| 摘要 |
PROBLEM TO BE SOLVED: To provide a direct spread spectrum demodulator capable of being simply constituted of a digital circuit fully by demodulating information data by generating a correlative pulse, corresponding to the information data, and holding synchronism at the timing of the correlative pulse. SOLUTION: Base band signals 1a fetched into a shift register 1 are inputted as (m) pieces of signals to a ROM even 2 and a ROM odd 3, so that the correlative value of spread spectrum modulated information data '0' and '1' is provided by a PN signal for each one-chip clock. When no correlative pulse is generated in the scheduled time area, a window output 12a is synchronized with the new correlative pulse as '0' over all the time area. Further, a synchronism hold circuit operates a counter B15, gate B16 and AND gate 14 while using a synchronizing window and, even when the correlative pulse is missed, a stable information data shift clock can be provided. consequently, the synchronization of PN signal can be kept. |
