Universal SAW gas sensor

A new principle of designing a SAW gas sensor is described. This sensor, being essentially of sorption type, also offers properties of thermometric SAW sensors. The basic idea here is that heat fluxes propagate between the SAW substrate and the working surface of the temperature-regulating system with some delay. A sensor based on this principle can detect not only the vapors of volatile substances but also gases by their thermal properties, retaining high temperature stability and speed of response unlike conventional SAW thermometric sensors. The design of this sensor built around a LiNbO₃ SAW delay line is described, and experiments on detecting a household propane-butane mixture with this sensor are reported. In particular, the responses of the sensor are measured at different gas-flow rates, two different SAW substrate temperatures, and two propane-butane concentrations. Ways of improving the sensor’s performance are discussed.     

超小型声表面波谐振器

传统声表面波谐振器中的指条反射阵占据了器件的大部分尺寸。由于剪切横波(SH wave)在材料基片的自由端面反射时不产生模式转换,因此可望利用自由端面来代替SH型声表面波谐振器中的指条反射阵,实现超小型低损耗的新型声表面波谐振器。本文首先用COM理论对新结构的谐振器进行了讨论,并且在实验上实现了120MHz至440MHz的几个单端谐振器(ST36°石英基片),其插入损耗从0.87dB至1.29dB,面积缩小到传统谐振器的50％至25％。     

利用准谐频叉指换能器实现GHz高频SAW滤波器

本文利用准谐频设计方法,在常规光刻工艺水平上,成功地实现了ＧＨＺ级声表面波（ＳＡＷ）器件,准谐频叉指换能器（ＱＨＩＤＴ）的优点为：其指条宽与指间隙可以比一般的单指换能器宽,克服了单指换能器内指间的多次反射,并且又较好地解决了普通谐频叉指换能器基频抑制不好的缺点,本文给出了制作在ＳＴ石英基片上,工作频率１１２８ＭＨＺ的声表面波滤波器的实验结果。     

Quasi-optical antenna duplexers

The development of antenna duplexers for transceiving quasi-optical systems of millimeter and submillimeter wavelengths are considered for two groups of devices — passive and active action. Duplexers, using properties of quasi-optical hybrids, belong to the first group, and duplexers on the base of semiconductor or ferrite devices are included to the second group. Results of developments and investigations of considered devices in the millimeter wave range are presented.     

A novel matching network employing surface acoustic wave devices for W-CDMA power amplifiers

This paper describes a new approach of designing high Q surface acoustic wave (SAW) resonators as an inductive element in the matching network for W-CDMA power amplifiers (PAs). Spiral inductors based on CMOS/BiCMOS technologies presently possess relatively low Q (typically <10) and occupy a considerably large area. In order to break through the limitations of the spiral inductors, the authors attempt to apply higher Q and wideband SAW resonators employing Cu-grating/15 degrees YX-LiNbO(3)-substrate structure to the matching network for improved PA performance. An analysis was made on SAW resonators in detail, and an SAW resonator having a very small capacitance ratio of 3.28 and moderate Q of 147.8 was developed. After discussing the frequency dependence of the effective inductances, SAW resonators, which are used to be as inductive elements in the matching networks of PAs, were designed and fabricated. The PA including the matching circuit was simulated using the characteristics of the fabricated SAW resonators. The result showed that with better shape factor and good out-of-rejection, the SAW resonators definitely work as an inductive element and could replace widely used spiral inductors.     

ZnO薄膜/金刚石在不同激励条件下声表面波特性的计算与分析

本文首先以刚度矩阵法为基础, 给出了ZnO薄膜/金刚石在四种不同激励条件下的有效介电常数计算公式. 然后以此为工具, 分别计算了多晶ZnO(002) 薄膜/多晶金刚石和单晶ZnO(002) 薄膜/多晶金刚石的声表面波特性, 并根据计算结果及设计制作声表面波器件的要求, 对ZnO膜厚的选择进行了详细地分析. 最后讨论了ZnO/金刚石/Si复合晶片可以忽略Si衬底对声表面特性影响时对金刚石膜厚的要求. 关键词： 声表面波 压电多层结构 有效介电常数 刚度矩阵法     

Evaluation of new single crystal piezoelectric materials for surface acoustic-wave applications

Surface acoustic waves (SAW), or Rayleigh waves, bound to the surfaces of piezoelectric materials are becoming rapidly significant in electronic device applications, particularly as VHF-UHF frequency filters and versatile time-domain processors. The majority of available devices utilize either signle crystalline quartz or lithium niobate as the piezoelectric medium. This paper describes briefly the growth and critical evaluation of SAW impedance and propagation properties for certain new single crystal piezoelectric materials. Crystals discussed are Czochralski-grown bismuth germanium oxide, films of zinc oxide and aluminum nitride both epitaxially grown on single crystal sapphire, and flux-grown beryllium oxide. It is concluded that bismuth germanium oxide may prove an important cost-effective alternative to both quartz and lithium niobate, and that either zinc oxide or aluminum nitride is destined to prove invaluable in the realization of monolithic circuits such as programmable tapped delay lines, in which SAW will be interfaced with metal-oxide semiconductor (large scale integrated) technology, and active SAW elements employing functional integration.     

Multifrequency characterization of viscoelastic polymers and vapor sensing based on SAW oscillators

Simplified relations for the changes in SAW velocity and attenuation due to thin polymer coatings and vapor sorption are presented by making analytic approximations to the complex theoretical model developed earlier by Martin et al. [Anal. Chem. 66 (14) (1994) 2201–2219]. The approximate velocity relation is accurate within 4% for the film thicknesses up to 20% of the acoustic wavelength in the polymer film, and is useful for analyzing the mass loading, swelling and viscoelastic effects in SAW vapor sensors. The approximate attenuation relation is accurate within 20% for very thin films, (less than 2% of the acoustic wavelength in the film). Based on these relations, a new procedure for determination of polymer viscoelastic properties is described that exploits the frequency dependence of the velocity and attenuation perturbations, and employs multifrequency measurement on the same SAW platform. Expressions for individual contributions from the mass loading, film swelling and viscoelastic effects in SAW vapor sensors are derived, and their implications for the sensor design and operation are discussed. Also, a new SAW comb filter design is proposed that offers possibility for multimode SAW oscillator operation over a decade of frequency variation, and illustrates feasibility for experimental realization of wide bandwidth multifrequency SAW platforms.     

环形定子的激光致表面波机理及可视化探测研究

开展了用于新型激光驱动马达的环形定子的激光致表面波机理及实验研究. 提出一种带有凹槽阵列结构的环形定子新设计, 建立了激光在环形定子表面激发表面波的物理模型, 揭示了影响表面波幅值的关键因素; 采用一种新颖的激光致表面波可视化探测方法, 在波长1053 nm, 脉宽30 ns, 单脉冲能量1 mJ的激光激发下, 对表面波在铜质环形定子表面的传播特性进行了可视化探测实验. 理论与实验研究表明: 当激发光斑的位置紧邻凹槽阵列时, 沿着圆环向凹槽方向传播的表面波会被齿状凹槽阵列迅速衰减和吸收, 而沿着圆环向远离凹槽方向传播的表面波能够持续传递, 从而首次实现了激光致表面波在环形定子上的单向传播; 而对没有凹槽阵列结构的圆环进行的对比实验表明, 激光致表面波在圆环表面双向传播, 最终因相互混叠和串扰等而处于混乱状态. 由激光在该种环形定子表面激发出的单向表面波, 可望在光致表面波马达及驱动机构中获得应用. 关键词： 激光致表面波 环形定子 表面波可视化 激光驱动     

移动通讯用声表面波器件发展近况

本文首先回顾了民用声表面波器件的最新发展概况．随着移动通讯的发展，声表面波器件的最大应用市场将是通讯，而低插损声表面波滤波器成为新的研究高潮．本文因此随后简要介绍了几种主要的低插损结构的研究情况及其在移动通讯中的应用．最后，展望了声表面波器件的发展趋势．     

压电基片与金属点阵厚度对行波模式声表面波陀螺仪检测灵敏度的影响

过低的灵敏度性能一直是声表面波(SAW)陀螺仪的瓶颈问题,对此,提出了一种结合金属点阵用以改善陀螺效应的新型行波模式SAW陀螺仪,并对其性能进行了评价。该结构由双延迟线型振荡器构成,两延迟线平行且反向制作于同一压电基片上,在延迟线的声传播路径上分布铜点阵。结合层状介质中声波传输特性的研究方法分析了两种压电晶体材料、不同金属点阵膜厚对传感器响应的影响,从而为确定陀螺仪的设计奠定理论基础。基于理论计算结果,研制了以128°YX LiNbO3及X-112°Y LiTaO₃为压电基片,铜点阵厚度分别为33000 Å,6000 Å,9000 Å的95 MHz声表面波陀螺仪。为改善振荡器的频率稳定性,延迟线采用了具有梳状结构的单相单向换能器结构。振荡器的测试频率稳定度达到了±5 Hz/h。利用精确速率转台对所研制的SAW陀螺仪性能进行了测试。测试结果表明:采用机电耦合系数较高的128°YX LiNbO₃基片并增加金属点阵厚度均能有效提高陀螺仪的检测灵敏度,所获得的最大检测灵敏度为2.7 Hz/(deg/s)。      

Nonlinear frequency shift in surface acoustic wave resonator operating as a gas sensor

The shift in the resonance frequency of a two-port quartz surface acoustic wave (SAW) resonator operating as a gas sensor without a selective layer is studied versus the power of an SAW excited in the resonator. At working frequencies of the resonator (≈389 MHz) placed in the flow of moisture-containing nitrogen gas, an anomalously large positive shift of the resonance frequency is observed as the SAW power exceeds 1 mW. This shift is one order of magnitude larger than that due to the nonlinear amplitude-frequency effect, which is known for quartz SAW resonators. Possible physical mechanisms underlying this phenomenon are analyzed. Experimental data indicate that such a shift is associated with the influence of a powerful SAW on sorption processes taking place on the active surface of the resonator rather than being a direct consequence of heating of the SAW substrate by the powerful SAW.     

Effects of strontium on the surface acoustic wave properties of Sm-modified PbTiO3 ceramics

The Sm-modified lead titanate ceramics with a composition of (Pb(0.88-x)Sr(x)Sm(0.08))(Ti(0.98)Mn(0.02))O(3); x = 0.05-0.25 were prepared by conventional mixed-oxide method. Surface acoustic wave (SAW) properties, including phase velocity, electromechanical coupling coefficient and temperature coefficient of frequency, were measured. The experiments successfully showed that Sr additive is helpful to obtain higher phase velocity and high electromechanical coupling coefficient. The SAW properties of our samples (V(p),k(2)) are better than some commercially-made PZT and PT samples.     

抽指加权宽带扇形叉指声表面波滤波器的等效电路分析

扇形换能器可以看成若干个沿孔径方向划分的均匀孔径换能器电端并联而成，根据梅森(Mason)等效电路模型以及由其延伸的混合场等效电路模型，推导出整个扇形换能器的导纳矩阵和频率响应，其中采用复阻抗模型考虑了叉指电极与自由表面的阻抗不连续的因素。本方法能够模拟指间反射、三次行程、指条寄生阻抗以及外围电路等对器件性能的影响；理论模拟与实验结果吻合。     

High frequency SAW stabilized oscillators for chemical agents sensors

The surface acoustic wave (SAW) chemical agents sensors usually operate in the oscillator feed-back configuration. It converts a molecular interactions between SAW surface and chemisensitive layer placed on it to relative easy to measurement electrical quantities (most often it is an operating frequency or phase change). Although in the SAW sensors the key role play chemisensitive coatings but nearly as important as the coatings are electronic circuits cooperating with SAW devices. The results of theoretical calculations show that the SAW sensors operating frequency increasing is profitable from the sensitivity point of view. Unfortunately, an advantageous sensitivity-frequency dependence is hard to apply because of decreasing of SAW device dimensions and thereby the area of the chemisensitive layer with the operating frequency. The smaller area of the layer, the smaller amount of detecting gas particles sorbed and the weakest response of the sensor. It is possible to avoid the problem using special constructions of SAW stabilised oscillators. In the paper such constructions have been described.     

Quantitative elastography provided by surface acoustic waves measured by phase-sensitive optical coherence tomography

We report on a quantitative elastography technique achieved by combining phase-sensitive optical coherence tomography (PhS-OCT) with the surface acoustic wave (SAW) method. Different from traditional optical coherence elastography, the elastography is achieved by impulse-stimulated SAW, rather than by shear waves. PhS-OCT serves not only as a detector to measure SAW signals but also as a means to provide a cross-sectional image of the sample. The experimental results indicate that the combination of PhS-OCT with SAW is feasible to provide quantitative elastography of heterogeneous tissue samples.     

Visualization of surface acoustic wave scattering by dislocations

Stroboscopic X-ray topography at the synchrotron beam line was used to visualize the propagation of a 580 MHz surface acoustic waves (SAW) in LiNbO3 crystals. For this purpose, the X-ray bursts coming from the synchrotron storage ring with periodicity of 5.68 MHz were synchronized with the SAW frequency in a phase-locked mode. This method allowed us to "stop" the SAW in time and to observe the X-ray diffraction contrast caused by the dynamic deformation field of SAW. The X-ray topographic images showed well-resolved individual acoustic wave fronts of 6 microm SAW as well as their distortions due to SAW scattering by linear dislocations. Some of the images revealed an exceptional contrast of the concentric rings about the dislocation line, which is caused by coherent interaction of the secondary elastic waves. This contrast is similar to the Fresnel zones in optics, and this conclusion is confirmed by direct summation of secondary waves emitted by local elements of a vibrating dislocation string.     

MOCVD法生长SAWF用ZnO/Diamond/Si多层结构

使用等离子体辅助MOCVD系统在金刚石,硅衬底上成功地制备了氧化锌多层薄膜材料,通过两步生长法对薄膜质量进行了优化。XRD测试显示优化后的样品具有c轴的择优取向生长,PL谱测试表明样品经优化后不仅深能级发射峰消失,同时紫外发射峰增强。对优化后的样品的表面测试显示出较低的表面粗糙度。比较氧化锌多层薄膜结构的声表面波频散曲线,ZnO薄膜声表面滤波器受膜厚和衬底材料的影响较大。当ZnO薄膜较薄时,在它上面的传播速度将与衬底上的传播速度接近,与其他衬底上生长的薄膜相比,以金刚石这种快声速材料为衬底的ZnO多层薄膜结构,声表面波滤波器的中心频率将提高1倍左右。     

Performance of Non-Contact Linear Actuators Driven by Surface Acoustic Waves*

A new kind of non-contact linear actuator （motor） driven by surface acoustic waves （SAWs） is presented, in which the stators are made from SAW delay lines using 128° YX-LiNbO3 substrates. A fluid layer is introduced between the slider and the stator of the actuator, and the slider is a circular aluminum disk suspended on the surface of the liquid （water） layer. As the SAW is excited on the stator, the SAW is converted to a leaky wave in the interface of the stator and the liquid, and then propagates into the liquid. Owing to the nonlinear effect of wave propagation, acoustic streaming is generated, which pushes the slider to move. By the experiments, the relations between the slider velocity and the experimental parameters, such as the exciting voltage of the SAWs, the thickness and the kinematic viscosity of the liquid layer, are obtained.     

新型声表面波电流传感器*

将声表面波技术的快速响应特点与磁致伸缩薄膜的高磁敏特点相结合,可实现一种快速、高灵敏、稳定可靠的新型电流检测技术。传感器由双通道差分式振荡器与沉积在传感通道器件表面的声传播路径上的磁致伸缩薄膜组成。该文基于分层介质中声传播理论及磁致伸缩效应,对声表面波电流传感机理进行了分析,以实现对传感器结构的优化设计。实验研制了采用铁钴(FeCo)薄膜的声表面波电流传感器,测试结果表明,该传感器具有快速响应和高灵敏特点。为抑制磁致伸缩薄膜自身的剩磁效应所带来的高磁滞误差,采用的有效途径是将沉积的磁致伸缩薄膜进行图形化设计。实验结果表明,采用栅阵化FeCo薄膜结构的传感器表现出更高检测灵敏度、更好线性及更低的磁滞误差。