Frequency-Shi- Keying

FSK

Logic 1 input, vm(t) = + 1

Logic 0 input, vm(t) = - 1

FSK in the frequency domain

Frequency devia?on, f (hertz)

Where: |fm- fs| = absolute dierence

between the mark and space frequencies (hertz)

FSK in the ?me domain

fc + f fc - f

Truth table for BFSK modula?on

FSK Bit Rate, Baud and Bandwidth

FSK Bit Rate, Baud and Bandwidth

The baud for binary FSK can also be determined by subs?tu?ng N = 1

Minimum bandwidth for FSK

Where: B = minimum Nyquist Bandwidth (hertz) f = frequency devia?on (|fm- fs|) (hertz) fb = input bit rate (bps)

Example:

Determine: (a)peak frequency devia?on (b)minimum bandwidth (c)Baud for binary FSK signal with a mark frequency of 49 kHz, a space frequency of 51 kHz and an input bit rate of 2 kbps

Example:

Using a Bessel Table, determine the minimum bandwidth for the same FSK signal described in the previous example, with a mark frequency of 49 kHz, a space frequency of 51 kHz, and an input bit rate of 2 kbps.

FSK Modulator

Noncoherent FSK demodulator

Coherent FSK demodulator

PLL-FSK demodulator

Noncon?nuous FSK waveform

Con?nuous MSK waveform