Steven N. Stitzer

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.

Frequency selective microwave power limiting in thin YIG films

This paper develops a model of frequency selective microwave power limiting in a microstrip transmission line coupled continuously to a magnetic insulator. Calculated selectivity bandwidth is compared to that experimentally measured in a 57 micron YIG film. Selectivity bandwidth is approximately ±20 MHz for 3 dB compression of weak signals in S-band. The effect of linear absorption in the microstrip is included in the analysis.

Nonlinear microwave signal-processing devices using thin ferrimagnetic films

The signal-processing characteristics of signal-to-noise enhancers and frequency-selective limiters are described. Performance of several practical devices is discussed. The theory of below-threshold operation is reviewed. New theoretical results are presented for calculation of threshold power and above-threshold power loss. Frequency selectivity and the consequences of linear losses are calculated for the limiter.