Injection-molded phased array antenna system

An injection molded phased array antenna system such as may advantageously employed on satellites. The antenna system comprises a plurality of metal plated, injection molded plastic horn radiating elements respectively coupled to a plurality of metal plated, injection molded plastic orthomode junctions that produce a corresponding plurality of vertically and horizontally polarized outputs. A metal plated, injection molded plastic vertical and horizontal beamforming networks is coupled to outputs of the plurality of orthomode junctions that establish unique phases and amplitudes that produce two separate outputs associated with two independent beams. The beamforming networks each comprise a plurality of metal plated, injection molded plastic fixed phase shifters respectively coupled to outputs of the plurality of orthomode junctions, a plurality of metal plated, injection molded plastic two-way power combiner-divider networks coupled to adjacent ones of the phase shifters, a plurality of metal plated, injection molded plastic eight-way power combiner-divider networks coupled to the two-way power combiner-divider networks by way of an intermediate structural panel, and a plurality of metal plated, injection molded plastic four-way power combiner-divider networks coupled to the eight-way power combiners by way of a main structural panel. The four-way power combiner-divider networks produce respective vertical and horizontal polarized outputs of the antenna system.

BACKGROUND
 The present invention relates generally to satellites, and more
 particularly, to a low cost, injection molded phased array antenna system
 that may advantageously be used on satellites.
 In addition to lower costs and shorter delivery schedules, the current
 trend in synchronous orbit satellites and satellite antennas is to provide
 more power and more payload capability, including more independent antenna
 beams. Satellite antennas while meeting other requirements must be low
 cost, quickly produced and mount to available spacecraft mounting
 locations. Also, the spacecraft with antennas and solar arrays must fit
 within the shroud of the launch vehicle. Spacecraft mounting space and
 shroud volume are limited, and larger launch vehicles with larger shrouds
 are costly.
 Transmit and receive functions are often separated into two antennas, each
 covering a narrow bandwidth, resulting in a reduction in transmit feed
 system losses and an improvement in antenna beam shape optimization
 efficiency. Improved transmit antenna performance reduces the high costs
 associated with supplying more solar array DC power, traveling wave tube
 amplifier (TWTA) RF power, and thermal control.
 A deployed shaped-reflector antenna is frequently used to satisfy transmit
 requirements and an earth facing, deck-mounted reflector antenna is used
 to satisfy receive functions. An earth deck structure is necessary to hold
 the receive antenna reflector, subreflector and RF feed. At Ku-band, the
 projected aperture of the earth deck antenna diameter is typically 1.2
 meters. The reflector, subreflector and structure are made of graphite
 composite materials.
 It would therefore be advantageous to have an improved phased array antenna
 system which may be used on satellites that improves upon conventional
 antennas.
 SUMMARY OF THE INVENTION
 The present invention provides for an injection molded phased array antenna
 system that may advantageously be used on satellites. The phased array
 antenna system comprises a plurality of metal plated, injection molded
 plastic waveguide components. A reduced-to-practice embodiment of the
 phased array antenna system includes five injection molded plastic
 components, some of which require no secondary machining, while some
 require minimal secondary machining.
 More particularly, the phased array antenna system comprises a plurality of
 metal plated, injected-molded radiation elements that include a plurality
 of metal plated, injected-molded horn radiating elements. A plurality of
 metal plated, injected-molded orthomode junctions are respectively coupled
 to the horn radiating elements. A crossed septum is preferably disposed in
 the radiating aperture of each horn radiating elements that equalizes E
 and H-plane radiation and increases radiating element gain. A
 noncontacting through port septum and a side port septum are disposed in
 each of the orthomode junctions. 90 degree E- and H-plane waveguides are
 coupled to appropriate side ports of the orthomode junctions. Vertical and
 horizontal metal plated, injected-molded phase shifters are coupled to
 each of the plurality of orthomode junctions.
 A metal plated, injected-molded power combiner-divider network comprising a
 plurality of cascaded vertical polarization and horizontal polarization
 power combiner-divider elements is coupled to outputs of the phase
 shifters and to outputs of the 90 degree E- and H-plane waveguides. Each
 power combiner-divider network is split along the broadwall of the
 waveguide and is riveted together. This method of constructing the power
 combiner-divider networks makes them relatively insensitive to
 perturbations. The broadwall split block technique used to produce the
 power combiner-divider networks allow accurate injection molding without
 electrical performance degradation.
 A plurality of subassemblies are produced that comprise a pair of horns and
 orthomode junctions, a pair of two-way power combiners and four phase
 shifters interconnected using spring clips are coupled to a plurality of
 eight-way power combiner-divider networks and are secured together using
 an intermediate structural panel. The assembled plurality of subassemblies
 are coupled to sets of four-way power combiner-divider networks for each
 polarization and secured together using a main structural panel. Each set
 of four-way power combiner-divider networks respectively produces vertical
 and horizontal polarized outputs of the antenna system.
 Near net dimensional, injection molding is used to reduce the required
 machining of the various components to a minimum. The phased array antenna
 system uses waveguide slip joints, snap together features, and clips for
 ease of assembly. The phased array antenna system has lighter weight, is
 produced at lower cost, with quicker fabrication and assembly, than
 conventional comparably performing antennas.
 The use of the injected-molded components produces a densely packed package
 that is a physically small array. The use of the injected-molded
 components reduces or shortens lengths of waveguide runs and therefore
 reduces the insertion loss of the phased array antenna system. The slip
 joints allow components to slide or snap together. This eliminates
 fasteners and is less sensitive to alignment, and allows the use of clips
 for ease of assembly.

DETAILED DESCRIPTION
 Referring to the drawing figures, FIG. 1 illustrates a system block diagram
 of an exemplary passive array antenna system 10 in accordance with the
 principles of the present invention. The passive array antenna system 10
 illustrated in FIG. 1 has been reduced-to-practice and a perspective view
 of a fully assembled system 10 is shown in FIG. 2. The reduced-to-practice
 embodiment of the passive array antenna system 10 comprises a 256 element
 passive direct radiating receive array operating from 13.75 GHz to 14.5
 GHz with a two wavelength element spacing. The system 10 has the
 equivalent RF performance of a conventional 1.2 meter Gregorian dual
 polarized shaped reflector antenna.
 The exemplary passive array antenna system 10 comprises 256 horn radiating
 elements 11, or horns 11. Each of the 256 horn radiating elements 11 is
 integrated with an orthomode junction 12 that produces 256 vertically and
 256 horizontally polarized outputs. Each of the horn radiating elements 11
 also contains a crossed septum 13 in its aperture to increase the
 directivity and improve E-plane and H-plane equalization.
 Separate beamforming networks 14 for each (vertical and horizontal)
 polarization are used to establish the unique phase and amplitudes
 necessary to produce two separate outputs associated with two independent
 beams of any desired shape. Due to the substantial similarity of the
 vertically and horizontally polarized beamforming networks 14, only the
 horizontally polarized beamforming network 14 will be described.
 The horizontally polarized output produced by each horn 11 and orthomode
 junction 12 passes through a predetermined fixed phase shifter 15 and is
 combined with the horizontally polarized output produced by a neighboring
 horn 11, orthomode junction 12 and phase shifter 15 in one of 128, two-way
 power combiner-divider networks 16. The 128 outputs of the two-way power
 combiner-divider networks 16 are then combined by sixteen eight-way power
 combiner-divider networks 17, resulting in sixteen outputs that are
 combined by five four-way power combiner-divider networks 18 to produce a
 single, horizontally polarized output.
 Each eight-way power combiner-divider network 17 is comprised of four
 two-way power combiner-divider networks 16, and each four-way power
 combiner-divider network 18 is comprised of two two-way power
 combiner-divider networks 16, for a total of 255 two-way power
 combiner-divider networks 16 in each vertically and horizontally polarized
 beamforming network 14. Each two-way power combiner-divider network 16 has
 a predetermined, fixed, output power ratio which along with the phase
 shifters 15 uniquely determine any desired output beam shape.
 In the antennas system 10, the RF beamforming networks 14 are designed to
 yield a "generic" part when they are injection molded. Each "generic"
 molded beamforming network 14 become "unique" after a desired power
 division ratio is computer numerically controlled (CNC) machined into each
 hybrid ring power combiner-divider network 16, 17, 18. By molding "near
 net shape" parts, the economy of using high volume, low cost manufacturing
 methods (i.e., injection molding and CNC machining) is realized. Secondary
 machining operations are minimal, but allow great design flexibility for
 specific antenna applications and all RF components. Net shape phase
 shifters 15 can be quickly and easily "snapped" in place to change or set
 desired characteristics.
 Table 1 presents a calculated loss budget and edge-of-coverage (EOC) gain
 for an exemplary reduced-to-practice antenna system 10 (shown in FIG. 2)
 designed to produce typical contiguous United States (CONUS) coverage. The
 beamforming network 14 of the reduced-to-practice antenna system 10 was
 constructed in WR62 and half weight WR62 waveguide operating in the
 TE.sub.11 mode and uses U-shaped waveguide phase shifters 15 and
 internally terminated hybrid ring power combiner-divider networks 16, 17,
 18. The RF performance of each component was computer optimized and then
 verified with aluminum models. An aperture cover 21 (FIG. 5) used in the
 reduced-to-practice antenna system 10 may be replaced by a three-layer
 meanderline polarizer 21b (FIG. 5) with an added 0.1 dB of loss if
 circular polarization is desired.
 TABLE 1
 Edge of coverage gain
 CONUS coverage edge of coverage directivity
 Rectangular horn 31.0 dB
 Crossed septum 0.5 dB
 Total directivity 31.5 dB
 Array antenna losses
 Mismatch loss 0.2
 Insertion loss 0.4
 Aperture cover loss 0.1
 total loss 0.7
 Antenna EOC gain 30.8
 The mechanical and manufacturing design of the passive array antenna system
 10 will now be discussed. To significantly lower the cost of the finished
 system 10, metallized, injection-molded fiber reinforced thermoplastic
 waveguide components are used for the horn radiating elements 11, phase
 shifters 15 and power combiner-divider networks 16, 17, 18. The material
 used in the reduced-to-practice embodiment of the passive array antennas
 system 10 has excellent physical and thermal properties, produces highly
 repeatable components, and is lightweight and easy to machine.
 Good metallization along with straightforward injection molding, is assured
 by splitting the power combiner-divider networks 16, 17, 18 along the
 waveguide broadwall axis exposing their inside surfaces. The power
 combiner-divider networks 16, 17, 18 are designed and molded to near net
 shape and are then lightly machined in "ring" areas 28 to predetermined
 fixed power ratios using high speed CNC machining. Internal RF loads 26
 (FIGS. 6a, 6b) for the power combiner-divider networks 16, 17, 18 are
 molded to net shape and hold-in-place features allow them to be captured
 when installed in the power combiner-divider networks 16, 17, 18.
 Injection molding to net and near net shape allows all components to be
 produced in quantity for a relatively low cost and placed in inventory in
 advance of their need, thus reducing the delivery time for a finished
 antenna array system 10.
 Ease of assembly, integration and test has been considered in the design of
 the passive array antenna system 10. Along with minimizing parts count
 where possible, flanges are eliminated, waveguide slip-joints 33 (FIG. 3,)
 are used, and threaded fasteners are replaced by clips 23 (FIG. 3) and
 lock-in place features 24. Where threaded fasteners are required,
 light-weight composite versions are used. Excess material has been
 designed out of the injection-molded pieces and interlocking, self-jigging
 features have been used.
 The injection-molding tools used to make the components were constructed
 from three-dimensional computer-aided-design (CAD) file models of the
 injection-molded components. The CAD files were verified using
 stereo-lithography models.
 FIG. 2 illustrates a perspective view of a fully-assembled passive array
 antenna system 10 with its aperture cover 21 and aperture cover support
 panels 21a removed on two sides for clarity. The fully-assembled
 reduced-to-practice system 10 is 0.84 meters by 0.76 meters in
 cross-section and 0.37 meters in height and weighs 28.7 Kg.
 FIG. 3 illustrates a partially exploded perspective view of an assembly 30
 comprising a pair of horns 11 and orthomode junctions 12, a pair of
 two-way power combiner-divider networks 16 and four phase shifters 15
 interconnected using Beryllium copper spring clips 23. This assembly 30 is
 a simple building block, and, when repeated a predetermined number of
 times, forms a major portion of the antenna system 10.
 FIG. 3a is a front perspective view of a portion of the assembly 30 shown
 in FIG. 3. The orthomode junctions 12 are coupled to ports 31 of the
 two-way power combiner-divider networks 16 by way of sections of straight
 waveguide 32 comprising the through ports 34 that have male waveguide slip
 joints 33a at their ends. The side ports 37 of the orthomode junctions 12
 are coupled to ports 31 of the two-way power combiner-divider networks 16
 by way of 90 degree E- and H-plane waveguides 35. The 90 degree E- and
 H-plane waveguides 35 also have male waveguide slip joints 33a at their
 ends. The male waveguide slip joints 33a connect to female slip joints 33b
 at the inputs of the two-way power combiner-divider networks 16.
 FIG. 3a illustrates the interior of the horn 11 and shows the cross septum
 13 disposed in the aperture of the horn. A noncontacting through port
 septum 34a is disposed at the junction of the horn 11 and a through port
 34 of the orthomode junction 12. FIG. 3a also shows a side port septum 37a
 formed in the sidewall at a side port 37 of the orthomode junction 12.
 FIGS. 3 and 3a more clearly show the alignment features 24 used on the
 horns 11, orthomode junctions 12, the straight waveguides 32, and the 90
 degree E- and H-plane waveguides 35.
 The phase shifters 15 are set to predetermined values between 0.degree. to
 360.degree. by CNC machining material from their open ends to produce the
 proper length and are easily interchanged to produce a desired phase
 distribution. Each horn 11 and orthomode junction 12 are each injection
 molded in two pieces and the cross septum 13 is injection molded in one
 piece. The five pieces comprising the horn 11 and orthomode junction 12
 are bonded together with structural adhesive and then plated with
 electroless copper to produce a finished subassembly.
 The 90 degree E- and H-plane waveguides 35 are injection molded in two
 pieces in two pieces that are bonded together with structural adhesive and
 then plated with electroless copper to produce a finished subassembly. The
 assembled 90 degree E- and H-plane waveguides 35 are bonded to the side
 port of the 37 of the orthomode junction 12.
 The phase shifters 15 and all versions of the power combiner-divider
 networks 16, 17, 18 are each molded in two pieces. After machining,
 electroless plating, and insertion of RF loads 26 in the power
 combiner-divider networks 16, 17, 18, the two pieces are joined together
 using molded-in self-aligning features and mechanically fastened with
 rivets 32 (FIGS. 6a, 6b, 7) disposed through tabs of the components.
 FIG. 4 illustrates a 4.times.16 element subarray assembly 30 formed by
 fastening thirty-two assemblies 30 comprising two horns 11, two orthomode
 junctions 12, four phase shifters 15 and two two-way power
 combiner-divider networks 16 to an intermediate structural panel 36.
 Outputs of the two-way power combiner-divider networks 16 pass through the
 intermediate structural panel 36 and slip into input ports 41 of four
 horizontally polarized and four vertically polarized eight-way power
 combiner-divider networks 17. The eight-way power combiner-divider
 networks 17 are fastened to the underside of the structural panel 36 and
 are offset with respect to each other for proper waveguide alignment.
 Details of the eight-way power combiner-divider networks 17 are shown and
 described with reference to FIGS. 6a and 6b.
 FIG. 5 illustrates an exploded view of the passive array antenna system 10.
 Four 4.times.16 element subarray assemblies 30 (FIG. 4) are fastened to a
 main structural panel 42. Two output power combiner/divider networks 19
 are fastened to the underside of the structural panel 42. For clarity,
 only one of two output combiner-divider networks 19, which are a subset of
 five two-way power combiner-divider networks 18, is shown. The second
 output combiner-divider network 19 is offset from and passes through the
 one that is shown in FIG. 5.
 Sixteen interconnecting waveguide input ports 43 pass through the
 structural panel 42 and slip into eight horizontally polarized and eight
 vertically polarized output ports 44 (FIG. 4) of the eight-way power
 combiner-divider networks 17. On the underside of the middle pair of the
 four-way power combiner-divider networks 18, are one horizontally
 polarized and one vertically polarized output ports (not shown). Fastening
 the aperture cover 21 and side panels 21a to the support panel 42
 completes the passive array antenna system 10. The aperture cover 21 may
 be replaced by a three-layer meanderline polarizer 21b with an added 0.1
 dB of loss if circular polarization is desired.
 FIGS. 6a, 6b, 7, 8 and 9 illustrate details of the power combiner-divider
 networks 16, 17, 18 used in the antenna system 10. More particularly,
 FIGS. 6a and 6b illustrate details of exemplary embodiment of the
 eight-way power combiner-divider networks 17 employed in the antenna array
 system 10 of FIG. 1. FIG. 6a shows a fully-assembled pair of the eight-way
 power combiner-divider network 17. FIG. 6b shows an exploded view of the
 horizontal eight-way power combiner-divider network 17 with an assembled
 vertical eight-way power combiner-divider network 17 disposed below it.
 FIG. 7 illustrates a partially exploded view of a typical near-net
 four-way power combiner-divider network 18. FIG. 8 illustrates an
 isometric view of two fully-assembled nested four-way power
 combiner-divider networks 18. FIG. 9 is an exploded view of a two-way
 power combiner-divider network 16.
 Each eight-way power combiner-divider network 17 is molded in two halves
 17a, 17b to near net shape and divided along its broadwall axis. Light
 machining is required in hybrid ring areas 28 of the respective hybrid
 ring power combiner-divider networks 17 to produce predetermined, fixed,
 output power ratio. After machining, both halves 17a, 17b are plated with
 electroless copper. RF loads 26 are molded to net shape including self
 capture features 48 and are inserted into the bottom half each the
 eight-way power combiner-divider network 17. The two halves 17a, 17b are
 joined using molded-in alignment features 24 and held in place with
 mechanical rivets 32. Copper grounding clips 46 are installed to ensure
 good electrical connection to the other components in the completed system
 10. With the exception of the grounding clips 46, the two-way and four-way
 power combiner-divider networks 16, 18 are similarly designed, produced,
 plated and assembled.
 Similarly, Each two- and four-way power combiner-divider network 16, 18 is
 molded in two halves 16a, 16b , 18a, 18b to near net shape and divided
 along its broadwall axis. Light machining is required in hybrid ring areas
 28 of the respective hybrid ring power combiner-divider networks 16, 18 to
 produce predetermined, fixed, output power ratio. After machining, the
 respective halves 16a, 16b, 18a, 18b are plated with electroless copper.
 RF loads 26 are molded to net shape including and are inserted into the
 bottom half each the power combiner-divider network 16, 18. The respective
 halves 16a, 16b, 18a, 18b are joined using molded-in alignment features 24
 and held in place with mechanical rivets 32. Copper grounding clips 46 are
 installed.
 As is shown in FIG. 9, the phase shifters 15 are sections of U-shaped
 plastic waveguide whose waveguide length is fixed. The phase shifters 15
 are set to predetermined values between 0.degree. and 360.degree. by
 machining material from their open (flat) ends to produce the proper
 length. The ring area 28 of the two-way power combiner-divider network 16
 that are lightly machined to predetermined fixed power ratios is more
 clearly shown in FIG. 9.
 From the above, it should be understood that the present invention provides
 a novel method for producing very low cost and lightweight phased array
 satellite antennas systems 10 using injection moldable, lightweight
 thermoplastic composite materials. The antenna system 10 comprises an
 assembly of microwave components that are injection molded to "net" and
 "near net" shape that are subsequently plated and assembled, or bonded,
 plated and assembled to form RF antenna components. These components have
 all of the required internal physical features molded to final proportions
 such as proper waveguide height and width dimensions, tuning stubs,
 septum, transformation sections, coupling slots, filter cavities, and the
 like, to effect the desired RF performance.
 With reference to FIG. 3, in the case of the horn and orthomode junction
 assembly, the two RF components (tapered horn 11 and orthogonal mode
 transformer or junction 12) are integrated into one unit, minimizing
 unnecessary, heavy and expensive flanges and hardware. The horn and
 orthomode junction assembly includes four molded plastic parts that are
 easily assembled using unique internal alignment and fixturing features
 molded into the parts.
 The horn and orthomode junction assembly is molded in two halves 11a, 11b
 (FIG. 3) that has a precision molded joint in the mating surfaces designed
 to support an adhesive structural bond, joining the halves 11a, 11b
 together. One half 11a has a continuous raised triangular cross section
 along the perimeter of the part. On the mating piece, a corresponding
 triangular shaped grove is molded. During assembly, adhesive is applied to
 the grooved surface. A flat spatula is used to screed the adhesive in the
 groove leaving the exact volume of bonding material. The dimensions of the
 mating ridge and the groove are such that when assembled the exact volume
 of adhesive is squeezed into the bond joint producing the desired bond
 line thickness without excess squeeze-out of the adhesive. The dimensions
 of the mating features, when assembled, are designed to displace the exact
 amount of adhesive to form the bond line of predetermined thickness.
 The two mating surfaces are uniquely designed to form a uniform and
 reliable bondline joint when assembled. A suitable structural adhesive is
 applied into the groove. A spatula is used to screed the adhesive,
 removing all of the material except what's left in the groove. The groove
 has been designed to hold the exact amount of bonding adhesive necessary
 to securely bond the two halves together.
 Interlocking pins and slots register the two halves 11a, and 11b in the
 desired location and provides the necessary physical displacement between
 the parts to secure a uniform bond line thickness, and provide the
 necessary fixturing to hold the parts together during the cure cycle. The
 two 90 degree elbows 35 are bonded to the horn 11 using similar fixturing
 techniques. The horn and orthomode junction assembly is then chemically
 and/or mechanically cleaned and plated using the desired metal coatings to
 the required thickness. When using gold flash as the final metal coating,
 no further finishing processes are required.
 Generic ring hybrid networks 16, 17, 18 (hybrid ring power combiner-divider
 networks 16, 17, 18) are molded to "near net" shape in the desired
 physical arrangement. The hybrid ring dimensions are molded in such a
 manner that a minimum amount of material is molded to accommodate a range
 of power division/combinations ratios. Once the specific power division
 relations have been specified, simple machining operations performed on
 the generic networks customize them, making each unique. After machining
 and part marking, the networks 16, 17, 18 are plated (with the desired
 metal coatings for RF purposes) RF loads 26 are installed and the two
 halves are joined. Fastening techniques include rivets 32, chemical
 bonding agents, thermal welding, ultrasonic welding, or other snap or
 interlocking features. Snap interlocking techniques are used to minimize
 installation time, reduce mechanical fastener count and simplify
 integration of individual RF components. Snap features are designed with
 hooks and loops molded as an integral parts of the RF components or may be
 separate components. Each network 16, 17, 18 is molded, machined, plated
 and assembled using the same methods.
 In order to facilitate rapid yet accurate integration of RF subassemblies,
 special RF/mechanical joints are used. The joints are designed as
 male/female slip joints 33 that plug together and are secured using clips
 and springs or integral snap features. The design allows rapid yet
 accurate hand assembly eliminating costly alignment fixtures, hard to
 access traditional screws and inserts, nut and washers. The assembly is
 lightweight due to minimizing, or eliminating traditional hardware and
 flanges.
 Each horn output (two in the disclosed embodiment, horizontal and vertical
 polarization) requires a waveguide element that is manufactured to a
 specific length, used to provide a desired RF phase length for that output
 port. The phase shifter 15 is molded in two halves 15a, 15b (FIG. 9),
 split along the broad wall of the waveguide with integral inter locking
 alignment features. The two halves 15a, 15b are molded net lengths forming
 the longest of a family of phase shifters 15 that are required. The ports
 are marked, plated using desired metal coatings and fastened together. The
 desired phase shift for each port is manufactured from the generically
 molded plastic pieces, plated, assembled and clipped to the desired RF
 port. If another phase length is desired the phase shifter 15 is easily
 removed and replaced using a premanufactured "clip" locking feature.
 A generic molded plastic power combiner-divider network 16, 17, 18 is
 designed to operate over a range of power division ratios by substituting
 the required septum before molding. Each power combiner-divider network
 16, 17, 18 is molded in two halves, split along the broadwall of the
 waveguide, as is shown in FIGS. 6b, 7 and 9. The mold is designed to
 accept a range of inserts used to achieve specific power divisions. The
 number of power combiner-divider network 16, 17, 18 and their ratios is
 predetermined based on a statistical analysis. Once determined, the
 required number of specific ratios power combiner-divider networks 16, 17,
 18 are molded. The design is such that surfaces of the septum 34a are
 noncontacting along the broad wall of the waveguide. After plating a
 resistive load is easily assembled to the septum 34a and the two halves
 joined together forming a unique microwave power combiner-divider network
 element. The combination of these elements in any desired combination of
 power division ratios is easily achieved by interconnections.
 The bond line joints used in producing components of the antenna system 10
 employ interconnecting features that are designed to meter a prescribed
 amount of bond material. A flange RF choke provides a PIM free connection
 between flanges and the broadwall. Snap features include the use of
 beryllium copper (Be--Cu) clips and plastic snaps. Generic RF manifolds
 are molded and then slightly modified using numerically controlled
 machining to produce application specific antennas.
 The reduced-to-practice embodiment of the present invention provides for an
 improved earth deck mounted passive array antenna system 10 that has the
 same RF performance and the same mass as a previously used 1.2 meter
 reflector antenna, costs 75 percent less, occupies 80 percent less earth
 deck area and 95 percent less shroud volume than the previously used
 Gregorian antenna. The passive array antenna system 10 has a lower center
 of gravity than the previously used antenna for improved spacecraft
 inertial characteristics.
 Thus, an improved injection molded phased array antenna system such as may
 be used on satellites has been disclosed. It is to be understood that the
 described embodiments are merely illustrative of some of the many specific
 embodiments that represent applications of the principles of the present
 invention. Clearly, numerous and other arrangements can be readily devised
 by those skilled in the art without departing from the scope of the
 invention.