A multiple silicon-avalanche diode oscillator

The combination of many synchronized devices has been proposed as a simple way of obtaining larger amounts of coherent output power. However, the synchronous operation of many microwave oscillators is not straightforward and requires practical solutions of several problems connected with phase locking, mode selection, noise, etc. The purpose of this paper is to identify the more important problems and their solution, and to present the experimental results obtained with a 6 GHz oscillator. Using eight Si-avalanche diodes in a resistive hybrid, power-combiner, 2/3 watt of CW power has been obtained with an efficiency of 3.5 percent without any external locking signal. The carrier-to-single sideband noise ratio is about 100 db per one cycle bandwidth at a frequency 1 MHz away from the carrier, which is slightly better than that of the best individual oscillator. The application of a synchronizing FM signal 10 db below the oscillator output can be used for a 0.1 percent frequency deviation, with a maximum deviation from linear phase of about one degree.