A miniaturized microstrip interdigital bandpass filter structure
A microstrip loading line is introduced into the open end of the terminal short-circuit interdigital bandpass filter to make the resonator size jump.By changing the line width of the microstrip loading line,the equivalent inductance value of the resonator is increased,so as to reduce the center frequency of the bandpass filter.The empirical formula based on the design indexes for center frequency variation with the change of loading line width is given.The X-band microstrip interdigital bandpass filter and microstrip line size jump are studied.The data show that the shorter the resonator is,the more the center frequency shifts to high frequency.The larger the microstrip line size jump,the more the center frequency shifts to low frequency.The filter is miniaturized by decreasing the length of the resonator and increasing the line width of the microstrip loading line appropriately,reducing the overall length of the filter and keeping its width unchanged,and maintaining its filtering characteristics unchanged before and after the improvement.The filter model is established in HFSS(high frequency structure simulator)and the simulation is carried out.In the improved model,the number of transmission zeros is increased,the return loss(RL)is more stable,the resonator length is reduced by 10%,the line width of the microstrip loading line is increased by 0.15 mm,and the overall filter size is reduced by 10%,which verifies the feasibility of the proposed structure.
万方数据
维普
