Calculate CBV from maximum frequency shift

This method calculates the capillary blood cell velocity (CBV) by finding the maximum frequency component in the power spectrum which is stronger than the threshold value.

This method detects the envelope of the Doppler Shift and is best for signals without a strong peak, perhaps due to not being directly above a perpendicular section of capillary, or where the is a sharp bend in the capillary at the measurement site, or where there are many gaps between blood cells or aggregates of cells.