Differential Wideband Bandpass Filter With High-Selectivity and Common-Mode Suppression

A circuit for differential wideband bandpass filter (BPF) is presented. The circuit works as a bandpass and bandstop filter under differential- and common-mode excitation, respectively. Under differential-mode, two transmission zeros are generated by the short-ended parallel-coupled stubs and supply a very sharp differential passband. The circuit parameters are analyzed and given to show the circuit characteristics. Finally, the circuit is implemented using microstrip technology and a differential wideband BPF is designed, simulated and measured. Simulated and measured results are well agreed.