LC Doherty Power Amplifier for Load-Fluctuation Resistance
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Solution Overview
Problem
Existing power amplifier circuits face challenges in achieving both high efficiency and resistance to fluctuations in load impedance while maintaining a compact size.
Innovation Solution
The proposed power amplifier circuit incorporates a carrier amplifier, a peak amplifier, and specific combinations of inductors, capacitors, and a 90° hybrid coupler to optimize signal phase and impedance characteristics, reducing size and enhancing efficiency while improving resistance to load fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a quarter-wave line is used in a Doherty amplifier to achieve high efficiency, then efficiency is improved, but the circuit size increases
Solution Approach 1:
The patent replaces the quarter-wave line with an LC circuit consisting of inductors and capacitors. This parameter change transforms the physical implementation from a transmission line structure to a lumped element circuit, achieving the same phase shift and impedance transformation functions without requiring the large physical space of a quarter-wave line, thus resolving the contradiction between efficiency and circuit size
Solution Approach 2:
The patent substitutes the distributed element transmission line (quarter-wave line) with a lumped element LC circuit. This substitution replaces the mechanical/physical transmission line structure with electrical components (inductors and capacitors) that achieve the same electrical function in a compact form factor, resolving the space requirement issue while maintaining the Doherty amplifier's efficiency
2Reliability
If a balanced amplifier configuration is used to achieve resistance to fluctuations in load impedance, then reliability is improved, but efficiency deteriorates
Solution Approach 1:
The patent merges the advantages of both Doherty and balanced amplifier configurations into a single circuit. The carrier amplifier and peak amplifier are configured with LC circuits that provide both the load modulation characteristics of a Doherty amplifier (for high efficiency) and the balanced structure (for resistance to load impedance fluctuations). This merging allows simultaneous achievement of high efficiency and high reliability
Solution Approach 2:
The LC circuit configuration serves multiple functions simultaneously: it provides impedance transformation, phase shifting, and load modulation while maintaining balanced operation. This multi-functionality allows the circuit to achieve both high efficiency (through Doherty operation) and high resistance to load fluctuations (through balanced operation) within a single unified structure
Data Source
AI summary
A power amplifier circuit includes a carrier amplifier, which amplifies a first signal and outputs a first amplified signal from a first output terminal, a peak amplifier, which amplifies a second signal and outputs a second amplified signal from a second output terminal, a first inductor, connected to the first output terminal and a first node, a first capacitor, connected to the first node and the ground, a second inductor, connected to the second output terminal and a second node, a second capacitor, connected to the second node and the ground, a third inductor, connected to the first node and a third node connected to a load, and a third capacitor, connected to the second node and the third node.