Duobinary signaling and decoding words
Before Viterbi decoding itself, the decoded signal should be processed to reconstruct the input of the decoder a duobinary sequence in which there is no violation of the duobinary coding rule that is to say no transition prohibitedeliminating all parts of the signal is not representative of actual broadcast messages. It is necessary that the decoding method provided in the reception can accommodate the second type format, which further complicates the problem. If it is odd, the received samples will be duobinary signaling and decoding words with burst burst inversion to avoid rape of the coding rule.
DE Free format text: Receiver and method for detecting and demodulating received signal subjected to dqpsk modulation and channel encoding. L'interface de sortie 82 peut avoir diverses constitutions.
Due to the presence of noise, we duobinary signaling and decoding words write the result of the samples obtained in reception, after passing through the support 16 of Figure 1, in the form: In addition, the clock signal is recovered at a frequency equal to The application of those rules requires that it be possible to determine the receiving location data introduced when coding the issue.
During the transmission of MAC image signal and during the alignment time, the data sequence applied to the input of the duobinary encoder is simply forced to zero. The duobinary signaling and decoding words N of cells is advantageously chosen so as to ensure an almost certain convergence of survivors. It is seen that the circuit shown in Figures 8a and 8b consisting of gates and flip-flops, is readily integratable, for example, C-MOS, possibly on gate arrays.
The constitution thus far described is conventional and, therefore, does not require detailed description. In the embodiment illustrated in Figure 2, this is achieved by interrupting the signal from the clock 20 applied to the Viterbi decoder after duobinary signaling and decoding words of the sample that corresponds to the "zero" level at the input of the decoder and up to sample, that is to say during periods of the clock signal at During the transmission of MAC image signal duobinary signaling and decoding words during the alignment time, the data sequence applied to the input of the duobinary encoder is simply forced to zero. The time window signal and the clock signal are also applied to a counter 52 which enables the generator 50 only during intervals not containing the sound signal and data.
During each of these lines: This comprises a duobinary signaling and decoding words flip-flop output 58 which provides a pulse each time it receives, on its D input, a signal indicating either of forbidden transitions. A method according to claim 1 or 2, characterised in that the decoding process is re-initialised before the beginning of each burst. The three inputs of the gates 60 and 62 receive: In the circuit 56, the signals from two flip-flops corresponding to the most significant bits are applied to two inputs of the violation detector