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Bomem-GRAMS User's Guide

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Appendix A<br />

Apodization Functions<br />

Name and description Function FWH<br />

H (%)<br />

Cosine<br />

Small side lobes, although with appreciable<br />

ripple; intermediate half-width.<br />

Hamming (Happ-Genzel)<br />

Small side lobes, although with appreciable<br />

ripple; intermediate half-width.<br />

Blackman-Harris<br />

Extremely small side lobes; large half width.<br />

Gaussian<br />

Monotone decreasing function with no ripple<br />

(minor ripple due to finite length).<br />

( cosπD)<br />

SLAM<br />

(%)<br />

0 .5 + 0.5<br />

91 0.71<br />

( cosπD)<br />

0 .53856 + 0.46144<br />

91 0.71<br />

0 .42323 + 0.49755( cosπD)+<br />

0.07922(cos 2π D)<br />

116 0.04<br />

e<br />

2<br />

-3.91202300543D<br />

75 0.1<br />

Norton Beer weak* 2<br />

0.548<br />

− 0.08331 ( − D )+ 0.5353(1<br />

− D<br />

2 ) 2 72 5.8<br />

Norton Beer medium* 2<br />

0.261−<br />

0.1548381 ( − D )+ 0.894838(1<br />

− D<br />

2 ) 2 84 1.4<br />

Norton Beer strong* 2 2<br />

0.09 + 0.5875( 1−<br />

D ) +<br />

0.3225(1<br />

− D<br />

2 ) 4<br />

97 0.3<br />

* Functions taken from the article New Apodization Functions for Fourier Spectrometry by Robert H. Norton and<br />

Reinhard Beer, J. Opt. Soc. Am., Vol. 66, No. 3, March 1976, pp. 259-264.<br />

These functions are an attempt to provide optimum apodizing functions of algebraic form that provide the smallest<br />

degradation in resolution for a specified reduction in side lobe intensity.<br />

Although these three functions provide optimum performance in terms of FWHH/SLAM ratio, they have the drawback of<br />

exhibiting very slow damping of the side lobe features (large ripple), which is often undesirable.<br />

32 <strong>Bomem</strong>-<strong>GRAMS</strong> <strong>User's</strong> <strong>Guide</strong>

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