Low cost stripline medium and its applications

Abstract

Many planar and c y l i n d r i c a l a r r a y s t o be b u i l t i n t h e f o r e s e e a b l e f u t u r e can be made conveniently from an assembly of identical linear arrays (columns o r rows) incorporating radiating elements and i n t e g r a l power distribution networks. There i s a continuing need t o minimize the cost and often also the weight of such assemblies. The work described i n t h i s paper was performed t o test a technique which appeared t o offer the desired properties. Linear arrays of dipoles with in-Typically, a 1/4-inch sandwich costs $3.50 per square foot in materials, weighs t e g r a l power d i v i d e r s 'nave been fabricated using a n o v e l s t r i p l i n e medium. of 1 2 f e e t o r more. 113 pound per square foot and can be manufactured a s m o n o l i t h i c u n i t s i n l e n g t h s The elements of t h e b a s i c s t r i p l i n e medium a r e shown on Figure 1. They c o n s i s t of t h i n aluminum s k i n s f o r ground planes, a c e n t r a l membrane on which honeycomb t o p r o v i d e t h e s e p a r a t i o n . These elements a r e bonded together using t h e p r i n t e d c i r c u i t p a t t e r n is typically photo-etched and two l a y e r s of nylon a thermo-plastic adhesive film in a thermal press at 2&OoF. Detailed information on t h o s e m a t e r i a l s i s provided in Table 1. The e l e c t r i c a l p r o p e r t i e s o f t h e medium w e r e derived from measurements of resonant frequency and Q f a c t o r i n a s h o r t c i r c u i t e d s e c t i o n of transmission l i n e . T y p i c a l r e s u l t s a r e t a b u l a t e d below. Frequency Thickness S t r i p w i d t h Impedance Eff. Dielectric Loss, dB/A 1 . 3 GHz 1 14'' .320" 5 OQ 1.17 0.08 3.0 GHz 114" .136" aaR 1.17 0.10 A number of standard components were designed i n t h i s medium including end coaxial launchers, mitered bends, asymmetric split-tee power d i v i d e r s and cop l a n a r d i r e c t i o n c o u p l e r s , w i t h no unusual behavior observed. The r a d i a t i n g elements selected were stripline dipoles, fed by a deformed hybrid-ring a s a b a l u n . T h i s s i m p l i f i e s t h e f a b r i c a t i o n p r o c e s s s i n c e a l l t h e p r i n t e d c i r c u i t is contained on the central membrane; r e g i s t r a t i o n w i t h t h e o u t e r ground planes is n o t c r i t i c a l . T y p i c a l l y , a s i n g l e d i p o l e X14 over a ground plane w a s matched t o w i t h i n a VSWR 5 1.2 over a 30% bandwidth. All of the above components have been i n t e g r a t e d t o form an 8-element, Lband l i n e a r a r r a y , t h e c i r c u i t r y f o r which i s shown on Figure 2. The power *This work was sponsored by t h e Department of t h e Air Force. The views and conb e i n t e r p r e t e d a s n e c e s s a r i l y r e p r e s e n t i n g t h e o f f i c i a l p o l i c i e s , e i t h e r ex-c l u s i o n s c o n t a i n e d i n t h i s document a r e t h o s e of t h e c o n t r a c t o r and should not pressed or implied, of the United Stat...