The Kaiser-Bessel window coefficients are given by the following formula

where N is the length of the filter and k = 0, 1, …, N – 1.

Consider a finite impulse response (FIR) low pass filter of length N = 201. The following is the Kaiser-Bessel window.

Given a sampling frequency of 2000 Hz and a filter cutoff frequency of 40 Hz, the impulse response of the filter with a rectangular window (with no window) and with the Kaiser-Bessel window is as follows.

The magnitude response of the same filter is shown on the graph below.

## Measures for the Kaiser-Bessel window

The following is a comparison of the discrete Fourier transform of the Kaiser-Bessel window and the rectangular window.

The Kaiser-Bessel window measures are as follows.

Coherent gain | 0.40 |

Equivalent noise bandwidth | 1.80 |

Processing gain | -2.55 dB |

Scalloping loss | -1.02 dB |

Worst case processing loss | -3.57 dB |

Highest sidelobe level | -65.3 dB |

Sidelobe falloff | -11.8 dB / octave, -39.3 dB / decade |

Main lobe is -3 dB | 1.70 bins |

Main lobe is -6 dB | 2.40 bins |

Overlap correlation at 50% overlap | 0.072 |

Amplitude flatness at 50% overlap | 0.608 |

Overlap correlation at 75% overlap | 0.537 |

Amplitude flatness at 75% overlap | 1.000 |

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