<p>An antenna comprising: (a) a pair of spaced apart conducting plates which are separated by a cavity containing a dielectric medium; (b) radio frequency feed means for coupling radio frequency energy into, or from, the cavity formed by the conducting plates; (c) generating means for forming a pattern of conducting elements between surfaces of the conducting plates and thereby to focus an electromagnetic wave front towards an edge of the cavity; (d) control means for influencing the pattern of conducting elements and thereby to direct or otherwise influence the electromagnetic wave front; and (e) redirecting means for redirecting the electromagnetic wave front to illuminate an associated radiating means.</p>
