2-Stage microstrip combline BPF with capacitor chip incorporation

Abstract

In this paper, the design and implementation of 2-stage microstrip combline bandpass filter (BPF) is proposed with capacitor chip incorporation. The initial design of filter is taken from the existing one with some improvements in the performances to be suitable for the 2.4GHz application. The proposed filter is designed on a 0.8mm thick FR4 Epoxy dielectric substrate with the dimension of 8.9mm × 32mm. Two tuning capacitor chips of 2pF are incorporated into resonators of filter and another capacitor chip is inserted into inter-resonator to connect each resonator of filter. After obtaining an optimum design, a prototype of 2-stage microstrip combline BPF is realized through wet etching technique. From characterization result, it shows that the realized filter has center frequency of 2.375GHz with -3dB working bandwidth of 170MHz. The measured bandwidth is 30MHz narrower than the simulated one which has center frequency and -3dB working bandwidth of 2.4GHz and 200MHz, respectively.