Abstract
The primary aim of the work described in this thesis has been to examine the general characteristics of microwave semiconductor oscillators with non sinusoidal waveforms and, in particular, to study the conditions for stability of such oscillators. Single and multiresonant circuits are considered experimentally with the L. S. A. mode being the main point of interest. It is clear from the results that the dependence of the diode power and conductance upon the fundamental voltage amplitude for a multiresonant circuit is quite different compared with a pure sinusoidal oscillator in a single resonant circuit. Similar results are obtained using the describing function technique which proves to be very useful in the analysis and synthesis of circuits for optimum properties of the system. The study on stability allowing for the presence of harmonic components has led to a generalization of the Kurokawa conditions. The new criteria are more restrictive than the condition of stability for pure sinusoidal oscillators. The describing function technique provides the necessary data to plot the device line and circuit admittance loci and a graphical interpretation of the stability conditions at each frequency component is presented.