Shear Mode Acoustic Resonator Structure for High-Q 3 GHz RF
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Solution Overview
Problem
Existing radio frequency acoustic resonators face limitations in extending their operating range to higher frequencies above 3 GHz while maintaining high electromechanical coupling coefficients and Q values, which is required for new communication standards like 5G.
Innovation Solution
A laterally excited shear mode acoustic resonator is designed with a piezoelectric layer made of monocrystalline lithium niobate or lithium tantalate, an acoustic mirror with alternating low and high acoustic impedance reflection layers, and a lateral reflector to generate a shear mode mechanical wave, enabling high electromechanical coupling and Q values at frequencies above 3 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic resonators are used, then they can operate at lower frequencies with acceptable Q values, but they cannot maintain high electromechanical coupling coefficients and high Q values when extending operating range to frequencies above 3 GHz
Solution Approach 1:
The patent changes the operating mode from longitudinal to shear mode and uses laterally propagating acoustic waves instead of vertically propagating waves. This parameter change in the acoustic wave mode enables the resonator to achieve high electromechanical coupling coefficients and high Q values at frequencies above 3 GHz, resolving the contradiction between operating frequency and performance maintenance
Solution Approach 2:
The patent employs a composite structure consisting of a piezoelectric layer (lithium niobate or lithium tantalate) on top of an acoustic mirror with alternating high and low acoustic impedance layers. This composite material structure enables the resonator to maintain high electromechanical coupling and Q values at higher frequencies by combining the advantages of different materials with complementary properties
2Ease of manufacture
If the resonator structure is simplified, then manufacturing becomes easier, but the ability to achieve high Q values and high electromechanical coupling at frequencies above 3 GHz is compromised
Solution Approach 1:
The patent segments the resonator into distinct functional layers: a piezoelectric layer and an acoustic mirror with alternating high and low acoustic impedance layers. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall performance, enabling high Q values and electromechanical coupling without excessive manufacturing complexity
Solution Approach 2:
The patent applies local quality by using different materials with specific acoustic impedance properties at different locations within the acoustic mirror. The alternating high and low acoustic impedance layers are strategically positioned to create effective acoustic reflection, achieving high Q values through localized material properties rather than uniform structure throughout
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 resonator achieves high electromechanical coupling coefficients and Q values above 3 GHz, supporting the synthesis of high-performance passband filters necessary for 5G communication standards and future updates.
Implementation Method 1
a piezoelectric layer disposed on the acoustic mirror and including monocrystalline lithium niobate and/or monocrystalline lithium tantalate; an electrode unit disposed on the piezoelectric layer and configured to form an electric field
Implementation Method 2
an acoustic mirror including at least one first acoustic reflection layer and at least one second acoustic reflection layer, acoustic impedance of each first acoustic reflection layer being less than that of each second acoustic reflection layer
Implementation Method 3
a lateral reflector disposed on the piezoelectric layer and configured to laterally reflect a sound wave
Implementation Method 4
A laterally excited shear mode acoustic resonator is designed with a piezoelectric layer made of monocrystalline lithium niobate or lithium tantalate, an acoustic mirror with alternating low and high acoustic impedance reflection layers, and a lateral reflector to generate a shear mode mechanical wave, enabling high electromechanical coupling and Q values at frequencies above 3 GHz
Data Source
AI summary
Provided is an acoustic resonator in a transverse excitation shear mode. The acoustic resonator comprises: an acoustic mirror (120), which comprises at least one first acoustic reflecting layer (121, 123, 125) and at least one second acoustic reflecting layer (122, 124), wherein the acoustic impedance of each first acoustic reflecting layer is less than that of each second acoustic reflecting layer; a piezoelectric layer (130), which is arranged on the acoustic mirror, and which comprises lithium niobate of a single crystal material and/or lithium tantalate of a single crystal material; electrode units (142, 143, 144), which are arranged on the piezoelectric layer (130) and are used for forming an electric field; and transverse reflectors (152, 154), which are arranged on the piezoelectric layer, are used for transversely reflecting acoustic waves, and can have a high electromechanical coupling coefficient and a high Q value at a frequency greater than 3 GHz.