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Tool 05

Antenna Far-field Measurement

Check Fraunhofer distance, allowable AUT size, and measurement-distance margin for far-field antenna testing.

Parameters

Enter frequency, maximum AUT size, and available measurement distance. Adjust the Fraunhofer factor only when your test standard requires a different far-field criterion.

Frequency
Maximum AUT Size D
Measurement Distance R
Advanced Settings
Criterion Factor K
×D²/λ

The common Fraunhofer condition is R ≥ 2D²/λ, so the default value is 2.

Sweep Graph

Custom Data Step applies to Linear X scale; Log X uses automatic logarithmic points.

Reference Values

Frequency [GHz]
10.000
AUT Size
1.000 m
Measurement Distance
10.000 m
Wavelength [mm]
29.979
Criterion Factor K
2.000

Formulas

Wavelength

Calculate free-space wavelength from frequency.

λ=cf\lambda = \frac{c}{f}

Far-field Distance

Fraunhofer far-field condition distance for AUT maximum dimension D.

Rff=KD2λR_{ff} = K\frac{D^2}{\lambda}

Max AUT Size

Calculate the maximum AUT size that satisfies the far-field condition at a given measurement distance.

Dmax=RλKD_{max} = \sqrt{\frac{R\lambda}{K}}

Far-field margin

Indicates how much margin the actual measurement distance has over the required far-field distance. Values of 1 or higher satisfy the condition.

M=RRffM = \frac{R}{R_{ff}}

The default K=2 corresponds to the common Fraunhofer condition R ≥ 2D²/λ.