Coupled-Inductor Doherty Amplifier for Broadband Back-Off Efficiency
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Solution Overview
Problem
Conventional Doherty power amplifiers suffer from narrow bandwidth and large area, with existing optimizations either introducing resonance at high frequencies or poor load modulation effects.
Innovation Solution
A Doherty power amplifier design utilizing a quadrature coupler with coupled inductors providing distributed parasitic capacitance, eliminating the need for additional capacitors and combining inductors into transformers via a T equivalent model to reduce area and improve back-off efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional Doherty structure is used, then back-off efficiency is improved, but bandwidth is narrow and area is large
Solution Approach 1:
The patent combines multiple inductors into transformer structures (third coupled inductor and fourth coupled inductor) that perform both impedance transformation and load modulation functions simultaneously. This merging of functions reduces the number of discrete components and minimizes the overall circuit area while maintaining the Doherty back-off efficiency improvement.
Solution Approach 2:
The coupled inductors in the load modulation network serve multiple purposes: they provide impedance transformation, enable load modulation for efficiency improvement, and contribute to bandwidth expansion through their coupled resonance characteristics. This multi-functionality allows a single component to address multiple performance requirements.
2Area of stationary object
If a pi-network with resonant inductance is used to reduce area, then area is reduced, but resonance at high frequency limits broadband performance
Solution Approach 1:
The patent changes the resonant parameters by using coupled inductors with specific coupling coefficients and turns ratios. The coupled resonance created by the third and fourth coupled inductors produces multiple resonant frequencies that extend the operational bandwidth, unlike the single resonant frequency of a conventional pi-network.
3Device complexity
If transmission line matching is used in load modulation network, then structure is simple, but load modulation effect is poor and back-off efficiency is not significantly improved
Solution Approach 1:
The patent replaces traditional transmission line matching structures with coupled inductor transformers that provide stronger and more controllable load modulation effects. The magnetic coupling mechanism enables more effective impedance transformation and load modulation compared to distributed transmission line structures.
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 design achieves a compact structure with improved back-off efficiency, reduced connection loss, and enhanced overall performance by minimizing area and maintaining broadband characteristics.
Implementation Method 1
a quadrature coupler including a first coupled inductor and a second coupled inductor
Implementation Method 2
coupled inductors providing distributed parasitic capacitance
Data Source
AI summary
The present disclosure discloses a Doherty power amplifier, including: a quadrature coupler including a first coupled inductor and a second coupled inductor, the quadrature coupler being configured to split an input signal into a first signal and a second signal; a first amplifier circuit, configured to amplify the first signal; a second amplifier circuit, configured to amplify the second signal; and a load modulation network, which is an output voltage-combined Doherty load modulation network using a T equivalent model. An overlapping part of the coupled inductors is used to provide distributed parasitic capacitance, thereby eliminating the need to set an additional capacitor in the quadrature coupler, and therefore reducing an area. Through the T equivalent model, a quarter-wavelength transmission line is equated to the load modulation network of the embodiments of the present disclosure, multiple inductors are combined into transformers with small areas.