Synthesis Design on Wideband Single-Ended and Differential Dual-Band Filtering Impedance Transformer

In this brief, a novel dual-band wideband impedance transformer (IT) integrated with the function of dual-band bandpass filtering was proposed for the first time. The presented design, based on the equivalents of dual-band J-inverters and LC resonators, has a simple structure with parallel open/short-circuited stubs and cascading transmission lines. Analysis results show that the considered ITs can work at two separate uncorrelated frequency bands with arbitrary terminated real impedances. For demonstration, a wideband single-ended dualband filtering impedance transformer (DBFIT) with the filtering order n = 4, and a differential DBFIT with n = 3, are designed. In particular, the common-mode rejection of the differential circuit is well considered. The simulated and measured results are recorded in good agreement, well verifying the design concept.