Frequency_shift_decoder_FSK

Published:2009/7/24 23:34:00 Author:Jessie | From:SeekIC

This circuit shows an XR-2211 connected for FSK decoding. Recommended component values for some of the most commonly used FSK bands are given in Fig. 3-9B. Internal functions of the XR-2211 are given in Fig. 3-9C. The.circuit can be tailored for any FSK-decoding application by the choice of R0, R1,C0, C1, and CF. For a given set of FSK mark and space frequencies, f1 and f2, these parameters can be calculated as follows: Calculate PLL center frequency fo using: Use 18 kΩ for R0 so that R0 can be set to 20 kΩ with the series Rx pot. Calculate the value of C0 using: C0=1/R0f0.Calculate R1 to give a difference frequency equal to the mark-space deviation: R1= R0[(f0/f1--/f2)].Calculate C1 (which sets the loop-filter time constant) using: C1= C0/4.Calculate CF (which is the data-filter capacitance with RF=100 kΩ and RF= 510 kΩ) using: CF (inμF) =3/baud rate. All calculated values, value. except R0, can be rounded off to the nearest standard walue .R0 can be fine tuned with Rx.



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