Renesas Electronics Corp developed a near-field wireless communication technology to transmit data to Bluetooth- and wireless LAN (WiFi)-compatible devices without using a battery.
It transmits data by using electricity harvested from environmental radio waves. The company will announce the details of the technology at 2011 Symposium on VLSI Circuits, which takes place from June 15, 2011 (thesis number: 16-1).
Because the new technology does not require a battery, it might realize an ultra-small sensor node. For example, if an adhesive plaster made by using the technology and a small body temperature sensor is attached to a baby, it is possible to constantly monitor the body temperature of the baby with a WiFi-compatible smartphone from a distance of less than 1m.
Also, a poster made by using the technology and a small sensor can transmit information to the Bluetooth- compatible device of a person passing by the poster.
Normally, to use Bluetooth or wireless LAN with a sensor node, the power consumption of its wireless transmission circuit becomes several tens of milliwatts, making it necessary to use a battery. With the new technology, however, the power consumption of the wireless transmission circuit was reduced to several microwatts.
On top of that, by using a technology to harvest electricity of about 10μW from environmental radio waves and driving the transmission circuit with this electricity, Renesas eliminated the need for a battery.
To transmit data by using several microwatts of electricity, the company employed the following method. First, radio waves have to be transmitted from an access point to mobile devices. And the newly-developed circuit (sensor node) equipped with an LC resonant circuit is installed here to absorb radio waves through LC resonance.
Then, radio waves can be directly transmitted from the access point to the mobile devices, improving the communication situation. The mobile devices interpret this as the sensor node sending "0" signals.
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