thumb|Crossed field test antenna installed in Silsden, U.K.
A crossed field antenna (CFA) is a controversial type of radio antenna for long and mediumwave broadcasting, patented by F. M. Kabbary and M. C. Hately in 1986, which was claimed to have the same efficiency as a conventional antenna but only one-tenth the overall height. The invention was received with incredulity from experts in electromagnetics and antenna technology owing to the deficient theoretical justifications offered and the lack of viable experimental verification. Although the antenna was installed in a few broadcasting stations in the 1990s, performance has not borne out the claims of the inventors.
Description
As with other low frequency antennas, the crossed field antenna is installed above a ground plane which may be the Earth. It consists of three electrically active parts:
- A horizontal metal disc (or "D-plate") raised above and insulated from the ground plane;
- A vertical hollow metal cylinder (or "E-plate") of smaller diameter than the disc, which it is concentrically mounted above, and insulated from;
- A metal lattice funnel (or "extended conical section") radiating above and outward from and connected to the top of the cylinder.
The theory of the antenna's operation is described in its inventor's literature.
Performance
In general, peer-reviewed journals have not accepted papers on CFAs, casting doubt on their claims. published by the Institute of Electrical and Electronics Engineers (IEEE) suggested that the Crossed Field Antenna was no more efficient than a conventional antenna design of the same height. The data presented in figure 31 of the Trainotti and Dorado report shows measured field values up to 15 dB lower than (3% of) a theoretical 100% efficient monopole antenna.
The last commercial CFA was installed in 2003. At the General Assembly of the DRM Consortium, in Hangzhou China in April 2004, a Chinese manufacturer Zhongli made a demonstration with assistance from Thales SA and fed their new Crossed Field Antenna with 6 kW of DRM power. Results of the test are not available.