Development of RF to DC conversion circuit for energy harvesting

Abstract

The demand of wireless application devices shows significant growth in this era. This leads to the needs of a long life battery unit to supply power for wireless devices. Thus, the idea of fulfilling this demand is by harvesting the surrounding energy and channeling it as the source for the battery. Among all sources, radio frequency has a lot of benefits since it is available almost everywhere, cost-free, and it does not require high power consumption to convert the signal to a desired voltage. However, previous studies on this subject have highlighted difficulty in converting a low power RF signal, since the discrete components such as diode, transistor and MOSFET use a high voltage drop operation. Another common obstacle is the radio frequency signal that needs to be converted have to be within the specific range of frequency. Therefore, the objective of this thesis is to study, develop and propose the new RF to DC converter circuit that can overcome problems as to be implemented in the application. The proposed circuit consists of rectifier, ring oscillator, charge pump and regulator. The rectifier rectifies the RF input signal to a DC voltage. The combination of charge pump and the ring oscillator acts as a DC to DC converter to convert a low input voltage to a higher output voltage. Finally the DC output voltage will be regulated to a desired 1.2 V DC and ready to be stored in the battery. The proposed RF to DC conversion circuit uses a 0.13 μm CMOS technology which is suitable for low power application. The proposed circuit is simulated by using Composer Schematic Editor in Cadence software. The result shows that the RF to DC conversion circuit can convert a -16.48 dBm RF signal to regulated 1.2 V DC output voltage with the load of 50 kΩ. The simulation also proves that the proposed circuit can convert wide RF bands ranging from 900 MHz to 2400 MHz.