Compact and highly-selective microstrip bandpass filter and diplexer using two-stage twist modified split-ring resonators

In this paper, a two-stage compact and highlyselective microstrip bandpass filter is first synthesized and discussed experimentally. The proposed filter composed of two pairs of twist modified split-ring resonators exhibits well filtering properties including three reflection poles within the passband and four transmission zeros below and above the passband. Two of the transmission zeros are very close to the passband, contributing to the highly frequency selectivity properties. Then a compact diplexer based the synthesized filter is designed and analyzed numerically. The diplexer also shows very compact size, highly frequency selectivity, and good port isolation properties.