Microwave Spintronics for Wireless Sensor Networks – SPINNET

CONTEXT
The objective of SpinNet is to bring low cost and low power solutions to key components used in wireless sensor networks (WSN) by exploiting recent results on spintronics microwave components. WSNs (as part of IoT) can nowadays be found everywhere, in vehicles, in habitat, in smart phones, in factories or in ground for environment monitoring (gaz, soil, traffic) to improve overall quality of life. In view of the increasing number of connected objects, a major concern is power consumption, compactness and cost, where the transmitter/receiver blocks are the most power consuming components in communicating sensor networks.

OBJECTIVE
Within this global context SpinNet proposes spintronics based solutions for three key components of WSN receiver Rx modules:
(i) Wake-up Radio (WuRx),
(ii) energy storage via Wireless Power Harvesting and Transfer (WPH/WPT) and
(iii) signal Demodulation (RxDEMOD).
For this SpinNet capitalizes on previous key achievements from the project partners by exploiting the best performances of one of the spintronic device classes, which are vortex magnetic tunnel junction (MTJ) devices (0.1-1GHz) and their RF-to-DC converter function (conversion of an RF input signal into a DC voltage signal). It is expected that optimized circuits can outperform existing components for the performance parameters of sensitivity to low input power, RF-DC conversion efficiency, power consumption and compactness.

WORKPLAN
The starting point are previous important results achieved by project partners on single non-optimized MTJ vortex devices for passive (IDC=0) and active (IDC non zero) detection functions.
Based on this three system level PCBs at TRL 3 will be developed. The overall methodology to improve system level performances includes three main steps:
(i) optimization of single devices to increase sensitivity + output signal level, reduce noise and optimize the signal shape (WP2)
(ii) definition of a network of serial and parallel devices to further increase sensitivity + output signal level, taking rf circuit design and impedance matching into account (WP3),
(iii) optimization of an antenna design, matched to the device network and realization of rf circuits on PCBs for functionalization of the spintronic device (WP4).
The output will be three PCBs (WuRx, WPH/WPT and RxDEMOD) that will be assessed and discussed for further exploitation.

OUTCOME/IMPACT
A major challenge for increasing the sensitivity to low input power is the definition of a network of devices connected in parallel and/or series. This is the first time that large arrays are addressed for the detection function with the aim to optimize single device and network performances to achieve target specifications for the different Rx functions. The achievements will also be beneficial for signal generation (not considered in this project but this is a very active research field of vortex spin torque oscillators, in particularly for neuro inspired spintronic devices). The functionalization of these networks for WuRx, WPH/WPT, RxDemod addresses questions on novel antenna designs for efficient energy distribution to the network, establishing an equivalent circuit for the detection function as well as novel multifrequency protocols for WuRx. It is expected that important new fundamental knowledge and new IP on system design will be developed that can be exploited also for other wireless communication applications.

CONSORTIUM
The project partners CEA-SPINTEC, UMPhy CNRS, THALES and CEA-LETI come from cross disciplinary communities (wireless communication and spintronics), are leading experts in their research field and have been collaborating before.