Radiation fields of open-cavity radiators and a backfire antenna

The radiation fields of an open-cavity radiator are studied theoretically and experimentally. This antenna consists of a simple open-ended circular cavity with a primary radiator, which includes a dipole, a dipole array, a terminated transmission line, and a loop, placed at an appropriate location inside the cavity. For the case of the dipole array exciter, because of the presence of a parasitic reflector in front of the dipole element, the open-cavity radiator radiates like a short backfire antenna.