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Antenna radiation pattern and lobes

Short answer

Radiation pattern graphs far-field strength versus direction. Main lobe contains maximum radiation; minor lobes include side lobes adjacent and back lobe opposite. Nulls are zero-radiation directions. HPBW is angle between -3 dB points; FNBW between first nulls (≈2×HPBW). Side lobe level is side lobe peak relative to main lobe in dB.

Explain the radiation pattern (radiation pattern lobes) of an antenna.

A radiation pattern is a graph (2-D or 3-D) of the radiated field strength or power of an antenna versus direction (θ, φ) in the far field. It is usually normalized to the maximum and drawn in the E-plane and H-plane.

Radiation pattern lobes:

  • Main (major) lobe: lobe containing the direction of maximum radiation.
  • Minor lobes: all other lobes; side lobes are next to the main lobe and the back lobe is opposite it.
  • Nulls: directions of zero radiation between lobes.
  • HPBW: angle between −3 dB points of the main lobe; FNBW: angle between first nulls.
  • Side lobe level: side lobe peak relative to main lobe (dB).
          main lobe
           .---.
          /     \  HPBW
   side  |       |  side
   lobe .|       |. lobe
       (  \  o  /  )
        '  '-+-'  '
           back lobe

✓ Answer checked by Claude Opus 5.5 (high effort)

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