Impedance tuning with photoconductors to 40 GHz

Abstract

Light is widely used to control a variety of microwave devices, including switches, antennas, and detectors. Here, the authors present a photoconductive device integrated into a coplanar waveguide to tune complex impedances at microwave frequencies with applied light. The authors measured the current–voltage characteristics of the device as a function of the applied light intensity and fit the behavior to a known metal-semiconductor-metal junction model with two Schottky barriers. The authors also measured the frequency-dependent scattering parameters and extracted the device impedances in a Pi-network model. The devices showed three orders of magnitude impedance tunability from 100 MHz to 40 GHz, and the authors developed a circuit model to fit the frequency-dependent impedances. This simple device has applications in microwave electronics, microwave metrology, and multi-state calibrations.