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Half Power Beamwidth Coverage Calculations

Half-Power Beamwidth Coverage Calculations — EMC Tool

Half Power Beamwidth Coverage Calculations

Enter antenna half-power beamwidth and separation distance to compute product coverage at the measurement plane.

Coverage is computed from the antenna half-power beamwidth (3 dB beamwidth) and the separation distance. The diagram updates when you press Calculate.

Calculations

Inputs: Beamwidth (deg), Distance (m)
Product Coverage
— meters
Animated setup (amplifier → cable → antenna → RF field → measurement plane) —° beamwidth • — m distance
OUTSIDE WORLD ANECHOIC CHAMBER AMPLIFIER ANTENNA RF FIELD MEASUREMENT PLANE — —
The cone shows the half-power beamwidth boundaries (±BW/2) and the green arrow shows product coverage at the measurement plane.
Formulas
\[ \text{Coverage} = 2\,D\,\tan\!\left(\frac{\theta}{2}\right) \] \[ \theta = \text{Half-Power Beamwidth (degrees)},\quad D=\text{Separation Distance (meters)} \] \[ \theta_{\mathrm{rad}}=\theta\cdot\frac{\pi}{180} \]

Applications, Resources, Definitions

RF immunity testing guidance

Applications

During RF immunity testing, the product is subjected to a specific RF field strength (say 10 volts per meter) for a fixed dwell time and over a series of predetermined spot frequencies. If the half-power beamwidth of the antenna is not large enough to cover the equipment under test, then one of the following should be performed:

  • Conduct multiple tests at locations along the EUT.
  • Use a greater separation distance (if allowed).
  • Perform the test with an antenna that has a larger half-power beamwidth.

Definitions

Half-Power Beamwidth is the angular distance on either side of the peak field, or main lobe, of the antenna that represents half of the peak field intensity. Half the power is equivalent to −3 dB, so the half-power beamwidth is also sometimes referred to as the 3 dB beamwidth.

Separation Distance is the distance from the antenna to the product under test.

Resources: Use this calculator to check whether your antenna’s half-power beamwidth can cover the EUT at the chosen distance.

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