pulsikoodmodulatsiooni

Pulsikoodmodulatsiooni, often abbreviated as PCM, is a method used to represent analog signals digitally. It is a fundamental technique in digital signal processing and is widely employed in telecommunications, audio recording, and various other digital systems. The process involves three main steps: sampling, quantization, and encoding.

Sampling is the first step, where the analog signal is measured at discrete, regular intervals. The rate at which these samples are taken is called the sampling rate. According to the Nyquist-Shannon sampling theorem, the sampling rate must be at least twice the highest frequency present in the analog signal to accurately reconstruct it.

The second step is quantization. Each sample, which is a continuous value, is approximated to the nearest value within a predefined set of discrete levels. This process introduces a small error, known as quantization error, which is inherent to PCM. The number of discrete levels used determines the resolution of the digital representation. A higher number of levels results in less quantization error but requires more bits to represent each sample.

Finally, encoding translates the quantized samples into a binary code. Each quantized level is assigned a unique binary word. This binary stream is the digital representation of the original analog signal. When this digital signal needs to be converted back to analog, a decoder performs the inverse process, known as pulse-code modulation demodulation, which involves decoding the binary stream, reconstructing the quantized levels, and then using a low-pass filter to smooth out the staircase-like signal back into an approximation of the original analog waveform.