Adaptive Negative Resistance Circuit for Crosstalk Suppression
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Solution Overview
Problem
Existing methods for suppressing crosstalk voltage on a common return wire in signal cables are ineffective when only the near end of the cable is accessible, as they require known common wire impedance or are not applicable for reducing crosstalk on a common return wire.
Innovation Solution
An adaptive on-line method involving a negative resistance circuit with adjustable output resistance is connected between the common wire terminal and a common point, with an auxiliary current determined to nullify the voltage level, using feed-forward or feedback modes to adjust the resistance and cancel the common wire ohmic resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a negative impedance circuit is connected in series with the common wire to compensate for crosstalk, then crosstalk voltage is reduced, but the method requires knowledge of the common wire impedance which is not always available during system operation
Solution Approach 1:
The patent applies preliminary action by measuring and storing the common wire impedance characteristics during an initial calibration phase when both cable ends are accessible. This pre-acquired impedance data is then used during normal operation to configure the negative impedance circuit for crosstalk cancellation, eliminating the need to know impedance values during actual system operation.
Solution Approach 2:
The patent applies preliminary action by pre-determining the negative impedance value based on cable characteristics measured during installation or initial setup. This pre-calculated negative impedance is then programmed into the circuit, enabling crosstalk suppression without requiring real-time impedance measurement or access to both cable ends during operation.
2Object-affected harmful factors
If feedback circuit is used to shift signal voltage at far end in opposing phase direction, then negative impedance effect is achieved, but this solution is not applicable for reducing crosstalk voltage on common return wire
Solution Approach 1:
The patent applies the taking out principle by extracting the negative impedance function from a complex feedback circuit configuration and implementing it directly in series with the common wire. This simplified approach uses a dedicated negative impedance circuit rather than a general-purpose feedback circuit, making the solution specifically applicable to crosstalk suppression on common return wires.
Solution Approach 2:
The patent applies the intermediary principle by introducing a negative impedance circuit as a mediator element connected in series with the common wire. This intermediary component directly counteracts the crosstalk voltage by providing an opposing voltage signal, enabling effective crosstalk suppression without requiring complex feedback circuitry at the far end.
3Object-affected harmful factors
If virtual remote sensing technique is used to measure conductor resistance, then output resistance compensation is achieved, but this solution is not applicable for reducing crosstalk voltage on common return wire
Solution Approach 1:
The patent applies the blessing in disguise principle by converting the harmful crosstalk voltage caused by common wire resistance into a useful measurement signal. By injecting a test current through the common wire and measuring the resulting voltage drop, the system determines the wire resistance and uses this information to configure the negative impedance circuit for crosstalk cancellation, turning the problematic resistance into a beneficial calibration parameter.
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
Effectively suppresses crosstalk voltage on a common return wire by adjusting the negative resistance to nullify the common wire resistance, improving signal quality and reducing interference, even when the cable is in operation and the far end is not accessible.
Implementation Method 1
connecting a negative resistance circuit having an adjustable output negative resistance between the common wire terminal at the device port and a common point at the device
Data Source
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AI summary
A method and circuit for providing adaptive suppression of signal crosstalk appearing on a common return wire in a signal cable connected to a device. The method steps comprise connecting an adjustable negative resistance circuit between the common wire terminal and a common point at the device; determining an auxiliary current (Iaux) such that is flowing through at least one of the cable wires and returns through the common wire; sensing the voltage between selected at least one of the cable wire terminals at the device port and the common point, while ensuring that this level is substantially affected by Iaux; measuring a level of the sensed voltage according to a predefined level measurement procedure; and adjusting the negative resistance so as to nullify said voltage level, thereby effectively cancelling the common wire ohmic resistance.