Enter any two of the wavelength, the antenna/aperture diameter, and the beamwidth (select units), then choose a pattern factor (K). The calculator will compute the missing value.
Beamwidth Formula
BW_{\mathrm{deg}} \approx K\cdot \frac{WL}{D}Variables:
- BW is the beamwidth (approximately the half-power beamwidth) in degrees (°)
- WL is the wavelength (any length unit, as long as it matches D; commonly meters)
- D is the antenna/aperture diameter (same length unit as WL; commonly meters)
- K is a dimensionless pattern factor (rule-of-thumb typically ~58–75; 70 is a common “typical” value)
To estimate beamwidth (in degrees), divide the wavelength by the diameter, then multiply by K (often ~70 for a typical parabolic dish illumination).
How to Calculate Beamwidth?
The following steps outline how to calculate the Beamwidth.
- First, determine the wavelength (use any length unit).
- Next, determine the diameter (use the same length unit as the wavelength).
- Next, gather the formula from above = BW ≈ K*WL/D (result in degrees).
- Finally, calculate the Beamwidth.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge (using K = 70 gives BW ≈ 8.75°).
wavelength (m) = 0.125
diameter (m) = 1
FAQ
What is Beamwidth in the context of antennas and optics?
Beamwidth is the angular spread of a beam of light, radio, or sound waves. In antennas and optics, it commonly refers to the angle between the two directions where the radiated (or received) power drops to half of its peak value (−3 dB), often called the Half-Power Beamwidth (HPBW).
How does the wavelength affect the Beamwidth?
For a fixed aperture/antenna diameter, beamwidth is approximately proportional to wavelength (and therefore inversely proportional to frequency). As the wavelength decreases (or frequency increases), the beamwidth becomes narrower for a given aperture size.
Why is Beamwidth important in antenna design?
Beamwidth is crucial in antenna design because it determines the antenna's coverage area and directivity. A narrower beamwidth focuses the signal more tightly towards a specific direction, which is beneficial for long-distance communication. Conversely, a wider beamwidth covers a larger area, useful for broadcasting and omnidirectional communication.
Can Beamwidth be adjusted after an antenna is constructed?
While the physical beamwidth determined by the antenna's structure cannot be easily changed after construction, electronic beam steering techniques can adjust the effective beamwidth and direction. This is achieved through phased array antennas, which manipulate the phase of the signal across multiple elements to steer the beam dynamically.
