The miniaturization design of microstrip interdigital bandpass filter

The L-band band-pass interdigital filter was studied, a large number of experimental data showed that bandwidth narrowed with the increasing of resonator width, and the center frequency becomes larger with the reducing of the resonator length; the bandwidth will widen when the distance between resonator was reduced. Change coupled structure, increase the effective coupling area of the microstrip line can make the structure of filter more compact, so as to reduce filter area. Based on these conclusions, a new type of filter was designed. Compared with the traditional interdigital filter, the size of the new filter was only 71.4% of that of the original one.