Classifying antenna types

Antennas can be sorted into a few broad structural families, which helps in understanding why each is suited to particular tasks. Wire antennas are built from thin conductors and include the dipole, the monopole working against a ground plane, and the loop. They are simple, inexpensive and effective from low frequencies up through the VHF range, where their resonant lengths remain physically reasonable.

Array antennas combine several radiating elements so their individual fields add in some directions and cancel in others, producing higher gain and a controlled beam. The Yagi-Uda array, with its driven element, reflector and directors, is the best-known example; log-periodic arrays extend useful operation over a wide band, and phased arrays steer the beam electronically by varying the phase fed to each element. Aperture antennas radiate through an opening rather than from a bare conductor: the horn is a flared waveguide, and reflector antennas such as the parabolic dish use a shaped surface to focus energy from a small feed into a narrow beam.

Within these families specialised forms address particular needs. Helical antennas provide circular polarization for satellite work; biquad and patch antennas are compact planar designs popular at microwave frequencies and in wireless networking; and groundplane verticals give omnidirectional coverage. The right choice depends on the operating frequency, the gain and beamwidth wanted, the polarization required, and the space and budget available.

Frequently asked questions

How are antennas grouped into families?

Common groupings are wire antennas, array antennas, and aperture or reflector antennas, based on how each structure produces and shapes its radiation.

What does an array antenna achieve?

By combining several elements with controlled spacing and phasing, an array reinforces radiation in wanted directions and suppresses it elsewhere, giving higher gain and a defined beam.

What is an aperture antenna?

An aperture antenna radiates through an opening, such as the mouth of a horn or the surface of a parabolic reflector, rather than directly from a thin conductor.