A Diplex, Doppler Phase Comparison Radar

A simple method of obtaining range and velocity information has long been sought for numerous applications.1One such application concerns itself with detecting the presence of an obstacle in the path of a moving vehicle, the distance to it, and the rate of closure. Since the ranging capabilities of such a system must include an approach to zero distance and extend to several hundred feet, most conventional radar systems can be dismissed as impractically complex and/or requiring large radio frequency bandwidths. A new and simple radar is presented for ranging to a moving target at close distances. Intended for a range interval of from zero to five hundred feet, the practice of operation may be extended to several times that distance; or, on the other hand, very close ranges (on the order of inches) may be measured. An important feature is this system's ability to distinguish a single moving target among a multitude of stationary ones and to correctly indicate the direction of motion-approaching or receding. The target's speed may be determined directly from its Doppler frequency. Extremely simple RF "front-end" and detector circuits, and unusually narrow bandwidths utilized by the solid state receiver, are salient features of a portable system which has been built to operate from an automobile battery.