What is the primary shape of a common reflector antenna?

What is the primary shape of a common reflector antenna?

• A. Circular
• B. Linear
• C. Parabolic
• D. Elliptical

Answer: (C)

The key idea is that reflector antennas achieve a tight, directional beam by using a surface that focuses waves. A parabolic surface has the special property that waves arriving parallel to its axis are reflected to a single point called the focus. When the feed is placed at that focus, the waves it emits are reflected out into space as a narrow, coherent beam, giving high gain and directionality. This is exactly how common dishes like satellite dishes operate. Other shapes don’t provide the same single-point focus for on-axis parallel waves: a circular form isn’t guaranteed to focus to one point, a linear shape isn’t a useful reflecting surface, and an elliptical reflector, while able to map waves between two foci, isn’t used for the straightforward on-axis focusing needed in typical dish antennas.

The key idea is that reflector antennas achieve a tight, directional beam by using a surface that focuses waves. A parabolic surface has the special property that waves arriving parallel to its axis are reflected to a single point called the focus. When the feed is placed at that focus, the waves it emits are reflected out into space as a narrow, coherent beam, giving high gain and directionality. This is exactly how common dishes like satellite dishes operate. Other shapes don’t provide the same single-point focus for on-axis parallel waves: a circular form isn’t guaranteed to focus to one point, a linear shape isn’t a useful reflecting surface, and an elliptical reflector, while able to map waves between two foci, isn’t used for the straightforward on-axis focusing needed in typical dish antennas.