Tunable ferrite phase shifters using substrate integrated waveguide technique

Substrate Integrated Waveguide (SIW) is a very promising technique in that we can make use of the advantages of both waveguides and planar transmission lines. As a waveguide, we can get such advantages as low loss, high Q factor, high power capability and small radiation. And as a planar transmission line, we can fabricate it in a compact size at a low cost. In this letter, ferrite phase shifters are designed and experimented using substrate integrated waveguide (SIW) technique to take advantages mentioned above. The first attempt to design a ferrite phase shifter using SIW was made by Wenquan et al. However, an experimental result was not presented maybe because of a fabrication difficulty of ferrite toroid which was supposed to be used in the design. A quite good performance of ferrite circulator in SIW structure was obtained by William et al. However, the design was implemented in a fixed bias. In this letter, tunable ferrite phase shifters using SIW technique are presented and experimentally demonstrated. Ferrite slabs are placed where circular polarization occurs along the SIW. Static magnetic field bias is applied to magnetize the ferrite slabs in transverse direction. In this letter, a variable magnetic field biasing method is presented and implemented. Measurement and simulation results of both single ferrite slab and double ferrite slabs phase are presented.;Measurement results of a tunable single and double ferrite slab phase shifters using SIW technique were presented. About 160° of differential phase shift was achieved in the single slab ferrite phase shifter and 190° of differential phase shift was achieved in the double ferrite slab phase shifter. The achieved figure of merit at 24GHz with the double ferrite slab phase shifter using SIW technique in this experiment is 95°/dB.