Open sleeve dipole

Image of the Open sleeve dipole.

The half-wave dipole antenna forms the basis for a number of other antennas such as the linear- and planar dipole arrays as well as Yagi-Uda and LPDA arrays. In its simplest form, it consists of two co-linear quarter-wavelength wire sections driven in anti-phase with respect to one another.

One popular way of increasing the operating bandwidth of a dipole structure is by using a sleeve. There are various ways in which a sleeve can be added to a dipole structure. The Open sleeve dipole is one very practical way to do this.

The Open sleeve dipole mentioned here includes a reflector and a quarter-wave balun, to enable feeding of the structure using an unbalanced coaxial line. Furthermore, two parasitic elements (sleeves) are added which enables a much wider bandwidth of typically 70% compared with 30% for a Cylindrical dipole with a quarter-wave balun in front of a reflector.

The image below shows a comparison between the S11 of the Open sleeve and the Standard quarter wave dipole with quarter-wave balun designed and simulated in Antenna Magus.

S11 comparison between the Dipole with quarter-wave balun and reflector antenna vs the Open sleeve dipole antenna.