Flat plate antennas have not yet been widely used in home satellite systems. There are two basic types: passive and active. The active flat plate is based on microcircuit design techniques. It is rarely seen in home satellite systems but is not uncommon in military and civilian radar systems were system cost is not a serious constraint. Passive flat plate antennas, like more common dishes, reflect or redirect satellite signals. A series of concentric rings overlaid onto a transparent sheet creates a lens that redirects or reflects and focuses signals. If these concentric rings are elongated into a set of ellipses, signals arriving from off- boresight locations can be focused to a point either in front of or behind the pattern.