Acoustic Mirror Wave Structure for Higher-Frequency Guided Waves
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices face limitations in miniaturization and frequency range, particularly surface acoustic wave devices which are difficult to miniaturize beyond 1-3 GHz due to lithography and electric loss constraints, and bulk acoustic wave devices are challenging to design for high frequencies.
Innovation Solution
An acoustic wave device featuring a piezoelectric layer on an omnidirectional acoustic mirror with interdigital conductive comb excitation/reception means, utilizing a stacking of alternated high and low acoustic impedance layers to propagate guided waves at higher speeds, allowing operation beyond conventional surface and bulk acoustic wave frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the pitch of interdigital combs is reduced to increase operating frequency, then the operating frequency is improved, but the manufacturing precision and electric loss worsen
Solution Approach 1:
The patent transitions from surface acoustic wave propagation to bulk acoustic wave propagation by introducing a piezoelectric layer with thickness comparable to the acoustic wavelength. This dimensional change allows frequency increase without further comb pitch reduction, as the frequency is now determined by the layer thickness rather than the comb geometry.
Solution Approach 2:
The patent changes the fundamental parameter determining acoustic wave frequency from comb pitch (surface wave regime) to piezoelectric layer thickness (bulk wave regime). This parameter transformation enables frequency scaling without proportionally reducing comb dimensions, thereby avoiding lithography and electric loss limitations.
2Speed
If the pitch of interdigital combs is reduced to increase operating frequency, then the operating frequency is improved, but the electric loss increases
Solution Approach 1:
By moving from surface wave to bulk wave propagation through the introduction of a piezoelectric layer, the system achieves higher frequencies without the need for extremely fine comb pitches. This dimensional transition maintains larger, less lossy comb structures while achieving the desired frequency increase.
3Speed
If bulk acoustic wave devices are used to operate at frequencies greater than 3 GHz, then the operating frequency is improved, but the device complexity increases
Solution Approach 1:
The device is segmented into distinct functional layers: a piezoelectric layer for bulk wave generation, an acoustic mirror structure for wave confinement, and interdigital combs for excitation. This segmentation simplifies the design by separating the frequency-determining bulk wave mechanism from the excitation mechanism, making high-frequency operation more achievable than in monolithic bulk wave devices.
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
Enables propagation of acoustic waves at significantly higher speeds, enabling operation at frequencies up to six times higher than conventional devices without modifying comb tooth pitch, with propagation losses and coupling coefficients comparable to surface wave devices.
Implementation Method 1
If a time-variable or A.C. signal is applied between combs 2 and 3, this signal is turned by piezoelectric effect into a surface acoustic wave which propagates in substrate 1
Implementation Method 2
an omnidirectional acoustic mirror and excitation and/or reception means on a surface of said piezoelectric layer, capable of exciting waves in a band gap of the acoustic mirror
Data Source
AI summary
An acoustic wave device comprising a piezoelectric layer on an omnidirectional acoustic mirror and excitation and/or reception means on a surface of said piezoelectric layer, capable of exciting waves in a band gap of the acoustic mirror.