Inverted Doherty Amplifier Topology for Wider RF Bandwidth
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Solution Overview
Problem
Conventional Doherty amplifiers have limited RF fractional bandwidth due to bandwidth constraints caused by impedance-matching components, which restrict their performance in high-speed, high-power, and broad-bandwidth applications, particularly in future RF communication systems.
Innovation Solution
The design of an inverted Doherty amplifier with specific impedance-matching components and an impedance inverter configuration, including microstrip transmission lines and phase delays, transforms input impedances to optimize power transfer and increase RF fractional bandwidth, allowing for broader signal bandwidth and improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional impedance-matching components are used in Doherty amplifiers, then the amplifier can achieve stable operation, but the RF fractional bandwidth is limited
Solution Approach 1:
The patent inverts the conventional Doherty amplifier topology by placing the impedance inverter between the peaking amplifier and the combining node, rather than between the main amplifier and the combining node. This inversion allows the impedance-matching function to be distributed differently, enabling broader bandwidth operation while maintaining stable operation through the preserved impedance transformation functionality.
Solution Approach 2:
The patent modifies the impedance parameters at the combining node and changes the configuration of impedance-matching components to achieve broader bandwidth. Specifically, the impedance inverter is configured with specific characteristic impedance values and phase delays that transform the input impedance to optimize power transfer across a wider frequency range, thereby improving RF fractional bandwidth while maintaining operational stability.
2Loss of energy
If impedance-matching components are added to optimize power transfer, then power transfer efficiency improves, but device complexity increases
Solution Approach 1:
The impedance inverter serves multiple functions simultaneously: it provides impedance transformation, phase delay compensation, and bandwidth extension. By integrating these functions into a single component configuration rather than using separate components for each function, the patent achieves improved power transfer efficiency while minimizing the increase in device complexity.
Solution Approach 2:
The impedance inverter acts as an intermediary element between the peaking amplifier and the combining node, mediating the impedance mismatch and phase differences. This intermediary component enables optimal power transfer by transforming impedances and compensating for phase delays without requiring complex multi-component networks, thus improving efficiency with minimal added complexity.
Data Source
AI summary
Apparatus and methods for an inverted Doherty amplifier operating at gigahertz frequencies are described. RF fractional bandwidth and signal bandwidth may be increased over a conventional Doherty amplifier configuration when impedance-matching components and an impedance inverter in an output network of the inverted Doherty amplifier are designed based on characteristics of the main and peaking amplifier and asymmetry factor of the amplifier.