Switched parasitic feeds for parabolic antenna angle diversity

The radiation direction from a parabolic dish antenna can be electronically controlled through the use of a switched parasitic element closely coupled to a dipole feed. Through the application of a dc voltage, the half‐wavelength‐long parasitic element is switched between open and short circuit using a p‐i‐n diode at its center. With a parasitic element vertically offset from the horizontal dipole, the performance of the antenna in both switch positions has been optimized. At 1.5 GHz, using a 2.4 m diameter reflector, beam skewing on the order of 1.5° at the −6 dB point can be achieved for a feed element spacing of 0.6 wavelengths. At a parasitic element spacing of 0.5 wavelengths, the main lobe is better than 15 dB above the unshifted null. The analysis of such a structure requires the calculation of the current in both the driven element and the parasitic element and the summation of their fields on the surface of the reflector independently.Griffith Sciences, Griffith School of EngineeringNo Full Tex