Beamwidth Calculator

The Beamwidth Calculator estimates the Half-Power Beamwidth (HPBW, 3 dB beamwidth) in degrees and radians for circular aperture antennas (such as parabolic dish reflectors). By providing operating frequency and physical reflector diameter ($D$), RF engineers can quickly assess directional radiation focus and spatial coverage angle.

Enter Frequency, Antenna Diameter exactly in the units shown by this beamwidth. Check the operating band, unit prefix, and decimal position before calculating; these are the inputs used by the formula.

• Frequency — use MHz.
• Antenna Diameter — use m.

The results describe the calculated beamwidth values for the inputs you entered. Check each value against the available space, selected components, feed system, and operating conditions before making a final design decision.

The Beamwidth uses HPBW ≈ 70 × λ / D. Supply Frequency (MHz), Antenna Diameter (m) in the displayed units, then use the calculated values as the first engineering target for this basic antenna parameters design or analysis.

Half-Power Beamwidth represents the angular width of the main radiation lobe between the points where radiated power drops to half (-3 dB) of its peak value. For circular apertures with typical edge illumination tapers (such as $-10\text{ dB}$ parabolic dish feeds), HPBW is approximated using $\theta_{3dB} \approx 70 \times (\lambda / D)$ degrees. Increasing dish diameter ($D$) relative to wavelength ($lambda$) produces a narrower, more highly directional main beam, which maximizes directive gain but requires tighter alignment tolerances.

Verify antenna beamwidth through 2D or 3D far-field radiation pattern cuts using an automated antenna turntable in an anechoic chamber. Note that non-uniform feed illumination, aperture blockage from feed support struts, and dish surface roughness widen the measured beamwidth and increase sidelobe levels relative to theoretical predictions.