Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Patent
1997-01-02
1998-06-23
Chin, Wellington
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
375269, 375298, 332103, H04L 512
Patent
active
057712638
ABSTRACT:
A communication system having a carrier oscillator for generating a carrier of predetermined frequency, a quadrature modulator for orthogonally modulating the carrier by input baseband I and Q signals and outputting a quadrature modulation wave, and a quadrature demodulator for orthogonally demodulating the quadrature modulation wave using the carrier and outputting demodulation baseband I and Q signals. The phase of the carrier input to the quadrature demodulator is shifted by a predetermined amount in accordance with a phase shift signal. The amplitude of the demodulation baseband I and Q signals output from the quadrature demodulator is corrected on the basis of a control signal, and demodulation baseband I and Q signals thus corrected are output. The amplitude of the input baseband I and Q signals is corrected on the basis of the control signal, and the baseband I and Q signals thus corrected are input to the quadrature modulator. An amplitude error is detected between the amplitude-corrected demodulation baseband I and Q signals. The control signal is generated so that amplitude coincides between the baseband I and Q signals of the quadrature modulation wave coincide and between the demodulation baseband I and Q signals output from the quadrature demodulator on the basis of the detected amplitude error.
REFERENCES:
patent: 3959726 (1976-05-01), Hinoshita et al.
patent: 4011405 (1977-03-01), Ridout et al.
patent: 4700151 (1987-10-01), Nagata
patent: 5524286 (1996-06-01), Chiesa et al.
Fujiwara Yukinari
Kanazawa Masayuki
Chin Wellington
Hitachi Denshi Kabushiki Kaisha
Tran Congvan
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