Shaping patterns with a beam transit MBA

Abstract

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