Theoretical and Experimental Transfer Impedance for Concentric Layers of Coaxial Shielding

Abstract

Modeling c o n c en tr i c layers o f braided s h i e l d s i s an in t e g r a l par t o f system hardening techno logy fo r Elec tromagnet ic Pulse (EMP) phenomena. To determine the accuracy o f a m u l t i p l e s h i e l d model, the model i s compared to measured data . This paper compares th e o ­ r e t i c a l and experimental t r a n s f e r impedance data f o r one , two and three la y er s o f machine-braided s h i e l d s . The experimental data was obta ined us ing a quadraxial t e s t f i x t u r e from 1 kHz t o 100 MHz. These r e s u l t s confirm S c h e lk u n o f f ' s t o t a l t r a n s f e r imped­ ance theorem^. The measured data a l s o showed t h a t the h igh-frequency , t o t a l t r a n s f e r impedance model (due to aperture coupl ing) i s inadequate to de sc r ib e m u l t i p l e l a y e r e d braided s h i e l d s s i n c e the t r a n s f e r impedance i s found not t o be d i r e c t l y proport ional to frequencyZ .