The Joint Laboratory project presented in this document associates the UMR CNRS / University of Limoges Xlim with the company INOVEOS. Its’ goal is to develop a conception methodology, to make and measure new non-reciprocal components (circulators, isolators, phase shifters...) using ferrite materials. These components, widely used within the microwave field, are very tricky to develop (especially the circulators). There are no reliable methods to do this. Manufacturers, in order to answer to technical specifications, are still obliged to work from existing designs which they modify step by step in function of the requests thanks to the know-how of some specialists. These adjustments are lengthy, tedious, expensive and don’t guarantee an optimal solution. Furthermore, it is almost impossible to imagine new designs. The company who would have a method and a conception tool would have a big advantage over its competitors. This is why, the company INOVEOS who designs and markets this type of components, and the laboratory Xlim who has been working for several years on the modelization of ferrite based devices (antennas, circulators…) have decided to associate themselves to meet this challenge. The scientific program will be divided into several phases and will be primarily focused on the designing of the circulators. 1. The first phases’ goal will be to develop a reliable methodology for the design of massive circulators (stripline type for example…). It will go via : • the mastering of the magnetostatics and a reliable modelization of the ferrite (appropriate tensor model, homogeneity of the field, …) • the mastering of the electromagnetic phenomena. For these two “steps” we will rely on the software of the CST suite. • Validation by comparison simulation / measurement on a known device. • The establishment of a methodology of conception (choice of the materials and magnets, topology, …) and the answer, thanks to this methodology, to a specification review provided by INOVEOS. • This new methodology will have to, amongst other things, enable to answer faster to specific needs not covered by the standard designs widely diffused worldwide and hence be performant for either wide band or narrow band needs but with higher performances. At completion of this first step, we will have to be able to reliably create innovative designs. It should take approximately 30 months. 2. The second phase will be aimed at initiating the work leading to the miniaturization of the non-reciprocal devices. This will require the utilization of ferrites in thin layers, self-magnetized if possible. To achieve this we will have to establish cooperation with laboratories specialized in magnetic materials (LabSticc, …). 3. A third phase will aim at approaching the modelization of power devices. Phases two and three will be launched during the last year of the Joint Laboratory (in parallel with phase 1). They will be intended to sustain the laboratory by giving it new perspectives. The Joint Laboratory needs to be an accelerator for the cooperation already underway regarding this subject between Xlim and INOVEOS (will be developed in the document). It will be a means to engage more human resources, software and materials to reach higher levels of Technology Readiness Level than with a simple thesis. The phases two and three will be a means of going quickly towards the miniaturization and the power handling, these aspects will not be addressed in a near future without this project.

Communication systems for civil and military applications have become increasingly complex. They tend to agglomerate multiple standards, which often contradicts the miniaturization requirements of terminals. Two essential elements of RF Front End are the antennas and the circulators placed ahead of them. They are usually designed separately and matched to a standard impedance, typically 50 Ohms. Increasing the compactness and the reducting the losses of these devices will be achieved by grouping these two elements together via a joint antenna/circulator design in order to avoid the interconnection stages. Furthermore, the grouping of communication standards on the same Front-End also seems relevant and requires the development of multi-band antennas as well as multi-band circulators. Finally, circular-polarized transmission and/or reception is/are increasingly required, especially for space applications. Biased ferrite materials are the main element in the design of passive circulators. In addition, they allow the natural generation of circularly polarized waves, which also makes them good candidates for circularly polarized antennas. The BISTRAU project presented in this document therefore aims to develop a new methodology for the joint design of a compact multi-band "circulantenna" (circulator-antenna association) radiating circular polarization thanks to the specific properties of ferrites. This co-integration will involve the use of a common ferrite substrate consisting of one or two layers (functions stacking). In this framework, a new topology of microstrip dual band circulator will be developed due to its smaller footprint. We will take advantage here of the biased ferrites properties that generate naturally circularly right and left polarized waves. An application in the SatCom band (20-30 GHz) will be targeted. Thus, to summarize, several challenges will be addressed in this project: • The development and validation, for the first time in the state-of-the-art, of a dual-band circulator in microstrip technology with a f2/f1 ratio of 1.5. • The design and validation of the first circularly polarized dual-band ferrite antenna with a ratio f2/f1 = 1.5. The control of the frequency ratio is a real challenge. • Development of a dual-band “circulantenna” co-design method without using 50 Ohms with again a frequency ratio of 1.5. Microstrip technology will be also chosen. An experimental phase will be carried out. In addition and to validate the methodology, a comparison of the performance between the joint design and a separate design will be carried out.

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.