Finite Wordlength EffectsChallenge 04Lesson 05 Data Acquisition SurveyQtitiEQuantization ErrorsChallenge 05What’s the deal?• How are continuous time signals quantized?• What is a quantization error?• How can quantization errors be computed?• How can quantization errors be interpreted?Lesson 05Challenge 04YkitltidiPC d ih di tiiYou are working at your multimedia PC doing some hedonistic voice recordings with a pirated copy of MATLAB’s audio suite, sampling at 8kSa/s. Your dog “Killer” is asleep at your feet. You decide that it’s time to feed Killer and head to the kitchenYou are amazed that even though youfeed Killer and head to the kitchen. You are amazed that even though you heard nothing, as soon as you remove the pull-top tab on the dog food can cover, Killer is standing right next to you. Upon returning to you PC you find out you left the record button on. You listen to the recorded sounds and find out that there is a detectible 3kHz tone which, when played, sounds like the slow weird tearing of a pull-top. What frequency (most probably) did Killer hear?(Assume you can hear out to 15kHz)Lesson 05Challenge 04Althtiithitilh tliiAnalyze the question using the unit circle approach to aliasing.Given fs=8000 Sa/sDid Killer hear the basaeband 3000Hz signal?3000Yes, but you would have head this too.4000, …0, 8000, …Lesson 05Challenge 04Gif8000 S /Given fs=8000 Sa/sDid Killer hear the non-baseband sources mapped to 3000Hz?3000Yes but you would have head them too-5000, 11000, -13000?4000, …Yes, but you would have head them too.0, 8000, …Lesson 05Challenge 04Gif8000 S /Given fs=8000 Sa/sWhat about 19000Hz?Yld ’t hhd3000You wouldn’t have heard it but Killer did.19000 = 16000 + 30004000, …0, 8000, …Lesson 05Typical Data Acquisition SystemRemember Shannon’s sampling theorem applies to the Remember, Shannon s sampling theorem applies to the discrete-time portion of this system.The digital portion introduces errors called quantization errors The digital portion introduces errors, called quantization errors. The DSP engineer needs to be able to quantify these errors. Lesson 05Data ConversionBut first, an Analog to Digital surveyADC overviewADC typesADC enhancementsToday’s DSP solutions are ADC – bound and not compute – bound!Lesson 05Data ConversionAnti-aliasing filterPractical ADC system with programmable conversion rates.Lesson 05ADC TypesDelta-sigma() converter.Loope(t)FilterLesson 05
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