FIR Filter

FIR (Finite Impulse Response) filters are implemented by sampling the sinc(x) function and windowing it with a Blackman window. Filtered signals are computed by convolution. The size of the impulse response is two seconds (relative to the sampling rate of the signal to be filtered), or at least 256 samples. If the notch (powerline) filter is also enabled, then another (band reject) filter is cascaded, with the same characteristics of the previous one.

"Windowed-sinc filters are used to separate one band of frequencies from another. They are very stable, produce few surprises, and can be pushed to incredible performance levels. These exceptional frequency domain characteristics are obtained at the expense of poor performance in the time domain, including excessive ripple and overshoot in the step response. When carried out by standard convolution, windowed-sinc filters are easy to program, but slow to execute."

From "The Scientist and Engineer's Guide to Digital Signal Processing", By Steven W. Smith, Ph.D.

Created with the Personal Edition of HelpNDoc: Full featured multi-format Help generator