Miniaturization Study Of Reconfigurable SIW Filter

With the development of radio in recent years,spectrum resources are scarce and RF modules are increasingly required to operate in different frequency bands.It is a very important and challenging task to maintain or even reduce the final size of the communications system while enabling signal coexistence in different frequency bands.The filter is an essential passive module in the system,and its miniaturization and reconfigurable capacity is the trend of design in the future.Firstly,this paper discusses the filter's general process of circuit synthesis.Then the coupling matrix synthesis process is discussed and the topology of transmission zero is analyzed.Based on the theoretical research of fixed filters,this paper introduces a design method suitable for RF / MW band-pass filter,and designs a seven-order metal waveguide filter.Both of SIW and metal waveguide are very similar in terms of propagation characteristics and resonant coupling.This paper refer to the design method of metal waveguide filter,discuss the design process of SIW filter,and design a fourth-order SIW filter with the same index.For reconfigurable filters,there is a lack of research both in theory and in design.Based on the theory of fixed filter design,this paper studies the design method of adjustable center frequency,adjustable bandwidth and adjustable zero point.The traditional waveguide technology can not be easily adjusted.However,the SIW device is also easily adjustable as a planar structure while inheriting the advantages of the metal waveguide.Therefore,the article discusses the reconfigurable technology of the SIW structure.However,SIW structure compared to other planar structure size is still large,so this article also discusses the SIW structure miniaturization technology which can be used in later reconfigurable filters.According to the theoretical research of the filter and the reconfigurable method,two reconfigurable filters that meet the miniaturization requirements are designed.Both of these filters realize the reconfigurable of the frequency and bandwidth.One is a reconfigurable QMSIW filter with an adjustable frequency range of0.78GHz-1.17 GHz and the bandwidth of each frequency point is reconfigurable.It sues a quarter-module SIW structure,the size is reduced by 75% compared with the the full-mode SIW structure.Also a new kind of method of loading tuning device isused in this design.The other is a reconfigurable RHMSIW filter with an adjustable frequency range of 1.11GHz-1.55 GHz.The bandwidth of each frequency point is reconfigurable.It uses the ridge half mode SIW structure,reduces the size by 84%,and can concatenate the low pass filter to improve the out of band performance.