- The reducer can be a part of a bigger construction, and can contain large amount of metallic wires thus making it stronger than any ordinary material with wave propagation properties close to air.
- Radio antennas
- Reflector antennas
- Radio telescopes
- Radio masts
- Airport masts
Previously, invisibility devices have been invented for cloaking large objects at the radio frequency range. There the cloak is a spherical object made with special material. Inside the cloak, there is a hollow cavity where the object to be made invisible is placed. The drawback of these devices is their narrow bandwidth. Because of the narrow bandwidth they do not work for signals. Another common approach involves reduction of forward scattering from cylindrical objects using hard surfaces. There the wave is guided around the hidden object. The device is broadband, but works only for one angle of incidence. Therefore, the radiation source cannot be placed near the object which is made invisible.
Our invention deals with an invisible structure and how it can be applied. The structure is invisible at the frequency bandwidth, where it is designed to work. Then both the transmission line network and the matching layer are matched to work at this frequency band. Invisible structure can work for example as a supporting structure or as a mechanical shield, but still to be invisible for electromagnetic radiation. If an antenna is placed behind such an invisible structure, the radiation of the antenna may pass the structure freely. Similarly the material may be a supporting structure or it may give a mechanical cover for the antenna. The novel structure is also of broad bandwidth and it works for signals. Wires can be placed inside the structure while maintaining the invisibility. For example, the mechanical strength of the structure can be increased by adding metallic wires. Also electric wires can be placed inside the structure and still the material is invisible. The invisible structure passes the electromagnetic radiation through freely and it minimizes the back-scattering. This is because the invisible structure may be impedance matched with any surrounding material.
Method has been verified successfully in a laboratory scale.
Priority date: 04.06.2007
US 8164505B2 -24.04.2012
Main inventor: Dr. Pekka Alitalo
Department of Radio Science and Engineering
Head of Innovation Services
Phone: +358 40 186 3320