Design of Microstrip Diplexer and Dual-Band Filter Using Quarter-Wavelength Stepped-Impedance Resonators
Date Issued
2010
Date
2010
Author(s)
Chang, Shin-Yui
Abstract
A novel microstrip diplexer with a compact size and high isolation is proposed in this thesis. It is formed by two four-pole cross-coupled bandpass filters placed side by side and combined through a T-junction. The filters are designed with quarter-wave stepped-impedance resonators (SIRs) to achieve simultaneously size reduction and better control of spurious responses. Though the filters are closely placed, higher isolation can still be obtained by properly designing the T-junction. Moreover, the possibility for the magnetic-coupled SIRs in the proposed diplexer to use a common shorting via is also discussed, and a modified design is presented. An optimized design composed of quarter-wavelength SIRs with the minimum lengths is also demonstrated. Besides, based on the above design method, three types of dual-band microstrip bandpass filters are also proposed. Lastly, two microstrip-fed planar antenna designs are introduced and integrated with the proposed diplexer.
The performances of all the circuits presented, including the diplexers, dual-band filters, microstrip-fed planar antennas, and the integrated diplexer and antenna, are all verified through both simulations and measurements, and they agree well.
Subjects
Stepped-Impedance Resonators
Diplexer
Type
thesis
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