Varactor-tuned substrate integrated waveguide phase shifter

In this paper, we present two designs of substrate integrated waveguide (SIW) phase shifter at 26GHz, an inline phase shifter and a reflection-type phase shifter. Two shifters are both fabricated and tested. The measured results correlate with the responses calculated from the equivalent models and EM models. An inline phase shifter tuned by a single varactor has a phase shift larger than 25° over a 30% bandwidth. The variation of the phase shift is less than 2.2° within the band. The 180° reflection-type phase shifter has a measured phase shift more than 180° over a bandwidth of 13% and the variation of the insertion loss is -3.8 ± 0.87 dB within a bandwidth of 15.3%.