RF-DC Rectifier Topology Using N-Well CMOS to Cut Parasitic Capacitance
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Solution Overview
Problem
Conventional RF-DC converters face inefficiencies, increased complexity, and higher manufacturing costs due to the use of twin-well CMOS processes and lack of body biasing in transistor configurations, leading to larger component sizes and higher maintenance costs.
Innovation Solution
A RF-DC converter design utilizing an n-well process for fabricating NMOS and PMOS transistors in a compact configuration, with a cross-coupled differential-drive (CCDD) rectifier, featuring a first stage with both NMOS and PMOS transistors and a second stage with only PMOS transistors, reducing component size and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If twin-well CMOS process is used for fabricating RF-DC converter, then transistor performance and reliability are improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts the p-well fabrication step from the conventional twin-well CMOS process, retaining only the n-well process. This is achieved by using n-well transistors for both NMOS and PMOS devices, eliminating the need for separate p-well regions and simplifying the manufacturing process while maintaining device functionality
Solution Approach 2:
The patent changes the fabrication parameter from twin-well to single n-well process. By modifying the manufacturing approach to use only n-well transistors with appropriate body biasing configurations, the complex twin-well process is replaced with a simpler single-process fabrication method that reduces cost while preserving transistor performance
2Ease of operation
If conventional RF-DC converter design is used, then basic rectification function is achieved, but device complexity and component size increase
Solution Approach 1:
The patent merges the body biasing control into the existing transistor structure by connecting the body terminals of n-well transistors to appropriate potential nodes. This integration eliminates the need for separate body biasing circuits and reduces component count while maintaining the rectification function
Solution Approach 2:
The patent makes the n-well transistors perform multiple functions by utilizing their body effect for both switching and body biasing purposes. The same transistors that perform rectification also provide body biasing when their body terminals are connected to appropriate nodes, eliminating the need for dedicated body biasing structures
3Ease of operation
If conventional RF-DC converter design is used, then rectification is achieved, but parasitic capacitances increase reducing operating speed
Solution Approach 1:
The patent extracts and eliminates the p-well regions that contribute to parasitic capacitances. By using only n-well transistors with properly managed body terminals, the parasitic capacitances associated with p-well structures are removed, thereby improving the operating speed of the rectifier
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 design achieves efficient RF energy harvesting with reduced chip size, lower parasitic capacitances, and lower production costs while maintaining high operating speed and stability, suitable for powering devices in environments with abundant RF signals.
Implementation Method 1
lower parasitic capacitances
Implementation Method 2
rectification is a process of converting radio frequency (RF) signals into direct current (DC)
Data Source
AI summary
A radio frequency to direct current (RF-DC) converter for energy harvesting includes a first cross-coupled circuit and a second cross-coupled circuit. The first cross-coupled circuit includes a pair of NMOS transistors and a pair of PMOS transistors. The second cross-coupled circuit is connected to an output of the first cross-coupled circuit and includes four cross-coupled PMOS transistors. Each of the NMOS transistors and PMOS transistors are fabricated on a substrate using n-well process. An RF voltage source is connected to the RF-DC converter to which an antenna and balun device are connected. An output circuit is connected the second cross-coupled circuit. Multiple stages identical to the second cross-coupled circuit including only PMOS transistors may be added between the output of the second cross-coupled circuit and the output circuit for greater amplification of the harvested energy.