For a binary FSK signal with a mask frequency of 49 kHz, a space-frequency of 51 kHz and on the input bit rate of 2 kbps, the peak frequency deviation will be

Concept:

In FSK (Frequency Shift Keying), binary 1 is represented with a high-frequency carrier signal, and binary 0 is represented with a low-frequency carrier, i.e. in FSK, the carrier frequency is switched between 2 extremes.

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• Frequency measurements of the FSK signal are usually stated in terms of “shift” and center frequency. The shift is the frequency difference between the mark and space frequencies.
• The nominal center frequency is halfway between the mark and space frequencies.
• Frequency deviation is equal to the absolute value of the difference between the center frequency and the mark or space frequencies.​

The deviation is also equal, numerically, to one-half of the shift, i.e.

|f_s - f_m|= 2 Δf

Δf = frequency deviation

f_s = space-frequency

f_m = mask frequency

Calculation:

With f_s = 51 kHz and f_m = 49 kHz

\({\rm{\Delta }}f = \frac{{\left| {{f_s} - {f_m}\;} \right|}}{2}\) 

\(= \frac{{\left| {51 - 49} \right|}}{2}\;kHz\) 

Δf = 1 kHz

The bandwidth of FSK is given by:

\(\left( {{f_s} + \frac{1}{{{T_b}}}} \right) - \left( {{f_m} - \frac{1}{{{T_b}}}} \right)\) 

\(= \left( {{f_s} - {f_m}} \right) + \frac{2}{{{T_b}}}\) 

|f_s - f_m|= 2 Δf