Calculating Group Delay in Delta Sigma Converters
Delta-sigma converter group delay equals the phase derivative across decimation filter stages, calculated as K times M minus one divided by twice the modulator clock for sinc filters.
Droop Compensation Fir
Passband Correction
Digital signal processing component designed to flatten the amplitude response of a preceding filter stage. A droop compensation fir filter counteracts the natural roll off observed in sinc filters or decimation stages. It applies an inverse gain profile to the signal to ensure a uniform response across the bandwidth of interest.
Implementation Logic
Coefficient selection for these stages focuses on the inverse of the sinc function over the frequency range. A droop compensation fir usually operates at the final output rate of a decimation chain to correct cumulative errors. Hardware designers must balance the number of taps against the tolerable latency, as more coefficients provide a flatter passband but increase the processing delay.
Accuracy Impact
Accuracy in analog to digital conversion relies on this correction to maintain gain accuracy within fractions of a decibel. Without a droop compensation fir, measurements near the edge of the passband would report lower values than the actual input signal. This attenuation typically reaches several decibels at the half power point if left uncorrected.
Calibration Verification
Calibration confirms the effectiveness of the filter by sweeping a reference tone. Results of this test prove that the droop compensation fir maintains the target flatness within the specified temperature range.