United States of America As Represented by the Secretary of the Air Force

Walter Rotman

Peter R Franchi

Nicholas V Karas

Ronald L Fante

J Leon Poirier

The bandwidth limitation in space fed phased arrays (that results from the use of phase shifters to implement beam steering) is overcome by a lens arrangement in which independent feeds are provided at the focal plane of the lens. Each feed generates a collimated beam in a different spatial direction. Each beam can then be steered about its central position by means of phase shifters, while retaining a substantially improved bandwidth. An algorithm is derived for designing three-dimensional (3D) microwave lenses with line source feeds by stacking a number of identical two-dimensional (2D) parallel-plate, wide-angle constrained lenses into a cylindrical antenna structure. This lens design provides focused beams over a wide range of scan angles in both elevation and azimuth with only small optical aberration. A wide variety of lens designs can be achieved through this algorithm, dependent upon the constraints which are selected for the 2D lens counterpart. For one design, where all the transmission line lengths in the lens are made equal, the phase errors for beam scanning in the plane containing the cylindrical axis of the antenna are less than their broadside values, regardless of scan angle. This permits wide-angle coverage in both elevation and azimuth from a single lens with both good beam and quality and bandwidth.

Cylindrical microwave lens antenna for wideband scanning applications

An intrusion detection system utilizes a radio frequency radiative system whose near electromagnetic field is monitored by receiving devices which respond, in a measurable way, to any disturbance of the near electromagnetic field by physical intrusion.

Intrusion detection system

An RF intruder system utilizes two concentric loops of wire spaced apart for a predetermined magnitude, either of which can transmit and/or receive electromagnetic energy. This area within the loops are to be protected against intrusion. Without intrusion, the received signal is steady. Upon intrusion, there are signal changes which are instantly noted by signal detection and processing.

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Brighton, MA, United States of America

Walter Rotman