modulátor

Modulátor is a device or circuit that imposes an information signal onto a carrier signal in order to enable transmission of the information over a communication channel. The purpose is to shift or encode the data so it can travel efficiently and be recovered later by a demodulator.

Analog modulators vary a property of the carrier, such as its amplitude, frequency, or phase, in proportion to the modulating signal. Common analog schemes include amplitude modulation (AM), frequency modulation (FM) and phase modulation (PM). Each scheme has characteristic spectral and noise properties and is suited to different channel conditions and applications.

Digital modulators map a sequence of bits to symbols and then modulate the carrier accordingly. Typical digital schemes include binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), higher-order phase shift keying, and quadrature amplitude modulation (QAM). Modern systems often combine digital modulation with multi-carrier techniques such as orthogonal frequency-division multiplexing (OFDM) to improve spectral efficiency and robustness.

Architecturally, modulators can be implemented as analog circuits, digital signal processing blocks, or hybrid systems. Analog modulators use mixers, oscillators, and filters to produce the modulated output. Digital modulators implement modulation in software or hardware DSP, followed by digital-to-analog conversion and RF upconversion.

Applications span radio broadcasting, television and satellite transmissions, cellular and wireless networks, data modems, and laboratory equipment. In consumer devices, modulators are used to convert baseband signals to RF channels (often with QAM or OFDM). See also demodulation for the complementary process.