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Abstract

For the purpose of channel state estimation at the receiver end, a reference signal (f.sub.q (t)) is added to and is transmitted with the data signal (f.sub.i (t)) containing the actual information. The addition of the reference signal (f.sub.q (t)) to the data signal (f.sub.i (t)) is effected by means of a quadrature modulation with the reference signal on the Q-axis and with the data signal on the I-axis, the envelopes being selected so that the magnitude of the complex envelope is constant. The receiver has a function stage for preprocessing the receive signal, for quadrature detection of the data signal elements and reference signal elements (y.sub.i) and (b.sub.i) respectively, for selection of the data/reference signal and for estimating the channel state. This permits the operation of non-linear final stages of the transmitter and a maximum energy output from the transmitter, and the requirements of the short-wave transmission such as very low signal-to-noise ratio and signal interference ratio, fading, slightly drifting local oscillators and time bases, as well as high noise burst frequency are taken account of in an optimum manner. In addition the send signal has a narrow bandwidth and a low sensitivity to bit slip, which increases the connection probability and the robustness of the transmission.

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