Compact RF Hybrid Coupler Layout for Broadband Base Station Coupling
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Solution Overview
Problem
Existing multi-port directional RF hybrid couplers in base station antenna systems are limited by large footprint and inadequate frequency bandwidth, which hinders their efficiency and versatility in cellular communication systems.
Innovation Solution
A compact, four-port RF hybrid coupler design with asymmetrically configured primary and coupled traces, serpentine-shaped segments, and defected ground structures, along with energy cancellation circuits, to enhance coupling and frequency bandwidth while maintaining a small form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional multi-port directional RF hybrid couplers are used, then coupling functionality is provided, but the footprint is large and frequency bandwidth is limited
Solution Approach 1:
The coupled traces are divided into multiple trace segments connected in series, where each segment contributes to the overall coupling degree. This segmentation allows the coupler to achieve broadband coupling while maintaining a compact footprint, as the segmented structure can be optimized for different frequency ranges within a smaller area
Solution Approach 2:
The coupler employs asymmetric configuration where the first coupled trace provides a first degree of coupling at its first end and a third degree of coupling at its second end, with the third degree being unequal to the first degree. Similarly, the second coupled trace provides unequal coupling degrees at its ends. This asymmetric design enables broadband operation by optimizing coupling characteristics across different frequency ranges while reducing the overall footprint
2Reliability
If conventional hybrid couplers with symmetric trace configuration are used, then simple manufacturing is achieved, but coupling strength and bandwidth are insufficient
Solution Approach 1:
The patent implements asymmetric trace configuration where coupled traces have different coupling degrees at different ends. The first coupled trace provides unequal coupling degrees (first degree at first end, third degree at second end), and the second coupled trace provides unequal coupling degrees (fourth degree at first end, second degree at second end). This asymmetric design strengthens coupling across broadband frequencies while the complexity is managed through systematic trace segmentation and strategic placement of asymmetric elements
3Area of stationary object
If compact design is implemented, then footprint is reduced, but coupling bandwidth may be compromised
Solution Approach 1:
By segmenting the coupled traces into multiple sections connected in series, the patent achieves broadband coupling within a compact footprint. Each segment can be optimized for specific frequency ranges, and their series combination provides extended bandwidth coverage without requiring large substrate area
Solution Approach 2:
The patent utilizes parameter changes in the trace segments, including varying trace widths, lengths, and spacing between segments to optimize coupling degrees across different frequency ranges. This allows the compact coupler to maintain strong coupling over broadband frequencies by adjusting electromagnetic field distribution through parameter optimization
Data Source
AI summary
A four-port RF hybrid coupler includes a substrate having first and second primary traces and first and second coupled traces on a first surface thereof. The first coupled trace has: (i) a first end configured to provide a first degree of RF coupling to a first end of the first primary trace when the RF hybrid coupler is active, and (ii) a second end configured to provide a third degree of RF coupling to a second end of the second primary trace when the RF hybrid coupler is active. The second coupled trace has: (i) a first end configured to provide a fourth degree of RF coupling to the first end of the second primary trace when the RF hybrid coupler is active, and (ii) a second end configured to provide a second degree of RF coupling to the second end of the first primary trace when the RF hybrid coupler is active. First and second energy cancellation circuits are also provided. The first energy cancellation circuit includes a first termination coupler having an input port electrically coupled to an end of the second coupled trace, and the second energy cancellation circuit includes a second termination coupler having an input port electrically coupled to an end of the first coupled trace.