Research And Design Of Tunable Microstrip Filter

With the rapid progress in the field of communication,while facilitating people's daily life,it also makes a large number of spectrum occupied,resulting in the shortage of spectrum resources,and then the phenomenon of congestion.Therefore,some techniques such as spread spectrum and dynamic frequency distribution have been widely used to realize the intelligent use of radio spectrum in order to slow down the phenomenon of radio spectrum congestion.Adjustable filter can quickly tune the frequency,but also to a certain extent reduce the volume of the receiver,so more and more researchers pay attention to it.The main work of this paper is as follows:First of all,the technical specifications of the filter design are introduced,the filter principle and the conversion process from low-pass prototype filter to microstrip filter are described in detail,and several methods of tuning are compared.Varactor diode and pin diode are selected as the focus of this paper.Secondly,by analyzing the characteristics and coupling structure of the filter topology,a dual band-pass filter is designed,which can cover WLAN and Wi MAX frequency bands.The filter is composed of two half wavelength resonators,and the cross coupling between the source loads is designed.The coupling position between the resonators is optimized by hfss15.0 simulation software,and a double pass band filter with better performance is designed.The test results are basically consistent with the simulation results.Then,after the improvement of the traditional e-resonator,a compact band-pass filter and a duplexer are designed.The simulation results show that the designed filter and diplexer meet the basic performance standards.Finally,a dual pass band switched tunable band-pass filter is designed by using pin diode and varactor diode.By analyzing the topological structure of the filter,the principle of the filter and the principle of the transmission zero point are explained in detail.By controlling PIN diode and varactor diode,frequency band switching and tuning are realized respectively.Compared with other filters,the designed filter has some advantages in size and tuning range.