Performance analysis of a microwave low-noise amplifier under laser illumination

Abstract

This paper analyzes in detail the performance changes of a GaAs HEMT-based low-noise amplifier under visible (650 nm) laser exposure. The device employed was first characterized in dark and illuminated conditions over the 2–18 GHz frequency range in terms of DC, scattering and noise parameters. Subsequently, it was modeled by means of a linear circuit model with associated noise sources in both conditions. By employing the experimental results, a low noise amplifier has then been designed and optimized for dark mode operation in the 7.5–8.5 GHz frequency range. Finally, the performance of the LNA under light exposure has been evaluated. On the basis of the device performance variations under VIS light exposure, we expected either a severe degradation of the noise figure, a slight increase of the amplifier gain and a moderate variation of the input/output matching. Instead, the obtained results exhibited a moderate degradation of the overall LNA performance due to device illumination, except for the input matching level which showed to be improved. We then analyzed the correlation between the device model variations and the amplifier behavior to get a deeper insight into the observed trends.