Digital Pre-Distortion in Multi-Amplifier Transceivers
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Solution Overview
Problem
Power amplifiers in wireless and wireline communication systems operate near saturation, leading to nonlinear characteristics and distortion issues such as harmonic and intermodulation distortion, which are exacerbated by high peak-to-average-power modulation schemes like Orthogonal Frequency Division Multiplexing, posing challenges in system design.
Innovation Solution
A transceiver with multiple amplifiers and a combiner generates pre-distortion compensated transmit signals using pre-distortion compensation coefficients determined by processing the combined signal, effectively addressing nonlinearities through digital pre-distortion techniques, including a complex baseband digital pre-distortion method to adjust biases and iteratively update coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power amplifiers operate near saturation region to improve power efficiency, then power efficiency is improved, but nonlinear distortion increases
Solution Approach 1:
The system applies digital pre-distortion to the transmit signal before amplification. The pre-distortion processor modifies the signal characteristics in advance to counteract the expected nonlinear distortion that will occur when the power amplifier operates near saturation, thereby maintaining both high power efficiency and low distortion
Solution Approach 2:
The system uses a feedback loop where the output signal from the power amplifier is captured, converted to digital form, and compared with the original transmit signal. The error between these signals is used to continuously update and refine the pre-distortion coefficients, enabling the system to adapt to changing amplifier characteristics and maintain optimal performance
2Power
If multiple amplifiers are used to amplify transmit signals, then signal amplification capability is improved, but intermodulation distortion increases
Solution Approach 1:
The system combines the output signals from multiple power amplifiers using a combiner. By processing the combined signal through a single feedback path and using unified pre-distortion coefficients, the system manages the intermodulation distortion that arises from combining multiple amplified signals, maintaining both high power capability and signal quality
Solution Approach 2:
The pre-distortion processor and feedback system serve multiple functions simultaneously: they compensate for nonlinearities in individual amplifiers, manage intermodulation distortion from signal combining, and adapt to varying operating conditions. This multi-functional approach enables the system to handle complex multi-amplifier operations with a unified control mechanism
Data Source
AI summary
In an example embodiment, a transceiver includes a plurality of amplifiers configured to amplify an analog transmit signal to generate a plurality of amplified transmit signals for further transmission, a combiner configured to combine a plurality of output signals to generate a combined signal, the plurality of output signals being based on the plurality of amplified transmit signals and at least one processor configured to execute computer-readable instructions to cause the transceiver to determine pre-distortion compensation coefficients based on the combined signal and generate a pre-distortion compensated transmit signal based on the pre-distortion compensation coefficients.