PMdemodulatsioon

PMdemodulatsioon refers to the extraction of the original information signal from a carrier wave that has been modulated in phase. In phase modulation (PM), the instantaneous phase of the carrier is varied in proportion to the message amplitude, causing the carrier frequency to fluctuate around its nominal value. This results in a spectrum that is broader than amplitude‑modulated signals but narrower than frequency‑modulated signals of equivalent modulation index.

The demodulation process typically begins with phase discrimination, which converts phase variations into instantaneous frequency deviations. A common approach uses a phase‑locked loop (PLL), where the PLL’s output tracks the phase of the incoming signal. The error voltage generated within the loop is proportional to the phase difference and can be filtered to recover the low‑frequency information signal. Synchronous detection (also called coherent detection) is another technique: the received signal is multiplied by a locally generated replica of the carrier, and the product is low‑pass filtered. This method requires precise knowledge of the carrier frequency and phase for optimal performance.

Compared with amplitude modulation (AM) and frequency modulation (FM), PM demodulation offers better resistance to amplitude noise, because noise that affects the signal amplitude does not directly translate into demodulation errors. However, PM can be more sensitive to phase noise and requires tighter synchronization between transmitter and receiver. In practice, many radio and satellite communication systems employ PM in combination with quadrature amplitude modulation (QAM) or phase shift keying (PSK) to achieve high spectral efficiency.

Typical applications of PMdemodulatsioon include digital television broadcasting, deep‑space communication, and certain wireless communication standards such as CDMA, where phase integrity is crucial. The choice of demodulation scheme depends on factors such as available bandwidth, signal‑to‑noise ratio, and computational complexity, with PLL‑based methods generally favored for analog or slowly varying signals and synchronous detection preferred for high‑speed digital data streams.