RF energy harvesting with W-CDMA

The low power RF devices such as RFID and Zigbee are important for ubiquitous sensing. However, these devices are powered by a portable energy source like battery. Thus the usage of a low power RF device has limited. To mitigate this problem, we have developed RF energy harvesting with W-CDMA for a low power RF device. Diodes is required with low turn on voltage, since the diode threshold is larger than the received peak voltage of the rectenna. Therefore, we used a Schottky diode HSMS-286. The prototype of RF energy harvesting device shows the maximum gain of 5.8dBi for W-CDMA signal. The 16 patch antennas are manufactured with 10 dielectric constant PTFT board. In low power RF devices, transmitter requires the step-up voltage 2.5~5V with up to 35 mA. To meet this requirement, we used the Texas Instruments TPS61220 as a low input voltage step-up converter. From evaluated result, the achievable incident power of rectenna as 926mV to operate Zigbee can obtain within the distance of 12m.