Quantifying Phase Margin Loss from Cascaded Sinc and Boxcar Filter Window Delay
Cascaded sinc and boxcar filter window delays introduce deterministic group delays that subtract directly from control loop phase margin at crossover frequencies.
Sample Rate Reduction
Decimation Process
Signal processing techniques decrease the number of data points collected or retained per unit of time from a continuous measurement. In digital systems, sample rate reduction is used to lower the storage requirements and the computational load of a monitoring task. This process must be handled carefully to avoid the loss of important high frequency information.
It is a common step when transferring data from a high speed sensor to a lower bandwidth logging device.
Aliasing Prevention
The procedure usually involves filtering the original signal to remove any frequencies above the new Nyquist limit. Without this filtering, sample rate reduction would cause aliasing, where high frequency noise appears as a low frequency phantom signal. Digital filters, such as finite impulse response filters, are typically employed to smooth the data before the extra points are discarded.
This ensures that the remaining samples accurately represent the trends in the original high speed stream.
Data Efficiency
Reducing the amount of data allows for longer recording times on devices with limited memory. For a sensor monitoring a slow process like thermal expansion, a high sample rate is unnecessary and generates redundant information. By implementing sample rate reduction, engineers can focus on the major changes while ignoring the millisecond to millisecond fluctuations that are just noise.
This efficiency is essential for battery powered remote sensors that must conserve energy by transmitting as little data as possible. The choice of the final rate depends on the fastest event that the user needs to capture.
Reconstruction Fidelity
Comparisons between the original and the reduced data sets confirm that no critical features have been lost. This verification step ensures the integrity of the measurement for later analysis.