eNodeB Amplifier Bias Control for PAR-Adaptive Linearity
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Solution Overview
Problem
Current amplification systems, such as those in eNodeB base stations, face inefficiencies over a wide power range, particularly in LTE networks, leading to high energy consumption and greenhouse gas emissions, while maintaining linearity performance as per 3GPP standards, and existing architectures like Doherty, Envelop Tracking, and switch mode systems have limitations in dynamic range, complexity, and bandwidth.
Innovation Solution
An amplification system incorporating a crest factor reduction module, digital pre-distortion module, drain bias controller, and gate bias controller that dynamically adapt to the Peak Average Ratio of the input signal, optimizing power amplifier efficiency and linearity across the full dynamic range without increasing complexity or reducing linearity, by synchronizing parameters like clipping radius, drain bias voltage, and gate bias voltage based on load and modulation factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Doherty power amplifier architecture is used to optimize efficiency at full power, then efficiency is improved, but efficiency deteriorates over wider dynamic range
Solution Approach 1:
The patent implements dynamic adaptation of the clipping radius based on the instantaneous Peak Average Ratio (PAR) of the input signal. The CFR module continuously adjusts the clipping threshold according to signal statistics, enabling the system to maintain optimal efficiency across varying power levels and dynamic conditions, rather than being fixed for full power operation only.
Solution Approach 2:
The system dynamically changes the clipping radius parameter based on signal PAR and load conditions. By adjusting this parameter in real-time, the amplifier adapts its operating point to maintain high efficiency across the full dynamic range, resolving the contradiction between full power optimization and wide dynamic range performance.
2Loss of energy
If clipping is applied to reduce Peak Average Ratio, then efficiency is improved, but linearity deteriorates
Solution Approach 1:
The system applies pre-distortion to the signal before amplification. The DPD module pre-compensates for the non-linearities introduced by the power amplifier and clipping operations, so that the final output maintains linearity despite the aggressive clipping used to improve efficiency.
Solution Approach 2:
The system employs feedback mechanisms where the output signal is monitored and used to adjust the pre-distortion parameters. This closed-loop approach ensures that linearity is maintained by continuously compensating for any distortion introduced by the efficiency-optimizing clipping operations.
3Loss of energy
If dynamic adaptation of clipping radius is implemented, then efficiency over full dynamic range is improved, but system complexity increases
Solution Approach 1:
The CFR module autonomously adapts the clipping radius based on the statistical properties of the input signal itself. The system uses the signal's own PAR measurements to control the clipping threshold, eliminating the need for external complex control mechanisms while achieving dynamic range optimization.
4Manufacturing precision
If pre-distortion is applied to maintain linearity, then linearity is preserved, but computational complexity increases
Solution Approach 1:
The pre-distortion is applied in advance before the signal reaches the power amplifier. By pre-compensating for expected non-linearities based on the clipped signal characteristics, the system maintains linearity without requiring complex real-time correction during amplification, reducing overall computational burden.
Data Source
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Figure 5a~5b
AI summary
Amplification system and associated eNodeB. The amplification system comprises a crest factor reduction module configured to clip the input signal and a digital pre-distortion module configured to pre-distort the clipped signal and at least one power amplifier configured to amplify the pre-distorted signal. Furthermore, within this amplification system, the crest factor reduction module is configured to pass an information representing a Peak Average Ratio of the input signal to the digital pre-distortion module and to the power amplifier, and the crest factor reduction module is configured to dynamically adapt a clipping radius according to a load factor and/or a modulation of the input signal and the digital pre-distortion module being configured to pre distort the clipped signal based on the information. This amplification system also comprises a drain bias controller, providing a drain bias voltage, based on the information, to the power amplifier; and a gate bias controller, providing a gate bias voltage, based on the information, to the power amplifier.