Synthesis of wide-band bandpass filters with quarter-wavelength resonators

This paper presents a synthesis method for the design of wide-band quarter-wavelength-resonator bandpass filters without global optimization. In this method, the improved K-inverter and J-inverter models with the exponent-weighted turns ratio and extra transmission lines are proposed in order to incorporate the frequency dependence of inverters. The proposed synthesis method is applied to the design of a rectangular coaxial wide-band bandpass filters. As a design example, a four-pole rectangular coaxial bandpass filter is designed for 63% fractional bandwidth. The measurement results agree well with the simulation results and show good equal ripple performance. The proposed method is expected to find more applications in the design wide-band bandpass filters.