Calculating Equivalent Noise Bandwidth and Flicker Corner Integration in AFEs
Calculating AFE noise requires integrating white floor spectral density across equivalent bandwidth while summing flicker contributions over the measurement duration.
Bessel Filter
Phase Response
Analogue signal processors designed for linear phase response across the passband provide flat group delay and preserve pulse shapes in time-domain measurements. The bessel filter belongs to this category, offering a transfer function that optimises phase linearity at the cost of a less steep roll-off. In transient analysis, this characteristic prevents the distortion of rapid steps.
Frequency Attenuation
Frequency domain selection is often limited by a trade-off between roll-off rate and step response. While Chebyshev designs offer sharper attenuation, a bessel filter provides a gradual transition from passband to stopband. This behavior ensures that high-frequency noise is attenuated without introducing artificial fluctuations into the measured step.
Group Delay
Propagation delay across the passband determines how well a system preserves complex waveforms. For a bessel filter, the phase shift is proportional to frequency, yielding a constant group delay that prevents signal dispersion.
Calibration Variance
Metrological verification of active filters relies on measuring phase shift across a swept frequency spectrum. Because the bessel filter operates with smooth transition curves, component tolerance variations of even five percent can shift the corner frequency without causing passband ripple. High-precision resistors and capacitors are required to maintain calibration stability under shifting temperatures.