CMOS Rectifier Body Biasing for Low-Leakage RF 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 in both low and high input power scenarios.
Innovation Solution
A CMOS rectifier design incorporating a cross-coupled architecture with adaptive body biasing, which adjusts transistor threshold voltage based on operational states to minimize reverse leakage current and enhance power conversion efficiency, utilizing multiple stages connected to an energy harvesting antenna to generate and convert oscillating currents into DC voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If Schottky diodes are used in conventional rectifiers, then reverse leakage current is reduced, but fabrication cost increases due to extra masks and device complexity increases
Solution Approach 1:
The patent extracts the rectifying function from separate Schottky diode components and integrates it directly into the CMOS transistor structure. The source and drain regions of the CMOS transistors are configured to perform rectification, eliminating the need for external Schottky diodes and their associated fabrication masks, thereby reducing device complexity while maintaining low reverse leakage current performance
Solution Approach 2:
The patent merges the rectifier circuit and antenna into a single integrated structure where the CMOS transistors serve dual purposes: signal processing and rectification. This integration combines multiple functions into unified components, reducing overall device complexity and eliminating the need for separate Schottky diode fabrication steps
2Device complexity
If Dickson charge pump rectifier with diode-connected CMOS transistor is used, then device complexity is reduced, but reverse leakage current increases significantly
Solution Approach 1:
The patent applies local quality by creating asymmetric doping profiles in specific regions of the CMOS transistors. The source and drain regions have different doping concentrations optimized for their specific functions: one region is optimized for low reverse leakage while the other is optimized for high current drive, allowing the simple Dickson charge pump structure to achieve low leakage performance without increasing overall device complexity
3Ease of manufacture
If conventional CMOS rectifier design is used, then fabrication cost is reduced, but power conversion efficiency decreases at low and high input power levels
Solution Approach 1:
The patent implements dynamic operation by configuring the CMOS transistors to operate in different regions (linear and saturation) depending on the input power level. The rectifier stages are designed to adaptively switch between operating modes, maintaining high power conversion efficiency across both low and high input power conditions while using standard CMOS fabrication processes
Solution Approach 2:
The patent utilizes parameter changes in the CMOS transistor operating conditions to optimize performance. By adjusting the gate-source voltage and drain-source voltage parameters dynamically based on input power levels, the rectifier maintains high efficiency across a wide input power range while continuing to use cost-effective standard CMOS fabrication
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 100 kΩ load, effectively harvesting RF energy across a wide range of input power levels, outperforming conventional designs by maintaining high efficiency at both low and high input power levels.
Implementation Method 1
an energy harvesting antenna configured to receive an electromagnetic radiation and generate an oscillating current
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.