Broadband antenna
Broadband antennas are antennas in which the electrical properties (for example the radiation characteristics and the base point resistance ) change little over a wide frequency range due to special design measures .
If the dimensions of an antenna, normalized to the wavelength, remain the same, their electrical properties also remain constant. An antenna whose shape remains unchanged when the scale changes, is therefore independent of frequency. This requirement is met if the antenna structure can only be defined by specifying angles (angle principle). However, this means that the structure must be infinitely extended and the feeding points must also be infinitely close to one another. In practice, the respective minimum and maximum dimensions limit the usable frequency range of the antenna.
Practical designs
The discone antenna is an example that makes it possible to use a wide frequency range.
In the case of a dipole , broadband can be achieved by thickening the radiator or widening it to two triangular areas. These broadband dipoles are often also called biconical antennas and are very widespread in the field of EMC measurement technology.
A logarithmic periodic antenna consists of a number of dipoles whose length and distance decrease towards the direction of radiation.
The logarithmic spiral antenna uses a similar principle based on the angle principle .
Combinations of broadband dipoles and logarithmic-periodic antennas are called hybrid antennas .
literature
- Gerd Klawitter: Antenna advisor receiving antennas for all wave ranges. 6th edition, Verlag für Technik und Handwerk, Baden-Baden 2005, ISBN 3-88180-613-X