Abstract: The influence of a DC offset with a carrier-frequency offset at the same time is reduced in that the values of the assumed or determined DC offset and of the assumed or determined carrier-frequency offset are included in the determination of reliability information for one sub-carrier in the multicarrier system, and the reliability information is corrected in this way. A factor M, where M<1, is defined for each sub-carrier on the basis of the values for the DC offset and for the carrier-frequency offset, and the reliability information for the sub-carriers is multiplied by these factors M.

Abstract: Distortions of radio signals transmitted in data blocks in an OFDM method, the distortions being caused by IQ asymmetries, can be estimated and subsequently equalized by means of specific reference data symbols which are transmitted at the transmitter end and may be part of a preamble. The method can be used particularly advantageously in a direct-mixing receiver.

Abstract: The influence of a DC offset with a carrier-frequency offset at the same time is reduced in that the values of the assumed or determined DC offset and of the assumed or determined carrier-frequency offset are included in the determination of reliability information for one sub-carrier in the multicarrier system, and the reliability information is corrected in this way. A factor M, where M<1, is defined for each sub-carrier on the basis of the values for the DC offset and for the carrier-frequency offset, and the reliability information for the sub-carriers is multiplied by these factors M.

Abstract: A method for demodulating a carrier wave that is modulated using a digital symbol sequence and that is transmitted over a noise-impacted channel, the ideal edge shapes of possible transitions between two symbols being known and stored in memory as reference edges, and a received edge being scanned and digitalized using a scanning frequency that is a multiple of the frequency of the symbol sequence. In particular, for detecting a received and scanned edge, all scanning values are used for calculating Euclidean distances from at least two reference edges, and the reference edge associated with the lowest Euclidean distance is selected. A Viterbi algorithm is applied to a sequence of estimated edges (rather than to an estimated symbol sequence) and the specific Euclidean distances between the edge received in one symbol period and the reference edges are considered as the costs of one trellis branch of the Viterbi algorithm.

Abstract: To provide an approach to correction of residual errors in subband-based transmission schemes there is provided a channel error correction apparatus with a first synthesis unit for synthesizing a preliminary output signal from subband signals received via a transmission channel. A subband correcting is achieved through a subband reanalysis unit analyzing the preliminary output signal through subband filtering without downsampling, an error estimation unit estimating errors in subband reanalysis output signals using subband specific error patterns, and an error compensation unit correcting the subband signals using error estimation results. A second synthesis unit then synthesizes a final output signal from output signals of the error compensation unit.

Abstract: In a method for demodulation of multistage-modulated data, correspondence variables (decision variables) are determined from the comparison of the received signal with stored signals, and these correspondence variables are converted into a posteriori symbol probabilities. The received signal represents a symbol which in turn represents a data group. The a posteriori symbol probabilities are now accounted for in turn such that one individual probability information item is produced for each bit of a data group, which information indicates the probability of a relevant bit being +1. Reliability values are determined from these bit-specific probabilities, and these reliability values are output, together with the bits, as soft bits.

Abstract: For compensation of the effects of multi-path reception, a cascade distortion corrector composed of distortion corrector blocks successively connected in series is provided for a digital FM demodulator that needs non-recursive filtering. Each distortion corrector block produces an increase of the phase rotation and of the propagation time as well as a reduction of the reflection factor of the input signal. The cascade distortion corrector leads to a significant reduction of the hardware expense compared to the previously used transversal type filter structures. Sufficient compensation of the multi-path reception effects can be obtained by connecting five or six distortion corrector blocks one after the other.

Abstract: Multi-phase/multi-level modulation data signals recorded on tape after conversion from original digital data are first converted to complex digital signals in an analog-to-digital converter in which the sampling rate is set by a pulse generator frequency controlled by the received signals through a control loop which develops a frequency control voltage (A). The complex digital signals have their real and imaginary parts separately filtered by filters of variable propagation time, but of constant bandwidth to produce complex signals to which the nearest permissible output complex signal (reference signal) is selected by a decision circuit (17), for final conversion to binary signals by a decoder (19) and a shift register (20). Timing shift correction is based on comparison of the received signals and reference signals of the decision stage to produce a control signal (.phi.

Abstract: FM Signals are demodulated on an entirely digital basis by converting the digitalized signal into a pair of signals which are substantially Hilbert transforms of each other. This requires at least one pair of nonrecursive filters having lower signal sample rates at the output than at the input. Each signal is delayed by one output sample interval, so that cross products of the delayed and undelayed Hilbert transforms can be formed, and the difference between them obtained. Finally, an arc-sine table is used to remove sine-function distortion. A single multiplier-accumulator provided with extra registers can perform all of the necessary arithmetical operations at the speeds required.