Overview of applications of optical measurements in microwave circuit and antenna array design

An overview of both photoconductive sampling and optoelectronic mapping measurements (developed at the University of Michigan by the Whitaker and Katehi group) and their benefit in expediting microwave circuit and array design is presented. In particular, photoconductively sampled time-domain waveforms of switched-mode nonlinear power amplifiers and X-band and high-efficiency multipliers at C-band will be discussed. The high-impedance optical sampling probe enables measurements of waveforms within a microwave circuit. This in turn enables us to validate designs of nontraditional nonlinear circuits, as well as to diagnose problems associated with improperly terminated harmonics, leading to new improved circuit designs. We also present near-field measurements using an electro-optic crystal probe. As an example, a 30 GHz (Ka-band) active amplifier antenna array power combiner is examined in detail. The effects of mutual coupling between array elements, and bias line influence on RF mutual coupling between elements are presented. An extensive list of references that contain more details of the overviewed material is also given.