NIST Tests of the Wireless Environment in 

Automobile Manufacturing Facilities

Kate A. Remley 

Galen Koepke 

Chriss Grosvenor 

Robert T. Johnk 

John Ladbury 

Dennis Camell 

Jason Coder 

NIST Technical Note 1550

NIST Technical Note 1550 

NIST Tests of the Wireless Environment in 

Automobile Manufacturing Facilities

Kate A. Remley 

Galen Koepke 

Chriss Grosvenor 

John Ladbury 

Dennis Camell 

Jason Coder 

Electromagnetics Division

Electromagnetics and Electrical Engineering Laboratory 

National Institute of Standards and Technology 

Boulder, CO 80305-3328 

Robert T. Johnk 

National Telecommunication and Information Agency 

Institute for Telecommunications Sciences 

Boulder, CO 80305-3328 

October 2008 

U.S. Department of Commerce 

Carlos M. Gutierrez, Secretary 

National Institute of Standards and Technology 

Patrick D. Gallagher, Deputy Director 
U.S. Government Printing Office 

Washington: 2008 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Internet bookstore: gpo.gov Phone: 202-512-1800 Fax: 202-512-2250 

Mail: Stop SSOP, Washington, DC 20402-0001 

Certain commercial entities, equipment, or materials may be identified in this 

document in order to adequately describe an experimental procedure or 

concept. Such identification does not imply recommendation or endorsement 

by the National Institute of Standards and Technology, nor does it imply that 

the entities, materials, or equipment are necessarily the best available for the 

purpose. 

National Institute of Standards and Technology Technical Note 1550 

Natl. Inst. Stand. Technol. Tech. Note 1550, 109 pages (October 2008) 

CODEN: NTNOEF 
iii 

Table of Contents 

Executive Summary 

0B1. Introduction ................................................................................................................. 2

1B2. Test Set-up .................................................................................................................. 3

2.1 The physical environment ...................................................................................... 3

14B2.2 The wireless propagation environment .................................................................. 6

2B3. Background Ambient Spectrum Analyzer Tests .......................................................... 7

15B3.1 Measurement set-up .............................................................................................. 7

16B3.2 Signal ranges over 24 hours ................................................................................ 14

17B3.3 Ambient signals in key frequency bands .............................................................. 18

3B4. Spectrum Analyzer Measurements of the 2.4 GHz Frequency Band ........................ 27

4B5. Ultra-Wideband Propagation Measurements ............................................................ 35

18B5.1 Measurement set-up ............................................................................................ 35

19B5.2 Frequency-domain measurements ...................................................................... 39

20B5.3 Time-domain data ................................................................................................ 41

21B5.4 Conclusion ........................................................................................................... 48

5B6. Summary ................................................................................................................... 48

6B7. References ................................................................................................................ 50

7BAppendix A: Assembly Plant, Low-Frequency Data, Omnidirectional Transmit and 

Receive Antennas ......................................................................................................... 51

Appendix B: Assembly Plant, High-Frequency Data, Directional Transmit, 

Omnidirectional Receive Antennas ............................................................................... 59

Appendix C: Assembly Plant, High-Frequency Data, Directional Transmit and Receive 

Antennas ....................................................................................................................... 67

8BAppendix D: Stamping Plant, Low-Frequency Data, Omnidirectional Transmit and 

Receive Antennas ......................................................................................................... 77

9BAppendix E: Metal Stamping Plant, High-Frequency Data, Directional Transmit, 

Omnidirectional Receive Antennas ............................................................................... 83

10BAppendix F: Metal Stamping Plant, High-Frequency Data, Directional Transmit and 

Receive Antennas ......................................................................................................... 89

1BAppendix G: Engine Plant, Low-Frequency Data, Omnidirectional Transmit and Receive 

Antennas ....................................................................................................................... 97

12BAppendix H: Engine Plant, High-Frequency Data, Directional Transmit Antenna, 

Omnidirectional Receive Antenna ............................................................................... 103

13BAppendix I: Engine Plant, High-Frequency Data, Directional Transmit and Receive 

Antennas ..................................................................................................................... 109

1 

NIST Tests of the Wireless Environment in Automobile Manufacturing 

Facilities 

Kate A. Remley, Galen Koepke, Chriss Grosvenor 

John Ladbury, Dennis Camell, Jason Coder 

Electromagnetics Division 

Electronics and Electrical Engineering Laboratory 

National Institute of Standards and Technology 

Boulder, CO 80305-3337 

Executive Summary 

 This report describes measurements carried out by members of the NIST 

Electromagnetics Division to study the wireless environment in automotive 

manufacturing facilities. Testing was performed at three facilities during 2006 and 2007. 

We studied an assembly plant, a very crowded environment having auto chassis bodies 

moving continuously along assembly lines; a metal stamping plant, consisting of large 

metal-working machinery housed in an older facility; and an engine plant, with a more 

modern open, assembly-line layout. 

We conducted three types of tests in each plant: (1) A background ambient 

spectrum survey where the existing wireless environment in each facility was monitored 

over a 24-hour period, indicating the current level of radio activity over time at one 

location on the factory floor. (2) A spectral analysis of the 802.11b WLAN frequency 

band, providing a detailed view of the existing use of this common frequency band. (3) 

Reverberant cavity tests where the physical spacing between a source and receiver 

was varied to investigate the signal-scattering characteristics of the production floor. 

These last tests provided an indication of the level of direct versus reflected path 

propagation in the environment. Together, the three sets of tests provided enough 

information to characterize the propagation environment for many wireless 

technologies. 

 Background ambient tests of the wireless environment showed signals in 

expected frequency bands, including broadcast radio and television transmissions, 

cellular telephone transmissions, and transmissions carried out within the facilities. In 

the stamping plant, the background ambient tests also showed signals covering a broad 

range of lower frequencies, probably due to machine noise. 

Our ultrawideband, synthetic-pulse measurements indicate that these 

manufacturing facilities are highly reflective, reverberant environments that can 

potentially complicate reliable performance of deployed wireless technology. Even 

under line-of-sight conditions, significant self-interference occurs when the transmitter 

and receiver are separated by only a few meters or more. When non-line-of-sight 

conditions occur, the transmission path becomes very noisy. However, spectrum 

analyzer tests conducted throughout the plant indicate that, for the current level of 

utilization of wireless technology, coverage can be maintained throughout the plants 
2 

when a sufficient number of transmitting and repeating nodes are used. However, if the 

use of wireless is to be expanded, interference may become a significant issue. 

The measured results provide key parameters that describe the wireless 

propagation environment in representative manufacturing facilities. While measurement 

uncertainties are not reported, end users of these data are interested primarily in largescale behavior on the order of tens of decibels. Including uncertainties on the order of 

±1 dB is of little value when we are studying quantities that can vary by tens of decibels. 

Improved channel descriptions will be useful for assessing current and future 

deployment of wireless technology in heavy-industrial manufacturing environments, for 

standards development, and for qualifying wireless equipment for use in highly reflective 

environments such as those studied here. Work is currently underway at NIST to 

develop laboratory-based methods for qualifying the performance of wireless equipment 

for use in highly reflective environments such as those studied here. 

0B1. Introduction 

Wireless technology in a production environment offers the potential benefits of 

lower installation costs, increased flexibility, and reduced maintenance when compared 

to cabled systems. However, the highly reflective, dynamic environment in an 

automobile production facility can impede signal reception for wireless devices such as 

local-area networks (LANs), equipment-diagnostic tools, plant-floor controllers, and 

RFID tags and readers. This may hinder the automotive industry and other U.S. 

industrial sectors from taking full advantage of the increased efficiency, reliability, and 

economy of wireless networking. A first step to improving the implementation of wireless 

networks and control at automotive manufacturing facilities is to evaluate the 

propagation environment by carrying out precise measurements at appropriate 

frequencies. 

 Members of the NIST Electromagnetics Division conducted detailed studies of 

the wireless environment in three automotive manufacturing facilities: an assembly 

plant, an engine plant, and a metal stamping plant. Tests were conducted on August 4-

6, 2006 and August 3-6, 2007. Three types of tests were carried out at each facility. 

First, we conducted a spectrum survey, where we monitored existing ambient signals in 

the environment over a 24-hour period. These “background ambient” measurements 

provide an indication of the current level of radio activity minute-by-minute at a 

representative location on the factory floor. The second set of tests measured the 

spectral activity at several locations throughout the facilities. These tests focused 

specifically on the 2.4 GHz industrial, scientific, and medical (ISM) unlicensed frequency 

band. Automotive plant wireless system engineers have expressed interest in additional 

utilization of systems in this band for telemetry and control on the production floor. 

 The third set of tests studied the scattering characteristics of the factory 

environment by use of a test source and receiver. The response of the environment to a 

pulse-like signal was measured, giving an indication of the level of direct versus 

reflected path propagation in the environment, as summarized in a metric called the 

RMS delay spread. This information can be useful in engineering additional wireless 

system deployments and determining the required level of immunity to interference for 
3 

new equipment. After an overview of the test set-up, the procedure and results for each 

test are discussed below. 

1B2. Test Set-up 

2.1 The physical environment 

The industrial environments represented by these manufacturing plants contain 

metallic structures and objects that can have a profound effect on radio reception. 

Transmitted radio signals reflect off objects before arriving at the radio receiver, and in 

so doing they can create interference. The size, shape, and materials of the factory 

environment will impact radio reception. An understanding of the physical environment 

can help to explain the measurement results and will enable development of appropriate 

lab-based tests to replicate these environments. 

 The first set of tests was carried out in an assembly plant whose dimensions are 

approximately 500 m x 250 m (1600 ft x 750 ft). The building is about 15 m (45 ft) high 

and constructed out of metal. The receiving site (“R” on Figure 2-1 below) for the 

background ambient tests, at Test Point “x”, was about 70 m (210 ft) from the left end of 

the building near columns “S7” and “S8”. The column indicators are noted on the left 

and upper side of the figure. For the scattering tests, a cart carrying the transmit 

antenna moved down aisle “S” approximately 300 m (1000 ft) from the receiving 

location. 

Path for scattering tests (R = receiver)

x

x Background ambient test site

2.4 GHz tests

o

o

o

W

U

S

L

Q

N

H

J

F

D

S,12 Column locator indicators

8 11 17 23 14 20

o

o o o o

R

o

27

o

o

o

~250 m

~500 m

Figure 2-1: Rough outline of assembly plant where NIST wireless testing was carried out. 

The plant contains numerous assembly lines, catwalks, and other metallic objects and 

structures. The location of NIST receiving equipment for the background ambient tests is 

marked by an x. The dashed line indicates the path taken during the reverberant cavity 

tests. The locations of the 2.4 GHz spectrum analyzer tests are marked with circles. 
4 

 The second set of tests was carried out in a metal stamping plant, referred to as 

the stamping plant in what follows. This facility contains large metal-working machinery, 

along with racks of parts, assembly lines, and offices. About half of the building dates to 

the 1940s, and the other half was added in the 1990s. The building is divided into large 

sections, as shown below in Figure 2. The dimensions of the building are approximately 

850 m x 760 m (2800 ft x 2500 ft). The building was about 15 m (45 ft) high. The newer 

portion is constructed of metal with a concrete floor and the older section is a mix of 

cinderblock, metal, and windows with floors of either concrete or wood. Our tests were 

conducted in different areas of the building: The receivers for our background ambient 

tests were set up at location “x” in Figure 2-2; a cart carrying the transmit antenna 

moved along the path denoted by a dashed line for the scattering tests; and the 

2.4 GHz spectrum analyzer tests were conducted throughout the facility at locations 

marked with circles. 

The third building was an engine assembly facility, referred to as the engine plant 

in what follows. This facility has a more open layout than the stamping plant or the 

assembly plant, with low-profile assembly-lines throughout the building. This is a very 

new facility, constructed in 2000. Its dimensions are approximately 215 m x 305 m 

(700 ft x 1000 ft). The ceilings were approximately 15 m high and made of metal. Again, 

we carried out each set of tests in various parts of the facility. The receivers for the 

background ambient tests were conducted at the location marked with an “x” on Figure 

2-3; the cart with the transmit antenna for the scattering tests moved along the path 

Path for scattering tests (R = receiver)

x

x Background ambient test site

2.4 GHz tests

o

o

o

D E F G H J K L

G,12 Column locator indicators

o

o

o

o

o

R

o

A BC

0

10

20

30

40

50

o

o

~750 m

~850 m

Figure 2-2: Rough layout of the stamping plant where NIST wireless testing was carried 

out. The plant contained assembly lines, heavy machinery, parts racks, and other metallic 

objects and structures. 
5 

marked with a pink dashed line; and the 2.4 GHz spectrum analyzer tests were 

conducted throughout the facility at locations marked with circles. 

 This facility is relatively open. Large machinery is located throughout the 

structure, but most machines were spaced several meters apart, connected by 

assembly lines. A number of metallic objects and surfaces are located throughout the 

facility including testing machinery, metal platforms, fences, beams, and conveyors, as 

well as mobile forklifts and maintenance vehicles. 

The stamping plant and the engine plant are much more open than the assembly 

plant we tested in 2006. Both have wide aisles and areas containing racks of parts. 

Because both plants had certain areas that were more crowded with machines, we 

carried out a number of the 2.4 GHz tests in these areas to study radio coverage and 

interference. 

 We would expect that large metal buildings like these with expansive metal 

surfaces and a very complex maze of reflective machinery would cause radio signals to 

scatter erratically or reverberate throughout the structure. These various signals travel 

in multiple complicated paths from transmitter to receiver. These multiple signal paths, 

known simply as ‘multipath’, typically involve different distances depending on how 

signals of a given frequency reflect off the metal surfaces. The concept of multipath is 

illustrated in Figure 2-4. When multiply reflected signals arrive at the receiver, they 

arrive at slightly different times. They may either add or subtract from the direct path 

signal, causing constructive or destructive interference, respectively. When the 

Path for scattering tests (R = receiver)

x

x Background ambient test site

2.4 GHz tests

o

o

Q o

P

N

M

L

K

J

H

G

F

E

D

H,12 Column locator indicators

6 8 10 16 12 14 18 20

o oo o

o

R

o

22

~215 m

~300 m

Figure 2-3: Layout of the engine plant where NIST wireless testing was carried out. The 

plant was more open than the assembly and stamping plants, although there were 

numerous assembly lines, parts racks, mobile fork trucks, and other metallic objects and 

structures. 
6 

interference becomes severe, radio communication may be lost. When the reflecting 

surfaces are in motion the received signal strength is even more variable. A good 

understanding of the relationship of these multipath signals to the direct (desired) signal 

is important in developing wireless systems that would work reliably in this environment. 

14B2.2 The wireless propagation environment 

As described above, the physical environment in all three facilities was quite 

reflective. This means that even weak radio signals from transmitters located a distance 

away could be received and could potentially interfere with desired radio signals. 

Knowledge of what radio technologies are deployed on the production floor can help 

interpret the measured results. 

 One primary use of radio technology in these facilities is for broadband data 

transfer by use of a wireless local-area network (WLAN). These plants use the IEEE 

802.11bTM or 802.11aTM standards [1-3]. The 802.11b standard consists of eleven 

channels operating on frequencies between 2.4 GHz and 2.472 GHz. These are 

considered “wideband” systems, since each channel spans about 20 MHz of spectrum 

to provide rapid data transfer. In comparison, a “narrowband” system may occupy only a 

few kilohertz to approximately a megahertz of spectrum. For all three plants studied, the 

WLAN transceivers (or nodes) were tuned to channels 1, 6, and 11. This is standard 

practice for minimizing interference between nodes. The nodes used in these facilities 

are mounted high overhead to provide the best line-of-sight radio connection between 

nodes. The 2.4 GHz “Industrial, Scientific, and Medical” (ISM) frequency band is 

unlicensed, which means other applications such as cordless phones, handheld 

Office

automobile

in production

TX

automobile

in production

Assembly 

line

RX

Direct Path

Reflections

Assembly line

Assembly line

Figure 2-4: Multiple reflections (multipath) occur when signals propagating between the 

transmitter and receiver reflect off metallic objects or structures. The different paths cause 

the signals to arrive at the receiver at slightly different times. 
7 

wireless games, as well as industrial control and telemetry equipment, can operate in 

this band. 

 Other wireless systems commonly used in industrial facilities include handheld 

radios for point-to-point communications. These radios are often used by maintenance 

and operational personnel for voice communications. These operate in the 900 MHz 

ISM frequency band. Cellular telephones used by staff operate at frequencies around 

850 MHz and 1.9 GHz. Cordless phones and other consumer electronics operating in 

the 5.2–5.9 GHz ISM unlicensed frequency band may also be used. At lower 

frequencies, radio interference from heavy equipment (“machine noise”) can impact 

signals. The tests below let us study these frequency bands to determine the level of 

interference between different systems in a particular band. 

2B3. Background Ambient Spectrum Analyzer Tests 

15B3.1 Measurement set-up 

Reception of desired wireless signals can be affected by users in a given 

frequency band as well as by out-of-band signals. Background ambient tests help to 

provide an understanding of the current wireless environment in a given facility, 

including potential in-band and out-of-band interference. This knowledge can be used to 

help mitigate existing interference issues, as well as to help ensure that future 

deployment will not face insurmountable interference. 

Figure 3-1 describes the measurement system used in our tests. A spectrum 

analyzer captured the ambient signals emitted by wireless devices, broadcast stations, 

and from unintentional emitters such as motors in machines. We were interested 

primarily in frequencies below 6 GHz, since these are the frequencies currently used for 

unlicensed voice and data wireless transmission. We recorded signals from a fixed 

location over 24-hour periods. For our first set of measurements in the assembly plant, 

we recorded signals over two 24-hour periods. We found little difference between data 

from one day to the next. Consequently, we recorded signals over one 24-hour period in 

the stamping and engine plants. 

In each plant, we used three spectrum analyzers: one for the lower frequencies 

(20 MHz to 1.3 GHz), one for mid-range frequencies (1 GHz to 6 GHz), and a third to 

monitor the higher frequencies (6 to 18 GHz). For the highest-frequency set-up, we 

were aware that the combined broad frequency band and low antenna sensitivity would 

result in a high noise floor. As a result, these measurements can identify only high-level 

signals in this band. 

In the assembly plant tests, we used omnidirectional antennas for all three 

frequency bands. In the stamping plant and the engine plant, we used omnidirectional 

antennas in the lowest and highest frequency bands and directional antennas for the 

middle band. In all cases, measurement data were collected continuously over the 

length of the test. This extended period for data collection tells us whether wireless 

traffic changes throughout the day; for example from production times to non-production 

times. The test site in each plant is indicated by the red “x” in Figures 2-1 through 2-3. 

Figure 3-2 shows a layout of the test equipment in the assembly plant, and Figures 3-2 
8 

and 3-3 show photographs of the measurement set-ups in the stamping and engine 

plants. 

antenna

g p

Signals from 

production floor

Spectrum analyzer

Figure 3-1: Background ambient tests use a spectrum analyzer to measure signals 

from all types of wireless devices, from broadcast stations, and from unintentional 

emitters such as large machines over a long period of time. 

automobile

in production

automobile

in production

Assembly 

line

Assembly line

Assembly line

NIST

RX

L

Receive 

antennas 

(on roof of 

office)

Spectrum 

analyzers

(inside 

office)

M H

Figure 3-2: Antenna and receiver locations for background ambient tests at the assembly 

plant. As shown in Figure 2-1, the office where the receivers were located was on aisle “S.” 
9 

Figure 3-3: Background ambient tests carried out at the stamping plant. (a) A midfrequency-range directional antenna located on a second-story-office roof is shown by the 

right-hand circle. A low-frequency, omnidirectional antenna was mounted between 

platforms, and is shown by the left-hand circle. (b) An omnidirectional antenna used for the 

high-frequency band was mounted on the platform to the left of the directional antenna in 

(a). (c) The second-story office where the three spectrum analyzers were located. 

(a) 

(c) 

(b) 
10 

 

The spectrum analyzers were programmed to acquire approximately 100 data 

sweeps every minute, and each sweep consisted of 8192 frequencies. Every 100 

sweeps, a computer program calculated the average and maximum at each frequency 

and saved these data files. Thus, we have a representation of the average and 

maximum every minute throughout one (approximately) 24-hour period. The recording 

(c) 

Figure 3-4: Background ambient tests carried out at the engine plant. The antennas and 

measurement system were located on a catwalk approximately 15 m above the plant floor. 

(a) A mid-frequency-range directional antenna. (b) A low-frequency, omnidirectional antenna 

was mounted on the catwalk hanging down over the production floor. (c) The three spectrum 

analyzers were located on the catwalk as well. 

(a) (b) 
11 

times are listed in Table 3-1 below. At the stamping plant, the different start and stop 

times occurred due to technical issues. The operational schedules for these facilities 

during these times are shown in Table 3-2. 

Stamping Plant (2007) 

Frequency 

band 

Start: 

Friday 

August 3 

Stop: 

Saturday 

August 4 

Low 1:25 p.m. 12:08 p.m. 

Mid 1:26 p.m. 12:09 p.m. 

High 10:36 a.m. 8:21 p.m. 

(August 3) 

Table 3-1: Start and stop times for the background ambient tests. 

Engine Plant (2007) 

Frequency 

band 

Start: 

Sunday 

August 5 

Stop: 

Monday 

August 6 

Low 1:45 p.m. 1:05 p.m. 

Mid 1:45 p.m. 2:34 p.m. 

High 1:47 p.m. 2:49 p.m. 

Assembly Plant Run #2 (2006) 

Frequency 

band 

Start: 

Friday 

August 4 

Stop: 

Saturday 

August 5 

Low 8:30 a.m. 7:15 a.m. 

Mid 8:30 a.m. 7:15 a.m. 

High 8:30 a.m. 7:15 a.m. 
12 

 The background ambient data presented below have been corrected for the 

antenna characteristics and represent the actual electric field strength (in dB relative to 

1 v/m) incident on the antenna. The antenna factors used are shown in Figure 3-5. The 

antenna factor represents the transfer function of the antenna from incident field 

strength to terminal voltage. We apply the antenna factor to the measured power 

recorded by the spectrum analyzer to determine the electric field strength picked up by 

the antenna. The antenna factors for these antennas were determined from direct 

measurements using the two-identical antenna method on the NIST open-area test site. 

 In practice, the antenna factor is valid for a particular aspect angle and will vary 

depending on the directional gain of the antenna. The antenna factors for the 

omnidirectional antennas are strictly valid only in the horizontal plane (zero-degree 

elevation angle) and, depending on the arrival angle of the radio wave, could be several 

decibels in error. Fortunately, the directional gain of these antennas is such that the 

zero-degree elevation angle antenna factor appears to be a reasonable average value 

over all the aspect angles. Notice in Figure 3-5 that the antenna factors are quite large 

at the higher frequencies, which makes it difficult to detect weak signals. The noise floor 

Table 3-2: Production schedules during the background ambient tests. 

Left side: assembly and engine plants. Right side: stamping plant. 

Assembly Plant 

Aug 3 – 5, 2006 

Day Shift 

Start: 6:00 a.m. 

Break: 9:30 - 9:45 a.m. 

Lunch: 11:00 - 11:30 p.m. 

Break: 1:00 - 1:15 p.m. 

Shift End: 2:30 p.m. 

Afternoon Shift 

Start: 3:30 p.m. 

Break: 5:30 - 5:45 p.m. 

Lunch: 9:00 - 9:30 p.m. 

Break: 10:45 - 11:00 p.m. 

Shift End: 12:00 a.m. 

Stamping Plant 

Aug 3, 2007 

1st shift 

Shift Start: 7:00 a.m. 

Break: 9:00 - 9:16 a.m. 

Lunch #1: 11:30 AM - 12:00 p.m. 

Lunch #2: 11:45 AM - 12:15 p.m. 

Cleanup: 2:55 - 3:00 p.m. 

Aug 3, 2007 

2nd shift 

Shift Start: 3:00 p.m. 

Break: 5:00 - 5:16 p.m. 

Lunch: 7:30 - 8:00 p.m. 

Cleanup: 10:55 - 11:00 p.m. 

Aug 3-4, 2007 

3rd shift 

Shift Start: 11:00 p.m. 

Break: 1:00 - 1:16 p.m. 

Lunch: 3:30 - 4:00 p.m. 

Cleanup 6:55 - 7:00 p.m. 

Aug 4, 2007 

1st shift 

Shift Start: 7:00 AM 

Break: 9:00 - 9:16 a.m. 

Lunch #1: 11:30 - 12:00 a.m. 

Lunch #2: 11:45 a.m.- 12:15 p.m. 

Cleanup: 2:55 - 3:00 p.m. 

Engine Plant 

Aug 5 – 7, 2007 

Shift Start: 6:00 a.m. 

Break: 9:00 - 9:15 a.m. 

Lunch: 11:00 - 11:45 a.m. 

Break: 1:30 - 1:52 p.m. 

Shift End: 4:30 p.m.
13 

of the spectrum analyzer is relatively constant with frequency; so the minimum signal 

we can measure is determined essentially by the antenna factor curve. 

 

Note that throughout this work, measurement uncertainties are not reported. End 

users of these data are primarily interested in large-scale statistical behavior on the 

order of tens of decibels. Including uncertainties on the order of 1 dB is of little value 

when we are studying quantities that can vary by tens of decibels. 

-30

-20

-10

0

10

20

30

40

50

60

70

0.01 0.10 1.00 10.00 100.00

Frequency (GHz)

Antenna Factor (dB)

Lowband Antenna Highband 

Antenna

Most Sensitive

Least Sensitive

Midband 

Antenna

(b) 

-30

-20

-10

0

10

20

30

40

50

60

70

0.01 0.10 1.00 10.00 100.00

Frequency (GHz)

Antenna Factor (dB)

Lowband Antenna

Highband Antenna

Most Sensitive

Least Sensitive

(a) 

Figure 3-5: Antenna factors for the receiving antennas used in the (a) assembly plant and 

(b) stamping and engine plants. In the assembly plant, we used the same antenna type for 

the mid- and high-band measurements.
14 

16B3.2 Signal ranges over 24 hours 

To summarize the large amount of data collected, we processed the recorded 

data. Each data file contained the average or maximum received signal at each 

frequency over a one-minute interval, and stored over the duration of the entire 

measurement (approximately 24 hours). Thus, at each frequency, we collected a set of 

over 1200 time samples. We then took the minimum and maximum of those time 

samples to obtain an overall minimum and maximum at each frequency. This leads to 

some admittedly confusing terminology when we refer to the maximum of the maxima, 

the maximum of the averages, or the minimum of the maxima. 

 Figures 3-6 and 3-7 show the extreme values of the (a) maximum and (b) 

average field measured over the entire spectrum from 20 MHz to 18 GHz for all three 

sites. As expected, no strong signals were detected above 6 GHz. However, the noise 

floor of the instruments increases significantly with frequency. 
15 

Figure 3-6: 24-hour signal amplitudes at the assembly plant. In (a), we computed the 

maximum of all recorded data collected during each minute, and then computed the 

minimum (dark blue curve) or maximum (light green curve) of each value over the 24-hour 

period. In (b), we computed the average of all recorded data collected during each minute, 

and then computed the minimum (dark blue) or maximum (green) of each value over the 24-

hour period. In each graph, the noise floor is plotted in red. 

(b) 

(a) 
16 

 

24 Hour Signal Characteristics

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

0.01 0.1 1 10 100

Frequency (GHz)

Signal Amplitude (dBV/m)

Min of Maximums

Max of Maximums

Figure 3-7: 24-hour signal amplitudes at the stamping plant. In (a), we computed the 

maximum of all recorded data collected during each minute, and then computed the 

minimum (dark blue curve) or maximum (light red curve) of each value over the 24-hour 

period. In (b), we computed the average of all recorded data collected during each minute, 

and then computed the minimum (dark blue) or maximum (red) of each value over the 24-

hour period. 

(a) 

(b) 

24 Hour Signal Characteristics

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

0.01 0.1 1 10 100

Frequency (GHz)

Signal Amplitude (dBV/m)

Min of Averages

Max of Averages
17 

24 Hour Signal Characteristics

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

0.01 0.1 1 10 100

Frequency (GHz)

Signal Amplitude (dBV/m)

Min of Max

Max of Max

(a) 

24 Hour Signal Characteristics

-120

-100

-80

-60

-40

-20

0

0.01 0.1 1 10 100

Frequency (GHz)

Signal Amplitude (dBV/m)

Min of Avg

Max of Avg

(b) 

Figure 3-8: 24-hour signal amplitudes at the engine plant. In (a), we computed the maximum 

of all recorded data collected during each minute, and then computed the minimum (dark 

blue curve) or maximum (light red curve) of each value over the 24-hour period. In (b), we 

computed the average of all recorded data collected during each minute, and then computed 

the minimum (dark blue) or maximum (red) of each value over the 24-hour period. 
18 

17B3.3 Ambient signals in key frequency bands 

The data collected for this evaluation of the wireless environment represent a 

comprehensive evaluation of the electromagnetic environment at a specific location 

within each plant. We briefly summarize some of our relevant findings for devices 

employed in production facilities such as these. We also discuss our methods for 

processing and presenting the results. 

We begin by examining two of the frequencies in and near the FM broadcast 

band. These two frequencies are representative of the typical signal characteristics 

throughout the measured spectrum. Figure 3-9 shows the measured field over time at 

106.7 MHz (an active FM radio channel) and at 109.0 MHz (slightly above the FM band 

with no apparent communication activity). The amplitude of the 106.7 MHz signal is 

roughly stable between −55 dBv/m and −40 dBv/m. The red curve represents the 

maximum observed signal over 100 samples, and the blue curve represents the 

average observed signal. The offset between these two curves is roughly constant at 

around 4 dB. 

Surprisingly, we see that the variation of the 106.7 MHz signal with time 

correlates well to the general operation of the plant, with lower levels observed while the 

assembly line was shut down. At 109.0 MHz, the readings are essentially at the noise 

floor of our instrumentation, with occasional spikes thrown in. Again the maximum 

observed signal is approximately 4 dB higher than the average, although the spikes 

show a much larger difference (as large as 20 dB). This indicates that the spikes are 

rare events, occurring only once or twice out of 100 samples. Since little information 

appears to be lost by examining the maximum observed signal, but using the average 

tends to diminish the effect of the spikes, we will focus on the maximum observed signal 

for the remainder of our analysis. 

 Presenting data similar to those shown in Figure 3-9 is not a tractable option for 

the more than 24,000 frequencies that we measured. Instead, we took a time series at 

several key measurement frequencies, similar to those shown in Figure 3-9, and 

computed five statistics: the minimum, the 25th percentile or lower quartile, the median, 

the 75th percentile or upper quartile, and the maximum. Together, these five statistics 

are referred to as a “five-number summary” of a set of data. Such a summary obviously 

loses information such as when a transition occurs or the duration of any transition, but 

does indicate how often an interfering signal might be present. For the 106.7 MHz and 

109.0 MHz signals, the minimum, lower quartile, median, and upper quartile are tightly 

grouped (approximately 5 dB variation) but the maximum is significantly higher 

(sometimes over 20 dB higher) than the upper quartile, indicating that high-amplitude 

signals are rare. Communication around a frequency that shows very little activity is 

possible as long as error correcting/detecting methods are used to recover from the 

occasional noise spike. 

 Figure 3-10 shows the five-number summaries for frequencies in the FM 

broadcast band. For each channel, the characteristics are similar to those of the 

106.7 MHz channel. Between channels, the characteristics are similar to those shown at 

109.0 MHz. 
19 

Figure 3-9: Maximum and average ambient signals at 106.7 MHz and 109 MHz from the 

assembly plant measured over a 24-hour period August 3-4, 2006. 

-100

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-50

-40

-30

-20

-10

0

Time 

Signal Amplitude (dBV/m)

106.7 MHz Max

106.7 MHz Ave

109 MHz Max

109 MHz Ave

106.7 MHz

109.0 MHz

9:00 PM 

to 

9:30 PM 12:50 PM 6:00 AM

11:00 AM 1:00 PM 3:00 PM 5:00 PM 7:00 PM 9:00 PM 11:00 PM 1:00 AM 3:00 AM 5:00 AM 7:00 AM 9:00 AM

8/4/2006 Maximum Quartiles Over a 24 Hour Period - Low-Band

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-50

-40

-30

-20

-10

0

10

90 92 94 96 98 100 102 104 106 108 110

Frequency (MHz)

Signal Amplitude (dBV/m)

max

0.75

median

0.25

min

Rare noise:

no signal

>75% of 

time 

Steady signal:

even minimum

is high.

FM Radio 

Figure 3-10: Ambient signals represented by a five-number summary in the FM broadcast 

band between 90 MHz and 110 MHz measured in the assembly plant and collected over a 

24-hour period, August 3-4, 2006. 
20 

 If several frequencies in a band have similar characteristics, we can overlay the 

traces to illustrate the commonalities. For example, Figures 3-11(a) through (c) show an 

overlap of all 43 frequencies measured between 20 MHz and 25 MHz at the three 

facilities. In 3-11(a), we see good correlation between the activity in the assembly plant 

and the level of electromagnetic emissions. The curves from the stamping and engine 

plants in 3-11(b) and (c) show three different characteristics: periods of low activity, 

periods of extended high activity, and short spikes of very high activity, possibly due to 

someone passing by the receiver site or a spike in the power or activity on the 

production floor. The broadband nature of the extended characteristics, along with the 

timing of the low-activity periods, indicates that the observed signals may be related to 

machinery that are energized during certain times of plant operation and either turned 

off or not operated during breaks. For example, the time window between 11 p.m. and 

5:30 a.m. in the stamping plant indicates that certain machinery may not be used during 

the third shift. 

We next examine some of the frequency bands of interest to wireless 

communication engineers. Figures 3-12(a), (c), and (e) show a three-dimensional 

representation of the signals around 5.8 GHz for the three facilities. We plot amplitude 

versus both frequency and relative time (number of minutes after the start of the 

measurement). Figures 3-12(b), (d), and (g) show the five-number summaries over the 

same frequency band for the three plants. 

In the assembly plant and the stamping plant, we see bursts of signal activity in 

this frequency band. Activity in the stamping plant occurs regularly, less so in the 

assembly plant. The signals cover a broad frequency range, but occur infrequently 

during the 24-hour period. Both types of graphs support this conclusion. For the engine 

plant, we see that the 5.8 GHz frequency band is not currently in use. 
21 

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-50

-40

-30

-20

-10

0

13:45 18:33 23:21 4:09 8:57 13:45

Time

Signal Amplitude (dBV/m)

Figure 3-11: An overlay of the 43 measured frequencies between 20 MHz and 25 MHz 

collected during a 24-hour period at (a) the assembly plant, August 3-4, 2006, (b) the 

stamping plant, August 3-4, 2007 and (c) the engine plant, August 5-6, 2007. 

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-40

-30

-20

-10

0

1:25 PM 3:49 PM 6:13 PM 8:37 PM 11:01 PM 1:25 AM 3:49 AM 6:13 AM 8:37 AM 11:01 AM 1:25 PM

Time

Signal Amplitude (dBV/m)

(a) 

(b) 

(c) 

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-40

-30

-20

-10

0

Time

Amplitude (dBV/m)

11:00 AM 1:00 PM 3:00 PM 5:00 PM 7:00 PM 9:00 PM 11:00 PM 1:00 AM 3:00 AM 5:00 AM 7:00 AM 9:00 AM Break Brea Break Break

k

BreakBreak

Shut Down
22 

 

Figure 3-12: Received signal levels at 5.8 GHz collected over a 24-hour period. Left 

column: Signal level versus frequency (right axis) and time (left axis) for the (a) assembly 

plant, (b) stamping plant, and (e) engine plant. Right column: A five-number summary of 

the same data for (b) assembly plant, (d) stamping plant, and (f) engine plant. 

Maximum Quartiles Over a 24 Hour Period

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-30

-20

-10

0

5.5 5.55 5.6 5.65 5.7 5.75 5.8 5.85 5.9 5.95 6

Frequency (GHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

(a) (b) 

Maximum Quartiles Over a 24 Hour Period

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-50

-40

-30

-20

-10

0

5.5 5.55 5.6 5.65 5.7 5.75 5.8 5.85 5.9 5.95 6

Frequency (GHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

(c) (d) 

(e) (f) 

8/4/2006 Maximum Quartiles Over a 24 Hour Period 

Mid-Band

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-50

-40

-30

-20

-10

0

10

5.5 5.55 5.6 5.65 5.7 5.75 5.8 5.85 5.9 5.95 6

Frequency (GHz)

Signal Amplitude (dBV/m)

max

0.75

med

0.25

min
23 

 The frequency band from 902 MHz to 928 MHz is often used for handheld 

wireless communication in industrial plants, while cell phone communications may be 

found in the 800 MHz frequency range. Figures 3-13(a)-(f) show radio activity in these 

bands. In the assembly plant, we see a great deal of activity in the 900 MHz band 

arising from plant floor communications. However, both the stamping plant and engine 

plant show little activity, with intermittent activity in the 800 MHz cellular band. 

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-80

-70

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-50

-40

-30

-20

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0

800 820 840 860 880 900 920 940 960 980 1000

Frequency (MHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

(a) (b) 

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-40

-30

-20

-10

0

800 820 840 860 880 900 920 940 960 980 1000

Frequency (MHz)

Signal Amplitude (dBV/m)

 Min

0.25

Median

0.75

Max

(e) (f) 

(c) (d) 

8/4/2006 Maximum Quartiles Over a 24 Hour Period - Low-Band

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-50

-40

-30

-20

-10

0

10

800 820 840 860 880 900 920 940 960 980 1000

Frequency (MHz)

Signal Amplitude (dBV/m)

max

0.75

median

0.25

min

Figure 3-13: Received signal levels at 900 MHz collected over a 24-hour period. Left 

column: Signal level versus frequency (right axis) and time (left axis) for the (a) assembly 

plant, (b) stamping plant, and (e) engine plant. Right column: A five-number summary of the 

same data for (b) assembly plant, (d) stamping plant, and (f) engine plant. 
24 

 The spectrum usage around 2.4 GHz is shown in Figure 3-14. In Figure 3-14(a) 

and (c), the 3-D representation shows high-level signals at certain frequencies. For the 

engine plant, Figure 3-13(e), we see consistent, low-level use of the 2.4 GHz band 

across the entire band (Figure 3-14(c)). The median in Figure 3-14(f) clearly shows one 

of the WLAN channels being used. The remainder of the usage is probably due to some 

other type of transmission system involving a frequency-hopping transmitter. 

-70

-60

-50

-40

-30

-20

-10

0

2.3 2.35 2.4 2.45 2.5 2.55 2.6

Frequency (GHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

(c) (d) 

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-50

-40

-30

-20

-10

0

2.3 2.35 2.4 2.45 2.5 2.55 2.6

Frequency (GHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

(a) (b) 

(e) (f) 

8/4/2006 Maximum Quartiles Over a 24 Hour Period 

Mid-Band

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-70

-60

-50

-40

-30

-20

-10

0

10

2.3 2.35 2.4 2.45 2.5 2.55 2.6

Frequency (GHz)

Signal Amplitude (dBV/m)

max

0.75

med

0.25

min

Figure 3-14: Received signal levels at 2.4 GHz collected over a 24-hour period. Left 

column: Signal level versus frequency (right axis) and time (left axis) for the (a) assembly 

plant, (b) stamping plant, and (e) engine plant. Right column: A five-number summary of the 

same data for (b) assembly plant, (d) stamping plant, and (f) engine plant. 
25 

Figure 3-15 shows low-frequency ambient signals from 10 MHz to 400 MHz. 

Below 400 MHz, the entire spectrum appears to be filled with noise, with a few obvious 

communication signals. For the stamping plant, there are several higher-level, 

intermittent signals at the lower frequencies. Much of this noise is probably related to 

the older, heavy machinery used in plant operations. 

(b)

(c) 

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-40

-30

-20

-10

0

0 50 100 150 200 250 300 350 400

Frequency (MHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

Figure 3-15: Low-frequency data (10–400 MHz) from (a) the assembly plant, (b) the 

stamping plant, and (b) the engine plant. Data were collected over a 24-hour period. 

8/4/2006 Maximum Quartiles Over a 24 Hour Period - Low-Band

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-80

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-60

-50

-40

-30

-20

-10

0

10

0 50 100 150 200 250 300 350 400

Frequency (MHz)

Signal Amplitude (dBV/m)

max

0.75

median

0.25

min

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

0 50 100 150 200 250 300 350 400

Frequency (MHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

(a) 
26 

 At 1.9 GHz, see Figure 3-16, (probable cell phone traffic) we see characteristics 

common to all plants. Below 1.95 GHz, the signals are less consistent, with high 

maxima, but low levels for the other statistics. These are likely transmissions from 

nearby individual cell phones. The lower-level signals are probably from a base station. 

Figure 3-16: Received signal levels at 1.9 GHz collected over a 24-hour period. Left column:

Signal level versus frequency (right axis) and time (left axis) for the (a) assembly plant (not 

available), (b) stamping plant, and (e) engine plant. Right column: A five-number summary of 

the same data for (b) assembly plant, (d) stamping plant, and (f) engine plant 

(a) (b) 

(c) (d) 

-70

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-50

-40

-30

-20

-10

0

1.8 1.82 1.84 1.86 1.88 1.9 1.92 1.94 1.96 1.98 2

Frequency (GHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

(e) (f) 

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-50

-40

-30

-20

-10

0

1.8 1.82 1.84 1.86 1.88 1.9 1.92 1.94 1.96 1.98 2

Frequency (GHz)

Signal Amplitude (dBV/m)

Min

0.25

Median

0.75

Max

8/4/2006 Maximum Quartiles Over a 24 Hour Period 

Mid-Band

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-20

-10

0

10

1.8 1.82 1.84 1.86 1.88 1.9 1.92 1.94 1.96 1.98 2

Frequency (GHz)

Signal Amplitude (dBV/m)

max

0.75

med

0.25

min

Figure not available 
27 

 The background ambient results presented here show wireless activity in 

expected frequency bands. The levels of activity seem very well defined. Broadcast 

stations can be received within the older stamping plant building, primarily because of 

the number of windows in this facility. Machine noise seems to be a significant issue in 

the stamping plant, but not the engine plant, at the locations studied. The 5.8 GHz band 

gets intermittent-to-little use. This may change as more wireless technology is deployed 

at these frequencies. We studied the 2.4 GHz band in more detail below. 

3B4. Spectrum Analyzer Measurements of the 2.4 GHz 

Frequency Band 

 Many types of wireless equipment utilize the 2.400 GHz – 2.484 GHz unlicensed 

frequency band, including WLAN systems used for data transfer, specialized equipment 

on the factory floor, and personal electronics, such as wireless handheld games or 

cordless phones. All of these different uses can lead to radio interference that can 

impair or even disable critical manufacturing equipment. Use of additional transceiver 

nodes to overcome interference or to fill in “dead spots” can actually create additional 

interference, especially in highly reflective environments, and must be positioned 

carefully. To provide additional insight into current use in this common frequency band 

on the production floor, we collected spectrum analyzer “snapshots” at locations 

throughout all three plants in the frequency range between 2.4 GHz and 2.5 GHz, as 

illustrated in Figure 4-1. 

 For these measurements, we used a portable spectrum analyzer connected to an 

omnidirectional antenna. Figure 4-2 shows the type of set-up used, although in practice 

we used a half-wave dipole antenna mounted on a metallic base for measurements 

above 1 GHz. The spectrum analyzer and antenna were carried throughout the plants 

and signals were recorded at the locations shown in Figures 2-1 through 2-3. 

Measurements were repeated at most locations on two different days. The goal of these 

tests was first to evaluate the coverage of existing transmissions throughout the plant, 

and second to determine whether there are any significant interfering sources in the 

present environment. 

Measurements were carried out with the “peak hold” feature of the spectrum 

analyzer turned on. This indicated the overall level of signal received at a particular 

location over the period for which the peak hold was engaged. Note that the signal 

levels presented in the measurement data give only relative values since we did not 

correct the measurements for the antenna used. 

Note that throughout this work, measurement uncertainties are not reported. End 

users of this data are primarily interested in large-scale statistical behavior on the order 

of tens of decibels, thus including uncertainties on the order of 1 dB is of little value. 
28 

We first show results from a series of measurements along aisle “S” in the 

assembly plant (see Figure 2-1). Using the handheld spectrum analyzer and a small 

rubber-coated helical monopole (rubber duck) antenna, we moved from column “S7” to 

column “S17”, about 170 m (500 ft.) away. Figure 4-3 shows the results of this set of 

measurements. While the 802.11b WLAN signals are very weak at S17, they can be 

detected almost continuously from S7 to that location. Midway, around S11, we see the 

transition from one node operating on channel 6 at 2.437 GHz to another node, 

operating on channel 11 at 2.462 GHz. Coverage is quite good down the aisle. 

node

antenna

Spectrum analyzer

frequency

Figure 4-2: Photograph of the portable spectrum analyzer and omnidirectional antenna used 

to collect snapshots of spectrum throughout the three plants. The antennas shown here were 

used at frequencies up to 1 GHz. Other omnidirectional antennas were used at higher 

frequencies. 

Figure 4-1: Measurement set-up for the handheld spectrum analyzer tests. 
29 

Figure 4-4 shows results of measurements at various locations in the stamping 

plant during production. Each graph was collected over a one-minute period on August 

3, 2007 using the “peak hold” function on the spectrum analyzer. We see that 802.11b 

signals are being transmitted on channels 1, 6, and 11 (center frequencies of 

2.412 GHz, 2.437 GHz, and 2.462 GHz). These signals were received at every location 

we tested, although in some cases the reception was quite weak, for example, channel 

1 in Figure 4-4(c). 

-100

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-90

-85

-80

-75

-70

-65

-60

-55

-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

5.0 dB 

M1

M2

M4

Spectrum Analyzer WPM9

Model: MS2711D Serial #: 00421041

Date: 08/05/2006 Time: 11:25:06

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 30 kHz VBW: 10 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -89.60 dBm @ 2400.0 MHz M2: -89.60 dBm @ 2400.0 MHz M4: -79.39 dBm @ 2465.0 MHz

S7

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-90

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-80

-75

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-65

-60

-55

-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

5.0 dB 

M1

M2

M4

Spectrum Analyzer WPM8

Model: MS2711D Serial #: 00421041

Date: 08/05/2006 Time: 11:19:42

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 30 kHz VBW: 10 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -90.22 dBm @ 2400.0 MHz M2: -90.22 dBm @ 2400.0 MHz M4: -90.97 dBm @ 2465.0 MHz

S9

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-90

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-65

-60

-55

-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

5.0 dB 

M1

M2

M4

Spectrum Analyzer WPM7

Model: MS2711D Serial #: 00421041

Date: 08/05/2006 Time: 11:18:27

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 30 kHz VBW: 10 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -89.20 dBm @ 2400.0 MHz M2: -89.20 dBm @ 2400.0 MHz M4: -90.86 dBm @ 2465.0 MHz

S11

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-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

5.0 dB 

M1

M2

M4

Spectrum Analyzer WPM6

Model: MS2711D Serial #: 00421041

Date: 08/05/2006 Time: 11:14:55

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 30 kHz VBW: 10 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -87.58 dBm @ 2400.0 MHz M2: -87.58 dBm @ 2400.0 MHz M4: -90.49 dBm @ 2465.0 MHz

S13

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-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

5.0 dB 

M1

M2

M4

Spectrum Analyzer WPM5

Model: MS2711D Serial #: 00421041

Date: 08/05/2006 Time: 11:12:46

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 30 kHz VBW: 10 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -89.24 dBm @ 2400.0 MHz M2: -89.24 dBm @ 2400.0 MHz M4: -89.74 dBm @ 2465.0 MHz

S15

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-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

5.0 dB 

M1

M2

M4

Spectrum Analyzer WPM4

Model: MS2711D Serial #: 00421041

Date: 08/05/2006 Time: 11:09:11

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 30 kHz VBW: 10 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -89.84 dBm @ 2400.0 MHz M2: -89.84 dBm @ 2400.0 MHz M4: -91.73 dBm @ 2465.0 MHz

S17

Figure 4-3: Handheld spectrum analyzer measurements made while moving approximately 

150 m (500 ft) down aisle S. Note that the center frequency of the 802.11b WLAN signal 

changes between S9 and S11, indicating reception from another node. 
30 

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-90

-80

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-60

-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer E23E4

Model: MS2711D Serial #: 00421041 Preamp: Dynamic

Date: 08/03/2007 Time: 08:29:19

Min Sweep Time: 1.00 Milli Sec

Std: 

RBW: 3 kHz VBW: 1 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: Dynamic dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -126.40 dBm @ 2437.0 MHz

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-110

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-90

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-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer K23B

Model: MS2711D Serial #: 00421041 Preamp ON

Date: 08/03/2007 Time: 09:23:33

Min Sweep Time: 1.00 Milli Sec

Std: 

RBW: 10 kHz VBW: 3 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 10 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -108.82 dBm @ 2400.0 MHz

Figure 4-4: Handheld spectrum analyzer measurements collected over a one-minute period 

in the 2.4 GHz frequency band in the stamping plant. Signals are clearly present in the three 

primary WLAN channels throughout the plant, although in some cases they are quite weak. 

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-90

-80

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-60

-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer K31A

Model: MS2711D Serial #: 00421041 Preamp ON

Date: 08/03/2007 Time: 09:00:08

Min Sweep Time: 1.00 Milli Sec

Std: 

RBW: 10 kHz VBW: 3 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 10 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -106.85 dBm @ 2400.0 MHz

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-50.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer L23

Model: MS2711D Serial #: 00421041 Preamp ON

Date: 08/03/2007 Time: 09:16:02

Min Sweep Time: 1.00 Milli Sec

Std: 

RBW: 10 kHz VBW: 3 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 1 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -119.17 dBm @ 2400.0 MHz

(a) (b) 

(c) (d) 

E23 K23 

K31 L23 
31 

 We carried out similar tests at the engine plant. We again turned on the “peak 

hold” function on the spectrum analyzer and carried out the measurement over an 

approximately three-minute window to see what signals were present over a longer 

period. Figure 4-5 shows results from representative locations on the production floor. 

These data were collected on Sunday, August 5, 2007. A second set of data collected 

at the same locations on Monday, August 6, 2007 is shown in Figure 4-6. 

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-20.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer K16-SUN-2P4-H

Model: MS2711D Serial #: 00421041

Date: 08/05/2007 Time: 12:57:09

Min Sweep Time: 1.00 Milli Sec

Std: 

MaxHold: ON

RBW: 30 kHz VBW: 1 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -95.66 dBm @ 2437.0 MHz

Figure 4-5: Handheld spectrum analyzer measurements collected over a three-minute 

period in the 2.4 GHz frequency band in the engine plant. As in the stamping plant, signals 

are present in the three primary WLAN channels throughout the plant. Other signals being 

transmitted in this frequency band are present in many locations as well. 

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-20.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer Q17-SUN-2P4-H

Model: MS2711D Serial #: 00421041

Date: 08/05/2007 Time: 12:52:17

Min Sweep Time: 1.00 Milli Sec

Std: 

MaxHold: ON

RBW: 30 kHz VBW: 1 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -94.84 dBm @ 2437.0 MHz

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-20.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer H11-SUN-2P4-H

Model: MS2711D Serial #: 00421041

Date: 08/05/2007 Time: 13:07:02

Min Sweep Time: 1.00 Milli Sec

Std: 

MaxHold: ON

RBW: 30 kHz VBW: 1 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -95.99 dBm @ 2437.0 MHz

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-20.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer H09-SUN-2P4-H

Model: MS2711D Serial #: 00421041

Date: 08/05/2007 Time: 13:11:08

Min Sweep Time: 1.00 Milli Sec

Std: 

MaxHold: ON

RBW: 30 kHz VBW: 1 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -95.81 dBm @ 2437.0 MHz

(c) (d) 

K16 Q17 

H11 H09 

(a) (b) 
32 

 We also carried out some longer-term studies in the assembly plant. Figure 4-7 

shows a typical snapshot of the WLAN traffic at a fixed receiving site during production. 

These data were collected over a 15-minute period during morning production on 

August 3, 2006. These measurements were carried out with a directional antenna 

aimed directly at one of the WLAN nodes. The 802.11b spectral mask has been drawn 

over the signals for channels 1, 6, and 11 (center frequencies of 2.412, 2.437, and 

2.462 GHz), showing the approximate level of each received signal. The spectral mask 

simply shows the maximum allowed occupied bandwidth for 802.11b WLAN signals. 

The lines show the allowed frequency span and the level to which signals need to be 

attenuated outside the channel to prevent interference with neighboring channels. 

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-70

-60

-50

-40

-30

-20

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-20.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer H09-MON-2P4

Model: MS2711D Serial #: 00421041

Date: 08/06/2007 Time: 06:44:19

Min Sweep Time: 1.00 Milli Sec

Std: 

MaxHold: ON

RBW: 10 kHz VBW: 1 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -100.51 dBm @ 2437.0 MHz

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-20.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer H11-MON-2P4

Model: MS2711D Serial #: 00421041

Date: 08/06/2007 Time: 06:39:44

Min Sweep Time: 1.00 Milli Sec

Std: 

MaxHold: ON

RBW: 10 kHz VBW: 1 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -92.57 dBm @ 2437.0 MHz

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-20.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer P17-MON-2P4-H

Model: MS2711D Serial #: 00421041

Date: 08/06/2007 Time: 05:09:06

Min Sweep Time: 1.00 Milli Sec

Std: 

MaxHold: ON

RBW: 10 kHz VBW: 3 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -100.51 dBm @ 2437.0 MHz

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-20.0 dBm 

 dB / Div : 

10.0 dB 

M1

Spectrum Analyzer K16-MON-2P4

Model: MS2711D Serial #: 00421041

Date: 08/06/2007 Time: 06:22:30

Min Sweep Time: 1.00 Milli Sec

Std: 

MaxHold: ON

RBW: 10 kHz VBW: 1 kHz Detection: RMS Average

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -91.09 dBm @ 2437.0 MHz

(a) (b) 

(c) (d) 

H11 H09 

K16 P17 

Figure 4-6: A second set of handheld spectrum analyzer measurements collected over a 

three-minute period in the 2.4 GHz frequency band in the engine plant. Again, signals are 

clearly present in the three primary WLAN channels, as well as at other frequencies in the 

band throughout the plant. The increased resolution in this set of graphs (10 kHz as opposed 

to 30 kHz in Figure 4-5) provides a reduced noise floor for the measurement, but also 

reduces the signal level in each measured frequency component, making the transient 

signals appear as lower-level signals compared to those in Figure 4-5, when they are 

probably comparable in actuality. 
33 

The high-level, spike-like signals seen in the channels adjacent to the center 

channel may be caused by other narrowband, frequency-hopping equipment in the 

vicinity such as a wireless scanning system used nearby. Also, the 802.11b protocol 

uses “probe” signals that allow nodes on different channels to communicate with each 

other. When examined over a long period, the probe signals show up as a set of 

narrowband spikes in adjacent channels. These spikes have approximately the same 

signal level as the main channel. Figure 4-8 shows three repeat measurements of a 

typical 802.11b card made in isolation in a NIST anechoic chamber over a one-hour 

period. The inset shows a single measurement, while the larger graph is the culmination 

of several measurements. The probe signals emanating from the card are clearly 

visible. 

Finally, a comparison of received signal strength during production and during a 

break (Figure 4-9) at the assembly plant shows only slight changes in the level of 

activity in the 2.4 GHz band. 

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-30.0 dBm 

 dB / Div : 

10.0 dB 

M1

M23

Spectrum Analyzer M3

Model: MS2711D Serial #: 00421041 Preamp ON

Date: 08/03/2006 Time: 06:41:08

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 3 kHz VBW: 1 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 10 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -109.47 dBm @ 2400.0 MHzM2: -109.47 dBm @ 2400.0 MHzM3: -109.47 dBm @ 2400.0 MHz

15 minute 

peak hold on

Figure 4-7: Handheld spectrum analyzer measurements collected over a 15 minute period in 

the 2.4 GHz frequency band. The spectral mask for the three 802.11b WLAN channels used in 

the facility are indicated on the graph, with the approximate level superimposed over the 

signals. 
34 

The detailed measurements of the spectrum in the 2.4 GHz frequency band 

discussed here show that there is a significant level of activity in this band in all of the 

plants. The use of an unlicensed portion of the spectrum for critical operations can be 

problematic, since the activity level can be highly variable and so interference issues 

can arise intermittently. Personal electronics as well as other systems that operate in 

this band can interfere with operations. However, there are few licensed frequency 

bands available for broadband data transfer in industrial environments. Frequency and 

channel coordination, as is done at these facilities, are two good options to minimize 

interference issues. A third would be to occasionally monitor activity, such as we have 

done here. When the spectrum gets crowded or if interference issues arise, these types 

of tests can be very beneficial in identifying and eliminating sources of interference. 

-100

-95

-90

-85

-80

-75

-70

-65

-60

-55

-50

2320 2340 2360 2380 2400 2420 2440 2460 2480 2500 2520

Ref Level : 

-50.0 dBm 

 dB / Div : 

5.0 dB 

P87-5M-6 

P87-5M-5 

M1

P87: 5 min Intervals After 1 Hour P87-5M-6

Model: MS2711D Serial #: 00421041

Date: 04/04/2005 Time: 14:48:13

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 100 kHz VBW: 30 kHz Detection: Pos. Peak

CF: 2420.0 MHz SPAN: 200.00 MHz Attenuation: 0 dB dBm

Frequency (2320.0 - 2520.0 MHz)

M1: -57.06 dBm @ 2420.0 MHz

M1

-100

-95

-90

-85

-80

-75

-70

-65

-60

-55

-50

2320 2340 2360 2380 2400 2420 2440 2460 2480 2500 2520

Ref Level : 

-50.0 dBm 

 dB / Div : 

5.0 dB 

P87-5M-6 

P87-5M-5 

M1

P87: 5 min Intervals After 1 Hour P87-5M-6

Model: MS2711D Serial #: 00421041

Date: 04/04/2005 Time: 14:48:13

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 100 kHz VBW: 30 kHz Detection: Pos. Peak

CF: 2420.0 MHz SPAN: 200.00 MHz Attenuation: 0 dB dBm

Frequency (2320.0 - 2520.0 MHz)

M1: -57.06 dBm @ 2420.0 MHz

M1

Figure 4-8: Handheld spectrum analyzer measurements of a representative 802.11b WLAN 

card made in isolation over a one-hour period. Note the large, spike-like signals outside the 

main channel which occur when the WLAN card monitors the environment for other cards in 

the area. 

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-40.0 dBm 

 dB / Div : 

10.0 dB 

M2M1

M3

Spectrum Analyzer M12

Model: MS2711D Serial #: 00421041 Preamp ON

Date: 08/03/2006 Time: 08:59:03

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 10 kHz VBW: 3 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -74.72 dBm @ 2434.5 MHz M2: -74.72 dBm @ 2434.5 MHz M3: -74.72 dBm @ 2434.5 MHz

15 minute 

peak hold on

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

2400 2410 2420 2430 2440 2450 2460 2470 2480 2490 2500

Ref Level : 

-40.0 dBm 

 dB / Div : 

10.0 dB 

M2M1

M3

Spectrum Analyzer M10

Model: MS2711D Serial #: 00421041 Preamp ON

Date: 08/03/2006 Time: 08:28:44

Min Sweep Time: 50.00 Micro Sec

MaxHold: ON

RBW: 10 kHz VBW: 3 kHz Detection: Pos. Peak

CF: 2450.0 MHz SPAN: 100.00 MHz Attenuation: 0 dB dBm

Frequency (2400.0 - 2500.0 MHz)

M1: -78.24 dBm @ 2434.5 MHz M2: -78.24 dBm @ 2434.5 MHz M3: -78.24 dBm @ 2434.5 MHz

15 minute 

peak hold on

Figure 4-9: The left-hand graph shows activity in the 2.4 GHz band during production at the 

assembly plant, while the right-hand graph shows activity during a break. 
35 

4B5. Ultra-Wideband Propagation Measurements 

18B5.1 Measurement set-up 

In order to characterize the radio-wave scattering in these facilities, we deployed 

a NIST-developed propagation measurement system. The system acquires both 

magnitude and phase of signals covering a broad range of frequencies. The phases of 

the sent and received signals are synchronized, enabling transformation of the recorded 

signal into the time domain. Signals that cover a wide frequency band transform to 

short-duration pulses in the time domain. Thus, this system can be used to study the 

effects of multiple reflections (‘multipath’) in an environment by measuring the time 

taken for reflections of the initial pulse to decay below a certain threshold value. 

The measurement system consists of a precision vector network analyzer (VNA), 

a transmitting antenna, a receiving antenna, an 18 GHz analog optical link, and 50 

microwave cables to connect the antennas with the VNA, as shown in Figure 5-1. A 

laptop computer is connected to the VNA in order to control the measurement process 

and to acquire and store measured data. The VNA has a transmitter and receiver within 

the same instrument and performs measurements between the two antennas. We 

acquired both the magnitude and phase of the S-parameter S21, which describes the 

characteristics of the transmission path. Data may be acquired at stepped frequencies 

over the range of 300 kHz to 18 GHz. For this series of tests, transmission data were 

acquired at approximately 80,000 frequencies. For frequencies up to 1 GHz, 

omnidirectional antennas were used. For frequencies from 1 GHz to 18 GHz, we used 

directional dual-ridge waveguide antennas, similar to horn antennas. The transmitting 

antenna was held fixed and the receiving antenna moved along aisles in the factory on 

a rolling cart, as shown in Figures 5-2 through 5-8. 

Ground Plane

Transmitting

antenna

tripods

62 inches

VNA

Port 1 Port 4

200 m

Optical

Fiber

Receiving

antenna

Fiber Optic

Receiver

RF Optical

Fiber Optic

Transmitter

RF Optical

Figure 5-1: Ultrawideband, synthetic-pulse measurement system based on a vector network 

analyzer. Frequency-domain measurements, synchronized by the optical fiber link, are 

transformed to the time domain in post-processing. This enables determination of wideband 

path loss, time-delay spread and other figures of merit important in characterizing broadband 

modulated signal transmission. 
36 

automobile

in production

automobile

in production

Assembly 

line

Assembly line

Assembly line

RX TX

Fiber-optic cable

Transmitter stays 

fixed while 

receiver moves 

down aisle

Receive 

antenna

Transmit 

antenna

Figure 5-2: Layout of UWB tests in the assembly plant. The VNA (labeled “TX” for 

transmitter) remains in a fixed location. The signal received by the receive antenna (labeled 

“RX” for receiver) is amplified and returned to the VNA via a fiber-optic cable that maintains 

the phase relationships between measured frequency components. The receiver moves 

away from the transmitter along a straight line in discrete steps. 

3

6

9

12

0 m

3 m

10 m

20 m

40 m

50 m

75 m

80 m

110A m 100 m 90 m

110B m

3

6

9

12

3

6

9

12

3

6

9

12

TX 

antenna

RX 

antenna

VNA

Optical

Fiber Link

Figure 5-3: Layout of the NIST ultrawideband tests in the stamping plant. The receive 

antenna (RX) was placed on a rolling cart and moved along aisles H and G, as indicated on 

the layout given in Figure 2-1. Measurements were taken at the distances indicated above. 

The transmit antenna (TX) remain fixed. When directional antennas were used, at 0 m, 

50 m, 75 m, and 110 m, the RX antenna was rotated in the directions indicated above. 
37 

Figure 5-5: Photograph looking the other way in the same corridor of the stamping plant. 

The high-frequency directional antennas are shown. The photograph shows the VNA and the 

optical fiber linking the transmitting and receiving antennas. 

Figure 5-4: Photograph of the long corridor in the stamping plant where the UWB scattering 

measurements were made. The low-frequency omnidirectional antennas are shown. The 

VNA is located near the NIST staff at the left side of the photo. 
38 

3

6

9

12

0 m

3 m

10 m

20 m

40 m

50 m

60 m

80 m

120A m 100 m

120B m

3

6

9

12

3

6

9

12

TX 

antenna

RX 

antenna

VNA

Optical

Fiber Link

6 m

Figure 5-6: Layout of the NIST ultrawideband scattering tests used in the engine plant. The 

receive antenna (RX) was placed on a rolling cart and moved along aisles Q and P as 

indicated on the layout given in Figure 2-2. Measurements were taken at the distances 

indicated above. The transmit antenna (TX) remain fixed. When directional antennas were 

used, at 0 m, 50 m, and 120 m, the RX antenna was rotated in the directions indicated 

above. 

Figure 5-7: Corridor in the engine plant where UWB scattering measurements were made. 

The receive antenna moved along the corridor on the rolling cart. The VNA and the 

transmitting antenna were located behind the photographer.
39 

Note that throughout this work, measurement uncertainties are not reported. End 

users of this data are primarily interested in large-scale statistical behavior on the order 

of tens of decibels, thus including uncertainties on the order of 1 dB is of little value. 

19B5.2 Frequency-domain measurements 

We first looked at measurements of received signal levels in the frequency 

domain. Figures 5-9 and 5-10 show measured excess path loss for the stamping plant 

and engine plant, respectively, where the data have been normalized to the magnitude 

of the direct-path received signal. The term “excess” means the direct-path signal has 

been subtracted, so we are looking only at scattered signals. In cases where there is no 

direct-path signal, we estimate its value by measuring free-space path loss for closely 

spaced antennas at a known distance. Knowing the free-space path loss for a given set 

of antennas and cables, we can then predict its value at other distances, since the freespace path loss has a 1/r dependence, where r is the distance in meters. 

Figures 5-9 and 5-10 show results for frequencies from 1 GHz to 18 GHz at four 

locations in the stamping plant and engine plant, respectively. All frequency 

components were transmitted at the same amplitude level, but the received signals 

show a range of amplitude values. The variations in received signal level across the 

measured frequency span indicate that signals reflected (scattered) off metallic surfaces 

and walls in the plants are interfering with the received signal. This is very pronounced 

at the 50 m distances, where interference off of a major reflecting surface (a corridor in 

the stamping plant and a wall in the engine plant) occurs at the 50 m mark. Once the 

receiving antennas turn the corner and are no longer within line of sight of the 

transmitting antennas, the signal levels drop and become much more noisy. This is 

because the large number of reflected paths taken by the signals between transmitter 

and receiver behave statistically like noise when there is no direct signal component. 

We saw similar results for the low-frequency omnidirectional antennas. The complete 

set of excess-path-loss data are given in the appendices at the end of the report. 

Figure 5-8: VNA set-up in the engine plant. The directional transmit antenna is shown in the 

foreground. The corridor shown in Figure 5-7 continues to the left side of this picture. 
40 

0 4000 8000 12000 16000 20000

Frequency (MHz)

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-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

50 m separation

System Noise (40 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

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-110

-100

-90

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-70

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-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

10 m separation

System Noise (20 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

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-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

80 m separation

System Noise (80 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

110 m separation (B)

System Noise (80 m)

Figure 5-9: UWB measurements made at the stamping plant using directional antennas 

facing each other at distances of (a) 10 m, (b) 50 m, (c) 80 m, and (d) 110 m. The deep nulls 

in (b) indicate significant scattering. The low-level, noise-like signals in (c) and (d) mean that 

interference and loss are creating a very noisy environment. 

(c) (d) 

(a) (b) 
41 

20B5.3 Time-domain data 

As mentioned above, the ability to acquire both magnitude and phase data over a 

large number of frequencies makes it possible to perform post-processing where we 

mathematically transform the stepped-frequency data into high-resolution, time-domain 

waveforms. These, in turn, can be gated and filtered to isolate selected scattering 

events. They can also be used to find wireless system figures of merit such as the 

power delay profile of an environment, the K-factor, and RMS delay spread. 

Post-processed time-domain waveforms that illustrate the multiple reflections 

scattered by equipment and structures are shown in Figure 5-11. The initial waveform 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

50m Separation

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

10m Separation

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

80m Separation

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

120m-A Separation

System Noise, 50m

Figure 5-10: UWB measurements made at the engine plant using directional antennas 

facing each other at distances of (a) 10 m, (b) 50 m, (c) 80 m, and (d) 120 m. The deep nulls 

in (b) and (c) indicate significant scattering. The low-level, noise-like signals in (d) mean that 

interference and loss are creating a very noisy environment. 

(c) (d) 

(a) (b) 
42 

event is the direct coupling between the transmit and receive antennas. The waveform 

activity that follows corresponds to scattering from objects inside the plants. The 

waveforms generally have exponentially decaying envelopes that are caused by lossy 

materials inside the plants (e.g., manufactured products, machinery, concrete, etc.). 

The fact that the plants exhibit such significant scattering behavior can pose a 

challenge for indoor wireless communications. One metric that is used to quantify this 

effect is the RMS delay spread, which is the period required for the reflected signals to 

die down below a certain threshold level. RMS delay for the synthetic pulse 

measurements is defined in [3]. A long RMS delay spread means that scattering is 

significant. When the RMS delay spread exceeds the error correction of the digital 

modulation used in most wireless transmissions, errors in transmitted bits may occur. 

0 300 600 900 1200 1500 1800

Frequency (MHz)

-200

-160

-120

-80

-40

0

S21 Normalized Magnitude (dB)

Stamping Plant

LowFreqDiscones

(6 m separation)

Direct Component included

No Direct Component (gate = 65 ns)

(a) (b) 

100 200 300 400 500 600 700 800 900 1000

Time (ns)

-160

-120

-80

-40

0

Received Signal Power (dB)

)

100 200 300 400 500 600 700 800 900 1000

Time (ns)

-160

-120

-80

-40

0

Received Signal Power (dB)

)

0 300 600 900 1200 1500 1800

Time (nS)

-140

-120

-100

-80

-60

-40

-20

0

S21 Magnitude (dB)

Engine Plant

Low Freq Discones (6m sep)

Direct Component Included

No Direct Component (gate=74nS)

(c) 

Figure 5-11: Time-domain response for antenna-to-antenna separations of (a) 50 m in the 

assembly plant; (b) 6 m in the stamping plant; (c) 6 m in the engine plant. Note the large 

reflection from a truck loading door in the assembly plant measurement. 
43 

Post-processing of the measured VNA data readily yields the RMS delay spread. 

Tables 5-1 and 5-2 give the RMS delay spread values that we measured in the 

stamping plant and the engine plant, respectively, for both high-frequency and lowfrequency antennas. 

If we further post-process the results, we can find the resulting reverberant cavity 

quality factor Q. Cavity Q is one metric that is indicative of complex cavity behavior: the 

higher the Q, the more reverberant the cavity and the longer the decay time. Q is 

defined as 

Q2 f , (5-1) 

where  is the received-power decay time, and f is the center frequency of interest. The 

rate of decay is defined as the time it takes for the signal to decay to 37 % of its initial 

value. 

Table 5-1: 

Stamping plant 

Low-frequency, omnidirectional 

Table 5-2: 

Stamping plant 

High-frequency, directional antennas

* The positions with an asterisk indicate calculations where the direct component has been 

removed and the RMS delay spread calculated to a stop time of 900 ns, where the signal 

levels are approximately 20 – 40 dB above the noise floor of the instrument. 

Position 

(m) 

RMS Delay 

Spread (ns) 

Mean 

Delay (ns)

6* 62 19 

10* 90 49 

20* 75 30 

40* 64 22 

50* 75 33 

60* 78 36 

75* 79 37 

80 106 97 

90 97 88 

100 104 117 

110A 116 153 

110B 131 158 

110B 

elevated 128 165 

Position 

(m) 

RMS Delay 

Spread (ns) 

Mean Delay 

(ns) 

6* 61 34 

10* 76 50 

20* 103 73 

40* 117 72 

50* 173 118 

60* 142 117 

75* 139 101 

80 128 107 

90 130 136 

100 146 173 

110A 153 220 

110B 153 218 
44 

Figure 5-12 depicts the decay characteristics in the assembly plant for 

frequencies in the vicinity of 950 MHz, 2.45 GHz, and 5.2 GHz. The decay times vary 

from 127 ns to 170 ns, with Q values covering a range of 1015 to 4149. This high-Q, 

reverberant behavior results primarily from the all-metal enclosure of the building and 

exhibits characteristics similar to some laboratory-based reverberation chambers. 

A reverberant environment, such as this, produces much scattering in addition to 

the direct path between a transmitter and receiver and inhibits the ability to 

communicate. One metric used to quantify this effect is the K-factor, which is the ratio of 

the energy in the direct-path coupling between the transmit and receive antennas to the 

energy that results from environmental reflections. A high K-factor means that the 

antenna-to-antenna coupling dominates, and a low K-factor implies a strongly 

reverberant (high multipath) environment. 

Table 5-3: 

Engine plant 

Low-frequency, omnidirectional 

Table 5-4: 

Engine plant 

High-frequency, directional antennas

* The positions with an asterisk indicate calculations where the direct component has been 

removed and the RMS delay spread calculated to a stop time of 900 ns, where the signal 

levels are approximately 20 – 40 dB above the noise floor of the instrument. 

Position 

(m) 

RMS Delay 

Spread (ns) 

Mean 

Delay (ns)

10* 66 36 

20* 61 38 

40* 107 77 

50* 105 75 

60* 116 93 

80* 112 82 

100 129 185 

120A 133 208 

120B 142 145 

Position

(m) 

RMS Delay 

Spread (ns) 

Mean 

Delay (ns)

6* 16 2 

10* 29 4 

20* 40 9 

40* 51 11 

50* 53 11 

60* 57 13 

80* 58 13 

100 115 141 

120A 114 155 

120B 120 157 
45 

We post-processed the VNA data to find the K-factor of the assembly plant. 

Figure 5-13 (a) and (b) depict K-factors measured in the assembly plant as function of 

antenna separation from 2 m – 300 m. We used both directional (Figure 5-13(a)) and 

omnidirectional (Figure 5-13(b)) transmit antennas. The curves are smoothed out by 

use of frequency averaging over a bandwidth of 200 MHz. Results are plotted in 

decibels for the 950 MHz, 2.45 GHz, and 5.2 GHz wireless bands. 

For the case of the directional transmit antenna (Figure 5-13(a)), the K-factor 

increases significantly for antenna separations less than 20 m. A more rapid increase is 

noted at the higher frequencies due to the higher gain of the transmit antenna and 

improved directionality. As the antenna separation is increased beyond 20 m, the Kfactor generally stays in the vicinity of unity (0 dB). We note a peak in the 5.2 GHz data 

at 150 m, which might be due to a combination of antenna pattern effects and a strongly 

reflecting path between transmitter and receiver. A similar effect is seen for the 

950 MHz data. 

0 40 80 120 160 200

Time (ns)

-65

-60

-55

-50

-45

-40

-35

Signal Power (dB)

950 MHz

ns

Q = 1,015

2450 MHz

ns

Q = 2,463

5200 MHz

ns

Q = 4,149

0 40 80 120 160 200

Time (ns)

-65

-60

-55

-50

-45

-40

-35

Signal Power (dB)

950 MHz

ns

Q = 1,015

2450 MHz

ns

Q = 2,463

5200 MHz

ns

Q = 4,149

Figure 5-12: Time-domain response for a 50 m antenna separation in the assembly plant 

using an omnidirectional transmit antenna. Decay characteristics are shown at selected 

wireless frequencies using a 200 MHz averaging bandwidth. 
46 

The situation changes when the transmit antenna is omnidirectional, as shown in 

Figure 5-13(b). The K-factor now drops to unity or less (< 0 dB) as distance is increased 

beyond 5 m. At a distance of 100 m or more, some peaks in the K-factor occur. This is 

probably due to a combination of the effects of the antenna pattern and the occurrence 

of strong environmental scattering. Lower values of K-factor indicate that the 

reverberant behavior of the assembly plant is much stronger if we illuminate it with an 

omnidirectional antenna. We also see that the use of a directional antenna reduces the 

effects of scattering and multipath for transmitter/receiver separations of 20 m or less. 

For larger separations, however, the advantages of using a directional antenna diminish 

rapidly. 

Figures 5-14 (a) through (d) depict the K-factor as a function of frequency for 

both the directional and non-directional antenna types. Each curve corresponds to a 

different transmit/receive antenna separation. Results are plotted over a frequency 

range from 1 GHz to 10 GHz using an averaging bandwidth of 200 MHz. 

1 10 100 1000

Distance (m)

-10

0

10

20

30

Discone k-Factor (dB)

k-Factor Discone

Antennas

950 MHz

2450 MHz

5200 MHz

1 10 100 1000

Distance (m)

-10

0

10

20

30

DRH k-Factor (dB)

k-Factor DRH

Antennas

950 MHz

2450 MHz

5200 MHz

1 10 100 1000

Distance (m)

-10

0

10

20

30

Discone k-Factor (dB)

k-Factor Discone

Antennas

950 MHz

2450 MHz

5200 MHz

1 10 100 1000

Distance (m)

-10

0

10

20

30

DRH k-Factor (dB)

k-Factor DRH

Antennas

950 MHz

2450 MHz

5200 MHz

(a) (b) 

Figure 5-13: K-factor over a 200 MHz bandwidth as a function of distance in the assembly 

plant for three different center frequencies. Black: 950 MHz, Red: 2.45 GHz, Green: 5.2 GHz. 

(a) Directional antennas. (b) Omnidirectional antennas. 
47 

In Figures 5-14(a) and 5-14(c), we see rapid variations in received-signal level as 

a function of frequency for the directional antennas. These variations are caused by the 

more complex pattern characteristics of the directional antennas. Peak-to-peak 

variations are typically in the range of 15 dB to 20 dB. The corresponding results for an 

omnidirectional transmit antenna, shown in Figures 5-14(b) and 5-14(d), exhibit 

smoother variations with frequency, due to the simple pattern characteristics. Peak-topeak variations in the K-factor of 5 dB to10 dB are typically seen as a function of 

frequency. The effects of using different types of antennas on received signal levels can 

be seen in more detail in the appendices, where the complete set of excess-path-loss 

data is given. 

2000 4000 6000 8000 10000

Frequency (MHz)

-20

-10

0

10

20

30

40

DRH k-Factor (dB)

5m-100m

5m

10m

20m

50m

100m

2000 4000 6000 8000 10000

Frequency (MHz)

-20

-10

0

10

20

30

40

DRH k-Factor (dB)

5m-100m

150m

200m

250m

300m

1000 2000 3000 4000 5000 6000

Frequency (MHz)

-20

-10

0

10

20

30

40

Discone k-Factor (dB)

2m-50m

2m

5m

10m

20m

50m

1000 2000 3000 4000 5000 6000

Frequency (MHz)

-20

-10

0

10

20

30

40

Discone k-Factor (dB)

100m-300m

100m

150m

200m

250m

300m

a)

b)

c)

d)

2000 4000 6000 8000 10000

Frequency (MHz)

-20

-10

0

10

20

30

40

DRH k-Factor (dB)

5m-100m

5m

10m

20m

50m

100m

2000 4000 6000 8000 10000

Frequency (MHz)

-20

-10

0

10

20

30

40

DRH k-Factor (dB)

5m-100m

150m

200m

250m

300m

1000 2000 3000 4000 5000 6000

Frequency (MHz)

-20

-10

0

10

20

30

40

Discone k-Factor (dB)

2m-50m

2m

5m

10m

20m

50m

1000 2000 3000 4000 5000 6000

Frequency (MHz)

-20

-10

0

10

20

30

40

Discone k-Factor (dB)

100m-300m

100m

150m

200m

250m

300m

a)

b)

c)

d) (c) (d) 

Figure 5-14: K-factor as a function of frequency for various antenna spacings in the 

assembly plant. (a) Directional antennas (5 m to100 m). (b) Omnidirectional antennas (2 m to 

50 m). (c) Directional Antennas (150 m to 300 m). (d) Omnidirectional antennas (100 m to 

300 m). Averaging bandwidth was 200 MHz. 

(a) (b) 
48 

21B5.4 Conclusion 

The three buildings studied here exhibit complicated scattering and multipath 

propagation as functions of both distance and frequency. These characteristics are due 

to a combination of metallic walls and ceilings, concrete floors, and a multitude of 

metallic scatterers inside the plants. 

One example of the complicated nature of radio-wave propagation in these 

facilities is well illustrated by the interference patterns seen in the UWB measurements 

of Figures 5-9 and 5-10. The signals emitted from our antennas were constrained to 

propagate down the aisleways by the antennas that we used and by the metallic 

structures on either side of the aisle. Very little energy was transmitted up and over the 

structures lining the aisles. Thus, under line-of-sight conditions, signals sometimes 

experienced deep interference nulls when the receiver was located midway between the 

transmitter and a reflecting surface such as a wall or even a perpendicular corridor, as 

shown in Figures 5-9(b) and 5-10(b). When the receiver was located around the corner 

from the transmitter, radio-wave penetration through the metallic structures in the plants 

was not possible. As a result, in non-line-of-sight conditions, signals were attenuated 

and exhibited classical, noise-like, Rayleigh-distributed behavior. 

The UWB measurements also showed that the use of directional antennas 

reduced the RMS delay spread. We saw this in the stamping and engine plants, the 

only two facilities where we calculated RMS delay spread. The RMS delay spread in the 

engine plant was significantly longer than that of the stamping plant, highlighting the 

more open floor plan in the engine plant. Reflections take longer to die out in this 

environment. When delay spread becomes long enough, it can interfere with the error 

correction in the transmission and additional errors can occur. 

The impact on wireless communications will depend on the type of system, data 

rate, and the location of the transmitter(s) and receiver(s). The representative 

measurements provided here of excess path loss, RMS delay spread, and K-factor are 

useful parameters that we hope will guide the design of wireless communications 

systems in these types of plants. 

5B6. Summary 

 Our background ambient measurements offered a few surprises. While they 

showed expected significant transmission activity in the 2.4 GHz unlicensed ISM 

frequency bands, there was essentially no activity in the 5.8 GHz band at the engine 

plant, and little in the 900 MHz frequency band in either plant. As expected, we saw 

transmissions from external sources such as broadcast stations and cellular telephone 

traffic. Since these are in frequency bands outside the operational bands of interest, 

they do not currently cause interference to operations. Finally, we saw some 

unintentionally generated machine noise at low frequencies within the stamping plant. 

This unintentionally transmitted noise can affect systems that operate at lower 

frequencies, such as diagnostics used in automotive applications. 

The site-specific spectrum analyzer measurement results showed that wireless 

transmissions in the 2.4 GHz frequency band can be detected at most locations 

throughout these two facilities. This indicates that transmitting and repeating nodes 

have been successfully installed throughout the plants. 
49 

UWB scattering measurements show that these facilities are highly reflective, 

reverberant environments that can complicate reliable performance of wireless 

technology. While the existing wireless technology has been successfully deployed, 

future expanded use of wireless for control and telemetry operations could pose an 

interference problem if the environment is not considered. 

There are several methods that can be implemented to minimize the effects of 

the reflective environment. Some are operational in nature, some deal with changing the 

environment, and some are technology based. Examples of these methods include: 

Operational 

 Use licensed frequency bands where possible 

 Coordinate frequency and channel usage 

 Restrict or forbid use of personal electronics in key frequency bands (e.g., 

2.4 GHz band) 

Environmental 

 Install absorbing material in the proximity of local wireless systems such as 

controllers 

 Place additional nodes at key locations 

Technological 

 Use wireless systems having high immunity to electromagnetic interference 

 Use wireless systems designed to operate in high multipath environments 

 Employ equipment on the production floor that emit little machine noise 

 Use directional antennas where appropriate 

 The results of this and the prior study at the assembly plant will be used to 

generate improved statistical models that describe the RF nature of the production floor 

for wireless systems. These models may be used by telecommunications manufacturers 

to engineer more robust designs for communications equipment, as well as for 

development of improved standards specifically for the automotive industry. 

Also, based on the measured results from the three automotive plants we have 

tested, work is currently underway at NIST to develop laboratory-based test methods to 

prequalify wireless devices for deployment on the factory floor. The test methods are 

based on measuring a device’s functionality when placed in a reverberation chamber 

whose characteristics have been tuned to simulate those of the factory floor. If a device 

operates properly in the test chamber, engineers can be confident that it would operate 

on the factory floor as well. 

Partial funding and support for this work was provided by the NIST United States 

Council for Automotive Research (USCAR) Liaison Dr. John Slotwinski, NIST 

Manufacturing Engineering Laboratory, National Institute of Standards and Technology, 

Gaithersburg, MD 20899-8200. 
50 

6B7. References 

[1] IEEE Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) 

Specifications: Higher-Speed Physical Layer Extension in the 2.4 GHz Band, IEEE 

Standard 802.11bTM-1999. 

[2] IEEE Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) 

Specifications: High-Speed Physical Layer in the 5 GHz Band, IEEE Standard 802.11aTM1999. 

[3] K.A. Remley, G. Koepke, C.L. Holloway, C. Grosvenor, D. Camell, J. Ladbury, D. Novotny, 

W.F. Young, G. Hough, M.D. McKinley, Y. Becquet, J. Korsnes, “Measurements to Support 

Broadband Modulated-Signal Radio Transmissions for the Public-Safety Sector,” Natl. Inst. 

Stand. Technol. Note 1546, Apr. 2008. 
51 

7BAppendix A: Assembly Plant, Low-Frequency Data, 

Omnidirectional Transmit and Receive Antennas 

The following pages contain the complete set of measured data from the assembly plant 

covering a frequency range of 100 MHz to 1.2 GHz when omnidirectional transmit and 

receive antennas were used. 
52 

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

10 m separation

System Noise (300m)

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

5 m separation

System Noise (300m)

Assembly Plant: Omnidirectional antennas

Figure A.1: Excess path loss from 100 MHz to 1.2 GHz in the assembly plant. Top: 5 

m separation. Bottom: 10 m separation. 
53 

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

50 m separation

System Noise (300m)

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

20 m separation

System Noise (300m)

Assembly Plant: Omnidirectional antennas

Figure A.2: Excess path loss from 100 MHz to 1.2 GHz in the assembly plant. Top: 

20 m separation. Bottom: 50 m separation. 
54 

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

100 m separation

System Noise (300m)

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

75 m separation

System Noise (300m)

Assembly Plant: Omnidirectional antennas

Figure A.3: Excess path loss from 100 MHz to 1.2 GHz in the assembly plant. Top: 

75 m separation. Bottom: 100 m separation. 
55 

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

150 m separation

System Noise (300m)

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

125 m separation

System Noise (300m)

Assembly Plant: Omnidirectional antennas

Figure A.4: Excess path loss from 100 MHz to 1.2 GHz in the assembly plant. Top: 

125 m separation. Bottom: 150 m separation. 
56 

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

200 m separation

System Noise (300m)

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

175 m separation

System Noise (300m)

Assembly Plant: Omnidirectional antennas

Figure A.5: Excess path loss from 100 MHz to 1.2 GHz in the assembly plant. Top: 

175 m separation. Bottom: 200 m separation. 
57 

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

250 m separation

System Noise (300m)

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

225 m separation

System Noise (300m)

Assembly Plant: Omnidirectional antennas

Figure A.6: Excess path loss from 100 MHz to 1.2 GHz in the assembly plant. Top: 

225 m separation. Bottom: 250 m separation. 
58 

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

300 m separation

System Noise (300m)

0 200 400 600 800 1000 1200 1400

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - Diamond Discones

275 m separation

System Noise (300m)

Assembly Plant: Omnidirectional antennas

Figure A.7: Excess path loss from 100 MHz to 1.2 GHz in the assembly plant. Top: 

275 m separation. Bottom: 300 m separation. 
59 

Appendix B: Assembly Plant, High-Frequency Data, 

Directional Transmit, Omnidirectional Receive Antennas

The following pages contain the complete set of measured data from the assembly plant 

covering a frequency range of 1 GHz to 12 GHz when directional transmit and 

omnidirectional receive antennas were used. 
60 

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

10 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

5 m separation

System Noise (300m)

Assembly Plant: Directional transmit, omnidirectional receive antennas

Figure B.1: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 5 m 

separation. Bottom: 10 m separation. 
61 

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

50 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

20 m separation

System Noise (300m)

Assembly Plant: Directional transmit, omnidirectional receive antennas

Figure B.2: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

20 m separation. Bottom: 50 m separation. 
62 

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

125 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

100 m separation

System Noise (300m)

Assembly Plant: Directional transmit, omnidirectional receive antennas

Figure B.3: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

100 m separation. Bottom: 125 m separation. 
63 

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

175 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

150 m separation

System Noise (300m)

Assembly Plant: Directional transmit, omnidirectional receive antennas

Figure B.4: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

150 m separation. Bottom: 175 m separation. 
64 

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

225 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

200 m separation

System Noise (300m)

Assembly Plant: Directional transmit, omnidirectional receive antennas

Figure B.5: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

200 m separation. Bottom: 225 m separation. 
65 

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

275 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

250 m separation

System Noise (300m)

Assembly Plant: Directional transmit, omnidirectional receive antennas

Figure B.6: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

250 m separation. Bottom: 275 m separation. 
66 

0 4000 8000 12000

Frequency (MHz)

-120

-80

-40

0

40

Excess Path Loss (dB)

Assembly Plant - DRG to Tophat

300 m separation

System Noise (300m)

Assembly Plant: Directional transmit, omnidirectional receive antennas

Figure B.7: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

300 m separation. 
67 

Appendix C: Assembly Plant, High-Frequency Data, 

Directional Transmit and Receive Antennas

The following pages contain the complete set of measured data from the assembly plant 

covering a frequency range of 1 GHz to 12 GHz when directional transmit and receive 

antennas were used. 
68 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

10 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

5 m separation

System Noise (300m)

Assembly Plant: Directional transmit and receive antennas

Figure C.1: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 5 m 

separation. Bottom: 10 m separation. 
69 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

50 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

20 m separation

System Noise (300m)

Assembly Plant: Directional transmit and receive antennas

Figure C.2: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

20 m separation. Bottom: 50 m separation. 
70 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

125 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

100 m separation

System Noise (300m)

Assembly Plant: Directional transmit and receive antennas

Figure C.3: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

100 m separation. Bottom: 125 m separation. 
71 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

175 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

150 m separation

System Noise (300m)

Assembly Plant: Directional transmit and receive antennas

Figure C.4: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

150 m separation. Bottom: 175 m separation. 
72 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

225 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

200 m separation

System Noise (300m)

Assembly Plant: Directional transmit and receive antennas

Figure C.5: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

200 m separation. Bottom: 225 m separation. 
73 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

275 m separation

System Noise (300m)

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

250 m separation

System Noise (300m)

Assembly Plant: Directional transmit and receive antennas

Figure C.6: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

250 m separation. Bottom: 275 m separation. 
74 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

275 m separation

System Noise (300m)

Assembly Plant: Directional transmit and receive antennas

Figure C.7: Excess path loss from 1 GHz to 12 GHz in the assembly plant. Top: 

300 m separation. 

300m separation
75 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

100 m separation - boresight

100 m separation - 45- 0clock position

100 m separation - 45- 90clock position

100 m separation - 45- 180clock position

100 m separation - 45- 270clock position

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

50 m separation - boresight

50 m separation - 45- 0clock position

50 m separation - 45- 90clock position

50 m separation - 45- 180clock position

50 m separation - 45- 270clock position

Assembly Plant: Directional transmit and receive antennas

Figure C.8: Excess path loss from 1 GHz to 12 GHz in the assembly plant when the 

receive antenna is rotated through angles from zero (boresight) to 270° as defined in 

Figure 5-3 for the stamping plant. Top: 50 m separation. Bottom: 100 m separation. 
76 

0 4000 8000 12000

Frequency (MHz)

-120

-100

-80

-60

-40

-20

0

20

Excess Path Loss (dB)

Assembly Plant - DRG to DRG

300 m separation - boresight

300 m separation - 45- 0clock position

300 m separation - 45- 90clock position

300 m separation - 45- 180clock position

300 m separation - 45- 270clock position

Assembly Plant: Directional transmit and receive antennas

Figure C.9: Excess path loss from 1 GHz to 12 GHz in the assembly plant when the 

receive antenna is rotated through angles from zero (boresight) to 270° as defined in 

Figure 5-3 for the stamping plant. Top: 300 m separation. 
77 

8BAppendix D: Stamping Plant, Low-Frequency Data, 

Omnidirectional Transmit and Receive Antennas 

The following pages contain the complete set of measured data from the stamping plant 

covering a frequency range of 100 MHz to 1.2 GHz when omnidirectional transmit and 

receive antennas were used. 
78 

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

20 m separation

System Noise (20 m)

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

10 m separation

System Noise (20 m)

Metal Stamping Plant: Omnidirectional antennas

Figure D.1: Excess path loss from 100 MHz to 1.2 GHz in the stamping plant. Top: 

10 m separation. Bottom: 20 m separation. 
79 

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

50 m separation

System Noise (20 m)

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

40 m separation

System Noise (20 m)

Metal Stamping Plant: Omnidirectional antennas

Figure D.2: Excess path loss from 100 MHz to 1.2 GHz in the stamping plant. Top: 

40 m separation. Bottom: 50 m separation. 
80 

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

75 m separation 

System Noise (60 m)

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

60 m separation

System Noise (60 m)

Metal Stamping Plant: Omnidirectional antennas

Figure D.3: Excess path loss from 100 MHz to 1.2 GHz in the stamping plant. Top: 

60 m separation. Bottom: 75 m separation. 
81 

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant 

Diamond to Diamond

100 m separation 

System Noise (110m, A)

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

80 m separation 

System Noise (60 m)

Metal Stamping Plant: Omnidirectional antennas

Figure D.4: Excess path loss from 100 MHz to 1.2 GHz in the stamping plant. Top: 

80 m separation. Bottom: 100 m separation. 
82 

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

110 m separation (B)

System Noise (110m, A)

110 m separation (B) - repeat measurement

0 500 1000 1500

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

Diamond to Diamond

110 m separation (A)

System Noise (110m, A)

Metal Stamping Plant: Omnidirectional antennas

Figure D.5: Excess path loss from 100 MHz to 1.2 GHz in the stamping plant. Top: 

110 m separation, straight path. Bottom: 110 m separation, around corner. See 

Figure 5.3 
83 

9BAppendix E: Metal Stamping Plant, High-Frequency Data, 

Directional Transmit, Omnidirectional Receive Antennas 

The following pages contain the complete set of measured data from the metal 

stamping plant covering a frequency range of 1 GHz to 12 GHz when directional 

transmit and omnidirectional receive antennas were used. 
84 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

20 m separation

System Noise (20 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

10 m separation

System Noise (20 m)

Stamping Plant: Directional transmit, omnidirectional receive antennas

Figure E.1: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 10 m 

separation. Bottom: 20 m separation. 
85 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

50 m separation

System Noise (40 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

40 m separation

System Noise (40 m)

Stamping Plant: Directional transmit, omnidirectional receive antennas

Figure E.2: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 40 m 

separation. Bottom: 50 m separation. 
86 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

75 m separation

System Noise (40 m)

75 m separation-repeat measurement

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

60 m separation

System Noise (40 m)

Stamping Plant: Directional transmit, omnidirectional receive antennas

Figure E.3: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 60 m 

separation. Bottom: 75 m separation. 
87 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

90 m separation

System Noise (80 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

80 m separation

System Noise (80 m)

Stamping Plant: Directional transmit, omnidirectional receive antennas

Figure E.4: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 80 m 

separation. Bottom: 90 m separation. 
88 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

110 m separation (B)

110 m separation (A)

System Noise (80 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to ARA (Tophat)

100 m separation

System Noise (80 m)

Stamping Plant: Directional transmit, omnidirectional receive antennas

Figure E.5: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 100 

m separation. Bottom: 110 m separation, see Figure 5-3. 
89 

10BAppendix F: Metal Stamping Plant, High-Frequency Data, 

Directional Transmit and Receive Antennas 

The following pages contain the complete set of measured data from the metal 

stamping plant covering a frequency range of 1 GHz to 12 GHz when directional 

transmit and receive antennas were used. 
90 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

10 m separation

System Noise (20 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

6 m separation

System Noise (20 m)

Stamping Plant: Directional transmit, receive antennas

Figure F.1: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 6 m 

separation. Bottom: 10 m separation. 
91 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

40 m separation

System Noise (40 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

20 m separation

System Noise (20 m)

Stamping Plant: Directional transmit, receive antennas

Figure F.2: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 20 m 

separation. Bottom: 40 m separation. 
92 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

60 m separation

System Noise (40 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

50 m separation

System Noise (40 m)

Stamping Plant: Directional transmit, receive antennas

Figure F.3: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 50 m 

separation. Bottom: 60 m separation. 
93 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

80 m separation

System Noise (80 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

75 m separation

System Noise (40 m)

Stamping Plant: Directional transmit, receive antennas

Figure F.4: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 75 m 

separation. Bottom: 80 m separation. 
94 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant 

DRG to DRG

100 m separation

System Noise (80 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

90 m separation

System Noise (80 m)

Stamping Plant: Directional transmit, receive antennas

Figure F.5: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 90 m 

separation. Bottom: 100 m separation. 
95 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

110 m separation (B)

System Noise (80 m)

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant

DRG to DRG

110 m separation (A)

System Noise (80 m)

Stamping Plant: Directional transmit, receive antennas

Figure F.6: Excess path loss from 1 GHz to 12 GHz in the stamping plant. Top: 

110 m separation, straight. Bottom: 110 m separation, around corner. See Figure 5-3. 
96 

0 4000 8000 12000 16000 20000

Frequency (MHz)

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Excess Path Loss (dB)

Stamping Plant 

DRG to DRG

50 m separation

50 m separation - elevated, 6 o'clock

50 m separation - elevated, 3 o'clock

50 m separation - elevated, 12 o'clock

50 m separation - elevated, 9 o'clock

Metal Stamping Plant: Directional transmit and receive antennas

Figure F.7: Excess path loss from 1 GHz to 12 GHz in the metal stamping plant 

when the receive antenna is rotated through angles from zero (boresight) to 270° as 

defined in Figure 5-3. Top: 50 m separation. 
97 

1BAppendix G: Engine Plant, Low-Frequency Data, 

Omnidirectional Transmit and Receive Antennas 

The following pages contain the complete set of measured data from the engine plant 

covering a frequency range of 100 MHz to 1.5 GHz when omnidirectional transmit and 

receive antennas were used. 
98 

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

20m Separation

System Noise, 20m

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

10m Separation

System Noise, 20m

Engine Plant: Omnidirectional transmit, receive antennas

Figure G.1: Excess path loss from 100 MHz to 1.5 GHz in the engine plant. Top: 

10 m separation. Bottom: 20 m separation. 
99 

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

50m Separation

System Noise, 50m

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

40m Separation

System Noise, 50m

System Noise, 20m

Engine Plant: Omnidirectional transmit, receive antennas

Figure G.2: Excess path loss from 100 MHz to 1.5 GHz in the engine plant. Top: 

40 m separation. Bottom: 50 m separation. 
100 

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

80m Separation

System Noise, 120m B

System Noise, 50m

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

60m Separation

System Noise, 50m

Engine Plant: Omnidirectional transmit, receive antennas

Figure G.3: Excess path loss from 100 MHz to 1.5 GHz in the engine plant. Top: 

60 m separation. Bottom: 80 m separation. 
101 

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

120m-A Separation

System Noise, 120m B

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

100m Separation

System Noise, 120m B

Engine Plant: Omnidirectional transmit, receive antennas

Figure G.4: Excess path loss from 100 MHz to 1.5 GHz in the engine plant. Top: 

100 m separation. Bottom: 120 m separation, straight path (see Figure 5-6). 
102 

0 250 500 750 1000 1250 1500

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, biconicals

120m-B Separation

System Noise, 120m B

Engine Plant: Omnidirectional transmit, receive antennas

Figure G.5: Excess path loss from 100 MHz to 1.5 GHz in the engine plant. Top: 

120 m separation, corner path (see Figure 5-6). 
103 

12BAppendix H: Engine Plant, High-Frequency Data, Directional 

Transmit Antenna, Omnidirectional Receive Antenna 

The following pages contain the complete set of measured data from the engine plant 

covering a frequency range of 500 MHz to 18 GHz when a directional transmit antenna 

and an omnidirectional receive antenna were used. 
104 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

20m Separation

System Noise, 10m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

10m Separation

System Noise, 10m

Engine Plant: Directional transmit, omnidirectional receive antennas

Figure H.1: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 10 m 

separation. Bottom: 20 m separation. 
105 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

50m Separation

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

40m Separation

System Noise, 50m

System Noise, 10m

Engine Plant: Directional transmit, omnidirectional receive antennas

Figure H.2: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 40 m 

separation. Bottom: 50 m separation. 
106 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

80m Separation

System Noise, 120m-B

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

60m Separation

System Noise, 50m

Engine Plant: Directional transmit, omnidirectional receive antennas

Figure H.3: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 60 m 

separation. Bottom: 80 m separation. 
107 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

120m-A Separation

System Noise, 120m-B

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

100m Separation

System Noise, 120m-B

Engine Plant: Directional transmit, omnidirectional receive antennas

Figure H.4: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 

100 m separation. Bottom: 120 m separation, straight path (see Figure 5-6). 
108 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-tophat

120m-B Separation

System Noise, 120m-B

Engine Plant: Directional transmit, omnidirectional receive antennas

Figure H.5: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 

120 m separation, corner path (see Figure 5-6). 
109 

13BAppendix I: Engine Plant, High-Frequency Data, Directional 

Transmit and Receive Antennas 

The following pages contain the complete set of measured data from the engine plant 

covering a frequency range of 500 MHz to 18 GHz when directional transmit and 

receive antennas were used. 
110 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

20m Separation

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

10m Separation

System Noise, 50m

Engine Plant: Directional transmit, receive antennas

Figure I.1: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 10 m 

separation. Bottom: 20 m separation. 
111 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

50m Separation

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

40m Separation

System Noise, 50m

Engine Plant: Directional transmit, receive antennas

Figure I.2: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 40 m 

separation. Bottom: 50 m separation. 
112 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

80m Separation

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

60m Separation

System Noise, 50m

Engine Plant: Directional transmit, receive antennas

Figure I.3: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 60 m 

separation. Bottom: 80 m separation. 
113 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

120m-A Separation

System Noise, 50m

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

100m Separation

System Noise, 50m

Engine Plant: Directional transmit, receive antennas

Figure I.4: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top: 

100 m separation. Bottom: 120 m separation, straight path (see Figure 5-6). 
114 

2000 4000 6000 8000 10000 12000 14000 16000 18000

Frequency (MHz)

-100

-80

-60

-40

-20

0

20

40

Excess Path Loss (dB)

Engine Plant, DRG-DRG

120m-B Separation

System Noise, 50m

Engine Plant: Directional transmit, receive antennas

Figure I.5: Excess path loss from 500 MHz to 18 GHz in the engine plant. Top:120 m 

separation, corner path (see Figure 5-6). 
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