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CN-122001335-A - Electroacoustic transducer and TF-SAW device

CN122001335ACN 122001335 ACN122001335 ACN 122001335ACN-122001335-A

Abstract

The invention discloses an electroacoustic transducer and a TF-SAW device, and belongs to the technical field of radio frequency filtering. The electroacoustic transducer comprises interdigital electrodes formed by a plurality of groups of electrode fingers which are arranged in a staggered mode, and a multistage bus bar structure which is arranged at two ends of the interdigital electrodes and is formed by a secondary bus bar, a primary bus bar and bus bar connecting fingers for connecting the secondary bus bar and the primary bus bar, wherein an electrode finger mass increasing part is arranged in a low sound speed area of the interdigital electrodes. The invention optimizes the size ratio of the multi-stage bus bar structure and the bus bar connecting fingers when the dummy fingers are not configured by optimizing the secondary bus bar length D, the dummy finger average length gamma and the number ratio of the dummy finger length larger than the average value. The invention also discloses a TF-SAW device containing the electroacoustic transducer, and the optimal matching relation between the electroacoustic transducers with different structures and the corresponding piezoelectric substrates is defined. According to the invention, through structural parameter optimization, the transverse mode can be effectively inhibited, and the frequency response stability and the filtering performance of the device are improved.

Inventors

  • WANG WEIBIAO
  • HAN LU
  • FU SULEI
  • YU ZHENYI
  • LIU PING

Assignees

  • 无锡市好达电子股份有限公司

Dates

Publication Date
20260508
Application Date
20251229

Claims (10)

  1. 1. An electroacoustic transducer is characterized by comprising a plurality of groups of interdigital electrodes formed by staggered arrangement of electrode fingers, wherein multi-stage bus bars are arranged at two ends of each interdigital electrode, each multi-stage bus bar comprises a secondary bus bar and a primary bus bar which are connected through bus bar connecting fingers, each interdigital electrode comprises a low sound velocity zone, each low sound velocity zone is provided with an electrode finger mass increasing part, When the electroacoustic transducer is provided with a prosthesis, the length beta of the prosthesis is not constant, The length D of the secondary bus bar satisfies 0.3 x λ≤d≤0.5 x λ; the average length gamma of the false finger meets the condition that gamma is more than or equal to 0.4 x lambda; The ratio of the number of the length of the false finger larger than the average length gamma to the total number of the false fingers is more than or equal to 30 percent, wherein lambda is the sound wave wavelength determined by the electroacoustic transducer.
  2. 2. The electroacoustic transducer according to claim 1 wherein the length G of the busbar connection finger when provided with a dummy finger satisfies 0.4 x λ≤g≤0.9 x λ.
  3. 3. The electroacoustic transducer of claim 1 wherein the standard deviation of the length β of the prosthesis in the discrete profile is 1% or less.
  4. 4. The electroacoustic transducer of claim 1 wherein when the electroacoustic transducer is not provided with a dummy finger, the distance from the electrode finger tip to the opposite side of the secondary bus bar is H, and the ratio of the length D of the secondary bus bar to the length D of the secondary bus bar satisfies D/H of 1 to 1.5.
  5. 5. The electroacoustic transducer of claim 4 wherein the bus bar connection finger length G meets G/H of 3.2 to 3.8.
  6. 6. The electroacoustic transducer according to claim 5, wherein the bus bar connection fingers have a width W and the adjacent two bus bar connection fingers have a pitch L, and the bus bar connection finger metallization ratio W/(w+l) satisfies 0.2 to 0.5.
  7. 7. The electroacoustic transducer according to claim 1 wherein the electrode fingers include a first electrode finger and a second electrode finger which are intersected with each other in a sound wave propagation direction in a region where the region edge is set to a low sound velocity region and the rest is a standard sound velocity region, between the region edge and the secondary bus bar and between the secondary bus bar and the primary bus bar is a high sound velocity region, and the secondary bus bar and the primary bus bar are low sound velocity regions, and sound velocities of elastic waves propagated in the standard sound velocity region are between those of elastic waves propagated in the low sound velocity region and the high sound velocity region.
  8. 8. A TF-SAW device comprising a piezoelectric substrate; a conductive material film pattern disposed on the piezoelectric substrate working surface; Wherein the conductive material film pattern is formed with at least one electroacoustic transducer as claimed in any one of claims 1 to 7.
  9. 9. The TF-SAW device according to claim 8, characterized in that said piezoelectric base comprises a piezoelectric layer, a low acoustic velocity layer, a trapping material layer, a substrate when said electroacoustic transducer is not provided with said artificial finger.
  10. 10. The TF-SAW device according to claim 8, characterized in that when the electroacoustic transducer is provided with the artificial finger, the piezoelectric base comprises a piezoelectric layer, a low acoustic velocity layer, a substrate.

Description

Electroacoustic transducer and TF-SAW device Technical Field The invention relates to the technical field of radio frequency filtering, in particular to an electroacoustic transducer and a TF-SAW device. Background In recent years, with the wide application of Surface Acoustic Wave (SAW) devices in the fields of communication systems, sensors, radio frequency front end modules and the like, performance requirements of the SAW devices are continuously improved, and in particular, the SAW devices are in the aspects of operating frequency, bandwidth, out-of-band suppression, insertion loss, temperature stability and the like. Film surface acoustic wave (TF-SAW) devices are important surface acoustic wave devices, and have become key components in high-end applications such as 5G communication, internet of things and vehicle-mounted radar because of the advantages of high frequency, high Q value, low loss, easiness in integration with semiconductor processes and the like. However, TF-SAW devices still face a series of technical challenges in practical applications, especially in terms of lateral mode (transverse mode) suppression. The transverse mode refers to non-main mode vibration caused by diffraction of sound waves in the propagation process, which can cause spurious fluctuation in the frequency response of the device, and affects pass band flatness, stop band rejection capability and overall filtering performance. Especially in multi-band and high-power applications, the transverse mode problem is more prominent, and the realization of high reliability and high performance of the device is severely restricted. In the prior art, common transverse mode suppression methods mainly focus on optimization of electrode finger structures, such as electrode finger weighting, aperture modulation, finger width gradient and other means, in an attempt to suppress the transverse mode by changing the distribution of the excitation sound field. However, such methods often fail to fully consider the influence of the bus bars and the connection structures thereof on the propagation of the sound field, especially the length and arrangement of the bus bar connection fingers, the length and distribution of the dummy fingers, and the structural parameters such as the gaps between the electrode fingers and the dummy fingers, which can have significant influence on the lateral propagation and reflection of the sound waves in the actual device, thereby restricting the suppression effect of the transverse mode. In addition, some prior art attempts have been made to control the sound velocity distribution by means of thin film etching, partial material modification, or multilayer composite structure, etc., so as to suppress the transverse mode. However, these methods often bring problems of increased process complexity, increased manufacturing cost, difficulty in ensuring structural consistency, etc., which are unfavorable for mass production and commercial application. Therefore, how to effectively inhibit the transverse mode in the TF-SAW device and improve the stability and the overall performance of the frequency response of the TF-SAW device through structural design and parameter optimization without significantly increasing the process complexity has become a key technical problem to be solved in the art. Disclosure of Invention The invention provides an electroacoustic transducer and a TF-SAW device, which are used for solving the problem of insufficient lateral mode inhibition, the problem of lack of systematic optimization of artificial finger design, the problem of acoustic leakage and lateral mode under a non-artificial finger structure, the problem of balance of device performance and process complexity and the problem of matching of the electroacoustic transducer and a piezoelectric substrate. The method has the core technical scheme that the effective suppression of the transverse mode is realized by optimizing a multi-stage bus bar structure, sound velocity partition, electrode finger mass design and false finger layout, and the filtering performance and the frequency response stability are improved. The specific scheme of the invention is as follows: an electroacoustic transducer comprises a plurality of groups of interdigital electrodes formed by staggered arrangement of electrode fingers, wherein multi-stage bus bars are arranged at two ends of each interdigital electrode, each multi-stage bus bar comprises a secondary bus bar and a primary bus bar which are connected through bus bar connecting fingers, each interdigital electrode comprises a low sound velocity zone, each low sound velocity zone is provided with an electrode finger mass increasing part, When the electroacoustic transducer is provided with a prosthesis, the length beta of the prosthesis is not constant, The length D of the secondary bus bar satisfies 0.3 x λ≤d≤0.5 x λ; the average length gamma of the false finger meets the condition that gamma is m