V-band Bull’s Eye Antenna for Multiple Discretely-Steerable Beams

We present a new approach to designing V-band Bull’s eye antenna so as to produce multiple beams, which are either fixed or discretely steerable. Bull’s eye antennas comprise concentric rings around a subwavelength aperture. Beam deflection is accomplished by adjusting the effective spacing of the rings, which we explain in terms of the coupling angle to free space and surface waves. We show that multiple beams can be obtained from a single antenna, with the deflection of each beam being controlled independently by the relevant portion of the ring pattern. We demonstrate the principle through rigorous full-wave simulations of two-beam antennas with symmetrical and asymmetrical shifts, and give experimental results for a prototype milled in aluminium, with two separate fixed beams each deflected 16° to either side of the broadside. We also propose means to obtain up to six different beam arrangements during operation by mechanically rotating a plate containing a special six-sector ring pattern. Our simulated example gives three patterns, a single broadside beam or two beams each deflected by 8° or 15°. The radiation efficiency of the antenna is 97%, and the gain of a single undeflected beam is 18.1dBi.