Analogsignal

An analog signal is a continuous-time signal that represents information by continuously varying quantities. Unlike digital signals, an analog signal can take on an infinite number of values within a given range and is defined at all real-valued time instants. In practice, common analog signals are electrical voltages or currents that mirror a physical quantity such as sound, light intensity, or temperature.

An analog signal is characterized by its time-domain form x(t) for t in real numbers and by its spectrum X(f). It can be amplitude-modulated, frequency-modulated, or phase-modulated. It may be band-limited, with energy confined to a finite frequency range, or broadband, spanning a wide range of frequencies.

Compared with digital signals, analog signals provide high fidelity in principle but are more susceptible to noise, distortion, and degradation over transmission or storage. Small noise is often inseparable from the signal and can accumulate over distance and processing. Analog systems use continuous-time elements such as resistors, capacitors, inductors, and operational amplifiers.

Applications include audio and video signals, radio frequency transmissions, sensor and instrumentation signals, and continuous-time control systems. Analog storage media include vinyl records and magnetic tapes; analog communications include AM/FM radio and telephone lines.

Processing of analog signals is performed with analog electronics, including amplifiers, filters, and modulators. In many systems, analog signals are converted to digital form by analog-to-digital converters for digital processing, storage, and transmission, with digital-to-analog conversion used at the output. The study of analog signal properties often relies on Fourier analysis and other time- and frequency-domain tools.