# FFT Low Pass Filter

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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