| The intention of quasi-optical techniques is to develop high power sources at millimeter wavelengths. Quasi-optical grid array allows the output powers from large numbers of individual transistors and diodes to be combined in free space.In this dissertation, we briefly reviewed the recent developments and the numerical investigation in quasi-optical active grid arrays. Based on the configuration of quasi-optical grid arrays and basic 2-port circuit theory, the equivalent circuit model of grid oscillators was synthesized to satisfy the oscillation requirement, and completed negative-resistance grid model of the embedding circuit.A full-wave analysis of quasi-optical grid array is presented. The dissertation did work on two aspects as: first, it discussed the analysis of infinite periodic grid structures loaded with active devices using unit-cell approximation, an set of expressions were derived relating the radiated electric field to the surface current density on the metal grid, which was determined by the method of moments, and it also gave the method of driving point impedance calculation and the transmission coefficient for several passive grids; secondly, a full-wave moment method implementation, using a combination of spatial and spectral domains, was given for the analysis of finite quasi-optical grid array, the dyadic Green's function was derived for quasi-optical system, and analyzed the mutual-coupling effects on the driving point reflection coefficient, which existed between unit cells in the finite grid array. |
