A figure of merit for signal processing reflector antennas

Abstract

In recent years a new class of reflector antennas utilizing array feeds has been receiving attention. An example of this type of antenna is a reflector utilizing a moveable array feed for beam steering. Due to the circuitry required to adjust the weights for the various feed array elements, an appreciable amount of loss can be introduced into the antenna system. One technique to overcome this possible deficiency is to place low noise amplifiers with sufficient gain to overcome the weighting function losses just after each of the feed elements. In the evaluation of signal processing antennas that employ amplifiers the standard antenna gain measurement will not be indicative of the antenna system's performance. In fact, by making only a signal measurement, the antenna gain can be made any arbitrary value by changing the gains of the amplifiers used. In addition, the IEEE Standard Test Procedures for Antennas does not cover the class of antennas where the amplifier becomes part of the antenna system. There exists a need to establish a standard of merit or worth for multi-element antenna systems that involve the use of amplifiers. A proposed figure of merit for evaluating such antenna systems is presented.