How does pulse code modulation work

In this process, the quantization interval is smaller near zero. This LPF is used to remove the high frequency HF components that are present within the input analog signal. Here this signal is higher as compared to the highest frequency message signal so that it avoids aliasing of the message signal.

The signal strength can be enhanced through this regenerative repeater. The main function of a decoder circuit is to decode the pulse-coded signal to repeat the actual signal. This circuit works like a demodulator. After the conversion of DAC digital-to-analog conversion is done with the help of the decoder and regenerative circuit, then an LPF low-pass filter is used to get back the original signal. So, this is known as the reconstruction filter. So, this entire procedure can be repeated within a reverse model to get the actual signal.

The encoder encodes the quantized samples. Each quantized sample is encoded into an 8-bit codeword by using A-law in the encoding process. Pulse code modulation is similar to PWM, PAM otherwise PPM however there is a significant disparity among them that is they are analog pulse modulation systems but Pulse code modulation is a digital pulse modulation system.

The data can be transmitted in code words format. The important operations within the transmitter of pulse code modulation mainly include sampling, quantizing, and encoding. In DPCM only the difference between a sample and the previous value is encoded. The difference will be much smaller than the total sample value so we need some bits for getting the same accuracy as in ordinary PCM.

So that the required bit rate will also reduce. For example, in 5-bit code 1 bit is for polarity, and the remaining 4 bits for 16 quantum levels. ADPCM is achieved by adapting the quantizing levels to analog signal characteristics. We can estimate the values with the preceding sample values. Error estimation is done as same as in DPCM. In this method data rate is half of the conventional PCM.

This is one kind of modulation technique, used to encode uncompressed audio data digitally, wherever audio signals are signified through a series of amplitude values from a model on a linear scale where these values are comparative to the amplitudes. So, the amplitude values are quantized linearly, therefore similar to a very large set of feasible values through a quite small set of values that may be discrete symbols or integers. High-Performance Cloud Computing.

Techopedia Terms. Connect with us. Sign up. Term of the Day. Best of Techopedia weekly. News and Special Offers occasional. Techopedia Explains Pulse Code Modulation PCM Each sample in a PCM is quantized, approximating a very large set of possible values by a relatively small set of values, which may be integers or even discrete symbols.

Share this Term. Tech moves fast! View Conferences. Gartner Webinars Expert insights and strategies to address your priorities and solve your most pressing challenges. View Webinars. Related Terms Business Technologist. Digital Assets. Digital Finance. Fusion Team. This is the technique which helps to collect the sample data at instantaneous values of message signal, so as to reconstruct the original signal.

The sampling rate must be greater than twice the highest frequency component W of the message signal, in accordance with the sampling theorem. Quantizing is a process of reducing the excessive bits and confining the data. The sampled output when given to Quantizer, reduces the redundant bits and compresses the value. The digitization of analog signal is done by the encoder. It designates each quantized level by a binary code. The sampling done here is the sample-and-hold process. Encoding minimizes the bandwidth used.

This section increases the signal strength.