Full-Duplex RF Circuit With Adaptive Self-Interference Cancellation
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Solution Overview
Problem
Full-time duplex systems face challenges in effectively canceling self-interference and preventing LNA distortion due to variable antenna phases and low isolation between transmitting and receiving antennas, particularly in mobile terminals and vehicle-mounted systems, leading to unstable operations and signal degradation.
Innovation Solution
A CCFD system and circuit with a mode determination unit that adjusts the amplitude and phase of the transmitting cancellation signal based on signal power ranges and RSSI, using power detection and RSSI amplitude phase adjustment units to cancel interference before the LNA, ensuring stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmitting signal power is increased to improve communication quality, then the self-interference cancellation becomes more difficult and LNA distortion occurs, but if the transmitting signal power is decreased, then the communication quality deteriorates
Solution Approach 1:
The patent applies preliminary action by adjusting the amplitude and phase of the transmitting cancellation signal before the self-interference reaches the LNA. The mode determination unit predicts potential interference levels and pre-adjusts the cancellation signal parameters to prevent LNA distortion before it occurs, rather than reacting after distortion has happened.
Solution Approach 2:
The patent implements feedback through the mode determination unit that continuously monitors the transmitting signal power and RSSI, then adjusts the amplitude phase adjustment unit accordingly. This closed-loop feedback mechanism ensures the cancellation signal adapts to changing transmission conditions to maintain optimal interference cancellation while preventing LNA distortion.
2Object-affected harmful factors
If the amplitude and phase of the transmitting cancellation signal are adjusted to cancel self-interference, then the self-interference is reduced, but the system complexity increases due to multiple adjustment units
Solution Approach 1:
The patent applies universality by designing the amplitude phase adjustment unit to serve multiple functions: it adjusts both amplitude and phase of the cancellation signal, and can operate in different modes (first and second adjustment modes) depending on transmission conditions. This multi-functionality reduces the need for separate dedicated components for each adjustment function.
Solution Approach 2:
The patent implements dynamics by making the cancellation signal parameters adjustable rather than fixed. The amplitude and phase can be dynamically changed based on real-time transmission conditions monitored by the mode determination unit, allowing the system to adapt to varying interference levels and transmission power without requiring multiple fixed hardware configurations.
3Power
If the LNA operates at high power levels to maintain signal strength, then the signal quality improves, but the LNA enters non-linear region causing distortion
Solution Approach 1:
The patent applies preliminary anti-action by pre-adjusting the amplitude and phase of the cancellation signal to counteract potential self-interference before it reaches the LNA. This prevents the LNA from receiving excessive interference signals that would push it into non-linear operation, thereby maintaining the LNA within its linear range while still allowing high signal power operation.
Data Source
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AI summary
Provided is a full-time duplex system. The system includes: a receiving antenna (107), a transmitting antenna (108), a transmitting channel (109), an LNA (106), a mode determination unit (101), a power detection amplitude phase adjustment unit (102), an RSSI detection amplitude phase adjustment unit (103) and an amplitude phase unit (104); the power detection amplitude phase adjustment unit (102) is electrically connected between the receiving antenna (107) and the low noise amplifier (106) and also between the transmitting antenna (108) and the transmitting channel (109); the mode determination unit (101) notifies, according to a power range which a signal transmitting power of the full-time duplex system belongs to, one of the power detection amplitude phase adjustment unit (102) or the RSSI detection amplitude phase adjustment unit (103) of controlling the amplitude phase unit (104) to adjust an amplitude and a phase of a transmitting cancellation signal.