SIW magic-T with bandpass response

A novel magic-T with bandpass filtering response using substrate integrated waveguide (SIW) technology is presented. The basic design concept is based on properly locating the two power-division ports in a dual-mode circular SIW cavity, whose field distributions are even or odd symmetric. Not only in-phase and out-of-phase operations can be achieved in the magic-T, but also filtering responses for the two operations can be obtained. This magic-T is fabricated in a single-layer PCB and measured results show that it is centred at 9 GHz with 70 MHz 3 dB bandwidth. Good measured performance of balance for magnitude (±0.35 dB) as well as phase (0°-5°) is also obtained within the passband.