Simulation study of harmonic oscillators

The harmonic behavior of GaAs Gunn oscillators of the cap type has been studied by Eddison and Brookbanks (1981) and Haydl (1981). It is now known that efficient second-harmonic generation is feasible in the frequency range up to 110 GHz using GaAs Gunn elements. The present investigation compares the fundamental circuit behavior of a negative resistance element operated in the fundamental mode with aspects of second-harmonic mode operation. It is found that the harmonic oscillator output power increases with the degree of unsymmetry of the I-V characteristic for the active element. The value of the source impedance of the harmonic oscillator is one half of the corresponding value for the fundamental oscillator. The obtained theoretical results confirm the observations made in connection with the empirical development of harmonic oscillators using Gunn elements as the active device.