Radio Transmitter PA Distortion Control With DPD and DPoD
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Solution Overview
Problem
Power amplifiers in radio transmitter devices face challenges in controlling non-linearity and distortion, particularly in 5G and 6G wireless networks, where strict emission requirements must be met.
Innovation Solution
The implementation of a radio transmitter device that applies a first distortion operation, such as digital pre-distortion (DPD), to control out-of-band distortion, and a second distortion operation, such as digital post-distortion (DPoD), for collaborative processing to control in-band distortion, using neural networks for partial application of these operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If digital pre-distortion is applied to control out-of-band distortion, then out-of-band distortion (ACLR) is reduced, but device complexity increases
Solution Approach 1:
Digital pre-distortion applies a distortion compensation operation before the power amplifier processes the signal. The transmitted signal is intentionally pre-distorted in the opposite direction of the expected power amplifier distortion, so that when the power amplifier applies its non-linear transformation, the overall effect is linear output. This preliminary action prevents out-of-band distortion before it occurs.
Solution Approach 2:
A digital signal processing block acts as an intermediary between the modulator and the power amplifier. This intermediary applies the pre-distortion transformation to the signal, modifying it in a controlled manner before it enters the non-linear power amplifier stage, thereby compensating for the upcoming distortion.
2Object-generated harmful factors
If digital post-distortion is applied to control in-band distortion, then in-band distortion (EVM) is reduced, but device complexity increases
Solution Approach 1:
Digital post-distortion uses feedback from the received signal to compensate for in-band distortion. The receiver measures the actual distortion that occurred during transmission and applies a corrective transformation to the received signal, using this feedback information to undo the power amplifier's non-linear effects and reduce in-band distortion such as EVM.
3Use of energy by moving object
If power amplifier operates at high efficiency, then power efficiency is improved, but distortion control becomes more difficult
Solution Approach 1:
By applying pre-distortion before the power amplifier, the signal is prepared in advance to compensate for the amplifier's non-linear behavior. This allows the power amplifier to operate at high efficiency points (such as saturation) without producing excessive out-of-band distortion, because the pre-distortion has already pre-compensated for the expected non-linear transformation.
Solution Approach 2:
Post-distortion techniques provide feedback-based correction that allows the system to tolerate higher power amplifier efficiency operation. The feedback loop measures the actual distortion produced and applies corrective transformations, enabling the power amplifier to operate more efficiently while maintaining acceptable distortion levels through active compensation.
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
Devices and methods for collaborative control of power amplifier related distortions in a radio transmitter device are disclosed. At least some example embodiments may allow controlling the distortions in the power amplifiers used in the radio transmitter devices in way that also takes into account various emission requirements.