FFT Low Pass Filter

This block is a convenience wrapper for the FFT Filter. It implements a lowpass filter using the fast Fourier transform (FFT).

Parameters

(R): Run-time adjustable

Gain

Multiplication factor at the output of the filter. Default: 1

Sample Rate

Default: "samp_rate"

Cutoff Freq

The cutoff frequency (roughly the 3 dB point) of the filter's impulse response.

Transition Width

The frequency difference between the filter's passband and stopband. The ratio of the transition width divided by the sample rate, combined with the window, sets the number of required taps for the filter.

Window

The filter is a basic windowed-sinc filter. This sets the window used. Possible windows are Hamming, Hann, Blackman, Rectangular, Kaiser. Default: Hamming

Beta

This is the value used for the Kaiser window. If any other window is selected, this value is ignored.

Example

This flowgraph filters and demodulates the audio from the US NOAA Weather Radio service. The FFT Low Pass Filter block filters out each signal individually in preparation for demodulation.

Source Files

C++ files

None

Header files

None

Public header files

None

Block definition

filter_fft_low_pass_filter.block.yml