modulasjonens

Modulasjonens, translated as modulation in Norwegian, is the process of varying one or more properties of a carrier signal to encode information. The carrier is typically a sinusoidal wave; by changing its amplitude, frequency, or phase, a modulated signal can convey analog or digital data. Modulation enables transmission over long distances, multiplexing, and frequency reuse, and is foundational in radio, television, and data networks.

Analog modulation schemes include amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM). In AM, the carrier amplitude changes with the modulating signal; in FM, the instantaneous frequency follows the modulating signal; in PM, the instantaneous phase follows the modulating signal. Digital modulation encompasses schemes such as BPSK, QPSK, QAM, ASK, and FSK, often used with multilevel constellations to increase data throughput.

Key concepts include carrier, modulation index or depth, sidebands, and bandwidth. In FM, Carson's rule approximates bandwidth as 2(Δf + f_m). In digital schemes, bandwidth and error performance depend on the constellation size and coding. Demodulation recovers the original data at the receiver, using envelope detection for AM, discriminators or phase-locked loops for FM/PM, and coherent or noncoherent demodulation for digital schemes.

Historically, modulation techniques were developed for wireless telegraphy and radio in the early 20th century and have evolved with digital communications, including OFDM in modern wireless standards. Modulation remains essential to transmitting information efficiently and reliably across varied media.