Antenna Duplexer Ground Segmentation for TX/RX Isolation
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Solution Overview
Problem
The demand for a smaller and lower-height antenna duplexer with improved attenuation and isolation characteristics is increasing due to the spread of multiband/multimode systems and additional wireless interface functions, while existing designs face challenges in reducing dimensions without compromising performance.
Innovation Solution
The antenna duplexer features a separated ground pattern for the receive filter, with a seal ring portion connected to the receive filter's ground pattern through a conductor pattern, including side castellations on the package's inner or outer walls, which enhances isolation and attenuation characteristics, allowing for reduced dimensions and height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common ground pattern is used in the package, then the structure is simpler and easier to manufacture, but the isolation characteristic between transmit and receive terminals deteriorates
Solution Approach 1:
The ground pattern is segmented into separate ground patterns for the transmit filter and receive filter. This segmentation prevents mutual interference between transmit and receive signals by providing electrically isolated reference potentials, thereby improving isolation characteristics while maintaining manufacturing feasibility through standardized PCB fabrication processes.
Solution Approach 2:
Different regions of the package are assigned different ground quality characteristics. The transmit filter region and receive filter region are provided with locally optimized ground patterns that are electrically isolated from each other, allowing each region to have the ground characteristics best suited for its specific function while maintaining overall package integrity.
2Area of stationary object
If the package dimensions are reduced, then the antenna duplexer size is smaller, but the attenuation characteristic deteriorates
Solution Approach 1:
The ground pattern is extended into the vertical dimension by forming it on both the upper and lower surfaces of the package substrate. This three-dimensional ground configuration increases the effective ground area and improves signal reference stability without increasing the planar footprint, thereby maintaining attenuation characteristics while reducing package dimensions.
Solution Approach 2:
The ground pattern is designed to utilize the entire package volume by extending across multiple layers and surfaces. The upper and lower ground patterns are nested within the package structure, maximizing the use of available space for ground reference while minimizing the external dimensions of the package.
3Length of stationary object
If the package height is reduced, then the antenna duplexer height is lower, but the isolation characteristic deteriorates
Solution Approach 1:
The ground pattern utilizes the lateral surfaces of the package by forming side castellations on the peripheral walls. This transforms the ground reference from a purely planar structure to a three-dimensional structure that wraps around the package, providing enhanced isolation between transmit and receive paths without increasing the package height.
Solution Approach 2:
The ground isolation function is achieved through electromagnetic field management rather than mechanical separation. The separated ground patterns and side castellation structures create electromagnetic isolation between transmit and receive circuits, replacing the need for increased physical distance or height to achieve the same isolation effect.
Data Source
AI summary
An antenna duplexer is provided, which can be built with a smaller size and lower height than ever without compromising out-of-band attenuation characteristic and isolation characteristic between a transmit terminal and a receive terminal. The antenna duplexer includes a transmit filter provided between an antenna terminal and the transmit terminal, and a receive filter provided between the antenna terminal and the receive terminal. The filters are enclosed by a package, in which a ground pattern for the receive filter is separated from other ground patterns.