| 摘要 |
PURPOSE:To improve frequency characteristics by increasing the number of conversion points without decreasing a discrimination frequency by providing DFT circuit groups which provide discrete Fourier transformation and by enabling each DFT circuit to perform transformation processing differing in start time in parallel. CONSTITUTION:A pair of A/D converter 201 and expander 202 are provided with multipliers 211 and 221, wind function generators 212 and 222, and six discrete Fourier transforming (DFT) circuit groups 213 and 223. To the outputs of circuit groups 213 and 223, comparing circuits 215 and 225 are connected. Then, the outputs of generators 212 and 222 are given a time difference a half integral time T of each DFT, and threshold level generating circuits 214 and 224 calculate the cumulative power of the signal between the start and end of DFT to determine and input threshold levels to comparing circuits 215 and 225. Those circuits 215 and 225 compare the outputs of circuit groups 213 and 223 with the threshold levels in parallel to apply the outputs to discriminating circuit 203, which time-divides the outputs by period T/2 for signal processing. |
