| 摘要 |
PROBLEM TO BE SOLVED: To provide a demodulator that can prevent characteristics such as a bit error rate from being deteriorated, even if the frequency of an input IF signal deviates greatly from a frequency from an oscillator. SOLUTION: A phase rotation unit 4 is placed on a pre-stage of a roll-off filter 5 and by phase rotating operation of the phase rotation unit 4, a base-band signal is made to pass through a pass band of the roll-off filter 5. Furthermore, in a state with the carrier synchronization not being established, a signal whose frequency changes only for a range, in response to amplitude of a periodic waveform signal, is given to the phase rotation unit 4 to enable the phase rotation unit 4 to sweep the center frequency of the base-band signal for the base- band signal to pass through the passband of the roll-off filter 5. |
