Design And Implementation Of Planar Microstrip Filters

The microstrip line filter is used in wireless communication systems widely for many advantages such as compact size, low cost and easy to be integrated with other circuits.Firstly, a new fourth-order cross coupling microstrip filter with a source-load coupling technology was designed in this thesis. The filter with a center frequency of2.414GHz and a relative bandwidth of2.5%, have a pairs of real frequency transmission zeros at2.232GHz and2.54GHz for skirt selectivity. An octagonal shape of this filter was constituted by headers and trailers connect between four resonators. And the load lines between resonators can strengthen their coupling. A pairs of real frequency transmission zeros can be more easily adjusted with the source-load coupling in this filter. Then the filter was manufactured and measured.Secondly, a novel dual mode square ring band pass filter was designed. The center frequency, relative bandwidth, and maximumin band return loss of this filter are1.634GHz,6.8%,17dB,respectively. A pairs of real frequency transmission zeros at1.5GHz and2.1GHz can enhance skirt selectivity. And its butterfly radial stub structure, ring resonator and local ground defect structure was analyzed. Then the filter was manufactured and measured.