| 摘要 |
PURPOSE:To estimate a sample timing like a digital by measuring the phase of a pi/4 shift QPSK-modulated intermediate frequency signal. CONSTITUTION:An input signal is band-limited by a filter 1, and passed through an amplitude limiting limiter 2. Then, a phase difference between a reference signal 3 and the input signal is measured by a phase measuring circuit 4 more than two times in one baud. A phase change in a certain section is obtained by using a delay circuit 5 and a difference detecting circuit 6. The result is inputted to an absolute value detecting circuit 7, the difference between adjacent outputs is obtained and is defined as the phase error of a timing. Then, a loop is formed by using a loop filter 10, reference signal 11, and phase control circuit 12. |
