Full-Duplex Radio Self-Interference Cancellation via Digital Feedback
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Solution Overview
Problem
Full-duplex radios face performance limitations due to self-interference signals, which are challenging to cancel effectively due to the unknown nature of the transmitted analog signal and distortions introduced by analog components, leading to inadequate cancellation techniques that are difficult to implement.
Innovation Solution
A feedback receiver circuit taps the analog TX signal to convert it into a digital representation, allowing for digital cancellation of self-interference noise components, and a compensating transmitter circuit can cancel noise in the analog domain, reducing the dynamic range requirements of ADCs and improving cancellation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital cancellation techniques are used to cancel self-interference, then cancellation effectiveness is improved, but implementation complexity increases due to the unknown nature of the transmitted analog signal and distortions introduced by analog components
Solution Approach 1:
The patent introduces an intermediary model of the transmitted signal that passes through the analog transmit chain to represent the actual transmitted analog signal. This model serves as a mediator between the digital baseband signal and the self-interference cancellation process, allowing accurate representation of signal distortions without requiring direct measurement of the unknown analog signal.
Solution Approach 2:
The patent performs preliminary modeling of the transmitted signal through the analog transmit chain before cancellation is needed. By pre-characterizing the distortions introduced by analog components (power amplifier, mixer, filter) and storing this information in a lookup table, the system prepares cancellation data in advance, reducing real-time computational complexity.
2Ease of manufacture
If analog cancellation circuits are used to cancel self-interference, then implementation simplicity is improved, but cancellation effectiveness deteriorates due to the unknown nature of the transmitted analog signal
Solution Approach 1:
The patent creates a digital copy of the transmitted signal by modeling it through the analog transmit chain characteristics. This digital copy accurately represents the actual transmitted analog signal including all distortions, enabling precise cancellation without requiring complex analog circuitry to generate and compare signals in real-time.
3Measurement precision
If high dynamic range ADCs are used to capture the full analog signal, then signal capture accuracy is improved, but hardware complexity and cost increase
Solution Approach 1:
The patent extracts only the necessary signal information for cancellation by using a simplified model of the transmitted signal rather than capturing the full high-dynamic-range analog signal. By taking out only the essential characteristics needed for self-interference cancellation, the system avoids the need for complex high dynamic range ADCs while maintaining cancellation effectiveness.
Data Source
AI summary
A full-duplex radio device is disclosed. The full-duplex radio device includes an analog transmission (TX) circuit that includes a power amplifier to output an analog TX signal. The full-duplex radio device also includes a feedback receiver circuit coupled to the analog TX circuit. The feedback receiver circuit provides a digital representation of the analog TX signal that is used to digitally cancel at least a transmitter noise component of a self-interference signal associated with a transmission of the analog TX signal in the full-duplex radio device.