Optically Controlled Photoconductive N-Bit Switched Microwave Signal Attenuator

An optical architecture for N-bit digital control of microwave signals is introduced that uses the photoconductive effect in microwave waveguides for variable rf attenuation control. A 2-bit optically controlled microwave attenuator based on a transmission line fabricated on a silicon photoconductive substrate is experimentally demonstrated at 990 MHz. This attenuator provided 0, 5.8, 11.2, and 15.6 dB of independent optically switched attenuation levels. © 1995 IEE