Doherty PA Harmonic Combiner for Back-Off Efficiency and Linearity
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Solution Overview
Problem
Power amplifiers in 5G communication systems, particularly Doherty Power Amplifiers (DPAs), face challenges in achieving high efficiency while maintaining linearity over a wide range of power levels and bandwidths, especially in millimeter wave applications where electronic components have lower gain and are prone to inefficiencies due to saturation and harmonic issues.
Innovation Solution
The integration of a novel 2nd harmonic combiner network within the DPA, featuring a λ/4 transmission line and LC resonant circuit, which injects the 2nd harmonic from the carrier PA into the peaking PA at back-off, enhancing efficiency by acting as a load puller and ensuring proper harmonic termination, thereby maintaining linearity and efficiency across the spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional DPA design is used, then circuit elegance and basic efficiency are achieved, but efficiency at back-off power levels deteriorates and harmonic issues arise
Solution Approach 1:
The patent converts the harmful 2nd harmonic signals generated by the carrier PA into a beneficial resource by injecting them into the peaking PA. This harmonic injection technique transforms what would normally be wasted energy or interference into a useful signal that improves back-off efficiency and linearity, directly addressing the contradiction between efficiency and harmonic issues
Solution Approach 2:
The combiner network is designed to perform multiple functions simultaneously: it combines the fundamental frequency signals from carrier and peaking PAs, terminates harmonics, and injects the 2nd harmonic from the carrier PA into the peaking PA. This multi-functionality resolves the contradiction by integrating harmonic management and efficiency enhancement into a single circuit structure
2Use of energy by moving object
If PAs operate in saturated regime to improve efficiency, then energy efficiency increases, but linearity deteriorates
Solution Approach 1:
The patent implements a form of feedback by injecting the 2nd harmonic signal from the carrier PA (operating in saturation) into the peaking PA. This creates a controlled interaction where the saturated carrier PA's harmonic content is fed back to the peaking PA, enabling the system to maintain linearity while operating efficiently in the saturated regime
Solution Approach 2:
The system combines two different PA operating modes into a composite structure: the carrier PA operates in saturated regime for efficiency while the peaking PA operates in linear regime. The combiner network integrates these two composite operating states, allowing the overall system to achieve both high efficiency and linearity simultaneously
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 solution significantly increases the efficiency of DPAs in millimeter wave applications by optimizing the operation of the peaking PA, ensuring high efficiency and linearity across the entire range of power levels and bandwidths, even in saturated regimes, thus addressing the limitations of traditional DPA designs.
Implementation Method 1
The harmonic injection is implemented in a novel combiner network to provide increased efficiency for the DPA at back-off
Implementation Method 2
featuring a λ/4 transmission line and LC resonant circuit
Implementation Method 3
The combiner network includes a λ/4 transmission line section and two λ/8 transmission line sections in parallel with a LC resonant circuit
Data Source
AI summary
Examples disclosed herein relate to a Doherty Power Amplifier (“DPA”) with integrated second harmonic injection. The DPA includes an amplifier circuit having a carrier amplifier and a peaking amplifier, and a combiner network coupled to the amplifier circuit, the combiner network having a plurality of transmission lines and a LC resonant circuit to inject a second harmonic from the carrier amplifier into the peaking amplifier.