modulerings

Modulerings, or modulation, is the process of altering a carrier signal to convey information. The carrier is a high-frequency waveform that carries a lower-frequency information signal (the modulating signal). By varying one or more properties of the carrier, such as its amplitude, frequency, or phase, information can be transmitted over a communication channel. Modulation also helps adapt signals to the characteristics of the channel and optimize power and bandwidth usage.

The main categories are analog modulation, such as amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM), and digital modulation, where data is encoded in discrete signal levels. In AM, the carrier's amplitude follows the modulating signal. In FM, the instantaneous frequency is varied; in PM, the instantaneous phase is varied. Digital modulation includes schemes such as phase-shift keying (PSK), quadrature phase-shift keying (QPSK), quadrature amplitude modulation (QAM), and frequency-shift keying (FSK).

Each method has trade-offs in bandwidth, noise robustness, and power efficiency. Analog modulation typically requires wider analog channels and is more susceptible to noise, while digital modulation can achieve higher spectral efficiency and easier error correction. Demodulation at the receiver reverses the modulation to recover the original information, often using synchronization and filtering.

Modulation is central to many technologies, including radio broadcasting, television, telephony, data networks, and satellite communications. Techniques such as OFDM and advanced QAM are used to increase capacity in modern wireless systems. The concept has roots in early 20th-century experiments in radio transmission and has evolved alongside advances in signal processing and communications theory.