Demodulaatori

Demodulaatori is a device or circuit that extracts the original information signal from a modulated carrier. In communications, modulation encodes information onto a carrier for transmission, and demodulation recovers that information at the receiver. Demodulaatori are used in radio receivers, television tuners, data communication equipment, and in optical communications.

Types and approaches

Demodulaatori can be classified as analog or digital. Analog demodulation includes AM demodulation (envelope detector or synchronous detector), FM demodulation (discriminator, phase-locked loop, or quadrature detector), and PM demodulation (often using differentiators or PLL-based methods). Digital demodulation covers modulations such as ASK, FSK, PSK, QAM, and OFDM; digital demodulators often require carrier recovery, symbol timing, and equalization. Some digital schemes use coherent detection with a reference carrier, while others use non-coherent techniques.

Architecture and use

A demodulaatori is typically a later stage in a receiver chain, following front-end RF downconversion and filtering. It may operate together with a digital baseband processor or function as an all-analog block. In optical communications, coherent demodulation retrieves amplitude, phase, and polarization information from a modulated optical field.

Performance considerations

Key factors include sensitivity to noise and distortion, accuracy of phase and frequency synchronization, bandwidth requirements, and implementation complexity. The choice of modulation family, channel conditions, and available error-correcting coding influence the efficiency and reliability of demodulation.