Which of the following is not listed as a type of antenna in the material?

• A. Yagi
• B. Horn
• C. Waveguide
• D. Parabolic

Answer: (C)

The key idea is that some terms describe how energy is radiated, while others describe how energy is carried to the radiator. Yagi, horn, and parabolic reflector are all radiating structures designed to produce and shape a beam: a Yagi uses multiple elements to create a directional pattern, a horn provides a shaped aperture that radiates efficiently at microwave frequencies, and a parabolic reflector focuses energy from a feed at its focal point into a narrow, high-gain beam. Waveguide, by contrast, is a hollow metallic conduit used to guide microwave energy from the transmitter to the antenna or feed. It isn’t a radiator itself, so it isn’t listed as a type of antenna in typical material. It can feed or be part of a system that includes an antenna, but on its own it’s a transmission line rather than an antenna.