| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce circuit scale by simplifying the configuration of a unique word detection circuit in a digital communication system employing aπ/4 shift QPSK as the modulation system. SOLUTION: A unique word of 2n symbols consists of combinations of two systems of unique words that are respectively sent for one symbol each, the one is mapped at one set of QPSK symbol points having a phase difference of 180 deg. on a constellation of theπ/4 shift QPSK and the other is mapped at symbol points in crossing with the one set of the points at an angular difference of 45 deg.. An I phase inner product arithmetic circuit 2 at a receiver side obtains an I phase correlation value CI by dividing past 2n symbols of the I phase component of a received base band signal into two n-symbol series, executing the correlation arithmetic operation with unique words of each system and summing the results. A correlation value peak detection circuit 12 provides an output of a point when the sum of the I phase correlation value CI and a Q phase correlation value CQ exceeds a threshold level as a unique word timing object.</p> |
