The design and implementation of DTMOS biased all PMOS rectifier for RF energy harvesting

The demand for battery free systems in remote applications raises interest in RF energy harvesting. The front-end for RF energy harvesting is the rectifier circuit that should be capable of operating efficiently at very low RF voltages. The rectifier is a circuit which converts the received RF signal voltage into an output DC voltage. The diode-connected transistor is most commonly employed in realizing the ON-chip rectifier circuit. Usually, the body terminal is connected to the source terminal (BTMOS) in the diode-connected transistor to minimize threshold voltage variation. In this work, we propose the implementation of principle of DTMOS concept where the body terminal is connected to the gate terminal in diode-connected transistor. This implementation facilitates the rectifier with dynamic control over threshold voltage. During forward conduction, the threshold voltage will lower which enables the rectifier to operate at low RF voltage amplitude. Similarly, rise in the threshold voltage during reverse conduction, reduces the reverse conduction loss in the rectifier. The single stage Dickson charge pump based rectifier is designed using BTMOS biasing and DTMOS biasing scheme and have been fabricated with a 0.18 μm standard CMOS process. The performance is expressed in terms of power conversion efficiency(PCE). The measurement results are presented for the targeted resistive load of 1 KΩ and 10 KΩ and RF input power varies from 24dBm to +10dBm at the signal frequency of 433MHz. The measured peak PCE for BTMOS biasing is ≈16% at the input RF power of ≈-8dBm while for DTMOS biasing the peak PCE is ≈23% at the input RF power of ≈-10dBm for the resistive load of 10 kΩ. Thus DTMOS biasing provides ≈7% improvement in PCE with 25% less input RF power.

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