This paper presents the implementation of a high-efficiency radiofrequency (RF) harvester, which consists of a rectenna and a maximum power point tracker (MPPT). The rectenna was characterized from −30 dBm to −10 dBm at 808 MHz, achieving an efficiency higher than 60% at −10 dBm. Experimental results also show that the rectenna can be well modelled as a Thévenin equivalent circuit, which allows the use of a simple ensuing MPPT. The complete RF harvester was tested, achieving an overall efficiency near 50% at −10 dBm. Further tests were performed powering a sensor node from a nearby antenna.
Smart utilities enable more efficient energy consumption and distribution and are the key for smart homes development. We propose an electronic device that will be integrated as an add-on to already installed conventional gas meters as a first stage of smart metering rollout. The electronic device will measure the gas consumption and it will be managed by the user’s or operator’s smartphone via NFC. For the gas flow measurement, the electronic device takes advantage of the rotation of a permanent magnet fixed in an index drum.
This paper proposes a compact Thévenin model for a rectenna. This model is then applied to design a high-efficiency radio frequency harvester with a maximum power point tracker (MPPT). The rectenna under study consists of an L-matching network and a half-wave rectifier. The derived model is simpler and more compact than those suggested so far in the literature and includes explicit expressions of the Thévenin voltage (Voc) and resistance and of the power efficiency related with the parameters of the rectenna. The rectenna was implemented and characterized from −30 to −10 dBm at 808 MHz. Experimental results agree with the proposed model, showing a linear current–voltage relationship as well as a maximum efficiency at Voc/2, in particular 60% at −10 dBm, which is a remarkable value. An MPPT was also used at the rectenna output in order to automatically work at the maximum efficiency point, with an overall efficiency near 50% at −10 dBm. Further tests were performed using a nearby transmitting antenna for powering a sensor node with a power consumption of 4.2 µW.
This paper proposes, analyzes, and tests a wake-up circuit for a microcontroller (MCU) that uses a LED, operating as a photodetector, illuminated by a smartphone flashlight. The wake-up circuit consists of a high-pass filter and a voltage level translator that interfaces the LED, with a suitable resistor in parallel, to the MCU. When illuminated by a switching flashlight, the LED generates a square voltage that is conveniently converted in logic levels at the output of the wake-up circuit. A firmware embedded into the MCU additionally checks that a predetermined sequence of logic pulses at a given rate is accomplished to activate the MCU. The paper includes a theoretical analysis and experimental results that validate the proposed circuit.
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