RF Front-End Multiplexer Layout for Overlapping Band Leakage

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Solution Overview

Problem

Existing radio frequency front-end circuits face challenges in maintaining satisfactory attenuation and bandpass characteristics when operating in multiband mode, particularly during carrier aggregation, due to signal leakage across filters with overlapping pass bands, leading to degradation of attenuation and bandpass characteristics.

Innovation Solution

The implementation of a radio frequency front-end circuit with a multiplexer configuration that includes a plurality of filters with different pass bands, where a first acoustic wave filter and a second acoustic wave filter are connected through a switch, with serial arm resonators positioned closest to the switch, ensuring capacitive impedance at frequencies outside the pass band, thereby enhancing reflection coefficients and maintaining improved attenuation and bandpass characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple filters with overlapping pass bands are used in a multiplexer configuration, then the circuit can operate in multiband mode and carrier aggregation, but signal leakage occurs between filters causing degradation of attenuation and bandpass characteristics

Engineering Contradiction:

Improvemultiband operation capabilityVSAvoidattenuation and bandpass characteristics

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies local quality by configuring specific resonators (serial arm resonators) at particular locations within the filter circuits, specifically closest to the switch on both input and output sides. This localized configuration creates capacitive impedance at frequencies outside the pass band, providing targeted improvement in attenuation characteristics without affecting the overall multiband operation capability of the multiplexer.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If filters are connected through a switch in a multiplexer, then signal routing between different bands is enabled, but signal leakage increases and attenuation characteristics deteriorate

Engineering Contradiction:

Improvesignal routing flexibilityVSAvoidsignal leakage

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent implements preliminary anti-action by pre-configuring serial arm resonators in specific positions within the filter circuits before signal transmission occurs. These resonators create capacitive impedance that proactively counteracts signal leakage at frequencies outside the pass band, preventing energy loss through the switch and into adjacent filters before the leakage can occur.

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If serial arm resonators are positioned closest to the switch, then capacitive impedance is maintained at frequencies outside the pass band, but the circuit complexity increases

Engineering Contradiction:

Improveattenuation characteristicsVSAvoidfilter configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the filter circuit into distinct functional sections with specific resonators positioned at critical locations. The serial arm resonators are segmented and placed specifically closest to the switch on both input and output sides, creating modular units that can be independently optimized. This segmentation maintains clear functional boundaries while achieving the desired capacitive impedance characteristics.

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 configuration significantly improves attenuation and bandpass characteristics by reducing signal leakage and maintaining capacitive impedance, even in non-connected states, allowing for effective operation across multiple frequency bands without degrading overall performance.

Implementation Method 1

a first acoustic wave resonator of one or more acoustic wave resonators defining the first acoustic wave filter is a serial arm resonator and is located closest to the switch among the one or more acoustic wave resonators defining the first acoustic wave filter

Methodology Applied

Scientific EffectCapacitive impedance: Capacitance

Implementation Method 2

acoustic wave filter

Methodology Applied

Scientific EffectAcoustic wave resonance: Resonance

Data Source

PatentUS10547288B2Radio frequency front-end circuit and communication device

Publication Date: 2020.01.28 MURATA MFG CO LTD

AI summary

A radio frequency front-end circuit includes a multiplexer including filters with different pass bands and including a first acoustic wave filter and a first terminal of each of the filters being connected in common, a second acoustic wave filter including a pass band within the pass band of the first acoustic wave filter, and a switch including a common terminal connected to a second terminal of the first acoustic wave filter and selective terminals including a selective terminal connected to the second acoustic wave filter. Each of an acoustic wave resonator of the first acoustic wave filter located closest to the switch and an acoustic wave resonator of the second acoustic wave filter located closest to the switch, is a serial arm resonator.