• Folded Dipole• Discone

Folded Dipole AntennaA folded dipole is a dipole antenna with the ends folded and connected to each other, forming a loop.

The width d of the folded dipole antenna is much smaller than the length L.

Main features

• It provides good impedance matching characteristics to practical coaxial lines of characteristic impedances 50-70 ohms.

• Wider bandwidth than dipole antennas.• Low noise pickup.• High impedance.

Applications

• Widely used as feed element of TV antennas.• Antennas for FM band

Discone Antenna

• A discone antenna is a version of a biconical antenna in which one of the cones is replaced by a disc. It is usually mounted vertically, with the disc at the top and the cone beneath.

• The disk is attached to the center conductor of coaxial feed line and is perpendicular to its axis. The cone is centered at its apex to the outer shield of the coaxial line.

Discone contd.. A discone antenna typically has at least three major components: the

disc, the cone, and the insulator.

• The disc The antenna's feed point is at the center of the disc.

• The cone The length of the cone should be a quarter wavelength of the antenna's

minimum operating frequency.

• The insulator The disc and cone must be separated by an insulator, the dimensions of

which determine some of the antenna's properties.

Main features

• Omnidirectional antenna• Vertically Polarized• Unity gain• Wideband : Wide range of frequency spectrum

Disadvantage• Due to wideband characterstics, it is highly affected

by noise.

Applications

• Due to wideband characterstics, wide applications comercially: UHF discone, etc

• Military applications : scanner radios, etc