What is the Antenna Near Field & Far Field Distance Calculator? 

Antenna Near Field & Far Field Distance Calculator is an online tool used to calculate reactive near field distance, radiating near field distance (Fresnel region), and the far field distance by inputting antenna dimension (length or diameter in meters) and operating frequency. The calculator uses the following formulas: 

Where, 

D = Antenna dimensions (Can be the length or diameter of the antenna) 

f = Signal Frequency 

λ = Wavelength 

Understanding reactive near field distance, radiating near field distance (Fresnel region), and the far field distance: 

An antenna is a metallic structure that transmits or receives electromagnetic waves by converting electrical signals into radio waves and vice versa. Antennas are used in applications such as EMC testing and wireless communications. When operating in transmitting mode, the area or region surrounding an antenna is divided into three regions: reactive near-field region, radiating near-field region (Fresnel region), and far-field region. Let’s understand these regions. 

Reactive near-field region: This is the region or area very close to the antenna where, depending on the antenna type, either the electric or magnetic field is dominant, and there is no significant electromagnetic radiation. For example, in a loop antenna, the magnetic field is dominant in the reactive near-field region. 

Radiating near-field region (also known as Fresnel region): This is the region or area near the antenna where the transition of the electromagnetic field from reactive to radiative begins. This region located in between the reactive near-field and far-field regions. 

Far-field region (Fraunhofer region): This is the area or region far from the antenna where the electromagnetic field is radiated and propagates as a plane wave.  In this area, the electric and magnetic fields are perpendicular to each other as well as perpendicular to the direction of wave propagation. The far-field region exhibits stable radiation characteristics, with the radiation pattern no longer changing with distance. This region is immediate to the radiating near-field region (for electrically large antennas) or immediate to the near-field region (for electrically small antennas where antenna dimension D < λ / 2).