Frequency shift keying can be divided into two types, coherent and non coherent. In coherent forms of FSK, there is no phase discontinuity in the output signal. FSK modulation formats generate modulated waveforms that are strictly real values, and thus tend not to share common features with quadrature amplitude modulation (QAM) schemes. In noncoherent forms of FSK, the instantaneous frequency is shifted between two discrete values. In BPSK, these are referred to as the “mark” and “space” frequencies. In this demonstration, we will illustrate noncoherent because it can be more easily represented in the frequency domain.
Next, we will examine various parameters of an FSK transmitter and observe their affects in the frequency domain. Most notably, we will change characteristics such as: M-ary, deviation frequency, and symbol rate to observe the effects upon the frequency domain of the signal.
As this demonstration illustrates, FSK involves the transmission of digital information through variations of a carrier’s frequency. In addition, it illustrates the relationship between carrier frequency, M-ary, frequency deviation, and symbol rate.
Example code from the Example Code Exchange in the NI Community is licensed with the MIT license.