Multi-Layer PCB Surface Wave Excitation Device
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Solution Overview
Problem
Existing surface wave excitation devices are unable to directly interconnect with printed circuit boards (PCBs) to propagate surface waves effectively, limiting their integration and performance in communication systems.
Innovation Solution
A surface wave excitation device utilizing a multi-layer PCB structure with at least five layers of PCBs, where copper wires form closed regions that gradually increase impedance, allowing conversion from TEM to TM mode and enabling direct integration with PCBs for efficient surface wave propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional cone structure is used for surface wave excitation, then conversion from TEM mode to TM mode is achieved, but the device size becomes too large to directly interconnect with PCB
Solution Approach 1:
The invention transitions from a three-dimensional cone structure to a two-dimensional planar structure by unfolding the conical surface onto a PCB layer. This dimensional reduction allows the excitation device to be directly integrated into the PCB while maintaining the essential impedance transformation function for surface wave generation.
Solution Approach 2:
The conical structure is segmented into multiple discrete impedance elements (open stubs, short stubs, and transmission line sections) distributed across the PCB layer. This segmentation enables the continuous impedance transformation to be approximated by discrete components, achieving both miniaturization and functionality.
2Ease of manufacture
If the excitation device is miniaturized for PCB integration, then direct interconnection is enabled, but the conversion efficiency from TEM to TM mode may be compromised
Solution Approach 1:
The invention systematically varies the impedance parameters of transmission line sections and stub lengths to create a progressive impedance transformation profile. By carefully controlling the characteristic impedance and physical dimensions of each segment, the design achieves effective mode conversion within the constrained PCB footprint.
Solution Approach 2:
The impedance transformation is prepared in advance through the fixed geometric configuration of the planar structure. The progressive impedance change is built into the device geometry before operation, ensuring reliable and repeatable mode conversion without requiring dynamic adjustment during operation.
3Reliability
If a large cone structure is used, then sufficient bandwidth and low loss are achieved, but the device cannot be directly integrated with PCB
Solution Approach 1:
The invention merges the surface wave excitation function with the PCB structure itself. The transmission line and excitation elements are combined into a single planar integrated structure, eliminating the need for separate three-dimensional components and reducing overall system complexity while maintaining transmission performance.
Solution Approach 2:
The mechanical three-dimensional cone structure is replaced with an electromagnetic planar transmission line structure. This substitution maintains the essential function of impedance transformation and surface wave excitation while adapting to the two-dimensional constraints of PCB technology.
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 device achieves efficient conversion and propagation of surface waves with reduced conductor loss and increased bandwidth, facilitating integration with PCBs and improving communication performance.
Implementation Method 1
convert the signal propagated in the TEM mode to the surface wave propagated in the TM mode
Implementation Method 2
The surface wave is a wave in which an electromagnetic field is transmitted in circles outside a conductor cable. The transmission mode of the surface wave is the TM mode.
Implementation Method 3
The conductor cable only guides the electromagnetic field transmission, and no current is transmitted inside the conductor cable.
Data Source
Figure 1~2b
Figure 2c~3b
Figure 3c~4
AI summary
A surface wave excitation device and a printed circuit board are provided. The surface wave excitation device includes: a multilayer PCB structure and a transmission line (16), where the multilayer PCB structure includes at least five layers of PCBs (11, 12, 13, 14, and 15). The transmission line (16) is disposed on a wire layer PCB (13), and PCBs (11 and 12) and PCBs (14 and 15) of a same quantity of layers are respectively disposed above and below the wire layer PCB (13). A copper wire is disposed on each layer of PCB (11, 12, 14, and 15), and the copper wire forms a closed region. Closed regions on the PCBs (11 and 12) and the PCBs (14 and 15) that are respectively disposed above and below the wire layer PCB (13) and that have a same distance from the wire layer PCB (13) are in a same shape, and a closed region on a PCB (11, 12, 14, or 15) farther away from the wire layer PCB (13) occupies a larger area. There are two closed regions (13a and 13b) on the wire layer PCB (13), one of which is disposed on one side of the transmission line (16), and the other is disposed on the other side of the transmission line (16), and shapes of the two closed regions (13a and 13b) are mutually symmetrical with the transmission line (16) as a symmetry axis. Integration of the surface wave excitation device and the PCB is implemented, so that surface wave is easy to propagate.