Quasi-Gregory Antenna for Subnanosecond Impulse Radiation

A quasi-Gregory antenna was designed for subnanosecond impulse radiation. It consists of an ellipsoidal feed, a mirror plane, and a paraboloidal reflector. The second focal point (F2) of the ellipsoidal dish can be regarded as the radiation center of the feed because electromagnetic waves launched from the first focal point of the ellipsoidal dish (F1) are in phase when arriving at point F2, according to geometric optics. The equivalent radiation angle at point F2is a spherical sector; therefore, it can be designed to geometrically cover the paraboloidal reflector precisely. Gaussian pulses with widths of 200 and 330 ps are used to test the performance of this proposed impulse-radiating antenna (IRA). The 3-dB beamwidth of this proposed IRA with a 1.5 m aperture diameter for the paraboloidal reflector is less than ±3° in the H-plane and less than ±5° in the E-plane. Compared to some existing IRAs, this quasi-Gregory antenna is also suitable for radiating pulses in the subnanosecond regime.