Echo Canceller Offset Calibration for Slicer Level Shifts
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Solution Overview
Problem
Echoes in communication systems caused by mismatched transmission line impedances or improper hybrid architecture designs lead to increased quantization noise and reduced signal-to-noise ratio (SNR) due to shifted slicer levels in analog-to-digital circuits.
Innovation Solution
An echo cancelling system and method that includes a digital-to-analog converter, a first echo canceller circuit, a processor circuit, an analog-to-digital converter, and a storage circuit, which generates an echo cancelling signal, updates an offset value based on error values, and uses a look-up table to maintain the output signal at a middle value between shifted slicer levels, minimizing quantization noise and improving SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If echo cancelling technology is used to cancel echoes caused by impedance mismatch or improper hybrid architecture, then echo reduction is achieved, but quantization noise increases and signal-to-noise ratio deteriorates due to slicer level shifts
Solution Approach 1:
The system performs preliminary calibration to determine optimal slicer level offset values before normal operation. The calibration process pre-computes compensation values that are stored and applied during subsequent echo cancelling operations, preventing quantization noise issues before they occur
Solution Approach 2:
The system dynamically adjusts the slicer level offset parameter based on calibration results. By changing the offset parameter from its default value to a calibrated value, the system compensates for slicer level shifts and maintains optimal signal-to-noise ratio while preserving echo cancelling performance
2Device complexity
If fixed slicer levels are used in analog-to-digital conversion, then circuit design is simplified, but output signal deviates from middle value between slicer levels causing increased quantization noise
Solution Approach 1:
The system modifies the slicer level offset parameter to compensate for shifts. By adjusting this parameter from its default fixed value to a calibrated value, the output signal is realigned to the middle value between slicer levels, minimizing quantization noise while maintaining the simplicity of fixed slicer level architecture
Solution Approach 2:
The system uses calibration feedback to determine the optimal offset value. During calibration, the system measures the actual slicer level positions and uses this feedback information to compute and apply the appropriate offset compensation, ensuring accurate output signaling without increasing circuit complexity
Data Source
AI summary
A digital-to-analog converter circuit generates an analog transmitted signal according to a digital transmitted signal. A first echo canceller circuit generates a first echo cancelling signal according to the digital transmitted signal. A processor circuit generates an analog processed signal according to the analog transmitted signal, the first echo cancelling signal, and a received signal. An analog-to-digital converter circuit generates a digital value according to the analog processed signal and two slicer levels of a plurality of slicer levels. A storage circuit stores a look-up table. The look-up table records an offset value corresponding to the digital value. The storage circuit further outputs a first output signal according to the digital value and the offset value. The offset value is updated according to an error value associated with the first output signal.