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The results of applying the planar nearf i e l d measurement technique t o two experimental phased array antennas are described.Fast and e f f i c i e n t tests are used to determine the required scan area and data point spacings.The use of t h e s e tests e n a b l e o n e t o r e d u c e t h e amount o f d a t a r e q u i r e d f o r some antennas without seriously inc r e a s i n g t h e e r r o r s i n computed f a r -f i e l d p a r ameters.Measurements were made a t d i f f e r e n t d i s t a n c e s from the antennas, with the probe transmitting and receiving, and for both sum and monopulse d i f f e r e n c e p a t t e r n s o f t h e t e s t antenna. Comparisons between t h e f a r -f i e l d p a t t e r n s computed from the nearf i e l d d a t a and t h o s e measured on f a r -f i e l d r a n g e s are presented.An experimental system to t e s t t h e p o t e n t i a performance of a two-pulse, four-element adaptive array has been constructed, using two four-element a r r a y s t o r e p r e s e n t t h e r e c e i v e r f u n c t i o n and 8 s i g n a l s o u r c e s d i s t r i b u t e d i n a z i m u t h t o r e p r e s e n t c l u t t e r . R e s u l t s a r e r e p o r t e d on t e s t s which a r e i n p r o g r e s s t o e v a l u a t e t h e l i m i t a t i o n s o f m u t u a l coupling, receiver match, A I D conversion, and simulated platform motion.The requirements for a t r a n s m i t t e r -r e c e i v e r t h a t i s d i s t r i b u t e d s p a t i a l l y on an a r r a y a r e reviewed and the design of the RF and the power supply packages are described.Details o f t h e major RF components are discussed as w e l l as overa l l parameters such as c o s t t r a d e -o f f s and a r r a y s i g n a l and power d i s t r i b u t i o n problems. a development program f o r a 40 w a t t , S-Band t r a n s m i t / receive module. The module c o n t a i n s , t r a n s i s t o r amplifiers, diode phase shifters, and crossed d i p o l e s f o r o p e r a t i o n w i t h a l l s e n s e s o f l i n e a r and c i r c u l a r p o l a r i z a t i o n s .One hundred modules were fabricated for an experimental 10x 10 suba r r a y .