| 摘要 |
A carrier reproducing circuit capable of reproducing a carrier quickly, wherein: a signal point arrangement converting circuit (14) detects the signal point arrangement of a demodulating baseband signal of a carrier when the carrier has a frequency different by a predetermined value from the center frequency of the modulated wave; a variance calculating circuit (15) calculates, based on the signal point arrangement, the number of times that the variance exceeds a preset threshold per unit time; a CN determination circuit (16) determines the reception CN ratio based on the number of times; a scanning step frequency width converting circuit (19) sets a frequency width changed by one step based on the determined reception CN ratio; the carrier for demodulation is sent out by changing oscillation frequencies of oscillators (6, 7) through an AFC circuit (20) based on the preset frequency width; and when a carrier synchronization judging circuit (18) detects that the number of times decreases to a value equal to or smaller than a threshold determined based on the reception CN ratio, the scanning by the AFC circuit (20) is stopped.
|
