Novel Microwave Bandpass Filter with Microtrip Cross-Coupled Square Open-Loop Resonators

A novel cross-coupled band pass filter (BPF)based on the flute resonator is proposed. Due to the adoption of the same new configuration of coupling coefficient, the distance between the two loops is clearly shortened, which offers BPF an advantage of miniaturization. The configuration is characterized by a higher Q factor by introducing two transmission zeros in the transfer-function. The structural parameter of the coupling coefficient of this configuration is achieved through the analysis of electromagnetic software CST. Thereby, the band pass filter used in X waveband is designed with a dimension of 5.9 mm×5.9 mm, in-passband insertion loss (IL) of 3.2 dB, and out-passband IL of 25 dB. The result of the experiment agrees well with simulation.