DC Block Patient Isolator With Split Absorbers for EMI Reduction
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Solution Overview
Problem
Microwave generators used in ablation procedures face interference issues due to unwanted radiation from DC block patient isolators, which affect the accuracy of sensor signals and violate regulatory radiation limits, particularly impacting the remote temperature probe measurements.
Innovation Solution
A DC block patient isolator design with a grounded structure and split high loss cavity resonance absorbers, featuring a 6 mm gap between proximal and distal absorbers, is employed to minimize radiation interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC block patient isolator is used to electrically isolate the patient from the microwave generator, then patient safety is improved, but unwanted radiation of high frequency energy occurs causing interference to sensor signals
Solution Approach 1:
A grounded shield is introduced as an intermediary component between the DC block and the microwave generator components. This shield acts as a mediator that captures and directs unwanted radiation away from sensitive sensor signals, thereby maintaining patient isolation while reducing interference to sensor accuracy
Solution Approach 2:
The design converts the harmful radiation effect into a beneficial outcome by using the radiation pattern to the advantage. The grounded shield strategically positioned around the DC block captures the radiated energy and redirects it through a controlled path that prevents interference with sensor signals, effectively transforming the harmful radiation into a manageable and non-interfering energy flow
2Reliability
If breaks are made in the outer conductor of the coaxial line within the DC block to achieve DC isolation, then patient isolation is improved, but unwanted radiation of high frequency energy occurs
Solution Approach 1:
The grounded shield is applied locally around the specific region where the outer conductor breaks are located within the DC block. This localized shielding approach targets the exact source of high frequency radiation without affecting the overall DC isolation function, providing precise control over the radiation issue while maintaining the necessary electrical isolation
3Measurement precision
If EMI shielding is added to reduce unwanted radiation, then sensor signal accuracy is improved, but device complexity increases
Solution Approach 1:
The EMI shielding is segmented into a modular grounded shield structure that can be independently positioned and adjusted around the DC block. This segmentation allows the shielding to be optimized for specific radiation patterns without creating a complex enclosing structure, maintaining sensor signal accuracy while keeping the overall device design manageable and adaptable
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 proposed design effectively reduces radiation interference by up to -9 dB at 4.9 GHz, ensuring accurate sensor measurements and compliance with regulatory radiation limits, thereby enhancing the operational reliability and safety of the microwave generator.
Implementation Method 1
at least one of the proximal absorber or the distal absorber is a high loss cavity resonance absorber
Implementation Method 2
a proximal absorber wrapped around a proximal portion of the DC block, and a distal absorber wrapped around a distal portion of the DC block
Implementation Method 3
DC block patient isolators operate with capacitive gaps across breaks in inner and outer conductors of a coaxial waveguide
Implementation Method 4
Low frequency signals see this coupling as high impedance, whereas an operational frequency of 2.45 GHz sees this coupling as low impedance
Data Source
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Figure 2B
AI summary
A patient isolator for a microwave generator includes a DC block grounded to a microwave module of the microwave generator, a proximal absorber wrapped around a proximal portion of the DC block, and a distal absorber wrapped around a distal portion of the DC block and separated from the proximal absorber by a gap.