MIL-STD-220A Versus Classical Measurement of Filter Insertion Loss in a 50-ohm System

Discrep anc ie s have been observed in the data obtained from measurement of i n s e r t io n l o s s us ing MILSTD-220A and other c l a s s i c a l and more t r a d i t io n a l t e ch n iq u e s . This has r e s u l t e d in confus ion fo r des ig ners o f in t e r f e r e n c e suppress ion components, r a i s in g doubts regarding the v a l i d i t y o f MIL-STD-220A and c o r r e c t n e s s of the t e s t procedures s p e c i f i e d t h e r e i n . In t h i s paper, a complete a n a l y s i s o f the t e s t c i r c u i t descr ib ed by MIL-STD-220A i s performed. Using the c i r c u i t c h a r a c t e r i s t i c s o f the matched i s o l a t i o n a t t e n u a t o r s , an equat ion i s d e r i v e d f o r the f i l t e r i n s e r t i o n l o s s . I t i s shown tha t fo r large va lues of a t te n u a t io n provided by matched i s o l a t i o n a t t e n u a t o r s , the va lues o f i n s e r t i o n l o s s obta ined become nearly equal t o the va lues obtained from the c l a s s i c a l equat ion o f the i n s e r t io n l o s s , which agree with experimental r e s u l t s .