A Method Based on the Theory of Small Reflections to Design Arbitrary Passband Microstrip Filters

Abstract

A method to design a kind of microstrip filters consisting of only opened stubs and shorted stubs is proposed in this paper. This method is based on the Theory of Small Reflections, and the equations to calculate dimensions of this type of filters is exhibited. Two filters developed by our method are simulated and fabricated. The first filter has a passband on 5~8GHz. The second one is a dual-band filter and can work on both 2.4GHz and 5.8GHz. By using our method, the designed filters only contain opened stubs and shorted stubs, therefore, it is easy to design and fabricate this type of filters. The comparison between calculated and measured reflection coefficient curves shows a satisfactory fitting degree, this manifestation verifies that the method in our paper has a good application in filter design. The position of transmission zeros about the second filter are investigated. All the results show that our method can be a good guidance in microstrip filter design.