Single-Layer PCB 180° Hybrid Coupler With Strong Broadband Coupling
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Solution Overview
Problem
Conventional hybrid couplers implemented on single-layer printed circuit boards face limitations in achieving strong coupling due to minimum distance constraints in fabrication, leading to reduced performance in applications requiring high coupling levels, while air stripline implementations increase costs.
Innovation Solution
The design incorporates a 90° hybrid coupler with quarter wavelength conductive stubs and a delay line on a printed circuit board with a single dielectric layer, allowing for increased coupling and phase control across a broad bandwidth, and optionally includes a band pass filter and metallized ground plane for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional printed circuit board fabrication techniques are used with minimum distance constraints, then manufacturing cost is reduced, but coupling strength is limited
Solution Approach 1:
The patent transitions from planar 2D trace coupling to 3D vertical coupling by positioning conductive traces on opposite sides of the PCB and utilizing vias to create through-board coupling paths. This dimensional change enables strong coupling without requiring traces to be in close proximity on the same layer, thus maintaining standard fabrication capabilities while achieving high coupling levels.
Solution Approach 2:
The patent introduces vias as intermediary elements that connect conductive traces on opposite sides of the PCB. These vias serve as coupling mediators, allowing RF energy to transfer between layers while maintaining electrical isolation on each individual layer. This intermediary structure enables controlled coupling without requiring adjacent trace placement.
2Reliability
If air stripline implementations are used to achieve strong coupling, then coupling strength is improved, but manufacturing cost increases
Solution Approach 1:
The patent creates an artificial stripline-like coupling environment by using vias to replicate the electromagnetic coupling behavior of air stripline structures. Instead of requiring actual air stripline construction, the via-connected trace configuration copies the essential coupling characteristics, achieving similar performance with standard PCB fabrication processes.
Solution Approach 2:
The patent replaces the mechanical air stripline structure with an equivalent electrical implementation using PCB traces and vias. The electromagnetic coupling mechanism is preserved through careful design of trace geometry, via placement, and layer configuration, substituting the physical air gap structure with an electrically equivalent PCB-based system.
3Device complexity
If interdigitated transmission line segments are used on single layer boards, then manufacturing simplicity is maintained, but coupling control is limited due to minimum distance requirements
Solution Approach 1:
The patent moves the coupling interaction from the 2D plane to the 3D vertical dimension by placing traces on opposite PCB layers and using vias to establish coupling paths. This eliminates the need for precise lateral positioning and minimum distance constraints, as coupling occurs through the board thickness rather than along the surface.
Solution Approach 2:
The patent divides the coupling function into separate segments: input traces on one layer, output traces on the opposite layer, and vias as coupling segments connecting them. This segmentation allows independent optimization of each component and enables precise control of coupling characteristics through via placement and trace geometry without requiring tight tolerances on trace spacing.
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 solution achieves low return loss and constant phase difference over a broad frequency range, enabling efficient RF signal splitting and combining with reduced insertion loss and increased coupling, while maintaining a compact and cost-effective design.
Implementation Method 1
Hybrid couplers are often implemented as a pair of RF transmission lines that are arranged so that RF energy may couple between the two transmission lines
Implementation Method 2
A first quarter wavelength conductive stub is coupled to the second output transmission line
Data Source
AI summary
A hybrid coupler includes a 90° hybrid coupler and a first quarter wavelength conductive stub. The 90° hybrid coupler includes a coupling section, a first input transmission line that is coupled to the coupling section, a second input transmission line that is coupled to the coupling section, a first output transmission line that is coupled to the coupling section and a second output transmission line that is coupled to the coupling section. The first quarter wavelength conductive stub is coupled to the second output transmission line.