| 摘要 |
<p>A line network communication system transmits coded data signals on a base band carrier signal and includes a receiver capable of recovering the coded data signals from transmitted signals. The receiver operates in a search mode initially, in which a series of data signals received at (13) is compared, at different relative phases, with a series of coded reference signals using an arrangement of shift registers (12, 15) and an exclusive OR gate (11).
<??>The reference signals are generated by a coder (1) under the command of a central control unit (3). The control unit monitors the results of comparisons and varies, by means of a shifter circuit (6), the relative phase of compared signals until at least one comparison indicates a degree of correlation exceeding a threshold value. The control unit then operates, in a tracking mode, to verify that said degree of correlation is maintained for a preset number of subsequent comparisons and in dependence on a successful verification enters a locking mode. The control unit maintains a selected phase difference between compared series while the degree of correlation exceeding said threshold value exists. </p> |
