EE 230 Lecture 40 Spring 2010

EE 230 Lecture 40 Spring 2010 - EE 230 Lecture 40 Data...

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EE 230 Lecture 40 Data Converters Amplitude Quantization Quantization Noise
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Time Quantization Typical ADC Environment Review from Last Time:
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Time Quantization Analog Signal Reconstruction Smoothing filter removes some of the discontinuities in the output of the zero-order hold Review from Last Time:
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Track and Hold Ф TH OUT IN Review from Last Time:
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Amplitude Quantization Analog Signals at output of DAC are quantized Digital Signals at output of ADC are quantized t Desired Quantized Review from Last Time:
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Amplitude Quantization Unwanted signals in the output of a system are called noise. Movement of carriers in devices Distortion Smooth nonlinearities Frequency attenuation Large Abrupt Nonlinearities Signals coming from other sources Interference from radiating sources Interference from electrical coupling Undesired outputs inherent in the data conversion process itself Review from Last Time:
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Amplitude Quantization How big is the quantization “noise” characterized? Review from Last Time:
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Amplitude Quantization Characterization of Quantization Noise Quantization noise is usually specified in terms of the rms value of the quantization error expressed relative to the LSB For convenience, consider the quantization noise for the following two waveforms that are as large as possible without without exceeding the input or output range of the data converter a) triangle or saw tooth b) sinusoidal
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Amplitude Quantization Characterization of Quantization Noise Quantization noise is usually specified in terms of the rms value of the quantization error expressed relative to the LSB For convenience, consider the quantization noise for the following two waveforms that are as large as possible without without exceeding the input or output range of the data converter a) triangle or saw tooth b) sinusoidal
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Characterization of Quantization Noise Saw tooth excitation 000 001 010 011 100 101 110 111 OUT IN REF Consider an ADC (flash) Assume first transition at X REF /(2 (n+1) )
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Characterization of Quantization Noise Saw tooth excitation X QE t X LSB
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Characterization of Quantization Noise Saw tooth excitation Error waveform:
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Characterization of Quantization Noise Saw tooth excitation Error waveform:
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Characterization of Quantization Noise Saw tooth excitation Error waveform:
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Characterization of Quantization Noise Saw tooth excitation Error waveform: () 2 1 2 1 t QRMS QE t Xx t d t T = Since x QE (t) is periodic, the X QRMS can be obtained by integrating x QE 2 (t) over one period
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Characterization of Quantization Noise Saw tooth excitation () 2 1 2 2 22 2 11 / / t T LSB QRMS QE tT X Xx t d t t d t
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This note was uploaded on 02/01/2012 for the course EE 230 taught by Professor Mina during the Fall '08 term at Iowa State.

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EE 230 Lecture 40 Spring 2010 - EE 230 Lecture 40 Data...

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