Communications I Dr. Mohammed Hawa Introduction to Digital - FET

impulses, as shown in Figure 4 below 4 . We will explain in class the differencebetween practically-sampled signals, naturally-sampled signals, and ideally-sampledsignals.Samples Values Sampled Signal, m s (t)m ptT sSampling Time-m pT sFigure 4. Practical Sampling.II. Quantization:The next step in analog-to-digital conversion is Quantization, which limits the digitaldata to be sent. Quantization is the process in which each sample value isapproximated or “limited to” a relatively-small set of discrete quantization levels. Forexample, in uniform quantization if the amplitude of the signal m(t) lies in the range(-mp, mp), we can partition this continuous range into L discrete intervals, each oflength v = 2 mp /L, and the value of each sample is then approximated to only oneof these L levels.Notice that quantization can be done in several different ways. In one method thevalue of each sample can be “truncated” to the quantization level just below it. Thisis shown in Figure 5 below for L = 5 levels.Sample Values now Quantizedm pm(t)errorQuantization Error = m s(t) – m sq(t) = [0, v]-m pFigure 5.m sq(t)vtL = 5Levels,Rule =Truncate4 Typical IC-based ADC chips perform sampling, quantization and mapping all on the same chip.4