Patent Abstract:
An electrical connector apparatus and method for connecting circuit traces on two or more independent circuit board assemblies. A compressible elastomeric member is wrapped with a flexible circuit assembly having a plurality of independent circuit traces, with each circuit trace including a pair of raised electrical contacts. The compressible member with the electrical circuit wrapped over it is supported by a holder assembly. The holder assembly is secured to one of a pair of adjacently positioned independent printed circuit assemblies. The compressible member is held by the holder assembly so that it is compressed against both of the printed circuit board assemblies. The raised electrical contacts electrically contact traces on each of the printed circuit assemblies to complete the electrical connections between the circuit assemblies. The apparatus is especially useful in applications where a large plurality of electrical connections need to be made between independent circuit board assemblies in a very limited space.

Full Description:
STATEMENT OF GOVERNMENT RIGHTS 
   Certain of the subject matter of the present application was developed under Contract Number N00014-02-C-0068 awarded by the Office of Naval Research. The U.S. Government has certain rights in this invention. 

   CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application discloses subject matter that is generally related to U.S. Ser. No. 10/917,151 filed Aug. 12, 2004, presently pending, which claims priority from U.S. provisional application No. 60/532,156 filed on Dec. 23, 2003, the disclosures of which are incorporated herein by reference. The present application is also generally related to the subject matter of concurrently filed U.S. application Ser. No. 11/140758, entitled “Antenna Apparatus and Method”. 
   FIELD OF THE INVENTION 
   The present invention relates to electrical coupling assemblies, and more particularly to an electrical coupling assembly that is especially useful for electrically coupling two miniature, independent circuit board assemblies, for example two electrical component subassemblies used in a phased array antenna module. 
   BACKGROUND OF THE INVENTION 
   The Boeing Company (“Boeing”) has developed many high performance, low cost, compact phased array antenna modules. The antenna modules shown in  FIGS. 1   a - 1   c  have been used in many military and commercial phased array antennas from S-band to Q-band. These modules are described in U.S. Pat. No. 5,886,671 to Riemer et. al. and U.S. Pat. No. 5,276,455 to Fitzsimmons et. al., both of which are incorporated by reference into the present application. 
   The in-line first generation module has been used in a brick-style phased-array architecture at K-band and Q-band. The approach shown in  FIG. 1   a  requires elastomeric connectors for DC power, logic and RF distribution but it provides ample room for electronics. As implemented in  FIG. 1   a , the in-line module provides only a single beam, either linear or right-hand or left-hand circularly polarized. As Boeing phased array antenna module technology has matured, many efforts have resulted in reduced parts count, reduced complexity and reduced cost of several key components. Boeing has also enhanced the performance of the phased array antenna with multiple beams, wider instantaneous bandwidths and improved polarization flexibility. 
   The second generation module, shown in  FIG. 1   b , represents a significant improvement over the in-line module of  FIG. 1   a  in terms of performance, complexity and cost. It is sometimes referred to as the “can-and-spring” design. This design provides dual orthogonal polarizations in a more compact, lower-profile package than the in-line module. The can-and-spring module forms the basis for several dual simultaneous beam phased arrays used in tile-type antenna architectures from S-band to K-band. The fabrication cost of the can-and-spring module has been reduced through the use of chemical etching, metal forming and injection molding technology. The third generation module developed by Boeing, shown in  FIG. 1   c , provides a low-cost dual polarization receive module used in high-volume production at Ku-band. 
   Each of the phased-array antenna module architectures shown in  FIGS. 1   a - 1   c  require multiple module components and interconnects. In each module, a large number of vertical interconnects such as electrically conductive fuzz buttons and springs are used to provide compliant DC and RF connectivity between the distribution printed wiring board (PWB), ceramic chip carrier and antenna probes. 
   A further development directed to reducing the parts count and assembly complexity for single antenna modules is described by Navarro and Pietila in U.S. Pat. No. 6,580,402, assigned to Boeing. The subject matter of this application is also incorporated by reference into the present application and involves an “Antenna-integrated ceramic chip carrier” for phased array antenna systems, as shown in  FIG. 1   d . The antenna integrated ceramic chip carrier (AICC) module combines the antenna probes of the phased array module with the ceramic chip carrier that contains the module electronics into a single integrated ceramic component. The AICC module eliminates vertical interconnects between the ceramic chip carrier and antenna probes and takes advantage of the fine line accuracy and repeatability of multi-layer, co-fired ceramic technology. This metallization accuracy, multi-layer registration can produce a more repeatable, stable design over process variations. The use of mature ceramic technology also provides enhanced flexibility, layout and signal routing through the availability of stacked, blind and buried vias between internal layers, with no fundamental limit to the layer count in the ceramic stack-up of the module. The resulting AICC module has fewer independent components for assembly, improved dimensional precision and increased reliability. The in-line module, can-and-spring module, the molded module, and the AICC have been realized as single element modules. So far, the AICC has been implemented by Boeing as a single element phased array module which is connected to the printed wiring board and honeycomb in much the same way as the can-and-spring and injection-molded modules. The AICC approach provides manufacturing scalability from single to multiple elements. As manufacturing/assembly process yields increase, the AICC can be scaled from single to multiple element sub-arrays to reduce parts count and assembly complexity. 
   A Boeing antenna which departs from a single element module is described by Navarro, Pietila and Riemer in U.S. Pat. No. 6,424,313, also incorporated by reference into the present application, which is shown in  FIG. 1   e . This module is referred to within Boeing as the “3D flashcube”. It has been implemented as a four-element module to provide additional space for electronics. This approach also avoids the use of fuzz buttons and button holders for its vertical interconnects. It has been used successfully to provide two independent simultaneous receive beams at 21 GHz with +/−60° scanning. It has also been implemented at 31 GHz in a switchable transmit application with +/−60° scanning. The 3D flashcube model can also be used to implement more than two independent receive and/or transmit beams. 
   In  FIG. 1   f , Boeing-Phantom Works further combines DC power, logic and the RF radiating probes into a phased array antenna into a single component through an approach known as the “Antenna Integrated Printed Wiring Board” (“AIPWB”). This approach is disclosed in U.S. Pat. No. 6,670,930, owned by Boeing, which is also incorporated by reference into the present application. This approach reduces parts count and further improves alignment and mechanical tolerances during manufacturing and assembly. The improved alignment and manufacturing tolerances improves yield and electrical performance while the reduced parts count shortens assembly time and reduces the number of processing steps required to manufacture the antenna module. This ultimately lowers the overall phased array antenna system costs. The AIPWB approach can be scaled to larger sub-arrays without degrading performance and represents an important step in the direction of more easily and affordably manufactured phased array antenna systems. 
   The first generation module in  FIG. 1   a  is the standard single polarization in-line or brick architecture used extensively for many electronic phased array systems because of the ample room provided for electronics.  FIGS. 1   b ,  1   c  and  1   d  use a tile-type or planar architecture which naturally provides dual polarization. A drawback of the tile architecture is that space is severely limited as frequency and scanning angle increases, since the electronics and input/output pads must fit within the physical area of the radiators in the array lattice. Because of the additional input and output pads required to connect to the RF/DC power/logic distribution, single element modules are further constrained in dimensions. As the array dimensions increase, the single element module pads require tighter dimensional tolerances to ensure alignment and connectivity. 
   The antenna module of  FIG. 1   e  has some of the benefits of tile-type architectures, namely providing dual polarization and broad-side interconnections to the printed wiring board. It also has some of the benefits of the in-line architectures by providing ample area for electronics and transitions. The 3D flashcube concept has been realized as a quad-module but the approach can be increased to 2×N modules as yield in electronics and packaging increase. The 3D flashcube uses a three layer flexible stripline to provide connections from the electronics to the antennas as well as connections from the electronics to the printed wiring board. 
   However, even with the 3D flashcube implementation, it is difficult to provide the extremely tight antenna module spacing between adjacent antenna modules that is needed to achieve +/−60° scanning in the microwave frequency spectrum (e.g., 60 GHz). The limitation of using the three layer flexible stripline for interconnections is that as scan angles and frequencies increase, the stripline must be bent at very, very tight (i.e., small) bend radii in order to achieve the extremely close antenna module spacing required for +/−60° scan angle performance in the microwave frequency spectrum. The stripline ground plane and conductor line becomes more susceptible to breaking apart at the very small bend radii needed to accomplish this extremely tight radiating element spacing. 
   Accordingly, there still exists a need for a dual polarized, phased array antenna which is able to operate within the V-band frequency spectrum (generally between 40 GHz-75 GHz), and more preferably at 60 GHz, while preferably providing +/−60° (or better) grating-lobe free scanning. Such an antenna, however, requires a new packaging scheme for coupling the electronics of the antenna to the radiating elements in a manner to achieve the very tight radiating element spacing required for 60 GHz operation, while still providing adequate room for the electronics associated with each antenna module. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to an apparatus and method for forming an electrical connector assembly that is especially well suited for use in electrically coupling two or more small electrical circuit boards or subassemblies that are positioned in close proximity to one another. In one preferred implementation the present invention is used to electrically couple two small electrical subassemblies in a phased array antenna module. 
   In one preferred embodiment the connector apparatus comprises a flexible electrical circuit having at least one circuit trace with spaced apart first and second electrical contact portions. The flexible electrical circuit is secured over a compressible (i.e., elastomeric) substrate. In one form the compressible substrate has an elongated, cylindrical shape. A holder apparatus receives the compressible substrate with the flexible electrical circuit positioned over the substrate. The holder aligns and secures the compressible substrate against one of the printed circuit board assemblies such that the substrate is slightly compressed or deformed, thus causing the electrical contact portions on the circuit trace to be forced into contact, and held in contact, with circuit elements on each of the circuit board assemblies. The circuit trace and electrical contact portions thus form an electrically conductive path for coupling the electrical components of the two printed circuit board assemblies. 
   In one preferred form the holder assembly incorporates a plurality of alignment pins that engage with at least one of the printed circuit board assemblies. The alignment pins align the trace of the flexible electrical circuit with the electrical components on each of the printed circuit board assemblies. The alignment pins also hold the compressible substrate precisely positioned relative to the two printed circuit board assemblies. 
   The connector apparatus can be employed to make electrical connections between two or more printed circuit boards where the use of ribbon cables or point-to-point wiring would be impractical or impossible in view of the small size, the proximity, the spacing of the two printed circuit assemblies and/or the large number (i.e., density) of electrical connections that need to be made within a very small area. 
   Further areas of applicability of the present invention will become apparent from the following detailed description. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, in which: 
       FIG. 1   a  illustrates a simplified schematic representation of the elements of an in-line antenna module; 
       FIG. 1   b  illustrates a schematic representation of the elements of a can-and-spring antenna module; 
       FIG. 1   c  illustrates a schematic representation of a molded antenna module; 
       FIG. 1   d  illustrates a schematic representation of the elements used to construct an antenna integrated ceramic chip carrier module; 
       FIG. 1   e  is a simplified schematic view of the elements of a three dimensional flash cube quad-module antenna; 
       FIG. 1   f  is a perspective view of an antenna printed wiring board assembly in accordance with U.S. Pat. No. 6,670,930; 
       FIG. 2  is a perspective view of an antenna system in accordance with a preferred embodiment of the present invention; 
       FIG. 3  is a bottom perspective view of the antenna system of  FIG. 2  taken from the opposite side of the module, relative to  FIG. 2 ; 
       FIG. 4  is a bottom perspective view of the waveguide coupling element; 
       FIG. 5  is a cross sectional side view taken in accordance with section line  5 - 5  in  FIG. 2  illustrating the 1×2 waveguide splitter formed in the mandrel, with a pair of waveguide coupling elements secured to opposite sides of the mandrel; 
       FIG. 6  is a side cross sectional view of the mandrel and antenna module interconnection, taken in accordance with section line  6 - 6  in  FIG. 2 ; 
       FIG. 7  is a perspective view of an antenna system incorporating eight of the antenna modules shown in  FIG. 2 ; 
       FIG. 8  is a perspective view of the waveguide distribution network component used with the antenna system of  FIG. 7 ; 
       FIG. 9  is a bottom plan view of the waveguide distribution network component of  FIG. 8 ; 
       FIG. 10  is a perspective view of a 16 element antenna in accordance with an alternative preferred embodiment of the present invention;  FIG. 11  is an exploded perspective view of the components of the antenna module of  FIG. 10 ; 
       FIG. 11  is an exploded perspective view of the components of the antenna system of  FIG. 10 ; 
       FIG. 12  is an enlarged plan view of the aperture board of the antenna system; 
       FIG. 13  is an enlarged perspective view of the module core; 
       FIG. 14  is a cross sectional side view of the module core in accordance with section line  14 - 14  in  FIG. 13 ; 
       FIG. 15  is a perspective view of a front side of one of the chip carrier assemblies; 
       FIG. 15   a  is a perspective view of a rear surface of a cover that covers the waveguide backshort shown in  FIG. 15 ; 
       FIG. 16  is a perspective view of the rear side of the chip carrier assembly of  FIG. 15 ; 
       FIG. 16   a  is a perspective view of one of the molytabs used to support each MMIC chip set on a heat spreader panel; 
       FIG. 17  is a perspective view of the antenna module used to form the antenna system of  FIG. 10 ; 
       FIG. 18  is a bottom perspective view of the assembly shown in  FIG. 17 ; 
       FIG. 19  is a perspective view of the flexible connector assembly secured to the aperture board; 
       FIG. 20  is an exploded perspective view of the flexible connector assembly; 
       FIG. 21  is an assembled, perspective view of the flexible connector assembly; 
       FIG. 22  is a plan view of a flexible circuit that is used to form a portion of the flexible connector assembly; 
       FIG. 23  is an enlarged perspective view of a pair of traces of the flexible circuit of  FIG. 22 ; 
       FIG. 24  is a perspective view of an elastomeric member used with the flexible connector assembly; 
       FIG. 25  is an enlarged perspective view of one end of a portion of the flexible connector assembly; 
       FIG. 26  is a perspective view of a portion of the flexible connector assembly coupled to the aperture board and the chip carrier assemblies; 
       FIG. 27  is a cross sectional side view of the flexible connector assembly secured to the aperture board in accordance with section line  27 - 27  in  FIG. 10 ; 
       FIG. 28  is a cross sectional end view of the assembly taken in accordance with section line  28 - 28  in  FIG. 27 ; and 
       FIG. 29  is a perspective view of an antenna system incorporating a plurality of the chip carrier assemblies and module cores. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     FIGS. 2 and 3  illustrate a phased array antenna module  10 . The module  10  operates within the V-band spectrum, and more preferably at 60 GHz, with ±60° elevational scanning capability. The module  10  generally includes a core or mandrel  12 , a first electromagnetic wave energy distribution panel  14  secured to a first side  16  of the mandrel  12 , a second electromagnetic wave energy distribution panel  18  secured to a second opposing side  20  of the mandrel  12 , and a pair of subpluralities of antenna modules  22   a  and  22   b . The mandrel  12  includes an input  24  and a pair of spaced apart interconnects  26  for coupling to a printed circuit board (not shown). The interconnects  26  and the input  24  are formed at a first end  28  of the mandrel  12  and the modules  22   a  and  22   b  are disposed in openings  30   a  and  30   b , respectively, at a second end  32  of the mandrel  12 . The openings  30   a  and  30   b  are shown as hexagonal. Other shapes such as circular openings could readily be employed. The openings  30   a  and  30   b  receive the antenna components  22   a  and  22   b  in the desired orientation. 
   Components  22   a  and  22   b  may be AICC modules in accordance with the teachings of U.S. Pat. No. 6,580,402, the disclosure of which is incorporated by reference. It will be appreciated, however, that any other antenna component that provides the function of radiating electromagnetic wave energy could be implemented. 
   With further reference to  FIGS. 2 and 5 , the mandrel  12  includes an opening  34  formed on side  16  and an opening  36  formed on side  20  opposite the opening  34 . With specific reference to  FIG. 2 , a first waveguide coupling element  38  is secured over the opening  34  and a second waveguide coupling element  40  is secured over opening  36 . The two waveguide coupling elements  38  and  40  are identical in construction. The openings  34  and  36  are further in communication with the input port  24  and function to couple portions of the electromagnetic wave energy received through input port  24  with its associated distribution panel  14  or  18 . 
   Referring to  FIG. 4 , the waveguide coupling element  38  is shown in greater detail. Waveguide coupling element  38  is preferably formed from a single block of electrically conductive material, for example aluminum, and essentially forms a cover for covering the opening  34 . The element  38  includes a recessed area  38   a  having an angled surface  38   c  at one end of the recessed area and a centrally disposed rib that forms a projecting stepped waveguide transition surface  38   b  at the opposite end. One waveguide coupling element  38  is secured over each of openings  34  and  36 , such by gluing with a conductive compound, like an epoxy. 
   Referring now to  FIG. 5 , the mandrel  12  includes a 1×2 waveguide splitter  42  formed internally adjacent the openings  34  and  36 . The waveguide splitter  42  is longitudinally aligned with the input port  24  to receive the electromagnetic wave energy traveling through the input port  24  and to split the energy into approximately two equal portions. Approximately 50% of the electromagnetic wave energy is directed toward opening  34  and the other 50% toward opening  36 . A step  38   b   1  of stepped surface  38   b  contacts a circuit trace  14   a  on distribution panel  14  to transfer the electromagnetic wave energy channeled through opening  34  into the distribution panel. Angled surface  38   c  helps to channel electromagnetic wave energy received by the antenna system into the opening  34  during a receive phase of operation. During a transmit operation, openings  34  and  36  can be termed as “output” ports, while during a receive phase of operation they would form “input” ports, and input port  24  would instead function as an “output” port. 
   With further reference to  FIGS. 2 and 3 , printed circuit boards  44  and  46  couple the interconnects  26  with the distribution panel  14 . A similar pair of interconnects (not shown) is disposed on the second side  20  of the mandrel  12  and serves to couple the interconnects  26  with the distribution panel  18 . 
   Referring to  FIGS. 2 and 6 , each electronic module  48  in distribution panel  14  includes an application specific integrated circuit (ASIC)  50 , a power amplifier  52  and a phase shifter  54 . Each electronic module  48  is associated with a particular one of the antenna components  22   a  or  22   b . With specific reference to  FIG. 6 , an enlarged view of a portion of the distribution panel  14  illustrates the coupling of one electronic module  48  with one antenna component  22   a . A metallic wire or pin  56  extending from the antenna component  22   a  contacts the circuit trace  14   a  to make an electrical connection between the component  22   a  and the distribution panel  14 . The wire or pin  56  is preferably epoxied to the circuit trace  14   a  or otherwise fixedly secured to make an excellent electrical connection with the electronics module  48 . The wire or pin  56  also contacts one of radiating/reception elements (i.e., probes)  22   a   1  of the antenna component  22   a  to electrically couple the distribution panel  14  to the radiating/reception element  22   a , of the antenna component  22   a . Each antenna component  22   a  includes a pair of radiating/reception elements in the form of elements  22   a   1 , such as illustrated in  FIG. 2 . Independent pins or wires  56  are independently coupled to each radiating/reception element  22   a   1  and  22   a   2 . This form of electrical coupling avoids the bending limitations of a stripline conductor that heretofore has prevented the tight antenna module spacing required for +/−60° scanning in the gigahertz bandwidth, and thus allows electrical connections to be made to extremely tightly spaced antenna components. 
   The mandrel  12  is preferably formed from a single piece of metal, and more preferably from a single piece of aluminum or steel. The first end  28  further includes a plurality of openings  58  for allowing a plurality of antenna systems  10  to be ganged together to form a larger antenna system composed, for example, of hundreds of thousands of antenna components  22 . 
   With reference now to  FIG. 7 , an antenna system  100  incorporating eight antenna modules  10  is illustrated. The antenna system  100  includes a 1×8 waveguide distribution network  102  which is coupled to a DC power/logic distribution printed wiring board  104 . DC power/logic distribution printed wiring board  104  is in turn coupled to the first end  28  of each mandrel  12  of each antenna module  10 . The antenna system  100  thus forms a 128 element millimeter wave (i.e., V-band) phased array antenna system. An even greater plurality of antenna system  10  components can be coupled together to form a 128 element, 256 element, or larger 1×N (where “N” is 2 i  and “i” is an integer) phased array antenna system. Accordingly, it will be appreciated that antenna systems having varying numbers of radiating elements can be assembled using various numbers of the module  10  of the present invention. 
   Referring to  FIGS. 8 and 9 , the 1×8 waveguide distribution network  102  can be seen. Network  102 , in this example, functions to divide electromagnetic wave energy received through an input port  106  evenly between eight output ports  108 . Each output port  108  is longitudinally aligned with an associated input port  24  of the adjoining antenna modules  10  to allow a portion of the electromagnetic wave energy passing through the output port  108  to enter the input port  24  of each antenna module  10 . The printed wiring board  104  includes eight sections or areas which form conventional “pass throughs” (i.e., essentially waveguide structures) to enable the electromagnetic wave energy to pass from each of the outputs  108  through an associated pass through and into an associated input port  24  of one of the antenna modules  10 . Interconnects  26  ( FIG. 2 ) further electrically couple with portions of the DC power/logic board  104  on opposite sides of an associated one of the pass throughs so the DC power and logic signals can be provided to the distribution panels  14  and  18  of module  10 , and, accordingly throughout the entire phased array system. 
   Referring to  FIGS. 10 and 11 , an antenna system  200  is shown. Antenna system  200  incorporates a flexible connector assembly in accordance with a preferred embodiment of the present invention. 
   The antenna system  200  is illustrated as a sixteen RF element system, but the system  200  could be formed with a greater or lesser plurality of radiating elements. The antenna system  200  includes a conventional honeycomb plate  202 , typically referred to in the industry as simply a “honeycomb”, secured over an aperture board  204 . The honeycomb plate  202  is preferably made from metal, and more preferably from aluminum. The honeycomb plate  202  and the aperture board  204  are secured to a hollow, metallic support frame  206 . The support frame  206  is secured to a heat sink assembly  208 . Heat sink assembly  208  is secured to a waveguide adapter  210  on an undersurface  212  of the heat sink assembly  208 . The heat sink assembly  208  includes a fluid carrying conduit  214  located within a channel  216  of a metallic cold plate  218  for providing liquid flow through cooling to the heat sink assembly  208 . 
   With specific reference to  FIG. 11 , the honeycomb  202  includes a plurality of apertures  220  for receiving threaded fastening members  222 . Openings  202   a  form waveguides for electromagnetic wave energy passing to/from the aperture board  204 . Each opening  202   a  may be filled with a conventional dielectric plug, such as a plug made from REXOLITE® cross-linked, polystyrene, microwave plastic, or from ULTEM® polyetherimide thermoplastic. 
   Aperture board  204  likewise includes a plurality of apertures  224 , and the support frame  206  includes a plurality of blind threaded bores  226  opening from surface  206   a . The cold plate  218  includes a plurality of holes  228 . Fasteners  222  extend through apertures  220  and apertures  224  into threaded holes  226 . Fasteners  223  extend through apertures  228  of the cold plate  218  into four threaded blind holes  225  of the frame  206  that are co-linear with threaded holes  226  but on edge  206   b  of support frame  206 . The cold plate  218  also includes a waveguide opening  230 . Opening  230  is aligned with a bore  232  within the waveguide adapter  210  when the waveguide adapter  210  is secured via fasteners  234  to the undersurface  212  of the cold plate  218 . Aperture  232  has the same rectangular geometry as aperture  230  on a top end  210   a  of the adapter  210 . Also, aperture  230  has a constant cross section through the cold plate  218  while aperture  232  forms a tapered rectangular waveguide that changes height as it passes through adapter  210 . In this example, aperture  232  is designed to mate with a WR 19 standard waveguide on the bottom end  210   b  of the adapter  210 , while mating with aperture  230  on the top end  210   a . Aperture  230  may be called a custom, “reduced height” waveguide based on the standard WR 19 size. The purpose of adapter  210  is to transform the signal from a WR 19 waveguide to a reduced height, WR 19 waveguide. 
   Referring further to  FIG. 11 , within the support frame  206 , is housed a metallic module core or mandrel  240  that holds a module  242 . A flexible connector assembly  244  in accordance with a preferred embodiment of the present invention is also housed within the support frame  206 . The module  242  includes a pair of signal distribution panels in the form of chip carrier boards  246   a ,  246   b , and a pair of retainer clips  248   a ,  248   b . Chip carrier board  246   a  and retainer clip  248   a  form a first pair of components that are secured to one side of the core  240 , while chip carrier board  246   b  and retainer clip  248   b  form a second pair of components that are secured to the opposite side of the core  240 . The flexible connector assembly  244  is used to electrically couple the chip carrier boards  246  with the aperture board  204 . 
   Referring to  FIG. 12 , the aperture board  204  is shown in greater detail. The aperture board  204  is preferably formed in accordance with the teachings of U.S. Pat. No. 6,670,930. The aperture board  204  essentially forms a multi-layer printed wiring board that combines a plurality of dual-polarized, electromagnetic wave radiating/reception elements  250  (in this example 16 such elements) with DC power distribution and logic distribution functions. For convenience, elements  250  will simply be referred to throughout as “radiating” elements  250 . Radiating elements  250  are aligned with the openings  202   a  so that each opening  202   a  forms a waveguide for a respective one of the sixteen radiating elements  250 . The aperture board  204  enables DC power and logic signals to be applied to drive ASICs and monolithic microwave integrated circuits (MMICs) on each of the chip carrier boards  246   a ,  246   b . Each radiating element  250  includes a pair of RF elements (i.e., probes) to provide dual polarization transmit and receive capability to the antenna  200 . The aperture board  204  and the chip carrier boards  246   a ,  246   b  can be constructed to provide the antenna  200  with transmit and receive capabilities over a desired bandwidth, and in one specific implementation over a frequency bandwidth spanning at least between about 40 GHz-60 GHz. 
   Referring to  FIGS. 13 and 14 , the module core  240  includes a waveguide input port  252  and a pair of output ports  254  formed on opposite surfaces. The module core  240  may comprise aluminum or any other highly thermally conductive material, such as brass or molybdenum. The module core  240  may be formed from a single piece of material, or from several pieces of material bonded or otherwise secured together. With reference to  FIG. 14 , the module core  240  includes, in this embodiment, a 3 dB splitter  256  that divides the electromagnetic wave energy fed through input  252  evenly between the two output ports  254 . A channel  257  is formed at one end of the module core  240  for receiving a portion of the flexible connector assembly  244  when the module  242  is assembled. 
   As shown in  FIG. 18 , this module core  240  also includes a flange  258  to help secure the core to the cold plate  218  and to increase the contact surface area between module core  240  and the cold plate  208  to facilitate heat-transfer. Four blind holes  253   a  and  253   b  are tapped in the module core  240  adjacent the port  252 . Holes  253   a  are threaded and receive screws (not shown) that pass through holes  218   a  in the cold plate  218  ( FIG. 11 ) to fasten these components together. The remaining pair of holes  253   b  accept close fitting alignment pins  257  that also extend into holes  218   b  in the cold plate  218  in order to align waveguide port  252  in the module core  240  with waveguide opening  230  in the cold plate  218 . 
   Referring to  FIGS. 15 and 16 , one chip carrier board  246   a  is shown in greater detail. Each chip carrier board  246  comprises a low temperature, co-fired ceramic (LTCC) substrate  262  having in this case eight holes  264  and four recesses  266 . A waveguide backshort  268  is formed on a front side  270  of the LTCC substrate  262 . The waveguide backshort  268  functions to provide a transition from a waveguide (i.e., waveguide adaptor  210 ) to a TEM transmission line such as a microstrip. 
   Reference numeral  268   a  indicates an elongated, rectangular embedded waveguide coming to the surface of the ceramic chip carrier board  246   a , and forms part of the waveguide backshort  268  structure. Often waveguides are hollow cavities in metal structures, as in port  252 , but in this instance embedded waveguide  268   a  is a continuous part of the ceramic substrate of chip carrier board  246   a . Metal traces and vias are arranged in the ceramic substrate so that the region electrically acts as a waveguide even though there is no actual slot cut in the ceramic that forms board  246   a . The actual shorting part of the waveguide backshort  268  consists of a rectangular plate of metal  259  (preferably KOVAR™ super alloy or ALLOY  42  iron-nickel alloy  42 ) approximately 0.010 inch (0.254 mm) thick, of sufficient size to cover this waveguide backshort  268  opening. Referring to  FIG. 15   a , plate  259  is attached to the ceramic chip carrier board  246   a  with conductive epoxy to cover waveguide backshort  268 . The waveguide backshort plate  259  may itself contain a very short length of waveguide  259   a  on the order of 0.002 inches (0.0508 mm) long, corresponding to the size of the embedded waveguide  268   a  and contiguous with waveguide backshort  268 . Waveguide  259   a  forms a 0.002-inch-deep rectangular recess in one side of the waveguide backshort plate  259 . The purpose of this part is to terminate the waveguide  268   a  with a short (that is, cover it with a conductor). Doing so is necessary to facilitate transmission of RF energy from waveguide port  254  in the module core  240  to trace  280  ( FIG. 16 ) in the ceramic package  246   a . Adjusting the length of the waveguide  259   a  located in the waveguide backshort plate  259  tunes the transition so that efficiency of this transition is maximized. In some embodiments, the waveguide  259   a  in the backshort plate  259  may be filled with a thin piece of dielectric material such as ceramic or plastic to further tune the transition. 
   In  FIG. 16 , a rear surface  272  of the LTCC substrate  262  includes a metallic heat spreader panel  274  that is brazed or otherwise secured to the rear surface  272 . Panel  274  has a cutout  276  to avoid shorting an electrically conductive distribution network  278  formed on the rear surface  272  of the LTCC substrate  262 . The network  278  feeds microwave energy from a strip line transition portion  280  to various components on the chip carrier board  246   a . The microwave energy is that one-half portion of the input energy that flows through the port  254  ( FIG. 14 ) of the core  240  that the strip line transition portion  280  is positioned over when the module  10  is assembled. Input/output (I/O) portions  281  electrically couple the chip carrier board  246   a  with the aperture board  240 . The chip carrier boards  246  are bonded directly to the core  240  to form an excellent and direct (conductive) thermal coupling that facilitates cooling of the module  10 . This allows for highly efficient cooling of the electronic components on the chip carrier assemblies  246 . 
   With further reference to  FIGS. 15 and 16 , within each hole  264  is mounted a MMIC chip set  282 . Each MMIC chip set  282  consists of a power amplifier, a driver amplifier and a phase shifter MMIC. Each MMIC chip set  282  is supported on the heat spreader panel  274  and is electrically coupled to an associated radiating element  250  ( FIG. 12 ) via I/O lines  281 . An ASIC chip set  284  disposed within each recess  266  controls the phase shifter MMICs of an associated pair of MMIC chip sets  282 . In  FIG. 15 , each ASIC chip set  284  controls the phase shifter MMICs of the two MMIC chip sets  282  located immediately above it. The distribution network  278  in  FIG. 16  divides electromagnetic wave energy input to the strip line transition portion  280  evenly to each of the MMIC chip sets  282  so that each radiating element  250  receives 1/16 of the total energy input at port  252 . 
   The metallic heat spreader panel  274  is a thermally conductive metal plate preferably about 0.015 (0.381 mm) inch thick, composed of any material with a coefficient of thermal expansion similar to the ceramic substrate  262 , for example molybdenum, copper-tungsten, or copper-moly-copper laminate. The panel  274  has several purposes. Since holes  264  penetrate through the entire ceramic substrate, each hole  264  must have a floor on which MMIC chip set  282  may be directly or indirectly mounted. The heat spreader panel  274  covers the holes  264  and provides a surface on which the MMIC chip sets  282  may be subsequently mounted from the opposite side of the chip carrier board  246   a . Also, integrated circuit components may be indirectly mounted to the heat spreader panel  274  via a molytab  261 , as shown in  FIG. 16   a . A small block of molybdenum (i.e., molytab  261 ) is affixed to the heat spreader panel  274  by means of conductive epoxy. The MMIC chip sets  282  are then mounted to the molytab  261  with conductive epoxy. The purpose of the molytab  261  is to make the top surface of each of the MMIC chip sets  282  coplanar with the top surface of the ceramic chip carrier board  246   a  and to provide a direct thermal path from the chip sets  282  to the heat spreader panel  274 . The heat spreader panel  274  further provides a direct heat path from the molytab  261  to the module core  240 , with the module core  240  being in metal-to-metal contact with the cold plate  218 . Therefore a continuous heat transfer path is formed from the back of each chip set  282  to the cold plate  218 . The metals used have a high thermal conductivity, limiting MMIC chip set  282  operating temperature and providing for extended MMIC chip set life. If the MMIC chip sets  282  were mounted directly to the ceramic substrate without the use of a molytab and heat spreader panel  274 , the MMIC chip set operating temperature would likely be somewhat higher than it is with the present embodiment. Mounting the MMIC chip sets  282  to an all-metallic structure also reduces the probability that the chip sets will experience a feedback condition, commonly called oscillation, that causes MMIC amplifiers to output large amounts energy at undesired frequencies. 
   Referring to  FIGS. 17 and 18 , the chip carrier assembly  242  is shown assembled to the core  240 . Each retainer clip  248  is preferably made from stainless steel tempered to a spring condition and includes a pair of curved arms  286  that interlock with one another. The arms  286  are secured from separating by pins  288  ( FIG. 18 ) that are inserted into each pair of interlocked arms  286 . 
   In  FIG. 19  the flexible connector assembly  244  is shown coupled to an undersurface  205  of the aperture board  204 . The assembly  244  is used to electrically interconnect the I/O lines  281  of each chip carrier board  246  with circuit traces, indicated in highly simplified form by reference numeral  204   b , on the aperture board  204 . This enables electrical communication between the radiating elements  250  and the chip carrier boards  246 . 
   Referring to  FIGS. 20 and 21 , the flexible connector assembly  244  includes a flexible circuit assembly  290  which is wrapped over an elongated, cylindrical compressible (i.e. elastomeric) member  292  to form a compressible electrical coupling subassembly  294 . The compressible subassembly  294  is supported on a holder subassembly  296 . The holder subassembly  296  includes a frame  298  having sleeves  300  formed at opposite ends. The frame  298  further has bores  302  to receive alignment pins  304   a ,  304   b . Each sleeve  300  has a bore  301  that receives a threaded fastener  306  to secure the holder assembly  296  to the aperture board  204 . The frame  298  may be made from any suitably rigid material such as metal or plastic. Referring briefly to  FIG. 19 , the aperture board  204  includes threaded blind holes  204   a  that receive the threaded fasteners  306 . 
   With specific reference to  FIG. 22 , the flexible electrical circuit  290  is illustrated before the circuit has been secured to the compressible member  292 . The flexible electrical circuit  290  includes a plurality of holes  308   a  and  308   b  adjacent the four corners of the circuit  290 . Holes  308   a  overlay one another, and holes  308   b  similarly overlay one another, when the circuit  290  is wrapped over the compressible member  292 . Hole  308   c  is longitudinally aligned with the holes  308   a  when the flexible circuit  290  is rolled over the compressible member  292 . Similarly, hole  308   d  is longitudinally aligned with holes  308   b  when the flexible circuit  290  is rolled and secured over the compressible member  292 . 
   The flexible circuit  290  includes a first plurality of circuit traces  310  formed in a longitudinal line, and a second plurality of circuit traces  312  also formed in a longitudinal line adjacent the first plurality of circuit traces  310 . The traces  310  and  312  are preferably formed on a sheet of polyimide having a thickness in the range of preferably about 0.0005 inch to 0.002 inch (0.0127 mm-0.0508 mm), excluding the thickness of the circuit traces  310  and  312  (typically copper having a thickness of between 0.0035 inch-0.0007 inch; 0.089 mm-0.018 mm). The above-described thickness range, as well as the width of each of the traces  310  and  312 , will need to be considered together to achieve the desired impedance (in the present embodiment about 50 ohms). While only two rows of circuit traces  310  and  312  are shown, a greater or lesser plurality of rows of circuit traces could be used to feed power at the desired impedance. Circuit traces  310  each include a pair of raised electrical contacts or pads  314   a  and  314   b , while traces  312  similarly include raised electrical contacts or pads  316   a  and  316   b . With brief reference to  FIG. 23 , the raised electrical contacts  314   a  and  314   b  of one of the circuit traces  310  are illustrated in enlarged fashion. 
   With reference to  FIG. 24 , the compressible member  292  is shown in greater detail. The compressible member  292  may be formed from any resilient, (i.e., elastomeric) deformable material, but in one preferred form comprises a silicone rubber cord of generally circular cross section with a Shore A durometer rating of approximately 60. Such material is manufactured by Parker Seal Co. of Lexington, Ky. The compressible member  292  includes a pair of bores  318   a  and  318   b  that are formed with a spacing in accordance with the spacing separating holes  308   c  and  308   d  of the flexible electrical circuit  290 . The diameter of the compressible member  292  may vary to suit the needs of a specific application, but in one preferred form comprises a diameter of between about 1.025-1.055 inch (2.6-2.67 mm). Similarly, the overall length may vary to accommodate electrically coupling to various pluralities of circuit traces on the aperture board  204 . Furthermore, the compressible member  292  may take other shapes besides a cylindrical shape. Spherical compressible members, oval shaped members or other shapes could be employed to suit the needs of specific applications, provided the flexible circuit assembly  290  can still be wrapped over the compressible member. 
   Referring to  FIG. 25 , the flexible circuit assembly  290  is shown wrapped over the compressible member  292 . Preferably, the flexible electrical circuit  290  has an overall width that does not leave any overlaps. Hole  318   b  aligns with holes  308   a ,  308   c  while hole  318   a  aligns with openings  308   b ,  308   d . Adhesive can be used to secure the flexible electrical circuit  290  to the compressible member  292 , but may not be required. Pins  304   a  and  304   b  lock the flexible electrical circuit  290  into place by passing through all the holes  308 . 
   Referring to  FIG. 27 , a highly enlarged, cross sectional side view in accordance with section lines  27 - 27  of  FIG. 10  illustrates the compressible subassembly  294  in electrical contact with just the aperture board  204 . A portion of the assembly  244  resides with the channel  257  in the module core  240 . 
     FIG. 28  is an enlarged, end, cross-sectional view of the flexible connector assembly  244  in accordance with section line  28 - 28  in  FIG. 27 , with the assembly  244  coupled to the aperture board  204  and the chip carrier boards  246   a  and  246   b . The circuit traces  310  and  312  are shown in representative form making electrical contact with the chip carrier boards  246   a ,  246   b . The aperture board  204  includes traces  240   b   1 , and  240   b   2 , also shown in highly simplified, representative form. Chip carrier board  246   a  includes a circuit trace  324  and board  246   b  includes at least one trace  326 , where traces  324  and  326  are shown in simplified, representative form. The raised electrical contact pads  314   a  and  314   b  of trace  310  can be seen pressed into contact with the electrical traces  240   b   2  and  326 . Raised electrical contact pads  316   a ,  316   b  of circuit trace  312  are pressed into electrical contact with circuit traces  240   b   1  and  324 . The alignment pins  304   a  and  304   b , in combination with the precisely located blind holes  204   b  ( FIG. 25 ), provide highly accurate alignment of the raised electrical contact pads  314   a ,  314   b  and  316   a ,  316   b  relative to the electrical traces that they contact. 
   The precise dimensions of the raised contact pads  314 , as well as the spacing between the circuit traces  310  and  312 , can be tailored to accommodate a degree of misalignment of the raised contacts  314 ,  316 . In one preferred form the raised contacts  314 ,  316  are formed in accordance with GoldDot™ flexible circuit technology available from Delphi Connection Systems of Irvine, Calif. The raised contacts  314 ,  316 , in one exemplary form, have a base diameter of about 0.007 inch (0.18 mm) and a height of about 0.0035 inches (0.089 mm). Raised contacts could also be formed by drilling vias in the contact locations and barrel plating the vias in such a way that barrel of the via extends beyond the surface of the flexible electrical circuit  290  forming a raised contact. Alternately metallic bumps could be soldered or compression bonded onto the flexible electrical circuit  290 . 
   Referring to  FIG. 29 , a 256 element antenna aperture  300  incorporating sixteen of the modules  240  is illustrated. In a ganged embodiment, a suitably dimensioned honeycomb  302  having a plurality of 256 apertures (not visible) is disposed against an aperture board  304 . Aperture board  304  includes 256 antenna components (not visible) that interface with the sixteen modules  240 . Thus, apertures having 2 n  (n being an integer) elements could be constructed to suit the needs of a wide range of applications. The systems  10  and  200  are ideally suited for phased array antenna applications where a large number (e.g., dozens, hundreds or thousands) of antenna electronics components must be coupled to a correspondingly large plurality of electromagnetic radiating elements in a relatively small area. 
   The antenna systems  10  and  200  that use distribution panels  14  and  18 , and chip carrier assembly  242 , provide ample room for the electronics required for a phased array antenna and enable the extremely tight radiating element spacing required for operation at V-band frequencies. The antenna systems  10  and  200  thus combine the advantages of previous “tile” type antenna architectures with those of the “brick” type architectures. The antenna systems  10  and  200  further include a module component that combines the use of a stripline waveguide with an air-filled waveguide to provide an antenna system with acceptable loss characteristics that still is able to distribute electromagnetic wave energy to a large plurality of tightly spaced radiating elements. This enables easy, modular expansion to create a larger overall antenna system. Additionally, the antenna systems  10  and  200  are readily suited for use with conventional waveguide distribution network components (e.g., a corporate waveguide component), thus making them especially well suited for use in larger (e.g., 128 element, 256 element, etc.) antenna systems. The system  200  is especially well suited to dissipating thermal energy generated by the chip carrier boards  246 . 
   The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Technology Classification (CPC): 7