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What is antenna beamwidth?

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Half-power beamwidth (HPBW) is, in a plane containing the direction of maximum radiation, the angle between the two directions in which the radiation intensity is one-half the maximum.[1] Beamwidth is inversely proportional to aperture size in wavelengths; for a dish, HPBW ≈ 70λ/D degrees.[2]

What are typical beamwidths?

AntennaHPBW
Hertzian dipole (E-plane)90°
Half-wave dipole (E-plane)78°
Uniform line source length L≈ 50.8λ/L degrees
Parabolic dish diameter D≈ 70λ/D degrees (tapered illumination)
Uniform linear array, broadside≈ 0.886λ/(Nd) rad

Sources: Balanis; Stutzman and Thiele.[3][2]

What is first-null beamwidth?

First-null beamwidth (FNBW) is the angular separation between the first nulls either side of the main beam. For a uniform line source FNBW ≈ 2λ/L rad, roughly 2.25 times the HPBW.[3]

How does beamwidth relate to gain?

Directivity scales inversely with the product of the two principal-plane beamwidths: D ≈ 41,253/(θEθH) for an idealized single beam.[4] Halving both beamwidths quadruples directivity (+6 dB). Amplitude tapering lowers sidelobes but broadens the beam; see array tapering.

Why does a phased array beam broaden when scanned?

The projected aperture shrinks by cos θ0, so the HPBW of a scanned array grows roughly as 1/cos θ0 until near endfire.[5] See beam steering.

Frequently asked questions

What is a 3 dB beamwidth?

Another name for half-power beamwidth.

What beamwidth does a 60 cm dish have at 10 GHz?

About 70 × 0.03/0.6 ≈ 3.5°.

Is narrower beamwidth always better?

Narrow beams give gain and interference rejection but require accurate pointing.

References

Online sources accessed October 21, 2026; printed works cited by edition. See all sources.

  1. “IEEE Standard for Definitions of Terms for Antennas (IEEE Std 145-2013)”. IEEE Antennas and Propagation Society. 2014.
  2. “Antenna Theory and Design, 3rd ed.”. W. L. Stutzman and G. A. Thiele, Wiley. 2012.
  3. “Antenna Theory: Analysis and Design, 4th ed.”. C. A. Balanis, Wiley. 2016.
  4. “Antennas for All Applications, 3rd ed.”. J. D. Kraus and R. J. Marhefka, McGraw-Hill. 2002.
  5. “Phased Array Antenna Handbook, 3rd ed.”. R. J. Mailloux, Artech House. 2017.
Categories: Fundamentals