Some Basic Characteristics of Broadband Negative Resistance Oscillator Circuits

With the advent of high-frequency negative resistance elements such as tunnel diodes, Gunn diodes, and IMPATT'S, it now appears practical, at microwave frequencies, to build negative resistance oscillators which perform various functions other than that of a fixed frequency oscillator. 1 Among the proposals recently made are variable frequency oscillators as FM deviators, and locked oscillators as FM amplifiers, limiters, and FM demodulators. 2-4 In the past, the analysis of these oscillators was primarily based on a simple model with a singleresonant circuit. 5-8 In practice, however, the designer of such a microwave circuit provides a number of tuning elements and adjusts them by trial and error until a desired bandwidth of locking or frequency deviation is obtained. During this adjustment, the designer observes numerous phenomena, including sudden changes in noise or oscillating frequency, as well as various hysteresis effects which could not be explained by the simple oscillator model. This paper presents a more realistic model of oscillators in which the load is separated from the active device by a multiple-resonant circuit. This gives us a better understanding of the oscillator behavior 1937