Design and realization of a microminiaturized filter based on broadside-coupled interdigital structure

To achieve miniaturization of Ultra-wideband(UWB) bandpass filter, a multi-layer interdigital-coupled filter and its design method is proposed. The filter realizes the bigger coupling coefficient using broadside-coupled structure, and unnecessary cross coupling is reduced by widening the width of stripline resonator, It simplifies design method of the filter. A six-pole inter digital bandpass filter centered at 3 GHz with a fractional bandwidth of 58% using the proposed structure is designed and realized, the size of filter is 6mm-10mm. The simulation results show that the filter keeps the advantage of the traditional interdigital-coupled filter with great stopband characteristics and spurious response.