Response of long-wave MCT detectors to microwaves

Infrared sensors are being incorporated in more systems and are often placed close to radar systems. The IR sensor is thus subjected to various microwave levels from the sidelobes or reflections of the radar pulses. In this paper we address the effect of microwaves on the performance of mercury-cadmium-telluride longwave photodiodes. We examine the effects of microwaves entering directly through the optical window (front-door mechanism) and entering along wires connected to the dewar (back-door mechanism). The diode noise voltage was measured before, during, and after the microwaves pulses by transimpedance amplification. The diode noise characteristics were shown to respond very rapidly to the microwave pulse. A linear relationship between detector noise and microwave power was observed. A strong dependence of noise on microwave frequency was observed and attributed to the resonances of the dewar design.