Compact and low cost substrate integrated waveguide cavity and bandpass filter using surface mount shorting stubs

A compact and low cost substrate integrated waveguide (SIW) cavity and bandpass filter using Surface Mount (SM) shorting stubs is proposed in this paper. These cavity and filter allows a drastically reduction in Printed Circuit Board (PCB) footprint. They are compact and also low cost as there fabrication involves standard PCB process and SM technologies. For demonstration purpose, one cavity and one 7th order bandpass filter were designed and fabricated over Ka-band. The cavity is designed at the center frequency of 34 GHz. It achieves an unloaded Qu factor of 201 with a footprint of only 1.9 × 6.3 mm² compared to 5.38 × 6.3 mm for a planar cavity. Then, a 7th order filter is designed at the center frequency of 34.5 GHz. It provides a sharp frequency selectivity using arranged transmission-zeros and achieves a bandwidth of 1 GHz with an insertion loss of better than 2.9 dB with a footprint of only 11.2 × 6.3 mm². The experimental prototypes achieve good performances. They potentially have many applications in microwave and millimeter wave devices, circuits and systems.