Spatial Digital Pre-Distortion for Shared MIMO PA Linearization
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Solution Overview
Problem
In multi-input multi-output (MIMO) systems with a large number of power amplifiers, existing digital pre-distortion techniques are not scalable and fail to contemporaneously linearize multiple power amplifier circuits due to variations in non-linearity characteristics, leading to inefficiencies and increased energy consumption with dedicated circuitry for each amplifier.
Innovation Solution
A hybrid approach using a commonly-shared digital pre-distortion signal applied to multiple power amplifier circuits with beam-forming weighting factors, collectively linearizing the output in the spatial domain by aggregating transmitted outputs from the antenna array, allowing adaptive compensation using a single spatially-aggregated feedback signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate pre-distortion circuits are used for each power amplifier, then linearity compensation is achieved, but device complexity and energy consumption increase
Solution Approach 1:
The patent merges multiple separate pre-distortion circuits into a single shared pre-distortion circuit that serves multiple power amplifiers. This is achieved by implementing collective linearization where one pre-distortion circuit processes signals for multiple amplifiers simultaneously, reducing the overall number of circuits while maintaining linearity compensation through spatial aggregation techniques.
Solution Approach 2:
The shared pre-distortion circuit is designed to perform multiple functions by compensating for non-linearity in multiple different power amplifiers. The circuit achieves universal applicability across different amplifier channels through beam-forming weighting factors and spatial aggregation, allowing a single circuit to provide linearity compensation for the entire array rather than requiring dedicated circuits for each amplifier.
2Reliability
If separate pre-distortion circuits are used for each power amplifier, then linearity compensation is achieved, but energy consumption increases
Solution Approach 1:
The patent merges multiple separate pre-distortion circuits into a single shared pre-distortion circuit that serves multiple power amplifiers. This is achieved by implementing collective linearization where one pre-distortion circuit processes signals for multiple amplifiers simultaneously, reducing the overall number of circuits while maintaining linearity compensation through spatial aggregation techniques.
Solution Approach 2:
The shared pre-distortion circuit is designed to perform multiple functions by compensating for non-linearity in multiple different power amplifiers. The circuit achieves universal applicability across different amplifier channels through beam-forming weighting factors and spatial aggregation, allowing a single circuit to provide linearity compensation for the entire array rather than requiring dedicated circuits for each amplifier.
3Device complexity
If a shared pre-distortion circuit is used for multiple power amplifiers, then device complexity is reduced, but difficulty in detecting and measuring non-linearity variations increases
Solution Approach 1:
The patent implements feedback mechanisms where the output of the power amplifiers is monitored and fed back to the shared pre-distortion circuit. This feedback loop enables the system to detect non-linearity variations in real-time and adjust the pre-distortion parameters accordingly. The feedback signal contains information about the actual output characteristics, allowing the shared circuit to adapt to variations in different amplifier channels despite using a single pre-distortion path.
Solution Approach 2:
The patent introduces beam-forming weighting factors and spatial aggregation techniques as intermediary elements between the shared pre-distortion circuit and the multiple power amplifiers. These intermediaries facilitate the measurement and detection of non-linearity variations by transforming the complex multi-channel problem into a manageable form that the shared circuit can handle, effectively mediating between the single circuit and multiple amplifiers with different characteristics.
Data Source
AI summary
Power amplifier circuits can behave in a non-linear manner particularly when operated to produce output signal swings approaching an amplifier saturation region. A pre-distortion signal can be applied to a signal to be transmitted to compensate for such power amplifier non-linearity. In applications where two or more transmitter power amplifiers are used, a beam-former can be configured to modify a digitally pre-distorted transmission signal by applying respective beam-forming weighting factors to the digitally pre-distorted transmission signal to provide input transmission signals for respective ones of the power amplifier circuits. The pre-distortion signal can be established at least in part using one or more of a sensed or estimated representation of a transmitted beam formed by spatially aggregating transmitted outputs from the two or more power amplifier circuits. In this manner, power amplifier efficiency can be enhanced without entirely separate pre-distortion compensation for each of the power amplifier circuits.