Calculate dish antenna beamwidth in degrees or gain in dBi from frequency, dish diameter, pattern factor, and aperture efficiency.

Estimate dish half-power (โˆ’3 dB) beamwidth. Uses K = 70 by default; actual illumination changes the pattern.

Pattern-factor assumption

Model choices retained from the original. Larger K means a wider beam; these values do not uniquely identify an antenna type.

Beamwidth Formula

BWdeg โ‰ˆ K ร— (WL) / (D)

Variables:

  • BW is the beamwidth (approximately the half-power beamwidth) in degrees (ยฐ)
  • 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 pattern factor using the degree convention (model choices 58โ€“75; default 70). It depends on illumination.

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, enter operating frequency; the calculator obtains wavelength from ฮป = 299,792,458 m/s divided by frequency in hertz.
  • Next, determine the diameter (use the same length unit as the wavelength).
  • Next, gather the formula from above = BW โ‰ˆ K*WL/D (result in degrees).
  • Select Half-power beamwidth, enter frequency and diameter, optionally set K, then select Calculate.
  • 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 โ‰ˆ 8.75ยฐ).

wavelength (m) = 0.125, corresponding to frequency 2.398339664 GHz

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 (โˆ’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. A wider directional beam covers a larger angular region; this dish model does not represent an omnidirectional antenna.

Can Beamwidth be adjusted after an antenna is constructed?

A dishโ€™s beamwidth changes with frequency and aperture illumination. Phased arrays can steer and shape beams through their element weights, but that behavior is outside this fixed circular-dish model.