3-Way Doherty Amplifier Phase Shift Network for Bandwidth
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Solution Overview
Problem
Conventional Doherty amplifier topologies, such as the two-way Doherty amplifier, face limitations in bandwidth and efficiency when operating in back-off conditions, particularly in cellular communication networks, where high bandwidth and efficient power amplification are required across multiple frequency bands.
Innovation Solution
A 3-way Doherty amplifier topology is integrated into a semiconductor die, utilizing phase shifting elements like bond wires and capacitors to facilitate efficient power combining and reduce mutual coupling, enabling a wider bandwidth and improved efficiency by optimizing the impedance and phase shifts within the amplifier stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional two-way Doherty amplifier topology is used, then the amplifier operates efficiently at 6 dB back-off, but the bandwidth is limited to about 5% and efficiency decreases in other back-off regions
Solution Approach 1:
The amplifier is segmented into three independent amplifying stages (main stage, first peak stage, second peak stage) instead of the conventional two stages. Each stage can be independently controlled and optimized, allowing the system to maintain high efficiency across multiple back-off regions (6 dB, 8 dB, and 9.5 dB) while achieving a wider bandwidth of up to 20%.
Solution Approach 2:
The amplifier employs dynamic load-line modulation through the output network that includes impedance elements with specific phase shifts (180° for the first peak stage output, 90° for the main stage output). This dynamic impedance transformation allows the main amplifier to operate efficiently across its full dynamic range while adapting to different back-off conditions.
2Loss of energy
If more complex Doherty topologies (asymmetric or three-way) are used to improve efficiency and bandwidth, then efficiency response with multiple maxima is achieved, but integration as an integrated circuit becomes difficult
Solution Approach 1:
The invention transforms the complex three-way Doherty topology into an integrable form by carefully selecting impedance parameters and phase shift values for the output network. The specific configuration (180° phase shift for first peak stage, 90° for main stage) simplifies the mutual coupling effects between impedance elements, enabling successful integration while maintaining the efficiency benefits of three-way topology.
Solution Approach 2:
The output network acts as an intermediary between the three amplifying stages and the final output, managing the complex interactions and mutual coupling effects. By positioning the impedance elements with specific phase shifts in this intermediary network, the invention facilitates integration while preserving the performance benefits of the three-way topology.
Data Source
AI summary
A die is described comprising at least one 3-way Doherty amplifier comprising a main stage, a first peak stage and a second peak stage. An input is connected to an input network which is connected to the main stage, first peak stage and second peak stage. The input network includes a first impedance connected to an input of the first peak stage and providing a −90° phase shift and a second impedance connected to an input of the second peak stage and providing a 90° phase shift. An output is connected to an output network which is connected to the main stage, first peak stage and second peak stage. The output network includes a third impedance connected to the output of the first peak stage and providing a 180° phase shift and a fourth impedance connected to the output of the main stage and providing a 90° phase shift.