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Friday, June 10, 2011

Why Data Converters?

        Our environment is full of analog signals, such as sound, light, temperature, voltage, current, and electromagnetic waves. By the use of sensors, these signals are usually converted to electrical quantities, voltage or current, and processed to extract useful information. The processing can be carried out in analog or digital domain. During the last two decades, digital signal processing has become immensely powerful. Advances in technology of Integrated Circuits (IC) made it possible to implement digital signal processors with a reasonable amount of silicon wafer area, low power consumption, and affordable price for different applications. Digital signal processors (DSP) can easily be programmed for different algorithms. Many functions of analog circuits have been replaced by equivalent algorithms in DSPs. Another major advantage of DSP algorithms is that functionality is not subjected to fluctuations and variations with respect to time and temperature.

 In addition, there are some functions that can be performed by DSP, but are difficult to implement with analog circuits. One such function is a linear phase filter. The main advantages of DSP over analog processing are programmability, repeatability, stability, and flexibility.
         Although an increasing amount of signal processing is performed in digital domain, the interface between analog and digital domain will remain a fundamentally necessary element. The gates of DSPs to analog signals are Analog-to-digital (A/D) and Digital-to-Analog (D/A) converters. For example, an echo cancellation in an amphitheater makes use of a microphone that generates a voltage in the range of a few microvolts to a couple of milivolts. This analog voltage should be amplified and converted to a digital signal for extensive processing by DSP. After echo cancellation, it is converted to an analog signal, which can be applied to a power amplifier.

Fig 4.1

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