Broad band ferromagnetic subsidiary resonance limiters for duplexer applications

This paper describes the results of a program to develop broad band ferromagnetic resonance limiters for duplexer applications. The major advantage of the subsidiary resonance limiter is the broad frequency bandwidth that can be achieved. The major disadvantage is the relatively high limiting threshold power level and low dynamic range. Methods of reducing the limiting threshold power to practical values of less than 1 watt peak and of increasing the dynamic range are described. The theory of subsidiary limiting is considered, and an analysis is made to determine feasible operational characteristics of the limiter, using the results of new material development programs. Experimental data on state-of-the-art devices are presented. Dynamic ranges greater than 50 db and bandwidths in excess of 12% have been achieved at X-band frequencies. The minimum threshold limiting power is less than 1 watt peak; the insertion loss of the device is less than 0.8 over the frequency range.