| 摘要 |
PROBLEM TO BE SOLVED: To suppress erroneous demodulation of such signal as an FSK caused by inconsistency of BPF characteristics. SOLUTION: A delay circuit 5 stores sequentially digital signals passed through a BPF 4 in a ring buffer. An autocorrelation processing circuit 6A reads, out of the delay circuit 5, a sample obtained by going by N samples into the past from that buffered at the present moment and a sample which is obtained by going back by D1 samples into the past, and calculates the inner product of both vectors as the autocorrelation. An autocorrelation processing circuit 6B calculates as an autocorrelation the vector inner product between the sample going by N samples back into the past from that buffered at the present movement and the sample going by D2 samples back into the part from the present moment. Integral processing circuits 7A and 7B suppress rapid changes in the autocorrelation values caused by autocorrelation processing circuits 6A and 6B, and a comparator circuit 8 decides the value of the demodulation signal by comparing the values from the integral processing circuits 7A and 7B. |
