Rupp, J.J.RuppHeidmann, D.D.HeidmannSchmitt, R.R.SchmittBresser, B.B.Bresser2022-03-082022-03-081997https://publica.fraunhofer.de/handle/publica/303819The encapsulated transmitter combines a fundamental-frequency oscillator (1) with a pulse sequence generator (2) and a pulse phase encoder (3) which may generate Barker codes or pseudonoise or m-sequences. The fundamental frequency (f0) is modulated (4) with the code for the driver (5) of the ultrasonic emitter (6). The receiver (11) feeds a preamplifier (12) and mixer (13) with quadrature channels in which a low-pass filter and digitiser are followed by a digital correlator (DK) using a stored sequence of transmission pulses as a reference. USE - Particularly for investigation of intestinal activity, the transmitter can be made smaller and less susceptible to noise, without loss of accuracy of its location.de608610620patent1996-19609564