Balanced Filter Module Layout for RF Phase Balance

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Solution Overview

Problem

Existing filter modules for communication devices, such as cellular phones, face challenges in maintaining excellent phase balance characteristics as the number of interstage filters and wave splitters increases, leading to deteriorated phase balance of reception signals.

Innovation Solution

A filter module design featuring a mount board with a specific stacking configuration of electrode and dielectric layers, including balanced terminals and internal ground electrodes, where the signal path lengths and opposing areas between mount and internal electrodes are differentiated to enhance phase balance, utilizing surface acoustic wave filters with balanced-unbalanced transforming functions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple interstage filters or wave splitters are mounted on an RF circuit to support multiple bands and systems, then the communication service capability is improved, but the phase balance characteristics of reception signals deteriorate

Engineering Contradiction:

Improvecommunication service capabilityVSAvoidphase balance characteristics

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies asymmetry by making the opposing areas between the first balanced mount electrode and first internal ground electrode different from those between the second balanced mount electrode and first internal ground electrode. This asymmetric configuration compensates for phase imbalances introduced by multiple filters, maintaining excellent phase balance characteristics while supporting multiple communication bands and systems.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by differentiating the signal path lengths and opposing areas at specific locations within the mount board. The first and second balanced mount electrodes have different opposing areas against the first internal ground electrode, creating localized electrical characteristics that balance the overall phase response across multiple frequency bands.

Inventive Principle:

Principle #3Local quality

2Reliability

If the number of interstage filters or wave splitters is increased to handle larger communication quality improvements, then the communication quality is improved, but the phase balance of reception signals becomes deteriorated

Engineering Contradiction:

Improvecommunication qualityVSAvoidphase balance of reception signals

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The asymmetric design of the balanced mount electrodes with different opposing areas compensates for the cumulative phase effects of multiple filters, maintaining reliable communication quality while preserving phase balance characteristics.

Inventive Principle:

Principle #4Asymmetry

3Ease of manufacture

If a balanced filter module is designed with equal opposing areas between balanced mount electrodes and internal ground electrodes, then the manufacturing is simplified, but the phase balance characteristics deteriorate

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidphase balance characteristics

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent deliberately introduces asymmetry in the opposing areas between balanced mount electrodes and internal ground electrodes. This asymmetric configuration is designed to compensate for phase imbalances, achieving excellent phase balance characteristics while remaining manufacturable through standard PCB fabrication processes.

Inventive Principle:

Principle #4Asymmetry

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

The design significantly improves phase balance characteristics and differential isolation, ensuring consistent signal performance across multiple frequency bands.

Implementation Method 1

a reception filter of the first duplexer 102 is constituted by a longitudinally coupled resonator-type surface acoustic wave filter

Methodology Applied

Scientific EffectSurface acoustic wave: Surface Acoustic Wave

Data Source

PatentUS8872602B2Filter module

Publication Date: 2014.10.28 MURATA MFG CO LTD

AI summary

In a filter module having excellent phase balance characteristics, a length of a signal path between a first balanced mount electrode and a first balanced terminal electrode is different from a length of a signal path between a second balanced mount electrode and a second balanced terminal electrode. When viewing a mount board from a side on which a filter component is mounted, an area along which the first balanced mount electrode and a first internal ground electrode oppose each other is different from an area along which the second balanced mount electrode and the first internal ground electrode oppose each other.