A 73.9%-Efficiency CMOS Rectifier Using a Lower DC Feeding (LDCF) Self-Body-Biasing Technique for Far-Field RF Energy-Harvesting Systems

A self-body-biasing technique is proposed for differential-drive cross-coupled (DDCC) rectifier, with its profound application in far-field RF energy-harvesting systems. The conventional source-to-body, and the proposed technique known as Lower DC Feeding (LDCF), were fabricated in the 130-nm CMOS and compared at the operation frequency of 500 MHz, 953 MHz and 2 GHz along with a corresponding load of 2 kQ, 10 kQ and 50 kQ. The technique allows the PMOS transistors to operate with a dynamic threshold voltage (V
_th
) which improves the power conversion efficiency (PCE) when the rectifier is operating at a smaller received power. A 9.5% of improvement is achieved at the peak PCE when the rectifier is operating at 953 MHz, and driving a 10 kQ load. A maximum PCE of 73.9% is measured at 2 GHz when driving a 2-kQ load. The LDCF technique also offers a self-limiting capability for its output voltage, by reducing the PCE at larger received power. A limit-voltage level of 3.5 V is measured irrespective to the operating frequency and load. This capability aids the protection of the subsequent circuits in a wireless sensor from being overpowered.