Lithium Tantalate Acoustic Wave Structure for Wider RF Bandwidth
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Solution Overview
Problem
Existing acoustic wave devices for RF communication systems face challenges in achieving high quality factor, low loss, wide bandwidth, and favorable temperature coefficient of frequency due to undesired oscillations or vibrations known as spurious modes.
Innovation Solution
The use of lithium tantalate with a specific crystalline orientation defined by (YXl)Θ°, where Θ is between 10° and 37°, in conjunction with a transducer and a substrate, to enhance the electromechanical coupling coefficient and thereby increase bandwidth and improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional piezoelectric materials and configurations are used in acoustic wave devices, then the devices can operate with basic functionality, but the electromechanical coupling coefficient remains limited, resulting in narrow bandwidth
Solution Approach 1:
The patent applies parameter changes by optimizing the crystalline orientation of lithium tantalate to specific angle ranges (ΥXl: 30°-45°, ZXl: 60°-75°) to maximize the electromechanical coupling coefficient. This precise parameter optimization enables enhanced bandwidth while maintaining stable material properties, resolving the contradiction between stability and adaptability.
Solution Approach 2:
The patent employs composite material structures by combining lithium tantalate piezoelectric layer with specific substrate materials and electrode configurations. This composite approach enables simultaneous achievement of high electromechanical coupling coefficient and wide bandwidth by leveraging the complementary properties of different materials in the acoustic wave device structure.
2Productivity
If acoustic wave devices operate at higher frequencies with conventional materials, then communication throughput improves, but spurious modes increase causing degradation of quality factor and increasing loss
Solution Approach 1:
The patent applies local quality by implementing specific crystalline orientation configurations in different regions of the lithium tantalate layer. The ΥXl and ZXl angle ranges are optimized to suppress spurious modes in specific frequency ranges while maintaining high quality factor, enabling high throughput communication without the detrimental effects of unwanted oscillations.
Solution Approach 2:
The patent converts the potentially harmful spurious modes into beneficial effects by carefully selecting crystalline orientations that suppress unwanted vibrations while enhancing the desired acoustic wave propagation. This transforms what would be degradation factors into performance-enhancing characteristics, maintaining high quality factor at elevated frequencies.
3Stability of the object's composition
If the thickness of the piezoelectric layer is increased to enhance coupling, then electromechanical coupling coefficient improves, but the device becomes more complex and harder to manufacture with precise control
Solution Approach 1:
The patent resolves the manufacturing precision challenge by identifying optimal crystalline orientation parameter ranges (ΥXl: 30°-45°, ZXl: 60°-75°) that maximize electromechanical coupling without requiring extreme layer thicknesses. This parameter optimization allows achieving high coupling coefficients with manufacturable thickness tolerances, balancing performance with manufacturing feasibility.
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 increases the electromechanical coupling coefficient, leading to improved bandwidth and performance of guided acoustic wave devices, while reducing spurious modes.
Implementation Method 1
Piezoelectric materials acquire a charge when compressed, twisted, or distorted, and similarly compress, twist, or distort when a charge is applied to them. Accordingly, when an alternating electrical signal is applied to the one or more electrodes in contact with the piezoelectric material, a corresponding mechanical signal (i.e., an oscillation or vibration) is transduced therein.
Implementation Method 2
Exemplary acoustic wave devices include surface acoustic wave (SAW) resonators and bulk acoustic wave (BAW) resonators
Data Source
AI summary
A guided acoustic wave device includes a substrate, a lithium tantalate layer on the substrate, and a transducer on the lithium tantalate film. The lithium tantalate has a crystalline orientation defined by (YXl)Θ°, where Θ is between 10° and 37°. The inventors discovered that limiting the crystalline orientation of the lithium tantalate in this manner provides significant increases in the electromechanical coupling coefficient of the acoustic wave device, thereby increasing bandwidth and improving performance.