A variable beamwidth millimetric wave antenna

A preliminary investigation of a millimeter wavelength antenna based upon the optical zoom lens system is presented. The antenna consists of an axial lens system of four elements and possesses a beamwidth that can be continuously varied over a range of 7.7 to 1 at 140 Gc and 5.3 to 1 to 70 Gc by the proper axial motion of its lens elements. An analysis based upon both visible and microwave optics is presented which provides approximate expressions for the beamwidth and gain variations in terms of the positions of the lenses of the system.