Radartutorial .eu
Angle of the Irradiation
Figure 1: headlight model of a phased-array antenna
Imagine an hemisphere as an idea model. A headlight is in the center and illuminates the
(inner) surface of the hemisphere so that an observer always sees the equal
spot size (as a projection) in central line of sight.
Since the observer looks at the margin sloping on the illuminated area of the hemisphere,
a larger area must be lit on the margin.
Well, the headlight can be focussed in central ray direction better.
Its „beam width Θ” is lower and
its „antenna gain” is better than at a large angle of the irradiation.
The Phased Array antenna behaves like the headlight model just described. But it isn't necessary that one knows this as a radar mechanic so exactly or that one even can derive this. It suffices to know:
The gain of a phased-array antenna deteriorates into dependence of the angle of the irradiation (Θs).
