Tutorial - IPEM 2006

Tutorial on Biomedical Signal ProcessingDavid Simpsonds@isvr.soton.ac.ukOverview of Biomedical Signal ProcessingPre-processingAcquisitionInformationInterpretationextraction2Outline• Sampling• Fourier transforms• Developments and Discussion• Concepts, principles and examples–no maths31Signal Acquisition SystemsAmplifier / Filter(Signal conditioning)ComputerPatient / TransducerADCAnalog-to-digital converter4Digital SignalsWhat are digital signals?1601401201008060 Do we lose information?4020028 28.5 29 29.5 30 30.5 31time (s)113 114 105 99 95 107 145 123 117 108 101 97 101 153 5Analog-to-Digital (A/D) conversionAnalog Input Digital OutputAnti-alias Sampling QuantizationFilter150 150 150 150140 140 140 140130 130 130 130120 120 120 120110 110 110 110100 100 100 10028.5 29 29.5 30 30.5 28.5 29 29.5 30 30.5 28.5 29 29.5 30 30.5 28.5 29 29.5 30 30.562Blood Pressure (mmHg)Sampling TheoremIf the highest frequency contained in a signal is f , and the signal is sampled maxat a sampling rate of f > 2 f , then the s maxoriginal analog signal can be exactly recovered from the samples.Sampling rate > twice the maximum frequency in signal→ No loss of information7Signal Reconstruction(blood pressure)15014013012011010028.5 29 29.5 30 30.58time (s)Aliasing8Hz, sampled at 10 Hz, appears (aliased) as 2 Hz10.5Aliasing cannot (normally) be 0 undone-0.5-10 0.2 0.4 0.6 0.8 1time (s) ...