Analog-to-digital ConversionandDigital-to-analog Conversion(with DSP)ES-3

A very simple (too simple!)Digital-to-analog converter

A simpleAnalog-to-digital converterscitec.uwichill.edu.bb Analog Input+-

scitec.uwichill.edu.bb Analog InputA simpleAnalog-to-digital converter+-3.5v0v0 0 0 0 0 0 0 0high0 0 0 0 0 0 0 11v0 0 0 0 0 0 1 02v0 0 0 0 0 0 1 13v0 0 0 0 0 1 0 04vlow0 0 0 0 0 0 1 13v0 0 0 0 0 1 0 0Improve accuracy: scale the DAC

Nyquist Sampling RateThe sampling of data must be at least twice the rate as the maximum frequency of the analog signal: fs>2fmaxV(t)Time, tUse a low pass filter with fc = fmax to remove harmonics sine

Nyquist Sampling RateThe sampling of data must be at least twice the rate as the maximum frequency of the analog signal : fs>2fmaxV(t)Time, t

Digital Signal Processing

Running average of 10 pts

Digital FilteringRemoving Noise and Interference from a Digital Signal

FFT of a noisy sine wave and its digitally filtered signal

DSP Example

Simple Notch Filterto remove 60 Hz interferencet (s)Vin(n)fS = 1440 samples per second1/60 s60 Hz sineVout(n) = Vin(n) + Vin(n - fs / 2fnotch) = Vin(n)+Vin(n-12)This adds the sample that is 1800 out of phase at 60 Hz

Matlab demoes3_60Hz.m

Ana