BINARY FREQUENCY SHIFT KEYING WITH DATA MODULATED IN DIGITAL DOMAIN AND CARRIER GENERATED FROM INTERMEDIATE FREQUENCY

摘要

Binary frequency shift keying modulation is implemented by choosing appropriate phases of a high frequency clock to generate a modulated intermediate clock frequency. The high frequency clock is chosen to be (M+0.5)*fc, where fc is the carrier frequency and M is an integer. Depending on the binary data ‘1’ or ‘0’ to be transmitted, ‘M’ or ‘M+1’ clock phases from the high frequency clock are converted to an intermediate clock that is 2*N times faster than the carrier frequency, where N is an integer. This intermediate clock, generated entirely in the digital domain, has the required data modulation in it, and is used to generate N pulse width modulated (PWM) phases of waveforms operating at the carrier frequency. The N phases are then weighed appropriately to synthesize a sine waveform whose lower harmonics are substantially suppressed.