Carbon Double-Layer Capacitor Low-Frequency Signal Coupling
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Solution Overview
Problem
Existing capacitive coupling circuits face limitations in low-frequency performance and direct current blocking, particularly in medical applications where signals with long time constants and low frequencies are required, often resulting in signal distortion and potential electrolytic reactions in biological tissues.
Innovation Solution
The use of symmetrical carbon double-layer capacitors, connected with both terminals floating, allows for efficient coupling of low-frequency alternating current signals while blocking direct current components, enabling the transmission of a wider range of signals with reduced distortion, and can be configured in series for redundancy and extended timing characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional film type or ceramic monolithic coupling capacitors are used, then the circuit structure is simple and manufacturing is easy, but the low-frequency performance is poor and signal distortion occurs
Solution Approach 1:
The patent changes the fundamental parameters of the capacitor by transitioning from conventional film or ceramic dielectrics to carbon-based double-layer capacitor technology. This parameter change enables exceptionally low-frequency signal coupling (below 20 Hz) while maintaining manufacturing feasibility through established carbon-based capacitor fabrication processes
Solution Approach 2:
The patent employs carbon-based composite materials in the double-layer capacitor structure, utilizing activated carbon or other porous carbon materials with high surface area. This composite material approach enables the capacitor to achieve the required low-frequency performance while maintaining a practical device structure
2Reliability
If conventional capacitors are used for direct current blocking, then the circuit is simple, but electrolytic reactions may occur in biological tissues
Solution Approach 1:
The patent changes the capacitor type to carbon-based double-layer capacitors, which have different electrochemical properties that prevent electrolytic reactions in biological tissues. This parameter change maintains reliability while managing the increased complexity through series configurations
Solution Approach 2:
The patent implements series configurations of multiple carbon-based capacitors to provide redundancy and prevent harmful electrolytic effects before they can occur. This beforehand cushioning approach ensures biological tissue safety while managing device complexity through structured arrangements
3Loss of information
If capacitors with large capacitance values are used to couple low-frequency signals, then signal distortion is reduced, but the capacitor size and cost increase
Solution Approach 1:
The patent changes the dielectric properties and capacitance density parameters by using carbon-based double-layer capacitor technology. This enables achieving large capacitance values (0.1 to 10 farads) in compact volumes, thereby reducing signal distortion without proportionally increasing capacitor size
Solution Approach 2:
The patent utilizes porous carbon composite materials with extremely high surface area to volume ratios. This composite material approach enables the capacitor to achieve the required large capacitance values in a compact form factor, minimizing volume while reducing signal distortion
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
This approach enables the effective coupling of exceptionally low-frequency signals, such as those below 20 Hz, into biological materials with minimal distortion and safety, maintaining low signal distortion and preventing harmful electrolytic effects, while supporting long time constants and large charge displacements.
Implementation Method 1
The conductors 20a and 20b are connected to plates 12a and 12b respectively as illustrated in FIG. 1a. The capacitance value C of capacitor 10 is given by C=∈S/d
Implementation Method 2
The earliest electrical storage device, the Leyden jar, was a simple capacitor. In its simplest conceptual form, a capacitor 10 as shown in FIG. 1 may be considered as two conductive plates 12a and 12b set parallel with an electrically nonconductive space 14 between them
Data Source
AI summary
A method and class of circuit configurations for coupling low-frequency signals from one stage of an electronic apparatus to another stage, from the outside world to such a stage, or from such a stage to the outside world, through the use of a plurality of symmetrical double-layer capacitors combined with other electronic components are disclosed. The capacitors are used for signal transmission while blocking direct current, rather than for energy storage. Use of double-layer capacitors in place of more conventional capacitors permits the transmission of a much wider range of signals with far less distortion. The technology is particularly well-adapted to use in medical devices, including bioelectronic stimulators, where redundant devices are required for safety in case of single component failure while unacceptable levels of distortion may occur when conventional components are used.