Photonic-Enabled RF Cancellation for Wideband Self-Interference
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Solution Overview
Problem
Conventional RF cancellers face limitations in bandwidth and flexibility due to their reliance on all-electronic components, with modest tap counts and restricted operational bandwidths, which hampers their effectiveness in mitigating self-interference in In-Band Full-Duplex (IBFD) applications.
Innovation Solution
A photonic-enabled RF canceller with a vector modulator architecture that maps self-interference to an optical wavelength, allowing for amplitude modulation and time-delay manipulation in the optical domain, enabling wideband cancellation and scalability beyond traditional tap counts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If all-electronic RF canceller components are used, then device complexity is reduced, but operational bandwidth and flexibility are limited
Solution Approach 1:
The patent introduces photonic components as intermediaries between the RF domain and the cancellation process. Optical carriers modulated by RF signals enable wideband cancellation without directly complicating the RF electronics, as the photonic domain handles the bandwidth-intensive operations
Solution Approach 2:
The patent replaces all-electronic RF cancellation mechanisms with a hybrid photonic-electronic system. The photonic components (lasers, modulators, photodetectors) substitute for electronic components to achieve wideband operation, leveraging the superior bandwidth characteristics of optical systems
2Reliability
If more canceller taps are added to address multipath reflections, then cancellation performance improves, but device complexity and optical component requirements increase
Solution Approach 1:
The patent segments the cancellation function into multiple independent taps, each handling specific multipath components. The optical domain enables parallel processing of multiple taps without the complexity constraints of all-electronic implementations, allowing flexible configuration to match multipath environments
Solution Approach 2:
The photonic canceller architecture provides universal functionality for handling various multipath scenarios through configurable taps. The same optical infrastructure supports different numbers and configurations of taps to address diverse propagation environments
3Adaptability or versatility
If microwave photonic cancellers operate in the optical domain, then instantaneous bandwidth increases, but canceller tap count is restricted by optical couplers and combiners
Solution Approach 1:
The patent transitions from RF-domain to optical-domain operations, adding a dimensional change that enables wideband cancellation. The optical domain provides additional degrees of freedom in terms of bandwidth and tap configuration, overcoming the limitations of RF components while managing complexity through photonic integration
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
The photonic-enabled RF canceller achieves significant self-interference cancellation over wide instantaneous and tuning bandwidths, with demonstrated performance of 25 dB over 500 MHz and 20 dB over 1 GHz, and is tunable between 0.5 and 5.5 GHz, enhancing spectral and networking efficiency in IBFD systems.
Implementation Method 1
The mitigated optical signals are converted back to the RF domain using one or more photodetectors
Data Source
AI summary
In-band full-duplex (IBFD) wireless systems offer the ability to revolutionize frequency spectrum utilization for future networks. For IBFD systems to work, the self-interference (SI) generated by each wireless node should be sufficiently mitigated, which becomes more challenging as the bandwidth increases. RF cancellation enables this interference reduction but has been limited so far to narrowband operation or restricted to distinctive environments. Fortunately, a photonic-enabled RF canceller can provide broadband interference cancellation using photonic components in a wideband vector modulator architecture with tunable time-delay taps. An example of this canceller with 20 canceller taps provides 25 and 20 dB of cancellation over 500-MHz and 1-GHz instantaneous bandwidths, respectively, and is tunable between 0.5 and 5.5 GHz. This photonic-enabled RF canceller provides the wideband operation and high tap counts for successfully deploying future wireless systems with IBFD technology.