| 摘要 |
PURPOSE:To obtain a demodulator in the digital portable telephone set in which miniaturization, low cost and low power consumption are effectively realized. CONSTITUTION:A phase difference between an output phase and an input phase from a 1-symbol delay section 11 is detected by a phase difference detection section 12 and inputted to an AFC (frequency drift compensation) section 13. The AFC section 13 uses comparator sections 132, 133 to discriminate an error of the phase difference based on low-order 3-bits of the phase difference and while the discrimination result is consecutive for K times or over, an up-down counter 136 is controlled to set an AFC correction value to the counter 136. The correction value set to the counter 136 is fed to an adder section 131 receiving the input phase and an output of the adder section 131 is fed to the phase difference detection section 12. Then a phase error appearing at the phase difference is cancelled and a demodulation symbol clock is extracted based on a 1/2pi or over detection signal DT of an absolute value of the phase difference. |
