RF Power Amplifier Predistortion for Stable MRI Signal Output
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Solution Overview
Problem
Radio frequency power amplifiers (RFPA) in magnetic resonance imaging (MRI) systems exhibit non-linear gain properties, leading to distortions that interfere with signal transmission and degrade image quality, posing risks to accurate diagnosis and research.
Innovation Solution
A gain compensation module and non-linear correction module are integrated with the RFPA to perform gain compensation and non-linear correction on the RF signal, using preset compensation rules and parameters such as supply voltage and transistor junction temperature to stabilize output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the RFPA operates in the saturation region or cutoff region to amplify RF pulses, then the amplification power is improved, but non-linear gain properties cause amplitude distortion and phase distortion that degrade signal quality
Solution Approach 1:
The patent applies pre-distortion technique where distortion compensation is performed in advance on the RF signal before amplification. The processing circuit pre-distorts the input signal based on predicted distortion characteristics, so that when the signal passes through the non-linear amplification region, the pre-applied distortion compensation counteracts the amplifier's non-linear effects, resulting in reduced amplitude and phase distortion in the final output.
2Stability of the object's composition
If gain compensation is performed using supply voltage and transistor junction temperature parameters, then output stability is improved, but device complexity increases due to additional processing circuits and sensors
Solution Approach 1:
The patent implements a feedback mechanism where the processing circuit continuously monitors the supply voltage and transistor junction temperature of the RFPA, and dynamically adjusts the RF signal parameters based on these measured values. This closed-loop control compensates for gain variations caused by temperature drift and voltage fluctuations, maintaining stable output characteristics despite changing operating conditions.
Solution Approach 2:
The system performs self-diagnosis and self-correction by automatically detecting its own operating parameters (supply voltage, temperature) and adjusting its output accordingly. The processing circuit uses the measured parameters to calculate and apply real-time gain compensation without external intervention, enabling the RFPA to maintain optimal performance autonomously.
3Manufacturing precision
If non-linear correction is applied to compensate for distortion, then image quality is improved, but processing time and computational resources increase
Solution Approach 1:
The patent performs distortion compensation in advance through pre-distortion of the RF signal before amplification. By predicting the non-linear distortion characteristics and applying compensatory distortion to the input signal beforehand, the system eliminates the need for time-consuming post-processing correction, achieving both high image quality and efficient real-time operation.
Data Source
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AI summary
Systems and methods for improving output stability of an RFPA. The systems may obtain an initial radio frequency signal to be amplified by the RFPA. The systems may also generate a compensated radio frequency signal by performing, based on a preset compensation rule and a set of compensation parameters, a gain compensation operation for the initial radio frequency signal. The set of compensation parameters may include a supply voltage of the RFPA and a transistor junction temperature of the RFPA. The systems may further generate, by performing a non-linear correction operation on the compensated radio frequency signal, a corrected radio frequency signal, which is transmitted to the RFPA.