| 摘要 |
PURPOSE:To decrease the processing quantity of a digital signal and to double the operating frequency by using a signal of a fixed oscillator whose frequency is deviated by a wider frequency of fB' than a modulation signal band width fB so as to detect a received modulation wave, sampling it by a sampling frequency of 4nfB' (n is a positive odd number) and applying the switching sequentially. CONSTITUTION:The operating sampling frequency of an A/D converter 9 has 4Xn times of the pass band width BW/2 and its output spectrum is shown in figure (e). An output of a complex number filter 10 has a spectrum shown in figure (i) and its sampling frequency is fs/2. The complex number signal has an offset of BW/2 with respect to zero frequency and is shifted by the share. Thus, the complex number signal of base band whose phase is rotated is obtained. The signal is subjected to phase rotation correction as shown in 13, the timing is adjusted by clock extraction to form a normal reception signal. Thus, the digital signal processing is applied to all operations after the A/D converter 9 and the operating sampling frequency is realized by a half of that of the A/D converter 9. |
