Siemens Aktiengesellschaft

Heinrich Sailer

Gero H Schollmeier

Helmut Koeth

For the compensation of echo signals occuring in the course of the duplex transmission of digital signals by the dual channel system in signal transmission equipment provided with an echo compensator, the equipment is designed so that the clock pulses emitted by a timing generator for the transmission of the digital signals can be shifted in phase by predetermined phase grid steps. When a change in the phase position of the clock pulses takes place within one phase grid step, correction signals are generated, with the phase position that has been accurately set in each case being maintained. These correction signals are subtracted, together with the compensation signals emitted by the echo compensator for the compensation of the echo signals, from the digital signals received together with the echo signals.

Method and circuit arrangement for the compensation of echo signals

A circuit arrangement is disclosed for the summation of products formed from analog signals and digital coefficients. A multiplying digital-analog converter is provided having a reference input for receiving analog signals at successive points in time. A data input of the digital-analog converter receives digital coefficients assigned to the respective analog signals. A summation stage connected to output signals of the digital-analog converter integrates over a predetermined time period the output signals of the digital-analog converter representative of products of the analog signals and digital coefficients.

Circuit arrangement for the summation of products formed by analog

Apparatus for controlling the phase of a clock signal in a data transmission system is described. In the latter system the data signal is pulse amplitude modulated, routed to a receiver-demodulator over a transmission path, the data signal retrieved by means of a sampling circuit and coupled to a data sink. A difference signal is produced from the demodulated and the data signals; the amplitudes of the difference signal characterize the amplitude differences between the demodulated and the data signals at predetermined sampling instants. Using the demodulated signal a slope signal, which is indicative of the slope of the demodulated signal at the sampling instants is produced. The difference and slope signals are multiplied producing a product signal having amplitudes equal to the product of the latter two signals. The product signal forms a control signal for altering the phase of the clock signal by adding to or suppressing pulses emitted from a frequency divider.

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Munich, Germany

Heinrich Sailer