CHAPTER 15 DSP Technology SAMPLING OF CONTINUOUS-TIME SIGNALS The most common way to generate a digital sequence is to start with a continuous-time (analog) signal and create a discrete-time signal. For example, speech signals are continuous-time signals because they are continuous waves of acoustic pressure. A microphone is the transducer that converts the acoustic signal into a continuous-time electric signal. In order to process this signal digitally, it is necessary to convert this signal into the digital domain. Finally, after processing, it is often necessary to convert the discrete-time signal back into a continuous-time signal for playback through a loudspeaker system. The process of converting an analog signal to a digital signal is often modeled as a two-step process, as shown in Figure 15.9 , of converting a continuous-time signal to a discrete-time signal (with infinite resolution of the amplitude) and then quantizing the discrete-time signal into finite precision values (creating the digital sequence) that can be processed by a computer. 1 The process of converting the continuous-time signal into a discrete-time signal will be introduced, and then quantization will be reviewed. The quantization step is necessary to create a sample value that has a data word size that is compatible with the arithmetic capabilities of the target DSP. All real-world analog-to-digital converters (A/Ds) perform both the sampling and quantization process internal to the A/D device, but it is useful to discuss the subsystems separately because they have different significance and design trade-offs. Continuous to discrete conversion The most common method for converting a continuous-time signal, x c ( t ), into a discrete-time signal, x [ n ], is to uniformly sample the signal every T seconds with the equation