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Daniel Muey > Math-FresnelZone-0.03 > Math::FresnelZone
Module Version: 0.03

# NAME

Math::FresnelZone - Perl extension for calculating the Fresnel Zone Radius of a given distance and frequency

# SYNOPSIS

```  use Math::FresnelZone;
use Math::FresnelZone qw(fresnel fresnelMi fresnelKm);```

# DESCRIPTION

The arguments are:

```   0 - distance in kilometers or miles (default is 1),
1 - frequency in GHz (defualt 2.4),
2 - set to true to specify that the distance you are inputting is in miles and that the results should be in in feet (default is 0 - IE kilometers/meters)```

## fresnel()

```   my \$fresnel_zone_radius_in_meters = fresnel(); # fresnel zone radius in meters for 1 kilometer at 2.4 GHz
my \$fzr_in_meters = fresnel(5); # fresnel zone radius in meters for 5 kilometers at 2.4 GHz
my \$fzr_in_meters = fresnel(5,4.8); # fresnel zone radius in meters for 5 kilometers at 4.8 GHz
my \$fzr_in_feet = fresnel(3,9.6,1); # fresnel zone in feet for 3 miles at 9.6 GHz```

If you are inputting Kilometers the result is in meters (these 3 calls have identical results):

```   fresnel(\$Km,\$GHz);
fresnelKm(\$Km,\$GHz); # see documentaion below for info about fresnelKm()
fresnel(\$Km,\$GHz,0);```

If you are inputting Miles (by specifying a true value as the 3rd argument) the result is in feet (these 2 calls have identical results)

```   fresnel(\$Mi,\$GHz,1);
fresnelMi(\$Mi,\$GHz); # see documentaion below for info about fresnelMi()```

## fresnelKm()

You can use this to make it easier to avoid ambiguity if are working in kilometers/meters. It takes the first two arguments only: distance in kilometers and frequency in GigaHertz

` my \$fzr_in_meters = fresnelKm(\$Km,\$GHz);`

## fresnelMi()

You can use this to make it easier to avoid ambiguity if are working in miles/feet. It takes the first two arguments only: distance in miles and frequency in GigaHertz

` my \$fzr_in_feet = fresnelMi(\$Mi,\$GHz);`

## EXPORT

None by default. You can export any of the 3 functions as in the synopsis example.

## VARIABLES

These variables are used when using miles/feet instead of kilometers/meters to modify the input for the formula and the output for the user:

```   \$Math::FresnelZone::KILOMETERS_IN_A_MILE  (Default is 1.609344)
\$Math::FresnelZone::FEET_IN_A_METER (Defualt is 3.280839)```

Feel free to change them if you need more or less than six decimal places and/or want really inaccurate results :)

To find out more about the fresnel zone (pronounced fray-NELL) you can google the man who this formula/zone is named after to learn more: Augustin Jean Fresnel.

Mr. Fresnel was a French physicist who supported the wave theory of light, investigated polarized light, and developed a compound lens for use in lighthouses (IE the "Fresnel lens") (1788-1827).

Also googling the phrase "Fresnel Zone" turns up some interesting glossary refernces to what the fresnel zone is.

Here is a link to an image illustrating what a fresnel zone is and the formula: http://drmuey.com/images/fresnelzone.jpg

# AUTHOR

Daniel Muey, http://drmuey.com/cpan_contact.pl