What is FSK ? |FSK Advantages | FSK Disadvantages |Applications of FSK
Frequency Shift Keying
What is FSK ?
It is a digital modulation technique which shifts the frequency of the carrier with respect to binary data signal. FSK stands for Frequency Shift Keying. The FSK modulation technique uses two different carrier frequencies to represent binary 1 and binary 0.
As shown in the figure-1, carrier frequency f1 represents binary data one and carrier frequency f2 represents binary data zero. Here amplitude and phase of the carrier remain constant while carrier frequency is changed. Binary FSK (BFSK) can be represented by following mathematical equation:
s(t) = A* cos(2*π*f1*t) for Binary 1
s(t) = A* cos(2*π*f2*t) for Binary 0
In this equation, f2 and f2 are offset from carrier frequency (Fc) by equal but opposite amounts
Following are the typical applications of FSK modulation.
• It is used on voice grade lines for data rates upto 1200 bps.
• It is used for high frequency radio transmission from 3 to 30 MHz.
• It is also used in coaxial cable based LAN (Local Area Network) at higher frequencies.
Following are the benefits or advantages of FSK:
➨It has lower probability of error (Pe).
➨It provides high SNR (Signal to Noise Ratio).
➨It has higher immunity to noise due to constant envelope. Hence it is robust against variation in attenuation through channel.
➨FSK transmitter and FSK receiver implementations are simple for low data rate application.
Drawbacks or disadvantages of FSK
Following are the disadvantages of FSK:
➨It uses larger bandwidth compare to other modulation techniques such as ASK and PSK. Hence it is not bandwidth efficient.
➨The BER (Bit Error Rate) performance in AWGN channel is worse compare to PSK modulation.
In order to overcome drawbacks of BFSK, multiple FSK modulation techniques with more than two frequencies have been developed. In MFSK (Multiple FSK), more than one bits are represented by each signal elements
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