# Wireless Design Toolkit

This page contains a set of equations and free javascript converters and calculators relevant to designing wireless implimentations. All the scripts are released under the GPL. The frequencies involved are, at the moment, set for 2.44 GHz to fit in line with an 802.11b WLAN (Wireless Local Area Network). With the advent of 802.11g this will be changed to allow the frequencies to be changed.

Back to the top

## Convert inches / millimetres

1 inch = 25.4 mm

 inches millimetres

Back to the top

## Convert circumference / diameter

C = πD

Where:

• C is the circumference of a circle
• D is diameter of a circle
• π is the constant pi =
 diameter circumference

Back to the top

## Convert miles / metres

1 mile = 1609 metres

 miles metres

Back to the top

## Convert feet / metres

1 foot = 0.3048 metres

 feet metres

Back to the top

## Calculate free space loss

FSL = 36.5 + (20 log10(D / 1609)) + (20 log10f)

Where:

• FSL is Free Space Loss in dB
• D is distance between antennas in metres
• f is frequency of signal in Hz
 distance in metres frequency in MHz free space loss in dB

Back to the top

## Wavelength in air

L = c(1 / f)

Where:

• L is wavelength in metres
• c is the speed of light in air 299552816 metres per second
• f is frequency of signal in Hz

Back to the top

## Wavelength in coaxial cable

L = vc(1 / f)

Where:

• L is wavelength in metres
• c is the speed of light in a vacuum 299792458 metres per second
• f is frequency of signal in Hz
• v is the velocity factor of the coaxial cable

Back to the top

## Coaxial impedance

Zo = {138 / sq_rt (E)}log10(D / d)

Where:

• Zo is the characteristic impedance in Ohms
• E is the dialectric constant
• D is the inner diameter of the outer conductor in metres
• d is the diameter of the inner conductor in metres

Back to the top

## Velocity factor

v = 1 / sq_rt (E)

Where:

• v is the velocity factor of coaxial cable
• E is the dialectric constant

Back to the top

## Period of the wave

t = 1 / f

Where:

• L is the period of the wave in seconds
• f is frequency of signal in Hz

Back to the top

## Calculate potential range from maximum FSL at 2.44 Ghz

D = 10((FSL-104.2) / 20)1609

Where:

• FSL is Free Space Loss in dB
• D is distance between antennae in metres
• f is frequency of signal in Hz
 free space loss in dB distance in metres

Back to the top

## Calculate effective radiated power (ERP)

 transmit power in dBm cable losses in dB antenna gain in dBi effective radiated power in dBm effective radiated power in mW

Back to the top

## Calculate system operating margin or fade margin

 transmit power in dBm transmitting antenna gain in dBi(including cable loss) receiving antenna gain in dBi(including cable loss) receiver sensitivity in dBm free space loss in dB fade margin in dB

Back to the top

## Convert milliWatts / dBm

milliWatts = 10(dBm/10)

 power in mW dBm

Back to the top