Multilayer Multiplexer Ground Segmentation for Cross-Isolation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In multiplexers with multiple frequency bands, increased filter connections lead to high-frequency signal leakage and interference, degrading cross-isolation and reception sensitivity due to common grounding of resonators, which enhances coupling between filters.

Innovation Solution

A multiplexer design with a multilayer substrate where parallel-arm resonators are surface-mounted and grounded on specific dielectric layers, isolating certain terminals from each other to prevent cross-talk while maintaining attenuation characteristics, using a configuration that includes series and parallel-arm resonators and inductors to adjust frequency and attenuation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If all parallel-arm resonators are commonly connected to a ground pattern on a die-attach layer, then attenuation characteristics of the reception filter are improved, but coupling between filters via the ground layer is strengthened causing signal leakage and degraded cross-isolation

Engineering Contradiction:

Improveattenuation characteristicsVSAvoidsignal leakage and interference

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The ground connection is segmented by separating the connection points of first and second parallel-arm resonators on the die-attach layer. Instead of using a single common ground pattern, the invention divides the ground connection into multiple independent segments, which reduces the coupling between filters while maintaining individual attenuation characteristics of each resonator.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If the number of filters connected to the antenna terminal is increased to support multiple frequency bands, then multiband support capability is improved, but leakage and interference of high-frequency signals easily occur between transmission and reception paths

Engineering Contradiction:

Improvemultiband support capabilityVSAvoidsignal leakage and interference

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The invention applies segmentation to the ground connection structure, dividing it into multiple independent connection points for different resonators. This allows multiple filters to be connected to the antenna terminal for multiband support while preventing signal leakage between transmission and reception paths through the ground layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention implements local quality by providing different ground connection configurations for different resonators based on their specific frequency bands and signal paths. Each resonator's ground connection is optimized independently, allowing multiband support while maintaining proper isolation between different frequency paths.

Inventive Principle:

Principle #3Local quality

3Reliability

If all resonators are grounded on a ground layer closer to the filter chip, then attenuation characteristics are improved, but cross-isolation between transmission filter and reception filter is degraded

Engineering Contradiction:

Improveattenuation characteristicsVSAvoidcross-isolation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention segments the ground connection so that first and second parallel-arm resonators have separate ground connection points on the die-attach layer. This segmentation maintains the close grounding needed for good attenuation characteristics while preventing the coupling that would degrade cross-isolation between transmission and reception filters.

Inventive Principle:

Principle #1Segmentation

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 design improves cross-isolation between filters while ensuring the attenuation characteristics of each filter, reducing high-frequency signal leakage and enhancing reception sensitivity by isolating parallel-arm terminals on specific dielectric layers.

Implementation Method 1

The first parallel-arm terminal and the fourth parallel-arm terminal are isolated from each other on the dielectric layers from the first main surface to an n-th dielectric layer of the multilayer substrate

Methodology Applied

Scientific EffectElectromagnetic isolation:

Data Source

PatentUS11545961B2Multiplexer and communication apparatus

Publication Date: 2023.01.03 MURATA MFG CO LTD

AI summary

A multiplexer includes a first transmission filter connected to a common terminal, a reception filter, a second transmission filter, and a multilayer substrate. The first transmission filter includes a first parallel-arm resonator connected to a first parallel-arm terminal and a second parallel-arm resonator connected to a second parallel-arm terminal. The second transmission filter includes a third parallel-arm resonator connected to a third parallel-arm terminal and a fourth parallel-arm resonator connected to a fourth parallel-arm terminal. The first to fourth parallel-arm resonators are surface-mounted on a main surface of the multilayer substrate. The second and third parallel-arm terminals are grounded on any dielectric layer from the main surface to an n-th dielectric layer of the multilayer substrate and the first and fourth parallel-arm terminals are isolated from each other on the dielectric layers from the main surface to the n-th dielectric layer.