This invention relates generally to radio frequency antennas and more particularly to flush-mountable radio frequency antennas.
As is known in the art, it is frequently desirable to provide a radio frequency antenna which occupies minimum space and is essentially flush-mountable to a carrier vehicle, such as an aircraft. As is also known in the art, a radio frequency antenna which is adapted to provide a cardioid-shaped radiation pattern is useful in many applications, for example, where each one of a pair of antennas is mounted to an opposite side of such vehicle, thereby enabling such pair of antennas to be used in a "left/right" amplitude sensing system. While many antennas, such as annular slot and cavity-backed spiral antennas, may be flush-mounted to such a vehicle, such antennas do not produce the cardioid-shaped radiation patterns necessary for the "left/right" amplitude sensing systems, and while other antennas, such as a loop monopulse antenna, provide the cardioid-shaped radiation pattern, such antennas are not flush-mountable and also have relatively low gain.