Cascaded Digital Pre-Distortion for High-Power PA Linearity
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Solution Overview
Problem
Wireless communication systems face challenges such as signal attenuation and distortion due to non-linear power amplifiers, leading to inefficiencies and interference, particularly in high-power applications like 5G new radio networks, which affect data throughput and emissions compliance.
Innovation Solution
The implementation of digital pre-distortion (DPD) and digital post-distortion (DPoD) techniques to mitigate distortion by applying inverse distortion to signals before transmission and after reception, respectively, using frequency-selective methods to address both in-band and out-of-band distortions, and dynamic adjustment based on power amplifier models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power amplifiers operate at high power to maximize transmission capability, then data throughput is improved, but signal distortion and out-of-band emissions increase
Solution Approach 1:
The patent applies digital pre-distortion (DPD) to the transmitted signal before it enters the power amplifier. The DPD circuit calculates distortion compensation values based on the PA model and applies inverse distortion to counteract the expected non-linear effects of the PA, thereby preventing signal distortion and reducing out-of-band emissions while allowing the PA to operate at high power levels
Solution Approach 2:
The patent uses the known characteristics of PA distortion (a harmful effect) to create a beneficial compensation mechanism. By modeling the PA's non-linear behavior and applying pre-distortion based on this model, the system converts the predictable harmful distortion into a compensable parameter, turning the PA's non-linearity from a problem into a manageable characteristic that can be corrected
2Stability of the object's composition
If digital pre-distortion is applied to mitigate signal distortion, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent performs distortion compensation in advance before the signal enters the power amplifier. The DPD circuit pre-calculates and applies distortion correction values based on the PA model, eliminating the need for complex real-time correction circuits after amplification. This preliminary action simplifies the overall system architecture by handling distortion correction proactively rather than reactively
Solution Approach 2:
The patent introduces a DPD circuit as an intermediary component between the signal source and the power amplifier. This intermediary applies mathematical transformation (pre-distortion) to the signal, converting it into a form that the non-linear PA can process more linearly. The DPD acts as a buffer that absorbs the complexity of distortion compensation, protecting the rest of the system from dealing with non-linear effects
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for digital pre-distortion (DPD). An apparatus for wireless communication generally includes a power amplifier (PA); a first DPD circuit, a second DPD circuit, and a transmitter. The first DPD circuit is generally configured to: obtain an input signal; apply a first DPD to the input signal to generate a first resulting signal; and output the first resulting signal to the second DPD circuit. The second DPD circuit is generally configured to: obtain the first resulting signal from the first DPD circuit; apply a second DPD to the first resulting signal to generate a second resulting signal; and output the second resulting signal to the PA. The PA is generally configured to amplify the second resulting signal to generate an amplified second resulting signal. The transmitter is generally configured to transmit the amplified second resulting signal to a second apparatus.