Digital Pre-Distortion Input Limiting for PA Saturation Stability
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Solution Overview
Problem
Conventional digital pre-distortion systems experience instability and performance degradation due to saturation phenomena in power amplifiers when input levels exceed a certain threshold, leading to increased average output power and divergence, which negatively impacts the stability and performance of secure transmission systems.
Innovation Solution
A digital pre-distortion method and apparatus that incorporates a Saturation Level Limiter (SLL) to detect peak levels in power amplifiers and limit input signals to prevent saturation, using a Peak Level Detector (PLD) and SLL to set a threshold value based on gain reduction, thereby preventing excessive input and maintaining system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If digital pre-distortion is applied to linearize power amplifier output, then linearity of output signal is improved, but saturation occurs when input levels exceed threshold causing instability and performance degradation
Solution Approach 1:
The patent applies preliminary anti-action by introducing a saturation level limiter that proactively prevents the power amplifier input from reaching saturation levels. The limiter detects when the input signal approaches the saturation threshold and attenuates it accordingly, preventing the harmful saturation effect before it occurs. This resolves the contradiction by maintaining linearity through prevention rather than correction, ensuring system stability while preserving the linearization benefit.
Solution Approach 2:
The patent implements feedback by using a peak level detector to monitor the power amplifier input signal and a saturation level limiter that adjusts attenuation based on detected peak levels. The system continuously measures the input signal characteristics and dynamically adjusts the attenuation factor to prevent saturation. This feedback mechanism ensures that linearity is maintained while preventing instability, resolving the contradiction between improving linearity and maintaining system reliability.
2Power
If input signal level is increased to improve transmission performance, then output power is improved, but saturation phenomenon increases causing divergence
Solution Approach 1:
The patent applies dynamics by making the attenuation factor adaptive rather than fixed. The saturation level limiter dynamically adjusts the attenuation based on real-time detection of peak signal levels. When input levels are high, attenuation increases to prevent saturation; when input levels are low, attenuation decreases to preserve output power. This dynamic adjustment resolves the contradiction by allowing high output power when safe and preventing saturation when necessary, maintaining system stability.
Solution Approach 2:
The patent changes the parameter of attenuation dynamically based on detected signal characteristics. The system monitors peak levels and adjusts the attenuation factor accordingly, transforming a static parameter into a dynamic one. This parameter change enables the system to achieve high output power when the amplifier is operating in its linear region while preventing saturation when input levels would cause instability, thus resolving the contradiction between power and stability.
3Reliability
If saturation level limiter is added to prevent saturation, then system stability is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the saturation level limiter to perform multiple functions within a single integrated structure. The limiter not only prevents saturation but also measures peak levels, calculates appropriate attenuation factors, and adjusts the input signal accordingly. By combining these functions into one component, the patent reduces the overall device complexity compared to having separate components for each function, thus resolving the contradiction between improving stability and minimizing complexity.
Data Source
AI summary
A digital pre-distortion system and method are provided. The method includes performing a digital pre-distortion operation; and limiting an input of the power amplifier to be no greater than a limit threshold.