A filter synthesis method for quasi-elliptic dual-passband filters

This paper presents a new synthesis method for the quasi-elliptic LC prototype of multi-passband filter. The optimized poles and zeros satisfying the required multi-passband filter response are achieved by optimized algorithm. Transfer and reflection functions were also calculated. Using the roots of these functions, the quasi-elliptic LC prototype was synthesized. To verify the proposed synthesis method, a dual-passband filter operating at GSM(880~960 MHz) and ISM(2400~2500 MHz) was designed and fabricated. The measured frequency response shows good agreement with the theoretical and simulated ones.