RF Characterization of Zero-Biased Photodiodes

The characteristics of zero-biased InGaAs p-i-n photodiodes were studied for use as optical transducers in an in situ phased array radar calibrator. Radio frequency (RF) operation is especially important for the intended application in which the zero-biased photodiodes drive patch antennas embedded in a radome. The photodiodes act as sources for real-time calibration of the phase and amplitude of each array element and will operate with only optical input from a modulated optical fiber link. Unfortunately, little is known of the RF performance of photodiodes operated without voltage bias. In this paper, both the dc and RF performance of a particular photodiode were studied to determine the optimum operating conditions and to understand the type and severity of any limitations.