Siirtoavainmodulaatio

Siirtoavainmodulaatio, also known as frequency shift keying (FSK), is a digital modulation technique used to transmit digital data by varying the frequency of a carrier signal. In FSK, digital data is represented by discrete changes in the frequency of an analog carrier wave. Typically, two or more distinct frequencies are used to represent binary ones and zeros. For instance, in binary FSK (BFSK), one frequency might represent a binary '0' and another frequency might represent a binary '1'. The modulator switches between these frequencies according to the input digital bit stream.

The receiver in an FSK system detects these frequency changes and converts them back into the original digital signal. Common detection methods include using bandpass filters to identify the specific frequencies or employing a phase-locked loop (PLL) circuit. FSK is relatively simple to implement and robust against noise compared to some other modulation schemes, making it suitable for applications where data rates are not extremely high.

Applications of FSK include radio communications, particularly for amateur radio, and in some older telecommunication systems. It is also used in simple wireless devices and as a component in more complex modulation schemes. The bandwidth occupied by an FSK signal depends on the frequency separation between the tones and the bit rate. While not as spectrally efficient as some advanced modulation techniques, its simplicity and reliability have ensured its continued use in various communication scenarios.