A Microwave Nonreciprocal Notch Filter Tunable by a Surface Acoustic Wave in Dynamic Magnonic Crystals

The results of using a dynamic magnonic crystal, which is created by a surface acoustic wave (SAW) in the structure of a film of yttrium iron garnet on a gallium gadolinium garnet substrate, for the development of a tunable nonreciprocal microwave filter are presented. A filter prototype that operates in the range of 3600-4200 MHz at a magnetic bias field of 640 Oe was developed and its main characteristics were measured. At a SAW frequency of 41 MHz and a power of 30 mW, the rejection depth was 23 dB. A SAW-frequency change by 1 MHz shifted the rejection frequency by similar to 7 MHz. The inversion of the signal-propagation direction in the device resulted in a shift of the rejection frequency by the value of the SAW frequency. The possibilities of the further improvement of the parameters of this device are discussed.