Design methodologies of planar duplexers and triplexers by manipulating attenuation poles

Design methodologies of planar duplexer and triplexer consisting of bandpass filters (BPFs) using different tapped resonators are described. Firstly, we propose a planar duplexer consisting of BPFs using a tapped half-wavelength resonator and a tapped quarter-wavelength resonator. The duplexer is designed based on a classical filter design method with a narrow-band approximation and a tap-coupling method. The experimental duplexer is fabricated using coplanar-waveguide structures. Secondly, a planar triplexer consisting of three types of BPFs is described in a similar manner. The results of this study show that the design methodology is useful for realizing the high-performance planar duplexer and triplexer fabricated without increasing the number of elements.