| 摘要 |
PROBLEM TO BE SOLVED: To provide a digital receiver, having a demodulator which performs signal processing after A/D conversion of a four-phase phase modulation signal, using a simple constitution, compensates the frequency error between the carrier frequency of an inputted IF signal and the output frequency of a voltage- controlled oscillator by fine adjustment of the frequency of the voltage-controlled oscillator and takes out an accurate symbol. SOLUTION: The A/D converter 1 of this digital receiver samples and digitizes an inputted IF signal synchronously with the signal of the oscillation frequency generated by a VCO 3. Digitized reception data are sent to an orthogonal separation part 2, operated synchronously with the signal of the oscillation frequency of the VCO 3 and is separated orthogonally. A separated reception signal passes an LPF 4 and enters a symbol rate synchronizing part 5, and the frequency is changed to frequency data dependent upon the symbol rate. Reception data have the band limited by an LPF 6 and is sent to a phase detector 7, and a frequency error is derived by a phase shift detector. This error finely adjusts the frequency of the VCO 3. |
