Hyperselective limiter

An anti-interference device using magnetic resonance has been studied both theoretically and experimentally. This device is basically a frequency selective limiter; that is, it can independently limit input spectral components without causing significant cross-modulation. Frequency selective limiting is also observed in the ferrite limiter, but occurs only if spectral components are spaced by at least a few megacycles. A much higher degree of selectivity has been obtained at these laboratories in a limiter using proton magnetic resonance. An experimental model operating at 30 Mc has provided independent limiting of two signals separated by as little as 5 cps. Such a high degree of selectivity makes possible the suppression of many types of interference which appear within a communication channel without degrading signal intelligence. Principles of operation will be discussed and experimental results will be presented.