This calculator determines the distances of the reactive near field, radiant near field (Fresnel region) and far field zones of an antenna based on its size and the frequency of the signal. It helps to understand the behavior of radiation and plan electromagnetic measurements or simulations accurately.
It is useful for RF engineers, antenna designers, and students studying electromagnetic propagation and antenna performance at different distances.
Formulas
λ = c/f
Reactive near field: R NF = 0.62 × √(D³ / λ)
Radiating near field (Fresnel region): R Fresnel = 2 × D² / λ
Far field: R FF = 2 × D² / λ
Explanation of formulas
- it is the speed of light (3 × 10⁸ m/s).
- f is the operating frequency in hertz (Hz).
- D is the largest dimension of the antenna (meters).
- The formulas help identify at what distance radiation becomes stable and predictable.
Far field for a 1 m antenna at 3 GHz
Input : D = 1 m, f = 3 GHz
Output : R FF ≈ 20 meters
Benefits and uses
- Defines field areas for precise antenna measurements.
- Useful for the design and validation of RF and microwave antennas.
- Helps avoid interference during anechoic chamber testing.
- Allows you to better understand the propagation and measurement limits of an electromagnetic field.