Conversions between electric field strength (E), magnetic field strength (H) and power density (S).

Picture of an EM field (power density S) being received by an antenna (gain G) with power P_r

P_r = A_e S                 A_e = g * lambda^2 / (4 pi)                 f = c_0 / lambda                 c_0 = 3 * 10^8 m/s
E = Z_0 H                 S = E^2 / Z_0 = Z_0 H^2                 Z_0 = 120 pi = 377 Ohm
Frequency:f = Hz
Antenna gain:G = dBi
Received power:Pr = dBm
pr = W
Electric field strength:E = V/m
Magnetic field strength:H = A/m
Power density:S = W/m2

Enter the frequency f, the gain G and one value (either pr, Pr, E, H or S) and click the "Convert" button next to it to compute the four other values.

En electromagnetic filed with a power density of S [W/m2] in its far field region is received by an antenna of gain G [dB] and a certain power Pr [W] is measured on the antenna connector.

The losses of the antenna and of the cable can be taken into account with an appropriate antenna gain G. The antenna impedance has to be matched with the cable and the receiver.

Bibliography:

C.-A. Balanis, Antenna theory, analysis and design Wiley, 1997, chapter 2.

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