Multilayer Filter Group Layout for Higher Inter-Filter Isolation
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Solution Overview
Problem
Existing filter groups face challenges in improving isolation between filters, which affects the performance of wireless communication modules, particularly in high-frequency applications like 5G NR.
Innovation Solution
The filter group design includes first and second filters formed on a single multilayer substrate, with paired ground conductor layers having overlapping areas that are disconnected to enhance isolation, and the filters are configured to be mirror symmetrical or congruent, allowing easy mounting on another substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two filters are provided in a filter group on a single multilayer substrate, then the filter group can be integrated into wireless communication modules, but isolation between the two filters becomes difficult to improve
Solution Approach 1:
The ground conductor layer is segmented into multiple independent ground regions corresponding to different filters. Each ground region is electrically isolated from others through disconnection portions, thereby segmenting the ground system to prevent mutual interference between adjacent filters while maintaining individual ground references.
Solution Approach 2:
Disconnection portions are introduced as intermediary elements between adjacent ground regions. These disconnection portions act as barriers that block electromagnetic coupling between filters, serving as mediators that prevent harmful interactions while allowing each filter to maintain its own ground potential.
2Stability of the object's composition
If ground conductor layers are continuous to provide stable grounding, then grounding stability is improved, but crosstalk between adjacent filters increases
Solution Approach 1:
The ground conductor layer exhibits different properties in different regions: continuous within each filter's ground region for stability, and disconnected between adjacent filter regions for isolation. This local differentiation of continuity enables simultaneous achievement of grounding stability and filter isolation.
Solution Approach 2:
The unified ground conductor layer is segmented into multiple independent ground regions, each providing stable grounding for its associated filter while being electrically isolated from other ground regions through disconnection portions, thereby eliminating mutual interference.
3Area of stationary object
If filters are arranged closely to reduce substrate area, then device compactness is improved, but isolation between filters deteriorates
Solution Approach 1:
Isolation between filters is achieved not by increasing horizontal separation distance but by introducing vertical dimensionality through disconnection portions in the ground conductor layer. This allows compact horizontal arrangement while maintaining electrical isolation through the layered structure.
Solution Approach 2:
Disconnection portions serve as intermediary barriers in the ground conductor layer that prevent electromagnetic coupling between closely spaced filters, enabling compact substrate area utilization without sacrificing filter isolation.
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3~4
AI summary
To improve isolation between a plurality of filters formed in a single multilayer substrate, in a filter group (10), a first filter and a second filter (filters 10a and 10b) formed in the multilayer substrate (11) each include a strip line constituted by a signal pattern (14a, 14b) and paired ground conductor layers (12, 13), and a first area (area 13a) and a second area (area 13b) in the ground conductor layer (13) are disconnected from each other.