Tunable Full Duplex Architecture for RF Self-Interference Cancellation
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Solution Overview
Problem
Full Duplex (FD) systems face challenges in achieving high RF self-interference cancellation due to limitations in the tunability of existing architectures, particularly caused by insertion loss and mismatch issues in hybrid couplers, which restrict the range over which the cancellation signal can be effectively tuned.
Innovation Solution
The implementation of a tunable wideband FD architecture that uses a combiner with a variable impedance comprising a power splitter and variable phase shifting and attenuation circuitry, allowing for minimal insertion loss and reflection by ensuring the cancellation signal passes through the attenuator and phase shifter only once, and incorporating control circuitry to adapt the attenuation and phase delay for optimal self-interference minimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hybrid couplers are used in FD systems, then signal combining and splitting is achieved, but insertion loss and mismatch issues limit the tunability range of the cancellation signal
Solution Approach 1:
The patent extracts the cancellation signal generation function from the hybrid coupler path and creates a separate injection loop using a power splitter. This separation removes the cancellation signal from the path of insertion loss and mismatch limitations, allowing independent tuning without energy loss constraints.
Solution Approach 2:
The patent introduces a power splitter as an intermediary component to generate the cancellation signal independently. This mediator allows the cancellation signal to be created and tuned separately from the main signal path, avoiding the limitations of hybrid couplers while maintaining signal integrity.
2Adaptability or versatility
If hybrid couplers are used in FD systems, then signal combining is achieved, but mismatch issues restrict the effective tuning range
Solution Approach 1:
The patent extracts the cancellation signal generation from the hybrid coupler's signal path and places it in a separate injection loop. This extraction eliminates the mismatch problems inherent to hybrid couplers, allowing the cancellation signal to be tuned independently with high precision over a wide range.
Solution Approach 2:
The patent creates a copy of the transmitted signal through the power splitter to generate the cancellation signal. This copying approach allows precise control and tuning of the cancellation signal without the mismatch issues that would affect the original signal path through hybrid couplers.
3Adaptability or versatility
If cancellation signal passes through attenuator and phase shifter multiple times, then tuning flexibility increases, but insertion loss accumulates
Solution Approach 1:
The patent applies preliminary action by setting the optimal attenuation and phase shift values in advance through the control circuitry, before the cancellation signal is injected into the combiner. This single-pass approach through the attenuator and phase shifter eliminates accumulated loss while maintaining full tuning flexibility through digital control.
Solution Approach 2:
The patent implements feedback control where the control circuitry monitors the self-interference cancellation effectiveness and dynamically adjusts the attenuator and phase shifter settings. This feedback mechanism provides continuous optimization without requiring multiple passes through the tuning components, avoiding accumulated insertion loss.
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
This approach enables significant reduction in self-interference, achieving cancellation levels of up to −45 to −60 dB over the 2.45 GHz ISM band, with the potential for further improvements by tuning the cancellation signal, and is scalable for higher frequencies and powers, enhancing the performance of FD systems and MIMO configurations.
Implementation Method 1
The signal processing unit is configured to generate a cancellation signal... that cancels the self-interference signal
Data Source
AI summary
A full duplex system comprising a combiner with a first port connected to an antenna, a second port connectable to a source of a signal to be transmitted via the antenna, a third port for outputting a signal received via the antenna and a fourth port connected to a variable impedance. The variable impedance comprises a power splitter with an input connected to the fourth port and at least two outputs, wherein at least two outputs are connected to each other via variable phase shifting and attenuation circuitry.