New miniature antennas concepts based on innovative self-biased ferrites for multi-functions and circular polarization applications – CONTACT

The CONTACT project is part of the context of a very significant increase in the integration density of electronic systems for communications, localisation or surveillance equipment. This requires the design of antennas which must be both miniature and multifunctional since they have to be able to meet several communication standards. In addition, many spatial and military applications need for circular polarization, which is also an interesting solution for civil domains to overcome misalignments between transmitter and receiver and to mitigate inherent polarisation loss factors due to multipath problems. More specifically, the CONTACT project aims to demonstrate an antenna array that will be composed of 4 miniature, tri-band (GPS/Galileo) and circularly polarized radiating elements for satellite radionavigation systems.
The state-of-the-art shows that obtaining a circular polarization when the antenna needs to be miniature and work on different frequency bands is really challenging. Indeed, circular polarisation can be produced by integrating an electronic circuit to excite two orthogonal current modes with a phase difference of 90°. This kind of solution can be complex, is bulky, lossy and not working on different frequency bands simultaneously. The litterature exhibits that is difficult, if not impossible, to keep a good circular polarization on different working frequencies. In the CONTACT project, we propose to reach these three objectives (miniature, multi-band with circular polarization) by proposing innovative solutions based on ferrimagnetic materials. Indeed, this kind of materials has interesting properties since:
- Their non-diagonal anisotropy allows them to naturally generate circularly polarized waves
- In addition of a high dielectric permittivity (er=15 typically), their effective permeability can be higher than 1 on some well selected frequency bands. Therefore, it will be possible to reach high miniaturization degrees.
- Their permeability is dispersive, i.e. it varies with the frequency. The antenna could operate on its fundamental mode at two different frequencies. We could therefore develop a multi-band antenna with circular polarization (since the antenna will work on the same mode on two different frequency bands). Published studies on ferrites antennas, remain theoretical with an ideal magnetization of the material or carried out using permanent magnets, implying an increase of the global dimensions of the antenna. This problematic is avoided in the framework of the CONTACT project since we propose a solution based on self-polarized ferrites. The development and the realization of self-polarized ferrites used to propose miniature and multi-band antennas while having a circular polarization will allow us to avoid permanent magnets and therefore reduce the size of the global device, its complexity and improve its efficiency. The benefit compared to the state of the art offers a dual approach, the first one on the development of the antenna and the second one on the material. Indeed, by developing new concepts we will simultaneously obtain a miniature, multi-band and circularly polarized antenna with a single feed point. For the material part, improved processes will be developed to reach self-magnetized ferrites with features fitting with RF applications. The consortium complementary and the interdisciplinary approach within the CONTACT project is perfectly adapted to give solutions and implement this high-potential concept.