RF Power Amplifier Harmonic Feedback for IM3 Distortion Reduction
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Solution Overview
Problem
RF power amplifiers face challenges in maintaining linearity and reducing distortion, particularly when the interval between fundamental frequency components of different bands is narrow, leading to issues with third-order intermodulation distortion and second harmonic components.
Innovation Solution
A power amplifying device is designed with a first amplification circuit, a filter circuit, and an inverting circuit. The filter circuit uses inductor and capacitor elements to generate low impedance for fundamental frequency components and high impedance for second harmonic components, while the inverting circuit phase-inverts and attenuates second harmonic and third-order intermodulation distortion signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a typical RF power amplifier is used to amplify wideband signals including multiple frequency bands, then the amplifier can operate in a higher power region, but third-order intermodulation distortion and second harmonic components deteriorate when the interval between fundamental frequency components is narrow
Solution Approach 1:
The patent captures the harmful third-order intermodulation distortion components generated by the power amplifier and feeds them back through an inverting circuit to cancel themselves out. By converting the harmful distortion into a beneficial cancellation signal, the system reduces IM3 at the output while maintaining high output power capability
Solution Approach 2:
The patent implements a feedback mechanism where third-order intermodulation distortion components are extracted from the amplifier output, phase-inverted, and fed back to cancel the original distortion. This feedback loop continuously compensates for nonlinear distortion effects, enabling the amplifier to operate at higher power levels with improved linearity
2Power
If a typical RF power amplifier is used to amplify wideband signals including multiple frequency bands, then the amplifier can operate in a higher power region, but second harmonic components deteriorate when the interval between fundamental frequency components is narrow
Solution Approach 1:
The patent captures the harmful second harmonic components generated by the power amplifier and feeds them back through an inverting circuit to cancel themselves out. By converting the harmful harmonic distortion into a beneficial cancellation signal, the system reduces second harmonic content while maintaining high output power capability
3Object-generated harmful factors
If filtering circuits are added to reduce distortion components, then distortion characteristics improve, but module size and cost increase
Solution Approach 1:
The patent replaces traditional mechanical filtering circuits with an electronic feedback-based distortion cancellation system. Instead of using physical filters to remove distortion components, the system uses active circuits to generate and inject cancellation signals, achieving distortion reduction without the size and cost penalties of traditional filtering approaches
4Object-generated harmful factors
If filtering circuits are added to reduce distortion components, then distortion characteristics improve, but module cost increases
Solution Approach 1:
The patent replaces expensive passive filtering components with active feedback circuits that can be implemented using standard RF amplifier components. This substitution reduces bill of materials costs and simplifies manufacturing while achieving the same distortion reduction effect
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces distortion characteristics, including third-order intermodulation distortion and adjacent channel leakage ratio, without increasing module size or cost, and can be implemented on-chip, improving the overall performance of RF power amplifiers.
Implementation Method 1
The filter circuit uses inductor and capacitor elements to generate low impedance for fundamental frequency components and high impedance for second harmonic components
Implementation Method 2
the inverting circuit phase-inverts and attenuates second harmonic and third-order intermodulation distortion signals
Data Source
AI summary
A power amplifying device includes a first amplification circuit amplifying a first signal having a first frequency component and a second frequency component; a second amplification circuit amplifying a second signal received through an output node of the first amplification circuit; a filter circuit connected between a ground node of the first amplification circuit and a common ground to pass the first and second frequency components to the common ground through the ground node; and an inverting circuit that phase-inverts a signal including second harmonic components of the first and second frequency components that are received through the ground node of the first amplification circuit and provide the phase inverted signal to the output node of the first amplification circuit.