Implementation of FSK Modulation and Demodulation using CD74HC4046A

In telecommunications and signal processing, frequency modulation (FM) is encoding of information on a carrier wave by varying the instantaneous frequency of the wave. Digital data can be encoded and transmitted via carrier wave by shifting the carrier's frequency among a predefined set of frequencies—a technique known as frequency-shift keying (FSK). FSK is widely used in modems, radio-teletype and fax modems, and can also be used to send Morse code.

Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave. This application report discusses logiclevel implementation of binary FSK (BFSK) modulator and demodulator using a phase-locked loop PLL device – CD54HC4046A, CD54HCT4046A, CD74HC4046A, and CD74HCT4046A (hereafter in this document referred to as HC/HCT4046A). BFSK is the simplest FSK, using a pair of discrete frequencies to transmit binary information.