PURPOSE: To constitute a demodulator with a digital circuit without use of a multiplier for a limiter section by outputting the sum of absolute values of I and Q signals or the absolute value which is larger and controlling a scaler varying the amplitude of the I and Q signals.
CONSTITUTION: A limiter section 1 is constituted of a synthesizer 3 obtaining the synthesized wave of I and Q signals, two scalers 5, 6 applying amplitude limit to each of the I and Q signals and a control circuit 4 controlling the scalers 5, 6 in response to the output from the synthesizer 3. A demodulation section 2 is constituted of two differentiation circuits 7, 8 obtaining respective derivatives of I' and Q' signals being output signals of the scalers 5, 6 of the limiter section 1, two polarity deciding circuits 9, 10 deciding the polarity of the I' and Q' signals to decide the operation of the polarity inversion circuit, two polarity inversion circuits 11, 12 revising each polarity of the derivatives of the I' and Q' signals in response to the information from the polarity deciding circuits 9, 10 and a subtractor 13 obtaining the difference between the two polarity discrimination circuit output signals.
TSUKAMOTO NOBUO
NAKAKOSHI ARATA
HOSHI ATSUSHI
HORAGUCHI MASATO
KOKUSAI ELECTRIC CO LTD
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