RF Module 3D Filter Stacking for Signal Isolation
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Solution Overview
Problem
In radio-frequency modules, the proximity of transmit and receive filters on the same major surface leads to increased signal communication loss due to interconnect resistance and phase shifts, and worsens isolation between transmission and reception signals.
Innovation Solution
The radio-frequency module is designed with a mounting board having opposite major surfaces, where the transmit filter is mounted on one surface and the receive filter on the other, allowing their footprints to overlap in plan view, thereby shortening interconnection lengths and improving isolation by interposing the board between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the transmit filter and receive filter are mounted on the identical major surface of the wiring board, then the module size can be reduced, but the signal communication loss increases due to long interconnection length
Solution Approach 1:
The patent transitions from a two-dimensional layout (both filters on the same surface) to a three-dimensional arrangement (filters on opposite surfaces of the wiring board). This vertical stacking approach reduces the planar footprint while shortening the electrical interconnection paths between the filters and common terminal, thereby simultaneously achieving miniaturization and reduced signal loss.
2Loss of energy
If the transmit filter and receive filter are mounted on the identical major surface with short interconnection length, then signal communication loss is reduced, but the isolation between transmit and receive signals deteriorates
Solution Approach 1:
By mounting the transmit filter on one major surface and the receive filter on the opposite major surface of the wiring board, the patent utilizes the third dimension (vertical spacing) to physically separate the filters. This spatial separation through the board thickness provides electromagnetic isolation between transmit and receive signals while maintaining short interconnection lengths for reduced signal loss.
3Area of stationary object
If the transmit filter and receive filter are positioned in close proximity on the same surface, then the module area is reduced, but the isolation between transmission and reception worsens
Solution Approach 1:
The patent resolves the area-isolation contradiction by moving the filters from a close-proximity two-dimensional arrangement to a vertically-separated three-dimensional arrangement. The filters are positioned on opposite surfaces of the wiring board with their footprints overlapping in plan view, achieving compact area utilization while the board thickness provides natural electromagnetic isolation between the transmit and receive paths.
Data Source
AI summary
A radio-frequency module includes a mounting board having first and second major surfaces opposite to each other and a duplexer including a transmit filter coupled to a node and a receive filter coupled to the node. The transmit filter is mounted on the first major surface, and the receive filter is mounted on the second major surface. When the mounting board is viewed in a plan view, a footprint of the transmit filter at least partially overlaps a footprint of the receive filter.