Compact Four Band Microstrip Planar Filter using Combined Stepped Impedance and Slotted Rectangle shaped Resonator

A novel four band bandpass filter (BPFs) using two symmetric resonators is proposed in this paper. The proposed filter is designed by combining stepped impedance resonator and slotted rectangle shaped resonator. The filter achieves four pass bands from 0.957 GHz – 1.166 GHz (Impedance BW = 19%), 4.048 GHz-4.103 GHz (BW=2%), 6.083GHz-6.941 GHz (BW=13%), 9.02 GHz – 9.26 GHz (BW=2%). The proposed filter range covers WLAN, WIFI and X-band applications. It is shown form simulation results that the resonance at 6.2 GHz is independently controllable by varying the length of T-shaped resonator. The proposed filter incurs low insertion losses of 0.5dB, 0.4 dB, 1.49 dB and 2.5 dB at 1.1 GHz, 4.1 GHz, 6.2 GHz and 9.1 GHz, respectively.