NTIA Report TR-12-483

A Prototype Antenna for Total RF Field

Measurement

J. Wayde Allen

NTIA Report TR-12-483

A Prototype Antenna for Total RF Field

Measurement

J. Wayde Allen

U.S. DEPARTMENT OF COMMERCE

October 2011
DISCLAIMER

Certain commercial equipment, materials, and/or programs are identified in this report to

specify adequately the experimental procedure. In no case does such identification imply

recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the program or equipment identified is necessarily the

best available for this application.
CONTENTS

Page

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 DESIGN OF THE ANTENNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 PROOF OF CONCEPT TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4 DATA ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.1 Detecting polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.2 Total Power Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5 CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

6 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

iii

A PROTOTYPE ANTENNA FOR TOTAL RF FIELD MEASUREMENT

J. Wayde Allen1

The total radio frequency (RF) field strength is the sum of all signals incident

at a given location. These signals can originate from many directions and have

various polarizations. This complicates the measurement of the total RF field since

commonly used antennas (dipoles, whips, etc.) respond to signals coming from a

specific direction and with a specific polarization.

This paper describes a prototype antenna constructed from three crossed dipole

elements. The output from these three dipole elements can be used to detect signals having arbitrary polarization, and arriving from any direction. This makes it

possible to perform real-time measurement of the total RF field.

Key words: antenna; crossed dipole; electromagnetic; electro-space; environment; noise; polarization; radio; RF; spectrum survey; Table Mountain

1 INTRODUCTION

At any arbitrary location, the total radio frequency (RF) field strength is the sum of the radio

signals arriving at that location. These signals can arrive from many different directions and

have varying polarizations. Unfortunately, antennas commonly used for measuring these

signals (vertical whips, dipoles, Yagi arrays, etc.) respond most strongly to signals having

a specific polarization or arriving from a certain direction. Consequently radio surveys are

generally limited to vertically or horizontally polarized signals. In some cases, diagonally

mounted Yagi antennas are used so that the response to horizontal and vertical polarizations

are roughly equal, but this only works for signals originating from the direction in which the

Yagi is pointed. This leaves us with two options for measuring the total field strength:

• make repeat measurements using more than one antenna type and/or orientation, or

• create several measurement systems configured with different antennas.

The first option uses the least amount of receiver hardware, but is time consuming and makes

the assumption that the field is relatively static so that measurements from different time

series can be reasonably combined. The second option uses multiple receivers, which can

be more expensive, but takes less time to perform and will work with time varying signals.

In either case, an antenna combination needs to be chosen that minimizes the number of

tests or receivers needed, and that makes combining these data straight forward. This paper

describes an antenna array designed specifically for this purpose.

1The author is with the Institute for Telecommunication Sciences, National Telecommunications and

Information Administration, U.S. Department of Commerce, Boulder, Colorado 80305.
x

Y

Z

X-Dipole

Y-Dipole

Z-Dipole

Figure 1: Dipole antennas relative to a 3D reference cube.

This antenna array consists of three orthogonal dipole antennas oriented as shown in Figure 1.

In this configuration, each dipole element responds most strongly to linearly polarized signals

that match the axis of the antenna element, and which are incident at right angles to the

plane in which the antenna element resides. The output from each of the dipole elements in

this array is proportional to the vector field components Ex, Ey, and Ez. This concept has

been used for the construction of various EM radiation monitors, but these are usually only

coupled to square law power detectors and no phase information is preserved. Positioning

the elements adjacent to each other and sampling the E-field components simultaneously

preserves phase information.

A prototype crossed dipole array like this was constructed in the early 1980’s at the National Bureau of Standards (now the National Institute for Standards and Technology or

NIST)[1][2]. The NIST design used mechanical switching to alternately connect the dipole

antennas to a single back-end spectrum analyzer. This allowed total field measurements in

the presence of signals that didn’t change during the time interval required to switch between

the antenna elements. However, since readings were taken sequentially rather than simultaneously, the instantaneous total field could not be measured, and again phase information

was lost.

The system described here uses a true three channel receiver capable of recording the E-field

voltages induced in each of the dipoles in synchronous real-time. This makes it possible not

only to gather information about the total RF field strength regardless of direction of arrival,

but also to distinguish polarization, and possibly even direction of arrival.

2
2 DESIGN OF THE ANTENNA

The antenna consists of an array of three orthogonally arranged dipole elements, each with

its own tuning filter and preamplifier feeding a separate channel on a digitizing oscilloscope.

Figure 2 shows a basic block diagram of the circuit.

Dipole Antennas

Filter

Digital Oscilloscope

X-Channel

Y-Channel

Z-Channel

Filter

Filter

Figure 2: Block diagram of the antenna system.

This decision allows us to tune the array to a specific frequency range using the filters, and

to capture time domain data of the signal as detected by the X, Y, and Z dipole elements.

We wanted to make the dipole elements tunable to test at different frequencies. A vendor was

found that could provide telescoping antenna elements that could be adjusted from 17.78

to 71.12 centimeters (7 to 28 inches), giving a useable frequency range of approximately

100 to 401 MHz. Plastic mounting blocks were made to hold these elements in appropriate

orientation to each other. Two of these blocks were made.

The first of these blocks was made with the mounting support hole drilled parallel to the

Z-axis dipole. This configuration simplifies testing by eliminating the need for transforming

our data between the antenna and laboratory coordinate systems, and consequently is the

focus of this paper. The resulting structure is shown in Figure 3.

3
Figure 3: Picture of the crossed dipole array arranged with elements relative to the laboratory

coordinate system.

4
Figure 4: Picture of the diagonal mounting block.

5
In the second block, the mounting support rod runs along the diagonal of the block as shown

in Figure 4. This diagonal mount design has the advantage of orienting each antenna element

symmetrically around the support structure. A problem with this configuration is that it

tips the XY-plane described by the X and Y antenna elements so that it no longer is parallel

to the surface of the earth. For terrestrial systems, horizontal and vertical polarization

is generally defined relative to the “laboratory frame of reference” where the XY-plane is

parallel to the surface of the earth. This means that using the antenna constructed with the

diagonal mounting block requires a coordinate system transformation to get E

0

x

, E

0

y

, and E

0

z

into the laboratory frame of reference Ex, Ey, and Ez. Testing of the diagonal mounting

block has not been completed and will not be discussed in this paper.

Broadband balun transformers are used to connect the dipole elements to the coaxial feed

that runs down through a piece of 1 inch plastic tubing that provides the mounting support

for the antenna.

6
3 PROOF OF CONCEPT TESTING

We ran three basic tests to see if this 3-axis antenna design concept worked as expected:

1. Test the response of the 3-axis antenna to various polarized signals incident from

different directions.

2. Verify that the antenna response would show the total incident power proportional to

|Ex|

2 + |Ey|2 + |Ez|2

regardless of the polarization or angle of incidence.

3. Measure the antenna transmission pattern with each of the elements driven with inphase signals and compare this to a computer simulation using an NEC model.

The setup for the first two tests used a Yagi antenna driven by a signal generator set to

402.5 MHz and a power of 10 dBm. This frequency is slightly higher than the predicted

resonance of the antenna, but not appreciably so. The decision to use this frequency was

driven by the availability of an existing three channel filter/amplifier box. The Yagi antenna

was mounted on a tripod in the NIST anechoic chamber with the 3-axis receive antenna

mounted on the antenna rotator. This allowed the Yagi to present a fixed level signal with a

polarization relative to its orientation (horizontal, 45 degree slant, or vertical). The output

of the 3-axis antenna was connected to the filter/amplifier box to provide selectivity and

gain and the resulting channels for Ex, Ey, and Ez were fed into a digitizing oscilloscope.

Figure 5 shows a block diagram, and Figure 6 shows a photograph of the actual test setup.

Plots of the measured voltages Ex, Ey, and Ez data can be seen in Figures 7–15.

As can be seen, the relative amplitudes of the traces do seem to vary as expected with

respect to the polarization angle and angle of incidence. Also, since the transmit power was

held constant during the measurements these data can be used to verify whether the total

received power is proportional to |Ex|

2 + |Ey|2 + |Ez|2

. This satisfies the data acquisition for

the first two verification tests.

The third and last test is to see if the real-life antenna array performs as predicted by the

NEC model. This requires reconfiguring the antennas as shown in Figure 16.

For this test, the 3-axis antenna is the transmit antenna, and is fed by a signal generator

through a power splitter providing three in-phase signals to each of the three dipoles in the

array. The Yagi array was used as a fixed, horizontally polarized, receive antenna connected

to a power meter. The 3-axis antenna was then oriented at five tilt angles (0 degrees,

22.5 degrees, 45 degrees, 67.5 degrees, and 90 degrees) as shown in Figure 17. In this case

0 degrees corresponds to the antenna standing vertically upright and 90 degrees corresponds

to the antenna tipped forward to a fully horizontal position. In all but the 90 degree position

the antenna was then rotated in 5 degree increments around its axis and the received power

seen by the Yagi antenna was recorded at each of these intervals. Fewer points were taken

at the 90 degree position since the Yagi was aimed straight down onto the 3-axis antenna at

this point.

7
Rotator

Yagi Antenna

3-axis Antenna

(Tiltable)

Signal

Generator Oscilloscope

~ 4.75 meter separation

Figure 5: Block diagram of the test setup.

Figure 6: Photograph of the test setup.

8
Horizontal Polarization

Yagi Array

(axial view)

(a) Yagi Antenna Orientation

3-axis antenna

y-element

x-element

z-element

(top view, 0 degrees rotation)

Direction of test signal

(b) 3-axis Antenna Orientation

(c) Plot of oscilloscope trace (5 nSec trace, 202 samples).

Figure 7: Measurement with horizontal Yagi antenna, and 3-axis antenna not rotated.

Graphic (a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna

rotation, and (c) shows the resulting oscilloscope trace.

9
Horizontal Polarization

Yagi Array

(axial view)

(a) Yagi Antenna Orientation

3-axis antenna

y-element

x-element

z-element

Direction of test signal

(top view, 45 degrees rotation)

(b) 3-axis Antenna Orientation

(c) Plot of Oscilloscope trace (5 nSec trace, 202 samples).

Figure 8: Measurement with horizontal yagi antenna, and 3-axis antenna rotated 45 degrees.

Graphic (a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna

rotation, and (c) shows the resulting oscilloscope trace.

10
Horizontal Polarization

Yagi Array

(axial view)

(a) Yagi Antenna Orientation

3-axis antenna

y-element

x-element

z-element

Direction of test signal

(top view, 90 degrees rotation)

(b) 3-axis Antenna Orientation

(c) Plot of Oscilloscope trace (5 nSec trace, 202 samples).

Figure 9: Measurement with horizontal yagi antenna, and 3-axis antenna rotated 90 degrees.

Graphic (a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna

rotation, and (c) shows the resulting oscilloscope trace.

11
Yagi Array

(axial view)

Slant Polarization

(a) Yagi Antenna

Orientation

3-axis antenna

y-element

x-element

z-element

(top view, 0 degrees rotation)

Direction of test signal

(b) 3-axis Antenna Orientation

(c) Plot of Oscilloscope trace (5 nSec trace, 202 samples).

Figure 10: Measurement with slant polarized yagi, and 3-axis antenna not rotated. Graphic

(a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna rotation, and

(c) shows the resulting oscilloscope trace.

12
Yagi Array

(axial view)

Slant Polarization

(a) Yagi Antenna

Orientation

3-axis antenna

y-element

x-element

z-element

Direction of test signal

(top view, 45 degrees rotation)

(b) 3-axis Antenna Orientation

(c) Plot of Oscilloscope trace (5 nSec trace, 202 samples).

Figure 11: Measurement with slant polarized yagi, and 3-axis antenna rotated 45 degrees.

Graphic (a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna

rotation, and (c) shows the resulting oscilloscope trace.

13
Yagi Array

(axial view)

Slant Polarization

(a) Yagi Antenna

Orientation

3-axis antenna

y-element

x-element

z-element

Direction of test signal

(top view, 90 degrees rotation)

(b) 3-axis Antenna Orientation

(c) Plot of Oscilloscope trace (5 nSec trace, 202 samples).

Figure 12: Measurement with slant polarized yagi, and 3-axis antenna rotated 90 degrees.

Graphic (a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna

rotation, and (c) shows the resulting oscilloscope trace.

14
Yagi Array

(axial view)

Vertical Polarization

(a) Yagi Antenna

Orientation

3-axis antenna

y-element

x-element

z-element

(top view, 0 degrees rotation)

Direction of test signal

(b) 3-axis Antenna Orientation

(c) Plot of Oscilloscope trace (5 nSec trace, 202 samples).

Figure 13: Measurement with vertically polarized yagi, and 3-axis antenna not rotated.

Graphic (a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna

rotation, and (c) shows the resulting oscilloscope trace.

15
Yagi Array

(axial view)

Vertical Polarization

(a) Yagi Antenna

Orientation

3-axis antenna

y-element

x-element

z-element

Direction of test signal

(top view, 45 degrees rotation)

(b) 3-axis Antenna Orientation

(c) Plot of Oscilloscope trace (5 nSec trace, 202 samples).

Figure 14: Measurement with vertically polarized yagi, and 3-axis antenna rotated 45 degrees. Graphic (a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna

rotation, and (c) shows the resulting oscilloscope trace.

16
Yagi Array

(axial view)

Vertical Polarization

(a) Yagi Antenna

Orientation

3-axis antenna

y-element

x-element

z-element

Direction of test signal

(top view, 90 degrees rotation)

(b) 3-axis Antenna Orientation

(c) Plot of Oscilloscope trace (5 nSec trace, 202 samples).

Figure 15: Measurement with vertically polarized yagi, and 3-axis antenna rotated 90 degrees. Graphic (a) shows the Yagi antenna orientation. Graphic (b) shows the 3-axis antenna

rotation, and (c) shows the resulting oscilloscope trace.

17
Rotator

Yagi Antenna

3-axis Antenna

(Tiltable)

Power

Meter

Signal

Generator

3-way

Splitter

~ 4.75 meter separation

Figure 16: Antenna configuration for transmission pattern test.

Figure 17: Tilt angles for the 3-axis antenna pattern measurement.

18
For comparison, a computer simulation using the Numerical Electrical Code (NEC) Method

of Moments was set up as follows:

CM NEC Input for 3-axis Antenna

CM

CM Author: J.W. Allen

CM Date: 2010-08-13

CM

CM Element Diameter 0.00508 meters (0.2 inches)

CM Dipole is center fed with 17.78 cm (7 inches) to each side

CM Single frequency excitation at 421 MHz on the center (5th segment)

CM I’ve added 0.3175 cm (1/8 inch) to each side.

CM This creates a 0.635 cm (1/4 inch) feed gap.

CE

GW 1 9 -0.1809 -0.0100 0.0000 0.1809 -0.0100 0.0000 0.00508

GW 2 9 0.0100 -0.1809 0.0100 0.0100 0.1809 0.0100 0.00508

GW 3 9 -0.0100 0.0100 -0.1809 -0.0100 0.0100 0.1809 0.00508

GE

EX 0 1 5

EX 0 2 5

EX 0 3 5

RP 0 36 36 1301 0. 0. 10. 10.

PT 2 5 5 5

XQ

EN

Plots of both the measured and simulated antenna pattern can be seen in Figure 18. It is

particularly interesting to note the deep null in the pattern that occurs along the diagonal

of the coordinate system. This null appears to coincide with the diagonal of the plastic

mounting block shown in Figure 4, which may be a reason to prefer the diagonal mount. This

could minimize the effect of the support structure on the antenna performance. However, in

this paper we report only tests of the structure designed to position the antenna elements

parallel to the laboratory coordinate system.

19
(a) Measured Antenna Pattern

(b) Simulated Antenna Pattern

Figure 18: Comparison of the measured and simulated transmission pattern of the antenna

with all elements fed in phase at the same frequency. Plot (a) shows the measured pattern,

and plot (b) is the simulated pattern.

20
4 DATA ANALYSIS

4.1 Detecting polarization

Returning to the data plotted in Figures 7–15, we would like to find a way to clearly determine

the polarization character of the incident signal. One way to do this is simply to plot the

voltages Ex, Ey, and Ez in three dimensions so that we can see the shape described. For

a horizontally polarized wave aligned with the X-axis antenna element, such a plot should

describe a line with voltage excursions along the x-axis in the plot. Figure 7 shows the

oscilloscope traces for this condition, so re-plotting these data in three dimensions results in

the graph seen in Figure 19.

3DplotofEx,Ey,andEz

Ez(Volts)

Ey(Volts)

Ex(Volts)

Figure 19: Plot of Ex, Ey, and Ez for the horizontally polarized signal at 0 degrees rotation

(aligned with x-axis).

This plot shows these data are close to the predicted horizontal line along the X-axis. The

deviation from the expected line is most likely due to measurement system noise and coupling

between the other orthogonal antenna elements and chamber reflections.

Plotting the horizontally-polarized data for each of the measured rotation angles (0 degrees,

45 degrees, and 90 degrees) produces the plot shown in Figure 20a. Here we can see how the

antenna array responds to the same horizontally polarized signal incident from these three

different angles. Ideally, all three traces should be straight lines, but because the wave is

partially incident on both the X and Y antenna elements, coupling between the two elements

distorts the straight line character of the plot.

Finally plotting all of the measured polarizations and rotation angles results in Figure 20b.

Here we can see that the general trend to render linearly polarized signals as narrow ellipses

21
relative to the polarization angle and angle of incidence is as expected. Ideally, each of

these traces would scribe a line; however, imperfections in the antenna, coupling between

elements, and system noise cause some distortion in the line traces. Whether some of these

effects could be accounted for through antenna calibration is an area to be explored.

4.2 Total Power Measurement

The voltages measured from each of the elements on the 3-axis antenna are proportional to

Ex, Ey, and Ez, and since the time average power is proportional to the square of the E-field

magnitude it should be possible to obtain the total power incident on the antenna as:

Ptotal = Cx|Ex|

2 + Cy|Ey|2 + Cz|Ez|2

(1)

with Cx, Cy, and Cz being a calibration constants for each of the antenna elements.

We tabulated the averages of the square of the measured element voltages to obtain the

results shown in Table 1.

Table 1: Average of the Squared Voltages for Each Antenna Element

Polarization Rotation (degrees) |Ex|

2

|Ey|

2

|Ez|

2

Horizontal 0 0.012838 0.000071 0.000067

Horizontal 45 0.006967 0.003866 0.000046

Horizontal 90 0.000073 0.013891 0.000059

Slant 0 0.006124 0.000079 0.002908

Slant 45 0.003064 0.002168 0.002466

Slant 90 0.000074 0.007611 0.002462

Vertical 0 0.000095 0.000153 0.004661

Vertical 45 0.000343 0.000012 0.004238

Vertical 90 0.000329 0.000116 0.003892

If we knew the calibration constants Cx, Cy, and Cz, these could be converted to powers

using the expressions:

Px = Cx|Ex|

2

, (2)

Py = Cy|Ey|

2

, and (3)

Pz = Cz|Ez|

2

. (4)

Since the original design of the test was for relative rather than absolute powers, we can

simply let Cx, CY , and Cz = 1.

Ideally, only one of the antenna elements should respond under the following conditions:

22
(a) Plot of the X, Y, and Z antenna element voltages for 0 degrees, 45 degrees, and 90 degrees rotation

(b) Plot of Ex, Ey, and Ez for all measured polarizations and rotation angles

Figure 20: Plots of multiple polarization angles. Plot (a) shows the X, Y, and Z antenna

element voltages for 0 degrees, 45 degrees, and 90 degrees rotation. Plot (b) shows Ex, Ey,

and Ez for all measured polarizations and rotation angles.

23
1. Horizontal, 0 degrees Rotation—only Ex should receive power

2. Horizontal, 90 degrees Rotation—only Ey should receive power, and

3. Vertical, any rotation—only Ez should receive power

Unfortunately after looking at these data in Table 1, it became clear that the response of

the Z-element dipole is less than that of the other two. Since we are still only interested in

seeing whether the antenna system will give a constant power reading in any orientation, we

can normalize these data so that each of these special case conditions results in a maximum

reading of one. Taking the value for |Ex|

2

from the first row of Table 1 and substituting into

(2) we obtain a value for Cx that normalizes our maximum power level for X-axis antenna

element with the condition (horizontal, 0 degrees rotation) described above. This results in:

1 = Cx(0.012838), (5)

or

Cx = 1/0.012838 ≈ 77.893 (6)

The Ey and Ez terms should ideally be zero, and as can be seen from Table 1 are small for

this condition; we simply ignore them.

A similar computation performed for the Y-antenna element (horizontal, 90 degrees rotation)

gives:

Cy = 1/0.013891 = 71.989. (7)

For Cz all of the vertical polarized signal orientations work, so:

Cz1 = 1/0.004661 ≈ 214.565 (8)

Cz2 = 1/0.004238 ≈ 235.971 (9)

Cz3 = 1/0.003892 ≈ 256.917. (10)

Taking the average of (8)–(10) gives us a useable value

Cz ≈ 235.817 (11)

Using these normalization coefficients to compute the average normalized powers gives the

results in Table 2.

24
Table 2: Normalized Powers

Polarization Rotation (degrees) Normalized Power

Horizontal 0 1.021

Horizontal 45 0.832

Horizontal 90 1.020

Slant 0 1.168

Slant 45 0.976

Slant 90 1.134

Vertical 0 1.117

Vertical 45 1.027

Vertical 90 0.952

Maximum 1.168

Minimum 0.832

Difference 0.337

Average 1.027

Standard Deviation 0.104

From this, it appears that there is a Type B uncertainty [3] most likely due to calibration

errors and cross coupling between the antenna elements that gives a reading too high by

roughly 0.027, and a Type A random uncertainty [3] of roughly 0.104. Nevertheless, it seems

that this antenna in this rather uncalibrated state can measure the total power regardless of

polarization or angle of incidence to within roughly:

Up =

q

(0.027)2 + (0.104)2 ≈ 0.107, (12)

or with an uncertainty on the order of 10.7 percent. In decibels, this would be approximately

±0.9 dB.

25
5 CONCLUSION

All the tests performed so far seem to indicate that the crossed-dipole, 3-axis antenna concept

is viable. In fact, the idea is really not much different than using a single dipole receive

antenna, and positioning it in a number of different orientations to sample RF energy coming

from different directions, or even tilting it to change the polarization angle. What is unique

about this configuration is that it allows data to be taken from each of the three dipoles

simultaneously. This not only speeds up data acquisition, it also makes it possible to process

the data stream to extract information about polarization and to compute the total RF field

incident on the antenna. There are a number of avenues to explore to expand on this work.

Developing a good way to characterize or calibrate the array is one possible avenue. Another

would be to change the diameter of the dipole elements, or use resistively loaded dipoles to

extend the bandwidth of the antennas. The design used here is relatively narrow-banded, but

using resistively loaded dipoles as was done by Kanda and Ries at NBS would be expected

to expand the useable frequency range. Kanda and Ries reported that their original design

had a relatively flat frequency response from 200 MHz to over 3 GHz [2].

The area that is particularly ripe for exploration would be how best to process data obtained

using the array. We have already started exploring the use of software-defined radio systems

to replace the digital oscilloscope used for these tests. This should help make the development

of more complex, pseudo-real time data analysis possible.

Finally, as was shown with the NEC simulation and the transmit test, the interaction between

the waves can create interesting nulls in the radiated pattern which may be useful to exploit.

The test done here fed the antenna with in-phase signals. Changing the relative phases

applied to each of the elements may make it possible to create controllable radiation patterns

that could be used to steer or blank out the transmitted signal in particular regions.

26
6 REFERENCES

[1] M. Kanda and F. X. Ries, “A Broad-Band Isotropic Real-Time Electric-Field Sensor

(BIRES) Using Resistively Loaded Dipoles,” IEEE Transactions on Electromagnetic

Compatibility, vol. EMC-23, no. 3, August 1981.

[2] M. Kanda and F. X. Ries, “Dipole-Based EM Probe Grabs Complex Fields,” Microwaves,

January 1981.

[3] B. N. Taylor and C. E. Kuyatt, “Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results,” National Institute of Standards and Technology,

Tech. Rep. NIST Technical Note 1297, 1994.

27

Form NTIA-29 U.S. Department of Commerce

(6/04) National Telecommunications and Information Administration

BIBLIOGRAPHIC DATA SHEET

1. Publication Number

TR-12-483

2. Government Accession Number 3. Recipient’s Accession Number

4. Title and Subtitle

A Prototype Antenna for Total RF Field Measurement

5. Publication Date

6. Performing Organization Code

NTIA/ITS

7. Author(s)

J. Wayde Allen

9. Project/Task/Work Unit No.

3155011-300

8. Performing Organization Name and Address

NTIA/ITS.M

U.S. Department of Commerce

325 Broadway

Boulder, CO 80305

10. Contract/Grant Number

11. Sponsoring Organization Name and Address 12. Type of Report and Period

Covered

14. Supplementary Notes

15. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography

or literature survey, mention it here.)

The total radio frequency (RF) field strength is the sum of all signals incident at a given location.

These signals can originate from many directions and have various polarizations. This complicates

the measurement of the total RF field since commonly used antennas (dipoles, whips, etc.) respond

to signals coming from a specific direction and with a specific polarization.

This paper describes a prototype antenna constructed from three crossed dipole elements. The

output from these three dipole elements can be used to detect signals having arbitrary polarization,

and arriving from any direction. This makes it possible to perform real-time measurement of the

total RF field.

16. Key Words (Alphabetical order, separated by semicolons)

antenna; crossed dipole; electromagnetic; electro-space; environment; noise; polarization; radio; RF;

spectrum survey; Table Mountain

17. Availability Statement

X Unlimited

For Official Distribution

18. Security Class (This report) 20. Number of Pages

27

19. Security Class (This page) 21. Price