Cancellation Circuit for Full-Duplex Self-Interference Reduction
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Solution Overview
Problem
Full-duplex wireless communication systems face significant challenges in reducing self-interference when operating at the same frequency for both transmission and reception, rendering them ineffective in receiving desired signals.
Innovation Solution
A cancellation circuit with multiple delay and attenuation paths, a combiner, and a subtractor is used to construct and subtract a signal representative of the self-interference, employing variable attenuators and sinc functions to optimize interference cancellation, along with a splitter, balun, isolator, and processing engine to enhance signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full-duplex communication operates at the same frequency for both transmission and reception, then spectral efficiency is improved, but self-interference increases significantly
Solution Approach 1:
The patent segments the self-interference cancellation into multiple delay paths (N paths where N≥2), with each path processing a different time segment of the transmit signal. This segmentation allows the system to handle the interference across multiple time windows, effectively reducing the overall self-interference while maintaining full-duplex operation at the same frequency.
Solution Approach 2:
The patent applies preliminary action by pre-processing the transmit signal through multiple delay and attenuation paths before it combines with the received signal. The controller adjusts attenuation levels in advance based on estimated self-interference characteristics, allowing the cancellation circuit to proactively reduce interference before it corrupts the desired receive signal.
2Object-generated harmful factors
If multiple delay and attenuation paths are used to reduce self-interference, then interference cancellation performance is improved, but device complexity increases
Solution Approach 1:
The patent implements universality by designing the cancellation circuit with N reusable delay and attenuation paths that can handle multiple interference scenarios. The same architectural block (delay element + variable attenuator) is replicated N times, allowing the system to reduce complexity by using identical modular units rather than designing separate complex circuits for each path.
Solution Approach 2:
The patent applies dynamics through the controller that dynamically adjusts the attenuation levels of the N variable attenuators based on real-time estimates of self-interference characteristics. This dynamic adaptation allows the system to optimize interference cancellation for different channel conditions and transmit signal patterns, improving performance without requiring a fixed complex structure.
3Measurement precision
If attenuation levels are dynamically adjusted based on self-interference estimates, then interference cancellation accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent implements feedback by using the controller to continuously monitor and estimate self-interference characteristics, then adjusting the attenuation levels of the N variable attenuators based on these estimates. This closed-loop feedback mechanism allows the system to adapt to changing interference conditions and maintain high cancellation accuracy without requiring overly complex processing.
Solution Approach 2:
The patent applies copying by creating N copies of the delayed and attenuated transmit signal paths, where each copy represents an estimate of the self-interference at different time delays. These copied signals are then combined and subtracted from the received signal, allowing the system to accurately model and cancel interference without requiring complex real-time processing of the actual interference waveform.
Data Source
AI summary
A wireless communication device includes, in part, at least one antenna for receiving or transmitting a signal, and a cancelation circuit adapted to cancel or reduce the self-interference signal. The cancelation circuit includes, in part, a control block, N delay and attenuation paths, a combiner, and a subtractor. Each path includes a delay element and a variable attenuator whose attenuation level varies in response to a control signal generated by the control block. Each path receives a sample of the transmit signal and generates a delayed and attenuated (weighted) version of the sample signal. The combiner combines the N delayed and weighted versions of the sample signal to construct a signal representative of the self-interference signal. The subtractor subtracts the constructed signal from the received signal thereby the cancel or reduce the self-interference signal therefrom.