radio astronomy concepts

HPBW&BWFN

Uniform linear feed the first null:
$$\theta=\lambda/D$$

Circular aperture the first null:
$$\theta=1.22\lambda/D$$

HPBW
半功率波束宽度: $\theta=1.02\lambda/D$
BWFN
主瓣束宽: $\theta=1.22\lambda/D$