Adaptive Echo Cancellation in RF Repeaters Using Weighted Power Spectrum
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Solution Overview
Problem
Existing RF repeaters face challenges in minimizing residual echo, especially for large repeater gains or difficult cancellation conditions, which can lead to oscillation and suboptimal signal transmission in wireless communication systems.
Innovation Solution
An adaptive echo cancellation system using a weighted power spectrum is implemented in an on-frequency RF repeater, which includes a digital intermediate frequency stage and internal digital echo cancellation performed by a digital signal processor. The system adjusts the repeater gain outside the echo cancellation loop and filters the power spectrum to reduce autocorrelation width, allowing for incremental adaptation and stability maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the forward gain of the repeater is increased to improve signal transmission, then signal quality is improved, but residual echo increases causing oscillation
Solution Approach 1:
The patent implements an internal feedback path that feeds a portion of the output signal back to the input. This feedback mechanism allows the system to measure the residual echo and adjust the echo cancellation coefficients accordingly, enabling the repeater to operate at high gain levels while maintaining low residual echo through continuous adaptation
Solution Approach 2:
The patent dynamically adjusts echo cancellation coefficients based on the power spectrum analysis of the input signal. By changing these parameters adaptively rather than using fixed values, the system can minimize residual echo across varying signal conditions while maintaining high forward gain
2Object-generated harmful factors
If conventional echo cancellation methods are used, then some residual echo is acceptable, but minimizing residual echo is difficult for large repeater gains
Solution Approach 1:
The patent employs adaptive echo cancellation where the cancellation coefficients are continuously adjusted based on real-time power spectrum analysis. This dynamic approach allows the system to handle difficult cancellation conditions by adapting to changing signal characteristics, achieving -15 dB or lower residual echo even for large repeater gains
Solution Approach 2:
The patent performs preliminary filtering of the power spectrum to reduce autocorrelation width before computing echo cancellation coefficients. This preliminary processing step simplifies subsequent cancellation operations and enables effective echo minimization even under challenging conditions
Data Source
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AI summary
A wireless repeater (10) includes an input antenna (12) for receiving an input signal, an output antenna (13) for outputting an amplified signal, and an amplifier (29) for amplifying the received input signal and providing the output amplified signal to the output antenna (13). Radiated coupling between the input and output antennas causes echoes to be transmitted by the repeater. A filter (210) is used for applying a weighting function to a power spectrum of a measured signal in the wireless repeater thereby obtaining a weighted power spectrum of the measured signal. An internal feedback path (150) is employed for adaptively canceling the echo by implementing an adaptive algorithm based on a autocorrelation of the input signal employing the weighted power spectrum of the measured signal.