| 摘要 |
PROBLEM TO BE SOLVED: To quickly detect a symbol timing with a high reproducing precision and a small operation volume in a demodulator of a π/4 shift QPSK modulated signal. SOLUTION: The demodulator is provided with a sampling means which converts a reception signal modulated in the π/4 shift QPSK system to a quadrature demodulation signal train oversampled with the one-symbol period, a differential means which obtains a differential vector from a sample of one symbol before, and a timing detection means which detects a sample closest to the axis of declination π/4 on the vector plane from the output vector of the differential means in each one-symbol period and takes a sample, which is shifted from the detection timing of the closest sample by a timing corresponding to a half symbol, as the symbol timing. |
