Beamwidth
Understanding Antenna Beamwidth
Beamwidth is the primary parameter describing how focused an antenna's radiation is. It directly relates to gain: narrower beamwidth means higher gain, because the same total power is concentrated into a smaller solid angle. Beamwidth also determines angular resolution in radar and the pointing accuracy required for communication links.
Beamwidth and Gain Relationship
For antennas with a single main beam, gain can be estimated from the beamwidths in the two principal planes: G = 41,253 / (theta_E x theta_H), where the beamwidths are in degrees. This approximation assumes sidelobes and losses are small.
Beamwidth by Antenna Type
| Antenna | Typical HPBW | Typical Gain |
|---|---|---|
| Dipole | 78 deg (H-plane) | 2.15 dBi |
| Patch (single) | 60-90 deg | 5-9 dBi |
| Standard gain horn | 10-50 deg | 10-25 dBi |
| 1m dish at 10 GHz | 1.8 deg | 39 dBi |
| 3m dish at 12 GHz | 0.5 deg | 49 dBi |
theta_3dB = 70 x lambda / D (degrees, uniform)
Rectangular aperture:
theta_3dB = 51 x lambda / L (degrees, uniform)
Gain from beamwidth:
G = 41,253 / (theta_E x theta_H)
Frequently Asked Questions
What is antenna beamwidth?
Beamwidth is the angular width of the main lobe measured at the half-power (-3 dB) points. It describes how focused the antenna beam is. Narrower beamwidth = higher gain = more precise pointing required.
How does beamwidth relate to gain?
Gain and beamwidth are inversely related: narrower beamwidth means higher gain. The same total radiated power is concentrated into a smaller solid angle. Doubling the aperture diameter halves the beamwidth and quadruples the gain (+6 dB).
What determines beamwidth?
Beamwidth is determined by the antenna aperture size relative to wavelength. HPBW = approximately 70 x lambda/D for a circular aperture. Larger antenna or higher frequency (shorter wavelength) produces a narrower beam.