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 are exhibited. Two filters developed by our method are simulated and fabricated. The first filter has a passband on 5~8 GHz. The second one is a dual-band filter and can work on both 2.4 GHz and 5.8 GHz. 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 positions 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.

A Novel Method to Design Stub-loaded Microstrip Filters with Arbitrary Passband Based on the Reflection Theory and Monte Carlo Method

“…In [26], we propose a method based on the TSR to design microstrip filters with arbitrary passbands. In that paper, a novel stub-loaded microstrip filter is proposed and the approximative reflection coefficient function at the input port of the filter is derived.…”

“…In that paper, a novel stub-loaded microstrip filter is proposed and the approximative reflection coefficient function at the input port of the filter is derived. In this paper, we present a modified version of the method in [26]. Our modified method can achieve more accurate calculation results than the method in [26].…”

“…In this paper, we present a modified version of the method in [26]. Our modified method can achieve more accurate calculation results than the method in [26]. The reflection coefficient function becomes very complex, so it is difficult for us to solve the dimensions of our filters from the reflection coefficient function.…”

“…A LPF is designed and compared with filters proposed in [24] and [29] in order to show the advantages of our proposed method and filter. At last, the frequency responses of a dual-band microstrip filter proposed in [26] is recalculated by the method proposed in this paper to justify the application of out modified method in the narrow band and multi-band situations.…”

“…This method is known as the TSR. In [26], a modified version of this theory is proposed and implemented in microstrip filter design, and a novel kind of stub-loaded filters is proposed. The parallel opened-and shorted-stubs are used to change the norm of the local reflection coefficients of the main transmission line in this novel stub-loaded filter.…”