CA2121153A1 - Active antenna array - Google Patents

Abstract

AN ACTIVE ANTENNA ARRAY

ABSTRACT OF THE DISCLOSURE
An active antenna array (58) for use in a radar seeker has a preselected number antenna elements (60) which are individually connected to an identical plurality of transmitting and receiving modules (64) backed up by a cold plate (66) for removing heat produced during use. In a preferred embodiment each module has a rectangular prism housing (84) within each of which there are individually modifiable phase and gain circuits (76,78). In a further embodiment, the transmitting and receiving modules are constructed of a number of wafers, each wafer having the same number of separate identical circuit function blocks as there are antenna elements.

Description

2 1 ~ 3 : `

AN AC~ ANq~NNA ARRAY
,,,, BACKGROUNQ
``~' ' '` ..`' , . Field Qf_the Invention ,~
The present invention relate~ to ~n antenna ~`- ',"
array, and, more particularly, to an active antenna "-'~
array for u~e with a radar~g~ided missile~ for exampla. ; .-2 ~escriotion o~ Related Art ,~ , '' In ce~tain kinds of missile systems, '', "';:;`,;
fre,quently ref-rred to as guided mi~siles or mi~sile ',~
see~ers, an on-board radar ~ystem diracte a radar beam toward3 the target and reflected energy recelved and , ,"~
processed ~aintains the missile on the desire~
intercept cour~e. The sophistication of avoidancQ and ,~
~amming technigues, which can be employed,~or the bane:fit of the targ~t in order to avoid a guided ~"`,~
missile seeker or redirect it along a non-intercept ,~ ~, course, have made it necessary to i~prove the missile ~, ', seeker in order to overco~e thess defensive ~ea-ures ';'',', and enhance th~ probability of successful target intercept. Typical defensive measures produce false ' ~
radar return signals, having the purpose of confuslng ,,,' ','~, the miBsile guidance system: as to the actual targe~
Approaches employed in~ advanced misBile ~, 25 seekers to defeat guided missile defenses, in a ~ajor , , part, recognize that RF ~ignal will be received over a r~latively broad angular field and electronic ~ ' 2 2 ~

1 procQssing of these signals 1~ requ~red to en~bl~ the seeksr to separate ~falae" 8ignal8 ~ro~ r~al target radar returns. In ~ddition, in multiple target engagements (multiple real targets and/or ~ultiple radar emitting decoys) the ~eeker must b~ capable oS
selecting a particular target located within the target ~ ~;
cluster.
A w~ known guidance sy~tam, typic~lly ~-referred to as a gimballed seeker, mounts a high gain antenna on a gimbal a~sembly to allow th9 ~eekar to b~ -pointed over a relatively large ~olid angle or scan volume. A servo ~ystem drive~ the gimbal which allows ` ;~
positioning of the antenna ~or both t~ansmis~ion and receipt of radar energy in a de~ired direction Yithin the scan volume. The weight, cost, excessiva volume and mechanical complexity of ~uch systems make replacement desirable. Additionally, gimballed sy~tems have traditionally had to be custo~ designed and fabricated for each new application.
Another form of missile seeker utilizes electronically scanned antenna (~SA) technology which includes a large numb~r of individual antenna element~
each of which has the capability to program the`phase ` of the transmitted and received signals. In one ver~ion o~ an ESA, known as a pas~iv~ ~SA, ths high RF -power ~5 developed in a separate transmitter unit and then partitioned among the numerous phase shifting elements. Since the phase shi~ting function is performed at relatively high power, the phase shifters tend to have high losses. In addition, since all the elements of the array are being driven by a single transmitter and the signals received by the individual array elements are combined prior to being rou~ed to the receiver, this ESA approach lacks the flexibility required to fully utilize modern signal processing 1 te~hniqua~ th~t requira access to multipla su~-~rray~
of the full apertur0.
A second ~SA approach, called a hybrid ESA, u~es high power ampli~iQrs and low noise a~fplifiers to `~
develop the tran~mit and receive 8ign~15, respactively, for group~ Or antenna radiating and receive elements.
Thi~ latter approach has many of the samef di~ficultie~
.. . ...
as the passiv~ ~SA and still does not provide ~ully independent radiating/recelve elemefnts inf th~ array.
In addition to accurately guiding to intercep~
the target, a guided mis6ile typically carries a -warhead payload that is desifgnefd to ~axi~ize damage to ~`~
the target under attack. To increase thef probability of taking out the target, accurate data is needed at intercept to determine the optimum bur3t point for the warhead. Exi~ting ~issile seekers used for guidance are not capable of collecting the precise data required to compute the optimum burst point for the missile ~ `~
warhead. In known syste~s, a second highly specializfd ~`
sensor i8 included in thef mi3sile de~ign to ga~her thi~
required data. It would be desirablef to be able to accompli3h this function ~ith the ~issile seeker, thus eliminating the need for a separate radar ~yste~, both bscause of additional cost and weight of such a sy~te~
as well as the taking up of additional space on-board thef missile.
,, SUM~a~y--F THE DISCLOSUR~
It is a primary aim and objective of the present invention to incorporate an active -~
electronically scanned array (AESA) into a radar guidance system for a missile to provide numerous advantages that are not attainable with the present art. These advantages include: (1) a modular and cost e~fective approach to achieving seeker power-aperture `-~ 212~1~3 1 product, (2) wide bandwldth enabling integrated active/pa~ive (ARH) guidance, (3) adaptive be~
formatlon to enh~nce seeker guidance in the presence of `~
stand-of~ ~ammer~ (SOJ8), (4) enhancsd guidance against - ' clustered targets, (5) ~eeker-ba3ad fuzing, i.e., integrating guidance and fuzing ~unction~ into a single seeker, and (6) improved reliability and graceful pe,rformance degradation through functional redundancy and r~al-t~me adaptive compen ation for f~iled elements in the array.

1. Modular con~truction ~ ~, The AESA is constructed o~ individu~l active transmit/receive modules. ~ach module con3ist~ of a ~'~
transmitter element and a radar receive element which are individually adjustable as to phase and gain. ' These basic building blocks may be combined together to form an array of any size without having to incur a - largs design co~t. By use of modular construction, it is possibls to provide ac~ antenn~ array~ o~ any desired size by ~erely assembling the appropriate number of module~

2. Wide bandwidth. inte~rated active/Pas~ive ~ M
ouidance Wide bandwidth is inherent in the basis design of the active transmit/receive (T/R) modules, and they ~ ~`
are capable of operating over bands that are tens of ,~
percent wide. Their ability to operate over such wide bandwidths allows the missile seeker to derive passive guidance information against various emitters opexating on-board the tarqet. In addition, the wide bandwidth supports active operation ovsr a wider bandwidth, which provides enhanaed performan~e in scenarios with multiple missiles in flight simultaneously or in high , 7~ 7i'S,'~

- -` 2121~3 , , ','~

1 RFI (i.e., radio frequency interference~ environments. ' `;
A wider operating bandwidth may alco prov~d~
performance advantage~ against ~ome ~lectronic counter '' mea~ura~ ~ECM) techniques. Forcing an EC~ device to , -~
operate over a wider bandwidth may dilute ~h2 ~a~ming power received by the missile seeker receiver. , 3. Adaptive k~am fo~ation to enha~e 3eek~ gcil~ng~
in the Preaent of s~and-off iam~er~_lS
The A~SA is capable of adjusting th~ gain and ,- ;~
phase of the individual elements of th2 active array to 8te9r antenna null~ in real-time to eliminate the interference from off-axis stand-off jammer~. With ' ~, reduoed interference, the probability of successful guidance to the desired target is enhanced.

4. Enhanced quidance aqainst clustered targe~s '~
With an AESA, the array may be partitioned '~
into multiple sub-arrays which by the use of appropriate signal proGessinq can achiev~ i~proved ' guidance to a specific target located within a cluster , of'targets. With separate transmis~ion and receiving ;~
capabilitie~ as well as individual phase and gain control for each antenna element, the sesker can resolve signals received fro~ a large numbar of independent targets. Furthermore, the resolution ~apability is not dependent upon the returns coming , from oomparably sized targets.
~, 5. Seeker-based fuzinq--inteqrating guidance and fuzinq function,s into a sinale seeker With an AESA, the same missile radar system ,~
used to detect and track targets can be used to collect ;',~
the data requisite for compu~ing the optimum burst point ~or the missile payload warhead. The inherent s 2121~53 1 feature~ of the actlve T/R ~odule de~ign which ~llow the fuzing function to be combined with the rad~r seeker are the small blind range (fast r~cove~y time after transmit), the wide bandwidth of tho T~R ~odule~
which supports waveforms that ar~ capabla o~ making precision measurement~ of target dlmensions, and the agility of pointing the seek~r bea~ to int~rrogate t~a target dimensions.

6.
degradation throuah funçtional redundanc~ and real-time adaptive oom~en3ation ~o~_~11Q~_ elements ~1 the array The AESA i5 typically compo~ed o~ lOO or more active elements. ~ach element has inherently high reliability, but in addition, the failure of a æinqle element may be compensated for by adjusting ~he parameters of gain and pha~e of the "neare~t neighbors". This feature provides graceful performance degradation as individual ele~ents fail. In addi~ion, high power seekers that use travelling-wave tube (TWT) technology typically require that the seek~r be pr~ssurized in order to preclude transmitter arcing and subsequent fa~lure. Any failure of the pres~ure ~eal will result in cata3trophic failure of t~e mis~ile seeker. Because each T/R module has a low~r peak power, the requirement ~or pressurization to preclude arcing is eliminated. The active T/R ~odules u~e much lower voltages than the TWT transmitter which commonly requires voltages on the order of ten thousand (10,000) volts to operate. Such high volta~es require extremely sophisticated manufacturing approache~ to ensure that power supply related failures do not occur. ~any o~
these issues are completely eliminated by the use o~
the active T/R modules which utilize voltage~ on the - 21211~3 1 ord~r of tens of volte. Finally, an A~SA eliminatas -`
the ~oving part~ that ~re part of ~ conventional gimballed antenna. The elimination of the gi~bal assembly with the accompanyin~ torquer ~otors and high-powered ~ervo electronlc~ ~ill provide a mark~d enhancement in reliability.

DESCRIPTION OF ~E DRAWING ~ -:
In the accompanying drawing:
FIG. 1 is an ~xplod~d ViQW of ~ pr~or art antenna asse~bly with convention~l array and 8ervo sweep apparatus;
FIG. 2 is a graph of antenna gain receiv~d along bore~ight and ~paced to each sid~ o~ boresight;
FIGS. 3A, 3B, 3C and 3D are schematic, ~:
function block depictions of the various apparatus required in the prior art missile radar seeker~ for a conventional slotted array antenna, for a passive ESA, and for a hybrid ~SA, respectively;
FIG. 4 shows an exploded view of variou~ part~
of an active array seeker of the present invention; `~
FIGS. 5A and SE are function block diagram~ of the active array of thi~ invention; and FI~. 6 i~ a urther sche~atic of a ~eeker apparatus sy~tem in accordance with this invention.
: :`''''`
D~S~IPTION OF A PREFERRED EMBODI~ENT ::
Th~re are three known alternative approaches : :;.
! to mechanizing the missile seeker: (1) the conventional gimballed slotted array antenna, (2) a passive . ;;
electronically scanned antenna, and (3) a hybrid electronically scanned antenna.
FIG. 1 s~ows in an exploded view the various . ;~
parts of a typical prior art gimballed radar seeker sys~em for guiding a missile enumerated generally as ~.''' - ~ ~

8 2~211~3 1 10. The 3y~tem includes, at the ~orward end, an antenna array 12 con~lsting of lndivldual antenna ~lement~ (or 310t~) 14 in a general ~trlx ~rrangQment, and various lnterconnection and ~lectronic circuit S means collectively identified as 16. The ~ntenna assembly 18, conQi~ting of the antenna array 12 wi~h interconnections and electronics 16, ixedly ~ecured to a gi~bal mounted pedestal 20 w~ich, in a conventicnal known manner, provides the ability for moving the antenna array 12 to face in any desired direction over a relatively wide solid angle. A serYomechanis~ drive 22, with associated control and drive electronic~ 24, i~ typically co~bined wi~h an RF proces30r 26. In use, the seeker assQmbly lo can be operated to ~can over a given solid angle and thereby enlarge the angular .-.
coverage that would be accorded to an antenna array 12 fixed in position. Such a gi~balled antenna array ~ :
system typically has from ~wo to four rec~ption ~ .
. channQls, and i8 highly tunsd in frequency with a - 0 relatively narrow operating ~requency ranse. .
A~ shown in the graph of radar responses of FIG. 2,.the radar echo or res~on~e 28 received directly along antenna boresight (often called the mainlobe ;
response) i8 the largest, but for angle3 away fro~ the ..
mainlobe, th~ signal return for high powered off~
boresight signals may still be signi~icant (e.g., 30,32). These responses away from the mainlobe peak ara usually re~erred as antenna sidelobes or just ;~
sidelob,es. Also, it i5 to be noted that between adjacent lobes there are points of zero reception 34, or "nulls". In practice, a signal located at the same ;~
angle or position as a null would not be sensed. There are two potentially adverse impacts of theee off -~
boresight responses: (1) In the presence of ~trong jamming signals located at an o~f boresight angle with ~:

--` 2~211 ~3 1 a ~idelobe peak, ~amming power received may be of ~uch magnitudQ that will impair acqulring a radar eign~l returning from the target, and (2~ if the main bea~ of the antenna ls not positioned directly toward the target and the target return falls in an antenna null, it may not be po~sibl~ to acquir~ the desir~d target return at all. In the ca~e of a gimballed antenna, the nullG are fixed and present a continuing po6~ibility for error in detection.
Not only have gi~balled antenna systems bsen ~ound unable to overcome many standard d~fensive techniques, they also are relatively heavy and bulky in reguiring ~ervo motors and a gimbal~pedestal which are relatively heavy items. In addition to weight, the size requirements for a gimballed antenna ~ystem exceeds desirable limits.
Turning now to FIG. 3B, an electronically scanned antenna (ESA) in the so-called passive form i8` ~
seen to consist of a large nu~ber of antenna element~ ;
36 arranged in a matrix 38 with phase control apparatu~
40 which enables collectively changing the phase o~ the signals raceived or transmi~ted fro~ the ant~nna i~ ~ ;
ele~ents. This approach offers a limited amount o~
control and proces~ing. Since the phase ~hift ~unction i~ perforned at high power, a substantial amount of loss typ~cally occurs across the phase shifter elements of apparatus 40.
In a hybrid ESA 42 (FIG. 3C), a phase control 44 again provides phase change across an antenna array 46, with a low noise amplifier 48 (LNA) provided for the return signals and additional separate amplifying means 50 provided for the transmitting signal from the exciter (FIG. 3B). Each low noise amplifier 48 is seen to include a limiter 52, an amplifier 54 and a aontrol 56 for the amplifier (FIG. 3D). Hybrid ESAs have ,~

. . , ' . , . . !; ~

2 1 ~ 3 1 problem~ ~imilar to pas~ive ~S~3 in that ~he pha~e ~hift function iB implemented at high RF power.
For the ensuing de~cript~on o~ the preaent invention, re~erence ls now made to FIGS. 4 and 5 wher~
an active array to be de3cri~d iB enumerated generally as 58. At the forwar~ facing end of the activQ array ;~
~eeker i8 a wideband antenna array composed of a plurality of individual antanna elements 60 which, ~or exemplary purpo~e~ only, will be aonsidered to number one hundred (100). They ar~ depicted ~ flared-notch type elements but may assume ~ variety of differsnt known forms and be suitabl~ ~or present purpo~es. It is important to note that the individual antenna elements are not secured to a 3ingle background, however, they are arranged in a modular form with each module including an antenna element. In thi8 way, an antenna array can be made up of any desired ~lze by merely utilizing the necessary number of antenna elements for the desired array.
Just behind the array o~ antenna ~lements, there is a module array and cold plate as~embly 62 consisting o~ individual module~ 64, one for each antenna element. ~ach module 64 includes at it~
forward facing surface can be mated with 25 corresponding elemen~ 60 ~rom the broadband antenna ~
array, serving both to phy~ically and electrically ~ ``
interconnect the module array and cold plate assembly modules to the antenna array module~. The cold plate assembly, identified separately as 65, can be constructed in a number of different well known ways, e.g., circulating coolant, change of phases material, or heat pipes.
With reference now particularly to both FIGS.
5A and 5B, it is seen that the individual antenna elements are connected through separate modules 64, ~ .

, ~.

ll 2~2~1~3 1 identified generally as T/R (tran~mit/rec21va) modules, which individually cont~in th~ circuit~ shown in FIG.
5B. More particularly, interconnection with tha antenna element i5 initially via a duplexer 70 which, in a way well known in ~h8 art, intarconnects outgoing radar signal~ fro~ a high-power a~plifier 72 (HPA) to the assoclated antenna element 60 for tran3mit and interconnects re~l~cted rad~r ~ign~18 fro~ thu s~me antenna element 60 to a lo~ noi~e ampli~ier 74 (LNA) for receive. The~e signals interconnect through tha duplexing switch 75 to a com~on line con~ ing o~ a serially arranged variabl~ phase control 76 and a variable gain control 78. Accordingly, both the :
amplituds and phase of each signal as appli~d to or ~:
raceived from each antenna elem~nt can be separately controlled as to phas~ and amplification. For - -~::
transmit, ~ince ~he phase and gain control is performed prior to the high power amplifier, phase and gain : `
control are implemented at lowQr power and can b~
accomplished with low 1088.
The r~ar face of each of the modules in the module array and cold plate a~sembly 62 receivea necessary RF and logic control signal~ from the RF and logic distribution network 80. : :
Finally, adaptive process~ng and monopulsQ
network circuit~ 82 are incorporated wi~h four major blocks or modules similarly mounted to and electrically connected with ~he RF and logic control distrlbution network 80 from the rear side. The cold plate assembly 60, in addition to effecting desired electrical ~ ~`
connections, also provides cooling to the rearward `
parts of the modular radar missile seeker o~ this invention, i.e., the RF and logic distribution network 80 and the monopulse network circuit 82.

- " 212~153 1 Turning once agaln to FIG~ 4 and ~imultaneously to FIGS. SA and 5B, accordlng to ~
preferred embodiment each T/R modulQ 64 i8 built into a complete, stand-alone as~embly incorporating all of the required functione and which assembly ha~ the ovarall ~orm of a generally rectangular prism. The various functional block8 (FIG. 5B), i.e., li~iter, high pow~r amplifier, low noise amplifier, phase and gain ;
ad~uætment, interface circuits, for exa~pl~, ~re included within each module and are lald out over the dept~ of the a~sembly housing 84 (i.~., extQnding alonq the direction from the antenna to the circuits 82).
The riqid cold plate 66 i3 ~ecurQd to the rear surface of each module 64.
An alternative embodiment of modular constructlon i obtained where a plurality of wafer module~ are sandwiched together, each wafer having a given nu~ber of identical and separat~ function block element~ (e.q., limiter, low noise a~plifiers) arranged in a matrix pattern. A nece~ ary nu~ber of interconnection means are provided on one ma~or sur~ace of aach wa~er to enable interconnsction of ~he wafer~
to each otherO The cold plate can be identical to cold plate 66 described ln connection with the first e~bodiment.
It is important to note that in either embodiment of modular construction the lateral dimensions of each module as well as the spacing betweenlmodules in the first embodiment and between ad~acent identical function blocks in the second embodiment, is determined essentially by the spacing of ;~;
the antenna elements 60. Correlating the modul~ sizes `~
to the antenna element spacing enables direct assembly o~ the modular array to the antenna array on a one to one basis. ~

: .

- - 2~21 1~3 : 13 1 ~IRECT ~OMPARISQN_OF PRIOR_aB~

The present invention provides numsrous advantages that are not attainable with the known : : `
systems, including: (1) a modular and C08t effective approach to achieving 3eeker power-apertur~ product, (2) wide bandwidth providing integrated active/pas ive (~RH) guidance, (3) adaptive beam formation to enhance seeker guidance in the presence of, say, stand-o~f ;~
~ammers (SOJ~), (4) enhanced guidance again~t clust~r~d targets, (5) ~eekQr-based fuzing, i.e., integratinq guidance and ~uzing functions into a 8ingle seekor, and ~6) improved reliability and graceful per~ormance degradation through ~unctional redundancy and real-time adaptive compsnsation for failed elements in the array.

1. Modular ~o~struction For a conventlonal radar seeker, the design of . ~
the antenna must b~ custom d2signed to the sp~ci~ic ~ .
application taking into account such factors as the center frequ~ncy, frequency ~andwidth, and aperture size. Th~ present invention is constructed o~
individual activ~ transmit/receiv~ module~ with each , .
module consisting o~ a transmitter element and a sensitiv~ radar receive element. These basic building blocks may be combined together to form an array of any size without having to incur a large design C08t.
! Since the basic parts are made in modular form, the :~
cost of any given radar missile seeker is substantially ; :: .
30 reduced in that it merely requires the assembly of a ~ ~ .
given number of modules to produce the system and does ,~
not require a completely customized design. As a further result of the modular construction, both the ~ ^` 14 2 ~

1 non-recurring and recurrlng oo~t of nQw ~aeker development 1~ reducQd.
Still further, the U~Q 0~ T/R module3 a~
building blocks provides a modular approach to achieving increa~ed power-ap~rture product. For the AESA, increa~inq the ~ize of the array increases both the transmitter power and the antennn g~n ~imultaneously. With existing t~chnology, signific~nt ~:
increase in tha power-aperture product lnvolve d2~ign efforts directed toward developing ~igh powsred transmitters and/or larger antennas. .

2. Wide bandwidth. integra~Ç~ active/~2~i~
(ARH) ~uidance ; ~:
Existing planar array antennas and travelinq ...
wave tube (TWT) transmitters are highly tuned to a specific frequency. Even over relatively modest bandwidths of a few percent, these existing systems experience significant performance degradation at the edge~ o~ the system operating band frequency. On the . :~
other hand, wide bandwid~h i~ inherent in th~ basic design of the present active transmit/rec~iv~ (T~R~
modules and tXey are capable of operating over band~
~ that are tens of percent wide. ~he preferred embodiment benefits from ~hi8 inherently wide :;
bandwidth. Ability to operate over these relatively `~
wide bandwidths allow a mi3sile to derive pas~ive -~
guidance information against emitters being used for defensive purposes which typically operate over a corresponding wide frequency range.
In addition, the wide bandwidth of the preferred embodiment provides enhanced performance in ~ m scenarios with multiple missiles in flight simultaneously or in high radio frequen y interference RFI environments. A wider operating bandwidth may also ~

' ~ ' ; `; :'' . ' ,... '..

~ 21211~3 1 provida per~ormance advantages again3t 30me electronlc `~
counter~easures (ECM) technique~. Forcing an EC~
device to operate over a wider bandwidt~ tend~ to dilute the ~a~ming power in ths mis~ile seeker receiver.

3. Adaptive ~eam formation~ nhance ~ek~r_~Yi~nca in th~ pr~sent o_stand-of~ 1a~mers (SOJ~
The conventional gimballcd s~eker ha~ a fixed antenna sidelobQ re~ponse that 1~ not capable of being modifiad in real-time to counter various defen6ive techniquQs that may be employed. One method availabl~
in the prior ~rt to overcome this problem is to modify ~;~
the flight pa~h o~ the missile in an atte~pt to ad~u~t the geometry with respect to interfering ~ources and .
place them in an antenna null. In the process of doing ..
this, however, overall missile performance is frequ~ntly degraded. On the other hand, the preferred embodiment enableq adjusting both th~ gain and pha~a of ~ -the individual elements o~ tha active array to ~teer antenna nulls in real-ti~e and in ~hat way eliminate :
the interference from off-axis stand-off jammer~, and this is all accomplished without modifying the ~issile ~light path. With reduc~d interference, ~he :~
probability of successful guidance to the desired target iB enhanced.

4. Enhanc~d ouidance aaain~t clustered ~araets :
A conventional gimballed seeker has limited per~ormance against target clusters in that the antenna array is typically divided into four quadrants which are either combined and then processed or processed separately. Only a maximum of three targets can be successfully resolved by this method. With the .
preferred e~bodiment, on the other hand, the array may 2~21~

1 be partitlon~d into multiple aub-array~ which by the use o~ appropriate signal proces~ing can achieve improved guidance to a ~psci~ic target located within a cluster of targets. The number of sub-array~ i8 S det~rmined by th~ BiZ~ of the array and the complexity of the ~ed network, but theoretically can be made arb~trarily large within th~ packaging constraints reguired ~or signal proce~sing. Wit~ separate transmission and receiving capabilitiG~ a~ w~ s individual phase and gain control for ~ach antenna element, ~he seeker can re~olve 8ignal8 r~ceived fro~ a large number of independent target~. Further, by utilizing modern signal processing techniqueq, the ~ -resolution capability is not dependent upon the returns lS coming from comparably sized target~

5. Seçk2r-based fuzinq -- inteqratina quidance and fuzina f~n~ti~ns intG ~ ~ingle_se~
With a conventional gimballed array, it is not practicable to combine ~hQ ~uzing and guidance functions into a single ~eeker. The limiting ~actors include the blind range of the hi~h power seeker, the limited bandwidth of operation, and the difficulty in positioning ~he beam at rates consi3tent wi~h attempting to scan the target to determine optimum burst point. In the present invention, the same i ;~
missile radar system used to detect and track targets can be used to collect the data requisite for computing the optimum burst point for the missile payload warhead. ~he inherent features of the active T/R ~ :
design which allow the fuzing function to be combined with the radar seeker are the small blind range (fast recovery time after triansmit), the wide bandwidth of the T/R modules which supports waveforms that are capable of making precision measurements of target .

21211~3 1 dimensions, and the agility of pointing the ~eeker baam to interroqate t~e target dlmensions.

6. Improved raliabilitY and graceful p*rfor~ançe degrad~tion Comparing FIG5. 1 and 4, it can b~ seen ~hat a ~-substantial reduction in hardwarQ complexity is obtained by use of the present ~nvention over th~ prior ;
art gi~balled pedestal 8y8tem- More particularly, a~
SQen in FIG. 3A, the equipment sp~cifically required for a conventional missile seeker with ~ gimball~d antenna ara those iteFs located in the shaded functional block diagram enumeratcd d6. Co~paring with FIG. 6, the gi~bal torquer motors, servo electronic~
and other mechanical appurtenances necessary for operation of this prior art system have been eli~inated and, in their place, there are predominantly ~
lightweight and relatively inexpensive electron~c `~ `
component~ and circuits shown enclosed in the dotted line part of the circuit enumerated as 88. ~he remainder of the circuit equipment in both cases (i.e., outside 86 and 88) is v~ry much the same Por both ~he gimballed and present invention.
In the conventional gimballed array, ~ailure of any one of a number of critical component6 will result in failur~ of the guided missil~ to be able to complete its mission. The AESA, because it typically is composed of 100 or more identical active modular ``~
elements, will display graceful degradation upon the ;~
failure of any single element. Each element has inherently high reliability, and seeker system reliability is further enhanced since the failure of a single element may be compensated for by adjusting the parameters of gain and phase of it~ "nearest .

s ~ ~

2~2~153 1 neighbors". Th~ 5 feature provides the highly advantageou~ gr~ceful perfor~ance degradation.
In addition, conventional high pow~r glmballed ~eekers that use travelling-wave tuba ~TWT) t~chnology S typically requ~re that the ~eeker be pres3uri~2d in order to preclude trans~itter arcing and subsequent catastrophic failure. In thi~ ca~e, any failure o~ the pressure seal will result in failurQ of the ~18811e seeker and, accordingly, failure of the ~is~ile to co~plete its mission. In the described ~odulsr ~y~tem, becau6e each T/R module has a lower peak power, the requirement ~or pressurization to preclude arcing is eliminated. The active T/R modular technology u3eS
much lower voltages than a TWT transmitter which commonly requires voltages on the order of ten thousand (10,000) volts to operate. Such high voltages requir~
extremely sophisticated ~anufacturing techniques to ;~
ensure that power supply related failures do not occur.
Although the invention has been describ2d in -~
connection with a preferred embodiment, it i~ to be understood that on~ skilled in ~he appertaining arts may make modification~ that come within the ~cope of the inv~ntion a~ descriked and within the ambit o~ th~
appen~ed claims.
, . "" ,.

Claims (15)

1. An active antenna array, comprising:
a plurality of antenna elements unitarily arranged in a general plane facing in a common receiving and transmitting direction; and modular transmitting and receiving circuit means, one for each antenna element, interconnected with the antenna element plane.

2. An active antenna array as in claim 1, in which each modular circuit means include separate apparatus for accomplishing transmission and receipt of radar signals handled by a given antenna element.

3. An active antenna array as in claim 2, in which the modular circuit means are electrically identical and each enclosed within a separate stand alone housing of identical dimensions and geometry.

4. An active antenna array as in claim 2, in which each module circuit means includes a plurality of wafers, each wafer including a plurality of identical function block circuits arranged in a matrix and function block circuits for the different wafer being selectively different, said wafers being unitarily interconnected together with a function block circuit of each wafer being aligned with a function block circuit of an adjacent wafer.

5. An active antenna array as in claim 1, in which each modular transmitting and receiving circuit means is individually adjustable as to phase and gain.

6. An active antenna array as in claim 1, in which heat absorption means are positioned in heat transferring relation to each modular transmitting and receiving circuit means.

7. An active antenna array as in claim 1, in which each modular transmitting and receiving circuit includes a duplexer connected to an antenna element for providing alternately switched connection of the same antenna element through a high power amplifier and a low noise amplifier in series with first a variable phase control and then a variable gain control.

8. An active antenna array as in claim 4, in which each modular transmitting and receiving circuit means is individually adjustable as to phase and gain.

9. An active antenna array as in claim 4, in which heat absorbing means are positioned in heat transferring relation to the modular transmitting and receiving circuit means.

10. An active antenna array of variable transmitter power and antenna gain, comprising:
a given plurality of modular antenna elements arranged in a uniform spaced apart relation forming a planar array of given areal extent for achieving a predetermined power and antenna gain;
an identical plurality of transmitting and receiving circuit modules, each module individually physically and electrically interconnected to a single antenna element; and cold plate means physically interconnected with the circuit modules forming a unitary arrangement of the circuit modules and antenna elements.

11. An active antenna array as in claim 10, in which each circuit module includes a generally rectangular prism housing enclosing individual transmitting and receiving circuits for the said interconnected antenna element.

12. An active antenna array as in claim 11, in which the circuit modules are identical to each other.

13. An active antenna array as in claim 10, in which each circuit module is individually adjustable as to phase and gain.

14. An active antenna array as in claim 13, in which each circuit module is secured to individually different antenna elements.

15. An active antenna array as in claim 10, in which each circuit module includes a duplexer connected to an antenna element for effecting alternate connection through a high power amplifier and a low noise amplifier, both of which are serially arranged with a variable phase control followed by a variable gain control.