| 摘要 |
In a demodulator for use in demodulating a quadrature amplitude modulated signal into a first and a second digital signal by the use of a reproduction of a carrier wave, a pull-in phase is detected by a pull-in phase discriminator (55) after establishment of synchronization. The reproduction of the carrier wave is momentarily phase shifted in a phase modulator (65, 65') with reference to the pull-in phase and is produced as a phase shifted carrier signal. The resultant pull-in phase is momentarily corrected to avoid abnormal demodulation. Detection of the pull-in phase is possible either by monitoring a demodulating analog signal and the first and the second digital signals or by monitoring only the first and the second digital signals. The phase modulator may be either a two-phase modulator or a n pi /2-phase one where n is a natural number between unity and three, both inclusive.
|
