Active Body-Shielding Circuit for Intra-Body Sensor Noise Cancellation
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Solution Overview
Problem
Medical intra-body sensors are vulnerable to electrical interference from external and internal sources, such as 50/60 Hz line voltage and devices like pacemakers, which corrupts precision measurements and poses safety risks due to inadequate shielding.
Innovation Solution
An active noise cancellation device using a low-impedance body connection electrode actively drives the patient's body with a limited current to counteract interfering voltages, employing a current-limited feedback network and on-chip sensor circuitry to null out noise and reduce leakage currents, while ensuring patient safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional passive shielding is used for intra-body sensors, then device complexity is reduced, but measurement precision deteriorates due to inadequate noise cancellation
Solution Approach 1:
The patent implements active shielding by feeding back a corrected drive signal to the electrode. The system measures the potential on the patient's body, compares it with the desired potential, and adjusts the drive signal to cancel interference voltages. This feedback mechanism dynamically compensates for electrical interference from external sources and internal devices, significantly improving measurement precision without requiring complex passive shielding structures.
Solution Approach 2:
The patent replaces traditional mechanical/passive shielding approaches with an electrical/active control system. Instead of using complex physical barriers or grounded shields, the system uses electronic feedback to generate counter-voltages that actively cancel interference. This substitution of passive mechanical shielding with active electrical control achieves superior noise cancellation while maintaining simpler device architecture.
2Object-affected harmful factors
If active shielding with high current is applied to the patient's body, then noise cancellation effectiveness is improved, but patient safety deteriorates due to excessive leakage current
Solution Approach 1:
The patent carefully controls the parameters of the drive signal applied to the patient's body. By adjusting the amplitude, frequency, and waveform of the corrected signal within safe physiological limits, the system achieves effective noise cancellation while maintaining patient safety. The feedback mechanism automatically adapts signal parameters to cancel interference without exceeding safety thresholds for current exposure.
Solution Approach 2:
The patent converts the potentially harmful drive signal into a beneficial tool for noise cancellation. By using the same electrode that could deliver harmful current to instead deliver a carefully controlled corrective signal, the system transforms a safety risk into a protective mechanism. The feedback control ensures the corrective signal cancels interference while remaining within safe current limits, effectively using the potential harm as the basis for protection.
3Adaptability or versatility
If sensor wire length is increased to reach distant measurement sites, then adaptability is improved, but reliability deteriorates due to increased susceptibility to electrical interference
Solution Approach 1:
The patent uses feedback control to continuously monitor and correct interference on the sensor wire. The system measures the actual potential at the sensor location and adjusts the drive signal to compensate for interference accumulated along the wire length. This real-time correction enables long sensor wires to maintain signal integrity despite increased exposure to electrical interference, allowing access to distant measurement sites while preserving reliability.
Solution Approach 2:
The patent applies preliminary correction to the drive signal before it reaches the sensor. By calculating and applying the necessary compensation in advance based on expected interference patterns and measured body potential, the system pre-corrects the signal to counteract interference that will occur along the wire path. This preliminary action prevents interference from degrading the signal, enabling reliable measurements from distant sites.
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
Significantly reduces electrical interference in sensor measurements, speeds up settling times, and enhances safety by limiting patient currents, effectively using the body as an active shield against noise and interference.
Implementation Method 1
a low-impedance body connection electrode adapted to actively drive the patient's body with a limited current to thereby use the patient's body as an active shield
Implementation Method 2
providing a feedback branch connecting said output connection with said first input connection, and limiting an error correction current through said feedback branch
Data Source
AI summary
An active noise cancellation device (2) for a medical device includes an active circuit having a first input connection (8), a second input connection (10), and an output connection (12). The second input connection (10) is connected to at least one predetermined reference signal. The active noise cancellation device (2) further includes a low-impedance body connection electrode (4) adapted to be in electrical contact with a bloodstream of a subject, wherein the low-impedance body connection electrode (4) is connected to said first input connection (8), and a feedback branch (14) connecting the output connection (12) with the first input connection (8). The feedback branch (14) comprises a current limiting circuit (18) to limit a current through said feedback branch (14) to be lower than a predetermined current.