Full-Duplex Interference Cancellation via Dynamic Equivalent Load
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Solution Overview
Problem
In wireless full-duplex communication systems, achieving effective interference cancellation is challenging due to large antenna impedance mismatch, which affects the isolation between transmit and receive signals, making it difficult to cancel self-interference signals effectively.
Innovation Solution
The proposed solution involves an apparatus and method using a splitter, circulators, an equivalent load, and a combiner to split and process radio-frequency signals, generating a reference signal that corresponds to the self-interference signal, allowing for phase inversion and amplitude regulation to cancel the self-interference component in the receive signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an antenna is used for both transmitting and receiving signals, then antenna utilization is improved, but self-interference occurs due to the strong transmit signal overwhelming the weak receive signal
Solution Approach 1:
The transmit signal path and receive signal path are segmented into separate circuits using circulators. The circulator divides the antenna system into distinct transmit and receive paths, allowing the same antenna to be used for both functions while preventing self-interference through circuit-level separation.
Solution Approach 2:
A circulator is introduced as an intermediary device between the antenna and the transmit/receive circuits. This passive component mediates the signal flow, directing transmit signals to the antenna and receive signals from the antenna while providing isolation to prevent self-interference.
2Object-generated harmful factors
If a circulator is used to isolate transmit and receive ends, then self-interference is reduced, but impedance mismatch occurs when antenna VSWR varies with frequency
Solution Approach 1:
The system changes the impedance parameter dynamically by switching between different equivalent loads (50 ohm and 200 ohm) based on frequency bands. This allows the load impedance to adapt to the antenna's varying VSWR characteristics across different frequency ranges, maintaining effective interference cancellation despite impedance variations.
Solution Approach 2:
The equivalent load is made dynamic rather than fixed, allowing it to be switched between different impedance values (50 ohm for lower bands, 200 ohm for higher bands) to match the antenna's frequency-dependent characteristics. This dynamic adaptation maintains system reliability across varying operating conditions.
3Object-generated harmful factors
If different frequency divisions are used for transmitting and receiving, then self-interference is avoided, but spectrum efficiency is reduced compared to full-duplex operation
Solution Approach 1:
A circulator serves as a mediator that enables full-duplex operation by providing isolation between transmit and receive paths. This allows simultaneous transmitting and receiving on the same frequency, achieving high spectrum efficiency while the interference cancellation system handles any remaining self-interference.
Solution Approach 2:
The system creates a copy of the transmit signal through the equivalent load to generate a reference signal for interference cancellation. This reference signal is then used to cancel self-interference in the receive path, enabling effective full-duplex operation with high spectrum efficiency.
4Device complexity
If a fixed equivalent load is used for interference cancellation, then the circuit is simple, but cancellation effectiveness deteriorates when antenna impedance varies with frequency
Solution Approach 1:
The equivalent load is made dynamically switchable between different impedance values (50 ohm and 200 ohm) based on the operating frequency band. This maintains simple circuit topology while improving cancellation effectiveness by adapting the load impedance to match the antenna's frequency-dependent characteristics.
Solution Approach 2:
The load impedance parameter is changed based on frequency bands - using 50 ohm for lower bands and 200 ohm for higher bands. This parameter adaptation maintains high interference cancellation effectiveness across different operating frequencies without significantly increasing circuit complexity.
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 improves the effectiveness of interference cancellation by using an equivalent load to generate a reference signal that matches the self-interference signal, enabling better isolation and reducing interference, thus enhancing the overall performance of wireless full-duplex systems.
Implementation Method 1
a first circulator (120) is configured to transmit the first transmit signal through the second port (124) to the antenna (130)
Implementation Method 2
the antenna (130) is configured to transmit the first transmit signal, perform receiving processing to acquire a receive signal
Implementation Method 3
acquire, through the third port (146), a reference signal generated due to that the equivalent load (150) reflects the second transmit signal
Implementation Method 4
the combiner (160) is configured to cancel the self-interference signal component in the to-be-processed signal according to the reference signal
Data Source
AI summary
Embodiments of the present invention provide an apparatus and a method for interference cancellation. The apparatus includes: a splitter, configured to acquire a first transmit signal and a second transmit signal; a first circulator, configured to transmit the first transmit signal to an antenna and to send a to-be-processed signal to a combiner, where the to-be-processed signal includes a receive signal component and a self-interference signal component, the self-interference signal component corresponds to an interference signal generated due to that the antenna reflects the first transmit signal; a second circulator, configured to: transmit the second transmit signal to an equivalent load, and acquire a reference signal generated due to that the equivalent load reflects the second transmit signal, where an impedance of the equivalent load corresponds to an impedance of the antenna; and a combiner, configured to cancel the self-interference signal component according to the reference signal.