FREQUENCY CONTROL CIRCUIT, RADIO TRANSMISSION AND RECEPTION DEVICE USING SAME, AND ITS FREQUENCY CONTROL METHOD

摘要

PROBLEM TO BE SOLVED: To lower high-speed acquisition and a clock speed and to correct an error in transmission frequency according to an error in reception frequency by digitizing an AFC circuit.

SOLUTION: A quadrature demodulator 15 applies quadrature demodulation to a received intermediate-frequency signal and outputs a complex code of I/Q. A phase error detection par t 21 outputs the phase difference between the actual phase of I/Q and a reference phase as error data corresponding to a frequency deviation. A DVCO part 23 outputs a sin/cos wave of frequency corresponding to the error data. A complex multiplier 19 performs complex multiplication of the output I/Q of the quadrature demodulator 15 by a sin/cos wave to correct the phase deviation and inputs it to a symbol judgement part 20. An quadrature modulator 26 performs quadrature modulation of a reference frequency signal of an oscillator 14 for transmission and reception with the sin/cos wave from the DVCO part 23 to generate a local oscillation signal for transmission whose frequency is deviated by the frequency deviation.

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