CMOS RF Energy Harvester Rectifier With Adaptive Body Biasing
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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 incorporating an adaptive body biasing technique and a cross-coupled architecture, 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 rectifier circuits, then reverse leakage current is reduced, but fabrication cost increases due to extra masks and device area increases
Solution Approach 1:
The patent extracts the harmful reverse leakage current characteristic from Schottky diodes by replacing them entirely with CMOS transistor-based rectifier circuits. The CMOS transistors are configured to operate in specific modes that inherently minimize reverse leakage without requiring Schottky diode structures, thus eliminating the need for extra masks and complex fabrication processes while achieving comparable or superior leakage performance.
Solution Approach 2:
The patent substitutes the physical Schottky diode component with an equivalent CMOS transistor circuit implementation. Instead of using a separate Schottky diode device with its specific physical structure and fabrication requirements, the rectification function is achieved through carefully designed CMOS transistor switching operations, replacing a specialized component with a standard semiconductor device configuration.
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 employs dynamic threshold voltage control through body biasing techniques. The threshold voltage of CMOS transistors is dynamically adjusted during operation to optimize performance: during rectification phases, the threshold is controlled to minimize reverse leakage current, while during energy transfer phases, it is optimized for maximum power conversion efficiency. This dynamic adaptation allows the system to achieve both low leakage and high efficiency that static threshold voltage designs cannot accomplish.
Solution Approach 2:
The patent changes the operational parameters of CMOS transistors by implementing adaptive threshold voltage control mechanisms. Through body biasing circuits and controlled gate voltages, the transistor threshold voltage parameter is modulated to match different operational requirements, enabling the system to achieve optimal reverse leakage performance and power conversion efficiency across varying input power levels and operating conditions.
3Loss of energy
If multi-stage rectifier circuits are implemented, then power conversion efficiency improves, but circuit complexity increases
Solution Approach 1:
The patent merges multiple rectifier stages into a unified CMOS circuit architecture where stages are integrated rather than cascaded as separate blocks. The multi-stage rectification process is implemented through coordinated operation of CMOS transistors within a single integrated circuit, sharing common components and control mechanisms. This merging approach achieves the power conversion efficiency benefits of multi-stage design while minimizing the complexity increase that would result from cascading discrete stages.
Solution Approach 2:
The patent implements universal CMOS transistor structures that perform multiple functions across different stages of the rectifier circuit. The same basic CMOS transistor configuration and control mechanism are reused throughout the multi-stage architecture, with each stage utilizing identical or similar circuit topologies. This universality reduces design complexity and facilitates integration while maintaining the power conversion efficiency advantages of multi-stage operation.
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, effectively harvesting RF energy across a broader power range compared to conventional designs.
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.