Patent ID: 7321639

Claim:
A demodulator comprising: carrier information extraction means for extracting carrier information from a BPSK modulated signal; carrier generation means for generating a carrier based on the carrier information extracted by the carrier information extraction means; analog-to-digital conversion means for converting the BPSK modulated signal to a digital value; multiplication means for multiplying the carrier output from the carrier generation means by the BPSK modulated signal digitized by the analog-to-digital conversion means; carrier period integration means for integrating a result of the multiplication performed by the multiplication means, with respect to a period of the carrier generated by the carrier generation means; and discrimination means for binarizing a result of the integration performed by the carrier period integration means, wherein at least one of the carrier information extraction means and the carrier generation means is composed of a digital circuit, and the carrier generation means generates, as the carrier, a modified square wave, in which if the amplitude of the modified square wave is 1 during the period of time in which the phase thereof is from 0 to π/3, the amplitude becomes 2 during the period of time in which the phase is from π/3 to 2π/3, the amplitude becomes 1 during the period of time in which the phase is from 2π/3 to π, the amplitude becomes −1 during the period of time in which the phase is from π to 4π/3, the amplitude becomes −2 during the period of time in which the phase is from 4π/3 to 5π/3, and the amplitude becomes −1 during the period of time in which the phase is from 5π/3 to 2π.