Configuring Moving Average Filter Lengths for Decimated Signal Processing
Matching moving average filter length to the decimation factor eliminates alias leakage by placing transfer function zeros directly on downsampling fold points.
Dither
Noise Injection
Signal conditioning uses the deliberate addition of random noise to sub-unit digital samples to mask quantization errors. Engineers apply dither during analog-to-digital conversion to randomize the truncation errors that occur when analog voltages are mapped to discrete digital codes. The technique shifts harmonic distortion into a wideband noise floor, which improves the dynamic performance of the acquisition system.
Quantization Resolution
Noise of specific amplitude must be added to the raw signal prior to digitization to achieve effective resolution below the least significant bit. When the amplitude of the added dither matches a fraction of the quantization step, the system can resolve signals otherwise lost in the digitization threshold.
Linearization Performance
System linearity rises when quantization errors become statistically independent of the input signal. Randomizing the error prevents the formation of spurious spectral lines that can otherwise degrade sensor measurements. In precision instrumentation, a Gaussian probability density function often models the noise distribution to optimize the trade-off between the total noise power and the suppression of spurious tones.
The resulting signal displays a higher spurious-free dynamic range at the cost of a slightly elevated background noise level. Precision analog circuits rely on this trade-off to measure fine transitions in physical signals such as pressure variation and seismic displacement.
Calibration Uncertainty
Metrological calibration ensures the injected noise maintains a stable root-mean-square amplitude across the operational temperature range. If the noise source drifts, the linearization benefit decreases and introduces unpredictable distortion in the measurement data. Verification occurs at the factory by analyzing the noise density of the digital output when the input is grounded.