Parabolic Reflector Antenna (2D Cross-Section)

Dish Geometry

Dish diameter 2.0 m

Focal length 0.6 m

Incoming Signal

Off-axis angle 0°

Rays converge tightly at the focal point.

Live Readout

Focal point (x, y)

0.00, 0.60 m

Spot spread

0.00 m

Convergence quality

100%

Relative gain

0.0 dB

How it works

A parabolic reflector's cross-section follows y = x²/(4f), where f is the focal length. This shape has one special property: every ray travelling parallel to the dish's axis reflects off the curve and passes through the same single point — the focus, at (0, f) — regardless of where on the dish it lands.

That is why satellite dishes work: a distant transmitter is effectively an infinite number of parallel rays, and the parabola collects all of them onto one small feed horn at the focus, concentrating a weak, spread-out signal into a strong one.

Tilt the incoming signal off-axis and the rays no longer share a common focus — they land in a smeared patch near it (coma aberration). The readout below tracks that spread directly: a bigger dish or a longer focal length narrows the beam but also narrows how far off-axis it can point before the spot smears and gain drops, which is exactly why a real dish must be aimed to within a fraction of a degree.