GFSK vs FSK: Understanding the Key Differences

This page compares GFSK and FSK modulation techniques across various system parameters. Let’s dive into the differences.

FSK (Frequency Shift Keying)

FSK stands for Frequency Shift Keying. This modulation technique is used to modulate a binary string of 1s and 0s, making it suitable for transmission using an RF carrier frequency from one end to another.

A simple example of FSK is Binary FSK (BFSK). In BFSK, binary information (1 and 0) is represented by a change in frequency. For example, binary 1 is represented by frequency f1, and binary 0 is represented by frequency f2.

FSK modulation

The basic digital modulation types include ASK, FSK, and PSK.

One significant drawback of FSK modulation is its unlimited spectral width. In FSK, the carrier frequency (fc) jumps sharply to a different frequency (fd). This significantly decreases spectral efficiency.

Continuous phase FSK modulation with an index of 0.5 is referred to as MSK modulation.

GFSK (Gaussian Frequency Shift Keying)

GFSK stands for Gaussian Frequency Shift Keying modulation.

In GFSK, baseband pulses (consisting of -1 and 1) are first passed through a Gaussian filter before modulation. This process smooths the pulses and limits the modulated spectrum width. This is known as pulse shaping.

In GFSK, the spectral width is limited due to the filter. Here, fc climbs slowly and eventually reaches a value equal to fd.