LEVEL i

tECHNICAL REPORT RE-81-13

RADAR ANALYSIS AND TEST

OF A BULLET HIT INDICATOR

"R. Russell, R. Garlough, F. Sedenquist, J. Cole

Advanced Sensors Directorate

US Army Missile Laboratory

DTICS ELECTEOCT 1 9 1981

June 1981

Approved for public release; dstrributlon unlimited.

C-,

LAJ

.7.

SIM FOIW 10211, 1 JUL 7I PREVIOUS EDITION II ONOLETE

DISPOSITION INSTRUCTIONS

DESTROY THIS REPORT WHEN IT I NO LONGER NEEDED. 00 NOTRETURN IT TO THE ORIGINATOR.

DISCLAIMER

THE FINDINGS IN THIS REPORT ARE NOT TO S1 CONSTRUED AS AN

OFFICIAL DEPARTMENT OF THE ARMY POSITION UNLESS SO 02210.NATED BY OTHER AUTHORIZED DOCUMENTS.

TRADE NAMES

WE OF TRADE MAMES o0 MANUFACTURERS IN THIS REPORT oo15NOT CONSTITUTE AN OFFICIAL INDONSIMINT OR APPROVAL OPTHE UBE OF SUCH COMMERCIAL HARDWARE OR $OFOrWARE.

SECURITY CAM 918TWO$ PAGE (When Date ftaeim

6. PERFORMING ONO. REPORT NUMSER

7 AUTHOR(s) $. CONTRA TOR GRANT NUMNER(a)R. Russell, R. Garlough, F. Sedenquist, J. Cole

9. PERFORMING ORGANIZATION NAME AND ADDRESS IT0. PROGRAM U. mlT., PRJI.CT TASKCommander, US Army Missile Command ARE AM " ORNIT rUMUE

ATTN: DRSMI-RDRedstone Arsenal, AL 35898

11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DAIECommander, US Army Missile Command June 1981ATTN: DRSMI-RPT 1S. NUMUER OF PAGESRedstone Arsenal, AL 35898 208

14. tAONITORING AGeNCY NAME & AODR5S51(i ll. dffeet In Contoin~g 01fiva) 1S. SECURITY CLASS. (of Ole1 ,.port)

UnclassifiedI

Is*. DECkLS IAON DOWNGRADING

IS. DISTRIOUTION STA-TSMENT (of.1 fflettpo)Approved for public release; distribution unlimited.

1S. SUPPLEMENTARY NOTESI

iS. Key woRos (consinut an tetet..sid .it notee~wv md iduutity &Y biasit minbet)

Bullet hit indicatorRadar systemBullet detection system

24L AOThAC1 bfw (C nim oeevemsaf W nmamsw .d hl*wif by 68eek numn&.t

This report presents theoretical analysis and data analysis pertaining to testsperformed by Cartwright Engineering Incorporated during the week of 17 November1980 at Test Area 1, Redstone Arsenal, Alabama

Do D i 0 1C m7 3 EornOW or P Nov ess's osw.uru UNCLASSIFIED

SICCU~hY CLAWF ICATION OF TWIS PAGE (Nb.' Data vner,.d))

U

CONTENTS

page

I. INTRODUCTION ................. ... .......................... 3

II. TEST DESCRIPTION............. ....................... . . 3

III. RADAR SYSTEK ANALYSIS . .................... 5 .5

IV. BULLET RADAR CROSS-SECTION ANALYSIS ...... ................ 8

V. DATA ACQUISITION AND PROCESSING ..... ............... ..... 21

VI. DATA ........... ..... .............................. ... 21

VII. DATA ANALYSIS .......... ......................... 23

VIII. CONCLUSIONS AND RECOMMENDATIONS ...... ................ ... 27

APPENDIX ....... ........................... 31

Acaession For

NTIlS __GRA&IDTIC TAB UUnannouncedJustification

Distribution/ .Availability Ccdva

Avnil cind/or

II

I

tI4.a-

I. INTRODUCTION

The purpose of this document is to present theoretical analysis, anddata analysis pertaining to tests performed by Cartwright Engineering Incor-porated, 251 E. Palais Road, Anaheim, California 92805, during the week of17 November 1980 at Test Area 1, Redstone Arsenal, Alabama. The unit undertest was a brassboard Bullet Detection System (BDS). The BDS is intended tobe used as a target scoring device f r 20-millimeter projectiles. The testswere performed under the Phase II req irement of ESM 1653-3G Statement ofWork, Attachment A, to Contract DAAH01 QQC-0012.

In this document, references toith. contractor refer to Cartwright

Engineering Incorporated.

Data reduction, data analysis, and theoretical analysis were performedby Mr. R. F. Russell, Group Leader, Mr. R. Ii. Garlough, Mr. F. W. Sedenquist,and Mr. J. S. Cole of the Land Comba Group, RF Guidance Technology, AdvancedSensors Directorate, US Army Missile Laboratory, US Army Missile Command,Redstone Arsenal, Alabama.

Compilation of this document was performed by Mr. Garlough. Data wasrecorded using US Army equipment located at Test Area 1 by Test and EvaluationDirectorate personnel.

II. TEST DESCRIPTION

The following test description is excerpted from the contractor's finalreport, reference CEI-BDS-FTR, dated 18 December 1980. Those parts of thecontractor's report which reference parts of that report are deleted.

"A CEI Model GRS-IL Ground Receiving Station was used to receive,process, display, and record the scoring data from the BDS. AA 151S.5-MHz telemetry link was used between the BDS and receivingstation. (Reference deleted.)

"The object of the BDS tests conducted at Redstone Arsenal was todemonstrate the feasibility of a scoring technique at 3.245 GHzduring static firing tests. All test firings were conducted withthe BDS suspended a minimum of 20 feet above ground level with thehorn antenna pointed vertically. The 900 test shots were firedwith ranges between S to 55 feet above the horn antenna. Thistest setup deviated from the Performance Test Plan (CEI-BS-PTP)because the 20-mm gun was more easily and accurately moved inelevation. Moving the gun in azimuth would have been considerablymore difficult and time consuming.

"The test firings were conducted over a three-day period beginningoi Tuesday, November 18, 1980 and ending Thrusday, November 20,1980. A total of 53 test rounds were fired at varying angles of00, 450, 900, 1350 and 1800, and at varying ranges of S to 55 feet.

"On Tuesday, 11 test rounds were fired to check out the system.All rounds fired were at 900 (horn antenna pointed vertically)

14 3

and with ranges varying between 5 to 50 feet. The BDS exhibiteda problem in that excessive noise was noted on the sensor output.The problem was corrected by realigning the timing between thetransmitter and receiver pulses. (References deleted.)

"With the sensor readjusted, the tests were continued on Wednesdaywith 23 test rounds being fired (rounds 12 through 34)."(References deleted.) "Rounds 12 through 23 were conducted at 900with ranges of 45, S0, 52, 55, 40, 35, 30, 25, 20, 15, 10, and Sfeet respectively. The ground receiving station counted all roundscorrectly except for the round at the 55-foot ragne which was out-side of the range of the system.

"Rounds 24 and 25 were fired with the antenna at 00 orientation(horn antenna pointed directly towards the gun) and at ranges ofS feet and 10 feet above the antenna. The BDS started to exhibitexcessive noise and deteriorating signal level again, and this Aproblem persisted the remainder of the day. The round at 5 feetwas counted; the round at 10 feet was not counted. The failure Ato score at 10 feet was primarily caused by the reduced radarcross-section at this orientation and the reduced response fromthe projectile passing through the edge of the scoring antennapattern. ]

"Rounds 26, 27, and 28 were fired with an watenna orientation of1800 (horn antenna pointed directly away from the gun) at a rangeof 5 feet. These three rounds were not counted due to the re-curting BDS noise problem.

"Rounds 29 through 34 were fired with antenna orientation of 450(horn antenna pointed towards the gun and elevated at 450 atranges of 5, 10, 20, 30, 40, and 25 feet respectively. All rou:-.were counted except for the rounds at 30 and 40 feet.

"On Thrusday, 19 rounds were fired (rounds 35 through 53).(References deleted.) With the BDS operating properly, rounds 35through 40 were fired with an antenna orientation of 00 (horn an-tenna pointed directly towards the gun). Rounds 35 through 38were fired at a range of 3 feet under the antenna, round 39 at Sfeet under the antenna, and round 40 at 10 feet above the antenna.All rounds were counted on the ground station except round 40 ata range of 10 feet, which again was at the edge of the scoringpatterns.

"Rounds 41 through 47 were fired with an antenna orientation of450 (horn antenna pointed towards the gun and elevated at 450 atranges of 5, 10, 20, 25, 30, 35, and 40 feet respectively). Allrounds were counted except round 47 at 40 feet, which is theeffective range limit for this reduced radar cross-section at a450 aspect angle. In this orientation, the projectile passes thecenter of the scoring pattern at a distance of .57 feet (40 ft/cos450), which is outside of the scoring range of the system.

4

I

"Rounds 48 through 51 were fired with an antenna orientationof 1350 (horn antenna pointed away from the gun and elevated at450 and ranges of 5, 10, and 20 feet respectively). Startingwith rounct 48, the noise level from the BDS began to increasewith a decrease of signal level. All rounds were counted exceptround 51 at 20 feet.

"Rounds 52 and 53 were fired with an antenna orientation of 1800(antenna pointed directly away from gun). at ranges of 3 feet and5 feet under the RIDS. Rounds 52 and 53 were not counted due to thedegrading doppler signal-to-noise ratio from the BDS."

III. RADAR SYSTEM ANALYSIS

Radar performance can be evaluated from the simple form of the radarequation.

P2

Pr 3

(4w) AR4 Ls

where

Pr is power received

Pt is power transmitted

G is antenna gain

X is radar wavelength

R is range to target

a is radar cross section

Ls is system losses

Power received, Pr , can be expressed as a function of the signal-to-noise ratio (S/N).

Pr = KTBF (S/N)

where

K is Boltzsmann's constant 1.38 x 10-23

T is temperature degrees Kelvin 2900

B is receiver bandwidth

F is noise figure of the receiver

5

Substituting one equation into the other results in a more convenientform of the radar equation that evaluates signal-to-noise ratio of thereceiver for given radar parameters.

PtG2X2 o

(4w) 3R4 KTBFLs

In analyzing radar performance, it is convenient to assume that theradar and target are both in free space. This case is allowed the freedom todo so because of the relative low frequency and the extremely short rangesinvolved.

The attenuation constant, a, at 3 GHz is less than 0.01 dB/km so overthe fifty-foot range of this radar the attenuation constant is less than onethousand of a dB.

The radar parameters of the Bullet Detection System Model BDS, asobtained from the contractor, are given in the following table.

TABLE 1. RADAR PARAMETERS

NAME SYMBOL VALUE dB VALUE

Power Transmitted Pt 3 Watts 4.77 dBwAntenna Gain G 6.31 8 dBWavelength X 0.0924 Meters -10.34 dBRadar Cross o 0.02145 Meters -16.7 dBSection* square

Bandwidth B 100 MHz 80 dBNoise Figure F 3.162 S dBSystem Losses L s i0.0 10 dB

*See Section IV. BULLET RADAR CROSS SECTION ANALYSIS

An example radar signal calculation for a 900 firing at 50 feet is shown

compared to the signal received on round number 13 which was a 900 firing at

50 feet.

S/N = = 12.1 dB(41r) R 4KTBFLs

The ratio of the signal and noise voltages measured for Round 13 onFigure 1 is approximately 33:6. Therefore, the signal-to-noise ratio mea-sured for Round 13 is

S/N measured - 20 logl 0 33/6 = 14.8 dB

which is very near the signal-to-noise from the radar parameters given.

6

ILCC.

ILW

Another example is when the bullet is fired at an angle of zero degreerelative to the radar (head-on). In this case the bullet cross section isreduced by 11 dB according to the contractor.

pcG2 X2 o

S/N = =1.1 dB(4t) 3R 4KTBFL5

However, the radar cross-section of a head on bullet is in the so-calledRayleigh region or law, and has a radius-to-wavelength ratio of approximately0.1. In this region, the radar cross-section is equal to the optical cross-section.

2 -a = ia = 3.14 x 10-4 meters square

This converts to dB as

a = -35.03dB,

which is 18.33 dB down from the calculated and assummed radar cross-section at900. Therefore, assumming the end-on head-on radar cross-section to be -35.03dB results in the following signal-to-noise calculation at 50 feet range.

P G2 X2 oS/N 3= -6.2 dB

(4) 3 R4 KTBFL

This level of signal-to-noise will make head-on and end-on detection verydifficult even though the bullet may pass closer than fifty feet. Passing at5 feet will increase the signal-to-noise by nearly 40 dB over the S0-footcase. However, the STC calculated would reduce this gain value to 10 dB,resulting in a S/N at 5 feet of + 4 dB which makes head-on automatic detectionquestionable. In this case, the zero doppler or zero crossing occurs out-side the main beam of the antenna.

IV. BULLET RADAR CROSS-SECTION ANALYSIS

In order to predict the signal-to-noise ratio of the radar receiver,some means of determining the radar cross-section of the 20-mm projectile isneeded. Figure 2 shows that the length L, of the projectile is 9.3 cm andthe radius, r, is 1 cm. The radar wavelength is 9.24 cm. According to Kerr Ill](see Figure 3), for r/X near 0.1 (Mie or resonance region), the higher ordermultiple moments fluctuate in phase and magnitude in a complicated way,causing the radar backscatter curve to oscillate. As r/X becomes very large,the oscillations diminish much like sin X/X until the radar cross-section be-comes the geometrical cross-section. Predicting the radar cross-section ofsimply shaped bodies in this region is very difficult at best, and for morecomplex shapes is beyond the scope of this effort. For this reason, threedifferent methods have been used to develop a radar cross-section model ofthe 20-rn projectile.

8

IIS-- %3 em

I e

Figure 2. Outline draw'ing of 20-mm projectile.

k5z E

S- 8 90°D IPO L E

inckknt

I m

6.'.

Figue 3 Scaterng gomery or aful wav diole

k~c~ds9

The first method assumes the projectile acts as a full wave dipole.This assumption is based on X a 9.24 and L - 9.30 cm. Figure 4 is a plot ofthe radar cross-section of a full wave dipole as a function of aspect angle.The null at broadside occurs because the model assumes an infinite thinnessfor the dipole.

The second method involves frequency scaling of radar cross-section dataof an artillery shell which has approximately the same L/r ratio and generalshape as the 20-mm projectile. Figure 5 shows the artillery shell and pro-jectile. (The figures are not to the same scale).

The third method utilizes a computer program to decompose the projectileinto a collection of evenly spaced concentric wire rings. The radar cross-section of the projectile is determined by summing each ring's contribution tothe total backscatter using the method of modes.

A. The 20-mm projectile as a full wave dipole

The assumption is made that at f = 3.245 GHz, the projectile will actas a full wave dipole.

L = 9.3 cm (Length of projectile)

f = 3.245 cm

= c c = Propagation velocityf

(3xlO8 m/sec) (100 cm/n)

3.245 x 109 Hz

X= 9.14 cm

L= X

From Ruck the full wave dipole backscattering cross-section is given by:

-0.93N 2 Cos 6i Cos 2__s i n(Tsif ui) s 2 in (vsin As,2

Los 2 ý IL cos 2 q s

where

6i = Polarization angle, incident plane

6s = Polarization angle, scattering plane

i= Aspect angle, incident plane

s= Aspect angle, scattering plane

10

- -' - -. � � -� � � '.--'---------- - -

- �

r

II

_______________________ _______________________________________________________________________

I

4)

00.".4*0

U.i

0 'IU4)0

000Id

U

I I0,

�wmqp� NOLL�IB 3SO� �iVOVH

11

a.

Ii* 4

b.

Figure 5. (a) 20-,ina projectile and (b) artillery shellused for scale modelling.

For the backscattering only case:

•, *i * 's * * - angle between a line normal to the dipolelongitudinal axis and the r&dar.

Sp varies between -900 and 900.

Rewriting (Equation 1) yields:

o u 0.93X cos64 - ----

Figure 4 is a plot of this equation for X a 9.245 cm. (Polarizationparallel to the length of the dipole or • = 00.) t•axima radar cross-sectionoccurs at i a +55*. This equation models a thin dipole with a sinusoidal cur-rent distributTon along the length and zero current at the ends. It assumeszero transverse crossectional area, hence the broadside return is zero.Singularities exist at ' a +900 and • - 00 so the model is valid only in theregion bounded by V. +80("o +50°

B. Radar cross-section of 20-mm projectile from scale model

Using data taken on an artillery shell and standard scale modelingtechniques, a plot of projectile radar cross-section versus aspect angle wasdeveloped. The raw data consisted of plots of the artillery shell RCS vsaspect angle for horizontal and vertical polarization. Pseudo circularpolarization data was developed by vectorially adding the horizontal and ver-tical raw data. Frequency scaling techniques were applied to yield the radarcross-section of a 20-mm projectile at 3.245 GHz for circular polarization,

Figures 6 and 7 are the artillery shell plots and Figure 8 is the 20-mm radarcross-section plot.

C. Radar cross-section of 20-mm projectile by computer modeling

Figures 9 and 10 are computer model plots of the projectile radar

cross-section versus aspect angle for horizontal and vertical polarization.The horizontal plot corresponds to the t parallel to the longitudinal axis ofthe projectile. Nose-on occurs at 0 degrees and broadside at 90 degrees.Figure 11 is the result of voctorially adding the two plots to simulate cir-cular polarization.

D. Figure 12 is a comparison of the results obtained by computer andscale modeling. The 5-dB difference at broadside can be attributed to reso-nance effects for which the computer model does not compensate. (See dipolelot, Figure 4, for resonance effect contribution to radar cross-section.)or * (aspect angle) r +25°, the projectile cross-section approximates that

of a half-wave dipole. -The 16 dB drop (from scale model curve) between broad-side and nose-on is in agreement with the data provided by the contractor. Thecontractor assumed the projectile acted like a half-wave dipole plus 4 dB atbroadside with an ll-dB drop from broadside to end-on. The nulls at approxi-mately +300 were not predicted by the contractors.

13

41

.4)4j

'IA

'I

(A

lob

(Mum Ollol Mwomvo0 14I

Li

4-d

t IA II

IL~Og ImI Moly$WOi~

154

4--

0

z4

(UM"

16

.44-

Iwq~ lt~lonIll l~i~lt "-

0,I,

14.

k2

f-II*- '-I

0- ad

40

la

"C4

El3,.

0 iCIO

(WAD) SW

17

*14

IV'

40

18.

1wIrc

-On

"4

400

cc

0)

"4

(Um" NOJ03 O* dv

19'*

I *10

U U

IW

200

I|L

V. DATA ACQUISITION AND PROCESSING

The data plots shown in this document were produced by the techniquesdescribed below.

Analog signals from the radar receiver of the system under test weretransmitted via the system's telemetry transmitter to the telemetry receiver.The output signals from the telemetry receiver were recorded on magnetic tape.

The tape recorder was operated at 60 inches per second for recording.The tapes were played back at 15 inches per second. During playback, thesignal from the tape recorder was sampled at 25 kilohertz, amplified andfiltered through a 10-KHz low-pass filter. Since the playback speed of therecorder was reduced by a factor of 4, the equivalent sampling rate was 100 KHzand the equivalent bandwidth of the low pass filter was 40 KHz to real-time.

The signal samples were stored in a computer memory and then recordedon digital magnetic tape. The digital magnetic tape records were then readback into the computer. In the computer the records were sorted, expanded timewise, amplified, etc., to produce the most meaningful data. These data werethen plotted on the computer display console and hard copies produced. Threeplots (or more) of each round fired are presented in the Appendix. One plotwith 4000 samples, 2000 samples, and one plot with 800 samples, for each roundare shown.

Some of the deviations from smooth curve representation on the plots aredue to sampling rate versus signal frequency. Figure 13 is an example ofdeviations from a smooth curve.

The three different numbers of samples plotted facilitate investigationof various parameters of the signals, e.g., the 4000-sample plots reveal thebackground noise before and after the doppler pattern and the expanded sampleplots (fewer number of points) show the characteristics of the doppler pattern.

Processing of the data, from playback of the analog tapes to the hardcopy plots, was performed by the RF Guidance Technology Data Analysis Facility,US Army Missile Command, Redstone Arsenal, Alabama.

VI. DATA

The data plots are presented in the Appendix. The data are plotted onthree different scales, 4000, 20C0, and 800 points per plot. The data wereacquired at an equivalent rate of 100,000 points per second or 10 usec perpoint. Therefore, a 4000 point plot is 40 msec long, a 2000 point plot is20 msec long and an 800 point plot is 8 msec long. The plots are convenientlytick marked both on X and Y axis at 10 percent points to facilitate easy inter-polation. Since no calibration was provided, amplitudes are relative ratherthan absolute; however, all plots are the same amplitude scale. In somecases, the pertinent data straddles two digital tape records; in these casesthere are presented more than 3 plots per round.

"The round number is presented at the top of the plot along with the date-time group. The sample number limits are given at the bottom of the plot sothat the number of points plotted can be easily identified.

21

4.1

zC

0 Im0

P-*4

A 4,

U. '.

22C

Excerpts from the contractors test logs are presented in the appendix.These excerpts contain the pertinent information about the specific roundfired: round number, range, angle, and remarks.

VII. DATA ANALYSIS

A. Signal-to-Noise Ratio

The signal-to-noise ratio expected is presented in the Radar SystemAnalysis section of this document. The data presented herein supports thetheoretical S/N ratio calculated.

Refer to data plots and test logs. Measure the amplitudes of the signaland noise shown in the data plots. Compare the signal-to-noise ratios of countand no-count rounds. Compute 20 x log1 0 (S/N) for count and no-count rounds.

All rounds which produced S/N ratios of 13 dB or more produced a count exceptround 32.

Round 32 data does not support a no-count condition. On this round, thebackground noise level is higher than normal but the S/N ratio is stillgreater than 1S dB.

Round 46 data indicates that a no-count should have occurred; however,count did occur. The S/N ratio on this round was approximately 8 dB.

Figure 14 shows a scenario of a projectile fired parallel to boresightas with round 39. Note that ze- . leppler occurs in the null 90 degrees fromboresight in the antenna patte-. -,e entire radar return is weak dueto poor aspect angle (minimum -iection) as the projectile approaches theantenna. As the cross-section .jves, the antenna pattern causes a null insignal strength. Hence, the zero doppler portion of the plot is obscured innoise.

B. Sensitivity Time Constant (STC) Curve

The STC curve, Figure 15 was plotted using the following technique.Since no calibration was provided, all values are normalized rather than usingabsolute values.

The theoretical signal strength decreases as the 4th power of range. SeeFigure 16. The relative signal strength as a function of range of 10 timesloglo of the reciprocal of the 4th power of range (in meters). The signal

strengths indicated are for ranges 5 through 55 feet in steps of S feet, allwere broadside. Since an ideal STC curve would produce a straight linesignal strength curve, an equation was generated to produce the line shown(labeled MEASURED) on the plot Figure 16. The STC attenuation curve was thenproduced by subtracting the straight line signal strength curve from thenormalized theoretical signal strength curve. The relative STC curve as afunction of range (or time) is shown in Figure 15.

23

LL&1

80

06

00 1.0

wlN 0

00

-ý4

24-

.55

IN'

255

_ _ _ _ _- , *J -- -

I .

I I. - . . -

.4.

Ln IK

--

1 "

.101

II'0

± i

(94l) H O U RS•ll 16l 1915

26

II I I I I I11111 "I IIN!i ]l il III l :1 1 +' •

C. Doppler Frequency

The doppler frequency can be calculated by counting the number ofsamples per doppler signal cycle. The number of samples is shown at the bottomof each plot. The effective saepling rate is 100K samples per second.

Refer to Figure 13. Approximately 49 samples were taken during 8 cyclesof doppler. This is 6.13 samples per cycle; therefore, the doppler frequencyis approximately 100K samples divided by 6.13 samples which equals to 16.31 KHz.

The calculations can be further extended to determine the velocity ofthe round relative to the antenna. Doppler frequency is equal to 2 x velocitydivided by wavelength of the radar frequency. The wavelength used in this sys-tem is 9.245 cm or 0.09245 meters. Wavelength is calculated by dividing thespeed of propagation of radar, 300,000,000 meters per second, by the radar fre-quency 3.24S GHz. The velocity of the projectile is equal to one-half thefrequency of the doppler multiplied by the wavelength of the radar signal whichis in this case 754 meters per second (2473 feet per second).

D. Data Anomalies

During the tests, noise levels shown on the plots were not consis-tent. Some of these inconsistencies were explained by the contractor as causedby equipment malfunctions.

The 90-degree plots show assymetrical amplitude responses, i.e., theamplitude of the doppler signal is greater after zero doppler than before zerodoppler. This phenomenon and some reoccurring cyclic noise after some roundpassings appear to be caused by ringing in the system. These phenomena werenot explained by the contractor.

The 45-degree plots show an amplitude build-up, an amplitude null, thenanother amplitude build-up prior to zero doppler. The null phenomenon cannotbe explained as due to antenna pattern alone. One possible explanation isthat as the aspect angle of the projectile changes, the amplitude of theradar return changes. See Section IV (BULLET RADAR CROSS SECTION). The onlysignificant nulls in the antenna pattern occur at the 90-degree off boresightpositions. Figure 17 shows the 45 degree scenario of rounds 30 and 42 as theypass through a theoretical antenna pattern. The antenna pattern provided bythe contractor is shown in Figure 18.

VIII. CONCLUSIONS AND RECOMMENDATIONS

The unit tested was capable of detecting projectiles passing atvarious angles. Best performance was when the projectile passed normal (900)to antenna boresight. The range gate was adjusted to count projectiles passingwithin S to 50 feet and excluded counting projectiles passing outside theselimits. Reliability of counting all projectiles passing within these limitsis good but not excellent when the projectile passes normal to antenna bore-sight. For projectiles passing 450 to antenna boresight, no round passing ata distance greater than 35 feet was counted. At ranges of 35 feet and less,there was a tendency to register multiple counts for a single projectile. Noprojectile fired at 1800 (from the rear) to antenna boresight was counted.

27

".0p04

Io

lid,

GaJ

ti

rM

no Ti

Sloe.

AZJ200 OU C ER I A

ELEvMI~TN CUT SOURCE HORTIZOCAL --

Figre 8.PrI-1ina, radiation pattern Of 3.24S GHz 'Coring *t~,L2

Projectiles fired at 00 (head-on) passing at 3 and S feet were counted;however, multiple counts of a single projectile were registered at 3 feet. At1350, projectiles at S and 10 feet were counted; none were counted at distancesgreater than 10 feet.

Analysis of data results in a conclusion that detection of a passingprojectile is based on doppler amplitude and not doppler zero frequency.Detection criteria based on doppler amplitude would account for the multiplecounts.

Information pertinent to detection criteria and processing technique wasrequested from the contractor, but this information was not received. Lack ofthis information precludes analysis of detection and processing methods.Recommend that this information be obtained from the contractor for analysisby Army personnel. -

The ability to count multiple projectiles was not demonstrated. Recommendthat the capability of counting multiple projectiles at 7200 rounds perminute be demonstrated.

Some data plots show assysitrical data on projectiles passing normal(900) to antenna boresight. The assymetry is in the form of higher amplitudeon the trailing pattern, after doppler zero, than on the leading pattern.This assymetry and cyclic noise patterns following doppler pattern on someplots appear to be caused by circuit ringing. Whether or not the ringingphenomenon degrades to system should be Investigated.

The apparent noise level. are different on some plots. Recommend thatstability tests be run •nh verified for temperatuire, humidity, and vibration.

30

APPENDIX

This appendix presents excerpts from the contractor's test logs

and plots of the data acquired during the Bullet Hit Indicator tests of

November 1980.

r

31

EXCERPTS FROM CONTRACTOR TEST LOGS

Round Range Angle Remarks

Number (feet) (Degrees)

1 30 90 Count 1

2 25 90 Count 1

3 20 90 Count i

49u4 15 90 Count 1

5 10 90 Count 1

6 5 90 Count 1

7 35 90 Count 1

8 40 90 No Count I9 35 90 Countl

10 45 90 No Count 411 50 90 No Count 1

12 45 90 Count 1

13 50 90 Count 1i

14 52 90 Count 1

15 55 90 No Count]

16 40 90 Count I

17 35 90 Count 1

18 30 90 Count 14

19 25 90 Count 1

321

20 20 90 Count 11

21 15 90 Count 1

22 10 90 Count 1

23 5 90 Count 1

24 5 0 Count 2

25 10 0 No Count

26 5 180 No Count

27 5 180 No Count

28 5 180 No Count

29 5 45 Count 1I

30 10 45 Count 1

31 20 45 Count 1

32 30 45 No Count

33 40 45 No Count

34 25 45 Count 1

35 3 under" 0 GRS disabled

(no detect)

36 3 under 0 Count 2

37 3 under 0 Count 2

38 3 under 0 Count 2

39 5 under 0 Count 1

40 10 0 No Count

41 5 45 Count 1

42 10 45 Count 3

33

43 20 45 Count 3

44 25 45 Count 1

45 30 45 Count 1

46 35 45 Count 2

47 40 45 Count 2

48 5 135 Count 1 Noise

Building

49 10 135 Count 1

50 10 135 Count 1

51 20 135 No Count

52 3 under 180 No Count

53 5 under 180 No Detect

3

*1IlI

1

I

34I

0 i

I-i

L-i

N3

O-I

n

wI*& I.

0- _36

ILI

N

zw

IK .

w

w. L

b-I 437

IxI

wIw

tu.

ILL-

1w IU. '-4

38)

CIW4

-ON

0-

-Jto

"0-4g-Li-A.

Q3

&i

N

a0

got

-0)

40

II- i.

'Ii.

• I ) I

I~I

424

0-AM

ILA

43

w I

to

I-44

Nl

w

VU

TI-

.- 445

IsY

w

IPI

-lii

044

1L! _ __0

i pT--- -

LLiLIl

46.-,, .

'U

z

0C3)

ONI

N .1-N

OD

(P M

0e-

.4-1 LL UU47

W) M

(.•_

Ix I-

48:11

0. ;'U

'4.8

a.--." i i i i i i I I I1 .. ~ =[/

SIL

ini

N am

w0J°

C-)

I)D

'Ii.iIWO..m-

LLL

0 _

49

ki-

cu

-JU

V)

cm

ol.4

" #4

_.IL)

N5

w

oww

I-i-

Wf,

51

Ix Now

wA

W44

W.4

N

ILIlb-

wC. wLa,.L

a-eN52

w

1L

ow

Nr"LLNPt

cm

53

IUL

hW .54

I m,,

I-am

• • 1i

)I

(r

2I511

)I

z I II I

U,,

56 J5

ERmJill , , , ~ ~~~i 11 + + +i

1. . ..! . ."4- ..•.....+.. . i +++ , ++

II

III

...- -

I.!

57

iN.

VI1L

58

w

Wiri 4

N

.9 59

ILCM)

bE-0

-0A

= I

"N i

if I.ln

61

N I5.,1

I-0 r,

&L &L

62

I

I')

N/

N I.i- .

t d I

: " L-

z * -- -

.. 0

• ., o

"C,, 0

12 I

I"

IL-i

LLIL-

'a64

- --s04 --PLii

LL IiN6

4 p

N VNI

z (669- MMS

~

I' I

NI

!I

90 I;i 6U

.4 i

Chi

M-

N ITuiiI!!

U :L

68

L.

W49CDt

Vi69

iI II a0

N Ii

71 1

4

&IUI-2

PW)

Tj

U.IL~

1')3

wI

i- LI

74H

•7j

-[ : .

fIi: |

i, A

(-£w

- St

V iip,,4I ,

(II. (i

L b 75

('J)

" ".

IL-

76*

I

m i77

," q -

0

I- I,

-- l~l i

N IL

it i

77

vi

4m1

us

_Uw

It-Do

78

ItL

ri V

AI.N7

.4 .

I I

I I"i!j

I,!

Wi I

80

d

3,

"N I

"t

:!a.t..;),I• • L... ... . . . . . . .. .• , -'

- ~ ---- =-~~-,---Y~c- - - ---i

,*0 f

I8

IP-ItvI404

go1

83I

si!

" ~I

84

oto

iN .

@-III

I4V4

I

TII

8S

= -= t a ~ t .~' -- r ,---~tn

-ic

IL4 -

U86

Ni

I4w9

S1L

II,=I

g,,.

.1.I

87

Ili

---

-11

_-1

I. II.

88

.II

L ii4

dI

t-4

1 1,, u .• L

wr

L L-

AlI

1-0

0*90

I!mwgw

==N

Lr I4z P

woOAI

91

ow

'Ii

-JO

a:.a00

Nj-LL L c

°9 -

jiHo

-.-

93

I:7!

'III

IN I

IIa

"1

w

'Ii.

0�4

0

0

I. Iii I*3 4 I

94

I

I'

N

Limrz

LI

a0ULii

liF1K �U)

04*:1 LU.

..4c'1LL�

QS

[1 Ir I:

11 e=.V95

6 -I

CIO

iL W

96

Nq

zP

~j~t

' --II

96

N -•I

mo

! 97

II

I''.4

113

N

w0r

0

C.)Lu0

�V)a;Lu.-Jab1L

Q

III 13 1�

t.,iK -

&a.IL

nH 98

I•1 •

'IIN I& •

-- - - -- - -

LU,m

99I

lt

0

a a

0

• ~. . __ _

1 '9

ii-°° it ,

I. r

10

-1

INAw

I• pII

102

-I "t a

IL

rq

"to ILI

Ii103AI

I-.COq

w10

INII3

"" NIm

Cj)

" tos

0Ql I'i

wL

mI

*1105

LLI

9KI.

Lu

1061

wI

107*

[1Y

N

I

0108

I i

. ft.F00.,•,,I • = - ,

it . .iI I . . . . . .. iI

I

I /"g !

I0 -. 'Iz

a r

S1(

TI$we

IAI

icLO IL0x

o jo

wL . til

s-112

- -

I1

Si.-.-

1.13

Clio

4M 1 *0 qq*uj*

11-14w

I.Uz 114

aro

I 0

I.-Ii

115

-JNI

TI111

4Ji

lii.

:4111

qI_ iiI-

I-L

Lw.l

iiI4I

I'1

� Iiq

N nI,

azI,I

5-

aI"

IL-

U,

I�I9 II. I Ai I- 1

-a--.

La.IL

119

IxIILI

V)

NIN

49

at) I.

LAS

120

C"

4mamow0.

112

8-44

ILL-

C0

A.

1 122

C• ,

1123

N

°°II,- Ii

123

('I'

C

1L.

412

'Lu_

124

I.o

S1I

-• VLi

I,"

I

rr

I!

125 I

OW

1YZ

of

O(3w

A-

-4j

IL W

1 26

LSI.

C

ow

COQ

UAL

(127

(KI

0

ICE

w._Sw6-4 Nb

494

128

LLItv4

ItowU

LL W

129

ii

•I 130!+.

N !

•3 1.LU•'J I

S"---'0N""•bN,4

"q __f!w_

:i it ,131

w

COD

an

ILI

U.LL.

1.32

----- ~.--- -------------- -

wV

rii

NC~j

Ilo-

113

0

0"

U)

-i -a

I. IL9134

LL

InI

U. L

1135

1 4

1361

LL

-� Vi

I

I

i4

I

I

N4I

I

1 1I

Ii

�Ii I.

�j5�B-a-

N

II 1;

I. I! I,

KK 'LI'

137

CY-

fiei

I I

13

tLL

H 138

N4 [

Il-

• ...

Nq

139

k

IZI

tl.--

*1 140

ITI

ILI

UAL-I14-

- - m m= = --

c=li

COD

4 -4

iL -

. i

z1

142

a.,o

I

;I

N

6-

w.

1L

19N I

I'.4

"I-

ww-I-A0-4 0-4Ia=La.

143

1 I4

'ILU.

144

I3IL

CMLI-

.145

1! 12" " k-

1454

hI I i ' l - i-

li _ I • ,- • . .

IU.

414

ac

La.

1LL

LL,

4- In

WLII

147

0I wIw

0-

atI--

414

Nor-.

ae

00

S. -

w.iLL .

In-V)

NMI

ne I-

149

01

<I1-- aIILI

015

'hi.---

4•.--

*.fE

IL*-

4 V)

Ud

150

H• .. .r -'"••••••' ' umiIimI• n iDa~m• il~ u . ]• ••• ' ' r • •• : •

4 0

4m1ý- . .4 p

015

IL

ILII

135

U.I153

160ý

If

LL-.

115

r

3 p

N

II

..Ird,

Lii.

1L

S

II!

a a

9,56��ILU.

.155

SI

I!1£1-u-

156

ON

U.

0~

15

LLI

0 d

ww

I d

ON

I--

115

I-I

!jai

IL-L

Ito

160II

160

0 c

C-)

tjl ale

ITON U

*1161

0

Im02'LU .6-44

116

LId

ae0

0- -

U. L

.J163

0

Ud

I f.-fa)

164

(41p

165

U I

166

IL &L

1671

-. --.. -- - -- ---- fi-,-' �----. -- - --- -. 5--,---- - -.

4

.11N

1

I

1*p)S

II. I

I.Ih.IL 0�

168

°4 p

ii

I

169

A64)

a M

!J~i

ILL--

07

amI

MaiIL-

.4-

wL .

u1171

I-

& Ii.

172

.. .

I'I

172

L- I

FIlk

IL117

-IIcm.

ic

SN

in49

IL W

174

Nu

Md)

117

IxIM4

.176

Io-.

II, I•

ii 176

A

I- 4

-1 -

N 4 7

a:

Ig

�

I-Fl I.4- I

-

w3 -a

It

-4

---- � S S*1 IiILIL

L ___

-:1

i

z q

H I-

- [La-..

417

j!;

LLI

oIw

~17

clii

oll

I& IL

IS

9-i

w.me

Im

0-'-

Ch

SIX

A U.

N

182

LLII

LLI

LLII

_w Iz U

ILI

318

0

w

C OD

U.

LW

184

I...i• - " ..... .. ...... 4ii~ l *r l il ..i li ;':l ll~ '

ccom

I-it

&La

'185

0

IL)

Im (M

ti ýWIM6

186

0%0

ILI

IL L

0~18I

Lii

'Al

÷U . .

118

Ilt1I

188

LLI

0-i

U.4.

'1-9

o V.

oo

I-

,'.-j

[C,

Si._

I.-

LLI

"C"

191

I no w

ILI

LiL

U- -

Ixt-

4I

LL L

19

I

ins

194.

•'1UD . •: • -.• *•-° •. • • r". ••4''•••s• ' s -N• -. . "•

SjV

•.- -IeILi

L D ! ..

aw

I. I

U~Ia.

195 •'

References

1. D. E. Kerr, "Propagation of Short Radio Waves," McGraw-Hill, New York,1951, page 452.

2. Ruck, G. T., Barrick, D. E., Stuart, W. D., Krichbaum, C. K., "Radar CrossSection Handbook," Plenum Press, New York, 1970.

197/78

DISTRIBUTIONNo. of Copies

CommanderWhite Sands Missile RangeATTN: STEWS-AD-L 1White Sands Missile Range, NM 88002

Sandia Laboratori esATTN: W. H. CurryDiv. 1336, Box 5800Albuquerque, NM 87115

CommanderUS Army Armor Center and Fort KnoxATTN: ATZK-CD-MS 1Fort Knox, KY 40121

Jet Propulsion LaboratoryCalifornia Institute of TechnologyATTN.- Library/Acquisitions 111-1134800 Oak Grove DrivePasadena, CA 91103

Commander (4253-3)Pacific Missile Test Center 1Point Mugu, CA 93042

Sandia LaboratoriesATTN: LibraryP. 0. Box 969Livermore, CA 94550

CommandantUS Army Air Defense SchoolATT : ATSA-CD-MMFort Bliss, TX 79916

Technical LibraryNaval Ordnance StationIndian Head, MD 20640

HQ SAC/NRI (Stinfo Library) 1Offutt Air Force Base, NE 68113

CommanderRock Island ArsenalATTN: SARRI-RLPL-Technical LibraryRock Island, IL 61201

Commander (Code 233)Naval Weapons CenterATTN: Library DivisionChina Lake, CA 93555

199

Department of the ArmyUS Army Research OfficeATTN: Information Processing OfficeP. 0. Box 12211Research Triangle Park, NC 27709

ADTC (DLOSL)Eglin Air Force Base, FL 32542 1

US Army Co-mmand and General Staff CollegeATTN: ATSW-ET-L1Fort-Leavenworth, KS 66027

University of California ILos Alamos Scientific LaboratoryATTN: Reports LibraryP. 0. Box 1663Los Alamos, NM 87545

Commander IUSACACDAATTN: ATCA-CAFort Leavenworth, KS 66027

LibraryUS Army War CollegeCarlisle Barracks, PA 17013 1

lIT Research InstituteATTN: GACIAC10 West 35th StreetChicago, IL 60616

DirectorUS Army Ballistic Research LaboratoryATTN: DRDAR-TSB-S (STINFO) 1Aberdeen Proving Ground, MD 21005

US Army Materiel Systems Analysis ActivityATTN: DRXSY-MPAberdeen Proving Ground, MD 21005

US Army Cold Region Research and Engineering LaboratoryATTN: CRREI-RT (Burger)P. 0. Box 282Hanover, NH 03755

Goodyear Aerospace Corporation2112 Lewis Turner BlvdATTN: Mr. McShera 1Fort Walton Beach, FL 32548

200

-A

DRSMI-LP, Mr. Voigt 1-EX, Mr. Owen 1-R 1-RPR 15 1-REG, Mr. Russell 20-RSL, Mr. Frank Case 2I-TE, Mr. Leeper 4-RPT (Record Copy) 1

(Reference Copy) 1

mA

I'-

I .

I:t*V.S GOVERNMENT PAINTING OFFICE: 1Ili-740-106iAI

201

ýLt