Single-Ended Coax Transmission Circuit for Noise-Resilient Bidirectionality
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Solution Overview
Problem
Conventional CoaXPress interface systems are expensive due to the use of external off-the-shelf PHYs, and they face challenges with signal integrity and noise coupling in bi-directional single-ended transmission over coaxial cables.
Innovation Solution
The implementation of bi-directional single-ended transmission systems using a coaxial cable with passive components such as inductors and resistors, which reduce the need for expensive external PHYs and improve signal integrity through low-speed injection and extraction circuitry and high-pass filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external off-the-shelf PHYs are used to implement CXP interface, then signal transmission capability is improved, but system cost increases
Solution Approach 1:
The patent combines the PHY functionality directly into the ASIC chip, merging previously separate components (ASIC + external PHY) into a single integrated unit. This eliminates the need for expensive external off-the-shelf PHYs while maintaining signal transmission capability through carefully designed internal circuitry including differential to single-ended conversion circuits and impedance matching networks.
Solution Approach 2:
The ASIC chip is designed to perform multiple functions: it serves as both the processing unit and the PHY interface, handling both data processing and signal transmission over coaxial cable. This multi-functionality eliminates the need for dedicated external PHY components, reducing system cost while maintaining reliable signal transmission.
2Device complexity
If bi-directional single-ended transmission is implemented over coaxial cable, then cost is reduced, but noise coupling and signal integrity deteriorate
Solution Approach 1:
The patent introduces intermediary circuits including differential to single-ended conversion circuits and impedance matching networks that act as mediators between the digital logic and the coaxial cable transmission medium. These intermediary circuits properly terminate differential signals and match impedances, preventing noise coupling and signal reflections that would otherwise occur in direct single-ended connections.
Solution Approach 2:
The patent changes signal parameters by converting between differential and single-ended modes depending on the transmission direction and speed requirements. High-speed downlink uses differential signaling for noise immunity, while low-speed uplink uses single-ended signaling for cost effectiveness. Impedance values are also carefully controlled and matched at various points in the circuit to minimize reflections and noise coupling.
3Device complexity
If passive components are used for signal transmission, then system cost is reduced, but signal integrity at different speeds becomes challenging
Solution Approach 1:
The patent applies different circuit topologies and component values optimized for specific signal speeds and directions. High-speed downlink paths use differential signaling with specific impedance matching, while low-speed uplink paths use single-ended signaling with different termination schemes. Each transmission path has locally optimized components and circuit arrangements tailored to its specific speed and signal characteristics, ensuring signal integrity across different operating conditions.
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
This approach provides better low-speed and high-speed signal integrity, reduces noise coupling, and mitigates baseline wander distortion, resulting in a more cost-effective and reliable transmission system.
Implementation Method 1
an inductor and a resistor connected in series between the first node and the third node
Implementation Method 2
an inductor and a resistor connected in series between the first node and the third node
Implementation Method 3
a shunt resistor connected between the third node and a ground node
Data Source
AI summary
Systems for bi-directional single-ended transmission are described. For example, a system may include a receiver with a first differential input terminal and a second differential input terminal, wherein the first differential input terminal is coupled to a first node and the second differential input terminal is coupled to a second node; a transmitter with an output terminal coupled to a third node; a first inductor connected between the first node and the third node; a second inductor connected between the second node and the third node; and a shunt resistor connected between the third node and a ground node.