MSW frequency selective limiters at UHF

Frequency selective limiters (FSLs) have potential application in maintaining the dynamic range of RF receivers in the presence of interference. Stripline FSLs, fabricated using thick YIG films, have been described previously and are suitable for broadband, microwave applications. Here a magnetostatic wave (MSW) FSL operating in the 400 MHz to 800 MHz frequency range is described with frequency selectivity and threshold power levels 100 times lower than achieved with stripline devices. Y/sub 3/Fe/sub (5-x-y)/Ga/sub x/Sc/sub y/O/sub 12/ (ScGaYIG) films with reduced 4/spl pi/M and anisotropy field were grown by LPE and characterized for /spl Delta/H, /spl Delta/H/sub k/ and 4/spl pi/M Devices were characterized for insertion loss, threshold power level, limiting, frequency selectivity and intermodulation products. FSLs in UHF through S-band (400 MHz to 4 GHz) are feasible with present YIG and ScGaYIG materials. Threshold power levels <20 dBm, narrow selectivity bandwidth <2 MHz and low intermod levels have been demonstrated.

I. Introduction

Frequency SELECTIVE LIMITERS (FSLs) are nonlinear devices that attenuate large radio frequency signals while allowing small signals at different frequencies to pass with little change. FSLs have potential application in maintaining the dynamic range of receivers in the presence of interference. Frequency selective limiting is a unique feature of ferrite devices and arises from the nonlinear interaction of the spin precession at the signal frequency, , with spin waves at half of the signal frequency, . Stripline FSLs, fabricated using thick YIG films, have been described previously [1] and are suitable for broadband, microwave applications. Here a FSL operating in the 400 MHz to 800 MHz frequency range is described with frequency selectivity and threshold power levels 100 times lower than achieved with stripline devices. Signal-to-noise-enhancers using a pair of MSW FSLs have been demonstrated [2] for noise reduction in DBS TV receivers and a similar MSW FSL configuration was used here.