# Half Power Beamwidth (HPBW)

A half power beamwidth is the angular separation between the half-power (-3dB) points on the opposite side of the pattern maximum (major lobe).

The side lobe attenuation, back lobe attenuation, 3dB angle of the major lobe and 3dB angle of side lobe are applied to the vertical and the horizontal pattern. In the case of a vertical pattern, the variable $\vartheta$ is used to describe the angles. For the horizontal pattern, the variable $\phi$ is used to describe the angles. The 3dB angles are also called half-widths.

Directivity is indicated in dB, and the lobe width 3dB values are more easily legible in degrees in a directivity pattern. It results in the following, adapted dimensional equation (angles values are in degree):

(1) ${D}^{\prime }\approx \frac{41253}{{\phi }_{M}|°\cdot {\vartheta }_{M}|°}$