Amplitude and Phase Control of an RF Signal Using Liquid-Crystals by Optoelectronic Method

摘要

An optoelectronic technique to control both the amplitude and phase of a radio frequency (RF) signal is presented that uses two electrically controllable birefringence mode nematic liquid-crystal spatial light modulators (ECB mode nematic LC-SLMs). An experimental circuit was built and its performance was examined. The intensity could be changed down to -25 dB, and a phase shift of up to 240 degrees was achieved, by changing LC-SLM supplied voltages. Carrier-to-noise ratio (CNR) and intermodulation characteristics of an RF signal were measured. It was, for the first time, found that CNR was not degraded by the amplitude control and phase shift performed by the LC-SLMs.