Abstract: A digital signal is interleaved by delaying samples thereof by an integral number times a unit delay in accordance with a cyclically repeated delay pattern (AL91) . . . AL(M) Select lines (AL91) . . . AL(M)) of a memory (HAS) are cyclically activated (HAS) at a cycle rate equal to unit delay. During the activation of a select line, both data is written and read from the memory. The data written comprises a relevant bit of each sample to be delayed in an integral number of sample groups. Each sample group is associated with one delay pattern cycle. The data read (b(1,1,j)@a1 . . . b(1,M,j)@aM . . . b(k,1,j)@a1 . . . b(k,M,j)@aM) comprises a number of bits which is equal to the number of bits written. The bits are read in accordance with the delay pattern. Accordingly, the speed requirements imposed on the memory (MEM) are relatively lax.

Abstract: A DAB receiver in which a reduced time de-interleaving memory for storing metrics is used, but which still allows processing of DAB services which normally would exceed the storage capacity of the memory. This is achieved by varying the length of a stored metric, depending upon the storage capacity required, by varying the number of stored reliability bits in a metric. In this way, a trade-off can be made between storage capacity and processing quality.

Abstract: In a digital audio broadcast receiver a digital audio transmission signal is supplied to a demodulator which provides demodulation samples. The demodulation samples are de-interleaved in a first section of a de-interleaving memory. After having been de-interleaved, demodulation samples are transferred to a second section of the de-interleaving memory. This transfer is effectuated in bursts via a relatively small buffer which stores the bursts. The second section of the de-interleaving memory effectively constitutes a relatively large buffer. De-interleaved demodulations samples are regularly read from the second section and supplied as a regular stream to a Viterbi decoder by means of a relatively small first-in first-out register.

Abstract: An echo canceller for use in send/receive apparatus includes a frequency-domain adaptive filter which provides filter parameters to a time-domain programmable filter. The programmable filter produces a signal y(k) which is an estimate of the echo signal produced by acoustic coupling between a loudspeaker in the received path and a microphone in the send path. By subtracting this estimate from the signal produced in the send path, an output signal r(k) is obtained from the send path which is essentially free of echoes. An accurate estimate of the echo signal cannot be obtained if a send signal is present at the input of the send path. Therefore, detecting means in the adaptive filter detects whether such a send signal is present and in that case blocks the transfer of filter parameters from the adaptive filter to the programmable filter. Erroneous modification of the estimated echo signal is thereby avoided.

Abstract: A digital echo canceller has a receive path (2) and a send path (3) and comprises combining apparatus (10) for forming a send output signal [r(k)] as the difference between the signal [z(k)] applied to the send input (SI) and a replica signal [e(t)] used for cancelling an additive echo signal [e(k)] at the send input (SI) that has developed in response to a receive input signal [x(k)] applied to the receive input (RI), which echo canceller at least includes transforming apparatus (13, 15) for transforming the receive input signal [x(k)] and the send output signal [r(k)]; transforming apparatus (14) for transforming the replica signal [e(k)]; a digital adaptive filter (9) which has a number of filter coefficients for generating the replica signal [e(t)] in response to the receive input signal [x(k)] and the send output signal [r(k)], adaptation apparatus (12) for determining for each block m, adaptation components [A(p;m)] for each of the filter coefficients [W(p;m)] in response to the receive input signal [x(

Abstract: A digital echo canceller [1] with a good protection against double-talk comprises a first filter [9] for the echo cancellation proper, a second adaptive filter [11] for making continuously adapted filter coefficients available to the first filter [9] and gate means [15] which will only apply the adapted filter coefficients to the first filter [9] if certain conditions are satisfied. In the echo canceller [1] a specific filter combination is used, in which the first filter [9] is a time-domain programmable filter (TDPF) and the second filter [11] is a frequency-domain block-adaptive (FDAF), and further means [20,20(1)] are provided that are arranged in cascade with the gate means [15] for transforming the frequency-domain filter coefficients [W(p;m)] of the FDAF [11] into time-domain filter coefficients [w(i;m)] for the TDPF [9].