Kantosignaali

Kantosignaali is a term used in telecommunications to refer to a high-frequency sinusoidal waveform that serves as a vehicle for information. The carrier has a fixed frequency, often denoted f_c, and an amplitude and phase that define its unmodulated state. Its primary role is to allow a baseband or low-frequency signal to be transmitted over a channel by modulation, which shifts the information spectrum to frequencies around the carrier.

Modulation techniques encode the information onto the carrier in different ways. In amplitude modulation (AM), the carrier’s amplitude varies with the message signal, producing sidebands around the carrier frequency. In frequency modulation (FM) and phase modulation (PM), the instantaneous frequency or phase of the carrier changes with the message, spreading the spectrum around f_c. In digital communications, symbols modulate the carrier to convey bits, and some schemes use a carrier that remains present (coherent detection), while others employ suppressed-carrier formats to improve power efficiency.

Generation and detection are central to kantosignaali systems. The carrier is produced by an oscillator, often stabilized by a crystal oscillator or a phase-locked loop. At the receiver, a locally generated carrier is used for coherent demodulation in many schemes, though non-coherent methods can operate without precise carrier alignment. Practical considerations include the choice of carrier frequency, required bandwidth, and power efficiency. Common examples of carrier-based systems appear in analog radio and television, as well as modern digital wireless communications.