A tour of the radiating structures that show up on spacecraft and ground stations. How to choose among them: antenna selection choices.
Wire Antennas
- Monopole: uses a ground plane
- Dipole: two conducting arms (omnidirectional in its azimuth plane, nulls along its axis — see isotropic vs. omnidirectional)
- Helical: in axial mode can give a directional, circularly polarized beam (see polarization)
Log-Periodic and Yagi Antennas
- Log-periodic: broad frequency coverage
- Yagi: a driven element with parasitic elements
Patch Antennas
- A radiating patch above a ground plane
- Low profile and easy to mount
- Can serve as an array element (see phased arrays)
Horn Antennas
- Pyramidal horns
- Conical horns
Reflector Antennas
- Configurations:
- Prime focus (): feed at the main reflector’s focus
- Cassegrain focus (): a subreflector redirects the path to a feed near the main reflector
- Ground antenna hardware: ground-station reflectors, up to the DSN 70 m reflector
- Gain scales with diameter and frequency: reflector gain
Broad-Coverage Antennas
- Hemispherical coverage: crossed dipoles, quadrifilar helix
- Covered with the coverage trades in Antenna Coverage