High Selective Microstrip Bandpass Filter and Diplexer With Mixed Electromagnetic Coupling

Abstract

A high selective bandpass filter and a high isolation diplexer by using mixed electromagnetic coupling have been presented. The filter transmission zeros (TZs) are attributed to the mixed electromagnetic coupling, and additional resonators are not required. TZs also can be adjusted by controlling the electric and magnetic couplings. The diplexer is fabricated and measured, and the new design is demonstrated by measurement. The diplexer has a compact size of 0.483λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ×0.585λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> , and a measured high isolation of no less than 42 dB.