Antenna Calculations

The following is a list of various antenna calculations should you find it necessary to convert from one parameter to another:

Conversion of signal levels from watts to volts in a 50 ohm system:

where:

P = power in Watts , V = voltage level in Volts, and R = resistance in ohms

Note that 1mW = 10–3 W and 1µV = 10–6 V.

For power in dBm, and voltage in dB (µV):

Power density to field strength:

An alternate measure of field strength is power density:

where:

E is the field strength in V/m and Pd is the Power density in W/m2

Power density at a point:

where:

Pd = power density in W/m

Pt = power transmitted in Watts

Gt = gain of transmitting antenna

r = distance from the antenna in meters

Pt = power transmitted in Watts

Gt = gain of transmitting antenna

r = distance from the antenna in meters

This equation is only valid in the far field, where electric and magnetic fields are related by the characteristic impedance of free space.