Spurious Suppression of a Parallel Coupled Microstrip Bandpass Filter with Simple Ring EBG Cells on the Middle Layer

This paper proposes a parallel coupled microstrip bandpass filter (BPF) with ring Electromagnetic Bandgap (EBG) cells on the middle layer for spurious suppression. The ring EBG cells of the middle layer add a good stopband-rejection mode to the second harmonics of the parallel coupled microstrip BPF with suppression of over −50 dB, without affecting the center frequency and insertion loss of the original designed BPF. The design of ring EBG cells is presented and verified by the experimented results. key words: electromagnetic bandgap (EBG), bandpass filter (BPF), spurious, suppression