Compact Microstrip Lowpass Filter with Low Insertion Loss for UWB Medical Applications

Abstract

A microstrip lowpass filter based on transmission line elements for UWB medical applications is proposed in this paper. The filter is constructed of two symmetric shunt open-circuited stubs and three series unit elements. The filter is designed to exhibit an elliptic function response with equal ripple in the passband and the rejection band. A prototype is successfully designed, fabricated, and measured, where a good agreement is attained. The filter shows a high filtering selectivity and an ultra-wide stopband up to 20 GHz with an attenuation level of more than 20-dB. The filter is compact and has a low insertion loss and an ultra-wideband (UWB) rejection which makes it attractive for many technologies such as UWB medical applications.