A Compact Microstrip Multi-layer Bandstop Filter Using Meandering Transmission Line Structure

A compact microstrip multi-layer bandstop filter is proposed in this paper. The filter consists of a main transmission line and eight resonators on the two-layer structure. The main transmission line placed on two layers is connected by a circular metal via hole. Each layer of the structure has four U-shaped resonators coupled with the main transmission line to design a compact eighth-order microstrip multi-layer bandstop filter. To verify the proposed multi-layer structure and design approach, a microstrip multi-layer bandstop filter has been simulated and measured. The measured center frequency and insertion loss are 1.56GHz and 1.26dB respectively, and the results show maximum stopband rejection up to 47dB.