High-efficiency operation of a Gunn oscillator in the domain mode

An examination of the problem of obtaining high-efficiency operation of a Gunn oscillator is given in this paper. The results are based on an assumed form of I-V characteristic of the Gunn diode, the ideal voltage and current waveforms being found for high-efficiency operation. The theory for a square wave of current through and voltage across the diode is worked out in detail and shown to predict the experimental results well. It is shown that a voltage waveform consisting of only a fundamental and second harmonic component could give efficiencies in the 20-28 percent range, as much as a factor of 3 larger than for a simple sinusoid. This is a reasonable approximation to the ideal voltage waveform, which is a half sinusoid of voltage. In this paper the charge and discharge time of the domain is neglected. An estimate of these times is given in the Appendix, and it is shown that the efficiency theory should be relevant to operation with diodes for which
nL \gg 10^{12}
cm
^-2
. The theory may also describe certain types of "LSA mode" operation.