This paper presents the design of an ultra high-frequency (UHF) radio frequency identification (RFID) sensor tag integrated into a textile yarn and manufactured using the E-Thread^® technology. The temperature detection concept is based on the modification of the impedance matching between RFID tag’s antenna and the chip. This modification is created by the change in the resistance of a thermistor integrated within the tag system due to a temperature variation. Moreover, in order to obtain an environment independent detection, a differential approach is proposed that avoids the use of a pre-calibration phase by the use of a reference tag. Experimental characterization demonstrates the RFID sensor’s potential of detecting a temperature variation or a temperature threshold between $25$ and 70 °C through the variation of the transmitted differential activation power.

While many theoretical and simulation works have already highlighted the potential gain of cognitive radio, several technical issues still have to be evaluated and overcome from an experimental viewpoint. Our team is currently developing a new experimental facility remotely accessible and dedicated to this problem. CorteXlab is developed in the framework of a nationwide French program Future Internet of Things which proposes a federated and competitive infrastructure. The Cor-teXlab facility offers a 167m ² EM shielded room and integrates a set of 22 USRP from National Instrument, 16 picoSDR nodes from Nutaq and 42 IoT-Lab wireless sensor nodes from Hikob. CorteXlab is built on the network architecture developed for the SensLAB testbed and exploits the free and open-source toolkit GNU-radio. All nodes are remotely accessible through a software interface called Minus. The demo presented at Infocom describes the facility and shows the process a user should follow to deploy his own experiment. Two typical scenarios involving several nodes are built and deployed live. The first scenario is based on IEEE 802.15.4 communication between two picoSDR nodes. The second scenario is dealing with an avoiding-interference use case where the previous two picoSDRs are communicating while a cognitive MIMO-OFDM transceiver running on one picoSDR must avoid interference with them.

This study presents the analysis and the experimental results of a 2.4 GHz antenna array using vector modulators working as active phase shifters for beamforming. With the use of such an active phase shifter, a continuously controlled 360° phase shifting range can be achieved leading to an efficient beamforming architecture. To show the robustness of this system, a theoretical analysis is first performed in order to quantify the impact of vector modulators I/Q mismatch on the obtained gains and phase shifts. In the same way, the impact of the vector modulators noisy command voltages is also quantified by system simulations. The experimental results of the 2.4 GHz vector modulators show a maximum relative gain error close to 2.5% and an absolute phase error less than 3°. The measured 1 dB output compression point is −6 dBm. Measurements of the prototype including an array of four ‘patch’ antennas controlled by the vector modulators were also performed in an anechoic chamber. The results show good agreement between measured and theoretical radiation patterns.

Harvesting radio frequency (RF) energy is an attractive solution for powering ultralow-power (ULP) devices. However, harvesting efficiently from different RF power levels is still a challenge. This work presents a wide power range RF harvester composed of a rectifier circuit and a power management integrated circuit (PMIC). Such a wide range is achieved by associating two independent rectifiers in parallel, one specifically optimized for low RF powers. In the association, the inductive matching technique is employed in each rectifier. It consists of an inductive branch comprised of a lumped inductor and a short-circuited stub whose values are selected to minimize ohmic losses. The operation range is controlled via the inductive branch values and by following the optimal load of the rectifier circuit with the PMIC, based on the input power level. The harvester is designed at $889~\text{MHz}$ and manufactured by using off-the-shelf components. Measured efficiencies of $29\%$ and $63\%$ are obtained at $-20$ and $0~\text{dBm}$ , respectively, demonstrating the wide power range with high efficiency at low powers. At $-20~\text{dBm}$ , the rectifier association keeps the PMIC active and delivers hundreds of nW at a regulated voltage of $1.8~\text{V}$ , which is suitable for ULP devices.

The last decades have been really hungry in new ways to reduce energy consumption. That is especially true when talking about wireless sensor networks in general and home multimedia networks in particular, since electrical energy consumption is the bottleneck of the network. One of the most energy-consuming functional block of an equipment is the radio front end, and methods to switch it off during the time intervals where it is not active must be implemented. This paper proposes a wake-up radio circuit which is capable of both addressing and waking up not only a more efficient but also more energy-consuming radio front end. By using a frequency footprint to differentiate each sensor, awaking all the sensors except for the one of interest is avoided. The particularity of the proposed wake-up receiver is that the decision is taken in the radio-frequency part and no baseband treatment is needed.