Dual-Band Impedance Transformer Based on General Coupled-Resonator Filter Theory

A kind of dual-band impedance transformer based on general coupled-resonator filter theory is proposed. By additionally taking impedance property of dual-mode resonator into consideration, the constructed dual-band filter could match to arbitrary required impedances. Besides different filtering specifications in two bands, different impedances in two bands can also be matched. Detailed design procedure for dual-band impedance transformer with any required different port impedances, center frequencies, bandwidths and return losses in two bands is displayed.