A new wide stopband microstrip bandpass filter with miniaturized interdigital capacitor resonator

A miniaturized interdigital capacitor resonator (ICR) is proposed in the design of a new wide stopband microstrip bandpass filter. Such an ICR has a curved geometry with small dimension, but with a large equivalent self-capacitance and higher the first spurious frequency. Curved interdigital capacitor structure is introduced to captured larger equivalent self-capacitor. Meanwhile, interdigital capacitor structure is adopted to obtain strong coupling between ICRs to achieve wide bandwidth. The developed filter exhibits sharp skirt and wide stopband, with an excellent agreements obtained between its measured and simulated S-parameters.