Surface Acoustic Wave Filter Using High-Order Modes for Higher Frequencies
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Solution Overview
Problem
Current surface acoustic wave devices are limited in supporting higher frequencies due to constraints in electric power resistance and manufacturing technologies, which restrict the reduction of wavelength provided by interdigital transducer electrodes, hindering their use in congested frequency bands such as those used by smartphones and emerging 5G and future wireless communication systems.
Innovation Solution
The development of a surface acoustic wave device with a piezoelectric substrate and an interdigital transducer electrode that supports a high-order mode with a wavelength A and phase velocity greater than 8,000 m/s, utilizing LiNbO3 crystal with specific Euler angles and electrodes made from materials like copper, aluminum, or platinum, and an overcoat layer of silicon dioxide to enhance temperature coefficient of frequency properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the wavelength of the interdigital transducer electrode is reduced to support higher frequencies, then the frequency support capability is improved, but the manufacturing precision and electric power resistance deteriorate due to current technology constraints
Solution Approach 1:
The patent changes the fundamental parameter of surface acoustic wave propagation by utilizing higher-order modes (particularly third-order modes) instead of the conventional fundamental mode. This mode transition enables phase velocities exceeding 8,000 m/s (compared to typical fundamental mode velocities), allowing the device to support higher frequencies without requiring proportional reduction in electrode wavelength, thereby avoiding the manufacturing precision constraints that would otherwise limit frequency support.
2Speed
If the wavelength of the interdigital transducer electrode is reduced to support higher frequencies, then the frequency support capability is improved, but the electric power resistance deteriorates due to current technology constraints
Solution Approach 1:
By transitioning to higher-order modes with phase velocities greater than 8,000 m/s, the patent alters the operational parameters of the surface acoustic wave device. This parameter change allows the maintenance of longer electrode wavelengths at higher frequencies, which in turn preserves electric power resistance characteristics that would otherwise deteriorate with wavelength reduction in conventional fundamental mode operation.
3Speed
If a higher-order mode with phase velocity greater than 8,000 m/s is supported, then the frequency support capability is improved, but the device complexity increases due to specific crystal orientation and material requirements
Solution Approach 1:
The patent specifies particular local qualities for the piezoelectric substrate, namely LiNbO3 crystal with Euler angles within defined ranges (θ: 100-140 degrees, φ: -45 to 45 degrees, ψ: -45 to 45 degrees). This localized specification of crystal orientation enables the generation and support of higher-order modes with phase velocities exceeding 8,000 m/s. While this introduces specific material requirements, the effect is confined to the substrate level rather than requiring complex device architecture, thus managing the trade-off between performance improvement and device complexity.
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 enables the generation of third-order modes with phase velocities of at least 9,000 m/s, effectively supporting higher frequency applications and improving filtering capabilities in radio-frequency devices, thereby addressing the limitations of existing technologies in handling congested frequency bands.
Implementation Method 1
an interdigital transducer electrode embedded in a surface of the piezoelectric substrate to support a high-order mode of a surface acoustic wave having a wavelength A and a phase velocity greater than 8,000 m/s
Implementation Method 2
a piezoelectric substrate and an interdigital transducer electrode embedded in a surface of the piezoelectric substrate
Implementation Method 3
a layer implemented over the piezoelectric substrate and the interdigital transducer electrode, and such a layer can be configured to provide improved temperature coefficient of frequency property of the surface acoustic wave device
Data Source
AI summary
In some embodiments, a surface acoustic wave device can include a piezoelectric substrate and an interdigital transducer electrode embedded in a surface of the piezoelectric substrate to support a high-order mode of a surface acoustic wave having a wavelength λ and a phase velocity greater than 8,000 m/s. Such a high-order mode can include a third-order mode, and the phase velocity can be at least 9,000 m/s. In some embodiments, such a surface acoustic wave device can be implemented in products such as a radio-frequency filter, a radio-frequency module and a wireless device.