Shielded Doherty Transmission Lines for Wideband RF Modules
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Solution Overview
Problem
Existing Doherty power amplifiers face challenges in achieving high efficiency across a wide band of frequencies due to narrowband performance and space constraints, with 90/180 Doherty amplifiers being unsuitable for limited module spaces and efficiency tradeoffs.
Innovation Solution
A Doherty power amplifier with a 90/180 configuration using hybrid transmission lines and shielding structures, integrated within a module platform, maintains phase coherency and reduces the use of lumped components, enabling efficient operation across a wide frequency band without impedance transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a 90/180 Doherty power amplifier is designed to provide broader RF bandwidth, then wideband performance is improved, but the device becomes unsuitable for use in limited space available in a power amplifier module
Solution Approach 1:
The patent implements a nested structure where the electromagnetic shield is integrated within the module substrate, and transmission lines are routed through multiple layers of the substrate. The shield encompasses the transmission lines, creating a compact nested arrangement that reduces overall device footprint while maintaining wideband performance
Solution Approach 2:
The patent transitions from planar transmission lines to three-dimensional routing through multiple substrate layers. Transmission lines are configured to extend in different spatial dimensions, allowing broader bandwidth performance in a compact footprint by utilizing vertical space rather than only horizontal expansion
2Area of stationary object
If lumped components are added to achieve 90/180 Doherty power amplifier in limited space, then space is saved, but efficiency deteriorates
Solution Approach 1:
The patent replaces lumped mechanical components (discrete capacitors, inductors, and transformers) with distributed electromagnetic structures etched directly into the substrate. Transmission lines and shielding are formed as integrated circuit features rather than separate discrete components, eliminating the efficiency losses associated with lumped element parasitics
Solution Approach 2:
The substrate serves multiple functions simultaneously: it provides mechanical support, routes transmission lines, provides electromagnetic shielding, and establishes ground references. This multi-functionality eliminates the need for separate lumped components, saving space while maintaining efficiency through integrated distributed structures
3Area of stationary object
If transmission lines are placed close together to save space, then area is reduced, but electromagnetic interference between transmission lines increases
Solution Approach 1:
The patent introduces an electromagnetic shield as an intermediary structure positioned between adjacent transmission lines. This shield acts as a mediator that blocks electromagnetic coupling between lines, allowing them to be placed closer together without significant interference. The shield is connected to ground, providing a reference potential that further reduces crosstalk
Solution Approach 2:
The patent applies electromagnetic shielding selectively in regions where transmission lines are in close proximity, rather than shielding the entire device. The shield is positioned specifically between adjacent signal paths to address local interference problems, preserving space while reducing harmful electromagnetic interactions where they occur
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 amplifier achieves high efficiency and wideband performance within limited space by maintaining phase coherency and reducing dispersion through hybrid transmission lines and electromagnetic shielding, suitable for various applications.
Implementation Method 1
an electromagnetic shield between the first phase shifter and the second phase shifter, the electromagnetic shield arranged to shield the first transmission line assembly from the second transmission line assembly
Data Source
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AI summary
A power amplifier module includes a first phase shifter, a second phase shifter, and an electromagnetic shield. The first phase shifter includes a first transmission line assembly to shift a first amplified signal by a first phase angle. The second phase shifter includes a second transmission line assembly to shift a second amplified signal by a second phase angle. The electromagnetic shield is arranged to shield the first transmission line assembly from the second transmission line assembly. The power amplifier module may have, for example, Doherty amplifier configuration.