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Active phased array antennas use a large number of TransmiVReceive (T/R) modules at the antenna aperture. These antennas require complex RF power dividedcombiner beamforming networks. DC power is generally provided by distributing power supplies at the antenna aperture that provide DC power to a group of T/R modules. High power T/R modules for phased arrays typically require liquid cooling. A typical phased array, then, might have a large number of RF, DC and logic connections at the antenna aperture.Since most of the active components are distributed at the aperture, in order to maintain the antenna performance, it is necessary to provide a means of easily replacing these components when they fail.A typical phased array will have thousands of RF, DC, logic and fluid connections. We describe a packaging scheme for an active phased array antenna that is easy to maintain, and requires very few disconnections for repairs A fabricated demonstration array and associated components are shown in Figures 1 and 2.The antenna incorporates the use of a monolithic faceplate, machined with great precision in order to achieve a set number of waveguide radiating elements, which form the antenna aperture. The machined radiating elements are capped off with a dielectric window, which is bonded in place, to provide protection against environmental and operating extremes.The T/R Modules/Control Modules/Power Supplies/Combiners and Power and Logic busses are mounted directly to vacuum brazed liquid cooled cold plates. These cold plates perform a dual function, as an integral part of the antenna structure and the means of controlling component temperatures by efficiently removing dissipated heat during antenna operation. Each cold plate has components mounted on both sides, using a built-in component offset to maintain the specified component element spacing and pattern. The use of vacuum brazed cold plates provides the flexibility to direct the coolant flow in the most efficient manner possible, in order to maximize the heat removal on critical (high power) components, thus decreasing junction temperatures and increasing operational life. The vacuum brazing feature also yields design flexibility, in that the brazing operation is fluxless and there is no requirement to include large voided areas in the cold plate for flux washout. *Retired 1608

Low sidelobe phased array antennas require precise control of the amplitude and phase illumination functions.A recent design uses a nearly circular aperture w i t h 4350 radiating elements arranged combiner networks used t o form the elevation sum and elevation i n 79 columns and 139 rows. This paper describes the column difference signals for each of the 79 columns. Since the array has centerline synnnetry, 40 different designs are needed. Using the smallest has 8 i n p u t s .two-element subarrays, the largest combiner has 36 inputs whileThe combiner networks are essentially multiple interferometers where signals from two-element subarrays equidistant from the array c e n t e r l i n e a r e combined i n three branch hybrid junctions to form partial sum and difference signals. The p a r t i a l sum signals and p a r t i a l d i f f e r e n c e s i g n a l s a r e then separate1 combined w i t h ladder networks of weighted split-tee power dividers T . A schematic of a typical combiner network is shown i n Figure 1. The s t r i p l i n e c i r c u i t f o r each combiner, consisting of up t o 17 one-ounce copper on a 0.004-inch thick Teflon/glass substrate. hybrid junctions and 34 s p l i t -t e e power combiners, is etched from The e t c h e d c i r c u i t which may be as large as 47-inch by 17-inch is a 0.064-inch layer of polyimide/aramid fiber honeycomb between t h e supported between two t h i n aluminum ground planes by interposing c i r c u i t and each ground plane. The s t r i p l i n e assembly, w i t h a ground plane spacing of 0.132-inch, is bonded t o g e t h e r t o form a semi-rigid light-weight device. A dimensioned cross-section is shown i n Figure 2. Physical constraints of the array package require t h a t r i g h t angle surface-launch connectors be used a t a l l o f t h e combiner ports. maintain the quasi-TEM integrity of the device. These Self-jigging metallic inserts are used a t each launcher to maintain dimensional tolerances during the bonding operation a t inserts, together w i t h a metallic edging, provide hard points to elevated temperature and pressure. Design o f t h e s p l i t -t e e power dividers was complicated by the requirements that the resistor handle several kilowatts of peak phase be nearly equal for the two ports and nearly equal for all power and several watts of average power, and t h a t the transmission of the coupling values. The r e s i s t o r is a thick-film deposited on a specially shaped beryllia body. Capacitance associated w i t h the r e s i s t o r was compensated by the addition of two open-circuited stubs and by adjusting the dimensions of the matching transformers.