Magnetostatic surface wave devices for UHF and L band applications

Magnetostatic wave (MSW) delay lines and filters made with gallium-substituted garnet films (Ga:La-YIG) are described. These devices were tuned over the 0.3 - 2 GHz frequency range by varying the dc bias field in the range 10-500 Oe depending on the saturation magnetization of the garnet film, therefore complementing already demonstrated MSW devices covering the 2-15 GHz frequency range. Techniques for reducing the amplitude and delay ripples and for minimizing the coupling to elastic resonances are described. The agreement between theoretical predictions, measured amplitude and group delay responses was fairly good. Typically, for a delay line at 500 MHz, the insertion loss is l0 dB; the amplitude ripples are less than 0.5 dB peak-to-peak and the group delay ripples are less than 10 nsec peak-to-peak. Linearly dispersive delay lines show a dispersion of about 1 nsec/MHz over more than 120 MHz bandwidth, while bandpass filters exhibit 25 MHz bandwidth with less than 0.3 dB amplitude ripples.