JPS54156461A - Demodulator for amplitude modulation wave - Google Patents

Abstract

PURPOSE: To establish the demodulator for amplitude modulation waves in which the frequency between the modulation signal and carrier are close, by constituting the unit with the waveform processing circuit, differentiation circuit, sampling hold SH circuit, incremental value operation circuit, and integration circuit etc.

CONSTITUTION: The amplitude modulation wave (a) is inputted to the waveform processing circuit 7 consisting of full-wave rectifier, PLL, 1/2 frequency demultiplication, and multiplier. The multiplication circuit 74 in the circuit 7 outputs the signal (h) multiplying f1 to the signal 9 when the output of the 1/2 frequency demultiplication circuit 75 is at high level and -1 when low level. The signal (h) is sampled with the differentiation output signals g and e different slightly in phase. The signals (i) and (j) are obtained with the first and second SH circuits and buffers 53 and 54, and they are inputted to the subtraction circuit 11 constituting the incremental operaton circuit, and the signal (k) is outputted from the circuit 11. The signal (k) is integrated with the signal (l) via the analog gate 12 at the integration circuit 13, to obtain the signal m and the signal (n) is outputted via LPF 14. Since the carrier frequency component included in the signals (i) and (j) is sufficiently removed in the signal (m), LPF 14 can be simple.

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