Abstract
An economical compact narrowband bandpass combline filter with coaxial input is presented. A novel configuration using identical post with capacitance-loading is introduced. Simulated results show that with order-5 filter centered at 2.0175 GHz, return loss lower than -18 dB can be achieved over a relative bandwidth of 0.75%. Sample filter has been fabricated and tested result confirmed the concept and the simulated results. In this paper, simulated and tested results will be given to illustrate the concept.