Each radiating element shifter; t h e p h a s e i s changed f o r e a c h beam p o s i t i o n . A m u l t ip l i c i t y o f r a d i a t i n g e l e m e n t s i s combined i n t o a sub-array. Transmitting and receiving amplification, separated by s u i t a b l e T-R d e v i c e s , t a k e s p l a c e a t t n e s u b -a r r a y l e v e l . F o r broad-band operation, time-delay, rather th&n phase, i s adjusted for each a p p r o p r i a t e m e l e n g t h s i n t o t h e c i r c u i t . The r e s u l t m t band-sub-array. This can be achieved, for example, by switching w i d t h in percent then approximately equals numerically the suba r r a y beamwidth i n degrees. The required combining network may For t h e r e c e i v e r , a somevrnat more complex network i s d e s i r a b l e amount t o an equi-phase and equj-power d i v i d e r f o r the transn-&tter. giving separately optimized sum and d i f f e r e n c e p a t t e r n s . S U B -m Y A 48-element sub-array has been developed a t C-band. Power i s s p l i t 4-ways i n the H-plane t o f o u r a d j a c e n t E -p l a n e s e c t o r a l horns as shown i n Figure 2. This method of power d i v i d i n g g i v e s a' constant amplitude distribution across the sub-array. In an array of sub-arrays, t h i s constant amplitude distribution i s i s placed i n t h e mouth of each horn t o c o r r e c t t h e i n h e r e n t required t o suppress grating lobes. A matched d i e l e c t r i c l e n s 1 2 waveguides arranged as shown i n Figure 3. The w a v e m d e s , s p h e r i c a l p h a s e f r o n t . Eacn of t n e f o u r s e c t o r a l h o r n s f e e d s 98
An experimental %-element phased-array antenna is described that has been matched to operate over nearly an octave. Techniques used in designing the aperture-matching networks are discussed and experimental results are presented.The array aperture is formed by broad-band digital latching femte phase shifters in a closely stacked triangular coniiguration. For experimental convenience the array is horn fed from the rear. Matching of this antenna was accomplished by placing double-step dielectric transformers on the input and radiating a p e h e s . Resonances caused by the dielectric transformer on the aperture are discussed. The array operates from 3.5 to 6.5 GHz with scanning to f60' in all directions. The bandwidth is limited at the low end by magnetic resonance of the ferrite phase shifter and at the high end by the aperture resonance.
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