Anti-Aliasing Filter Design - PowerPoint PPT Presentation

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Anti-Aliasing Filter Design

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  1. Anti-Aliasing Filter Design

  2. Sampling Process Analog Signal Sampling Interval (Ts) Sampled Numbers

  3. Analog-to-Digital Conversion Analog Discrete Digital

  4. Undersampling or Aliasing Undersampling results in a form of distortion termed as aliasing. http://www.dsptutor.freeuk.com/aliasing/AliasingDemo.html

  5. Anti-Aliasing Filter Design

  6. Anti-Aliasing Filter Implementation

  7. Anti-Aliasing Filter Design Signal of Interest : DC to 1 KHz Analog-to-Digital Converter : 12 bits SAR Sampling Rate : 20 kHz  Nyquist Rate : 10 kHz Anti-Aliasing Filter Goal : To filter signals such that high frequency for the analog input do not pass through the A/D Converter.

  8. fsamp fnyq fcutoff Targeted Attenuation Level to prevent aliasing.

  9. fsamp fnyq fcutoff Targeted Attenuation Level to prevent aliasing. 12 bit ADC  212 = 4096 levels Dynamic Range = 20 * log (#levels)  72.3 dB

  10. Anti-Aliasing Filter Design Signal of Interest : DC to 1 KHz Analog-to-Digital Converter : 12 bits SAR Sampling Rate : 20 kHz  Nyquist Rate : 10 kHz Anti-Aliasing Filter Goal : To filter signals such that high frequency for the analog input do not pass through the A/D Converter.

  11. Anti-Aliasing Filter Design 5th Order Bessel

  12. 5th Order Bessel

  13. Anti-Aliasing Filter Design 3rd Order Chebyshev

  14. 3rd Order Chebyshev

  15. Anti-Aliasing Filter Design 4th Order Butterworth

  16. 4th Order Butterworth

  17. Homework: EEG Amplifier Design Input: 0.1 – 100 Hz Pass-band (switchable to DC-100 Hz) 25 – 100 uV signal levels Differential input CMRR >100 dB Output: Goes to ADC +/- 5 volt Range sampling at 1 kHz rate