Echo Canceller Reuse for Transceiver Calibration
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Solution Overview
Problem
High-speed Ethernet transceivers face performance degradation due to PVT variations and echo channel issues, which existing calibration methods fail to address effectively, especially in long cable lengths and during field operations.
Innovation Solution
A transceiver circuit and method that uses echo canceller circuitry to generate test signals and loop them back between transmit and receive paths for calibration, allowing digital processing to analyze and optimize transceiver parameters, including transmit phase and gain matching, to compensate for echo and distortion, thereby improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If initial training methods are used to optimize transceiver parameters, then receiver parameters can be calibrated, but PVT variations over time cause performance degradation that cannot be compensated
Solution Approach 1:
The patent performs preliminary characterization of PVT effects at the chip fabrication stage by measuring transceiver parameters across process, voltage, and temperature variations. These measurements are used to create lookup tables and calibration data that are stored in non-volatile memory, enabling the transceiver to compensate for PVT variations during field operation without requiring re-calibration.
Solution Approach 2:
The patent implements continuous monitoring and adjustment of transceiver parameters during operation. The system measures actual performance parameters, compares them against optimal values from lookup tables, and adjusts calibration parameters dynamically to compensate for PVT drift, ensuring sustained performance stability.
2Device complexity
If echo canceller circuitry is reused for both echo cancellation and calibration, then device complexity is reduced, but calibration functionality must be integrated with existing echo cancellation resources
Solution Approach 1:
The patent makes the echo canceller circuitry multi-functional by configuring it to perform both its primary function of echo cancellation during normal operation and a secondary function of parameter calibration during initialization. The same hardware resources (ADCs, DACs, signal paths) are time-multiplexed between calibration and operational modes, eliminating the need for separate calibration circuitry.
Solution Approach 2:
The transceiver uses its own operational echo canceller circuitry to perform self-calibration without requiring external calibration equipment. The system generates test signals, routes them through the transmit and receive paths, and uses the echo canceller to measure and optimize parameters, making the calibration process self-contained and simplifying manufacturing.
3Measurement precision
If test signals are looped back through the transmit path to the receive path for calibration, then accurate performance measurement is achieved, but signal distortion and echo must be compensated during calibration
Solution Approach 1:
The patent converts the harmful echo and distortion effects into useful calibration information. By intentionally injecting test signals and measuring the echoed and distorted versions returned through the transmit path, the system characterizes the actual signal degradation that occurs during operation. The echo canceller processes these distorted signals to extract accurate parameter measurements, turning the previously harmful effects into the basis for accurate calibration.
Data Source
AI summary
A method of operating a transceiver integrated circuit is disclosed. The method comprises generating test signals directed to testing one or more transceiver parameters. The test signals are transmitted from a digital domain to an analog domain along a transmit path, and looped-back from the transmit path to a receive path. Echo canceller circuitry coupled between the transmit path and the receive path is trained and generates a filtered output representing a metric indicative of the one or more transceiver parameters.