Class-F Power Amplifier Harmonic Termination for RF Efficiency
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Solution Overview
Problem
There is a need for improved power amplifiers in RF electronics, particularly for smartphone applications, to increase battery life and efficiency, especially when handling high peak-to-average-power ratio signals like those in the LTE standard, while maintaining high gain and output power with minimal noise and stability concerns.
Innovation Solution
A Class-F RF power amplifier design incorporating a hybrid output network with discrete SMT components, wirebonds, and on-die chip capacitors, featuring termination circuits that provide short circuits at even harmonics and open circuits at odd harmonics, along with a resonant circuit that blocks odd harmonics, to achieve high efficiency and reduce sensitivity to supply voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional power amplifier designs are used, then output power and gain can be achieved, but efficiency is insufficient leading to reduced battery life
Solution Approach 1:
The patent changes the impedance parameters at different harmonic frequencies by introducing termination circuits that provide specific short and open circuit conditions at even and odd harmonics respectively, transforming the amplifier operation to achieve higher efficiency
Solution Approach 2:
The patent segments the harmonic frequency spectrum into even and odd harmonics, applying different termination strategies (short circuit for even harmonics, open circuit for odd harmonics) to each segment, enabling optimized efficiency across the frequency spectrum
2Loss of energy
If efficiency is increased through complex circuits, then battery life improves, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple harmonic terminations into a unified Class-F amplifier architecture with systematic termination circuits, achieving high efficiency without proportionally increasing complexity through integrated design
3Productivity
If harmonic terminations are added to improve efficiency, then power amplifier performance increases, but circuit complexity increases
Solution Approach 1:
The patent changes the impedance parameters at different harmonic frequencies by introducing termination circuits that provide specific short and open circuit conditions at even and odd harmonics respectively, transforming the amplifier operation to achieve higher efficiency
Solution Approach 2:
The termination circuits are designed to provide multiple functions simultaneously: shorting even harmonics, opening odd harmonics, and maintaining broadband operation, reducing the need for separate circuits for each function
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 design achieves ultra-high efficiency of about 80% for low-band frequencies and 75% for ultra-high-band frequencies, outperforming existing state-of-the-art designs without increasing the die or PCB area, and provides linear power with reduced noise and stability issues.
Implementation Method 1
The termination circuit is configured to provide a short circuit at a second harmonic of the amplified RF signal
Implementation Method 2
The resonant circuit is coupled to the output of the power amplifier transistor. The resonant circuit is configured to provide an open circuit at a third harmonic of the amplified RF signal
Data Source
AI summary
Aspects of this disclosure relate to efficient power amplifiers, such as class-F power amplifiers. A power amplifier transistor can provide an amplified RF signal. A termination can be coupled to an output of the power amplifier transistor and configured to provide a short circuit at a second harmonic. In some instances, the termination circuit can provide an open circuit at a third harmonic. A resonant circuit can be coupled to the output terminal of the power amplifier transistor and configured to provide an open circuit at the third harmonic. In certain embodiments, an input termination circuit coupled to an input terminal of the power amplifier transistor can provide a short circuit at the second harmonic. The power amplifiers of this disclosure can be implemented, for example, in envelope tracking applications.