A high efficiency splashplate feed for small reflector antennas

Three alternative polyrod type feeds are investigated with a view to solving the problem of nulls in the gain of small (typically 10 wavelengths) reflector antennas with the splashplate feed. A polyrod-fed Cassegrain system is used as a first attempt to suppress the nulls; a hybrid solution is then considered where the polyrod is embedded within a splashplate. Finally, an optimum solution is suggested which combines the features of the previous two. Also, a novel design is proposed in which a polarizer is incorporated into the polyrod.