Abstract
The development of mobile communication sets higher demands on high frequency surface acoustic wave (SAW) devices. The layout of interdigital transducers (IDT) in SAW devices is in plane and the traditional methods of improving frequency for SAW devices are the increase of acoustic velocity and the reduction of wavelength. However, these methods have a limit due to the limited acoustic velocity and the photolithography limit. This work proposes a new way for the development of high frequency SAW devices by redesigning the layout of IDT in three dimensions (3D). The set of IDTs is split into two layers, i.e. the ground electrodes on one layer and the signal electrodes on the other layer. This 3D layout of IDTs dramatically narrows the horizontal gap between two adjacent electrodes, which can significantly increase the frequency. The frequency and the electromechanical coupling factor (K 2 ) of the four structures of SAW devices with the 3D layout of IDTs were studied by the finite element method (FEM). The results show that the frequency can be doubled under the same critical resolution of lithography due to the shortening of wavelength, and the 3D layout of IDTs is available for SAW devices based on piezoelectric thin film or piezoelectric single crystal. This work develops a new alternative to increase the working frequency of SAW devices.
Highlights
Surface acoustic wave (SAW) devices have been widely used in the field of communication system, microfluidic and sensor. [1]–[7] With the rapid development of mobile communication technology, especially the emergency of the 5th generation (5G) wireless system has promoted the frequency range into Sub-6 and even millimeter Wave, which demands a large number of high frequency filters and duplexers
In conclusion, a 3D layout of interdigital transducers (IDT) for the development of high frequency SAW devices is presented by splitting a set of IDTs into two layers, i.e. the ground electrodes on one layer and the signal electrodes on the other layer
The first two of which are based on piezoelectric thin film and the last two of which are based on piezoelectric single crystal, are designed to identify the application range of the 3D layout of IDTs
Summary
Surface acoustic wave (SAW) devices have been widely used in the field of communication system, microfluidic and sensor. [1]–[7] With the rapid development of mobile communication technology, especially the emergency of the 5th generation (5G) wireless system has promoted the frequency range into Sub-6 and even millimeter Wave, which demands a large number of high frequency filters and duplexers. Since the layout of IDT in SAW devices is in plane, the period of IDT cannot be prepared into a very small level because of the photolithography limit, the preparation cost and the power durability. This stimulates us to explore a new solution to increase SAW devices frequency. The IDTs are separated into two layers, i.e. the ground electrodes on one layer and the signal electrodes on the other layer, and the gap between electrodes in either part of IDTs can be much smaller, which narrows the wavelength significantly The devices with this 3D layout of IDTs have much higher frequencies under the same critical resolution of lithography
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