Design of a microstrip multi-band bandpass filters using the filter synthesis method

This paper presents a new L-C prototype of the quasi-elliptic multi-band bandpass filter using the synthesis method. The pole -zero placing technique is used to synthesize the filter. The quasi-elliptic network can be synthesized from poles and zeros obtained from the optimization process. L-C prototype element values can be extracted by the impedance or admittance elimination method. The design of a multi-band bandpass filter operating at GSM (880~960 MHz) and WLAN (2400~2500, 5250~5350 MHz) is presented and realized to verify the proposed synthesis method. The measured frequency response shows good agreement between the theoretical and simulated responses.