| 摘要 |
PROBLEM TO BE SOLVED: To further improve the reception characteristic of differential demodulation by separating differential demodulation of frequency synchronization from coherent demodulation of phase synchronization and also using coherent demodulation in a reception environment through Doppler means. SOLUTION: A differential decoder 9 inputs an orthogonal transform signal from which the deviation of a frequency is eliminated and performs differential decoding. A coherent decoder 10 inputs an orthogonal transform signal, from which phase shift is further eliminated and performs coherent decoding. A Doppler shift computer 12 inputs speed information of a moving body, calculates the Doppler shift and outputs the result to a signal selecting means 11. The means 11 selects outputs of the decoders 9 and 10 based on the Doppler shift. A carrier phase reproducing device 13 is connected to an output of low-pass filters 6 and 7, detects only a phase error through inverse modulation apart from deviation correction of a frequency by an automatic frequency controller 8, outputs the result to a complex multiplier 3, corrects the phase error and performs an absolute phase demodulation. |
