Low profile active electronically scanned antenna (AESA) for Ka-band radar systems

[0001] This invention relates generally to radar and communication systems and more particularly to an active phased array radar system operating in the Ka-band above 30 GHz.

[0002] Active electronically scanned antenna (AESA) arrays are generally well known. Such apparatus typically requires amplifier and phase shifter electronics that are spaced every half wavelength in a two dimensional array. Known prior art AESA systems have been developed at 10 GHz and below, and in such systems, array element spacing is greater than 0.8 inches and provides sufficient area for the array electronics to be laid out on a single circuit layer. However, at Ka-band (>30 GHz), element spacing must be in the order of 0.2 inches or less, which is less than {fraction (1/10)} of the area of an array operating at 10 GHz.

[0003] Accordingly, previous attempts to design low profile electronically scanned antenna arrays for ground and air vehicles and operating at Ka-band have experienced what appears to be insurmountable difficulties because of the small element spacing requirements. A formidable problem also encountered was the extraction of heat from high power electronic devices that would be included in the circuits of such a high density array. For example, transmit amplifiers of transmit/receive (T/R) circuits in such systems generate large amounts of heat which much be dissipated so as to provide safe operating temperatures for the electronic devices utilized.

[0004] Because of the difficulties of the extremely small element spacing required for Ka-band operation, the present invention overcomes these inherent problems by vertical integration of the array electronics which is achieved by sandwiching multiple mutually parallel layers of circuit elements together against an antenna faceplate. By planarizing T/R channels, RF signal manifolds and heat sinks, the size and particularly the depth of the entire assembly can be significantly reduced while still providing the necessary cooling for safe and efficient operation.

[0005] Accordingly, it is an object of the present invention to provide an improvement in high frequency phased array radar systems.

[0006] It is another object of the invention to provide an architecture for an active electronically scanned phased array radar system operating in the Ka-band of frequencies above 30 GHz.

[0007] It is yet another object of the invention to provide an active electronically scanned phased array Ka-band radar system having a multi-function capability for use with both ground and air vehicles.

[0008] These and other objects are achieved by an architecture for a Ka-band multi-function radar system (KAMS) comprised of multiple parallel layers of electronics circuitry and waveguide components which are stacked together so as to form a unitary structure behind an antenna faceplate. The invention includes the concepts of vertical integration and solderless interconnects of active electronic circuits while maintaining the required array grid spacing for Ka-band operation and comprises, among other things, a transitioning RF waveguide relocator panel located behind a radiator faceplate and an array of beam control tiles respectively coupled to one of a plurality of transceiver modules via an RF manifold. Each of the beam control tiles includes respective high power transmit/receive (T/R) cells as well as RF stripline and coaxial transmission line elements. In the preferred embodiment of the invention, the waveguide relocator panel is comprised of a diffusion bonded copper laminate stack up with dielectric filling while the beam control tiles are fabricated by the use of multiple layers of low temperature co-fired ceramic (LTCC) material laminated together and designed to route RF signals to and from a respective transceiver module of four transceiver modules and a quadrature array of antenna radiators matched to free space formed in the faceplate. Planar type metal spring gaskets are provided between the interfacing layers so as to prevent RF leakage from around the perimeter of the waveguide ports of abutting layer members. Cooling of the various components is achieved by a pair of planar forced air heat sink members which are located on either side of the array of beam control tiles. DC power and control of the T/R cells is provided by a printed circuit wiring board assembly located adjacent to the array of beam controlled tiles with solderless DC connections being provided by an arrangement of fuzz button electrical connector elements. Alignments pins are provided at different levels of the planar layers to ensure that waveguide, electrical signals and power interface properly.

[0009] Further scope of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood, however, that the detailed description and specific example while indicating the preferred embodiment of the invention, it is provided by way of illustration only since various changes and modifications coming within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

[0010] The present invention will become more fully understood when the detailed provided hereinafter is considered in connection with the accompanying drawings, which are provided by way of illustration only and are thus not meant to be considered in a limiting sense, and wherein:

[0011] FIG. 1 is an electrical block diagram broadly illustrative of the subject invention;

[0012] FIG. 2 is an exploded perspective view of the various planar type system components of the preferred embodiment of the invention;

[0013] FIG. 3 is a simplified block diagram showing the relative positions of the system components included in the embodiment shown in FIG. 1;

[0014] FIG. 4 is a perspective view illustrative of the antenna faceplate of the embodiment shown in FIG. 2;

[0015] FIGS. 5A-5C are diagrams illustrative of the details of the radiator elements in the faceplate shown in FIG. 4;

[0016] FIG. 6 is a plan view of a first spring gasket member which is located between the faceplate shown in FIG. 4 and a waveguide relocator panel;

[0017] FIGS. 7A and 7B are plan views illustrative of the front and back faces of the waveguide relocator panel;

[0018] FIG. 7C is a perspective view of one of sixteen waveguide relocator sub-panel sections of the waveguide relocator panel shown in FIGS. 7A and 7B;

[0019] FIGS. 8A-8C are diagrams illustrative of the details of the waveguide relocator sub-panel shown in FIG. 7C;

[0020] FIG. 9 is a plan view of a second spring gasket member located between the waveguide relocator panel shown in FIGS. 7A and 7B and an outer heat sink member which is shown in FIG. 2;

[0021] FIG. 10 is a perspective view of the outer heat sink shown in FIG. 2;

[0022] FIG. 11 is a plan view illustrative of a third set of five spring gasket members located between the underside of the outer heat sink shown in FIG. 10 and an array of sixteen co-planar beam control tiles shown located behind the heat sink in FIG. 2;

[0023] FIG. 12 is a perspective view of the underside of the outer heat sink shown in FIG. 10 with the third set of spring gaskets shown in FIG. 11 attached thereto as well as one of sixteen beam control tiles;

[0024] FIG. 13 is a perspective view of the beam control tile shown in FIG. 12;

[0025] FIGS. 14A-14J are top plan views illustrative of the details of the ceramic layers implementing the RF, DC bias and control signal circuit paths of the beam control tile shown in FIG. 13;

[0026] FIG. 15 is a plan view of the circuit elements included in a transmit/receive (T/R) cell located on a layer of the beam control tile shown in FIG. 14C;

[0027] FIG. 16 is a side plan view illustrative of an RF transition element from a T/R cell such as shown in FIG. 15 to a waveguide in the beam control tile shown in FIG. 141;

[0028] FIGS. 17A and 17B are perspective views further illustrative of the RF transition element shown in FIG. 16;

[0029] FIG. 18 is a perspective view of a dagger load for a stripline termination element included in the layer of the beam control tile shown in FIG. 13;

[0030] FIGS. 19A and 19B are perspective side views illustrative of the details of RF routing through various layers of a beam control tile;

[0031] FIG. 20 is a perspective view of an array of sixteen beam control tiles mounted on the underside of the outer heat sink shown in FIG. 12 together with a set of DC connector fuzz button boards secured thereto;

[0032] FIG. 21 is a perspective view of the underside of the assembly shown in FIG. 20, with a DC printed wiring board additionally secured thereto;

[0033] FIG. 22 is a plan view of one side of the DC wiring board shown in FIG. 21, with the fuzz button boards shown in FIG. 20 attached thereto;

[0034] FIG. 23 is a plan view of a fourth set of four spring gasket members located between the array of beam control tiles and the DC printed wiring board shown in FIG. 21;

[0035] FIG. 24 is a longitudinal central cross-sectional view of the arrangement of components shown in FIG. 21;

[0036] FIG. 25 is an exploded perspective view of a composite structure including an inner heat sink and an array RF manifold;

[0037] FIG. 26 is a top planar view of the inner heat sink shown in FIG. 25;

[0038] FIGS. 27A and 27B are perspective and side elevational views illustrative of one of the RF transition elements located in the face of heat sink member shown in FIG. 26;

[0039] FIG. 28 is a top planar view of the inner face of the RF manifold shown in FIG. 25 including a set of four magic tee RF waveguide couplers formed therein; and

[0040] FIG. 29 is a perspective view of one of four transceiver modules affixed to the underside of the RF manifold shown in FIGS. 25 and 28.

[0041] Referring now to the various drawing figures wherein like reference numerals refer to like components throughout, reference is first made to FIG. 1 wherein there is shown an electrical block diagram broadly illustrative of the subject invention and which is directed to a Ka-band multi-function system (KAMS) active bidirectional electronically scanned antenna (AESA) array utilized for both transmitting and receiving RF signals to and from a target.

[0042] In FIG. 1, reference numeral 30 denotes a transceiver module sub-assembly comprised of four transceiver modules 32₁ . . . 32₄, each including an input terminal 34 for RF signals to be transmitted, a local oscillator input terminal 36 and a receive IF output terminal 38. Each transceiver module, for example module 32₁, also includes a frequency doubler 40, transmit RF amplifier circuitry 42, and a transmit/receive (T/R) switch 44. Also included is receive RF amplifier circuitry 46 coupled to the T/R switch 44. The receive amplifier 46 is coupled to a second harmonic (X2) signal mixer 48 which is also coupled to a local oscillator input terminal 36. The output of the mixer 48 is connected to an IF amplifier circuit 50, whose output is coupled to the IF output terminal 38. The transmit RF signal applied to the input terminal 34 and the local oscillator input signal applied to the terminal 36 is generated externally of the system and the IF output signal is also utilized by well known external circuitry, not shown.

[0043] The four transceiver modules 32₁ . . . 32₄ of the transceiver module section 30 are coupled to an RF manifold sub-assembly 52 consisting of four manifold sections 54₁ . . . 54₄, each comprised of a single port 56 coupled to a T/R switch 44 of a respective transceiver module 32 and four RF signal ports 58₁ . . . 58₄ which are respectively coupled to one beam control tile 60 of a set 62 of sixteen identical beam control tiles 60₁ . . . 601₆ arranged in a rectangular array, shown in FIG. 2.

[0044] Each of the beam control tiles 60₁ . . . 60₁₆ implements sixteen RF signal channels 64₁ . . . 64₁₆ so as to provide an off-grid cluster of two hundred fifty-six waveguides 66₁ . . . 66₂₅₆ which are fed to a grid of two hundred fifty-six radiator elements 67₁ . . . 67₂₅₆ in the form of angulated slots matched to free space in a radiator faceplate 68 via sixteen waveguide relocator sub-panel sections 70₁ . . . 70₁₆ of a waveguide relocator panel 69 shown in FIGS. 7A and 7B. The relocator panel 69 relocates the two hundred fifty six waveguides 66₁ . . . 66₂₅₆ in the beam control tiles 64₁ . . . 64₁₆ back on grid at the faceplate 68 and which operate as a quadrature array with the four transceiver modules 32₁ . . . 32₄.

[0045] The architecture of the AESA system shown in FIG. 1 is further illustrated in FIG. 2 and comprises an exploded view of the multiple layers of planar components that are stacked together in a vertically integrated assembly with metal spring gasket members being sandwiched between interfacing layers or panels of components to ensure the electrical RF integrity of the waveguides 66₁ . . . 66₂₅₆ through the assembly. In addition to the transceiver section 30, the manifold section 52, the beam control tile array 62, the waveguide relocator panel 69, and the faceplate 68 referred to in FIG. 1, the embodiment of the invention includes a first spring gasket member 72 fabricated from beryllium copper (BeCu) located between the antenna faceplate 68 and the waveguide relocator panel 69, a second BeCu spring gasket member 74 located between the waveguide relocator panel 69 and an outer heat sink member 76, a third set of BeCu spring gasket members 78₁ . . . 7₈₅ which are sandwiched between the array 62 of beam control tiles 60₁ . . . 60₁₆, and a fourth set of four BeCu spring gasket members 82₁ . . . 82₄ which are located beneath the beam control tile array 62 and a DC printed wiring board 84 which includes an assembly of DC fuzz button connector boards 80 mounted thereon. Beneath the printed wiring board 84 is an inner heat sink 86 and the RF manifold section 52 referred to above and which is followed by the transceiver module assembly 30 which is shown in FIG. 2 including one transceiver module 32₁, of four modules 32₁ . . . 32₄ shown in FIG. 1. When desirable, however, the antenna faceplate, the relocator panel, and outer heat could be fabricated as a single composite structure.

[0046] The relative positions of the various components shown in FIG. 2 are further illustrated in block diagrammatic form in FIG. 3. In the diagram of FIG. 3, the fuzz button boards 80 and the fourth set of spring gasket members 82 are shown in a common block because they are placed in a coplanar sub-assembly between the array 62 of beam control tiles 60₁ . . . 60₄ and the inner heat sink 86. The inner heat sink 86 and the RF manifold 52 are shown in a common block of FIG. 3 because they are comprised of members which, as will be shown, are bonded together so as to form a composite mechanical sub-assembly.

[0047] Referring now to the details of the various components shown in FIG. 2, FIGS. 4 and 5A-5C are illustrative of the antenna faceplate 68 which consists of an aluminum alloy plate member 88 and which is machined to include a grid of two hundred fifty six radiator elements 67₁ . . . 67₂₅₆ which are matched to free space and comprise oblong slots having rounded end portions. As shown in FIGS. 5A and 5B, each radiator slot 67 includes an impedance matching step 90 in the width of the outer end portion 92. The outer surface 94 of the aluminum plate 88 includes a layer of foam material 96 which is covered by a layer of dielectric 98 that provides wide angle impedance matching (WAIM) to free space.

[0048] Dielectric adhesive layers 95 and 99 are used to bond the foam material 96 to the plate 88 and WAIM layer 98. Reference numerals 100 and 102 in FIG. 4 refer to a set of mounting and alignment holes located around the periphery of the grid of radiator elements 67₁ . . . 67₂₅₆.

[0049] Referring now to FIG. 6, located immediately below and in contact with the antenna faceplate 68 is the first Be-Cu spring gasket member 72 which is shown having a grid 104 of two hundred fifty six elongated oblong openings 106₁ . . . 106₂₅₆ which are mutually angulated and match the size and shape of the radiator elements 67₁ . . . 67₂₅₆ formed in the faceplate 68. The spring gasket 72 also includes a set of mounting holes 108 and alignment holes 110 formed adjacent the outer edges of the openings which mate with the mounting holes 100 and alignment holes 102 in the faceplate 68.

[0050] Immediately adjacent the first spring gasket member 72 is the waveguide relocator panel 69 shown in FIGS. 7A and 7B 69 comprised of sixteen waveguide relocator sub-panel sections 70₁ . . . 70₁₆, one of which is shown in FIG. 7C. FIG. 7A depicts the front face of the relocator panel 69 while FIG. 7B depicts the rear face thereof.

[0051] The relocator panel 69 is preferably comprised of multiple layers of diffusion bonded copper laminates with dielectric filling. However, when desired, multiple layers of low temperature co-fired ceramic (LTCC) material or high temperature co-fired ceramic (HTCC) or other suitable ceramic material could be used when desired, based upon the frequency range of the tile application.

[0052] As shown in FIG. 7C, each relocator sub-panel section 70 includes a rectangular grid of sixteen waveguide ports 112₁ . . . 112₁₆ slanted at 45 and located in an outer surface 114. The waveguide ports 112₁ . . . 112₁₆ are in alignment with a corresponding number of radiator elements 67 in the faceplate 68 and matching openings 106₁ . . . 106₂₅₆ in the spring gasket 72 (FIG. 6).

[0053] The waveguide ports 112₁ . . . 112₁₆ transition to two linear mutually offset sets of eight waveguide ports 116₁ . . . 116₈ and 116₉ . . . 116₁₆, shown in FIGS. 8A-8C, located on an inner surface 118. The waveguide ports 116₁ . . . 116₈ and 116₉ . . . 116₁₆ couple to two like linear mutually offset sets of eight waveguide ports 122₁ . . . 122₈ and 122₉ . . . 122₁₆ on the outer edge surface portions 124 and 126 of the beam control tiles 60₁ . . . 60₁₆, one of which is shown in FIG. 13. Such an arrangement allows room for sixteen transmit/receive (T/R) cells, to be described hereinafter, to be located in the center recessed portion 128 of each of the beam control tiles 60₁ . . . 60₁₆. The relocator sub-panel sections 70₁ . . . 70₁₆ of the waveguide relocator panel 69 thus operate to realign the ports 122₁ . . . 122₁₆ of the beam control tiles 60₁ . . . 60₁₆ from the side thereof back on to the grid 104 of the spring gasket 72 (FIG. 6) and the radiator elements 67 in the faceplate 68.

[0054] As further shown in FIGS. 8A-8C, each relocator sub-panel section 70 includes two sets of eight waveguide transitions 130₁ . . . 130₈ and 132₁ . . . 132₈ formed therein by successive incremental angular rotation, e.g., 45/251.8 of the various rectangular waveguide segments formed in the panel layers. The transitions 130 comprise vertical transitions, while the transitions 132 comprise both vertical and lateral transitions. As shown, the vertical and lateral transitions 130₁ . . . 130₈ and 132₁ . . . 132₈ terminate in the mutually parallel ports 112₁ . . . 112₁₆ matching the openings 106 in the spring gasket 72 shown in FIG. 6 as well as the radiator elements 67 in the faceplate 68.

[0055] Referring now to FIG. 9, shown thereat is the second BeCu spring gasket member 74 which is located between the inner face of the waveguide relocator panels 69 shown in FIG. 7B and the outer surface of the outer heat sink member 76 shown in FIG. 10. The spring gasket 74 includes five sets 136₁ . . . 136₅ of rectangular openings 138 which are arranged to mate with the ports 116₁ . . . 116₁₆ of the relocator sub-panel sections 70₁ . . . 70₁₆. The five sets 136₁ . . . 136₅ of openings 138 are adapted to also match five like sets 140₁ . . . 140₅ of waveguide ports 142 in the outer surface 134 of the outer heat sink 76 and which form portions of five sets of RF dielectric filled waveguides, not shown, formed in the raised elongated parallel heat sink body portions 144₁ . . . 144₅.

[0056] Referring now to FIG. 11, shown thereat is a third set of five discrete BeCu spring gasket members 78₁, 78₂ . . . 78₅ which are mounted on the back surface 146 of the outer heat sink 76 as shown in FIG. 12 and include rectangular opening 148 which match the arrangement of openings 138 in the second spring gasket 74 shown in FIG. 9 as well as the waveguide ports 143 in the heat sink 76 and the dielectric filled waveguides, not shown, which extend through the body portions 144₁ . . . 144₅ to the inner surface 146 as shown in FIG. 12. FIG. 12 also shows for sake of illustration one beam control tile 60 (FIG. 13) located on the inner surface 146 of the outer heat sink 76 against the spring gasket members 78₄ and 78₅. It is to be noted, however, that sixteen identical beam control tiles 60₁ . . . 60₁₆ as shown in FIG. 13 are actually assembled side by side in a rectangular array on the back surface of the heat sink 76.

[0057] Considering now the construction of the beam control tiles 60₁ . . . 60₁₆, one of which is shown in perspective view in FIG. 13 by reference numeral 60, it is preferably fabricated from multiple layers of LTCC material. When desired however, high temperature co-fired ceramic (HTCC) material could be used. As noted above, each beam control tile 60 of the tiles 60₁ . . . 60₁₆ includes sixteen waveguide ports 122₁ . . . 122₁₆ and associated dielectric waveguides 123₁ . . . 123₁₆ arranged in two offset sets of eight waveguide ports 122₁ . . . 122₈ and 122₉ . . . 122₁₆ mutually supported on the outer surface portions 124 and 126 of an outermost layer 150.

[0058] Referring now to FIG. 14A, shown thereat is a top plan view of the beam control tile 60 shown in FIG. 13. Under the centralized generally rectangular recessed cavity region 128 is located sixteen T/R chips 166₁ . . . 166₁₆, fabricated in gallium arsenide (GaAs), located on an underlying layer 152 of the beam control tile 60 as shown in FIG. 14B. The layer 150 shown in FIG. 14A including the outer surface portions also includes metallic vias 170 which pass through the various LTCC layers so as to form RF via walls on either side of two sets of buried stripline transmission lines 174₁ . . . 174₈ and 174₉ . . . 174₁₆ located on layer 152 (FIG. 14B). The walls of the vias 170 ensure that RF signals do not leak from one adjacent channel to another. Also, shown in an arrangement of vias 172 which form two sets of the eight RF waveguides 123₁ . . . 123₈, and 123₉ . . . 123₁₆ shown in FIG. 13. Two separated layers of metallization 178 and 180 are formed on the outer surface portions 124 and 126 overlaying the vias 170 and 172 and act as shield layers.

[0059] FIG. 14B shows the next underlying layer 152 of the beam control tile 60 where sixteen GaAs T/R chips 166₁ . . . 166₁₆ are located in the cavity region 128. The T/R chips 166₁ . . . 166₁₆ will be considered subsequently with respect to FIG. 15. The layer 152, as shown, additionally includes the metallization for the sixteen waveguides 123₁ . . . 123₈ and 123₉ . . . 123₁₆ overlaying the vias 172 shown in FIGS. 14A, 14C and 14E as well as the stripline transmission line elements 174₁ . . . 174₈ and, 174₉ . . . 174₁₆ which terminate in respective waveguide probe elements 175₁ . . . 175₈ and 175₉ . . . 175₁₆.

[0060] In FIG. 14B, four coaxial transmission line elements 186₁ . . . 186₄ including outer conductor 184₁ . . . 184₄ and center conductors 188₁ . . . 188₄ are shown in central portion of the cavity region 128. The center conductors 188₁ . . . 188₄ are connected to four RF signal dividers 190₁ . . . 190₄ which may be, for example, well known Wilkinson signal dividers which couple RF signals between the T/R chips 166₁ . . . 166₁₆ and the coaxial transmission lines 186₁ . . . 186₄. DC control signals are routed within the beam control tile 60 and surface in the cavity region 128 and are bonded to the T/R chips with gold bond wires 192 as shown. Also shown in FIG. 14B are four alignment pins 196₁ . . . 196₄ located at or near the corners of the tile 60.

[0061] Referring now to FIG. 14C, shown thereat is a tile layer 198 below layer 152 (FIG. 14B). Layer 198 contains the configuration of vias 172 that are used to form walls of waveguides 123₁ . . . 123₄. In addition, a plurality of vias 202 are placed close together to form a slot in the dielectric layer so as to ensure that a good ground is presented for the T/R chips 166₁ . . . 166₁₆ shown in FIG. 14B at the point where RF signals are coupled between the T/R chips 166₁ . . . 166₁₆ and the waveguides 123₁ . . . 123₄ to the respective chips. Another set of via slots 204 are included in the outer conductor portions 184₁ . . . 184₄ of the coaxial transmission line elements 186₁ . . . 186₄ to produce a capacitive matching element so as to provide a match to the bond wires connecting the RF signal dividers 190₁ . . . 190₄ to the inner conductor elements 188₁ . . . 188₄ as shown in FIG. 14B. Also, there is provided a set of vias 206 for providing grounded separation elements between the overlying T/R chips 166₁ . . . 166₁₆.

[0062] Turning attention now to FIG. 14D, shown thereat is a buried ground layer 208 which includes a metallized ground plane layer 210 of metallization for walls of the waveguides 123₁ . . . 123₄, the underside of the active T/R chips 166₁ . . . 166₁₆ as well as the coaxial transmission line elements 186₁ . . . 186₄, Also provided on the layer 208 is an arrangement of DC connector points 211 for the various components in the T/R chips 166₁ . . . 166₁₆. Portions of the center conductors 188₁ . . . 188₄ and the outer conductors 184₁ . . . 184₄ for the coaxial transmission line elements 186₁ . . . 186₄ are also formed on layer 208.

[0063] Beneath the ground plane layer 208 is a signal routing layer 214 shown in FIG. 14E which also includes the vertical vias 172 for the sixteen waveguides 123₁ . . . 123₄. Also shown are vias of the inner and outer conductors 188₁ . . . 188₄ and 184₁ . . . 184₄ of the four coaxial transmission lines 186₁ . . . 186₄, Also located on layer 214 is a pattern 219 of stripline members for routing DC control and bias signals to their proper locations.

[0064] Below layer 214 is dielectric layer 220 shown in FIG. 14F which is comprised of sixteen rectangular formations 222₁ . . . 222₁₆ of metallization further defining the side walls of the waveguides 176₁ . . . 176₁₆ along with the vias 172 shown in FIGS. 14A, 14C and 14E. Four rings of metallization are shown which further define the outer conductors 184₁ . . . 184₄ of the coaxial lines 186₁ . . . 186₄ along with vias forming the center conductors 188₁ . . . 188₄. Also shown are patterns 226 of metallization used for routing DC signals to their proper locations.

[0065] Referring now to FIG. 14G, shown thereat is a dielectric layer 230 which includes a top side ground plane layer 232 of metallization for three RF branch line couplers shown in the adjacent lower dielectric layer 236 shown in FIG. 14H by reference numerals 234₁, 234₂, 234₃. The layer of metallization 232 also includes a rectangular portion of metallization 237 for defining the waveguide walls of a single waveguide 238 on the back side of the beam control tile 60 for routing RF between one of the four transceiver modules 32₁ . . . 32₄ (FIG. 2) and the sixteen waveguides 123₁ . . . 123₄, shown, for example, in FIGS. 14A-14F. FIG. 14G also includes a pattern 240 of metallization for providing tracks for DC control of bias signals in the tile 60. Also, shown in FIG. 14G are metallizations for the vias of the four center conductors 188₁ . . . 188₄ of the four coaxial transmission line elements 186₁ . . . 186₄.

[0066] With respect to FIG. 14H, shown thereat are the three branch couplers 234₁, 234₂ and 234₃, referred to above. These couplers operate to connect an RF via waveguide probe 242 within the backside waveguide 238 to four RF feed elements 244₁ . . . 244₄ which vertically route RF to the four RF coaxial transmission lines 186₁ . . . 186₄ in the tile structure shown in FIGS. 14D-14G. The three branch line couplers 234₁, 234₂, 234₃ are also connected to respective dagger type resistive load members 246₁, 246₂ and 246₃ shown in further detail in FIG. 18. All of these elements are bordered by a fence of metallization 248. As in the metallization of FIG. 14G, the right hand side of the layer 14H also includes a set of metal metallization tracks 250 for DC control and bias signals.

[0067] FIG. 141 shows an underlying via layer 252 including a pattern 254 of buried vias 255 which are used to further implement the fence 248 shown in FIG. 14I along with vias for the center conductors 188₁ . . . 188₄ of the coaxial lines 186₁ . . . 186₄. The dielectric layer 252 also includes three parallel columns of vias 256 which interconnect with the metallization patterns 240 and 250 shown in FIGS. 14G and 14H.

[0068] The back side or lowermost dielectric layer of the beam control tile 60 is shown in FIG. 14J by reference numeral 258 and includes a ground plane 260 of metallization having a rectangular opening defining a port 262 for the backside waveguide 238. A grid array 262 of circular metal pads 264 are located to one side of layer 258 and are adapted to mate with a fuzz button connector element on a board 80 shown in FIG. 2 so as to provide a solderless interconnection means for electrical components in the tile 60. Also located on the bottom layer 258 are four control chips 266₁ . . . 266₄ which are used to control the T/R chips 166₁ . . . 166₁₆ shown in FIG. 14B.

[0069] Having considered the various dielectric layers in the beam control tile 60, reference is now made to FIG. 15 where there is shown a layout of one transmit/receive (T/R) chip 166 of the sixteen T/R chips 166₁ . . . 166₁₆ which are fabricated in gallium arsenide (GaAs) semiconductor material and are located on dielectric layer 182 shown in FIG. 14C. As shown, reference numeral 268 denotes a contact pad of metallization on the left side of the chip which connects to a respective signal divider 190 of the four signal dividers 190₁ . . . 190₄ shown in FIG. 14C. The contact pad 268 is connected to a three-bit RF signal phase shifter 270 implemented with microstrip circuitry including three phase shift segments 272₁, 272₂ and 272₃. Control of the phase shifter 270 is provided DC control signals coupled to four DC control pads 274₁ . . . 274₄. The phase shifter 270 is connected to a first T/R switch 276 implemented in microstrip and is coupled to two DC control pads 278₁ and 278₂ for receiving DC control signals thereat for switching between transmit (Tx) and receive (Rx) modes. The T/R switch 276 is connected to a three stage transmit (Tx) amplifier 280 and a three stage receive (Rx) amplifier 282, respectively implemented with the microstrip circuit elements and P type HEMT field effect transistors 284₁ . . . 284₃ and 286₁ . . . 286₃. A pair of control voltage pads 288₁ and 288₂ are utilized to supply gate and drain power supply voltages to the transmit (Tx) amplifier 280, while a pair of contact pads 290₁ and 290₂ supply gate and drain voltages to semiconductor devices in the RF receive (Rx) amplifier 282. A second T/R switch 292 is connected to both the Tx and Rx RF amplifiers 280 and 282, which in turn is connected via contact pad 294 to one of the sixteen transmission lines 174₁ . . . 174₁₆ shown in FIG. 14C which route RF signals to and from the waveguides 176₁ . . . 176₁₆.

[0070] FIGS. 16, 17A and 17B are illustrative of the microstrip and stripline transmission line components forming the transition from a T/R chip 166 in a beam control tile 60 to the waveguide probe 175 at the tip of transmission line element 174 in one of the waveguides 123 of the sixteen waveguides 123₁ . . . 123₄ (FIG. 14B). Reference numeral 125 denotes a back short for the waveguide member 123 As shown, the transition includes a length of microstrip transmission line 296 formed on the T/R chip 166 which connects to a microstrip track section 298 via a gold bond wire 300 in an air portion 302 of the beam control tile 60 where it then passes between a pair of adjoining layers 304 and 306 of LTCC ceramic material including an impedance matching segment 173 where it connects to the waveguide probe 175 shown in FIG. 17A. As shown in FIGS. 16 and 17A, the waveguide 123 is coupled upwardly to the antenna faceplate 68 through the relocator panel 69.

[0071] Considering briefly FIG. 18, it discloses the details of one of the dagger load elements 246 of the three dagger loads 246₁, 246₂ and 246₃ shown in FIG. 14H connected to one leg of the branch line couplers 234₁, 234₂, and 234₃. The dagger load element 246 consists of a tapered segment 308 of resistive material embedded in multilayer LTCC material 310. The narrow end of the resistor element 308 connects to a respective branch line coupler 234 of the three branch line couplers 234₁, 234₂, and 234₃ shown in FIG. 14H via a length of stripline material 312.

[0072] Referring now to FIGS. 19A and 19B, shown thereat are the details of the manner in which the coaxial RF transmission lines 186₁ . . . 186₄, shown for example in FIGS. 14B-14G, are implemented through the various dielectric layers so as to couple arms 245₁ . . . 245₄ of the branch line couplers 234₁ . . . 234₃ of FIG. 14H to the signal dividers 190₁ . . . 190₄ shown in FIG. 14B. As shown, a stripline connection 314 is made to a signal divider 190 via multiple layers 316 of LTCC material in which are formed arcuate center conductors 188 and the outer conductors 184 of a coaxial waveguide member 186 and terminating in the stripline 245 of a branch line coupler 234 so that the upper and lower extremities are offset from each other. Reference numeral 204 denotes the capacitive matching element shown in FIG. 14C.

[0073] Considering now the remainder of the planar components of the embodiment of the invention shown in FIG. 2, FIG. 20, for example, discloses the underside surface 146 of the outer heat sink member 76, previously shown in FIG. 12. However, FIG. 20 now depicts sixteen beam control tiles 60₁, 60₂, . . . 60₁₆ mounted thereon, being further illustrative of the array 62 of control tiles shown in FIG. 2. Beneath the beam control tiles 60₁ . . . 60₁₆ are the five spring gasket members 78₁ . . . 78₅ shown in FIG. 11. FIG. 20 now additionally shows a set of four fuzz button connector boards 80₁, 80₂, . . . 80₄ in place against sets of four beam control tiles 60₁ . . . 60₁₆ of the array 62.

[0074] FIG. 21 further shows the DC printed wiring board 84 covering the fuzz button boards 80₁ . . . 80₄ shown in FIG. 20. FIG. 21 additionally shows a pair of dual in-line pin connectors 85₁ and 85₂. FIG. 22 is illustrative of the underside of the DC wiring board 84 with the four fuzz button boards 80₁, 80₂, 80₃, and 80₄ shown in FIG. 20.

[0075] Referring now to FIG. 23, shown thereat is the set of fourth BeCu spring gasket members 82₁, 82₂, 82₃, and 82₄ which are mounted coplanar and parallel with the fuzz button boards 80₁, 80₂, 80₃ and 80₄ shown in FIG. 20. Each of gasket members 82₁ . . . 82₄ include four rectangular openings 83₁ . . . 83₄ which are aligned with the four sets of rectangular openings 87₁, 87₂, 87₃; in the DC wiring board 84. A cross section of the sub-assembly of the components shown in FIGS. 21-23 is shown in FIG. 24.

[0076] Mounted on the underside of the DC wiring board 84 is the inner heat sink member 86 which is shown in FIG. 25 together with the RF manifold 52 which is bonded thereto so as to form a unitary structure. The inner heat sink member 86 comprises a generally rectangular body member fabricated from aluminum and includes a cavity 88 with four cross ventilating air cooled channels 87₁. 87₂, 87₃ and 87₄ formed therein for cooling an array of sixteen outwardly facing dielectric waveguide to air waveguide transitions 89₁ . . . 89₁₆ as well as DC chips and components mounted on the wiring board 84 which are also shown in FIG. 26 which couple to the waveguides 238 (FIG. 14K) of the wave control tiles 60₁ . . . 60₁₆.

[0077] The details of one of the transitions 89 is shown in FIGS. 27A and 27B. The transitions 89 as shown include a dielectric waveguide to air waveguide RF input portion 91 which faces outwardly from the cavity 88 as shown in FIG. 25 and is comprised of a plurality of stepped air waveguide matching sections 93 up to an elongated relatively narrow RF output portion 95 including an output port 97. Output ports 97₁ . . . 97₁₆ for the sixteen transition 89₁ . . . 89₁₆ are shown in FIG. 26 and which couple to a respective backside dielectric waveguide 238 such as shown in FIG. 14K through spring gasket members 82 of the sixteen beam control tiles 60₁ . . . 60₁₆. Reference numerals 238 and 242 shown in FIGS. 27A and 27B respectively represent the waveguides and the stripline probes shown in FIG. 141.

[0078] Considering now the RF manifold section 52 referred to in FIG. 1, the details thereof are shown in FIGS. 25 and 28. The manifold 52 coincides in size with the inner heat sink member 86 and includes a generally rectangular body portion 51 formed of aluminum and which is machined to include two channels 53₁ and 53₂ formed in the underside thereof so as to pass air across the body portion 51 so as to provide cooling. As shown, the manifold member 52 includes four magic tee waveguide couplers 54₁ . . . 54₄, each having four arms 57₁ . . . 57₄ as shown in FIG. 28 coupled to RF signal ports 56₁ . . . 56₄ and which are fabricated in the top surface 63 so as to face the inner heat sink 52 as shown in FIG. 25. The RF signal ports 56₁ . . . 56₄ of the magic tee couplers 54₁ . . . 54₄ respectively couple to an RF input/output port 35 shown in FIG. 29 of a transceiver module 32 which comprises one of four transceiver modules 32₁ . . . 32₄ shown schematically in FIG. 1.

[0079] The transceiver module 32 shown in FIG. 29 is also shown including terminals 34, 36 and 38, which couple to transmit, local oscillator and IF outputs shown in FIG. 1. Also, each transceiver module 32 includes a dual in-line pin DC connector 37 for the coupling of DC control signals thereto.

[0080] Accordingly, the antenna structure of the subject invention employs a planar forced air heat sink system including outer and inner heat sinks 76 and 86 which are embedded between electronic layers to dissipate heat generated by the heat sources included in the T/R cells, DC electrical components and the transceiver modules. Alternatively, the air channels 53₁, 53₂, and 87₁, 87₂, 87₃, and 87₄ included in the inner heat sink 86 and the waveguide manifold 52 could be filled with a thermally conductive filling to increase heat dissipation or could employ liquid cooling, if desired.

[0081] Having thus shown what is considered to be the preferred embodiment of the invention, it should be noted that the invention thus described may be varied in many ways. Such variations are not regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.