AFC for Frequency Hopping Systems

An AFC system has been developed for stabilizing the frequency of a voltage-tunable oscillator near any one of many discrete frequencies. A delay line takes the place of the conventional cavity in the discriminator. The discrete steps correspond to the electrical length of the delay line, e.g., 2 Mc in the S-band system reported herein. Slow frequency fluctuations inherent in the oscillator are reduced; a stabilization factor of 100 has been achieved in a system for jumping frequency rapidly by stepping the tuning voltage. The nature of the hysteresis loops and means for their reduction are discussed. The system is significant for improving the stability and the spectrum of wide-band tunable oscillators as used in frequency hopping apparatus.