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Antenna Factor Calculator

Antenna Factor Calculator

This tool calculates the Antenna Factor (AF) from the Antenna Gain (G) and Frequency of operation (f).

Antenna Factor to Gain Calculator

Formula

AF = 20*Log10(9.73/(Îŧ√G))

where,

Îŧ = c/f

c is the speed of light, f is the operating frequency and Îŧ is the wavelength.

G is the linear value of Antenna Gain relative to that of an isotropic antenna.

How to use the Calculator

Enter

  • Antenna gain (in dBi) – this is typically provided by manufacturers in the data-sheet
  • Frequency of operation (in MHz)

Example calculation: for a gain of 8 dBi and frequency of 915 MHz, the Antenna Factor is 21.50 dB/m.

Increasing the antenna gain to 12 dBi at the same frequency gives a lower value of AF = 17.5 dB/m

Background

Antenna Factor is the ratio of the electric field E (units: V/m or ΞV/m) to the voltage V (units: V or ΞV) induced across the terminals of an antenna. It is a measure of how much energy is captured by the antenna.

For a fixed value of E, a higher Antenna Factor implies a smaller effective voltage. This translates to a lower antenna gain in dBi.

The units are dB-per-meter or dB/m.

Notes

The equation for Antenna Factor takes the effect of impedance mismatch into account and only applies under the following conditions

  • When the receiving antenna is in the far field of the transmitter
  • Impedance is 50 ohm
  • Antenna and incident field is matched in terms of polarization