THE BACKFIRE ANTENNA, A NEW TYPE OF DIRECTIONAL LINE SOURCE

Abstract : A description is given of the backfire antenna, a new type surface- wave radiator which consists of an ordinary endfire structure (Yagi, dielectric rod, and so forth) terminated by a plane reflector. The surface wave launched at the feed travels along the endfire structure until it impinges on the reflector; it then travels back toward the feed and radiates into space in a direction opposite to that of normal endfire operation. The gain of the backfire antenna is between 4 and 6 db higher than that of an ordinary endfire antenna of the same length; conversely, to achieve the same gain, the backfire antenna needs to be only between 1/4 to 1/3 as long as the ordinary endfire antenna. The side and back lobes can be kept extremely low. The backfire antenna will have wide application in cases in which the transverse dimension of the reflector does not violate ringe low-silhouette requirement .