Full-Duplex Transceiver Distortion Cancellation via Adaptive Filtering
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Solution Overview
Problem
Full-duplex transceivers face distortion issues due to transmitter signal leakage into the receiver channel, leading to data errors and reduced throughput, with existing solutions like SAW filters being impractical for small form factor devices.
Innovation Solution
The implementation of an adaptive filter that generates a digital signal based on the transmitted signal to simulate the filtering effects in the transceiver and subtract it from the received signal to cancel distortion, using techniques like least-means-squared filtering to reduce intermodulation distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SAW filters are used to reduce transmitter signal leakage, then receiver sensitivity is improved, but device form factor increases and becomes impractical for small devices
Solution Approach 1:
The patent replaces physical SAW (Surface Acoustic Wave) filters with a digital signal processing approach. Instead of using mechanical/acoustic filtering components that occupy physical space, the invention uses digital signal processing to generate an estimate of the transmitter signal leakage and subtract it from the received signal. This substitution of mechanical filtering with digital processing resolves the contradiction by maintaining receiver sensitivity while eliminating the need for bulky filter components in small devices.
Solution Approach 2:
The patent creates a digital copy or estimate of the transmitter signal leakage path by processing the transmitted signal through a model of the coupling path. This copied signal representation is then subtracted from the received signal to cancel the leakage. By copying and subtracting the interference signal rather than physically filtering it, the system achieves leakage reduction without requiring additional physical filtering components that would increase device form factor.
2Reliability
If transmitter signal leakage is reduced through physical filtering, then data errors are reduced, but device complexity and size increase
Solution Approach 1:
The patent replaces complex physical filtering systems with digital signal processing operations. Instead of implementing multiple stages of physical filtering components that increase device complexity, the invention uses digital algorithms to generate an estimate of the leakage signal and subtract it from the received signal. This digital approach reduces data errors while simplifying the overall device architecture by eliminating the need for complex physical filtering subsystems.
3Productivity
If adaptive filtering is applied to cancel distortion, then throughput is improved, but signal processing complexity increases
Solution Approach 1:
The patent implements an adaptive filtering system that uses feedback to continuously improve distortion cancellation. The system processes the transmitted signal through a model of the coupling path, subtracts the estimated leakage from the received signal, and uses the result to refine the filtering process. This feedback-based adaptive approach improves communication throughput by effectively removing distortion while managing processing complexity through iterative refinement rather than requiring overly complex upfront processing.
Data Source
AI summary
Methods and apparatus for canceling distortion in full-duplex transceivers are disclosed. Some example methods to reduce distortion in a full-duplex transceiver include generating a first digital signal, generating a first analog signal based on the first digital signal for transmission over a full-duplex channel, receiving a second analog signal via the full-duplex channel, and generating a second digital signal based on the second analog signal, wherein the second digital signal includes coupling distortion based on the first analog signal. The example methods further include generating an adaptive filter signal based on the first digital signal, and reducing the coupling distortion from the second digital signal by subtracting the adaptive filter signal from the second digital signal.