Inside Wireless: Nearfield vs Farfield
Nearfield and Farfield are two distinct regions around an antenna, where the antenna’s radiation properties differ significantly. In this episode of Inside Wireless, you’ll learn why Nearfield and Farfield regions are important to understand, when designing your wireless networks.
Take a look at other Inside Wireless episodes here:
https://www.youtube.com/playlist?list=PLii-eQuaf57ocpSGH6NR8IKtJvB9mb81h
Farfield region, also known as the radiation field, or the Fraunhofer region, is the region far away from the antenna, where the electromagnetic waves have fully developed and exhibit a simple predictable behavior. They propagate as planar waves with the electric and magnetic fields perpendicular to each other.
The Farfield region is defined by the wavelength of the signal (λ) and the size of the antenna (D).
Farfield equation: 2*D²/λ.
Examples of Farfield region:
· 30° Symmetrical Horn antenna operating at 5.5 GHz – Farfield region starts at 2 meters and extends to infinity,
· 24 dBi gain Dish antenna – Farfield region starts at 6 meters and extends to infinity,
· 20 dBi Patch Array Sector – Farfield region starts at 20 meters and extends to infinity.
On the other side closest to the antenna we have the Reactive Nearfield region. This is a place of electromagnetic chaos. Any objects inside this region cause unpredictable changes to the antenna’s radiation diagrams and VSWR, because it becomes a part of the antenna itself.
Nearfield equation: 0.62*(D³/λ)½.
Examples of Reactive Nearfield region:
· 30° Symmetrical Horn antenna operating at 5.5 GHz – Reactive Nearfield region from 0 to 0.3 meters,
· 24 dBi gain Dish antenna – Reactive Nearfield region from 0 to 0.7 meters,
· 20 dBi Patch Array Sector – Reactive Nearfield region from 0 to 2 meters.
Maintaining a Reactive Nearfield free of obstacles is much simpler with antennas with small form factors, enabling much denser colocation.
And finally, the Radiative Nearfield is the region in the middle. The electromagnetic fields have not yet consolidated into their Farfield structure but anything placed in this region is far enough not to have a direct influence on the antenna’s performance.
https://rfelements.com/
00:00 – What is Nearfield & Farfield
00:24 – Farfield Region
00:55 – Farfield Region Examples
01:11 – Reactive Nearfield Region
01:31 – Reactive Nearfield Region Examples
01:55 – Radiative Nearfield Region
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