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 adequately compensate for non-linearity across multiple power amplifier circuits, leading to inefficiencies and increased energy and cost due to the need for dedicated circuitry for each amplifier.
Innovation Solution
A hybrid approach is implemented where a commonly-shared digitally pre-distorted transmission signal is applied to multiple power amplifier circuits with beam-forming weighting factors, using a single digital pre-distortion circuit and digital-to-analog converter, and adaptive feedback or estimation to collectively linearize the outputs in the spatial domain, even for poorly-matched amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate pre-distortion compensation is applied to each power amplifier circuit, then non-linearity compensation accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple separate pre-distortion compensation circuits into a single shared pre-distortion circuit that serves multiple power amplifier circuits. This is achieved by spatially aggregating feedback signals from multiple PAs and applying a common pre-distortion signal, thereby reducing device complexity while maintaining compensation effectiveness through adaptive feedback mechanisms.
Solution Approach 2:
The pre-distortion circuit is designed with multi-functionality to serve multiple power amplifier circuits simultaneously. By using a single pre-distortion circuit that processes aggregated feedback from multiple PAs and applies compensation to all, the system achieves universal compensation capability, reducing the need for dedicated circuitry for each amplifier.
2Reliability
If dedicated pre-distortion circuitry is provided for each power amplifier, then compensation effectiveness is improved, but energy consumption and cost increase
Solution Approach 1:
The patent combines multiple dedicated pre-distortion circuits into a single shared circuit that serves multiple power amplifiers. Energy consumption is reduced by eliminating redundant circuitry while maintaining compensation effectiveness through spatial aggregation of feedback signals and adaptive processing that accounts for individual PA characteristics within the collective system.
Solution Approach 2:
The pre-distortion circuit achieves multi-functionality by compensating for non-linearity in multiple power amplifier circuits simultaneously. This universal approach reduces energy consumption by avoiding the need for separate dedicated circuits for each PA, while maintaining compensation effectiveness through adaptive feedback that captures the collective behavior of the PA array.
3Device complexity
If a commonly-shared pre-distortion signal is used for multiple power amplifiers, then device complexity is reduced, but non-linearity compensation accuracy deteriorates
Solution Approach 1:
The patent implements adaptive feedback mechanisms where feedback signals from multiple power amplifier outputs are spatially aggregated and fed back to the pre-distortion circuit. This feedback loop enables the system to continuously adjust and optimize the pre-distortion signal, maintaining high compensation accuracy despite using a shared circuit, by accounting for individual PA characteristics through the aggregated feedback.
4Manufacturing precision
If separate pre-distortion circuits are used for each power amplifier, then non-linearity compensation is improved, but the system becomes less scalable
Solution Approach 1:
The pre-distortion circuit is designed with universal multi-functionality to serve any number of power amplifier circuits in the array. This scalable architecture allows the same circuit design to be applied whether there are a few or many PAs, achieving both effective non-linearity compensation and system scalability through its ability to handle multiple outputs simultaneously.
Solution Approach 2:
The patent transitions from individual per-PA pre-distortion circuits to a collective spatial-domain approach. By aggregating feedback signals in the spatial domain and applying a common pre-distortion signal, the system moves to a higher-dimensional solution that can efficiently handle any number of PAs, thereby achieving scalability while maintaining compensation accuracy.
Data Source
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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.