Cross-field antenna
Cross-field antenna ( CFA for short ), also EH antenna , is the name of a type of antenna for long wave , medium wave and short wave in which the electrical (E) and magnetic (H) field components of the electromagnetic wave to be generated are each different Components of the antenna are generated.
In principle, the CFA is a form of the Tesla transformer . In both practical and mathematical terms, it can be demonstrated that low scattering losses occur between resonance structures constructed in this way, which makes it interesting for wireless energy transfer, for example to charge batteries in wireless devices without contact.
Optimal radiation is only achieved if the E-field and the H-field are phase-shifted by 90 ° and are generated perpendicular to each other and perpendicular to the direction of radiation (in other words: effective only in the immediate near field).
The design goal of this antenna was clearly missed. This consisted of achieving the same efficiency as a conventional transmitting antenna (for example self-radiating transmission mast or conventional dipole ) with a significantly lower overall height . Compared to antennas with matched lengths, the CFA has a potentially higher bandwidth; however, this is associated with excessive antenna losses.
Practical experiments confirm that the cross-field antenna must be carefully balanced and that its efficiency is significantly lower than that of the conventional dipole or loop antenna .
Other investigations allegedly show better horizontal bundling or less radiation downwards and upwards and consequently a greater range for a CFA for 20 m wavelength compared to a standing quarter-wave dipole .
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
Web links / individual references
- ↑ Archive link ( Memento of the original dated August 4, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Comparison of CFA and loop antenna for a wavelength of 80 m
- ↑ CFA for 20 m. In fact, however, CFA antennas are avoided in radio practice, since they are consistently lagging behind by a factor of around 100 compared to conventional transmitting antennas.
