Pattern types
| Pattern | Shape | Gain | Example |
|---|---|---|---|
| Isotropic | Perfect sphere | 0 dBi (reference) | Theoretical only |
| Omnidirectional | Donut around antenna axis | 2–6 dBi | Dipole, monopole |
| Directional (beam) | Single main lobe | 6–55 dBi | Yagi, patch, dish |
| Bidirectional | Two main lobes | ~2–5 dBi | Horizontal dipole (broadside) |
| Cardioid | Heart-shape (more front) | ~5 dBi | Patch + reflector |
| Pencil beam | Very narrow main lobe | 20+ dBi | Dish, phased array |
| Fan beam | Wide in azimuth, narrow in elev. | varies | Airport radar |
Key metrics
| Beamwidth | Angular width between −3 dB points of main lobe |
|---|---|
| First-null beamwidth | Between first nulls — about 2× HPBW |
| Sidelobe level | Peak sidelobe relative to main (dB) |
| Front-to-back | Main lobe / back lobe ratio |
| Aperture efficiency | G = 4π A_eff / λ² — dish efficiency (60–80%) |
Typical values
| Antenna | Beamwidth | Front/back |
|---|---|---|
| Half-wave dipole | 78° (E-plane) | ~0 (symmetric) |
| 3-element Yagi | ~65° | ~10 dB |
| 10-element Yagi | ~40° | ~20 dB |
| Patch | ~65° | ~20 dB |
| Corner reflector | ~60° | ~25 dB |
| Dish (1 m @ 10 GHz) | ~2° | > 30 dB |
| Helix (8 turns) | ~40° | ~15 dB |
Notes
- Polar plot: 0° = main direction; radial scale usually in dB relative to main lobe peak.
- Gain (dBi) is above isotropic; dBd is above dipole. dBi ≈ dBd + 2.15.
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