Abstract
The aim of the work described in this thesis was to examine the starting characteristics of Trapatt (Trapped Plasma Avalanche Triggered Transit) oscillators capable of producing high (peak) power at high efficiencies, normally in L and S bands. General approach was aimed to be mainly experimental using deep diffused silicon devices suitable for operation in S band. To perform the experiments an oscillator circuit, in 7 mm coaxial line was constructed, suitable for using a device in S-4 package. The overall arrangement of the experimental setup was similar to one described by various other researchers for observing the dynamic current and voltage waveforms. The C-V profiling experiment produced a characteristic which suggested that the depletion layer capacitance of the device does not really saturate for increasing voltage even upto its breakdown voltage. A detailed analysis of the C-V plot and related features was carried out and it was concluded that the actual doping distribution appears to be favouring a graded junction. Experimentally it was established that the device has negative resistance at VHF and also at d.c. It has also been shown that the device has small signal negative resistance at the operating frequency of the oscillator. Detailed investigations into the starting characteristics indicated that the oscillations start from the beginning at the final fundamental frequency of the oscillator. For the device and the circuit reported in this thesis no evidence could be found to suggest that Impatt type oscillations trigger the Trapatt oscillations. As a result of our experiments it has been possible to establish that the rate of growth and the time taken for the oscillations to start depend upon the d.c.drive. There are strong indications that in future Trapatt devices could successfully be employed in various systems as a microwave generator.