Active Antenna Branch Compensation for Mutual Coupling Distortion
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Solution Overview
Problem
Active antenna systems face challenges with mutual coupling between antenna elements, leading to unwanted intermodulation and spurious emissions due to non-linear power amplifiers, which existing solutions fail to adequately address, especially in large arrays where complexity increases rapidly.
Innovation Solution
A method involving the determination and application of compensation coefficients to output signals from baseband processing units of antenna branches to compensate for mutual coupling, allowing pre-distortion techniques to mitigate non-linear effects while reducing computational complexity and maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If individual power amplifiers are used on each antenna branch in active antenna systems, then system integration and cable loss reduction are improved, but mutual coupling between antenna elements causes backwards intermodulation and spurious emissions
Solution Approach 1:
The patent applies digital pre-distortion techniques to pre-compensate the input signals before they reach the power amplifiers. By anticipating and correcting for the non-linear effects and mutual coupling in advance, the system prevents backwards intermodulation from occurring in the first place, rather than attempting to correct it after the fact
Solution Approach 2:
The patent introduces compensation coefficients as an intermediary element between the baseband processing unit and the power amplifiers. These coefficients act as a mediator that adjusts the signals to account for mutual coupling effects, allowing the individually linearized amplifiers to operate correctly despite the presence of coupling between antenna elements
2Object-generated harmful factors
If cross coupling compensation trees are used to counteract backwards intermodulation, then intermodulation suppression is improved, but device complexity increases rapidly with more antenna branches
Solution Approach 1:
The patent extracts and addresses only the dominant coupling effects between adjacent antenna elements rather than attempting to compensate for all possible coupling paths in the array. By focusing on the most significant intermodulation sources, the system achieves effective suppression without requiring complex compensation trees that would scale poorly with array size
Solution Approach 2:
The patent changes the approach from structural complexity to parameter optimization by using adjustable compensation coefficients that can be tuned to account for mutual coupling. This parameter-based approach allows flexible adaptation to different array configurations without increasing hardware complexity
3Reliability
If pre-distortion techniques are applied to linearize power amplifiers, then amplifier linearity is improved, but non-linear effects from mutual coupling still cause spurious emissions
Solution Approach 1:
The patent merges the pre-distortion function with mutual coupling compensation into a unified signal processing approach. By combining these two functions, the system simultaneously achieves amplifier linearization and coupling effect mitigation, preventing spurious emissions from both sources through a coordinated compensation strategy
Data Source
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AI summary
A method in a network node (1200) comprises receiving (1104) a first input from a baseband processing unit (210) of a first antenna branch (810A), receiving (1108) a second input from a baseband processing unit (210) of a second antenna branch (810B), determining (1112, 1116) a first and second compensation coefficient, applying (1120) the first compensation coefficient to the second input to generate a first output, applying (1124) the second compensation coefficient to the first input to generate a second output, outputting (1128) the first output to a first power amplifier (850A) of the first antenna branch, the first output compensating for a mutual coupling from the second antenna branch to the first antenna branch, and outputting (1132) the second output to a second power amplifier (850B) of the second antenna branch, the second output compensating for a mutual coupling from the first antenna branch to the second antenna branch.