Analysis and design for quasi-optical structures

Citation

Preventza, Polly (1999) Analysis and design for quasi-optical structures. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/t7ve-td81. https://resolver.caltech.edu/CaltechETD:etd-02242008-093525

Abstract

Quasi-optical power combiners such as quasi-optical grids provide an efficient means of combining the output power of many solid-state devices in free space. Unlike traditional power combiners no transmission lines are used, therefore, high output powers with less loss can be achieved at higher frequencies. This thesis will detail three quasi-optical grids and their modeling. Two new models for analyzing quasi-optical grid amplifiers based on a finite-element simulator (HFSS) are presented and their validity is tested. A 36-element Ka-band grid amplifier is also described. The grid uses Flip-Chip InP HEMT's and has a peak gain of 4.8 dB at 36 GHz. A beam-steering method which includes microelectromechanical (MEM) switches on an insulating membrane is presented. The arrays are fabricated monolithically on highly- doped silicon by Rockwell Science Center. Processing challenges in fabricating the structures will be discussed. Measurements of s-parameters of capacitive arrays (Off state) are made and give promising results for the beam-steering grid. The design, construction and performance of a 36-element hybrid gid oscillator is also presented. The active devices are InP-based HEMT's. A locked frequency spectrum was achieved, with a Peak Effective Radiated Power (ERP) of 200 mW at 43 GHz. The grid is designed to minimize the substrate-mode power and produce an E-field with low side-lobes.

Thesis Files