Design of higher order miniaturized bandpass filter using two cascaded new multimode resonators

In this paper, a broadband microstrip bandpass filter has been designed by a new multi-mode resonator (MMR) which is further cascaded to improve the performances. The new MMR is obtained from the size miniaturization and modification of conventional rectangular shaped one. The unit consists of low-impedance triangular section in the middle and two identical high-impedance line sections on both sides and it generates multiple resonating modes. The operating bandwidth is thus tunable with the impedance ratio of the high-low impedance line. A bandpass filter is designed using the technique with a 3dB bandwidth of 84% considering impedance ratio of 2.52. The design has advantages of size reduction of around 54.16% in compare with the conventional MMR filter. Two such MMR units are cascaded to improve the selectivity as well as the order of the filter. The design mechanism is advantageous in terms of planar structure, easy to integrate with other MMICs and cost effective.