Antenna Near Field Calculator

Enter your Antenna Dimension (D) and Frequency (f) into the Antenna Near Field Calculator to find the Far Field Distance where your antenna's radiation pattern fully forms, along with the Wavelength, Reactive Near Field Distance, and Radiating Near Field Distance — so you know exactly which electromagnetic zone you're operating in.

m

Largest antenna dimension (length or diameter)

Operating frequency of the antenna

Results

Far Field Distance

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Wavelength

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Reactive Near Field Distance

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Radiating Near Field Distance

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Antenna Field Regions

Frequently Asked Questions

What is the difference between near field and far field regions?

The near field region is close to the antenna where the electromagnetic field is reactive and complex. The far field region is where the field becomes purely radiative and the antenna pattern is well-defined. The transition depends on antenna size and wavelength.

How do I determine the largest antenna dimension?

For linear antennas, use the physical length. For dish antennas, use the diameter. For array antennas, use the largest overall dimension of the entire array structure.

What is the reactive near field distance?

The reactive near field extends from the antenna surface to a distance of λ/(2π). In this region, the electromagnetic field is predominantly reactive and energy storage dominates over radiation.

What is the radiating near field (Fresnel region)?

The radiating near field or Fresnel region extends from the reactive near field to 2D²/λ. In this region, the radiation pattern depends on distance and the field is transitioning from near field to far field characteristics.

Why is the far field distance important?

The far field distance (greater than 2D²/λ) is where antenna measurements should be taken for accurate pattern characterization. Beyond this distance, the antenna pattern is independent of measurement distance.

How does frequency affect field regions?

Higher frequencies result in shorter wavelengths, which typically reduce the distances of all field regions. Lower frequencies extend these regions further from the antenna.

What happens for electrically small antennas?

For antennas where D < λ/2, there are only two regions: near field and far field. The radiating near field region effectively doesn't exist for electrically small antennas.

Can I use this calculator for any type of antenna?

Yes, this calculator applies to all antenna types including dipoles, patches, dishes, arrays, and horns. Just use the largest physical dimension of your specific antenna.

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