ADC anti alias filter
ADC anti alias filter with computed response and explicit circuit realisation.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Alias stop edge: fstop = fs − fpass
Half-LSB rejection: Astop = 20 log10(Ainterferer × 2^(N+1))
Butterworth order: n ≥ log10[(10^(As/10)−1)/(10^(Ap/10)−1)]/[2 log10(fs/fp)]
Chebyshev order: n ≥ acosh(√[(10^(As/10)−1)/(10^(Ap/10)−1)])/acosh(fs/fp)
Assumptions
- The interferer amplitude is relative to ADC full scale. Passband droop and nearest-image attenuation define the minimum ideal order. Bessel order is searched from computed −3 dB prototypes. Actual component/driver/ADC responses must be included before hardware sign-off.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Sampling frequency
- 48000 Hz
- Passband edge
- 10000 Hz
- ADC target bits
- 12 bits
- Out-of-band input / full-scale amplitude
- 1
- Allowed passband attenuation
- 0.5 dB
- Prototype
- butterworth
Results
- Minimum order
- 8
- Required corner or ripple-edge frequency
- 11405.1 Hz
- First alias stopband edge
- 38000 Hz
- Required rejection
- 78.2678 dB
- Rejection at alias edge
- 83.6296 dB