Abstract: An antenna is described. The antenna includes a planar circular structure. The antenna also includes a radiating element located at the center of the planar circular structure. The antenna further includes one or more parasitic elements located on a contour around the radiating element. The parasitic elements are aligned in parallel direction with the radiating element. The parasitic elements protrude from the planar circular structure. The antenna includes switches separating each of the one or more parasitic elements from ground. A switch in a first position creates a short between a parasitic element and ground. A switch in a second position creates an open circuit between the parasitic element and ground.

Abstract: An antenna assembly (30) for a communication device (20) includes a feed structure (25), which has front and rear sides (26, 27), and which is coupled to be driven by the device so as to radiate an electromagnetic field in a given frequency band. An electrically reactive surface (28) is positioned adjacent to the rear side of the feed structure so as to define a cavity (35) between the feed structure and the reactive surface, thereby substantially nulling the electromagnetic field on the rear side of the feed structure.

Abstract: A radiation shield (36) includes a virtual magnetic wall (VMW), which is adapted to be placed between a radiating antenna (34) and an object (30) so as to reflect electromagnetic radiation emitted from the antenna in a given frequency band and having an electric field with a given polarization, away from the object. The electric field of the radiation reflected by the VMW is substantially in phase with the electric field of the emitted radiation incident on the VMW.

Abstract: A slotted waveguide array antenna includes a plurality of waveguide elements extending in a parallel side-by-side relation, each having a radiating side including a broad wall formed with a plurality of slots, and an asymmetric ridge. The slots are slanted to the longitudinal axis of the antenna in alternating directions and are spaced .lambda.g/2 apart such as to offset phase reversal between each pair of adjacent slots.