| 摘要 |
PROBLEM TO BE SOLVED: To provide a simple and inexpensive circuit by which a C/N and a bit error rate(BER) are measured nearly in real time even when an error rate is low in the case that a modulation signal by the carrier modulation transmission system is received, demodulated and an original digital signal is recovered. SOLUTION: A counter 7 counts number of times of entry to a prescribed window W by I, Q signals obtained by applying orthogonal synchronization detection to an input QPSK signal within a prescribed time and gives the count to a C/N conversion circuit 9. Data denoting a cross reference between measured counts and C/N are stored in the C/N conversion circuit 9. The C/N is obtained based on conversion of the data from the count outputted from the counter T. |
