A low-cost differential radiometer that detects the human microwave emissions

In the last few years, implementations of low cost teaching radiometers suitable for the demonstration of the human microwave electromagnetic field emission were described. They use, as reception front-end, a Low Noise Block. This component, however, has a great gain instability in relation to the environmental temperature and the characteristics of the detector that is employed in the next stage are temperature dependent. Furthermore, the back wall intercepted by the antenna beam has, during the day, a high temperature variation, much greater than the temperature difference between the target and the back wall. For these reasons, in a single-receiver system the offset circuit requires frequent adjustments. This disadvantage can be eliminated by providing for a differential configuration of the system, as described in this article.