Voltage-Combining Doherty PA Topology for Smaller RF Output Networks
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Solution Overview
Problem
Existing Doherty power amplifiers have a large footprint due to the use of surface mount device components in their output networks, which increases size and cost.
Innovation Solution
A compact Doherty power amplifier design utilizing a shunt inductor coupled to the output of the main amplifier and a shunt capacitor coupled to the output of the auxiliary amplifier, along with a transformer for voltage combining, reducing the need for impedance inverters and allowing for a more compact structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If surface mount device components are used in the output network, then the power amplifier can be manufactured with standard components, but the footprint and size increase
Solution Approach 1:
The patent combines multiple functions into integrated structures: the impedance inverter is merged with the output matching network, and the transformer serves both as a combining network and impedance transformation element. This integration eliminates the need for separate surface mount device components, reducing footprint while maintaining manufacturability through consolidated design elements.
Solution Approach 2:
The transformer in the output network serves multiple functions simultaneously: it acts as a combining network for the main and auxiliary amplifier outputs, provides impedance transformation, and functions as part of the output matching network. This multi-functionality reduces the number of discrete components needed, thereby reducing footprint while preserving ease of manufacture.
2Reliability
If impedance inverters are used in the output network, then the amplifier can achieve proper impedance matching, but the device complexity and size increase
Solution Approach 1:
The impedance inverter function is merged with the transformer and output matching network. The transformer's inherent impedance transformation properties are utilized to perform both impedance inversion and matching functions simultaneously, eliminating the need for separate impedance inverter components and reducing overall structural complexity.
Solution Approach 2:
The transformer is designed to perform multiple functions: it provides impedance inversion, serves as a combining network for parallel amplifier outputs, and acts as part of the output matching network. This multi-functionality achieves proper impedance matching while reducing device complexity by consolidating multiple functions into a single component.
3Reliability
If multiple discrete components are used for power splitting and phase shifting, then the amplifier can achieve proper signal distribution, but the footprint and cost increase
Solution Approach 1:
The power splitting and phase shifting functions are merged into an integrated circuit structure rather than using discrete surface mount components. The phase shifter and power divider are implemented as integrated elements that provide proper signal distribution to the main and auxiliary amplifiers while occupying minimal footprint space.
Solution Approach 2:
The patent transitions from a two-dimensional layout of discrete surface mount components to a three-dimensional integrated structure. The integrated circuit implementation allows signal distribution elements to be stacked or routed in multiple layers, reducing the footprint while maintaining the necessary signal splitting and phase shifting functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves high power efficiency with reduced size and cost, providing efficient power amplification for radio frequency signals with high peak-to-average power ratio.
Implementation Method 1
a transformer including a first inductor coupled between the output of the main amplifier and the output of the auxiliary amplifier, and a second inductor magnetically coupled with the first inductor
Data Source
AI summary
A Doherty power amplifier (PA) includes a main amplifier, an auxiliary amplifier, and a power splitting and phase shifting circuit configured to receive an input radio frequency (RF) signal, split the input RF signal into a first RF signal and a second RF signal, output the first RF signal to an input of the main amplifier, output the second RF signal to an input of the auxiliary amplifier, and provide a phase shift between the first RF signal and the second RF signal. The Doherty PA also includes a shunt inductor coupled to an output of the main amplifier, a shunt capacitor coupled to an output of the auxiliary amplifier, and a transformer. The transformer includes a first inductor coupled between the output of the main amplifier and the output of the auxiliary amplifier, and a second inductor magnetically coupled with the first inductor.