Introduction to adaptive predistorter
An adaptive predistorter is a signal processing technique used to compensate for nonlinear distortions in high peak-to-average ratio (PAR) signals. In wireless communication and broadcast systems, PAR refers to the difference between the maximum and average power levels of a signal. Signals with high PAR can cause significant distortions when amplified, leading to reduced system performance.
Adaptive predistortion techniques aim to mitigate these distortions by dynamically adjusting the input signal based on the characteristics of the amplifier and its nonlinearities. This process involves modelling the amplifier's behaviour and applying an inverse distortion function to the input signal before it is amplified.
By using feedback mechanisms and adaptive algorithms, an adaptive predistorter continuously adapts its parameters to changes in the amplifier's characteristics, ensuring optimal compensation for nonlinearities in real-time.
High peak-to-average ratio (PAR) in signals
The peak-to-average ratio (PAR) is a measure of the maximum amplitude compared to the average amplitude of a signal. In signals with high PAR, there are significant peaks or spikes that occur sporadically, causing the average amplitude to be much lower than the maximum amplitude. This phenomenon can be observed in various types of signals, including audio, video, and wireless communication signals.
High PAR signals often result from nonlinearities in the signal generation or transmission process. Nonlinearities can introduce distortions that cause certain portions of the signal to have higher amplitudes than others.
The presence of high PAR in signals can pose several challenges in practical applications. It can lead to inefficient use of power amplifiers, as they need to be designed to handle the highest possible amplitudes. This results in increased power consumption and reduced overall system performance. Additionally, high PAR can cause intermodulation distortion and spectral regrowth, which degrade the quality of the transmitted signal.
To address these challenges and optimize signal transmission, an adaptive predistorter is often employed. This predistorter adjusts the input signal before it is transmitted through a power amplifier to compensate for the nonlinearities and reduce the PAR. By purposely distorting the input signal in a controlled manner, it ensures that when passed through the power amplifier and subsequent stages, the output signal has a lower PAR.
The adaptive predistorter works by modelling and compensating for the nonlinear characteristics of the system. It uses advanced algorithms and digital signal processing techniques to analyze and modify the input signal based on its known nonlinear behaviour. The goal is to shape the input signal so that it will undergo specific transformations when passing through the power amplifier, resulting in a more linear and lower PAR output signal.
By reducing the PAR of the signal, the adaptive predistorter enables more efficient use of power amplifiers. This leads to improved power efficiency, reduced distortion, and enhanced overall system performance.
Avateq's adaptive predistorter effectively compensates non-linear and linear distortions caused by imperfections of the signal distribution and amplification components.
It's benefits include:
- Reduced distortion
- Improved signal quality
- Increased power efficiency
- Enhanced spectral efficiency
- Flexibility in system design
- Compatibility with existing systems
- Cost savings