Single-Ended Signal Transmission Using Return-Path Current Cancellation
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Solution Overview
Problem
Common mode noise in single ended signal transmission leads to reduced signal-to-noise ratio and errors in receivers, necessitating differential signaling which increases cost and size due to the need for two electrical conductors per signal path.
Innovation Solution
A noise cancellation system using a first noise cancellation circuit with compensation impedances and an impedance buffer circuit to generate a noise cancelling current that opposes the noise generating current in the return path, reducing common mode noise without requiring additional conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If differential signaling is used to reduce common mode noise, then noise reduction is achieved, but cost and size increase due to requiring two electrical conductors per signal path
Solution Approach 1:
The patent introduces a noise cancellation circuit as an intermediary component that generates a cancellation current through compensation impedances. This cancellation current opposes the noise generating current in the return path, effectively reducing common mode noise. The intermediary circuit allows single-ended signaling to achieve noise performance comparable to differential signaling while maintaining only one electrical conductor per signal path, thus resolving the contradiction between noise reduction and conductor count.
2Device complexity
If single ended signaling is used to reduce cost and size, then conductor count is reduced to one per signal path, but common mode noise increases reducing signal to noise ratio
Solution Approach 1:
The patent converts the harmful noise generating current into a beneficial cancellation mechanism. By measuring the noise generating current through the input impedance and generating an equal and opposite cancellation current through compensation impedances, the system transforms the original harmful effect into a useful noise reduction mechanism. This allows single-ended signaling to maintain low conductor count while achieving noise performance through active cancellation.
Solution Approach 2:
The noise cancellation circuit employs feedback by continuously monitoring the noise generating current through the input impedance and adjusting the cancellation current accordingly. The buffer circuit isolates the compensation impedances from loading effects, ensuring accurate feedback measurement. This feedback mechanism enables the system to dynamically counteract common mode noise while maintaining single-ended signaling simplicity.
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
Reduces common mode noise effectively while maintaining isolation between ground structures, achieving cost and size benefits comparable to single ended signaling with only one electrical contact per signal path.
Implementation Method 1
each first compensation impedance is configured to generate a first noise cancellation sub-current when a voltage of a single ended signal, received by a corresponding first buffer input, varies
Implementation Method 2
flows through an inductance in a return path, between the transmitting circuit and the receiving circuit
Data Source
AI summary
Techniques are provided which reduce common mode noise voltage in single ended signal transmission. The common mode noise voltage is generated by a noise generating current flowing through an inductance of a return path between a transmitting circuit and a receiving circuit. The common mode noise voltage may be diminished by generating a noise cancelling current which flows through the inductance in the return path in a direction opposite to the flow of the noise generating current. As a result, a magnitude of noise current flowing through the inductance is diminished. Further the transmitting circuit and receiving circuit are isolated, by using buffering, from ground plane(s) of the transmitting and/or the receiving circuits so that such circuits are substantially unaffected by this common mode noise suppression technique.