RF Power Amplifier Feedforward Linearization for Wideband Distortion
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Solution Overview
Problem
RF power amplifiers, particularly those using EER topologies, suffer from poor linearity due to non-linearities in pulse-width modulator circuits and switching circuits, leading to signal distortion and spectral re-growth, which affects bit-error rate performance and requires inefficient high-power amplifiers for feedforward linearization, limiting its practicality, especially for wideband signals.
Innovation Solution
A digital multiplexer generates two instances of digital data, with one instance converted to analog magnitude and phase signals for an RF amplifier and the other to an analog RF reference signal, using a feedforward linearization circuit with a differential amplifier and combiner to generate and align error signals for correcting distortion in the RF output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If feedforward linearization is applied to highly non-linear EER amplifiers, then linearity is improved, but a relatively high power RF amplifier is required for scaling the error signal, which reduces overall efficiency
Solution Approach 1:
The patent changes the operating parameters of the error signal amplifier by using compression techniques to reduce the magnitude of the error signal before amplification. This allows the use of a lower power amplifier while still achieving the required linearity correction, thereby resolving the contradiction between improving linearity and maintaining efficiency.
2Device complexity
If traditional RF components are used in feedforward linearization, then the system is simpler, but phase and amplitude variations occur across wideband signals, reducing accuracy
Solution Approach 1:
The patent replaces traditional RF mechanical/components-based signal processing with digital signal processing. By converting RF signals to digital domain for processing and then back to analog, the system achieves phase and amplitude accuracy across wideband signals while maintaining manageable complexity through software-based solutions.
3Manufacturing precision
If the error signal magnitude is increased to improve linearity, then distortion removal is enhanced, but the power consumption of the error signal amplifier increases
Solution Approach 1:
The patent introduces asymmetry in the signal processing by applying compression specifically to the error signal path. This asymmetric treatment reduces the peak magnitude of the error signal without affecting the overall linearity correction capability, thereby reducing power consumption in the error signal amplifier while maintaining distortion removal accuracy.
Data Source
AI summary
RF amplifier system (200) incorporating feedforward linearization. The system includes a digital waveform source (202) generating digital data s(t) representative of at least one analog signal. The system also includes a feedforward linearization circuit for reducing a distortion of an RF power amplifier (212). The feedforward linearization circuit includes a differential amplifier (230) arranged for generating an error signal. The error signal is determined based on a difference between the distorted RF output signal and an analog RF reference signal (229) generated from the digital data.