ZLPFILT

Purpose:

Performs low pass filtering by zeroing the FFT values.

Syntax:

ZLPFILT(series, fc, mask)

series

-

Input series to filter.

fc

-

Optional. A real, the low pass cutoff frequency. Defaults to rate(series)/10.

mask

-

Optional. An integer, return the frequency domain mask only. Defaults to 0, return processed input.

Returns:

A series, the low pass filtered output.

Example:

W1: gsin(1000, 1/1000, 20) + gsin(1000, 1/1000, 1)

W2: zlpfilt(w1, 10)

 

W1 contains a 1 Hz sinewave with 20 Hz high frequency sinusoidal noise.

W2 filters out the noise an returns the 1 Hz sinusoidal component.

Remarks:

ZLPFILT performs low pass filtering by zeroing out the high frequency components of the FFT of the input. FFT zeroing is a crude but fast filtering operation. However, the pass band and transition edge of the equivalent filter will exhibit significant ripple.

 

 

 

For a flatter response, use traditional filter design methods such as those offered by DADiSP/Filters.

  

If fc < 0, no filtering is performed.

 

If mask == 1, the frequency domain binary mask used to zero out the stop band frequencies is returned.

 

See ZHPFILT for a high pass filter.

See Also:

DADiSP/Filters

FFT

FINTEG

LOWPASS

ZBPFILT

ZBSFILT

ZHPFILT