Experimental and Electromagnetic Modeling of Waveguide-Based Spatial Power Combining Systems

HICKS, CHRIS WAYNE. Experimental and Electromagnetic Modeling of WaveguideBased Spatial Power Combining Systems. (Under the direction of Michael B. Steer.) Recent technological advancements and demands for high power sources at microwave and millimeter-wave frequencies have initiated extensive theoretical and experimental research in the area of quasi-optical and spatial power combining. The work described here was motivated by the necessity to develop a modeling environment for the electromagnetic analysis of planar quasi-optical and spatial power combining systems, in order to understand physical fundamentals and provide a basis for the design process. Two types of planar quasi-optical (QO) and spatial power combining systems are investigated. Propagation in a QO parallel plate system is investigated with the aim of establishing the mode structure and characteristics of the modes. Theoretical electromagnetic properties of a Gauss-Hermite beammode expansion was developed, and verified experimentally, for the prediction of the resonant frequencies of the structure and beammodes dispersion behavior. The system was designed, fabricated, tested, and showed good agreement between the experimental and theoretical results. In addition, a QO parallel-plate stripline-slot amplifier system was designed, tested and compared to a QO open HDSBW amplifier system with Vivaldi-type antennas. Experimental results verify that a QO parallel-plate stripline-slot amplifier proposed in this dissertation can be modeled using Gauss-Hermite beammodes. A full-wave electromagnetic model is developed and verified for a spatial power combining system consisting of slotted rectangular waveguides coupled to a strip line. The waveguide-based structure represents a portion of the planar QO power combiner discussed above. The electromagnetic simulator is developed to analyze the stripline-to-slot transitions in a waveguide-based environment. The simulator is based on the method of moments (MoM) technique to model a power combining array of slotted waveguide modules coupled to a strip line. The simulator uses Galerkin projection technique with piecewise sinusodial testing and basis functions in the electric and magnetic surface current density expansions. Electric and magnetic dyadic Green’s functions are developed for an infinite rectangular waveguide in the form of partial expansions over the complete system of eigenfunctions of a transverse Laplacian operator. Numerical results are obtained and compared with a commercial microwave simulator for a few representative slot-strip-slot spatial power combining transitions and arrays.