FSK_DEMODULATOR

Published:2009/7/14 22:36:00 Author:Jessie | From:SeekIC

Exar XR-210 FSK modulator-demodulator is connected as PLL system by providing AC coupling between VCO output pin 15 and pin 6. When input frequency isshifted, corresponding to data bit, polarity of DC voltage across phase detector output pins 2 and 3 is reversed. Voltage comparator and logic driver sections convert this DC level shift to binary pulse. C1 serves as PLL filter. C2 and C3 are postdetection filters. Timing capacitor C0 and fine-tune adjustment are used to set VCO midway between mark and space frequencies of input signal. Table gives typical values for 300-baud (103-type) and 1200-baud (202-type) modem applications. Supply can be 5-26 V.- Phase-Locked Loop Data Book, Exar Integrated Systems, Sunnyvale, CA, 1978, p 17-20.



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