A
parabolic antenna is an
antenna that uses a
parabolic reflector, a curved surface with the cross-sectional shape of a
parabola, to direct the radio waves. The most common form is shaped like a
dish and is popularly called a
dish antenna or
parabolic dish. The main advantage of a parabolic antenna is that it has high
directivity. It functions similarly to a searchlight or
flashlight reflector to direct the radio waves in a narrow beam, or receive radio waves from one particular direction only. Parabolic antennas have some of the highest
gains, that is, they can produce the narrowest
beamwidths, of any antenna type. In order to achieve narrow beamwidths, the parabolic reflector must be much larger than the
wavelength of the radio waves used, so parabolic antennas are used in the high frequency part of the
radio spectrum, at
UHF and
microwave (
SHF) frequencies, at which the wavelengths are small enough that conveniently-sized reflectors can be used.