The Miniaturization Research Of Interdigital Microstrip Bandpass Filter

The interdigital microstrip filters with bandwidth to adapt to large scope, as well as the advantages of lower production costs, are used in electronics, telecommunications and other areas widely. The miniaturization research of it for improving the integration, reduce production the cost of great significance.First, summarized microwave filter miniaturization research situation, and introduced the design theory knowledge about microstrip microwave filter, and described the design method of interdigital microstrip filters High-frequency simulation software Ansoft Designer was used, and a fifth-order L-band cross-finger-type microstrip band-pass filter was used as an example, by adjusting the relevant physical parameters, observed the simulation results of S curves, finally qualitative obtained their physical parameters laws affecting of its filtering performance. The results show that the greatest impact on the center frequency is the length of the resonator, When the resonator length larger then the center frequency decreases. However changed the length of resonator, pass-band bandwidth is almost no effect. The major impact of spacing on the performance of the filter in the pass-band bandwidth, with the increasing distance between resonators pass-band bandwidth is decrease. VSWR within a closely related position with the tap, but the length of filter tap on its center frequency, bandwidth, so little impact. On these basis, adjusted the corresponding physical parameters to meet design specifications.Finally based on the working principle of the interdigital filter founded that change the structure would not affect the transmission performance, through a large number of simulation experiments, designed a new type of interdigital microstrip band-pass filter, and changed the traditional structure of the coupling and coupling method, and adjusted accordingly in accordance with relevant interdigital microstrip filters physical parameters of law of its performance, the final design of its original area of only 67.8%.Simulation results show that the improved filter is still to meet the design requirements, and ultimately achieving the purpose of miniaturization, to prove the feasibility of this method.