ARL-TR-8076● JULY 2017

US Army Research Laboratory

Detection of Metallic and Electronic Radar 

Targets by Acoustic Modulation of 

Electromagnetic Waves

by Gregory J Mazzaro, Andrew J Sherbondy, Matthew R Judy, 

Kyle A Gallagher

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Destroy this report when it is no longer needed. Do not return it to the originator.
ARL-TR-8076● JULY 2017

US Army Research Laboratory

Detection of Metallic and Electronic Radar 

Targets by Acoustic Modulation of 

Electromagnetic Waves

by Gregory J Mazzaro

The Citadel, The Military College of South Carolina, Charleston, SC 

Andrew J Sherbondy and Matthew R Judy 

Oak Ridge Associated Universities, Oak Ridge, TN

Kyle A Gallagher

Sensors and Electron Devices Directorate, ARL

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July 2017

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Technical Report

3. DATES COVERED (From - To)

26 June 2017–11 August 2017

4. TITLE AND SUBTITLE

Detection of Metallic and Electronic Radar Targets by Acoustic Modulation of 

Electromagnetic Waves

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Gregory J Mazzaro, Andrew J Sherbondy, Matthew R Judy, Kyle A Gallagher

5d. PROJECT NUMBER

GTSPO#-17-123Mod1

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

US Army Research Laboratory

ATTN: RDRL-SER-U

2800 Powder Mill Road, Adelphi, MD 20783-1197

8. PERFORMING ORGANIZATION REPORT NUMBER

ARL-TR-8076

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12. DISTRIBUTION/AVAILABILITY STATEMENT

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13. SUPPLEMENTARY NOTES

14. ABSTRACT

Acoustic-electromagnetic (EM) interaction is evaluated for metallic and electronic target detection. The transmitter consists of 

a radar-wave generator emitting a single EM frequency and an acoustic-wave generator emitting a single acoustic frequency. 

The EM wave and the acoustic wave interact at the target. The target reradiates a new EM wave, which consists of the original 

EM wave modulated by the acoustic wave. This reradiated wave is captured by the radar’s receive antenna. The presence of 

measurable EM energy at any discrete multiple of the audio frequency away from the original radio-frequency (RF) carrier 

indicates target detection. Proof-of-concept detection is demonstrated for purely metallic and RF electronic targets within the 

near field of an ultra-wideband radar antenna operating in the ultra-high frequency band.

15. SUBJECT TERMS

radar, acoustic, electromagnetic, wave, interaction, modulation, detection, metallic, electronic, nonlinear, junction

16. SECURITY CLASSIFICATION OF:

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 ABSTRACT

UU

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 PAGES

26

19a. NAME OF RESPONSIBLE PERSON

Kelly D Sherbondy

a. REPORT

Unclassified

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Unclassified

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(301) 394-2533

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iii

Contents

List of Figures iv

1. Introduction 1

2. Acoustic-Electromagnetic Interaction 2

3. Near-Field Experiment and Data 5

4. Conclusions 9

5. References 10

Appendix. Code for an Example Program 13

List of Symbols, Abbreviations, and Acronyms 18

Distribution List 19
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iv

List of Figures

Fig. 1 Hybrid acoustic/EM technique for remotely detecting RF electronic 

targets: the transmitter consists of an EM-wave generator (antenna) 

and an acoustic-wave generator (speaker); a second antenna receives 

the EM wave modulated by the acoustic wave..................................... 2

Fig. 2 (a) Frequency modulation imparted onto the EM wave by translational 

motion (or compression/expansion) of the target and (b) time-domain 

reflected radar waveform and associated Fourier spectrum ................. 3

Fig. 3 (a) Amplitude modulation imparted onto the EM wave by intermittent 

contact of metal junctions within the target and (b) time-domain 

reflected radar waveform and associated Fourier spectrum ................. 4

Fig. 4 Flowchart of wireless experiment to receive acoustically modulated 

radar waveforms.................................................................................... 6

Fig. 5 Spectra recorded using the experiment of Fig. 4: the target is a metallic 

corner reflector, which measures 18 inches on each side. The thick 

(red) traces indicate that the target is present. The thin (black) traces 

indicate that the target is absent............................................................ 7

Fig. 6 Spectra recorded using the experiment of Fig. 4: the target is a hollow 

metallic circular cylinder with a diameter of 6 inches and a height of 8 

inches. The top of the cylinder faces the antenna. The top of the 

cylinder is held loosely to the body of the cylinder (i.e., there is a thin 

air gap between the top and the body around the perimeter of the top).7

Fig. 7 Spectra recorded using the experiment of Fig. 4: the target is a 

Motorola MD200R radio, upright and turned sideways to the antenna. 

The thick (red) traces indicate that the target is present. The thin 

(black) traces indicate that the target is absent. .................................... 8
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1

1. Introduction

Detection of radio-frequency (RF) electronics—targets whose radar cross sections 

(RCSs) are too small to be seen by traditional radar—has recently been investigated 

by implementing nonlinear (or “harmonic”) radar.1 This novel type of radar relies 

on the presence of electromagnetic (EM) nonlinearities in the target to convert EM 

energy incident on the target at an original set of frequencies into EM energy 

reradiated from the target at a new set of frequencies (e.g., harmonics). Reception 

of frequencies different from the original transmit set indicates target detection.

For nonlinear radar, the physical phenomenon that produces a measureable target 

response is purely EM. The radar generates an EM wave from its transmit antenna, 

the target is illuminated by a weaker copy of the transmitted EM wave, the target 

reradiates another EM wave, and the radar captures a weaker copy of the reradiated 

EM wave at its receive antenna. The conversion of the EM energy, from the 

illuminating waveform from an original frequency set into new EM energy 

reradiated at a new frequency set, occurs at the semiconductor and/or metal-tometal junctions2 in the target. These junctions distort the transmitted EM waveform 

into a new reradiated waveform, which contains Fourier components that were not 

part of the original transmission.

In this work, a different physical phenomenon is evaluated for target detection: the 

distortion of an EM wave caused by the interaction of an acoustic (audible, 

pressure) wave and the original (unmodulated) EM wave. The hybrid acoustic-EM 

technique is illustrated in Fig. 1. The radar transmitter (Tx) consists of an EM wave 

generator (i.e., a transmit antenna) emitting a single EM frequency fRF and an 

acoustic-wave generator (here depicted as a speaker) emitting a single acoustic 

frequency faudio . At the device under test (DUT), the EM wave and the acoustic 

wave interact. The target reradiates a new EM wave, which consists of the original 

EM wave modulated by the acoustic wave. The new EM wave contains a set of 

frequencies fRF ± n·faudio, where n is any positive integer. This reradiated wave is 

captured by the radar receiver (Rx). The presence of measurable EM energy at any 

discrete multiple of faudio away from the original RF carrier fRF (i.e., at any n ≠ 0 ) 

indicates target detection.
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2

TxRF

Rx

fRF

faudio

fRF ± n·faudio

Tx

DUT

audio

Fig. 1 Hybrid acoustic/EM technique for remotely detecting RF electronic targets: the 

transmitter consists of an EM-wave generator (antenna) and an acoustic-wave generator 

(speaker); a second antenna receives the EM wave modulated by the acoustic wave.

In this report, 2 ways in which acoustic and EM waves interact at targets of interest 

are described. Detection of canonical and purely metallic targets is performed by 

exploiting one type of acoustic-EM interaction. Detection of RF electronic targets 

is performed by exploiting a second type of acoustic-EM interaction.

2. Acoustic-Electromagnetic Interaction

There are 2 mechanisms described in the available literature by which acoustic 

waves interact with EM waves at metallic or electronic targets to generate new 

spectral content in a radar return. Considering the TxRF and Rx antennas to be the 

“original” radar system, the acoustic transmitter Txaudio can impart the modulation 

±n·faudio onto the original transmit/receive waveform by 2 fundamentally different 

physical phenomena: translational motion, which produces a Doppler shift (and 

harmonics of that shift) in the target reflection, and intermittent metal contact,

which interrupts the reflection like a switching transient.

Whether the acoustic wave from the speaker travels over the air or the wave couples 

into the target from the material around it, the acoustic energy vibrates (“shakes”) 

the target. For a target that is not necessarily a metal, vibration of its surface 

deforms the outer shell and compresses the inner material. As a result, the original 

RCS of the target is perturbed. The inner and outer perturbations may be modeled 

separately.

3 For metal and electronic targets, very little of the radar wave propagates 

into (and reflects from) the dielectrics beyond the conductors (or semiconductors); 

thus, only the perturbation of the outer shell (or circuit board) of the target is 

relevant. This perturbation is depicted in Fig. 2a.
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3

Fig. 2 (a) Frequency modulation imparted onto the EM wave by translational motion (or 

compression/expansion) of the target and (b) time-domain reflected radar waveform and 

associated Fourier spectrum

If the radar wave incident on the target is assumed to be a uniform plane wave and 

the acoustic wave incident on the target produces translational motion in the target, 

the electric-field intensity reflected by the target Erefl may be written as a sinusoid 

with a phase that is linearly dependent upon the target velocity toward the radar 

receiver.4 Thus, the modulation imparted onto the EM wave with carrier frequency 

fRF is entirely phase modulation.5

If the acoustic transmission is a steady tone, the surface of the target vibrates 

sinusoidally.

6 Since the time derivative of the phase of Erefl is generally nonzero, 

the perturbation imparted by the acoustic source on the target, as a result of moving 

the target toward and away from the radar receiver sinusoidally, is frequency 

modulation (FM).

In the Fourier domain, compared to unidirectional translational motion,7 sinusoidal 

motion produces a spectral spreading wider than that predicted by Doppler shift 

alone.8 This spreading extends both above and below fRF.

9

. Early measurements, 

using a 10-GHz radar and oscillating 6-inch metal discs, confirmed that the spectral 

peaks are indeed separated by ∆f = faudio.10 Since the perturbation of the radar return 

results in pure FM, the mathematics associated with FM used for radio 

communications applies, and in the frequency domain, Erefl may be written as a

series of Fourier components whose amplitudes are Bessel coefficients.11

The degree of modulation, and thus the total energy spread across the n ≠ 0 

sidebands, depends on the displacement of the target surface away from its initial 

(“unshaken”) position. Sample FM waveforms are shown in both the time and 

frequency domains in Fig. 2b.

uncompressed

or stationary

compressed or moving

away from radar fRF

fRF

fRF

fRF − n·faudio

Erefl

t

|Erefl|

f

fRF

fRF − 3faudio

fRF − faudio

fRF + faudio

fRF + 3faudio

fRF − 2faudio

fRF + 2faudio

fRF + 4faudio

fRF − 4faudio

fRF + 5faudio

fRF − 5faudio

Taudio

~

Taudio = faudio

_____ 1

(a) (b)
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4

The greatest Doppler shift occurs when a target moves directly toward or away 

from the radar. Therefore, with regard to target orientation, the components of Erefl 

are maximum when the target vibrates directly toward or away from the receiver.12 

The reflected response is further enhanced if the incident acoustic energy activates 

a mechanical resonance, which further displaces the target surface.13

Using this Doppler-based mechanical-EM interaction, a hybrid acoustic/radar 

sensor system was developed for detecting buried landmines.

14 The radar portion 

of the sensor transmits and receives at 8 GHz.

15 while the acoustic portion of the 

sensor transmits between 100 Hz and 1 kHz.16 The acoustic transducer is a 

mechanical shaker placed in contact with the surface of the material within which 

the target is buried.

17 To vibrate the target efficiently, the acoustic source needs to 

be placed within one acoustic wavelength of the material on/in which the target is 

buried; otherwise, the acoustic waves will propagate only along the surface of the 

burial material and not reach any appreciable depth.

16

Experiments have shown that acoustic resonances greatly improve the detectability 

of shallow-buried landmines.

18 Also, mines possess acoustic resonances, which 

clutter objects do not.

19 Both metallic and nonmetallic landmines are detectable 

down to a depth of at least 11 cm.

16 Detection is possible beneath rough surfaces as 

long as the acoustic spot size illuminating the rough surface is significantly greater 

than the cross-sectional area of the target.

20

A secondary effect of shaking the target, which can produce an even stronger return 

at higher-order sidebands (n > 1), is to cause intermittent contact between metal 

junctions within the target. This phenomenon is depicted in Fig. 3a.

Fig. 3 (a) Amplitude modulation imparted onto the EM wave by intermittent contact of 

metal junctions within the target and (b) time-domain reflected radar waveform and 

associated Fourier spectrum

most

junctions 

(dipoles) 

disconnected

fRF

fRF

fRF

most 

junctions 

(dipoles) 

connected

fRF

Erefl

t

|Erefl|

f

fRF

fRF − 3faudio

fRF − faudio

fRF + faudio

fRF + 3faudio

fRF − 2faudio

fRF + 2faudio

fRF + 4faudio

fRF − 4faudio

fRF + 5faudio

fRF − 5faudio

Taudio

~ Taudio = faudio

_____ 1

(a) (b)
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If a metal or electronic target vibrates while it is being illuminated by an EM wave, 

the reflected wave will contain not only a Doppler shift due to displacement of the 

target surface; the target will generate additional spectral content, which resembles 

noise.

21 Since this spectral content is centered on fRF and also occurs at intervals of 

∆f = faudio , it may be considered another form of modulation of the transmitted EM 

wave by the acoustic wave. This modulation may be described by the interruption 

of surface currents established along the target.

21 Such interruptions occur at a rate 

of faudio and may be modeled by time-varying surface impedances.

22

Alternatively, the acoustic modulation may be modeled by the periodic connection 

and disconnection of dipole antennas along the target surface; each dipole radiates 

at fRF.

21 Measurements on n ≠ 0 sidebands23 indicate that the dipole-antenna 

collection may be replaced by a single center-loaded conducting cylinder.24 

Multiple intermittent connections may be replaced by a single time-varying load 

impedance25 where the peak radar return occurs when the target (dipole) is shortcircuited.26 Mathematically, the intermittent contact may be described as a squarewave multiplication of the original EM wave.21 Thus, by vibrating the target to 

cause intermittent metal-metal contact, the modulation imparted onto the original 

(stationary-target) EM wave is amplitude modulation (AM).

A sample AM waveform is shown in Fig. 3b along with its corresponding Fourier 

spectrum. In this case, the degree of modulation depends on the difference between 

the minimum and maximum load impedance,26 which physically corresponds to the 

difference between the number of metal junctions that are connected versus those 

that are disconnected along/inside the target at any one time.

In the following section, an experiment is described, which confirms that metal and 

electronic targets of interest may be detected by exploiting either of the 2 

aforementioned acoustic-EM interactions.

3. Near-Field Experiment and Data

The experiment used to receive acoustically modulated radar waveforms from 

metal and electronic targets is shown as a flowchart in Fig 4.
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6

fRF

Tektronix

RSA-6114A

DUT

Prec

faudio

faudio

fiberglass

rod

Agilent

33220A

Keysight

N5171B

HP 778D-12

or HP 779D

LabWorks

PA-138

LabWorks

MT-161

Schwarzbeck 

BBHA-9120-E

Tx/Rx PRF

1 Vpp

–20 dB

2 ft

Fig. 4 Flowchart of wireless experiment to receive acoustically modulated radar 

waveforms.

The RF source is the Keysight N5171B analog signal generator. It outputs a 

continuous-wave (CW) signal at a frequency fRF and a constant power of 

PRF = –10 dBm. This CW transmit signal enters a Hewlett Packard (HP) directional 

coupler and passes on to the transmit antenna. For frequencies less than or equal to 

2 GHz, the coupler is the HP 778D-12. For frequencies greater than 2 GHz, the 

coupler is the HP 779D. The Schwarzbeck BBHA-9120-E horn antenna (oriented 

for vertical polarization) transmits fRF to the DUT. The distance between the 

antenna and the target is 2 ft. This short distance is within the near field of the 

antenna.

The DUT is attached to a 3-ft-long fiberglass rod using a pair of rare-earth magnets 

at the end of the rod. The other end of the fiberglass rod is attached to the LabWorks 

MT-161 modal test shaker. The shaker is powered by the LabWorks PA-138 

amplifier, into which is fed an audio-frequency signal at faudio provided by the 

Agilent 33220A function generator. The shaker vibrates the rod, and the rod 

vibrates the DUT. The EM wave reflected by the DUT (while it is illuminated by 

fRF and shaking at a frequency of faudio) is received by the same BBHA-9120-E 

antenna. The backward-traveling reflection is sampled (at –20 dB) by the 

directional coupler. The sampled Prec is sent from the coupled port to the Tektronix 

RSA-6114A spectrum analyzer.

Figures 5–7 contain spectra recorded for 3 different targets. The thick (red) traces 

are the target-present traces. The thin (black) traces are the target-absent traces. The 

upper pair of spectra correspond to fRF = 800 MHz, the lower pair correspond to 

fRF = 1000 MHz, the left pair correspond to faudio = 50 Hz, and the right pair 

correspond to faudio = 100 Hz .
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Fig. 5 Spectra recorded using the experiment of Fig. 4: the target is a metallic corner 

reflector, which measures 18 inches on each side. The thick (red) traces indicate that the target 

is present. The thin (black) traces indicate that the target is absent.

Fig. 6 Spectra recorded using the experiment of Fig. 4: the target is a hollow metallic 

circular cylinder with a diameter of 6 inches and a height of 8 inches. The top of the cylinder 

faces the antenna. The top of the cylinder is held loosely to the body of the cylinder (i.e., there 

is a thin air gap between the top and the body around the perimeter of the top).
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Fig. 7 Spectra recorded using the experiment of Fig. 4: the target is a Motorola MD200R 

radio, upright and turned sideways to the antenna. The thick (red) traces indicate that the 

target is present. The thin (black) traces indicate that the target is absent.

The RSA-6114A analyzer is configured to capture spectra centered at fRF with a 

bandwidth of 10faudio (i.e., such that sidebands out to n = ±5 are visible). The number 

of frequency points captured across each spectrum trace is 4001. The resolution 

bandwidth (per frequency point) is 3 Hz. The N5171B, 33220A, and RSA-6114A 

are controlled using a laptop, programmed in MATLAB using its Instrument 

Control toolbox and scripts written in Standard Commands for Programmable 

Instruments (SCPI) code. Communication between the laptop and the instruments 

is accomplished over a GPIB-USB interface. Code for an example program is 

provided in the Appendix.

Figure 5 contains 4 spectra recorded for a large metallic corner reflector. At all 4 

frequency combinations, the corner reflector is clearly (visibly) detectable above 

the noise because each target-present case contains ±n·faudio spikes, which do not 

appear in each target-absent trace. Figure 6 contains data recorded for a metallic 

cylinder. Only at fRF = 1,000 MHz and faudio = 50 Hz is there significant spectral 

energy that appears in the target-present trace that does not appear in the targetabsent case. Figure 7 contains data recorded for a handheld radio. At 3 out of the 4 

frequency combinations, the radio is detectable. At fRF = 1,000 MHz and 

faudio = 100 Hz , there is no significant difference between the target-present and 

target-absent traces.
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9

4. Conclusions

The interaction between acoustic and EM waves appears to be exploitable for 

detecting metallic and electronic radar targets. Data taken on 3 targets (a corner 

reflector, a metallic cylinder, and a handheld radio) indicate that EM waves are 

indeed modulated by acoustic waves at these targets of interest, for particular 

combinations of radar and acoustic frequencies (at ultra-high frequency and in the 

audible range, respectively). In a follow-up investigation, we will attempt to 

achieve target detection at a range of 10 ft, for a wider selection of targets 

illuminated by a wider range of frequencies.
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10

5. References

1. Mazzaro GJ, Martone AF, K. Ranney I, Narayanan RM. Nonlinear radar for 

finding RF electronics: System design and recent advancements. IEEE Trans 

Microw Theory Tech. 2017 May;65(5):1716–1726.

2. Origlio GF. The METRRA techniques. Ft Belvoir (VA): US Army Mobility 

Equipment Research and Development Center; 1972. AD522716.

3. Lawrence DE, Sarabandi K. Acoustic and electromagnetic wave interaction: 

Analytical formulation for acousto-electromagnetic scattering behavior of a 

dielectric cylinder. IEEE Trans Ant Propag. 2001 Oct;49(10):1382–1392.

4. Borkar SR, Yang RF H. Reflection of electromagnetic waves from oscillating 

surfaces. IEEE Trans Ant Propag. 1975 Jan;23(1):122–127.

5. Kleinman RE, Mack RB. Scattering by linearly vibrating objects. IEEE Trans 

Ant Propag. 1979 May;27(3):344–352.

6. Wetherington JM, Steer MB. Standoff acoustic modulation of radio frequency 

signals in a log-periodic dipole array antenna. IEEE Ant Wireless Propag Lett.

2012;(11):885–888.

7. De Zutter D. Doppler effect from a transmitter in translational motion. IEEE

J Microwaves, Opt Acoust. 1979 Mar;3(2): 85–92.

8. Kleinman RE. Electromagnetic scattering by a linearly oscillating target.

Hascom AFB (MA): Air Force Cambridge Research Laboratory; 1975 Oct.

Report No.: AFCRL-TR-75-0554.

9. Cooper J. Scattering of electromagnetic fields by a moving boundary: The onedimensional case. IEEE Trans Ant Propag. 1980 Nov;28(6):791–795.

10. Mack RB. Measured backscatter modulation from linearly oscillating metal 

disks. Griffiss AFB (NY): Rome Air Development Center; 1977 Aug. Report 

No.: RADC-TR-77-285.

11. Van Bladel J. De Zutter D. Reflections from linearly vibrating objects: Plane 

mirror at normal incidence. IEEE Trans Ant Propag. 1981 July;29(4):629–637.

12. De Zutter D. Reflections from linearly vibrating objects: Plane mirror at 

oblique incidence. IEEE Trans Ant Propag. 1982 Sept;30(5):898‒903.
Approved for public release; distribution is unlimited.

11

13. Sarabandi K, Lawrence DE. Acoustic and electromagnetic wave interaction: 

Estimation of doppler spectrum from an acoustically vibrated metallic circular 

cylinder. IEEE Trans Ant Propag. 2003 July;51(7):1499–1507.

14. Scott WR, Schroeder C, Martin JS. An acousto-electromagnetic sensor for 

locating land mines. In: Proc SPIE 3392; 1998 Apr. p. 176–186.

15. Scott WR, Schroeder C, and Martin JS. A hybrid acoustic/electromagnetic 

technique for locating land mines. In Proc Int Geosci Remote Sens. Symp;

1998 July. p. 216–218.

16. Scott WR, Larson GD, Martin JS. Simultaneous use of elastic and 

electromagnetic waves for the detection of buried land mines. In Proc SPIE 

4038; 2000 Apr. p. 667–678.

17. Scott WR, Martin JS. An experimental model of a acousto-electromagnetic 

sensor for detecting land mines. In Proc. IEEE Ant Propag Soc Int Symp; 1998

June. p. 978–981.

18. Scott WR, Martin JS. Experimental investigation of the acoustoelectromagnetic sensor for locating land mines. In Proc SPIE 3710; 1999 Apr. 

p. 204–214.

19. Scott WR, Martin JS, Larson GD. Investigation of a technique that uses elastic 

waves to detect buried land mines. In Proc Int Geosci Remote Sens Symp;

2000 July. p. 1640–1642.

20. Lawrence DE, Sarabandi K. Acousto-electromagnetic interaction in the 

detection of buried objects. In Proc Int Geosci Remote Sens Symp;

2001 July. p. 1989–1991.

21. Bahr AJ, Frank VR, Petro JP, Sweeney LE. Radar scattering from 

intermittently contacting metal targets. IEEE Trans. Ant Propag. 1977

July;25(4):512–518.

22. Lawrence DE, Sarabandi K. "Electromagnetic scattering from vibrating 

metallic objects using time-varying generalized impedance boundary 

conditions. In Proc IEEE Ant Propag Soc Int Symp; 2002 June. p. 782–785.

23. Bahr AJ, Petro JP. Frequency dependence of the modulated scattering from 

simple intermittently contacting metal targets. In Proc Ant Propag Soc Int 

Symp; 1977 June. p. 166–168.

24. Hu Y. Back-scattering cross section of a center-loaded cylindrical antenna. 

IRE Trans Ant Propag. 1958 Jan;6(1):140–148.
Approved for public release; distribution is unlimited.

12

25. FrankVR. Petro JP, BahrAJ. Backscattering from a cylindrical dipole centrally 

loaded by a time-varying impedance. IEEE Trans Ant Propag.

1977 May;25(3):356–358.

26. Bahr AJ. Petro JP. On the RF frequency dependence of the scattered spectral 

energy produced by intermittent contacts among elements of a target. IEEE 

Trans Ant Propag. 1978 July;26(4):618–621.
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13

Appendix. Code for an Example Program
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14

Provided in this Appendix is a MATLAB script, which uses the Instrument Control 

toolbox to configure the signal generation and capture equipment in Fig. 4. The 

output from the script is a power-versus-frequency plot in the style of Figs. 5–7.

freq_RF = 800e6; % radio frequency

pwr_RF_dBm = -10;

freq_audio = 100; % audio frequency

Vpp_audio = 1.0;

res_bw = 3; % spectrum analyzer

freq_span = freq_audio * 10; % settings

freq_pts = 4001;

hold_count = 10;

yscale_ref = -15;

yscale_offset = -40;

yscale_dB = 100;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% configure Keysight N5171B signal generator %%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

exg = gpib('ni', 0, 19);

fopen(exg);

fwrite(exg,['OUTPut:MODulation:STATe OFF']);

fwrite(exg,['POWER ' num2str(pwr_RF_dBm) 'dBm']);

fwrite(exg,['FREQ ' num2str(freq_RF) 'Hz']);

fwrite(exg,['OUTPut:STATe ON']);

fclose(exg);

pause(0.5)
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15

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% configure Agilent 33220A function generator %%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

awg = gpib('ni', 0, 10);

set(awg,'OutputBufferSize',2^18);

set(awg,'Timeout',40.0);

fopen(awg);

fprintf(awg, ['FUNCtion SINusoid']);

fprintf(awg, ['FREQuency ' num2str(freq_audio)]);

fprintf(awg, ['VOLTage ' num2str(Vpp_audio)]);

fprintf(awg, ['OUTPut ON']);

fclose(awg);

pause(0.5);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% configure Tektronix RSA-6114A spectrum analyzer %%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

sa = gpib('ni', 0, 1);

set(sa,'InputBufferSize',2^20);

set(sa,'Timeout',20);

fopen(sa);

fprintf(sa,['SENSE:SPECTRUM:BANDWIDTH:RESOLUTION ' num2str(res_bw) 

'Hz']);

fprintf(sa,['SENSE:SPECTRUM:FREQUENCY:CENTER ' num2str(freq_RF) 

'Hz']);

fprintf(sa,['SENSE:SPECTRUM:FREQUENCY:SPAN ' num2str(freq_span) 

'Hz']);

fprintf(sa,['SENSE:SPECTRUM:POINTS:COUNT P' num2str(freq_pts)]);

fprintf(sa,['INPUT:RLEVEL ' num2str(yscale_ref)]);
Approved for public release; distribution is unlimited.

16

fprintf(sa,['DISPLAY:SPECTRUM:Y:SCALE:OFFSET ' 

num2str(yscale_offset)]);

fprintf(sa,['DISPLAY:SPECTRUM:Y:SCALE ' num2str(yscale_dB)]);

fprintf(sa,['INITIATE:CONTINUOUS OFF']);

fprintf(sa,['TRACE1:SPECTRUM:FUNCTION AVERage']);

fprintf(sa,['TRACE1:SPECtrum:AVERage:COUNt ' 

num2str(hold_count)]);

fprintf(sa,['TRACE1:SPECtrum:AVERage:RESet']);

fprintf(sa,['INITIATE:IMMEDIATE']);

fprintf(sa,'READ:SPECtrum:TRACe1?');

char(fread(sa,1));

ndig = str2double(char(fread(sa,1))); 

nbytes = str2double(char(fread(sa,ndig))'); 

P_rec = (fread(sa,nbytes/4,'single'))';

fprintf(sa,['INITIATE:CONTINUOUS ON']);

fprintf(sa,['TRACE1:SPECTRUM:FUNCTION NONE']);

fprintf(sa,['INITIATE:IMMEDIATE']);

fclose(sa);

pause(0.5);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% turn N5171B and 33220A outputs off %%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

fopen(awg);

fprintf(awg, ['OUTPut OFF']);

fclose(awg);
Approved for public release; distribution is unlimited.

17

fopen(exg);

fwrite(exg,['OUTPut:STATe OFF']);

fclose(exg);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% plot spectrum recorded by RSA-6114A %%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

delta_f = freq_span / (freq_pts-1);

f_start = freq_RF - freq_span/2;

f_end = freq_RF + freq_span/2;

freq = f_start:delta_f:f_end;

figure

plot(freq-freq_RF,P_rec)

axis([-Inf -140 0])

ylabel('Received Power, {\itP}_{rec} (dBm)')

xlabel('Frequency Offset from Carrier (Hz)')

grid
Approved for public release; distribution is unlimited.

18

List of Symbols, Abbreviations, and Acronyms

AM amplitude modulation

CW continuous-wave

DUT device under test 

EM electromagnetic 

FM frequency modulation

HP Hewlett Packard 

RCS radar cross section 

RF radio frequency 

Rx radar receiver

SCPI Standard Commands for Programmable Instruments 

Tx radar transmitter

USB universal serial bus
Approved for public release; distribution is unlimited.

19

1 DEFENSE TECHNICAL

(PDF) INFORMATION CTR

DTIC OCA

2 DIRECTOR

(PDF) US ARMY RESEARCH LAB

RDRL CIO L

IMAL HRA MAIL & RECORDS

MGMT

1 GOVT PRINTG OFC

(PDF) A MALHOTRA

8 DIRECTOR

(PDF) US ARMY RESEARCH LAB

RDRL SER U

K GALLAGHER

M JUDY

A MARTONE

G MAZZARO

K RANNEY

A SHERBONDY

K SHERBONDY

A SULLIVAN
Approved for public release; distribution is unlimited.

20

INTENTIONALLY LEFT BLANK.