An anechoic chamber used for missile test or simulation inherently adds boresite error, generally as a result of sidewall reflections. A simple method of analysis shows this error depends on the sidewall angle of arrival through the antenna difference pattern and the bistatic reflection coefficient of the sidewall material. This material coefficient which is seldom measured is of critical importance. CORRESPONDENCEI1211l
Valley Forge Space Center user requirements i s t h e " r a i s o n d ' e t r e " of the multibeam antenna. The need f o r a lightweight, high gain device with this capability led to the development beam forming networks. This paper discusses the hardware, the optimum-gain of b o t h a 1 9 beam and 6 1 beam lens antennas with electronically switchable beam synthesis algorithm and t h e computer c o n t r o l l e d d a t a b a s e a c q u i s i t i o n a s s o c i a t e d w i t h t h e o p e r a t i o n of t h e 1 9 beam transmit antenna. The a b i l i t y t o s p e c i f i c a l l y " t a i l o r " a n t e n n a p a t t e r n s t o s a t i s f y v a r y i n g The transmit antenna i s a 19 beam waveguide lens device that i s a b l e t o produce a 4 O "spot coverage" beam which can be varied, via the beam forming nous s a t e l l i t e . The waveguide l e n s , a well-known d e v i c e t h a t i s much documented network (BFN), t o i n c l u d e t h e e n t i r e 1 8 ' e a r t h ' s f i e l d of view from t h e spnchodimensional array of aluminum tubes (chem-milled to .009 wall thickness) i n t h e l i t e r a t u r e , h a s a 28" diameter and a n f / d r a t i o of 1. It i s a two mechanically bonded together with the waveguides touching side-by-side to form t h e f a m i l i a r c o n c a v e l e n s s t r u c t u r e . A single zone, for weight reduction, has been introduced into the lens contour. The feedhorn array i s a hexagonally shaped c l u s t e r of 1 9 horns spaced 1.6 a p a r t on a s p h e r i c a l s u r f a c e of 28" Figure 1. The 19 element feed array i s seen i n F i g u r e 2 a s i t was being r a d i u s . The assembled transmit MBA, w i t h i t s beamforming network, i s shown i n assembled. The beam forming network (BFN) c o n s i s t s o f 18 v a r i a b l e power d i v i d e r s (VPD) arranged i n a binary tree having 19 output ports. The BFN was manufactured by Electromagnetic Sciences Corporation, Atlanta, Georgia. The VPD c o n s i s t s o f a magic tee i n p u t , two 9 0 ' f e r r i t e p h a s e s h i f t e r s and a 9 0 ' component VPD's a r e l a t c h i n g f e r r i t e d e v i c e s w i t h 6 b i t s of c o n t r o l . Each r e c e i v e BFN has 6 b i t f e r r i t e p h a s e s h i f t e r s on e a c h o u t p u t p o r t f o r a d d i t i o n a l sidewall hybrid output. A VPD schematic i s shown i n F i g u r e 3 . (The 6 1 p o r t control.) models to determine the required amplitude and phase f o r t h e s e v e r a l c o n s t i t u e n tFormerly, particular shaped patterns have been created using analytical beams. Experimentally, these parameters were continually adjusted to achieve CH134E-5/78/0000-011OSOO~75 0 1976 IEEE 1 1 0
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