Compact spiral band pass filter with low group delay

A complementary coupled spiral transmission line with center via is proposed to design band pass filter with compact and simple profile, low group delay, and low insertion loss. A compact wideband band pass filter is designed and fabricated for demonstration which has 26% bandwidth, 0.3 dB insertion loss, and compact size as 0.41 × 0.23 λg with very low group delay, 0.28 ns. These good specifications prove the capability of the proposed approach to design of band pass filter compared with the literatures.