Body-Biased CMOS Rectifier for Low-Leakage RF Energy Harvesting
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Solution Overview
Problem
Conventional CMOS rectifiers for RF energy harvesting face challenges such as high reverse leakage current, complex circuitry, and limited power conversion efficiency across a wide range of input power levels, making them unsuitable for efficient energy harvesting at both low and high input power levels.
Innovation Solution
A CMOS rectifier design employing an adaptive body biasing scheme with a cross-coupled architecture, where body biasing capacitors are used to dynamically adjust the threshold voltage of transistors, reducing reverse leakage current and enhancing power conversion efficiency by optimizing transistor operation during both half cycles of the oscillating current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If Schottky diodes are used in rectifier circuits, then reverse leakage current is reduced, but fabrication cost increases due to extra masks and integration complexity
Solution Approach 1:
The patent combines the rectifier and voltage multiplier functions into a single integrated CMOS circuit block, eliminating the need for separate Schottky diodes and their associated fabrication masks. The CMOS transistors perform both rectification and voltage multiplication, reducing manufacturing complexity and cost while maintaining low reverse leakage current through proper transistor configuration and body biasing techniques.
Solution Approach 2:
The patent utilizes body biasing to dynamically adjust the threshold voltage of CMOS transistors, optimizing their performance to match that of Schottky diodes. By changing the body voltage parameter, the transistors can operate with reduced reverse leakage current while remaining fully integrated in standard CMOS technology, avoiding the need for expensive Schottky diode integration.
2Object-generated harmful factors
If conventional CMOS transistors with low threshold voltage are used, then reverse leakage current increases, but power conversion efficiency decreases
Solution Approach 1:
The patent implements dynamic body biasing that adjusts the threshold voltage of CMOS transistors based on the operating conditions. During different phases of the RF cycle, the body voltage is modulated to optimize transistor performance - reducing reverse leakage when transistors are off while maintaining low on-resistance when on, thereby achieving high power conversion efficiency without suffering from high reverse leakage current.
Solution Approach 2:
The patent changes the body voltage parameter of CMOS transistors dynamically during operation. By applying appropriate body bias voltages, the threshold voltage is adjusted to minimize reverse leakage current while maintaining efficient conduction during the active phases, thus resolving the contradiction between low reverse leakage and high power conversion efficiency.
3Device complexity
If a single-stage rectifier is used, then circuit complexity is reduced, but power conversion efficiency across wide input power range is limited
Solution Approach 1:
The patent designs a multi-stage circuit where each stage serves multiple functions: rectification, voltage multiplication, and impedance transformation. The cross-coupled configuration allows the same circuit topology to efficiently operate across a wide input power range by leveraging the nonlinear characteristics of CMOS transistors and the synergistic interaction between stages, achieving high efficiency without requiring complex switching mechanisms.
Solution Approach 2:
The patent employs a nested architecture where voltage multiplier stages are integrated within the rectifier structure. Each subsequent stage is coupled to the previous one, with capacitors and transistors nested in a cross-coupled configuration. This nested design allows the circuit to maintain low complexity while achieving high power conversion efficiency across wide input power ranges through the cumulative effect of multiple stages working together.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The CMOS rectifier achieves a peak power conversion efficiency of 78.2% at an input power of −27.5 dBm and a 100 kΩ load, outperforming conventional designs by maintaining high efficiency across varying input power levels and load conditions.
Implementation Method 1
an energy harvesting antenna configured to receive an electromagnetic radiation and generate an oscillating current
Implementation Method 2
body biasing capacitors are used to dynamically adjust the threshold voltage of transistors
Data Source
AI summary
A circuit and methods describing a complementary metal-oxide semiconductor (CMOS) rectifier for use in radio frequency (RF) energy harvesting with body biasing by the RF input to control the threshold voltage of each transistor. The CMOS rectifier includes an energy harvesting antenna, and multiple rectifier stages. The antenna receives electromagnetic radiation from the environment and generates a DC current. The oscillating input current is an RF+ positive current during a first half cycle and is an RF− negative current during a second half cycle. A first rectifier stage includes a first capacitor connected to the RF+ positive current, a second capacitor connected to the RF− negative current and a cross coupled CMOS circuit connected to the antenna.