Air Loaded Stripline Using Conventional PCB Fabrication
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Solution Overview
Problem
Diplexers used in dual-band systems are difficult and expensive to implement, particularly due to the challenges of integrating air loaded stripline filters with other circuit components, as they often require complex fabrication technologies and are bandwidth limited, especially at high frequencies.
Innovation Solution
An air loaded stripline is produced using conventional printed circuit board techniques, featuring conductive traces on a substrate with spacer elements and ground planes, allowing for integration with other circuit components and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air loaded stripline filters are implemented using conventional suspended stripline structures with metallic cavities, then low insertion loss and wide bandwidth are achieved, but device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The patent extracts the essential function of the metallic cavity (providing ground reference and shielding) while removing the complex three-dimensional metallic structure. Instead, it uses a planar ground plane on the opposite side of the substrate and peripheral ground structures, maintaining the electromagnetic field confinement and shielding functions with significantly reduced structural complexity.
Solution Approach 2:
The patent replaces the mechanical/metallurgical fabrication processes required for traditional suspended stripline with complex metallic cavities and shielding channels with conventional PCB fabrication techniques. The stripline is implemented as a printed conductive trace on a substrate, allowing standard PCB manufacturing processes to be used instead of complex metal forming, machining, and assembly operations.
2Reliability
If air loaded stripline filters are implemented with suspended structures in metallic cavities, then filtering performance is improved, but ease of manufacture deteriorates due to requiring complex fabrication technologies
Solution Approach 1:
The patent substitutes mechanical/metallurgical fabrication with PCB fabrication processes. The stripline filter is created using standard PCB techniques such as printing, photo etching, or etching to form conductive traces on a substrate, which can then be assembled using conventional PCB assembly methods rather than complex metal component fabrication and assembly.
Solution Approach 2:
The patent makes the PCB substrate serve multiple functions simultaneously: it provides the mechanical support for the stripline, acts as the dielectric medium for electromagnetic wave propagation, provides the ground plane for reference potential, and serves as the mounting structure for the entire filter assembly. This multi-functionality eliminates the need for separate metallic cavity and support structures.
3Adaptability or versatility
If transmission line structures are printed on a substrate suspended in a shielding channel, then integration with larger circuits is facilitated, but device complexity increases due to requiring bottom metallic pieces and metallic caps
Solution Approach 1:
The PCB substrate is designed to perform multiple functions: it supports the printed transmission line structure, provides the dielectric medium, serves as the ground plane, and acts as the structural support that eliminates the need for separate bottom metallic pieces and caps. The peripheral ground structures on the substrate provide both electrical reference and electromagnetic shielding functions.
Solution Approach 2:
The patent extracts and eliminates the redundant bottom metallic piece and metallic cap structures from the design. The shielding and ground reference functions are achieved through the peripheral ground structures and ground planes integrated into the PCB substrate itself, removing unnecessary components and simplifying the overall structure.
Data Source
AI summary
Air loaded stripline assemblies and methods for providing same are disclosed. The air loaded stripline assembly includes circuit board layers interconnected to one another. A layer containing a conductive trace forming a stripline is connected to spacer layers. The spacer layers include voids or relieved areas, that define cavities adjacent areas of the stripline layer on which the stripline is formed. Ground plane layers are interconnected to the spacer layers, bounding the cavities. The air loaded stripline assembly can additionally incorporate conductive vias for electrically interconnecting the stripline to other components or assemblies. The air loaded stripline assembly can be formed using conventional printed circuit board techniques.