A magnetically- and electrically-tunable microwave phase shifter using yttrium iron garnet/gadolinium gallium garnet thin film

A new type of tunable microwave phase shifter that combines ferromagnetic resonance (FMR)-based magnetic tuning in a yttrium iron garnet-thin-film and DC electrical tuning in a varactor-loaded composite band-pass filter is reported. For the frequency range of 10.37 to 10.87 GHz, a phase shift of 147.5 to 280° was first obtained by applying a reversed bias voltage from 6 to 18 V, and the total phase shift was subsequently increased to 406.5° by varying the bias magnetic field from 2700 to 3450 Oe. The corresponding insertion loss variation measured ±1.5 dB. Similar performance figures could also be obtained for other frequency ranges by varying the bias magnetic field and the corresponding FMR frequency. Thus, the composite phase shifter has clearly demonstrated its capability for a large and continuously tunable phase shift with a moderate insertion loss variation over a wide range of operating frequencies.