LC Resonant Linearization in Multi-Stage RF Power Amplifiers
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Solution Overview
Problem
Conventional RF amplifiers face challenges in maintaining linearity due to memory effects and distortion, which introduce high-frequency components and reduce amplification efficiency, especially in multi-stage designs.
Innovation Solution
A multi-stage RF power amplifier employs a video band phase and/or amplitude adjustment network, utilizing an inductor-capacitor (LC) tank circuit to compensate for phase distortion in the previous stage, improving linearity by modulating the carrier frequency and signal content bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional RF amplifier design is used, then the amplifier can provide high power amplification, but the linearity deteriorates due to memory effects and distortion
Solution Approach 1:
The patent applies preliminary action by introducing predistortion compensation through a diode before the signal enters the RF amplifier. The diode pre-distorts the input signal in advance so that the distortion produced by the amplifier cancels out the predistortion, resulting in linearized output. This resolves the contradiction by preparing the signal beforehand to counteract the expected non-linear effects of high-power amplification.
Solution Approach 2:
The patent uses a diode as an intermediary element to mediate between the input signal and the RF amplifier. The diode introduces controlled predistortion that acts as a compensating mechanism for the amplifier's inherent non-linearity. This intermediary component enables the system to maintain both high power and good linearity by actively counterbalancing distortion effects.
2Manufacturing precision
If predistortion compensation using a diode is applied, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent employs a simple diode as the predistortion element, which is a low-cost, straightforward component. Rather than using complex active predistortion circuits or sophisticated digital signal processing, the invention leverages the simple non-linear characteristics of a basic diode to achieve linearity improvement. This approach resolves the contradiction by using an inexpensive, simple component to achieve the desired linearity without significantly increasing device complexity.
3Reliability
If second harmonic short circuit or video band short circuit is used, then memory effect is reduced, but the solution requires additional circuit components
Solution Approach 1:
The patent combines the predistortion function with the existing amplifier input stage by integrating a diode into the signal path. Rather than adding separate, dedicated memory effect suppression circuits, the invention merges the linearity improvement function into the existing amplifier architecture. This resolves the contradiction by achieving memory effect suppression without requiring additional standalone components, thus minimizing the increase in device complexity.
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
This approach enhances linearity by 5-10 dBc in Adjacent Channel Leakage Ratio (ACLR) while maintaining high efficiency in deep class AB amplifiers, effectively suppressing memory effects and distortion.
Implementation Method 1
a resonant circuit comprising an inductor and a capacitor and having a resonant frequency (FR), the resonant circuit coupled to the input of the second amplification stage and compensating for the phase distortion caused by the first amplification stage at frequencies within the signal content bandwidth FS
Data Source
AI summary
A multi-stage Radio Frequency (RF) power amplifier is presented herein. According to one embodiment, the amplifier comprises: a first amplification stage configured to amplify an input signal to provide a first output signal having a phase distortion; a second amplification stage having an input and configured to amplify the first output signal that is received at the input to provide a second output signal, wherein the second output signal has a carrier frequency (FC) modulated by a signal content (S) having a signal content bandwidth (FS); and a resonant circuit comprising an inductor and a capacitor and having a resonant frequency (FR), the resonant circuit coupled to the input of the second amplification stage and compensating for the phase distortion caused by the first amplification stage at frequencies within the signal content bandwidth FS, wherein the resonant frequency FR is less than the signal content bandwidth FS.