| 摘要 |
PROBLEM TO BE SOLVED: To provide a data broadcast CATV terminal equipment by using a loop filter controlling two oscillation signals so as to avoid a phase difference between the two thereby not using a high performance crystal vibrator with less dispersion or temperature drift. SOLUTION: A mixer 33 subtracts a 1st oscillation signal outputted from an oscillation means 34 from an input signal 20 to extract a QPSK modulation signal S22. A QPSK demodulator section 37 demodulates the QPSK modulation signal to generate a clock signal S25. A phase comparator section 36 compares a phase of the clock signal S25 with a phase of a signal S24 obtained by applying 1/n frequency division to a 2nd oscillation signal outputted from the oscillation means 34, then a loop filter 38 converts a differential signal outputted from the phase comparator 36 into a DC level signal S27 and it is outputted to the oscillation means 34. |
