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A11107 D4TD3T I

National Institute of Standards and Technology

Technology Administration, U.S. Department of Commerce

NIST Technical Note 1547

NIST Technical Note 1547

Electromagnetic Airframe Penetration

IVIeasurements for the FAA

Bombardier Global 5000

Chriss Grosvenor, David Novotny, Dennis Camel!, and Galen Koepke

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

June 2008

%"A 1

"'^S-^'-^J^

U.S. Department of Commerce

Carlos M. Gutierrez, Secretary

National Institute of Standards and Technology

James M. Turner, Deputy Director
National Institute of Standards U.S. Government Printing Office For Sale by the

and Technology Washington: 2008 Superintendent of Documents

Technical Note 1547 U.S. Government Printing Office

Natl. Inst. Stand. Technol. Stop SSOP, Washington, DC 20402-0001

Tech. Note 1 547 Phone: (202) 512-1 800

XX pages (Date 2008) Fax: (202) 51 2-2250

CODEN: NTNOEF Internet: bookstore.gpo.gov
Contents

1

.

History and Background 1

2. Overview 3

3. Measurement System 6

4. Measurement of Electromagnetic Airframe Penetration 8

5. Reference Measurements 12

6. Airframe Penetration Measurements — Overview 18

6.

1

Extrapolation Results 19

6.2 Main Passenger Cabin Penetration Results 21

6.3 Flight Deck Penetration Results 44

6.4 Cargo Closet Penetration Results 61

6.5 HIRE Positions for Flight Deck Penetration 79

6.6 Internal Coupling Measurements 83

7. Uncertainty Analysis 90

8. Summary and Conclusions 93

9. References 97

Appendix A. Time Domain Waveform Analysis 98

Appendix B. Signal and Noise Characteristics 109

Appendix C. TEM and DRG Horn Boresight Gain Characteristics 112

Appendix D. Penetration Data for HIRE Frequency Bands 114

Appendix E. Bombardier Global 5000 Measurement Equipment List 119

ni
IV
Electromagnetic Airframe Penetration

Measurements for the FAA

Bombardier Global 5000

Chriss Grosvenor, David Novotny, Dennis Camell, and Galen Koepke

Electromagnetics Division

National Institute of Standards and Technology

325 Broadway

Boulder, CO 80305

and

Robert T. Johnk

National Telecommunication and Information Agency

Institute for Telecommunication Sciences

325 Broadway

Boulder, CO 80305

The National Institute ofStandards and Technology has recently completed shielding

effectiveness/penetration studies on three different aircraft types for the Federal Aviation

Administration. The studies are used to understand the cavity coupling characteristics between

antennas placed in various compartments inside the aircraft and antennas placed at various

angular positions around an aircraft. This document shows how penetration varies as afunction

offrequency, antenna type, antenna polarization, and cavity susceptibilityfor a Bombardier

Global 5000 businessjet. Internal coupling between two antennas placed in the aircraft at

different locations to determine the qualityfactor and the time decay offields is also presented.

These measurements will provide the Federal Aviation Administration with a database on

penetrationfor three different classes ofaircraft.

Key words: aircraft; cavity coupling; digital signal processing; HIRF; penetration; shielding

effectiveness; synthetic time-domain measurements.

1. History and Background

The Field Parameters and EMC Applications Project of the National Institute of Standards and

Technology (NIST) has recently completed shielding effectiveness studies of three representative

aircraft for the Federal Aviation Administration (FAA). These studies will be used to provide

the FAA with the procedures and data reduction techniques for typical low-level airframe

penetration for high intensity radiated field (HIRF) attenuation/shielding tests. This technical

note addresses aircraft shielding tests conducted on a Bombardier Global 5000 business jet

owned and operated by the FAA. Two additional reports will detail studies of (1) a 737-200

owned and operated by the FAA and (2) a Beechcraft Premier lA owned by the Hawker-
Beechcraft Corporation. The 737-200 represents a typical commercial aircraft, and the Premier

lA represents a typical carbon-composite aircraft. By measuring all three aircraft and comparing

them, we have the potential to provide a "design roadmap" for the optimization of HIRF testing

standards for the electromagnetic compatibility (EMC) aircraft manufacturing community.

The FAA currently has specific certification policies addressing the effects of HIRF on an

aircraft's electrical and electronic systems that have been applied for the past 19 years [1]. In the

FAA document, the regulatory authorities and industry have defined HIRF environments,

requirements for aircraft HIRF protection, and methods for testing and verifying the level of

HIRF protection. Most of reference [1] discusses HIRF testing for electronic and electrical

subsystems, which this technical note does not address. In this technical note, we specifically

address both high- and low-level airframe shielding compliance testing. The HIRF procedures

are found in Section 6.6.2.6 and Section 6.6.4 of Reference [1].

The basic problem is to evaluate the coupling of an external source into a large, leaky cavity. The

cavity could represent the whole aircraft or a zone (cargo bay, flight deck, etc.) depending on the

expected vulnerability. In a typical HIRF measurement, the measurement system is calibrated

and a reference measurement is taken without the aircraft embedded in the test setup. The

aircraft is then placed into the test setup and various measurements are taken in susceptible

cavities. These attenuation tests are typically conducted using either mechanical stirring or frequency stirring methods [2,3]. The airframe attenuation is calculated by use of the following

equation,

. _ (^ P

_ reference measurement

^^^ atten cavity measurement

where A^atten is the airframe attenuation and S.E. is defined as the shielding effectiveness. These

numbers, expressed in decibels, are typically positive so that the more positive the number, the

greater the protection the aircraft provides to electromagnetic fields, and as the number

approaches zero we expect almost no shielding protection. The aircraft HIRF attenuation data

vary as a function of frequency, physical position of the measurement antenna, characteristics of

the aircraft, and configuration of the test site. After a company tests and processes the data, the

information is given to the FAA, which uses it, in conjunction with the subsystem susceptibility

tests to determine an aircraft's HIRF vulnerability.

The detailed method used to process aircraft HIRF attenuation data is not well documented and

is closely held by the handfiil of test service providers. Therefore, the interpretation of the data

is not immediately obvious to the certification engineer. This technical note and the two to follow will consider attenuation measurements as a fiinction of frequency, antenna position,

antenna type, and cavity selection. Our data processing methodology will be shown in detail.

Using this information, we hope to provide guidelines for both the FAA and test engineers to develop a uniform and transparent test method for data processing and documentation. We know

that the confidence levels are expected to be dependent on the number of sample points
(measurement geometries), but we should be able to assess the trade-offs between measurement

effort (sample number) and risk (confidence level).

2. Overview

This report summarizes results of a measurement effort conducted by the Field Parameters and

EMC Applications Project team of NIST. This effort consisted of an extensive series of

penetration measurements performed on a Bombardier Global 5000 owned and operated by the

FAA. The aircraft was tested at the FAA site in Atlantic City, New Jersey during the period from

October 3, 2005 to October 8, 2005. The purpose of this effort is to provide the FAA with a database of penetration data on the Bombardier Global 5000, which is a commercial business jet.

The effort utilized NIST-developed measurement systems consisting of ultra-wideband

transverse electromagnetic (TEM) horn antennas, 3117 dual-ridged guided (DRG) horn antennas,

a commercially available vector network analyzer (VNA), interconnecting transmission media,

and an amplifier. Interconnections between transmitting and receiving antennas were made

using 1 1 GHz and 1 8 GHz precision, analog electro-optic links. This effort was the first time

NIST researchers used a broadband, analog, electro-optic link in conjunction with a configurable

VNA and amplifier for airframe shielding studies up to 18 GHz. Shielding data are obtained

fi-om a direct comparison of two measurements: (1) a transmission measurement between

boresighted antennas located outside the aircraft to obtain a reference, and (2) transmission

measurements with one antenna located inside a selected compartment of the aircraft and a pair

of horizontally and vertically polarized antennas for both low-frequency-band and highfrequency-band antennas located outside the aircraft at specified locations. Shielding data are obtained by comparing processed reference and aircraft transmission data. This is achieved

using an efficient sequence of Fourier and inverse Fourier transformations, frequency domain

convolutions, and filtering combined with time gating and frequency averaging. Shielding

values are obtained by taking the ratio of the gated amplitude spectra of the aircraft measurement

and the gated amplitude spectra of the references. Data smoothing is performed using the

frequency-averaging of signal power over a specified bandwidth as described in [2]:

K.')=^"^''.,M^) i=n-N

(1)

Shielding data were obtained with a receiving antenna located in one of three internal

compartments: (1) the main passenger cabin, (2) the flight deck, and (3) the internal aft cargo

closet. A pair of transmitting antennas was positioned outside the aircraft at a fixed height of 4

m, which is the approximate height of the windows, at a fixed distance of 23 m from the center

of the aircraft. The transmitting antennas were boresighted at the center of the aircraft, and data were obtained for both the horizontal and vertical polarizations. We based our tests on HIRE

standard test procedures and other questions we felt were important to ask. These standards are concerned with detecting possible leakage into the aircraft. Key areas include the flight deck, the

avionics bay, any windows/doors/joints, and the wing/tail section of the fuselage. We defined a

test setup at various angular positions around the aircraft, around the flight deck of the aircraft at five positions at a constant distance from the front landing gear of the aircraft, and internal
coupling measurements. In a recent paper [4], questions were raised as to how many positions

need to be measured around an electrically large object to fully characterize the fields penetrating

into the aircraft for a particular high-fi-equency limit. For this reason, we designed the test plan

as follows: (1) From 0° to 120°, measurements were conducted every 10°; (2) from 120° to 160°

and from 330° to 360°, measurements were carried out in 5° increments; and (3) additional

measurements were carried out at 190° and 270° in order to look at symmetry. Finally, we

concluded with a set of internal coupling measurements to understand the reverberant

environment internal to the aircraft. An aircraft's level of electromagnetic field protection,

referred to as shielding, depends on the level of treatment, the compartment, the frequency, the

transmitting antenna polarization, and the angle of illumination. In this document, we will

display penetration values, which are the reciprocal of shielding values. On the graphs that

follow, a penetration near dB means electromagnetic fields can easily penetrate into that part of

the aircraft. Penetration levels for the Global 5000 Bombardier range from approximately dB

to -45 dB. The estimated dynamic range of this system is 50 dB at 4000 MHz and 30 dB at

1 8,000 MHz. Maximum penetration results were obtained with the receiving antenna in the

main passenger cabin, while lower values were obtained in the flight deck and the aft cargo

closet. Maximum penetration in the main passenger cabin was observed with the transmitting

antennas illuminating the aircraft from positions located at the side of the aircraft. Minimum

penetration was seen in the aft cargo closet at both the nose and tail positions.

This report is divided into five main sections: (1) a description of the measurement system, (2) an overview of the measurement technique, (3) an overview of the signal processing, (4) a summary of results for the three different aircraft compartments and various internal

measurements, and (5) an uncertainty analysis. Five appendices discuss the impact of time

gating, signal and noise, an equipment list, maximum penetration as a function of the HIRF

specified frequency bands, and the gain characteristics of the ultra-wideband antennas that were

used.
3. Measurement System

The configuration of the NIST measurement system for these aircraft measurements is shown in Figures 1 and 2. The system consists of: (1) a VNA, (2) two transmitting TEM horn antennas

and two DRG horn antennas configured for the horizontal and vertical polarizations,

respectively, (3) a receiving TEM horn antenna and DRG antenna, (4) two coaxial microwave

switches to select the polarization of the transmit antennas, and (5) two precision analog electrooptic links to cover both fi"equency bands and to provide an interconnection between the

transmitting antennas outside the aircraft and the receiving antenna inside. These links provide a

significant improvement in performance over conventional microwave cables. The optical links

result in low transmission losses and low noise, and they do not pick up common-mode noise

from environmental ambient signals. The optical links also provide an improvement in dynamic

range and have better immunity from electromagnetic interference. The heart of this system is a commercially available four-port VNA that has been configured to acquire complex transmission

data (S31 for the TEM antennas and S42 for the DRG antennas, in-phase and quadrature signals).

Due to the internal hardware, the VNA was limited to a maximum of 1 600 1 frequencies, but we

developed software that extends the number of frequencies to any desired value. If we need

more than 16001 points, the software subdivides a given frequency range into a user-selected

number of 16001 point sub-bands. The DRG horn antennas operate from 1 GHz to 18 GHz and were configured using two bands, resulting in 32002 equally spaced measurement points from

approximately 0.5 MHz to 18 GHz. The TEM horn antennas operate from 0.1 GHz to 4 GHz

and were configured using one band, resulting in 6401 equally spaced measurement points from

Optical link to optical receiver

Figure 1 . Airframe shielding measurement system (receiving side). The reverberant nature of the airframe permits the reception of both horizontally and vertically polarized signals.
approximately 0.5 MHz to 4 GHz. A reduced frequency spacing is necessary to avoid problems

due to aliasing. Prior to connecting the cables to the antennas, a calibration of all channels was

performed to remove systematic transmission effects due to cabling, switches, and the frequency

and phase variations of the optical transmission link. This procedure calibrates the system with

respect to the input of the transmitting and receiving antennas. Three NIST-developed ultrawideband TEM horn antennas were used: two 1 .2 m antennas on a tower located outside of the

aircraft, either to transmit horizontally and vertically polarized fields, and a more compact 36 cm

TEM horn located in a pre-selected aircraft compartment to detect energy coupled into the

airframe. For the higher frequency bands, three commercially available DRG antennas were

used: two on the same transmitting tower located outside of the aircraft to transmit horizontally

and vertically polarized fields, and a DRG antenna located in the same preselected aircraft

compartment to detect energy coupled into the airframe. The frequency data were digitized and

transferred to a laptop computer for subsequent data analysis and signal processing.

4. Measurement of Electromagnetic Airframe Penetration

The extraction of airframe penetration characteristics requires a two-step measurement process,

shown in Figure 3. In the first step, a reference transmission measurement is performed by

Transmitting TEM

horn antennas\

Transmitting TEM

horn antennas

Channel

H-pol Channel 2 V-pol

Transmitting DRG

horn antennas

(Side view)

Tower

Laptop

1 1 GHz Optical

link receiver 18 GHz Optical

link receiver <---

Optical fiber from aircraft

Figure 2. Transmitting side of the airframe shielding measurement system.
boresighting the transmitting and receiving antennas at a fixed distance. The reference

measurements were performed at a location away from the aircraft in order to minimize

reflections from the aircraft. This measurement quantifies the energy incident on the aircraft, and

enables us to calibrate and remove the frequency-dependent effects of the antennas and

interconnecting hardware. In the second step, the receiving antenna was placed in a selected

aircraft compartment; the transmitting antennas were placed at fixed locations, external to the

aircraft, and stepped-frequency transmission data were acquired.

The reference and airframe data were processed using a sequence of filtering, Fourier transforms,

and time gating to obtain the penetration values. The basic process through which the data were

obtained is shown in Figure 4. The raw frequency data were first filtered to maximize the signalto-noise ratio and to minimize effects from the low-frequency cut-off of our electro-optic link.

Next, a tapered frequency-domain window was applied to both sets of data to reduce Gibbs

ringing in subsequent processing. An inverse Fourier transform (IFT) was then applied to the

processed data to obtain time-domain waveforms. Time gates were then applied to isolate the

desired portions of waveforms and remove undesired portions. In the case of the reference, the

time gate was applied to isolate the direct antenna-to-antenna coupling and remove the effects of

ground bounce and late-time reflections. Time gating was applied to the airframe data to isolate

either the direct illumination or reverberant fields of the aircraft. Effects from ground bounce are embedded in the waveforms at this distance and therefore cannot be removed by time-gating.

The time-gated data sets were then transformed back into the frequency domain, and the

Transmitting antennas Receiving

antennas

Optical fiber

Reference measurement

Transmitting antennas /

~{°' /^Cj ;Q

Receiving

antennas

II II N

^

Figure 3. Two-step airframe shielding measurement procedure used in the

Bombardier Global 5000 evaluation.
penetration (PE), was computed from the deconvolution:

PE = DCS^2 {g(^ted airframe)

S^2 {gated reference

)

(2)

where S^iigated reference) is the antenna-to-antenna couphng with environmental effects gated

out, and S^iigated airframe) is the airframe transmission with gating appHed to minimize noise.

Since the reference and airframe measurements are typically carried out at different distances, a

distance correction, {DC), was applied.

Transmission measurement through airframe

Stepped-frequency

aircraft data

Background=0

Stepped-fi-equency antenna reference

Background=0

1

Appropriate filter to emphasize signal

I

Appropriate filter to emphasize signal

Condition data for FT

and reduce Gibbs ringing

T

I

Condition data for FT

and reduce Gibbs ringing

Apply time gate(s) to isolate sample response

T

Apply time gate to

isolate sample response

Remove conditioning

For IFT

I

Remove conditioning

For IFT

Deconvolve airframe spectrum

with

reference spectrum

Frequency domain

' Kaiser-Bessel window

<0.02 dB passband ripple

>50 dB rejection 0.5 ns on/off transition Frequency domain convolution

Apply distance correction

\

—Frequency domain

antenna correction

. _ Distance correction relative

to antenna-to-antenna reference

Appropriate filter to emphasize signal

1

Aircraft penetration

Figure 4. Signal processing sequence to obtain airframe penetration.
DC(J5) = 201ogio

D

aref (3)

where D is the distance in meters from the aperture of the transmitting antenna to the geometric

center of the aircraft and A-e/ is the distance between the reference antennas. A detailed

description of this procedure is given in [2]. Thus, our definition of penetration is based on a comparison of a direct antenna-to-antenna coupUng and signal transmission through the airframe.

The penetration, as we define it here, is the reciprocal of shielding (in decibels, penetration is the

negative of shielding). We prefer to display results in terms of penetration because of a better

graphical display and to normalize by our reference measurement.

Single aspect penetration characteristics for aircraft exhibit rapid variations with frequency, due

to the large, complex cavity behavior of the aircraft. In order to obtain the volumetric averaged

penetration for a compartment, the processed penetration data were frequency averaged over a

specified bandwidth, by use of the process shown in Figure 5. Averaging the penetration data

reduces the complex cavity variations, increases modal randomness, and highlights systematic

coupling effects. These effects are discussed in detail in references [2-5].

Processed

penetration data

Perform averaging over a selected

bandwidth (BW)

N /=1i

Frequency-averaged

penetration

{m/i))

Figure 5. The frequency averaging definition.
5. Reference Measurements

The test setup for the reference measurements is shown in Figure 6. The transmitting antennas

are shown mounted on one tower with aperture centers located 4 m above the ground. The

receiving antennas were mounted on the other tower. The towers were constructed from PVC

pipes and plywood platforms to produce a low-density support structure with minimal scattering.

The antennas were then boresighted and a distance extrapolation was performed to determine an

optimal reference distance to minimize near-field effects and maximize the period between the

signal and ground bounce. We performed multiple reference measurements with antenna-toantenna separations ranging from 2 m to 35 m. We found that a separation of 6 m was optimal in

terms of accuracy and time separation. Two transmission measurements were performed namely, one each for the vertical and horizontal channels. This process required a manual reorientation

of the receiving antenna to be co-polarized with each of the transmitting antennas. Once the

reference data were taken, the receiving antenna was dismounted from the support tower and

placed at selected locations inside the aircraft. The external antenna tower and aircraft are shown

in Figure 7. The reference waveforms for the DRG antenna are shown in Figures 8, 9, and 10. The reference waveforms for the TEM horn antenna are shown in Figures 11, 12, and 13. The

ungated time-domain reference waveforms are shown in Figures 8 and 1 1 . The doublets that occur at 18 ns in Figure 8 and 30 ns in Figure 1 1 correspond to the direct antenna-to-antenna

coupling. The subsequent waveform activity was due to a combination of internal antenna

Figure 6. Reference measurement setup. The transmitting tower is configured and the

receiving antennas will be mounted on top of the second tower.

10
reflections and environmental scattering due to ground bounce and reflections from nearby

objects. Figures 9 and 12 show the ungated frequency-domain responses for the DRG and TEM

horn references, respectively. The noise-like hash on the waveform is due to ground bounce and

spurious reflections which were time-gated out of the reference measurement. The frequencydomain transmission amplitude spectra of Figures 10 and 13 show the impact of applying this

time gate, thus isolating direct antenna to antenna coupling and yielding the reference for

penetration measurements.

Figure 7. The transmitting antennas placed on top of a support tower and

boresighted at the center of the aircraft.

11
0.06 -^

0.04

aU 0.02 a

<:

u

N

O

-0.02

-0.04

-0.06

10

Antenna-to-antenna response

Ground bounce

& spurious responses /

20 30

Time (ns) 40 50

Figure 8. Ungated time-domain transmission waveform for a DRG antenna

obtained at a separation of 6 m and vertical polarization.

/'" r Vmw^V'"''^'' Vf*w iW(V,-''^v-^''"^rt\«w

-40

ua

a

-80

-120

•"^•''v^*.,,.

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 9. Ungated frequency-domain amplitude spectrum for a DRG horn

anterma obtained at a separation of 6 m and vertical polarization. Note the hashy

behavior due to the spurious reflections shown in Figure 8.

12
-40

-80

-120 T r 4000 8000 12000 16000 20000

Frequency (MHz)

Figure 10. Gated frequency-domain amplitude spectrum corresponding to the

waveform of Figure 9.

0.04

u 0.02 3

s

N

o2 -0.02

-0.04

Anterma-to-antenna response

Ground bounce

& spurious responses

20 40 60

Time (ns)

Figure 1 1 . Ungated time-domain transmission waveform for a TEM antenna

obtained at a separation of 6.0 m and vertical polarization.

13
PQ3

<L> 1s

-40

-80

120

,y^y\/ -j-"-^

1000

---1 J T 2000

Frequency (MHz)

3000 4000

Figure 12. Ungated frequency-domain amplitude spectrum for a TEM horn

antenna obtained at a separation of 6.0 m and vertical polarization. Note the

scalloping due to the large ground bounce reflection shown in Figure 1 1

.

u

•T3

u -

/

I -40- i

1

i1j

00 1

1 OA iZv '

1

' 1

'

1

' 1000 2000

Frequency (MHz)

3000 4000

Figure 13. Gated frequency-domain amplitude spectrum corresponding to the

waveform of Figure 12.

14
6. Airframe Penetration Measurements—Overview

We began by measuring the penetration at several extrapolation points on the 45° line as shown

by the black X's in Figure 14. For penetration measurements, the external transmitting antennas were boresighted at the geometric center of the aircraft and moved to thirty clock positions at a

radial distance of 23 m (75 ft) as shown by the blue, dashed line in Figure 14. We applied

antenna gain and distance correction factors to maintain consistency in the results. The receiving

antenna was placed in three compartments of the aircraft: ( 1 ) the flight deck, (2) the main cabin,

and (3) the aft cargo closet. These are shown by the red X's.

X 100

270 90

180

Figure 14. Test master graphic showing internal measurement positions (red X's),

Extrapolation distances in feet (black X's), measurements around aircraft (blue,

dashed imc) at a distance of 23 m (75 ft).

15
6.1 Extrapolation Results

We performed a set of extrapolation measurements from 6.1 m (20 ft) to 30.5 m (100 ft). The

transmitting antennas were moved along the 45° line and the receiving antennas were in the main

cabin. These measurements were used to verify that we were in the far-field and to understand

how penetration changes as a fiinction of distance from the aircraft. Distance correction was

applied to the data by use of a reference distance of 6.1 m. These data are shown in Figures 15 to

18. These measurements show a spread in the data of about 5 dB to 6 dB across the frequency

spectrum for the DRG antennas and around 10 dB for the TEM horn antermas. The large spread

in the data is due mostly to the 6. 1 m and 9. 1 m distances. If we remove these data sets, we

tighten up the spread to between 2 dB and 5 dB for both sets of antennas. We believe this is because, at the closer distances, our antennas see more of the aircraft, but as we move ftirther

from the aircraft the antennas see less of the aircraft and more of the surrounding environment.

The DRG antennas have higher directivity than the TEM horn antennas, which corresponds to the greater spread in penetration data for the TEM horn antennas. These results have been both

corrected for distance and for antenna gain. A discussion of the gain for the DRG horn antenna

and TEM horn antenna is given in Appendix C.

-10

-a

5 -20

C

-30

-40

DRG-Hpol

6.1 m (20 ft)

9.1 m (30 ft) 15.2 m (50 ft) 23.5 m ( 75 ft) 30.5 m (100ft)

3000 6000 9000 12000

Frequency (MHz)

15000

I 180

Figure 15. Extrapolation measurements for the DRG antenna, horizontal polarization.

16
-10

OQ

5 -20

a

CL,

-30

-40

DRG-Vpol

6.1 m (20 ft)

9. 1 m ( 30 ft) 15.2 m (50 ft) 23.5 m ( 75 ft) 30.5 m (100ft)

3000 6000 9000 12000

Frequency (MHz)

15000 18000

Figure 16. Extrapolation measurements for the DRG antenna, vertical polarization.

-10

•aaI -20

g

-30

-40

TEM-Hpol — 6.1 m (20 ft) — 9.1 m (30 ft) — 15.2 m ( 50 ft) 23.5 m (75 ft) 30.5 m (100ft)

500 1000

Frequency (MHz)

1500 2000

Figure 1 7. Extrapolation measurements for the TEM antenna, horizontal polarization.

17
10

PQ•aco

•5 -20

-30

-40

TEM-Vpol

6.1 m (20 ft)

9.1 m (30 ft) 15.2 m (50 ft) 23.5 m ( 75 ft) 30.5 m (100ft)

500 1000

Frequency (MHz)

1500 2000

Figure 18. Extrapolation measurements for the TEM antenna, vertical polarization.

6.2 Main Passenger Cabin Penetration Results

The receiving antenna was located near the geometric center of the main cabin, as shown in

Figure 19. The antennas were placed in an area where the seats had been removed and the

antennas were mounted on tripods to provide support and separation. The antenna position was

selected to provide robust excitation of available cavity modes. The transmitting antennas were

boresighted to the geometric center of the aircraft to avoid assumptions about signal penetration

apertures.

Time-domain plots are used as an aid to understand penetration into airframes. We begin by

transforming the measured frequency domain data into the time domain to look at the signal in

time. Time-domain plots for the DRG antenna in the horizontal polarization are shown in Figure

20 at various angular positions around the aircraft. At an angular position of 0°, we have small

signal amplitude, where the signal rises to a maximum value and then decays slowly. This is indicative of reverberant field decay. As we travel around the aircraft we obtain maximum

signals between 60° and 150°. At these positions, the signal shows an initial sharp impulse,

indicative of direct antenna-to-antenna coupling; it then falls and rises to a smaller amplitude and

then decays again, showing the same reverberation characteristics as for the 0° position. We

know that the second smaller impulse is not due to ground bounce based on time-of-flight

calculations. The cause of this second impulse is a build-up of fields inside the cavity followed

by their decay. At angular positions between 170° and 190° we again observe small signal

amplitudes. This makes sense because most of the signal will couple into the main cabin
passenger windows, giving us the large initial direct coupling component seen at the beginning

of the waveform. The small signal level at the back of the aircraft is because no direct signal

path exists for the signal to get into the main passenger cabin, and at the front of the aircraft, the

signal must travel through the flight deck windows and back into the main passenger cabin. The

larger the direct coupling component, the more energy there is that initially gets coupled into the

main passenger cabin, and the less energy there is available in the reverberant field. A more in- depth discussion of this direct component versus reverberant field energy is found in Appendix

A. This analysis provides valuable insight into possible maximum coupling paths. Time-domain

plots for the DRG antenna in the vertical polarization are shown in Figure 2 1, and time-domain

plots for the TEM horn antennas in both polarizations are shown in Figures 22 and 23. The TEM

horn antennas receive lower signal levels and we do not see time-domain evidence of direct

coupling. This could be due to the low directive gain (broad radiation pattern) of the antenna.

Frequency-domain plots for various positions around the aircraft are summarized in Figure 24.

The purpose of this plot is to show how the penetration level varies at selected positions around

the aircraft. We expect the signal to drop at the front and back of the aircraft because there are no direct signal paths at these positions. We have also plotted some penetration results at various

symmetrical positions around the aircraft to determine whether there may be leakage points on

one side that are not on another. This is shown in Figure 25. We would expect a possible

leakage point at the door into the aircraft. In Figure 24, we see that the maximum penetration of

about dB occurs around 1 2000 MHz for the DRG antennas, with the transmitting antenna in

Figure 19. Receiving antenna placement in main passenger cabin.

19
the vertical and horizontal polarizations, at an angle of 30°, and the receiving antennas in the

main passenger cabin. Minimum penetration of approximately -35 dB occurs at an angle of

180° for the DRG antenna in the vertical polarization. Although not shown in either Figure 24 or Figure 25, the signal is also strong in some of the 5° positions; namely, 125° and 145°. These

positions are shown individually in Figures 26 to 53. At these particular positions there must be

some direct path available to the signal. For TEM horn antenna signals below 100 MHz, we

find that the penetration artificially increases, which is an artifact of the measurement system

rapidly losing dynamic range. This reduction in dynamic range is due to the combination of

increasing airframe shielding performance and reduced antenna efficiency.

Detailed penetration results at various azimuthal positions for all antennas and all polarizations

are summarized in Figures 26 to 53. The DRG antenna data are frequency averaged over a bandwidth of 200 MHz and the TEM horn antenna data are fi^equency averaged over a bandwidth of 50 MHz. We have concluded that these bandwidths work well at suppressing the

"hashy" behavior caused by the complex cavity modes, while emphasizing the deterministic

coupling effects. Frequency averaging is described in detail in [2-5]. We see that the penetration

is lower at the 0° position than for surrounding positions and increases as we proceed to the side

of the aircraft. The highest penetration values are seen for positions from approximately 90° to 150°. This directly correlates to the time domain data discussed previously. The horizontally

polarized antennas tend to have higher penetration values than the vertically polarized antennas

and the vertically polarized DRG antenna has very low penetration values fi^om approximately

330° to 350°. Our purpose in moving every 10° until we reach the second quadrant and then

changing to 5° increments is to investigate the possibility that we may be missing important

leakage points by only traversing every 10° [4]. What we see is that the angular variation in

penetration does not change greatly from angular position to position with typical variations less

than 5 dB. This can be attributed to a combination of complex cavity behavior and a large

number of coupling apertures distributed around the perimeter of the main cabin. Due to the

large number of coupling apertures, we do not take into account the antenna pattern effects for

either the antennas or the aircraft. If we knew exactly where the fields were penetrating into the

cavity, then these types of corrections would be feasible. These coupling paths are both

vertically and horizontally polarized, and therefore we believe the fields inside the aircraft are depolarized to a large extent.

The main conclusions for an antenna placed in the main passenger cabin are: (1) the main

coupling apertures are the windows on the side of the aircraft; (2) penetration is lowest at the

front and back of the aircraft due to lack of coupling apertures; (3) penetration into the airframe

is fairly symmetric except where the door to the aircraft is; (4) typical penetration values are dB from 90° to 140° and -30 dB for the 0° and 180° positions; and (5) horizontally polarized

energy more easily penetrates the airframe than vertically polarized energy. We believe this is because of the horizontal "slot apertures" that the array of windows provides.

20
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26
Main Cabin - degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330'

8000 12000

Frequency (MHz)

16000 20000

180-

ISC'

60'^

90^'

120''

Figure 26. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 0° position and the receiver placed in the main cabin.

sso^'

-10

§ -30

-40

-50

Main Cabin - 1 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180°

GO--'

90'

120°

I-SO-^

Figure 27. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 0° position and the receiver placed in the main cabin.

27
-20 co

nt

<u -^0

CL,

-40

Main Cabin - 20 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

150°

60*

90*

120°

180=

-50

4000 8000 12000 16000 20000

Frequency (MHz)

Figure 28. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 20° position and the receiver placed in the main cabin.

Main Cabin - 30 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330

60^

90°

120°

-40

-50

4000 8000 12000 16000 20000

Frequency (MHz)

180=

150°

Figure 29. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 30° position and the receiver placed in the main cabin.

28
0°

-40

-50

Main Cabin - 40 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

330°

16000 20000

ISC'

30-

l.W

60"

90°

120°

Figure 30. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 40° position and the receiver placed in the main cabin.

0-

-40

Main Cabin - 50 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330°

0°

30-

60^

90*

120°

150^

180°

-50

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 3 1 . Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 50° position and the receiver placed in the main cabin.

29
0^

-10

^ -20

-30

-40

-50

Main Cabin - 70 degrees

TEM - Hpoi

DRG - Hpol

TEM - Vpol

DRG - Vpol

SSC

4000 8000 12000

Frequency (MHz)

16000 20000

180-

30"

120*

150''

Figure 32. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 70° position and the receiver placed in the main cabin.

10

-30

-40-

-50

Main Cabin - 80 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000

\

' \ 8000 12000

Frequency (MHz)

16000 20000

330°

180=

30^

60*

90*

120°

\50°

Figure 33. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 80° position and the receiver placed in the main cabin.

30
O^'

-50

Main Cabin - 90 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330'"

~1 ^

\

'

I

'

'

^ 4000 8000 12000 16000 20000

Frequency (MHz)

180°

w150"

Figure 34. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 90° position and the receiver placed in the main cabin.

-40

-50

Main Cabin - 100 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330°

4000 8000 12000

Frequency (MHz)

16000 20000

180'

W150°

120°

Figure 35. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 100° position and the receiver placed in the main cabin.

31
-10

CQ -20 a

o

mbajc

<L) -10

Ah

-40

-50

O--'

Main Cabin - 1 1 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

"H ^\

'

\

'

\

' I 4000 8000 12000 16000 20000

Frequency (MHz)

SSO"

180^

30°

150-=

120**

Figure 36. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 10° position and the receiver placed in the main cabin.

0°

-10

-30

-40

-50

Main Cabin - 120 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

330°

1 SOSO"

150°

60'

90°

I :()

Figure 37. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 120° position and the receiver placed in the main cabin.

32
-40

-50

Main Cabin - 1 25 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

3 BO"

4000 8000 12000

Frequency (MHz)

16000 20000

180"

30°

1 50'^

60"^

90°

120"

Figure 38. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 125° position and the receiver placed in the main cabin.

10

-10 m

c1-20

-30

-40

Main Cabin - 130 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330° 30"

150°

60°

90"

120°

180°

-50

4000 8000 12000 Frequency (MHz)16000 20000

Figure 39. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 130° position and the receiver placed in the main cabin.

33
-10

-30

-40

Main Cabin - 135 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330' 30°

150°

60°

90°

120-

180^

-50 4000 8000 12000

Frequency (MHz)

16000 20000

Figure 40. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 135° position and the receiver placed in the main cabin.

10

530°

0° 30*

-10

CQ

1-20

-30

-40

Main Cabin - 140 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

ISOISO"

60°

90°

IZO"

-50

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 41. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 140° position and the receiver placed in the main cabin.

34
-50

330'='

Main Cabin - 145 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000 16000 20000

Frequency (MHz)

180^

30°

150°

60°

90°

120°

Figure 42. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 145° position and the receiver placed in the main cabin.

~, 330^

0° 30°

-10

^ -20-

c

o

n)

OJC

-30

-40

-50

Main Cabin - 1 50 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

60-

180°

90°

120°

Figure 43. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 50° position and the receiver placed in the main cabin.

35
-40

-50

Main Cabin - 1 60 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

0"^- 330°

180"

30°

150^

60-

90°

120°

4000 8000 12000 16000 20000

Frequency (MHz)

Figure 44. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 160° position and the receiver placed in the main cabin.

-10

-30

-40

-50

0° Main Cabin - 1 70 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

330°

180-

^0

150°

60°

90°

120°

Figure 45. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 70° position and the receiver placed in the main cabin.

36
330° 30''

-10

^ -20

-40 ^

Main Cabin - 1 80 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

60^

90°

120-

-50

i

^

I r r

^

I

^

I 4000 8000 12000 16000 20000

Frequency (MHz)

Figure 46. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 80° position and the receiver placed in the main cabin.

-10

-40

Main Cabin - 190 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330° 30'"

60-

90'^

120°

150°

-50

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 47. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 90° position and the receiver placed in the main cabin.

37
-40

-50

Main Cabin - 330 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330'

180"

TiO"

ISO'^'

60°

90"

120*

4000 8000 12000 16000 20000

Frequency (MHz)

Figure 48. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 330° position and the receiver placed in the main cabin.

-10

-30

-40

-50

Main Cabin - 335 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180

30'

60*

90°

120*

150°

Figure 49. Penetration versus frequency for all antermas and polarizations for the transmitting

tower placed at the 335° position and the receiver placed in the main cabin.

38
330

-10 H

-40

Main Cabin - 340 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

30'='

150-=

60°

90°

120^

180^

-50

4000 8000 12000 Frequency (MHz)16000 20000

Figure 50. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 340° position and the receiver placed in the main cabin.

-10

3-20

c

o

S -30

cu

-40

Main Cabin - 345 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330

60°

90°

120°

l.'^O"

180=

-50

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 5 1 . Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 345° position and the receiver placed in the main cabin.

39
Main Cabin - 350 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330'

180*

60"^

90°

120'='

150'^

-50 4000 8000 12000

Frequency (MHz)

16000 20000

Figure 52. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 350° position and the receiver placed in the main cabin.

Main Cabin - 355 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330

60^

90*

120^

150°

180°

-50

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 53. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 355° position and the receiver placed in the main cabin.

40
6.3 Flight Deck Penetration Results

The second penetration study was performed with the receiving antennas placed in the flight

deck between the pilot's and the co-pilot's seats, as shown in Figure 54. The time-domain plots

for various angular positions around the aircraft are shown in Figure 55. Only the horizontal

polarization is shown for the DRG antennas, and we notice that no significant direct coupling

components are visible for any position. Therefore, maximum penetration results are lower than

for positions in the main cabin, where direct coupling is seen in the time-domain plots. Figure

56 shows penetration data for various positions around the aircraft. Maximum penetration of

approximately - 1 5 dB occurs around the nose position for the vertical polarization, but decays

rapidly for the horizontal position at 0° and at frequencies above 2000 MHz. Minimum

penetration of -45 dB occurs at the 190° position for both polarizations. Symmetry around the

aircraft is shown in Figure 57. Figures 58 to 86 show detailed penetration data for each

individual external position around the aircraft.

Figure 54. The receiving DRG and TEM antennas placed between the pilot and co-pilot

seat as shown in these two photos.

41
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42
xtc

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44
Flight Deck - degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330

180^

4000 8000 12000

Frequency (MHz)

16000 20000

150°

6(y>

90*

120'^'

Figure 58. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 0° position and the receiver placed in the flight deck.

-10

^ -20

-30

-40

-50

Flight Deck - 10 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330"^

180*

4000 8000 12000

Frequency (MHz)

16000 20000

6(P

90*^

120^'

150"

Figure 59. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 0° position and the receiver placed in the flight deck.

45
-10

§ -30

-40

-50

Flight Deck - 20 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180^

150"

60'

90*

120°

Figure 60. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 20° position and the receiver placed in the flight deck.

-10

-30

-40

-50

Flight Deck - 30 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

??0'

0°

180^

30°

60-

90°

120°

150°

4000 8000 12000 16000 20000

Frequency (MHz)

Figure 6 1 . Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 30° position and the receiver placed in the flight deck.

46
330° 30"

-10

Flight Deck - 40 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

ISC'

150°

60-

90^

120

Figure 62. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 40° position and the receiver placed in the flight deck.

530° 30"

Flight Deck - 50 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180"

60-

90-

120^

150°

Figure 63. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 50° position and the receiver placed in the flight deck.

47
Flight Deck - 70 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330"

8000 12000

Frequency (MHz)

16000 20000

180^

30'

150°

120°

Figure 64. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 70° position and the receiver placed in the flight deck.

Flight Deck - 80 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

30°

8000 12000

Frequency (MHz)

16000 20000

180°

150°

120°

Figure 65. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 80° position and the receiver placed in the flight deck.

48
0° 33Cr 30°

-10

Flight Deck - 90 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

A

ISC^

150°

60°

90^

120^

Figure 66. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 90° position and the receiver placed in the flight deck.

.^30'^' 30°

-10

Flight Deck - 1 00 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180°

1.50°

120°

Figure 67. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 00° position and the receiver placed in the flight deck.

49
0°

Flight Deck - 1 10 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

530'

8000 12000

Frequency (MHz)

16000 20000

ISO30^-

60"

90°

120°

150°

Figure 68. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 10° position and the receiver placed in the flight deck.

Flight Deck - 120 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000 16000 20000

Frequency (MHz)

??0

180-

30'-"

150^'

60°

90°

120"

Figure 69. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 120° position and the receiver placed in the flight deck.

50
0° 330 30'"-'

-10

g-20

c

oI

-30

-40

-50

Flight Deck - 125 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180^

150°

60'

90-

120

Figure 70. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 125° position and the receiver placed in the flight deck.

3.30° 30^

10

Flight Deck - 130 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000 16000 20000

Frequency (MHz)

180°

60^

90"

120

150°

Figure 7 1 . Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 130° position and the receiver placed in the flight deck.

51
330° 30*

-10

Flight Deck - 135 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180-

150°

60^

90°

120"

Figure 72. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 135 ° position and the receiver placed in the flight deck.

330° 30^

-10

Flight Deck - 140 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180=

150°

60"

90°

1 20-

Figure 73. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 140° position and the receiver placed in the flight deck.

52
330" 30'

-10

Flight Deck - 145 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000 16000 20000

Frequency (MHz)

180°

150°

60°

90^

1 20°

Figure 74. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 145° position and the receiver placed in the flight deck.

-

1

-10 J

0°

Flight Deck - 1 50 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

W

4000 8000 12000

Frequency (MHz)

16000 20000

180°

30°

60°

90-

12(1

150°

Figure 75. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 50° position and the receiver placed in the flight deck.

53
-10

330''

Flight Deck - 1 60 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180"

30"-^

150°

60°

90-^

120°

Figure 76. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 160° position and the receiver placed in the flight deck.

-10

0°

Flight Deck - 1 70 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

330°

180^

30^

60f

90*

120°

Figure 77. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 170° position and the receiver placed in the flight deck.

54
330'^ 30°

-10

Flight Deck - 1 80 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

150°

60°

90-

1 20

Figure 78. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 180° position and the receiver placed in the flight deck.

530"

0° 30°

-10

-40

-50

Flight Deck - 1 90 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

60°

90-

120°

150°

Figure 79. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 190° position and the receiver placed in the flight deck.

55
330" 30^

-10

-30

-40

-50

Flight Deck - 270 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

^

^

180»

150°

60-

90°

120°

Figure 80. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 270° position and the receiver placed in the flight deck.

Flight Deck - 330 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330

4000 8000 12000

Frequency (MHz)

16000 20000

180^

6<y>

90°

120°

150°

Figure 8 1 . Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 330° position and the receiver placed in the flight deck.

56
-40

-50 -1^

Flight Deck - 335 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

G - Vpol

180='

150°

60'

90'

i:(t

4000 8000 12000 16000 20000

Frequency (MHz)

Figure 82. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 335° position and the receiver placed in the flight deck.

-40

Flight Deck - 340 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330°

150°

60''

90'

120

180°

-50

4000 8000 12000 Frequency (MHz)

16000 20000

Figure 83. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 340° position and the receiver placed in the flight deck.

57
-10

-40

-50

Flight Deck - 345 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

,

330'

180=

8000 12000

Frequency (MHz)

16000 20000

150°

60^

90°

120°

Figure 84. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 345° position and the receiver placed in the flight deck.

10

Flight Deck - 350 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

3.30'

4000 8000 12000

Frequency (MHz)

16000 20000

180=

60^'

90°

120°

150°

Figure 85. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 350° position and the receiver placed in the flight deck.

58
•a

-40

330"

Flight Deck - 355 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

180'

150"

60^

90*

1 20'-

-50 4000 8000 12000

Frequency (MHz)

16000 20000

Figure 86. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 355° position and the receiver placed in the flight deck.

59
6.4 Cargo Closet Penetration Results

A series of penetration measurements were taken with the receiving antennas placed in the cargo

closet located at the rear of the main passenger cabin. The receiving antenna positions for the

TEM horn antennas and DRG antennas are shown in Figure 87.

Figure 88 shows the time-domain plots for the DRG antenna in the horizontal polarization for

various positions around the aircraft. We see no direct antenna-to-antenna coupling in these

plots due to the lack of any direct coupling paths from the outside of the aircraft into the cargo

closet. Because there is no hardened door for this compartment we do expect to see more

penetration than for typical cargo bays found on commercial aircraft. The frequency-domain

plots corresponding to these same time-domain plots are shown in Figure 89. A pronounced

resonance peak in penetration is seen in the neighborhood of 600 MHz for vertically polarized

antenna positions of the TEM horn antenna for the 60° position to the 180° position. The

horizontally polarized antennas generally show greater penetration as we move around the

aircraft. Maximum penetration of around -15 dB occurs at the 30°, 60°, 330°, and 350°

positions at the lower frequencies, and approximately -20 dB at these same positions at the

higher frequencies. Minimum penetration occurs for the vertically polarized antennas at the 0°,

180°, and 350° positions of approximately -30 dB for the lower frequencies, and approximately

-45 dB at the middle frequencies. Symmetry plots are shown in Figure 90. Penetration tends to be symmetrical with the receiving antenna in the cargo closet, although the vertical polarization

has approximately 5 dB less penetration than horizontal polarization. Detailed penetration data

for every external angle are shown in Figures 91 to 120.

f

Figure 87. TEM and DRG antenna placement in the cargo closet.

60
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63
1

Cargo Closet - degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180'

150^

60'

90°

120°

Figure 9 1 . Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 0° position and the receiving antennas placed in the cargo closet.

Cargo Closet - 10 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

330°

180°

150°

60-

90°

120°

Figure 92. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 10° position and the receiving antennas placed in the cargo closet.

64
Cargo Closet - 20 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330

8000 12000

Frequency (MHz)

16000 20000

ISC^

150°

eO'^'

90*

120°

Figure 93. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 20° position and the receiving antennas placed in the cargo closet.

Cargo Closet - 30 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

330"

150°

180°

60°

90°

120'"

Figure 94. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 30° position and the receiving antennas placed in the cargo closet.

65
0°

530° Cargo Closet - 40 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180^

30^'

150°

60*

90"

120°

Figure 95. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 40° position and the receiving antennas placed in the cargo closet.

Cargo Closet - 50 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

>30° 30'-"'

8000 12000

Frequency (MHz)

16000 20000

180-

150°

60°

90'

120°

Figure 96. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 50° position and the receiving antennas placed in the cargo closet.

66

'
0°

-10

-30

-40

Cargo Closet - 60 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330°

180°

30°

150°

120^^^

-50

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 97. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 60° position and the receiving antennas placed in the cargo closet.

0°

10

03 -20 co

(fl

a> -30

-40

-50

Cargo Closet - 70 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330'

4000 8000 12000

Frequency (MHz)

16000 20000

30^'

150°

180°

120'

Figure 98. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 70° position and the receiving antennas in the cargo closet.

67
-40

-50

Cargo Closet - 80 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

0° 330°

4000 8000 12000

Frequency (MHz)

16000 20000

180*

30^

150"

Figure 99. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 80° position and the receiving antennas placed in the cargo closet.

Cargo Closet - 90 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

530°

8000 12000

Frequency (MHz)

16000 20000

180°

30^

1.^0°

120°

Figure 1 00. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 90° position and the receiving antennas placed in the cargo closet.

68
0° 330

Cargo Closet - 100 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

-40

-50

\

'

i

'

\

'

\

'

! 4000 8000 12000 16000 20000

Frequency (MHz)

ISC'

30°

150°

60°

90-

120^^

Figure 101 . Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 100° position and the receiving antennas placed in the cargo closet.

30°

-10

-30

-40

-50

Cargo Closet - 1 1 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180°

150°

Figure 102. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 10° position and the receiving antennas placed in the cargo closet.

69
330'=' wCargo Closet - 1 20 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000 16000 20000

Frequency (MHz)

180^

150°

60'=

90°

120"

Figure 103. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 120° position and the receiving antennas placed in the cargo closet.

-40

-50

330°

Cargo Closet - 125 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

0°

180'^

30"

150°

60°

90°

1 20°

4000 8000 12000 16000 20000

Frequency (MHz)

Figure 104. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 125° position and the receiving antennas placed in the cargo closet.

70
330 30^

Cargo Closet - 130 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000 16000 20000

Frequency (MHz)

ISO*

150°

60°

90'

120°

Figure 105. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 130° position and the receiving antennas placed in the cargo closet.

0°

-10

-40

-50 4000

Cargo Closet - 135 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180"

30°

150°

60°

90"

20'

Figure 106. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 135° position and the receiving antennas placed in the cargo closet.

71
Cargo Closet - 140 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

530°

8000 12000 16000 20000

Frequency (MHz)

180^

30-

150°

60^

90°

120°

Figure 107. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 140° position and the receiving antennas placed in the cargo closet.

Cargo Closet - 145 degrees

TEM - Hpol — DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000 16000 20000

Frequency (MHz)

330°

180^

30"

150°

60-

go'-

120°

Figure 108. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 145° position and the receiving antennas placed in the cargo closet.

72
^30 30°

-10

3

-2^ coI

S -30

-40 -

-50

Cargo Closet - 1 50 degrees

TEM - Hpol — DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180°

150°

60°

90'-

120

Figure 109. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 150° position and the receiving antennas placed in the cargo closet.

0°

Cargo Closet - 1 60 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

330'

180°

30°

60°

90°

120'^'

150°

Figure 1 1 0. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 60° position and the receiving antennas placed in the cargo closet.

73
Cargo Closet - 1 70 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

0° 330°

4000 8000 12000 16000 20000

Frequency (MHz)

180-

30'

60'^

90°

120°

Figure 111. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 70° position and the receiving antennas placed in the cargo closet.

Cargo Closet - 1 80 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

330° 30"

8000 12000

Frequency (MHz)

16000 20000

60-

90°

120°

Figure 1 12. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 1 80° position and the receiving antennas placed in the cargo closet.

74
0"

-10

330^

Cargo Closet - 190 degrees

TEM - Hpoi

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180°

30°

60°

90^^

1 20

Figure 113. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 190° position and the receiving antennas placed in the cargo closet.

0°

3.30'

Cargo Closet - 270 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

180°

30°

150°

60°

90'^

120°

Figure 1 14. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 270° position and the receiving antennas placed in the cargo closet.

75
0^ 330° 30=

Cargo Closet - 330 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180=

150'^

60'

90«

120°

Figure 115. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 330° position and the receiving antennas placed in the cargo closet.

Cargo Closet - 335 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

30-

ISOISO"

60'

90°

120°

Figure 1 16. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 335° position and the receiving antennas placed in the cargo closet.

76
0°

10

330

Cargo Closet - 340 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180^

30'

150°

60*

90'

noFigure 117. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 340° position and the receiving antennas placed in the cargo closet.

-10

-30

-40

-50

Cargo Closet - 345 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000 Frequency (MHz)

16000 20000

180*

150°

60-

90^

120'=

Figure 1 1 8. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 345° position and the receiving antennas placed in the cargo closet.

77
-10

Cargo Closet - 350 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

180"

60*

90°

120"

150°

Figure 1 19. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 350° position and the receiving antennas placed in the cargo closet.

Cargo Closet - 355 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000

Frequency (MHz)

16000 20000

330

180-

l.SO"

6(y>

90°

120°

Figure 120. Penetration versus frequency for all antennas and polarizations for the transmitting

tower placed at the 355° position and the receiving antennas placed in the cargo closet.

78
6.5 HIRF Positions for Flight Deck Penetration

These tests are standard measurements taken for HIRF evaluation of airframe shielding and

vulnerability, as discussed in [1]. Five measurements were taken around the flight deck of the

aircraft to investigate shielding vulnerabilities. In our measurements, we offset the transmitting

antenna approximately 1 5 m from the front wheel of the aircraft. There is no required offset

from the flight deck windows for testmg but there are requirements for angular positions. These

are at 270°, 315°, 0°, 45°, and 90° around the flight deck windows. Figure 121 shows a diagram

of these measurement positions and their associated graphs. At positions 270° and 3 15° we see a sharp penetration resonance at approximately 2000 MHz for the DRG antenna in the vertical

polarization. We see that the penetration has a maximum value of approximately -25 dB at around 2000 MHz for the vertical polarization and around 3000 MHz for the horizontal

polarization. The minimum penetration values that occur at the higher frequencies are approximately -30 dB to -35 dB. For angles 0°, 45°, and 90° we do not see the sharp resonance

for the DRG antenna in the vertical polarization. These positions have lower penetrations of

approximately -30 dB at the lower frequencies and -30 to -40 dB at the higher frequencies.

Detailed HIRF penetration data are given in Figure 122 to 126.

79
t/3 c

4—

o

Oh

c

a>

-t->

o

B

C3

U(

CO) ca

^-1 Q

(N

3

DC •1—

(

(gp) uoiiEjpuoj

(ap) uoquJiouoj

80
c

o

HIRF flight deck - 270 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

8000 12000 Frequency (MHz)16000 20000

270

Figure 122. HIRF penetration data versus frequency for all antennas and polarizations for the

transmitting tower placed at the 270° position, at a distance of 15 m centered on the front landing

gear, and the receiving antennas placed in the flight deck.

'1

1

-40

-50

HIRF flight deck - 3 1 5 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 123. HIRF penetration data versus frequency for all antennas and polarizations for the

transmitting tower placed at the 315° position, at a distance of 15 m centered on the front landing

gear, and the receiving antennas placed in the flight deck.

81
HIRF flight deck - degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

270 X

8000 12000

Frequency (MHz)

16000 20000

Figure 124. HIRF penetration data versus frequency for all antennas and polarizations for the

transmitting tower placed at the 0° position, at a distance of 1 5 m centered on the front landing

gear, and the receiving antennas placed in the flight deck.

0-n

-10-

-30

-40

-50

HIRF flight deck - 45 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

-^ ^

\

^

^

4000 8000 12000

Frequency (MHz)

16000 20000

270 ic

Figure 125. HIRF penetration data versus frequency for all antennas and polarizations for the

transmitting tower placed at the 45° position, at a distance of 15 m centered on the front landing

gear, and the receiving antennas placed in the flight deck.

82
-10

HIRF flight deck - 90 degrees

TEM - Hpol

DRG - Hpol

TEM - Vpol

DRG - Vpol

270 X

8000 12000

Frequency (MHz)

16000 20000

Figure 126. HIRF penetration data versus frequency for all antennas and polarizations for the

transmitting tower placed at the 90 degree position, at a distance of 15 m centered on the front landing gear, and the receiving antennas placed in the flight deck.

83
6.6 Internal Coupling Measurements

Internal coupling measurements can tell us a lot about the propagation environment within the

airframe. It can tell us whether fields are uniform and decay at a rapid rate or more slowly over

time. It can also tell us how well the fields propagate within the airframe and whether they can

easily reach critical components inside the airframe.

NIST conducted several internal coupling measurements to determine the decay time and the

quality factor of the internal airframe volume. We looked at the reverberant environment and

how the fields couple from one cavity to another. Each configuration is shown in Figures 127 to

132. The chosen configurations were meant to physically stir the fields inside the aircraft as much as possible. In each configuration, the red rectangle represents the fransmitting 1 .2 m

TEM horn antenna, the blue rectangle represents the receiving 36 cm TEM horn antenna, and the

other two antennas are the transmitting DRG antenna (red), and the receiving DRG antenna

(blue). The arrows indicate the aperture of the antenna.

Configuration 1

Antennas [^RxTEM

iTxTEM ^ Rx DRH

C;;Tx DRH

Figure 127. Layout for Configuration 1 measurements: coupling from main passenger cabin

to cargo closet.

84
Configuration 2

Antennas l^RxTEM

Tx TEM

C^RxDRH

(^Tx DRH

Figure 128. Layout for Configuration 2 measurements: coupling from main passenger cabin

to cargo closet.

Configuration 3

Figure 129. Layout for Configuration 3 measurements: coupling from main passenger cabin

to flight deck.

85
Configuration 4

Antennas

I^RxTEM

TxTEM ^ Rx DRH

(^TxDRH

Figure 130. Layout for Configuration 4 measurements: coupling from forward main

passenger cabin to aft main passenger cabin.

Configuration 5

Antennas

I^RxTEM

I Tx TEM

Rx DRH

C^TxDRH

Figure 131. Layout for Configuration 5 measurements: coupling from forward main

passenger cabin to mid main passenger cabin:

86
Configuration 6

Antennas

[^Rx TEM

TxTEM ^ Rx DRH

^Tx DRH

Figure 132. Layout for Configuration 6 measurements: coupling from forward main

passenger cabin to mid main passenger cabin.

We began by looking at the time decay and quality factor of the airframe for each set of antennas

in each configuration. These data are shown in Figures 133 to 136. At approximately 8 GHz,

the time decay for the DRG antennas in Figure 133 shows a rapid departure from the clustering

behavior. Below 8 GHz, the variation in time decay is anywhere from 2 ns to approximately 7

ns. The variation above 8 GHz is from 7 ns to 10 ns. There is no discemable pattern behavior as a function of position. The variation in time decay for the TEM horn antennas is on the order of

2 ns to approximately 7 ns. The trend shows tighter clustering for the DRG antennas at the lower

frequencies and for the TEM antennas in the higher frequency range. Because of the lower

frequency range, the quality factor is much lower for the TEM horn antennas. Figures 137 and

138 are plots showing the combined quality factor for both antennas for Configuration 1 and

Configuration 6. The two antennas types show good agreement across their common frequency

band from 1 to 2 GHz. In a reverberant cavity, we expect the quality factor and time decay to vary little throughout the cavity. However, further statistical analysis would have to be

completed in order to determine that the cavity was not reverberant.

87
60

50

40

solo

10

Internal Measurements

Configuration 1 n D n Configuration 2

Configuration 3 A A A Configuration 4 X X X Configuration 5

1^ ^ "iV Configuration 6

4000 8000

Frequency (MHz)

o

X

12000 16000

Figure 133. Time decay for DRG antennas in all six internal configurations.

2000

1600

.: 1200 a

3 800

O

400

O

o

o

X

n

Internal Measurements O

D

O

A

X

O

D

O

A

X

O Configuration 1 D Configuration 2 O Configuration 3 A Configuration 4 X Configuration 5

"i^ Configuration 6

4000 8000

Frequency (MHz)

12000 16000

Figure 1 34. Airframe quality factor (Q) for DRG antennas in all six internal configurations.

88
60-

- ©

50

40

30

20

X

X

Internal Measurements O Configuration 1 D a D Configuration 2 Configuration 3 A A A Configuration 4 X X X Configuration 5 ^ ^ 1^ Configuration 6

10 400 800 1200 1600 2000

Frequency (MHz)

Figure 135. Time decay for TEM horn antennas in all six internal configurations.

2400

400

^

300

a

u^ 200

Internal Measurements

100

o

D

O

A

X

1^

o

n

o

A

X

O Configuration 1 D Configuration 2 O Configuration 3 A Configuration 4 X Configuration 5

"i^ Configuration 6

400 800 1200

Frequency (MHz)

1600 2000 2400

Figure 136. Airframe quality factor (Q) for TEM horn antennas in all six internal configurations.

I

89
1800

1600

1400

1 200

5 1000

C3 U.

>• =1 800 o

600

400

200

Internal Mcasurcmcnls ( DRCi & TI-M i O O O Conl'igurjlion I

o

o

^o

<>

.o^ oo

O

4000 8000 12000

Frcquenc) (MH/)

Figure 137. Quality factor for both antennas for Configuration 1

.

1 800

I AQn I nicrnal Mcasuremcnls ( DRG & TEM

)

O O O Configuralion 6

1400

1200 O

o

2 1000

1 800 5

O

600 O

o 400

200 .O

,ooo^*

o

4000 8000 12000

I-'rcqucncv (MH/)

Figure 138. Quality factor for both antennas for Configuration 6.

90
7. Uncertainty Analysis

The sources of uncertainty are based on NISTIR 5019 [6] which provides a natural framework

for the identification of source uncertainties encountered in aircraft shielding measurements,

along with an efficient method for tracking and combining them.

Six sources of measurement uncertainty are considered in our analysis:

Measurement Repeatability

Range Uncertainties/Distance Correction

Time Gating

Drift

Polarization Mismatch

Signal-to-Noise Ratio

These sources of uncertainties (influence factors) were evaluated as follows:

1. Measurement Repeatability: For a given internal orientation, we took multiple data sets, in

which we moved the external antennas to and from the same location.

2. Range Uncertainties: We used estimates of variations when positioning the antennas for both

the reference and airframe measurements.

3. Time Gating: We determined time-gating uncertainties by varying the gate width and

performing a statistical analysis on the resulting amplitude specfra. See Appendix A for further

discussion.

4. Drift: The uncertainty due to instrumentation drift was small and was computed by using the

data obtained from system calibration checks done before and after circumnavigating the aircraft. The uncertainty was determined by looking at the difference and dividing that by the average of

the two signals.

5. Polarization Mismatch: Polarization mismatch uncertainties occur because antennas could be

misaligned for a given polarization. We calculated one uncertainty based on a possible

misalignment of 5°. The other term comes from the possible leakage from one polarization to the other. The cross-polarization of our TEM horn antennas is approximately -20 dB, and for the

DRG antennas it is approximately -15 dB. These two factors both contribute to the polarization

mismatch uncertainty.

6. Signal-to-Noise Ratio: These uncertainties were calculated for the Global 5000 aircraft. Appendix B of this report summarizes typical signal and noise characteristics.

The impact of these six influence factors on the measured penetration is summarized in Table 1. This table lists the fractional uncertainties [7,8] resulting from each influence factor. The most

91
significant error is due to signal-to-noise uncertainties. Measurement repeatability has an

influence that is somewhat less than the signal-to-noise ratio, but is nevertheless significant.

Time gating is the next largest uncertainty, followed by the range/distance correction

uncertainties, extrapolation uncertainties, polarization mismatch, and drift, respectively.

Polarization mismatch and drift contribute almost nothing to the overall uncertainty.

The combined standard uncertainty was computed using the procedure given in NIST Technical

Note 1297 [8]. The six sources of uncertainties were combined using the root sum-of-squares of

the linear fractional uncertainties averaged over a 200 MHz frequency window. The resulting

uncertainties (in decibels) for penetration are plotted in Figure 139 for the frequency range from

800 MHz to 1500 MHz. The uncertainties were calculated as a function of frequency, and

therefore, we have listed an approximate average value in the table below. We have broken the

uncertainties into those below 9 GHz and those above 9 GHz because the noise floor resets itself

there due the internal configuration of both attenuators and mixers. We believe that a reasonable

uncertainty bound would be at the 95 % level for the data shown in Figure 139, remembering

that this current uncertainty analysis is based on a limited set of data.

Table 1 . Typical fractional uncertainties resulting from the six influence factors

Influence factor

Typical fractional uncertainties (dB)

<9GHz >9GHz

Signal-to-noise 1.00 1.20

Repeatability 0.60 0.80

Time gating 0.03 0.20

Range/distance correction 0.28 0.28

Extrapolation 0.15 0.40

Polarization mismatch 0.06 0.06

Drift 0.01 0.01

RSS 1.82 4.06

92
6^

c

'3t 4 u

n

VI

Pi

[' 4000 8000 12000

Frequency (MHz)

16000 20000

Figure 139. Combined standard uncertainty in penetration.

8. Summary and Conclusions

The data collected in this report will be used to provide guidelines for HIRP testing on various

aircraft. We have reported on the penetration measurements taken on the Bombardier Global

5000 at the FAA facility in Atlantic City, New Jersey. We have discussed extrapolation

measurements taken to ensure that the measurements are in the far- field of the transmitting

antenna. We have shown results for measurements taken at various azimuth angles around the

outside of the aircraft with the receiving antenna in the main passenger cabin, the flight deck, and

the cargo closet. We have also performed a series of internal measurements to look at the

reverberant field characteristics within the cavity to determine the viable statistics associated

with the fields.

The main passenger cabin shows the greatest penetration for all three compartments. We

attribute this to the numerous windows. Typical maximum penetration values are dB and

appear at angles between 90° and 150°. Minimum penetration values occur at the front and rear of the aircraft and are on the order of -40 dB. Flight deck maximum penetration is around -15

dB, occurring around 45°, and minimum penetration values are around -45 dB, occurring at 190°. Cargo closet penetration values are similar to the flight deck numbers. Maximum

penetration values occur at 30°, 60°, and 330°, while minimum penetration occurs at 0°, 180°,

93
and 350°. We also found that the horizontal polarization has higher penetration values than the

vertical polarization, and that symmetry is maintained around the aircraft until we get to the main

passenger door, and then values increase slightly. HIRF penetration into the flight deck shows

approximate values of -20 dB at lower frequencies and -25 dB at higher frequencies for a radial

distance of 15 m fi^om the front landing gear at angles of 270°, 315°, 0°, 45°, and 90°. The

internal coupling measurements showed that traditional reverberation statistics would not be

valid in this cavity, but good agreement was shown between the two antenna types for quality

factor values between 1 GHz and 2 GHz. Finally, we found that major coupling apertures would

not be missed if measurements were taken every 10° as opposed to every 5°. Figure 140 shows

penetration data measured with the DRG horn antenna in both the vertical and horizontal

polarizations for various frequencies in each compartment. Figure 141 shows penetration data

measured with the TEM horn antenna in both the vertical and horizontal polarizations for various

frequencies in each compartment. Red circles are in the main cabin, blue triangles are in the

flight deck, and green squares are in the cargo closet. This shows us that flight deck penetration

is typically lower than for the cargo closet at each of these frequencies. And we see that

penetration typically decreases as frequency increases. This was an important measurement

effort both to aid in understanding and to help define standard measurement procedures for HIRF

testing.

94
800 MHz

1000 MHz

5000 MHz

I

10000 MHz

I

18000 MHz

SOO MH? • • •Mniii Cabin

Fhghi DLLk 320

CaTtuClo!>Ll

UIO

DRG-Hpol

50 H)o, 3(r"f j«^J=io^Jo .:^

./ / ,20

DRUHpol

lUUOMHz • • • M3in Cabin

FlighC Deck 320 Cargo Closet

„ k''

DRG Hpol

soon MH7

I • Main Cdbin

Flight Deck ^20

I Cargo Closet ^

"'

300 -. /

DRG Hpol

10000 MH7 • • • Main Cabni

Flislll Deck

Cargo C lONcI •••:^l'-''<•.

3:r-^tf^ .;So, -to Jib~'.20-,iu_|o

ORG Hpol

IKOOOMIIi! • • • Main Cabin

Kligln Dark 320 Cargo C losct

DRG Vpol 800 MH7. • Main Cabin » FlighlDcck

I Cargo Closet

300 /

DRG-Vpol

•^-*l^^-<-'

:l7€><'^y\

DRG Vpol

1000 MHz # 9 Main Cabin

Flight Deck 320

Cargo Closet

^\ ^K /-^c--^ *-•-

DRG Vpol 5000 MHz • • Main Cabin

Flight Deck

Cargo Cloiict

300

I -T-—/_ -; "",<.* !/^--' '.-? Am—*-

DRG Vpol IOOOOMH2 • • Main Cab

Fligh D ck Cargo Close!

DRG Vpol I8OOOMH7 # # Main Cab

Flight Deck - Cargo Closet

300 v*n^

^i2^)(^

40

3(r7-4(Mjo_Jo

./.•^

Figure 140. Penetration data as a function of angular position for DRG horn antenna in both vertical

and horizontal polarizations for various frequencies in each compartment. Red circles (•) are in the

main cabin, blue diamonds () are in the flight deck, and green squares (U) are in the cargo closet.

95
TEM-Hpol TEM-Vpol

TEM Hpol 800 MHz • • • Main Cabin

Flight Deck

Cargo Closet

300

280 -'

340 20

^'^w:. 60

TEM Vpol 800 MHz • • • Main Cabin

Flight Deck ^^0 Cargo Closet /

300

800 MHz 260

-r. Hir

240

50, ^0 -3(f -20^0

-; - - . ^ ..

' " 100 260

120

00

120

140

200

TEM Hpol

1000 MHz # # # Main Cabin

Flight Deck 320

Cargo Closet

300

180

160

20

••V

40 l%4 • >

' 4

60

220

TEM Vpol

1000 MHz 9 # Main Cabin

Flight Deck 320

Cargo Closet

300

140

200

340

180

^^»,

1000 MHz

280 ~)

260

-SO -40 /

.

3B»r-2fl~ilO /O 100 260

rP'^

220

TEM Hpol

3000 MHz # # # Main Cabin

Flight Deck 320

Cargo Closet

300

••y

140 220

20

40

rSO -40 JD^-»jaO /O z.«.

140

180

3000 MHz

280 ~'

260

J&.

240

220

200

40

TEM Vpol 3000 MHz V C # Main Cabin

Flight Deck

340

320

sa^o ^!P^=2fl-Jdo_jO

I Cargo Closet

300

280 -J •^1-^%

f

100

i 260

-"

120 240

220

180

160 200

Figure 141. Penetration as a function of angular position for TEM horn antenna in both

vertical and horizontal polarizations for various frequencies in each compartment. Red circles

(•) are in the main cabin, blue diamonds () are in the flight deck, and green squares ()

are in the cargo closet.

96
We would like to thank Robert Morrison and Anthony Wilson from the FAA in Atlantic City,

New Jersey and David Walen from the FAA office in Renton, Washington for their excellent

assistance and financial support for this work.

9. References

[1] SAE Aerospace Group, Guide to certification of aircraft in a high intensity radiated field

(HIRF) environment. SAE ARP5583 (January 2003).

[2] C. A. Grosvenor, R. T. Johnk, D. R. Novotny, N. Canales, C. M. Weil, J. Veneman, A twophase airframe shielding performance study using ultrawideband measurement systems. Natl.

Inst. Stand. Technol. NISTIR 6622 (January 2003).

[3] J. M. Ladbury, T. H. Lehman, G. H. Koepke, Coupling to devices in electrically large

cavities or why classical emc evaluation techniques are becoming obsolete. 2002 Intl Symp. on

Electromagnetic Compatibility, 2: 648-655 (August 2002).

[4] P. F. Wilson, D. A. Hill, C. L. HoUoway, On determining the maximum emissions from

electrically large sources. 2002 IEEE Trans. Electromagnetic Compatibility, 44(1): 79-86

(February 2002).

[5] R. T. Johnk, B. Archambeault, D. Novotny, Using joint time-frequency analysis to enhance

time-domain numerical emc simulations. 2003 Annual Report Interference Technology (2003).

[6] R. C. Wittmann, M. H. Francis, L. A. Muth, R. L. Lewis, Proposed uncertainty analysis for

RCS Measurements. Natl. Inst. Stand. Technol. NISTIR 5019 (January 1994).

[7] J. R. Taylor, An introduction to error analysis. University Science Books, Sausolito, CA,

(1997).

[8] B. N. Taylor, C. E. Kuyatt, Guidelines for evaluating and expressing the uncertainty of NIST

measurement results. Natl. Inst. Stand. Technol. Tech. Note 1297 (September 1994).

[9] E. B. Larsen, R. L. Ehret, D. G. Camell, G. H. Koepke, Calibration of antenna factor at a ground screen field site using an automatic network analyzer. 1989 Intl. Symp on

Electromagnetic Compatibility, 1: 19-24 (August 1989).

[10] R.T. Johnk; Ultrawideband shielding evaluation of a business jet. SAE Lightning

Committee Meeting (May 2006).

97
Appendix A. Time Domain Waveform Analysis

Time-domain waveforms provide important information on the penetration of electromagnetic

fields into an airframe. Figure 142 shows the time-domain waveform for a DRG antenna

transmitting in the horizontal polarization at an angle of 70°. The waveform shows an initial direct antenna response followed by a short period where the signal decays, and then a secondary

impulse that decays into the reverberant fields inside the airframe. These different waveform

characteristics are outlined in Figure 143. We have defined the four parts of the waveform as follows: (1) the direct component, shown in the black rectangle, includes only the initial impulse

response from the antenna; (2) the initial gate, shown in the blue rectangle, includes the direct

component plus the decay from this initial impulse; (3) the reverberant component, shown in the

green rectangle, includes the secondary signal build-up and the signal decay out to where the

energy of the signal no longer contributes significantly to the signal; and (4) the entire signal,

shown in the red rectangle, which extends from the initial part of the waveform until the same

point in (3) where the energy no longer contributes significantly to the signal. From the

waveform in Figure 143 we see that the direct component comprises a small portion of the entire

signal, so we expect that this component will not contribute much to the airframe penetration.

The initial gate, which includes the direct component, contributes a little more to the entire signal

but will not contribute much to overall penetration. In this example, the reverberant fields

contribute the most energy to the entire signal. We conclude that the reverberant fields at this

position are very important to the airframe penetration. This is shown by the frequency response

curves in Figure 144. Note that the entire signal waveform (direct + reverberant parts) looks very

similar to the reverberant signal waveform.

0.0006

-0.0006

100 200

Time (ns) 300

Figure 142. Time-domain waveform for a DRG antenna transmitting at angular position 70'

Receiving anterma in the main passenger cabin.

98
Let's examine another position, at 140°, where the direct component is large compared to the

reverberant fields. This is shown in Figure 145 using the same color scheme given above. Here

we see that the direct component is almost five times larger than that for Figure 143, and so we

expect both the direct component and the initial gate to contribute more to the overall penetration

into the aircraft and for the reverberant fields to contribute significantly less. Figure 146 is the

frequency-domain response for this same position, showing that indeed the direct component and

initial gate contribute strongly to the overall penetration and the reverberant fields contribute

very little. Notice also that the direct component is a smoothed version of the entire signal, and

that the initial gate, which is a combination of the direct response and the initial decay of the

direct response, shows much of the same "hashy" behavior of the entire signal. This tells us that

the noise associated with this signal is a direct result of secondary reflections. We saw this same

phenomenon when we gated out the ground bounce from our reference measurements in Section

4. Finally, at the 1 80° position, where no direct component is available, we find that the signal,

initial decay, and reverberant fields seem to contribute equally to the penetration curves shown in

Figures 147 and 148.

0.0006

0.0004

0.0002

-0.0004

-0.0006

Direct Gate - Black line

Initial Gate - Blue line Re\ erb Gale - Green line Signal Gate - Red line

End Gate

stops at 800 ns

100 200 300

Time (ns)

Figure 143. Time-domain waveform for a DRG antenna transmitting at angular position of

70°. Application of various gates to look at penetration dependence for the direct antenna

interaction and reverberant fields.

99
-a

5

13N

O

-20 -

-40

-60

-80

DRG - Hpol

70 degrees

Main Cabin

Direct (time gate - 50 to 75 ns) Signal (time gate - 10 ns to 800 ns)

Initial (time gate -10 ns to 85 ns) Reverb (time gate - 85 ns to 800 ns)

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 144. Frequency-domain curves for a DRG antenna transmitting at angular position of

70°. Application of various gates to look at contribution to penetration of the direct antenna

interaction or the reverberant fields.

100
S

<

c

60

U

N

O

0.003

0.0025 -

0.002

0.0015 -

0.001

0.0005

-

-0.0005

-0.001

-0.0015 "

^?fz:

40

-^|n^

^---7

Direct Gate - Black dotted line

Initial Gate - Blue line Reverb Gate - Green line Signal Gate - Red line

End Gate

stops at 800 ns

i| Wi'/f.f^^^^^^^

End Gate » stops at 800 ns

60 80

Time (ns) 100 120

Figure 145. Time-domain waveform for a DRG antenna transmitting at angular position of

140°. Application of various gates to look at penetration dependence for direct antenna

interaction and reverberant fields.

o

-20

03

-dN

-40

-60

-80

DRG - Hpol

140 degrees

Main Cabin

Direct (time gate - 50 to 75 ns) Signal (time gate - 10 ns to 800 ns)

Initial (time gate -10 ns to 85 ns) Reverb (time gate - 85 ns to 800 ns)

4000 8000 12000 16000 20000

Frequency (MHz)

Figure 146. Frequency-domain curves for a DRG antenna transmitting at angular

position of 140°. Application of various gates to look at contribution to penetration of the direct antenna interaction or the reverberant fields.

101
After understanding how gating can affect penetration, we must answer the questions: (1) When

time gating, should we keep or discard the direct components? (2) Is it better to remove the

direct component and observe only the reverberation part of the waveform? and (3) If we keep

the direct component to obtain penetration, how much can this bias our results? We have plotted

the penetration results at several frequencies for both the reverberant components and the

reverberant plus the direct components around the aircraft, as shown in Figures 149 to 158. The

data for the DRG antenna in the horizontal polarization are shown in Figure 149 to 153 and for

the DRG antennas in the vertical polarization in Figures 154 to 158. The data show that

including the direct component can introduce a larger error than if it is not included. This is because the direct component contains many of the higher-frequency components. For this reason, when processing the data shown in this report, we have included both the direct and

reverberant components. Since no direct component was observed for the TEM horn antennas in

either polarization, the answer to this question is obvious and makes the argument self- consistent. There is less penetration at the flight deck windows and rear of the aircraft with the

antenna in the main passenger cabin. More penetration is observed at positions where the

transmitter has direct access to the main passenger cabin.

o

12

0.003

0.0025 -

0.002 ^

u 0.0015

I 0.001 B< 0.0005

.^

enI -0.0005

-0.001

-0.0015 H

J -0.002

-0.0025 I

-0.003 4

jlHleXip^ftwinwiKow-)"

DRG - Hpol

1 80 degrees

100 200

Time (ns) 300

Figure 147. Time domain waveform for a DRG antenna transmitting at angular position of

180°. Application of various gates to look at penetration dependence for direct antenna

interaction and reverberant fields.

102
CQ

0) "9

-aN

o

-20

^ -40

-60

-80

DRG - Hpol

1 80 degrees

Main Cabin

Signal (time gate - 10 ns to 800 ns)

Initial (time gate -10 ns to 85 ns) Reverb (time gate - 85 ns to 800 ns)

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 148. Frequency domain curves for a DRG antenna transmitting at angular

position of 180°. Application of various gates to look at contribution to penetration of the direct antenna interaction or the reverberant fields.

103
DRG Hpol

800 MHz

Main Cabin 320 + + + Reverb only • • • Direct & Reverb

300

280

260

240

220

340

••••^(

20

40 > • • 60

50 -40 -30 -ap^ L-10 J

80

100

120

200

140

160 180

Figure 149. Penetration at 800 MHz, for the DRG antennas in the horizontal

polarization, by computing only the reverberant component (black +) vs. computing the direct plus reverberant component (red •).

+

DRG Hpol

1000 MHz

Main Cabin

+ Reverb only ^^0 • Direct & Reverb

300

280

260

240

220

340

•••••< •

20

• •

40

60

.Sa -40 -30-20^10

80

100

120

140

200

180 160

Figure 1 50. Penetration at 1000 MHz, for the DRG antennas in the horizontal

polarization, by computing only the reverberant component (black +) vs. computing

the direct plus reverberant component (red •).

104
DRG Hpol

5000 MHz

Main Cabin

+ + + Reverb only • • • Direct & Reverb

300

320

340 20

40

••••^ f

60

240

220

50-40 ^^3f--^l40^

+ _ •

80

100

120 • •

140

200 160

180

Figure 151. Penetration at 5000 MHz, for the DRG antennas in the

horizontal polarization, by computing only the reverberant component

(black +) vs. computing the direct plus reverberant component (red •).

DRG Hpol

10000 MHz

Main Cabin

+ + + Reverb only • • • Direct & Reverb

300

320

340

• •^ 1

20

40

60

280

260

240

220 140

200 160

180 Figure 152. Penetration at 10000 MHz, for the DRG antennas in the vertical

polarization, by computing only the reverberant component (black +) vs. computing the direct plus reverberant component (red •).

105
DRG Hpol

18000 MHz

Main Cabin

+ + + Reverb only • • • Direct & Reverb

300

280

320

340 20

40

260 >

'<"'/ iSO -40 50-^2<|»i-10

+ + ^

80

100

• ••

240 • ++*'•*. 120

220 140

200 160

180 Figure 153. Penetration at 18000 MHz, for the DRG antennas in the

horizontal polarization, by computing only the reverberant component

(black +) vs. computing the direct plus reverberant component (red •).

DRG Vpol

800 MHz

Main Cabin

+ + + Reverb only ^20 • • • Direct & Reverb

300

280

260

240

340 20

40

sa -40 -3r 4%j-iit ,0

80

100 '^•v • ••+

120

220 140

200

180 160

Figure 154. Penetration at 800 MHz, for the DRG antennas in the vertical

polarization, by computing only the reverberant component (black +) vs. computing the direct plus reverberant component (red •).

106
DRG Vpol

1000 MHz

Main Cabin

+ + + Reverb only • • • Direct & Reverb

300

320

340 20

• •

40

•••

60

280

260

240

Figure 155. Penetration at 1000 MHz, for the DRG antennas in the vertical

polarization, by computing only the reverberant component (black +) vs. computing the direct plus reverberant component (red •).

DRG Vpol

5000 MHz

Main Cabin

+ + + Reverb only • • • Direct & Reverb

300

320

340 20

40

60

280

260

240

-5o;;'^^o -30 -ie J40»

100

120

220 140

200 160

Figure 156. Penetration at 5000 MHz, for the DRG antennas in the vertical

polarization, by computing only the reverberant component (black +) vs. computing the direct plus reverberant component (red •).

107
DRG Vpol

10000 MHz

Main Cabin

+ + + Reverb only • • • Direct & Reverb

320

280

260

240

340 20

40

80

-5ft -40 -30 420 rip

+ ^ 100

.••• 120

220 140

200

180

160

Figure 157. Penetration at 10000 MHz, for the DRG antennas in the vertical

polarization, by computing only the reverberant component (black +) vs. computing the direct plus reverberant component (red •).

DRG Vpol

18000 MHz

Main Cabin

+ + + Reverb only • • • Direct & Reverb

300

280

260

240

220

200

50 -40 -30 -40^0 '0 +• " 100

*t*

••*••/

120

140

180 160

Figure 158. Penetration at 18000 MHz, for the DRG antennas in the vertical

polarization, by computing only the reverberant component (black +) vs. computing the direct plus reverberant component (red •).

108
Appendix B. Signal and Noise Cliaracteristics

Typical signal and noise characteristics are shown in Figures 159 to 161 for the three

compartments: (1) main passenger cabin, (2) flight deck, and (3) cargo closet, at three different

angular positions: (1) 30°, (2) 45°, and (3) 180°, respectively. We have plotted only the DRG

horn antenna in the horizontal polarization for this section. Noise is a function of position due to the location of ambient RF sources which the aircraft may shield from the internal antennas as we move around the aircraft. Noise floors tend to be around -60 dB to -80 dB at the lower

frequencies and climb to around -50 dB at the higher frequencies. Noise levels peak at frequencies around 2000 MHz due to external sources. The rise in the noise floor at around 9

GHz is due to the attenuator configuration of the VNA for the upper frequencies. The signal-tonoise ratios for the main passenger cabin vary from 30 dB to 60 dB. In the flight deck, the

signal-to-noise ratio varies from 20 dB to 55 dB, and in the cargo closet, the signal-to-noise ratio

varies from 15 dB to 55 dB.

The signal-to-noise characteristics for the TEM horn antennas are a little different due to the FM

frequency bands. Over the frequency band from 100 MHz to 1500 MHz, typical signal-to-noise

ratios range from 20 dB at the lower frequencies to 60 dB at the higher frequencies.

COG

O

1u

c

<u Oh

-20

-40

-60

-80

-100

Main Cabin

30 degrees

DRG - Hpol — Noise floor

'~^~^.

•TA/V'V-^

LV4000 8000 12000

Frequency (MHz)

16000 20000

Figure 159. Typical signal and noise characteristics for measurements in the main

passenger cabin. This particular noise measurement was taken at an angle of 30°.

109
PQ3

so

is

<DC

(L>

-20

-40

-60

-80

-100

\y-^'^^'-

Flight Deck

90 degrees

DRG - Hpol

Noise floor

/--A^'Vv/^l^/^A/v-/'y"^..v.-^''

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 160. Typical signal and noise characteristics for measurements in the flight deck.

This particular noise measurement was taken at an angle of 90°.

PQ-aao

0-n

-20

-40

g -60

-80

100

-.r-^

, r-v^,^

Cargo Closet

1 80 degrees

DRG - Hpol

Noise floor

4000 8000 12000

Frequency (MHz)

16000 20000

Figure 161. Typical signal and noise characteristics for measurements in the cargo

closet. This particular noise measurement was taken at an angle of 180°.

110
Appendix C: TEM and DRG Horn Boresight Gain Characteristics

The DRG and TEM horn antennas used in this effort were caHbrated before we deployed our system in Atlantic City. This technique can be used to derive antenna gain with a specified

resistive load (typically 50 Q) at the antenna terminals. An accurate method for doing this is the

three-antenna method. As the name implies, three transmission measurements are made with

three combinations of the three antennas. This procedure is described in detail in reference [9].

This process yields three equations that can be readily solved for either gain or antenna factor.

The gain characteristics of our DRG horn antennas are shown in Figure 162; those for our 36 cm

TEM horns are shown in Figure 163; and those for our 1.2 m TEM horns are shown in Figure

164. The gains displayed in these figures include the antenna input mismatch, which accounts

for the reduction of gain at the lower frequencies. The DRG horn antenna gain, plotted in Figure

162 shows that the low-frequency cutoff of these antennas occurs around 750 MHz. As the

frequency is reduced, the input mismatch increases, which accounts for a rapid decrease in

antenna gain. Mismatch and gain are not cause and effect, but a combination of both aperture

beam forming and a better input match accounts for the increasing gain at the higher frequencies.

A maximum gain of approximately 15 dB occurs at 16000 MHz. The 36 cm antenna resuhs,

plotted in Figure 1 63 show a maximum gain of approximately 7 dB realized at 4,000 MHz.

Results for a NIST 1 .2 m horn antenna are plotted in Figure 164. This horn is longer, and it has a

resistive taper, which improves the low-frequency performance. The maximum frequency of this

antenna is 1500 MHz, due to balun performance limitations and a maximum gain of 7 dB occurs

at this frequency as well.

Ill
20 —

1

OQ

CO a

8000 12000 Frequency (MHz)

16000 20000

Figure 162. Measured boresight antenna gain for a 3 1 17 DRG horn antenna. The gains

plotted here include the input mismatch effects, which account for the rapid decrease

below 750 MHz.

.8.846. '°

1 1 1 1 1 1 _ .-1^""*'""

^/"

-10 - /

-

c

so Gq -30

-40

-50

- -

1

-51.078_6o 1 1 1 1 1 1 1 500 1000 1500 2000 2500 3000 3500 40 00

.2.498. Homl_2^''* Frequency (MHz)

.4x10^.

-

Figure 163. Measured boresight antenna gain for three identical NIST 36 cm TEM horn

antennas. The gains plotted here include the input mismatch effects, which account for the

rapid decrease below 100 MHz.

112
Freq Frequency (MHz)

Figure 164. Measured boresight antenna gain for a NIST 1.2 m TEM horn antenna,

gains plotted here include the input mismatch effects, which account for the rapid

decrease below 50 MHz.

The

Appendix D: Penetration Data for HIRF Frequency Bands

The peak and average field strengths in a HIRF environment are defined for specific frequency

bands [1]. The frequency bands that correspond to our measured data are: (1) 200 MHz to 400

MHz, (2) 400 MHz to 700 MHz, (3) 700 MHz to 1000 MHz, (4) 1000 MHz to 2000 MHz, (5)

2000 MHz to 4000 MHz, (6) 4000 MHz to 6000 MHz, (7) 6000 MHz to 8000 MHz, (8) 8000

MHz to 12000 MHz, and (9) 12000 MHz to 18000 MHz. If we determine the maximum

penetration per compartment in these same frequency bands and plot it versus our measured data,

this is likely of more interest to the HIRF community. Figures 165 to 167 are plots for the TEM

and DRG antennas in the vertical and horizontal polarizations, at one angular position for each of

the measured compartments. The black dotted line indicates the maximum penetration for that

compartment.

Figure 1 65 shows the penetration data as a function of the HIRF environment frequency bands

for the receiving antenna in the main cabin and the transmitting antenna at an angular position of

145°. This is an angle where there is high electromagnetic penetration into the aircraft. We

notice that the maximum penetration is positive in certain frequency bands. Although the

solution seems at first unrealistic, we have shown from our penetration definition that an aperture

backed by a cavity can lead to a positive penetration value [10]. Penetration into the flight deck

at an angle of 340° is shown in Figure 166. Again, the black dotted line shows the maximum

113
penetration for all angles as a function of the frequency band. We can see that the penetration

into the aircraft at this angle is well below that of the maximum penetration for this cavity.

Finally, Figure 1 67 shows the penetration for the receiving antenna in the cargo closet, and the

transmitting antenna at an angle of 50°. Most of the data in the lower frequency bands are well

below the maximum penetration, and in the upper frequency bands we see that the penetration is closer to the maximum penetration for this compartment. If we use the maximum penetration for

each compartment, we can then determine the peak and average field levels inside that

compartment from the peak and average field levels outside of the aircraft.

114
240

Main Cabin - 145 degrees TEM - Hpol DRG-Hpol TEM - Vpol DRG - Vpol

i

'

i 280 320

Frequency (MHz)

500

Frequency (MHz)

700 800 900

Frequency (MHz)

1000 1200 1400 1600 Frequency (MHz)

1 I

'

I I

'

I 3000 2400 2800 3200 3600

Frequency (MHz)

4400 4800 5200

Frequency (MHz)

5600 6000

6000 6400 6800 7200 7600 moa

Frequency (MHz)

9000 10000 11000

Frequency (MHz)

I128M 14000 16000

Frequency (MHz)

Figure 165. Frequency band exploded view of the penetration for all antennas and polarizations for the transmitting tower placed at the 145° position and the receiver placed in the main cabin.

115
Flight Deck - 340 degrees TEM - Hpol DRG - Hpol TEM - Vpol DRG - Vpol

200 240 280 320

Frequency (MHz)

360 400 500 600

Frequency (MHz)

t

' T"

800 900

Frequency (MHz)

1000

1200 1400 1600 1800 Frequency (MHz)

2400 2800 3200 3600 4000 4400 4800 5200

Frequency (MHz) Frequency (MHz)

5600 6000

6000 6400 6800 7200

Frequency (MHz)

9000 10000 11000 12000

Frequency (MHz)

14000 16000

Frequency (MHz)

Figure 166. Frequency band exploded view of the penetration for all antennas and polarizations for the transmitting tower placed at the 340 ° position and the receiver placed in the flight deck.

116
Cargo Closet - 50 degrees TEM - Hpol DRG - Hpol TEM - Vpol DRG - Vpol

-50

200 280 320 360

Frequency (MHz)

500 600

Frequency (MHz)

800 900

Frequency (MHz)

'

'

I

'

I 4400 4800 5200

Frequency (MHz)

1000 1200 1400 1600 Frequency (MHz)2800 3200

Frequency (MHz)

3600 4000 5600 6000

6000 6400 6800 7200

Frequency (MHz)

I

'

i

'

1 9000 10000 IIOOO

Frequency (MHz)

14000 16000

Frequency (MHz)

Figure 167. Frequency band exploded view of the penetration for all antennas and polarizations

for the transmitting tower placed at the 50° position and the receiver placed in the cargo closet.

117
Appendix E: Bombardier Global 5000 Measurement Equipment List*

The main equipment used in the evaluation of the Bombardier Global 5000 is listed below:

Agilent N5230A PNA-L (300 kHz to 18 GHz) with a maximum of 16001

frequencies/trace.

Insulated Wire (IW) Cables (4 m to5 m)—^we used phase-stabilized cables to avoid phase

drift with temperature variations.

Miteq Optical Fiber Link MDDR/MDDT (11 GHz version)—this unit has the ruggedness

and temperature characteristics for field use.

Miteq Optical Fiber Link SCMR/SCMT (18 GHz version)—^this unit has the ruggedness

and temperature characteristics for field use.

HP 1 1713A Switch Controller and HP 3781 Switches

HP 59306A Relay Actuator

HP E361 5A DC Power Supply for relay control

AML 0120L2403 Amplifier for DRG antennas

Harrison 6205 DC Power Supply

Two 1 .2 m TEM Horn Antennas designed and built at the NIST Boulder Laboratories

One 36 cm TEM Horn Antenna designed and built at the NIST Boulder Laboratories

Three 3117 DRG Horn Antennas

NIST-developed "RADAR" Labview program used to perform time/frequency

transformations, time gating, and signal processing

NIST-developed "multical" Labview program used to perform multiband VNA

calibrations and to circumvent the limitation of only 16001 frequency points. This

program permits an arbitrarily large number of frequency points. In practice we typically use as many as 48003 points.

Certain commercial equipment, instruments, or materials are identified in this paper in order to adequately specify

the experimental procedure. Such identification does not imply recommendation or endorsement by the National

Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily

the best available for the purpose.

118
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