TR-1335

TELEMETRY RING ANTENNA

by Howard Sassen

Ronal Jantz

December 1966

U .S . ARMY MATE~IEL COMMAND

HARRY DIAMOND LABORATORIES WASHINGTON . O .C . 20438

DISTRIBUTION Of THIS DOCUMENT IS UNLIMITED

... ,. · ~

... ~ ~ ~

t ····------:.-;

~ ·· · '~iiiii.iurfiiiliit J(..l, .... . ...,.

I '!be findiqs in this report are not to be

c01l8trued u an official Depart•nt of the Army poe1tion 1 unless •o designated by otber author­ized docu.nt•.

Deatroy this report when it ia no lonpr nMded. Do not Nturn it to the oricinator •

•

M-inaaMiMOi AMOK Cotes SMI.11.63600 WLVxoj M«00

AD

TR-1335

TELEMETRY RING ANTENNA

by

Howard Bässen

Ronald Jantz

December 1966

U.S. ARMY MATERIEL COMMAND

HARRY DIAMOND LABORATORIES WASHINGTON. D.C. 20438

DISTRIBUTION OF THIS DOCUMENT IS UNLIMITED

AMUUCT j

i» ZMmcDticnoN ••••••• •■•••• 9

a. wzar BAcuwuND. • 5

3. FABRZCATZOir 10

4. IVAUMTZOir XI

6. MAPTATXOir OT jHB «MBXBHIAYIXlNOni KM iURmU AB A fUZI AllllMKA» •• «#•§••• It

f« OONCIUSIOIf« ••••••••••••••••••17

■

i i

I

ABSTHACT

A quart«r*ir*v«l«nftli ring aatranft was d»T»loptd to tml&amfr •ctlv« fus«« la flight with a ■lalaua nodiflcatlon to fuao or artlllory round. Using prlnolplos of strip transalssloo lino thoory, gonsral doslgn orltsrla wsro ostabllshsd to MXIBIM ra- diation sfflcloney within a flxod font factor. Iloetroplatlng and solsctlvo naohlnlng provldod for sconoalcal^ aoourat« pro- duction. Antonna flold strtngth Masursasnts vorlflod «psota- tlons as to adoquato radiation sffldoncf and a highly syaastr^o, rlng-shapsd pattom. This typs antonna prcrldos tht ability# for the first tlas^ to toloastor In-flight actlTO fuses without aajor shell nodlflcatlon.

1* Ih'rimiUCTION

lbs nood for a fuso toloastxy systsa that would rsqulrs aln- Imm nodlflcatlon to olthor fuso or Its artlllory round provldod tho lapstus for ths dovolopasnt of a now antonna systoa. Iho concept of a ring antonna aountod on tho sloovo botwoon fuao and artlllory shall (fig. 1) was dooasd aost suitable for the above requlreaents. Of prlaary ccmcem was the rtqulreaent that the radiated energy froa this antenna cause no Interference with fuse operation. Cost and convenience considerations dic- tated the need for an antenna ccapatible with the different standard artillery rounds, i.e., antenna perforaance should be relatively Independent of the body upon which it is aountod and withstand ths aaxlana ocodltions of a gun-launched, projectile environasnt. Hie quarter-wavelength ring antenna was developed to aset all of these requireasnts and provided a reasonable radia- tion efficiency.

An eaplrlcal approach was taken in the dovolopasnt of a pro- totype antenna. After baaic, qualitative guidelines were estab- lished froa strip transalsslon line theory, it was found that the aost expedient approach was that of construction and neasure- aent. A hybrid theory involving strip transalsslon line radia- tors in the VHP range is practically nonsKistent end aathsaatl- cally overwhelalng for nonidealiaed goeastries.

2. mSIOH BAOBgRODHP

An understanding of the quarter-wavelength ring antenna can be best achieved through a study of strip transalsslon line theory. The specific antenna under study any be conaldered as a shorted-tenlnatlon strip transalsslon line. At a frequency whose wavelength is four tiaes the electrical length of the trans- alsslon line, a parallel resonant situation soclsts. Ibe input lapedanoe of the line is high and pursly real, consisting of the sua of 11ns losses and a resistance that represents ths radiated

w

'I

Pus« under study

Ring «nLenns

Unmodified 8limn mortar shell

Figure 1. Ring antenna mounted on Slinm mortar shell. 674-66

H w-^wwrn-m™**' ^-imhMmmimim»** ■■■HMn

powtr dlHlpfttion teeter« Itorlag tke drlTlaf point «raj fi th* input leran the iapkUuMt ■Mewed «t the tfrivinf point« Ihii veluo, zeletive to the klfh value of input inptdeaoo, ie • funotion of the vntio of dvivinf point length (ntMuied frai the ohorted end) to total line lenffth. Urne a variety of teal inpodanct valuee if available bgr the proper aeleetion of driv- ing point location«« Vor the «peoifio antenna under etudjr, an inpodanet of SO ohna vae ohoaea ainoe thia valua van eonpatible with the videat range of laboratory inatrunenta and oonial cablet. UM length of an epaqr-fibezglaea, aST-Mbi unit vae 7«35 in« vhile the driving point on thia . unit vae approninately 0«6 in« fron the aborted end«

Oonaideraticn of an idaaliaed^ theoretical^ atrip trana- ■iMion line yielda aeveral inportant ecneepta that nay be util« iaed in the adaptation of a strip traneaiaaicn line to an antenna aysten« figuze S illuatratet the idealiaed case of two infin- ite parallel conducting planes separated by distance h and of width a« A right-handed, Cartesian coordinate systen is util- ised with a being the direction of propagation of a ateady-etate, aiauscidal, electrosMgnetic wave of angular fraqpieney •• In this first analysis, the rsnainder of the n-a planes will be tained aa guard plates to sinplify the gbosvtry« fron Mneell equations the following relationehips are ebtained^t

bz/dz - - JdWC0(a/h)V

and dV/^Z - - (JsiM0(Vo)I

vhere I ■ longitudinal currant ? ■ voltage between platea

^c - 48C10-7 M/m

co m (1/39) x lO"9 F/k

Fron these equationa, the inductoace L and capacitance C per unit length are established aa

L-^h/k *

^ C. «€0 a/h I

h m aeparation bstveenrt plates

a ■ atrip width

c • relative dielectric constant of aaterial between platea

*t. Watson, "iha Physical Principles of Wave Ouida ftananisaion and Antenna Systens," Okford at the Clarendon Press, 1947, p 2.

7

.— ...•.. -,.

Figur« 2 - Theoretical, infinite conducting planes.

CONDUCTING PLANE NEIGHBORING CONDUCTOR

DIELECTRIC

TRANSVERSE COUPLING GROUND PLANE

Figure 3 - Illustration of transverse coupling sffects.

8

N«lth«r ••paration b«tw«eii plat«« nor tha atrip width dataralna tha raaonaat fraquancy (ü0 of a fixad-langth Una line« cancal- latlon of tha a and h tana oeeura In tha following ralatlon: a) ■ I/VLC, Strip langth aolaly datamina« tha ratonant fra- quancy of a Una at a fraquancy whosa wavalangth nay ba aypranad as X ■ Sir v/w . whara v ■ valoolty of propagation v ■ l/Zcc a . By talactlng a aatarlal with a aultabla dlalactrlc constant €, a flxad physical dlnanalon nay ba sad« coapdtlbla with a daalrad alactrlcal langth slnca tha dlalactrlc-loadad Una langth nay ba shortanad by a factor of l/Tc ralatlva to at air dlalactrlc Una.

Tha radiation of anargy from a tranaalsslon Una can ba analycad In an affort to ■axlals« thla phanoaanon for antanna appllcatlona. In tha Idaal casa, only tha im aoda la prasant (trua If spacing bstwaan conducting strip and ground plana la lass than ono-half wavalangth), Undar thaaa conditions^ radlatad power Pr ralatlva to power tranaaittad In tha Una P Is ax- pressed as*:

Thus

where ZQ m characteristic line lapedance

h ■ height of conducting atrip above tha ground plana a ■ conducting strip width

&. 4 K« « constants s X ■ wavelength of propagated wave In the atrip

tranaalsslon Una.

It can therefore be stated that a change In either strip width or spacing will cause a directly proportional change In radlatad power relative to Input poser.

Power flow between conducting and ground planes Is rastrlcted to an area In the laaedlata rldnlty of the tranaalsslon line.**

♦D, Orleg and H. Ingelnann. "Mlcroatrlp—A new Tranaalsslon Tseh- nlque for tha Xlloaegacycle Range, IRS Proceedings, Vol 40, Dec 1902, pp 1644-1651,

♦♦F. Assadourlan and I. Rlaal, "simplified Theory of Mlcrostrlr rransmisslon Systems," IRE Proceedings, Vol 40, Dec 1952, pp 1651-57.

I ^■^^(jKHIWll'i) JüPHi"'

It is lUadafd pmetlM la «Mlytis of strip traaialMion UM« to ooooidor a gsouad ploao infinit« in width if it i« gr««t«r tlun tkfo« tia«« ttao width of th« oooduoting «trip. Ihi« iapli«« that a «trip tr«n«Bi««ioa lin« radiator i« virtually ind«p«nd«nt of it« «nrroundinc«. lb« proportjr of solatir« |Bd«P«ndono« of th« hody up«« Whioh it i« ■oimt«d i« eliaraot«ri«tic ox this fam- ily of aat«na««9

Con«id«ration «uat b« §!▼«« to th« powor lo«« that ooours duo to tr«n«w«r«« oouplinf of foot«, lb« proaciaity of th« con- duetinf «trip to oitbor ground or othor oonductlng «trip« l«ad« to ooupliBf of th« tnuuivor«« eoapoavnt« of radiatod «n«rgy. Attenuation of tran«Y«?««ly radiatad «Mrgy i« «xpr«st«d aa*s

at - ar/b

a±m attanuation in db/unit diatane«

b ■ di«t«aoo of oooduoting strip froa transvors« con- ducting plan«

By aaxiaising th« di«taaoo of th« oooduoting «trip froa conduc- tor« parallel to tho diraotion of propagation, th« transvors« coupling «ffoct nay bo aad« nsgllgibl«.<flg. 3).

froa ths abovo con«id«rationa on« aay draw ««v«ral basic ooaolusioa« in th« adaptation of «trip transaisslon linns to an aatanaa «y«t«a, Waralangth and xosonano« ara «trictly function« of «trip l«ngtb and dioloctric. Radiatod powor inoroasos di- rootly with incrsaslng diaonsioos of strip width and spacing abovo th« ground piano. Powor flow is rostrlotod to tho area in th« i«a«diat« vicinity of tho lino, iaplying that only lia- itad «xcttation of tho surroundings occur. Spacing of th« oontor conductor with ro«p«ct to conducting areas running par- allel to tho piano of tho center conductor should be adequate to avoid transverse coupling effects.

3. PAMICATK»

Ita« fabrication of a prototype that could be cheaply yet accurately reproduced in large quantities was achieved through th« technique of electroplating. Figur« 4 illustrates an opoBKy-fiberglass ring coapletely plated with a 0.002-in. copper layer, then aachined to create a circular strip transaission

«W. Prona, "Characteristics and Seas Application« of Striplin« Coaponents,** IRI Transactions on Klorowavo Theory and Technique, Vol mis #3, March 1965, pp 13-17.

10

-.,

■

■

■

Ground plan

■<.. ■

- ■. ■

■

- ■ ■

Driving point

; ■ i • / ' r r i- i • • • | • • • | • • ! ■ . • » o i a a i 7 INCH I

■^mimii l<u lv#4f Hf li f«111 • f. i • i • 11111111 h!: 111 v^J^La^y Figure 4. Epoxy fiberglass ring antenna.

... _v.

^# - •.■■

.-■ ■-.,.■ „

•••■ ^ ..■■•■

■ *'■ ■v

i ^ • £1

Figure 5. Antenna mounted on fuze hardware. 672-66

Hu». Ite ■aehiBlnff proMii was nad« «octraatly tlapl« In the follovlBf ■alliiert Before plating, a circular groove !■ machined around the center of the ring while a eecond, lateral groove la ■aohlned perpendicular to the first. After plating, the raised edges bordering the circular groove are removed In a lathe. A continuous circular strip of copper, grounded by the lateral groove, remains on the ring. A 1/16-ln. break In the lateral groove Is cut In the copper, creating a strip transmission line with a ground plane comprising the back, top and bottom sides of the ring.

Semirigid cosxlal cable Is connected to the appropriate driving point through a hole drilled In the wall of the ring. With epoocy encapsulation to ruggedlze this Joint, the antenna assembly Is made sturdy enough for most present artillery en- vironments. Figure 5 Illustrates a unit fitted In this manner.

4. IVALPATiaN

The quarter-wavelength ring antenna was evaluated In two ways, through a study of Impedance and reflection parameters and by a comparison with standard dlpoles and similar reference radiators. Presented In figures 6 and 7 are the Impedance and VSWR versus frequency characteristics of an epoocy-flberglass- dlelectrlc ring antenna. Figure 8 shows the antenna mounted for test measurements. A usable bandwidth of approximately 6 MHz at a frequency of 227 VBz Is well within the limits of existing telemetry transmitters. While first units evaluated were ap- prooclmately 14 dB below a reference dlpole, further studies In- dicate a 10-dB figure Is entirely feasible using the theoretical guidelines presented In this report. The achievement of this 10-dB value represents a high figure of merit for an antenna of this physical size and frequency range. The relatively nar- row bandwidth of this antenna can be utilized advantageously by using the antenna as the tuned circuit of a coaxial oscil- lator whose bandwidth will consequently be narrow. It should be noted that by decreasing line losses, through the use of lower-loss dielectrics, a proportional decrease In bandwidth occurs.

Antenna field strength patterns Illustrated In figure 9 Indicate the symmetrical pattern characteristic of this type antenna. The very uniform circular azlmuthal ifield strength pattern is of major significance in both telemetry and fuze considerations. Of particular Interest is the fact that no radiation of power occurs in the nose region of the shell, implying that telemetry transmission should not interfere with the active fuze. The wide 3-dB angle of dispersion (60°) of this antenna is of great value for telemetry applications

12

VSWR

223.9 229.1 FREQUENCY (MHz)

Figure 6. VSWR versus frequency.

225 226 227 Fo 228 229

Figure 7. impedance versus frequency,

13

■■«

■ ;m*vwm'w,<mif*wW3** ' ■wipw'' I

■

- :■

- • ' . . .

■ "

673-66 Figure 8. Ring antenna In test fitting.

■u. $0

-J

? z o N £ o

UJ

u UJ

o Q: a.

-i < u P K UJ >

UJ

u UJ

o K Q.

(D O o II

UJ -I o Q.

tr < a z ? V)

s N CM (VI

Ul K Z <

UJ z

£z K > UJ — I- ^

O -J < a: o

u. üJ CO1

z z K I-

r» a. Qj

o z UJ o: I-

UJ iZ I

UJ a O

(ft < UJ

■

■Inc« It psnitf gnator flexibility In th« poflltlonlng of MMlvlng statlonfl whll« aalntftlnlng unlfom rto«lv«d «Ifnal l«v«ls.

5. APAFTAnOH Off TM qPARmHWAVUlMOTH RIMtt AMIINNA AS A FÜZI AMT1NHA

Ite physical and aarodynaalo oharactarlatlea of fuso-oarry- Ing alaalloa usually laposs strict llaltatlons upon ttas fuss aatsnna. His antenna mist bs ■■all, ruggsd enough to withstand high vslocltlss and tsmptraturss # and still glvs a radiation pattsm that will produce the desired target sensitivity. The fuse antenna should also require no »edification when used on various projectiles. The doppler fuse depends on the Inter- ference between an Incident wave and a wave rsflooted from the target. Ihls Interfersnce Is analytically equivalent to a load variation on the transmitting oscillator caused by a changing antenna Impedance. This principle Is applied In adapting the ring antenna for fuse use.

TWo common fuse antenna types are the loop antenna and the cap antenna. Use of the cap antenna for vehicle excitation results In satisfactory radiation, but the sixe and shape of the vehicle have a great Influence upon the radiation pattern and the frequency used. Loop antennas opsrate as part of the tank circuit of the oscillator as well as the radiating elements. Design problems are complicated since the use of a loop antenna requires suitable loop dimsnsions and an operating frequency must be chosen for efficient operation and desired impedance values. The ring antenna, however, is independent of vehicle length and can be tuned to the frequency desired. The use of the quarter-wave ring antenna means it is possible to choose the antenna Impedance and operating frequency desired and then tune the antenna to these parameters.

The quarter-wave ring antenna has a considerable mechanical advantage over a loop antenna. Whereas the loop antenna is placed with its axis parallel to the axis of the missile and requires a certain amount of height, the ring antenna is mounted in a plane perpendicular to the missile axis, as shown in figure 1. This results in a large saving in space. For a fixed frequency, sev- eral ring diameters «re also possible by choosing materials with different dielectric constants, since the physical length is in- versely proportional to the square root of the dielectric constant.

The ring antenna produces a typical longitudinal pattern as shown in figure 9, when the antenna is mounted on the missile as shown in figure 1. This radiation pattern is very similar to

16

that produced by tlw loop antenna. A» 1« truo for tha loop an- tonna, the aaall slse of the quarter-wave ring antenna means a relatively Inefficient radiation lyatem. Tbm alaalle, however, is relatively free from vehicle excitation when the quarter-wave ring antenna la uaed. Since any impedance values are available, the phasing of two or »ore rings can be accomplished to give more pattern flexibility.

Ihe quarter-wave ring antenna may be applied to the devel- opsMnt of a short intrusion fuse. This type antenna provides various new mounting configurations along the missile axis.

6. CONCLUSION

A quarter-wavelength ring antenna for telemetering artillery fuse functions has been developed. Ihe deaign is such that it may be mounted without modifying the shell and offen consider- able leeway in locating the receiver, because of its wide beam angle. Ihia type antenna will provide the ability, for the first time, to telemeter in-flight, active fuses without major shell modification. Ihe application of the ring antenna for uae as a fuze antenna is also suggested.

17

tmciAMxriD

mgmgm itHimuitm dim, ********** n$mt h •i—*n*4i i. wmmsimWWfmm

Barry Diawmd UboratorlM, Washlngtoa, D. C. 20438

a«, MPMIT Mflumrv CLAMIPICATION

UMCLASSiniD

f ft- «MU»

!• MMRT TITkl RUDORRY RING ANHMNA

\(T9t»*

%. AUTN9WW tU* mm* TSi BMS«n, Hiward Jants, Ronald

^MMRTMTI Dao«ab*r 1966 24

•«. ««HTIIACT •« MANT N«.

aMMMTH». DA-lia22901A301

•.AMCMS Cod«: 5221.11.62600

*HDL ProJ 86800

•» •m«INAT*N>t IICP«HT NUMftlNfV

1A-1338

**" ICÄÜf **''* MI,W (;4*,f ><l,rll"ll>,"> *•* MT M M«l«Mtf

11 AVAIkAMUTV/UMTATieN NOTtCa

Distribution of this doeuMBt 1« unllnlted

It. tU^LBMtNTAIIV NOTIS II. IMNSOMN« MLITANV ACTIVITV

U.S. Angr Mntorlol Conmnd

U. AMTRACT

A quartor-wavolongtli ring antonna was dovalopod to toloastsr actlvo fusos In flight with a nlnlmui aodlflcatlon to fuz« or artlllary round. Using prlnolplss of strip transmission Uns tbsory, general dssign oritoria wors •stsblishsd to Mucinize radiation «fficisney within a fizsd form factor. Iloctroplatlug and solsetiv« aaehining providod for «cononical, aceurat« production. Antenna field strength msasurseonts vsrifisd «xpsctations as to adequate radiation efficiency and a highly syaaetric, ring-shaped pat- tern. This type antenna provides the ability, for the first tine, to telemeter in-flight active fuzes without major shell modification.

DD POSH I JAM M 1473 UMCLASSIFIID

Sseadtjr Classiflcsttes 23

I

UNCLASSiriKD Stcurity CUttlflcticir

14. KIV VOROI

LINK A I WT

LINK ■ ROLC «T

LINKC NOLI WT

Ring antenna

Fuze antenna

Telemeter antenna

iNirmicnoNs 1. OMOINATINO ACnviTYt Bat«r th« IMM and addrMt of lh* eontracter, •ubcentraetor. grMit««. DapwtaMt of D» f«iiM Mtlvlty or othar organtMUon (eoipotlm mtthn) laming r<M raport.

3a. REPORT SBCUnry CLAMIFICATIOK: Bnlar Iha evat^ all aaeorlty claaaifleallen af tha raport. ladlcata whathar "Raatrietad Data" la InaludaA Marking la ta ba In accertf- anca with approprlata aaeurtty ragulatlona.

26. OROUPt Automatic downgrading la apaclflad In OoD 01* ractlva 5300.10 and Armad Parcaa Induatrlal Manual. Entar tha group nuMbar. Alao, whan applleabla, ahaw that optional marklnga hava baan uaad for Group 3 and Group 4 aa author»

S. REPORT TTTLEi Entar tha conptata raport tltla In all capital lattara. Tltlaa In all caaaa ahoold ba unctaaalflad. If a awaalngfiil tltla cannot ba aalactad without claaalflca» tlon, aha« tltla elaaalflcatlon In all capltala In paranthaala taiawdlataly following tha tltla.

4. DESCRIPTIVE NOTES: If approprlata. antar tha typa of raport. a.g., latarlm, prograaa, auaunary. annual, or final. Olva tha Inclualva dataa whan a apaclflc raportlng parlod la covarad.

5. AUTHOR(8)i Entar tha naataCa) of autboKa) aa ahown an or In tha raport Entar laat nama, fir at nama, mlddla InlllaL If adlltary. ahow rank and branch of aarvlca. Tha nama of tha principal author i» an abaoluta minimum raqulramanl.

A. REPORT DATE: Entar tha data of tha raport aa day, month, yaan or month, yaar. If mora than ona data appaara on tha raport, uaa data of publication. 7«. TOTAL NUMBER OP PAGES: Tha total paga count ohould follow normal pagination procaduraa. La., antar tha mimbar of pagaa containing information.

76. NUMBER OF REFERENCES! Entar tha total numbar of rafarancaa cltad in tha raport. •a. CONTRACT OR GRANT NUMBER: If ^propriata, antar tha applleabla mimbar of tha contract or grant undar which tha raport waa wrlttam

S6, IB, fc id. PROJECT NUMBER: Entar tha approprlata military dapartmant idantlflcation, auch aa projact numbar, uibprajact nuaftar, ayatam numbara, taak numbar, ate. «a. ORIGINATOR'S REPORT NUMBER(8): Entar tha affl- clat raport numbar by which tha documant will ba Idantiflad and controllad by tha originating activity. Thia numbar muat ba unlqua to thla raport 06. OTHER REPORT NUMBER(S): If tha raport haa baan analgnad any othar raport numbara failhar hy (ha originator or by (Aa tpoiwor), alao antar thla nttmbar(a).

10. AVAILABILITY/LIMITATION NOTICES: Entar any 11m- Itatlona on furthar diaaaminatlon of tha raport, othar than thoaaj

24

Impoaad by aacurlty elaaalflcatlon, ualng atandard atatamanta auch am

"Quallflad raquaatara may obtain coplaa of thla raport from DDC"

"Foralgn announcamant and diaaamlnatlan af thla raport by DDC la not authorlsad"

"U. S. Oovarnmanl aganclaa may obtain eaplaa of thla raport dlroctly from DDC Othar qnallBad DOC uaara ahall raquaat through

(I)

(3)

(3)

(4)

(5)

"U. 8. military aganclaa may obtain eoplaa of thia raport dlractly from DDC Othar quallflad uaara ahall raquaat through

"All diatrlbutlon of thla report la controllad QuaU Iflad DDC uaara ahall raquaat through

If the raport haa baan furnlahad to the Of flea of Taehnleal Sarvicaa, Dapartmant of Commarca, for aala to tha public. Indi- cate thla fact and antar tha price. If know»

1L SUPPLEMENTARY NOTES: Uaa for addlUonal aaplaaa. tory notaa.

IX SPONSORING MILITARY ACTIVITY: Entar tha nama af tha departmental project office or laboratory aponaorlng fpaj» Ing lor) tha reaeerch and development Include addreea. 13- ABSTRACT: Enter an abairact giving a brief and factual aummary of tha documant indicative of the report, even though it mey alao appear alaewhare in the body of the taehnleal ra- port. If additional apace la required, a continuetlon aheet ahall ba tttechad.

It ia highly deairable that the ebatract of claaalflad reporta ba unclaaalfied. Bach paragraph of the ebatract ahall and with an indication of the militaiy aacurlty claaaificetlon of the in- formation in tha paragraph, i«pr«aanted aa (TSi, (S). (C), or (V).

Thaia la no limitation on tha length of the ebatract Hew- ever, the auggaatad length la from ISO to 22S werde.

14. KEY WORDS: Key worda are technically maaalngfol tarma or abort phraaea that characteriae a report end may be uaad aa (ndas antrlea for cataloging tha report. Key worda muat be aelaciad ao that no aacurlty claaaificatlon ia required. Uentl- fiera, auch aa equipment model dealgnatlon, trade neaM, military project code nama, geographic location, may ba uaad aa key worda but will be followed by an indication of taehnleal eon- teat. The aaalgnmant of linka, rulea, and weighta la optional.

UNCLASSIFIED Security Clatsificntion