Two kinds of statistics are computed on the ADC data [2]. These are:

• The sum of absolute values of the adc data, $absSum= \sum _{i= 1}^N\left(x_i\right)$ where x_i corresponds to the adc samples in the chirp.
• The sum of the first difference of adc data, $diffAbsSum = \sum _{i= 2}^N\left(x_i-x_{i-1}\right),$ .

These are then scaled down to generate means, and then scaled up to generate two thresholds (AbsThreshold and AbsDiffThreshold).

The abs-diff filters suppress the low-frequency tone and help make the glitch more visible.

Figure 3-3 Detecting Outliers Using Abs and Abs-diff Filters

The advantage of calculating the first difference is that it suppresses low-frequency reflections like the bumper reflection or the antenna coupling effect, allowing weaker glitches to be easily found.