Doherty Amplifier Harmonic Tuning With Impedance Rotation
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Solution Overview
Problem
Existing Doherty amplifiers suffer from deteriorated performance due to inadequate processing of harmonic waves by a single harmonic tuning circuit, leading to reduced efficiency.
Innovation Solution
A Doherty amplifier design that incorporates a distributor, first and second amplifiers, a third node for signal combination, an impedance conversion circuit, and a harmonic tuning circuit that adjusts impedance within specific ranges on a Smith chart and electrical lengths to effectively handle both fundamental and second harmonic waves, minimizing the need for separate harmonic tuning circuits in each amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single harmonic tuning circuit is used in existing Doherty amplifiers, then the device complexity is reduced, but the performance deteriorates due to inability to effectively process harmonic waves from both main and peak amplifiers
Solution Approach 1:
An impedance conversion circuit is introduced as an intermediary component between the first amplifier and the combining node. This circuit converts the impedance in the second harmonic wave by 360°±45°, transforming the harmonic wave characteristics so that a single harmonic tuning circuit can effectively process harmonic waves from both amplifiers. The intermediary circuit enables one harmonic tuning circuit to achieve the performance previously requiring two separate circuits.
2Reliability
If separate harmonic tuning circuits are provided for main and peak amplifiers, then the harmonic wave processing performance is improved, but the device complexity and size increase
Solution Approach 1:
The patent merges the functions of two separate harmonic tuning circuits into a single harmonic tuning circuit by introducing an impedance conversion circuit. The impedance conversion circuit processes the second harmonic wave to enable one harmonic tuning circuit to handle harmonic waves from both the first and second amplifiers, thereby combining multiple functions into a single component and reducing overall device complexity.
Solution Approach 2:
The impedance conversion circuit changes the impedance parameter of the second harmonic wave by rotating it 360°±45°. This parameter transformation allows the single harmonic tuning circuit to effectively process harmonic waves that would otherwise require separate handling, achieving the same performance as multiple circuits through parameter modification.
3Object-generated harmful factors
If the impedance conversion circuit rotates impedance by 360°±45° in the second harmonic wave, then the harmonic interference is reduced, but the circuit complexity increases
Solution Approach 1:
The impedance conversion circuit applies a specific parameter change to the second harmonic wave by rotating the impedance 360°±45°. This controlled parameter transformation reduces harmonic interference by optimizing the impedance characteristics, while the circuit implementation remains relatively simple using standard impedance conversion techniques.
Data Source
AI summary
A Doherty amplifier includes a distributor, a first amplifier, a second amplifier, a third node, an impedance conversion circuit having a first end connected to a first node and a second end connected to the third node, and rotating an impedance viewed from the first amplifier to the third node with respect to an impedance viewed from the first amplifier to the first node within a range of 360°±45° on a Smith chart in a second harmonic wave, and a harmonic tuning circuit having a third end connected to a line connecting the first amplifier and the third node at the first node, and making an absolute value of an impedance with respect to a reference potential at the third end in the second harmonic wave smaller than an absolute value of an impedance with respect to the reference potential at the third end in the fundamental wave.