High performance compact microstripline phase shifter at C-band using yttrium iron garnet

Microstrip phase shifters, fabricated using thick YIG films, have been described previously and are suitable for a wide range of microwave applications. Earlier designs using ferrite phase shifters require a few thousands of Oersteds magnetic field to produce usable large phase changes (Delta&PHgr;) and suffer from disadvantages of large size and weight. This research aims to fabricate a planar microstripline phase shifter that is compact and light weight using bulk Yttrium Iron Garnett (YIG) material. It is capable of producing large differential phase change (Delta&PHgr;) for very small applied field thus eliminating the need for heavy permanent magnets. YIG material possesses narrow FMR linewidth and low insertion loss at C band frequencies. The propagation direction of the microstrip and magnetization direction of the YIG is collinear, and the length of the microstrip and the YIG is ∼5 cm in length.;The proposed design shows large differential phase changes of 100 degrees for applied magnetic fields from 0 to 5.57 kA/m (70 Gauss) over the frequency range of 1.2 GHz between 5.4 GHz and 6.6 GHz. The average insertion loss, ∼3 dB, was measured to have a bandwidth of ∼ 1.2 GHz. This work also evaluates the effect of YIG material thickness on the phase shift and insertion loss properties of the phase shifter device.;The planar phase shifter presented here demonstrates a compact design, low loss, and an especially large phase shift with a relatively small bias field. This design is particularly well-suited for future microwave and millimeter wave devices applications in which light-weight and high performance are required.