8.1 Analog to Digital Conversion

There could be a need to convert an analog signal into a digital form. For example, to communicate a human voice over a network.

As described earlier in the course, an analog signal is a time continuous signal that include an infinite number of values.

The analog to digital conversion process involves representing the information contained in an analog continuous wave form as a series of digital pulses (1s or 0s) with the minimum loss of information.

A widely used analog to digital conversion method is the Pulse Code Modulation (PCM) which involves a number of steps as illustrated in Figure 8.1:

	1.	Pulse Amplitude Modulation (PAM): that samples the analog signal to be converted and generates a series of pulses representing the signal.
	2.	Quantization: that assigns integral values (predefined for each voltage level) to the
	3.	Binary Encoding: where the integral value specified in step 2 for each sampled pulse is converted into a binary representation, thus generating a stream of bits representing the original analog signal.
	4.	Digital to Digital Encoding: using any of the encoding methods discussed in Section 7.2 to convert the binary data generated in step 3 into a digital signal for transmission.

8.1 Analog to Digital Conversion

Figure 8.1: Main Steps of the PCM Process