Feedforward Echo Cancellation Circuit for High-Frequency Impedance Mismatch
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Solution Overview
Problem
In full-duplex communication systems, existing echo cancellation devices struggle to accurately simulate the impedance on the output path, leading to ineffective echo cancellation, particularly in the high-frequency band due to varying impedances in cables, transformers, and chip packages.
Innovation Solution
A feedforward echo cancellation device is implemented, which includes a first impedance circuit, an echo cancellation current generating circuit, a circuit module, and a second impedance circuit, dynamically adjusting impedance values and using a programmable gain amplifier to generate a compensation signal that matches the echo signal, thereby compensating for energy mismatches and optimizing cancellation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a variable impedance circuit is used to simulate the output path impedance, then the echo cancellation device can generate echo cancellation signals, but it fails to accurately simulate the impedance in the high-frequency band due to multiple different impedances in the output path
Solution Approach 1:
The patent divides the single variable impedance circuit into multiple impedance circuits (first impedance circuit and second impedance circuit) with different impedance values. Each impedance circuit handles a specific frequency range, with the first impedance circuit covering lower frequencies and the second impedance circuit covering high frequencies. This segmentation allows accurate impedance simulation across the entire frequency spectrum while maintaining manageable circuit complexity.
Solution Approach 2:
The patent employs dynamic switching between different impedance circuits based on frequency detection. The echo cancellation device dynamically selects which impedance circuit to use depending on the frequency characteristics of the transmission signal, enabling accurate impedance simulation that adapts to varying frequency conditions rather than relying on a fixed impedance value.
2Reliability
If a single impedance value is used in the echo cancellation device, then the device structure is simple, but it cannot compensate for energy mismatches in the high-frequency band
Solution Approach 1:
The patent applies different impedance values to different frequency ranges rather than using a uniform impedance across all frequencies. The first impedance circuit with first impedance value handles the general frequency range, while the second impedance circuit with second impedance value specifically addresses the high-frequency band. This local quality approach ensures optimal echo cancellation performance for each frequency range without requiring complex multi-parameter adjustment.
Data Source
AI summary
A feedforward echo cancellation device includes: a first impedance circuit for responding to a transmission current to output a first current to a node; an echo cancellation current generating circuit for drawing an echo cancellation current from the node; a circuit module that is coupled to the echo cancellation current generating circuit and the node has a first impedance value adjusted based on a system convergence index of a communication device, where the first impedance value is used to determine a gain of a programmable gain amplifier in the communication device; and a second impedance circuit for responding to the transmission current to output a second current to the node, where a second impedance value of the second impedance circuit is adjusted based on the first impedance value of the circuit module accordingly. Specifically, the node is coupled to an input terminal of the programmable gain amplifier.