Stacked RF Filter Layout for Lower Inductive Coupling
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Solution Overview
Problem
Radio frequency modules experience deterioration in filter characteristics due to inductive coupling between the mounting board and resonators, leading to attenuated signal quality.
Innovation Solution
The design incorporates a mounting board with specific conductor and ground portions, featuring series and parallel arm resonators, and through-via conductors to reduce inductive coupling by optimizing the placement and connection of resonators and wiring, ensuring the series arm resonator is closest to the input/output terminal and the parallel arm resonator is connected between the signal path and ground, with a shorter distance between through-via conductors to minimize loop area and magnetic field generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the series arm resonator is placed closest to the input/output terminal and the parallel arm resonator is connected between the signal path and ground, then inductive coupling between the mounting board and resonators is reduced, but the filter characteristics may still deteriorate due to parasitic capacitance variations and loop area
Solution Approach 1:
The patent transitions from a planar arrangement to a three-dimensional stacked configuration where resonators are arranged vertically across multiple layers. The series arm resonator is placed on the first substrate and the parallel arm resonator on the second substrate, with through-via conductors connecting them. This spatial reconfiguration reduces parasitic capacitance between resonators and minimizes loop area, thereby reducing inductive coupling and improving filter characteristics.
Solution Approach 2:
The patent introduces through-via conductors as intermediary elements that connect the series arm resonator on the first substrate to the parallel arm resonator on the second substrate. These through-via conductors serve as controlled impedance transmission lines that mediate the electrical connection while minimizing parasitic effects. The mounting board with ground conductor portions also acts as an intermediary to provide stable grounding and reduce inductive coupling between the resonators and the mounting board.
2Object-affected harmful factors
If through-via conductors are used to connect resonators across substrates, then inductive coupling is reduced by minimizing loop area, but the device complexity increases due to multiple substrates and connection components
Solution Approach 1:
The patent combines multiple functions into integrated components. The mounting board integrates ground conductor portions that serve both as electrical ground connections and as shielding structures to reduce inductive coupling. The through-via conductors are integrated directly into the substrate structure rather than being separate components, reducing assembly complexity. The series and parallel arm resonators are positioned to overlap in the vertical direction, allowing them to share the same mounting board and reducing the overall device footprint.
3Measurement precision
If the parallel arm resonator is connected between the signal path and ground conductor portion, then the filter's frequency selectivity is improved, but parasitic capacitance variations occur due to the connection path
Solution Approach 1:
The patent applies different structural configurations to different parts of the filter circuit. The series arm resonator is connected in series with the signal path with minimal grounding connections, while the parallel arm resonator is connected between the signal path and ground through controlled impedance paths. The through-via conductors providing ground connections are strategically positioned to minimize parasitic capacitance. This localized optimization of connection methods for different resonator types maintains frequency selectivity while reducing parasitic effects.
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
This configuration effectively reduces inductive coupling, preventing deterioration in filter characteristics and maintaining signal quality by minimizing parasitic capacitance variations and loop area, thereby enhancing the radio frequency module's performance.
Implementation Method 1
the characteristics of a filter may be deteriorated due to an occurrence of inductive coupling between a path between a mounting board and a series arm resonator of the filter and a path between a parallel arm resonator of the filter and the mounting board
Data Source
AI summary
In a filter of a radio frequency module, a first chip is provided on a mounting board, and a second chip is provided on the first chip. The first and second chips respectively include first and second resonators. The first and second resonators face each other in a thickness direction of the mounting board. The first chip includes first and second through-via conductors, and first and second wiring portions. The first through-via conductor is interposed between a first terminal and a first connection conductor portion. A distance between the second through-via conductor and the first through-via conductor is shorter than a distance between the first wiring portion and the first through-via conductor.