Echo-Canceling Line Driver Circuit With Active Termination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In line driver/receiver circuits, especially with active termination impedance, existing echo cancellation methods fail to effectively eliminate the strong transmit signal distortion that degrades the signal-to-noise ratio (SNR) of the receive signal, necessitating improved echo cancellation techniques.
Innovation Solution
The implementation of complex sense impedances with transconductance amplifiers to match the load impedance, using a pure resistive bridge across the sense impedances to cancel the transmit signal, and adjusting the drive/termination impedance based on line driver and transconductance amplifier gains to achieve effective echo cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a resistor bridge is used for echo cancellation in line drivers with active termination impedance, then the transmit signal can be canceled at the receiver input, but the receive signal is completely blocked and no receive signal is present at the line driver interface
Solution Approach 1:
The system is divided into two separate paths: one path through the resistor bridge for echo cancellation of the transmit signal, and another path through the transmission line for receiving the actual receive signal. This segmentation allows the transmit signal to be canceled in one path while preserving the receive signal in the other path.
Solution Approach 2:
The invention introduces an intermediary signal path that allows the receive signal to bypass the resistor bridge. The receive signal is coupled to the receiver input through the transmission line without passing through the echo cancellation bridge, thus avoiding complete blocking while still achieving transmit signal cancellation.
2Use of energy by moving object
If the output signal levels are lowered to reduce power consumption, then the supply voltage and power consumption are reduced, but the echo cancellation performance degrades
Solution Approach 1:
The invention changes the impedance parameters of the bridge resistors to achieve effective echo cancellation at lower output signal levels. By optimizing the resistor values in the bridge circuit, the system maintains good echo cancellation performance even when the transmit signal power is reduced, thereby enabling lower supply voltage and power consumption.
3Power
If the drive impedance is set to match the load impedance for optimal power transfer, then the signal levels are maximized, but the echo cancellation becomes ineffective
Solution Approach 1:
The invention applies different impedance values to different parts of the circuit: the drive impedance is optimized for power transfer to the transmission line, while the bridge resistors are given specific impedance values optimized for echo cancellation. This local differentiation of impedance characteristics allows both objectives to be achieved simultaneously in their respective domains.
Data Source
AI summary
In a line driver/receiver circuit where the line driver is connected with its output terminals to a load for supplying a transmit signal thereto and where the receiver is connected with its input terminals to the load for simultaneously receiving a receive signal therefrom, the transmit signal on the input terminals of the receiver is canceled by connecting the output terminals of the line driver to the load via equal complex sense impedances of an impedance value that is much smaller than the impedance value of the load impedance to match the load impedance, connecting the input terminals of the receiver to the load via equal first resistors and to respective output terminal of the line driver via equal second resistors, and providing transconductance amplifiers to sense the voltage across the sense impedances and supply corresponding currents to respective input terminal of the line driver.