XBAR Split-Ladder Filter With Coupled Sub-Resonators for Wideband RF

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Solution Overview

Problem

Current RF filters using acoustic wave resonators are not well-suited for higher frequencies and wider bandwidths required by future communication networks, particularly for 5G NR and Wi-Fi bands, due to limitations in frequency range and bandwidth capability.

Innovation Solution

The development of a split-ladder band-pass filter using transversely-excited film bulk acoustic resonators (XBARs) with a split-ladder architecture, where series and shunt resonators are fabricated on separate chips with different piezoelectric material thicknesses, allowing for optimized resonance and anti-resonance frequencies to cover the n77 frequency range from 3300 MHz to 4200 MHz, and employing a frequency setting dielectric layer to extend bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional acoustic wave resonators are used, then the filter can be manufactured with standard processes, but the frequency range and bandwidth capability are limited and not suitable for higher frequencies required by future communication networks

Engineering Contradiction:

Improvefrequency range and bandwidth capabilityVSAvoidperformance at higher frequencies

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The resonator is divided into multiple sub-resonators connected in parallel, each with different piezoelectric material thicknesses. This segmentation allows each sub-resonator to contribute to different frequency ranges, enabling the composite resonator to achieve wider bandwidth and higher frequency capability while maintaining manufacturing feasibility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the resonator use piezoelectric materials with different thicknesses to optimize local frequency responses. This local quality variation enables the resonator to handle multiple frequency bands simultaneously, improving adaptability for future communication networks requiring higher frequencies and wider bandwidths

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If a single piezoelectric material thickness is used in the resonator, then the manufacturing process is simplified, but the separation between resonance and anti-resonance frequencies is insufficient for high-performance filtering

Engineering Contradiction:

Improveseparation between resonance and anti-resonance frequenciesVSAvoidresonator structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The resonator structure is segmented into multiple sub-resonators with different piezoelectric material thicknesses. This segmentation creates distinct resonance and anti-resonance frequency points, improving the separation between these critical frequencies for high-performance filtering applications

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The resonator uses a composite structure with multiple piezoelectric material layers of different thicknesses. This composite approach enables precise control over resonance and anti-resonance frequencies while maintaining a manageable device structure through systematic design

Inventive Principle:

Principle #40Composite materials

3Speed

If the piezoelectric material thickness is increased to achieve higher resonance frequencies, then the frequency range is extended, but the bandwidth capability is reduced

Engineering Contradiction:

Improveresonance frequencyVSAvoidbandwidth capability

Core Design Contradiction:

SpeedVSAdaptability or versatility

Solution Approach 1:

The resonator is segmented into multiple sub-resonators with progressively different piezoelectric material thicknesses. This segmentation allows the system to achieve high resonance frequencies through thinner materials while the collective response of all sub-resonators provides wide bandwidth capability, resolving the trade-off between frequency and bandwidth

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 solution enables high-performance RF filters capable of handling higher frequencies and wider bandwidths, improving filter performance by providing better separation between resonance and anti-resonance frequencies, thus enhancing communication system capabilities.

Implementation Method 1

Each of the plurality of resonators comprises an interdigital transducer and a piezoelectric material

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

acoustic wave resonators including surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, film bulk acoustic wave resonators (FBAR)

Methodology Applied

Scientific EffectAcoustic resonance: Resonance

Data Source

PatentUS12255625B2Filter using transversely-excited film bulk acoustic resonators with inductively coupled sub-resonators

Publication Date: 2025.03.18 MURATA MFG CO LTD

AI summary

A filter includes first and second shunt resonators, at least one series resonator connected to the first and second shunt resonators in a ladder filter circuit, and a first ground contact pad. The first shunt resonator has two or more first sub-resonators and the second shunt resonator has two or more second sub-resonators. At least one first sub-resonator and at least one, but less than all, of the two or more second sub-resonators are connected to the first ground contact pad.