Microstrip Impedance Transformer for Electrosurgical Cable Matching
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Solution Overview
Problem
Conventional electrosurgical instruments experience power loss and unwanted heating due to impedance mismatch between the electrosurgical generator and the instrument cable, leading to energy reflections during the delivery of electromagnetic energy to biological tissue.
Innovation Solution
A microstrip impedance transformer is used to match the impedance between a microwave feed line and an instrument cable with a lower impedance, preventing energy coupling into an internal passageway and minimizing power loss and heating effects, by employing a planar dielectric substrate with a microstrip conductor layer and ground conductor layer, and a hollow conduit configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional coaxial cable is used to transmit microwave energy from the generator to the instrument, then the energy can be delivered to the treatment site, but impedance mismatch occurs between the feed line and the instrument cable, causing power loss and unwanted heating
Solution Approach 1:
A microstrip impedance transformer is introduced as an intermediary component between the coaxial feed line and the instrument cable. This transformer serves as a mediator that gradually transitions the impedance from the feed line value to the instrument cable value, preventing direct impedance mismatch and the associated power loss and heating effects.
Solution Approach 2:
The impedance transformer utilizes a gradual change in geometric parameters (such as the width of the microstrip conductor) along its length to achieve a progressive impedance transition. By varying the physical dimensions of the microstrip structure, the characteristic impedance changes continuously from the feed line impedance to the instrument cable impedance, eliminating reflections and power loss.
2Object-affected harmful factors
If an impedance transformer structure is introduced to match impedance, then power loss and heating effects are minimized, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical impedance matching structures with a planar microstrip transmission line design. Instead of using traditional three-dimensional mechanical transformers or adjustable mechanisms, the impedance transformation is achieved through a two-dimensional printed circuit board-style microstrip structure, significantly simplifying the mechanical complexity while maintaining effective impedance matching.
Solution Approach 2:
The impedance transformer transitions from traditional three-dimensional volumetric structures to a two-dimensional planar microstrip configuration. By spreading the impedance transformation across a flat surface area rather than concentrating it in a compact volume, the design achieves effective impedance matching with reduced structural complexity and improved manufacturability.
3Productivity
If the instrument cable has a lower impedance than the feed line, then efficient energy coupling is achieved, but energy may be coupled into the internal passageway causing heating of liquids within it
Solution Approach 1:
The microstrip impedance transformer creates localized regions with different electromagnetic field distributions. By carefully designing the microstrip geometry and positioning, the electric field is concentrated in specific areas that favor coupling into the instrument cable while minimizing field presence in regions that could couple into the internal passageway, thus preventing unwanted heating of liquids.
Solution Approach 2:
The impedance transformer acts as an intermediary that controls the distribution and direction of electromagnetic energy flow. It guides the energy preferentially into the instrument cable transmission path while isolating the internal passageway from significant energy coupling, thereby maintaining efficient energy delivery to the treatment site without heating liquids in the passageway.
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 microstrip impedance transformer effectively matches the impedance, reducing power loss and reflections, ensuring efficient energy delivery to the treatment site while preventing unwanted heating of instruments and liquids within the hollow conduit.
Implementation Method 1
a microstrip impedance transformer arranged to match the first impedance and the second impedance
Implementation Method 2
a microwave feed line for carrying microwave electromagnetic (EM) energy having a frequency from an electrosurgical generator
Implementation Method 3
an instrument cable for insertion into a patient's body to a treatment site, the instrument cable comprising: a coaxial transmission line for conveying the microwave EM energy
Implementation Method 4
The microstrip impedance transformer is configured to perform impedance matching between the microwave feed line and the instrument cable in a manner that does not adversely affect a separate feed into the internal passageway
Data Source
AI summary
A microstrip impedance transformer that permits efficient (i.e. low loss) coupling of a microwave feed line (e.g. a conventional 50Ω coaxial cable) to an instrument cable, where the instrument cable has a lower impedance (e.g. in the range 12 to 14Ω) and includes an internal passageway. The microstrip impedance transformer is configured to perform impedance matching between the microwave feed line and the instrument cable in a manner that does not adversely affect a separate feed, e.g. for delivering fluid, into the internal passageway.