High resolution ultrasonic distance measurement in air using coded signals

This paper gives a survey of problems of ultrasonic distance measurement systems with regard to applicability in industrial environment as well as for presence detection and also for high resolution measurement tasks. The impulse compression method is able to handle the mentioned problems. To simplify the real time signals processing a one bit correlation technique is introduced. Next, the comparison between A-B-measurement and use of passive reflection leads to a new method of active reflection in ultrasonic systems which combines the advantages of both methods. The active and passive reflection is compared and their common and different aspects are shown. In the following the radiation pattern of an ultrasonic transducer is analyzed and its influence on broadband signal emission and reception in conjunction with correlation based receivers is discussed. A prototype of an active reflection system is presented and its final configuration is shown.