Design of balanced dual-band bandpass filter based on substrate integrated waveguide

For the first time, a balanced dual-band bandpass filter using a substrate integrated waveguide structure is reported. The co-shared TE₁₀₂-mode cavities arranged on the symmetrical plane can greatly reduce the common-mode signal while selectively transmitting the differential-mode (DM) signal. In addition, the desired DM response can be easily analysed and obtained by the equivalent 2-port circuit model. To validate the design concept, one X-band prototype has been fabricated and tested. The measured results match well with the theoretical counterparts.