demodulates

Demodulation is the process of extracting the original information-bearing signal from a modulated carrier. It is the reverse of modulation and is essential to receiver systems. The objective is to recover the baseband signal with fidelity, despite channel noise and distortion.

Analogue demodulation varies by modulation type. Amplitude modulation (AM) can be demodulated with an envelope detector, which rectifies and filters the signal to recover the modulating waveform. Frequency modulation (FM) and phase modulation (PM) use ratio discriminators, phase detectors, or phase-locked loops to track the instantaneous frequency or phase of the carrier. Modern systems often employ coherent (synchronous) demodulation, which uses a locally generated carrier reference to maximize sensitivity, along with filtering and synchronization stages.

Digital demodulation handles digital modulation formats such as ASK, FSK, PSK, and QAM. Demodulation typically involves down-conversion to baseband, sampling, timing recovery, carrier recovery, and symbol decision. It may employ matched filtering, equalization, and error correction to combat channel distortions and noise.

Applications include radio receivers, television tuners, data communication links, cellular networks, and optical communications. Demodulation performance depends on signal-to-noise ratio, bandwidth, and channel conditions; nonidealities such as amplitude nonlinearity, phase noise, and interference can degrade the recovered signal.