Doherty Amplifier Circuit Using Hybrid Coupler Harmonic Extraction
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Solution Overview
Problem
The increase in the number of frequency bands required for compatibility with new communication standards, such as 4G and 5G, leads to an increase in circuit size due to the need for multiple filter circuits in Doherty amplifier circuits, which are not compatible with existing Doherty amplifier configurations.
Innovation Solution
A Doherty amplifier circuit design that includes a 90° hybrid coupler with an isolation terminal receiving a second harmonic signal, a carrier amplifier, and a peak amplifier, which compensates for intermodulation distortion without using filter circuits, thereby reducing circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filter circuits are introduced to extract second harmonic for intermodulation distortion compensation, then intermodulation distortion is suppressed, but circuit size increases
Solution Approach 1:
The patent extracts only the necessary second harmonic signal through the isolation terminal of the 90° hybrid coupler, rather than using full filter circuits. This selective extraction achieves intermodulation distortion compensation while minimizing the added circuit area.
Solution Approach 2:
The isolation terminal of the 90° hybrid coupler, which is part of the existing signal distribution structure, is repurposed to receive and process the second harmonic signal. This multi-functional use of existing circuit elements avoids adding separate filter circuits, thereby reducing circuit size while maintaining distortion compensation capability.
2Adaptability or versatility
If multiple filter circuits are added for compatibility with multiple frequency bands (4G, 5G), then frequency band compatibility is improved, but circuit size increases
Solution Approach 1:
The 90° hybrid coupler and its isolation terminal serve multiple functions: signal distribution for Doherty amplifier operation and second harmonic extraction for intermodulation distortion compensation across multiple frequency bands. This universal structure eliminates the need for separate filter circuits for each frequency band.
Solution Approach 2:
The patent merges the second harmonic extraction function with the existing signal distribution network by utilizing the isolation terminal of the 90° hybrid coupler. This consolidation integrates multiple functions into a single structure, achieving multi-frequency band compatibility without proportionally increasing circuit size.
3Reliability
If additional isolation structures are added to ensure isolation between distortion compensation device and Doherty amplifier, then operational interference is reduced, but circuit size increases
Solution Approach 1:
The isolation terminal of the 90° hybrid coupler inherently provides the necessary isolation between the second harmonic processing path and the main signal path. By utilizing this built-in isolation capability of the hybrid coupler structure, additional isolation components are eliminated, maintaining operational reliability while reducing circuit size.
Data Source
AI summary
A Doherty amplifier circuit includes a 90° hybrid coupler that includes an input terminal receiving a first input signal, a first output terminal outputting a first output signal on the basis of the first input signal, a second output terminal outputting, on the basis of the first input signal, a second output signal different in phase by 90° from the first output signal, and an isolation terminal whose isolation from the input terminal is ensured; a carrier amplifier that amplifies the first output signal to output a first amplified signal; and a peak amplifier that amplifies the second output signal to output a second amplified signal. The isolation terminal is a terminal which receives a second harmonic in the second harmonic frequency band of the first input signal.