Integrated Dual-Band Radiating Bandpass Filter Using Dual-Mode Circular Cavities

A new technique for the design of integrated dual-band multilayer substrate integrated waveguide (SIW) bandpass filter and microstrip antenna is presented. The design is based on a dual-mode TM110 circular cavity structure, where two orthogonal modes co-exist in a single layer. The first layer has the first resonator for each band, and the second layer has the second radiating resonator. The two layers are coupled via capacitive rectangular irises at the common ground plane. The complete integrated device behaves as two second ordered bandpass filters each of which simultaneously filters and radiates. Simulation and measured results exhibit excellent agreement with the return loss level of 8 dB and gain of 5 dBi at 1.96-1.988 GHz and 2.06-2.09 GHz. This technique has the advantage of miniaturizing the overall structure and eliminates the need of external matching circuits.