Patent ID: 7031370
Filing Date: 2006-04-18
Classification: H04B,H04J

Abstract:
1. A spread spectrum communication system including a transmitter and receiver for performing spread spectrum communications based on a direct sequence spreading scheme, the transmitter comprising: a complex spreading portion for multiplying an I-phase component signal and a Q-phase component signal of a transmission signal by a complex number sequence which will not cause any phase transition of signals on an I-Q plane in a direction toward the origin thereof; a multiplier for multiplying signals output from the complex spreading portion by a pseudo-random sequence which is generated at a speed exceeding a symbol rate of the transmission signal; a roll-off filter for waveform shaping; and a carrier modulator for performing carrier modulation of signals having undergone waveform shaping, the receiver comprising: a carrier demodulator for performing carrier demodulation of a signal received from the transmitter; a multiplier for multiplying signals of two types output from the carrier demodulator by the pseudo-random sequence; a complex despreading portion for performing despreading by multiplying the signals of each type by the complex number sequence; and a phase-correcting portion for performing phase-correction so as to extract the I-phase and Q-phase components, wherein the complex number sequence is a pattern by which the I-phase component is constantly set at 1 or −1 and the Q-phase component changes between 1 and −1 alternately.