| 摘要 |
The invention relates to a method and an arrangement for controlling the frequency of a radio-receiver which receives signal-sequencies which have been subjected to interference and which include a synchronizing-sequence and a data-sequence. A signal-sequence is A/D-converted (3) to signal-points (I,Q) intended for analysis, and a Viterbi-algorithm (10) is adapted (12,13) to the prevailing interferencies with the aid of the synchronizing-sequence. The data-sequence is Viterbi-analyzed through a large number of calculating stages, for the purpose of determining the bit-sequence of the data-sequence. According to the invention, a bit-sequence is extracted during the Viterbi-analysis, with a time-delay (TE), subsequent to effecting a few calculating stages, and a corresponding extracted signal-point is calculated (14). The analysis-intended signal-point corresponding to the extracted signal-point is divided and time-delayed (16,TE), and phase-compared (15) with the extracted signal-point. Corresponding phase-comparisons are made with respect to consecutive signal-points in the data-sequence and the angular magnitudes obtained in the phase-comparison are low-pass filtered and integrated (17) to form an angle-shift signal (V). The analysis-intended signal-points are displaced angularly (11) by the angle-shift signal (V) prior to the Viterbi-analysis. |
