Compact circulator operating in Ku band – CirCKu

This 30 months duration project concerns the development of compact circulators for applications in the Ku band, a frequency band in which new systems for defense and space telecommunications are developed. These components, essential in transmitter/receiver (T/R) modules, are today the main shortcoming concerning the required size reduction and ease of integration. The future RADAR detection and telecommunications systems must respect strong constraints of integration and performances. While some important progress already has been obtained regarding the active components, circulators / isolators are the weak link today because they are still cumbersome and expensive.

The main objective of this project is to implement a breakthrough manufacturing technology based on a collective and additive manufacturing of complex multilayer ceramic components. This technology consists in laminating various green materials, ceramics and metals, layer by layer and then to densify the assembly by sintering at low temperature.
Another objective consists in using new ferrite garnets having a high permittivity which immediately leads to a reduced component size.

The conventional manufacturing process of this type of components consists in assembling different nature materials by using long and expensive processes. These difficulties motivate the users to delete them or to replace them, but no satisfying solution has yet been found. The CirCKu project aspires at a process of collective manufacturing based on the LTCC technology (Low Temperature Cofired Ceramics). This process will allow to decrease the size and the cost but also to improve the performances of circulators because it is the only process that allows realizing ferrite-dielectric co-sintered structures without degrading the properties of the materials.

This project gathers a defence contractor (THALES) and two complementary teams of an academic laboratory, the Lab-STICC which is common to the University of Brest (UBO) and the school of engineers IMT Atlantique. It revolves around four main technical sub-projects, which concern:
- The synthesis of ferrite and dielectric materials
- The technology of shaping and co-sintering
- The optimization of the design and the simulation
- The microwave measurements (materials and devices).

The low sintering temperature ferrites (T < 900°C) offer new perspectives in terms of design and packaging. This new opportunity is mainly based on the recent discovery of new ferrites of garnet and spinel type for microwave applications. These ferrites, associated with low sintering temperature dielectric oxides, can be co-sintered with gold or silver metallic paths which enable the collective manufacturing of microwave circulators / isolators. This project will demonstrate the potential of a new manufacturing technology of microwave circulators for Ku band applications.
It will contribute also to the strengthening of the French and European supply chain in a field where the American end Asian domination represent a threat to a large part of our economy.