Open Vacancy at École Nationale d'Ingénieurs de Brest

The project will be carried out within the Lab-STICC laboratory (UMR CNRS 6285) bringing together researchers from ENIB, in the field of photonics, and UBO, in the field of microwaves. The project must meet several requirements: the main ones being, on the one hand, the remote generation of tunable delays in order to centralize their remote management of an antenna network and, on the other hand, the use of a carrier frequency, suited to the antenna array, adjustable over several decades, up to THz, without modifying the structure of the microwave filtering devices. We propose the architecture of an opto-microwave hybrid system to meet these constraints.

The tunable delay for an antenna of the antenna array is generated by a two-stage opto-hyper system: a phase-shift and pre-distortion RF stage operating in baseband or at intermediate frequency followed, after an electrical-optical conversion stage, an optical semiconductor amplifier (SOA) which role is twofold. The SOA must, on the one hand, add a phase shift to the one generated in the electrical layer, by the pre-distortion stage, so that a true time delay is applied to the RF signal intended for the antenna and, on the other hand, generate the frequency up-conversion of the electrical signal from baseband or intermediate frequency towards the sub-THz frequency range. The advantage of this structure is that it allows the pre-distortion RF stage to act independently of the target carrier frequency and to work in baseband or at intermediate frequency. It also exploits the SOA capacity to use the so-called “up-CPO” technique making it possible to transpose to very high frequencies the phase shift applied to a signal in baseband or at intermediate frequency. This signal, transposed into frequency and carried optically, can be distributed to the antenna potentially placed at a great distance. The pre-distortion stage has the advantage of taking into account and correcting the non-linearities generated by the SOA and thus widening the instantaneous bandwidth for the signal, beyond several GHz.

The different stages of the study will be based on simulation phases, in order to guide research towards the most promising techniques, and on measurement campaigns on optical-microwave bench to validate the concepts experimentally. The objective is to implement and test a complete path of the architecture to generate a true time delay. A co-simulation platform can be used, allowing both a fine simulation of optical components and microwave circuits and a more system-oriented simulation. This is possible by the joint use of electrical and optical simulators (ADS/Keysight and VPI TM/VPIPhotonics). The relevance of the use of a co-simulation platform has already been demonstrated by the LabSTICC / ENIB team and will make possible to assess, from end to end, the operation of the proposed architecture and identify specific issues to be solved to optimize overall performance.