Ethernet Transceiver Noise Measurement via Signal Cancellation
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Solution Overview
Problem
Existing methods for measuring noise in Ethernet transceivers are unable to precisely estimate reflected noise due to changes in output terminal loading, leading to inaccurate noise measurement when data is transmitted from the other side of the cable.
Innovation Solution
A method and apparatus that utilize a pseudo noise generator and descrambler to generate and recover data sequences, allowing for noise cancellation and calculation of noise values under different transmission conditions to estimate noise from circuits, thereby isolating near-end noise during actual data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the other side of the cable transmits data to the Ethernet transceiver under test, then the loading on the output terminal changes making the measurement more representative of real-world conditions, but the reflected noise cannot be precisely estimated due to mixing with additional signals
Solution Approach 1:
The patent segments the noise measurement into two distinct components: reflected noise (measured when LP device transmits) and additional signals (measured when both devices transmit). By separating these components through controlled transmission scenarios, the patent enables precise estimation of reflected noise while maintaining the ability to measure under realistic dual-transmission conditions.
Solution Approach 2:
The patent changes the transmission state parameter of the link partner device between measurement phases. In the first phase, the LP device transmits data to establish loading conditions; in the second phase, both devices transmit to capture additional signals. By controlling these parameter changes, the patent isolates reflected noise from other signal components.
2Measurement precision
If data transmission is stopped at the other side of the cable to ensure detected noise only includes reflected noise, then measurement precision for reflected noise is improved, but the measurement does not represent real-world conditions where both sides transmit data
Solution Approach 1:
The patent performs preliminary measurement of reflected noise under controlled single-transmission conditions before conducting measurements under dual-transmission conditions. This preliminary action establishes a baseline for reflected noise that can be used to interpret and separate noise components in more complex real-world transmission scenarios.
Solution Approach 2:
The patent uses feedback from the first measurement phase (where LP device transmits alone) to inform the second measurement phase (where both devices transmit). The reflected noise characteristics established in phase one serve as a reference that feedbacks into the analysis of phase two measurements, enabling separation of reflected noise from additional signals even when both devices are transmitting.
Data Source
AI summary
A method and a measuring apparatus for measuring noise of a device under test (DUT) is provided, wherein the DUT is connected to a link partner (LP) device via a cable, and the measuring apparatus is coupled to the DUT and LP device. The method includes: controlling the LP device to transmit a far-end data sequence to the DUT according to transmission data; controlling the DUT to recover the transmission data for generating aided-data sequence according to the transmission data, wherein the aided-data sequence is configured to perform cancellation with a received far-end data sequence to generate a cancellation result; generating a first noise value and a second noise value in a first training phase and a second training phase, respectively; and estimating noise from at least one circuit according to the first noise value and the second noise value.