Full-Duplex Hybrid Circuit for Wideband Echo Cancellation
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Solution Overview
Problem
Full duplex communication systems face challenges in suppressing echo signals, which dominate the desired receive signal and saturate analog-to-digital converters, especially when reflections along the transmission medium cannot be distinguished from the desired receive signal, leading to incomplete echo suppression and noise leakage.
Innovation Solution
A hybrid transmission arrangement is placed across the amplifier's input and output nodes, utilizing capacitive elements and phase matching circuits to achieve signal cancellation and isolation, thereby reducing echo and extending bandwidth while maintaining low loss and low noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a hybrid circuit is placed between amplifier output and transmission medium to suppress echo, then echo suppression is improved, but signal loss increases and bandwidth is limited
Solution Approach 1:
The patent introduces a hybrid circuit as an intermediary component placed between the amplifier input and transmission medium. This hybrid circuit mediates the signal path by providing a controlled impedance interface that enables echo suppression through signal cancellation while maintaining low loss characteristics. The hybrid circuit acts as a mediator that separates the transmit and receive paths, allowing independent optimization of each path.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the impedance values and electrical lengths of transmission lines within the hybrid circuit to achieve optimal echo cancellation across a wide bandwidth. By varying the characteristic impedance and phase characteristics of the transmission lines, the circuit maintains low signal loss while effectively suppressing echo signals across multiple frequency ranges.
2Object-affected harmful factors
If a hybrid circuit is placed between amplifier output and transmission medium to suppress echo, then echo suppression is improved, but bandwidth is limited
Solution Approach 1:
The patent segments the signal path into multiple transmission line sections with different electrical lengths and impedance values. This segmentation allows each section to be optimized for specific frequency ranges, collectively providing wideband echo suppression. The segmented structure enables independent tuning of different frequency bands to extend the operational bandwidth.
Solution Approach 2:
The patent extends the solution from a single-frequency approach to a multi-dimensional frequency response by using multiple transmission line sections with varying electrical lengths. This dimensional expansion in the frequency domain allows the hybrid circuit to maintain effective echo suppression across a broad bandwidth, transforming a narrowband solution into a wideband solution.
3Device complexity
If ADC operates without accounting for echo signal, then ADC settings are simple, but ADC becomes saturated by echo signal
Solution Approach 1:
The patent applies preliminary action by suppressing the echo signal in the analog domain before the ADC conversion process. The hybrid circuit performs echo cancellation upfront, preventing the echo from reaching the ADC and causing saturation. This preliminary suppression simplifies the ADC operation settings since no complex digital echo cancellation is needed, and the ADC can operate within its dynamic range.
4Object-affected harmful factors
If hybrid circuit is designed for immediate echo suppression, then isolation between Tx and Rx is improved, but reflections cannot be suppressed
Solution Approach 1:
The patent incorporates feedback mechanisms through the hybrid circuit structure that continuously monitors and cancels echo signals. The hybrid circuit provides a feedback path that allows the system to adapt to varying reflection conditions by adjusting the cancellation signals in real-time, enabling suppression of both immediate echo and reflected signals.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves theoretically 0 dB loss with improved bandwidth support, effectively isolating the transmitter from the receiver and compensating for phase response and gain roll-off, enhancing the isolation bandwidth up to 2 GHz and reducing power consumption in line drivers.
Implementation Method 1
the cancellation circuit for canceling the input signal with a signal of equal amplitude and inverse phase is provided with compressors and an expander
Implementation Method 2
utilizing capacitive elements and phase matching circuits to achieve signal cancellation and isolation, thereby reducing echo
Data Source
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AI summary
The present document discloses a transmission arrangement for coupling an amplifier to a transmission medium. An input node of the amplifier is couplable to a transmitter and an output node of the amplifier is couplable to a terminal of the transmission medium. The transmission arrangement may comprise a first branch coupled between the input node of the amplifier and an intermediate node which is couplable to a receiver. The transmission arrangement may further comprise a second branch coupled between the output node of the amplifier and the intermediate node. In particular, the first branch comprises a first capacitive element, while the second branch comprises a second capacitive element. Furthermore, at least one of the first and second branches further comprises a phase matching circuit coupled in series with the respective capacitive element.