Implementation of GHz SAW filters using quasi-harmonic interdigital transducers

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。     

谐振式检测器指条厚度对质量型声表面波传感器灵敏度的影响

研究了谐振器指条厚度对质量型声表面波传感器灵敏度的影响.利用耦合模方程推导出耦合模参量与周期栅阵禁带边界频率的关系,结合有限元及P矩阵模型,获得了声表面波传感器灵敏度随指条厚度的变化关系。制备3种不同铝指条厚度(1600?,1900?,3100?)的声表面波谐振器,通过对其表面中心区域沉积SiO_2层验证了计算结果。结果表明:采用ST-X石英基底的声表面波谐振器对SiO_2负载检测时,传感器的灵敏度随铝指条厚度的增加先变大后减小,最优归一化指条厚度为1.9%。分析表明,指条厚度对传感器灵敏度的影响主要来自于传播速度和耦合系数的共同作用,通过优化指条厚度的方法可改善传感器的灵敏度.     

单根电极或沟槽形成的栅格对声表面波的散射*

该文借鉴汪承灏先生研究栅格声表面波散射的技术路线,提出一种既不限制基片和栅格形状、类型,也不限制声波入射方向,可精确计算栅格对SAW散射的有限元通用模型。作为对《超声学》第六章"声表面波"中栅格对声表面波的反射和体波散射一节部分结论的进一步阐释和说明,计算了YZ-Li Nb O3和128?YX-Li Nb O3单晶上厚度为200 nm、宽度为1μm的单根悬浮铝栅条以及沟槽在不同频率下的反射系数曲线。提出的计算方法今后可推广应用于层状结构基底、应用到非规则指条、沟槽、金属点阵、基片端面、台阶等的反射的精确分析,为优化设计新型声表面波器件奠定理论基础。     

基于双螺旋谐振器的UHF（超高频）低频段窄带高温超导滤波器设计

由于弱耦合要求和基片尺寸限制,相对带宽小于0.5%的UHF低频段(～500 MHz)窄带高温超导滤波器一直是滤波器设计制作中的难点.本文应用双螺旋弱耦合谐振器设计制作了中心频率为500 MHz,相对带宽为0.4%的窄带高温超导滤波器.通过采用80 m微带线宽工艺,六节滤波器尺寸仅为28ram 8mm.测量结果表明,未经调谐,通带内最小和最大插损分别为0.12 dB、0.46 dB,反射损耗小于-13.9 dB;带边陡峭度为34 dB/MHz,带外抑制为70dB.设计及测试结果表明,双螺旋谐振器比较适用于低频窄带滤波器的设计.     

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。     

谐振式检测器谐振腔对声表面波气相色谱仪灵敏度的影响

研究了谐振式检测器谐振腔对声表面波气相色谱仪灵敏度的影响。构建无液膜负载和有液膜负载下压电基片和金属指条结构的三维有限元模型,利用有限元方法提取不同周期结构的耦合模参量,结合P矩阵级联技术,推导出传感器灵敏度随检测器腔体结构改变的变化关系。实验制备了两种三换能器结构的声表面波谐振器,其输入换能器与输出换能器间距离分别为22.25倍波长和1.25倍波长,通过测试甲基膦酸二甲酯气体,验证理论计算结果。结果表明:缩短谐振器的谐振腔长度使器件中心处能量更为集中,有效地提高了声表面波气相色谱仪灵敏度。      

LB膜在SAW ILRAC及RAC相位修正中的应用

声表面波反射栅脉冲压缩器件(RAC)及直列式反射栅脉冲压缩器件(ILRAC),在脉冲压缩雷达及其他一些系统中用作匹配滤波,是一种重要的模拟信号处理器件。声表面波在器件基片上的各处速度的轻微差别将会影响器件的性能。器件中的金属膜结构(叉指换能器;金属栅条,点阵等)会改变表面波速度,因而镀膜,光刻等工艺的误差将对器件的参数产生影响,最终表现为对于到达输出换能器的声表面波的相位导致误差,降低脉冲压缩输出的主副瓣比。     

应用LiNbO_3声表面波驱动的全光纤声光频移器

介绍一种工作在10.7MHz的全光纤声光频移器.它由在LiNbO_3基片上制作的叉指电极换能器产生的声表面波驱动.当驱动电功率1.5W时,频移光转换效率达35％.     

低插损微小型表面漏波谐振滤波器

本文的工作在于,利用49°Y旋转铌酸锂基片,在其基片的表面激励表面漏波,利用其机电耦合系数k_s~2比较高;短路金属反射条声阻抗变化比较大的特点,成功地研制了表面漏波谐振滤波器(Surface Leaky waves resonators简称SLWR)。这种谐振滤波器的突出优点是所占的基片面积小,仅为同频率的声表面波谐振滤波器(SAWR)的1/4—1/5,50Q系统中的插入损耗仅2—5dB。 本文在实验上,测定了49°Y旋转LiNbO_3基片表面的机电耦合系数k_s~2及声阻抗失配比│8│,从而计算了不同短路金属反射条时的反射系数。利用等效电路模型定性分析了它在50Q系统中的插入损耗。并介绍了典型的实验数据。     

基于指条厚度优化的冷凝式SAW气体传感器灵敏度提升方法

该文通过对声表面波谐振器指条厚度的优化提升了冷凝式气体传感器的灵敏度。基于流固耦合理论,利用有限元商业软件建立了有液膜负载和无液膜负载下的多物理场三维周期模型,并提取了相应的耦合模参量,利用耦合模模型及P矩阵级联技术,计算了不同指条厚度下液膜负载引起的传感器响应,获得了冷凝式声表面波气体传感器灵敏度随指条厚度的变化关系。实验中制备了6种不同电极厚度的声表面波谐振器,并利用甲基膦酸二甲酯实验样品完成了传感器的响应测试,验证了理论分析的正确性。结果表明,冷凝式声表面波气体传感器的灵敏度随指条厚度的增加先变大后减小,最优归一化电极厚度为6.4%～7.6%之间。该研究结果对进一步提升传感器灵敏度具有重要意义。     

Development of two-port surface acoustic wave resonator with Al/Au electrodes for gas sensing

Simple and efficient surface acoustic wave(SAW)two-port resonators with low insertion loss and high Q-values on ST-X quartz substrate using a corrosion-proof A1/Au-stripe electrode structure are developed for gas sensing.It was composed of two shorted grating reflectors and adjacent intedigital transducers(IDT),and an active metal film in the cavity between the IDTs for the sensitive film coating.The devices are expected to provide good protection towards metal electrode for gas sensors application in chemically reactive environments.Excellent device performance as low insertion loss,high Q factor and single-mode are achieved by carefully selecting the metallic electrode thickness,cavity length and acoustic aperture.Prior to fabrication,the coupling of modes(COM)model was performed for device simulation to determine the optimal design parameters.The fabricated single-mode SAW resonator at operation frequency of 300 MHz range exhibits matched insertion loss of~6.5 dB and loaded Q factor in the 3000 range.Using the fabricated resonator as the feedback element,a dualresonator-oscillator with excellent frequency stability(0.1 ppm)was developed and evaluated experimentally,and it is significant for performance improvement of SAW gas sensor.     

应用于气体传感器的具有铝/金电极的单模式两端对声表面波谐振器

为改善气体传感器性能,通过器件优化设计获得了一种应用于气体传感器的具有低损耗、高品质因子(Q)的单模式两端对声表面波(SAW)谐振器。该谐振器由两个换能器、分置于换能器两边的短路栅反射器以及在换能器之间分布的用于敏感膜镀膜的约2.5mm金属薄层构成。谐振器采用铝/金双层电极以降低测试气体环境的腐蚀影响。利用经典耦合模(COM)理论对器件性能进行了仿真以提取优化的结构设计参数。基于仿真结果,实验研制了基于300MHz频率的新型铝/金电极SAW两端对谐振器,测试结果显示所研制器件具有较低损耗(〈7dB),较高Q值(-3000)以及单一谐振模式的特点,并且,以所研制的新型谐振器为频率控制单元的谐振器型振荡器表现出良好的频率稳定度(t15Hz/h),这对于改善气体传感器的检测下限及稳定性等性能指标具有重要意义。      

The effect of geometry and post-annealing on surface acoustic wave characteristics of AlN thin films prepared by magnetron sputtering

This paper describes experimental relationship between surface acoustic wave (SAW) properties of two-port SAW resonators based on polycrystalline aluminum nitride (AlN) thin films grown on Si substrates by using a pulsed reactive magnetron sputtering system and their geometry's parameters. Moreover, the influence of post-deposition heat treatment on SAW properties of AlN thin films was investigated at different annealing temperature (600 °C and 900 °C). The measurement results show the number of the inter-digital transducers (IDT) finger pairs (N), the number of reflectors grating pairs (R) and the IDT center-to-center distance (L) related to insertion loss of SAW resonators. The best result of insertion loss was 15.6 dB for SAW resonators with R = 160 pair, N = 5 pair and L = 750 μm. At the same geometry parameters, the SAW velocity and insertion loss were improved slightly after annealing at 600 °C and were worse for the films annealed at 900 °C by changes in the surface morphology and stress on the film.     

Study of noise characteristics of baw and SAW quartz resonators

The low-frequency noise of bulk- and surface-acoustic-wave (BAW and SAW) resonators at frequencies of from 100 to 600 MHz is studied. It is shown that both SAW and BAW resonators have parameter (resonant-frequency) fluctuations with 1/f power spectra with considerable intensity spreads: approximately 20 dB for SAW and more than 30 dB for BAW resonators. The phase-noise floor of 100-MHz oscillators with BAW resonators is –150 dB/Hz for a 1-kHz offset frequency. The phase-noise level of oscillators with SAW resonators at 400–600 MHz is higher by 5–10 dB (scaled to a 100-MHz carrier frequency).Presented at All-Union Coordinating Conference Low-Frequency Noise in Semiconductor Devices (Chernogolovka, Moscow Region, June, 1991).Ural Polytechnic Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 12, pp. 1143–1152, December, 1993.     

Effects of Mn‐doping on surface acoustic wave properties of ZnO films

Surface acoustic wave (SAW) filters based on Mn‐doped ZnO films have been fabricated and effects of Mn‐doping on SAW properties are investigated. It is found that the electromechanical coupling coefficient (K²) of Zn_0.913Mn_0.087O films is 0.73 ± 0.02%, which is 73.8% larger than that of undoped ZnO films (0.42 ± 0.02%). Zn_0.913Mn_0.087O film filters also exhibit a lower absolute value of insertion loss (|IL|) of 16.1 dB and larger bandwidth (BW) of 5.9 MHz compared with that of undoped ZnO film filter. However, Zn_0.952Mn_0.048O film filters exhibit a smaller K² of 0.34 ± 0.02%, larger |IL| of 26.9 dB and smaller BW of 3.5 MHz. It is suggested that the SAW properties can be improved by appropriate Mn‐doping and Mn–ZnO/Si multilayer structure with large d₃₃ is promising for wide‐band and low‐loss SAW applications. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Superconducting tunable filter with constant bandwidth using coplanar waveguide resonators

In this paper we propose a two-pole varactor-tuned superconducting filter using coplanar waveguide(CPW) spiralin-spiral-out(SISO) resonators. Novel internal and external coupling structures are introduced to meet the requirements for a tunable filter with a constant absolute bandwidth. The fabricated device has a frequency tuning range of 14.4%at frequencies ranging from 274.1 MHz to 317.7 MHz, a 3-d B bandwidth of 5.14 ± 0.06 MHz, and an insertion loss of0.08 d B–0.70 d B. The simulated and measured results are in excellent agreement with each other.     

Wi-Fi频段体声波滤波器的设计

为了保证移动设备在Wi-Fi频段正常工作且不受相邻频段的干扰,设计了一种用于Wi-Fi IEEE802.11b频段(2402~2482 MHz)的BAW滤波器。设计基于薄膜体声波谐振器(FBAR)的一维Mason等效电路模型构成初始结构的梯形滤波器。然后,将串联FBAR的谐振区面积值以及串、并联FBAR的谐振区面积的比值设置为优化参数,以所需的滤波器的带内插损和带外抑制为优化目标,使用ADS软件基于遗传和梯度的优化算法对滤波器进行优化。在滤波器的设计过程中,为了使仿真结果更加精确,采用声电磁协同仿真方法对滤波器进行仿真,并与Mason 等效电路模型仿真结果对比,结果表明,滤波器性能有所下降,带内插损增大1.6 dB,带内纹波增大1.1 dB,带外抑制基本一致。所设计的Wi-Fi频段的BAW滤波器具有低插入损耗(小于3 dB)、高带外抑制(大于40 dB)性能。     

低射频窄通带高温超导滤波器设计

本文在双面YBCO高温超导薄膜上设计了12节低射频窄通带超导带通滤波器.中心频率385MHz,相对带宽1.3%,考虑到窄带滤波器对衬底介电常数的敏感性,采用MgO基片以避免基片孪晶造成的介电常数非均匀性带来的影响.为了能在不大于2英寸的基片上制备出如此低频的高性能超导滤波器,设计中选用了1/4波长的螺旋形谐振结构.设计结果的带边陡峭度达到了50dB/MHz,带内插损小于0.014dB,带外抑制达到100dB,二倍频处抑制度优于130dB.     

ZrO_2的掺杂对于单畴YBCO超导块材的影响

研究了在Y211中掺入ZrO2对于用顶部籽晶熔渗方法制备YBCO块材的影响,以及不同掺杂比例对于样品表面形貌和磁悬浮力的影响.实验表明,随着ZrO2掺杂量的增加,样品的磁悬浮力有增大的趋势.这种现象可能是由于ZrO2的掺杂在样品中形成了磁通钉扎中心,有效的提高了超导体的物理性能.     

应用于无线传感器的声表面波反射型延迟线的耦合模分析

基于耦合模理论对一种应用于无线传感器的声表面波(SAW)反射型延迟线的性能进行了优化模拟分析。结合混合等效电路模型推导出评价这种器件性能的时域反射系数S₁₁。典型的SAW反射型延迟线包含置于压电基片之上的一个换能器与沿声波传播方向设置的多个反射器。讨论了器件性能的各种结构性影响因素如换能器结构以及反射器类型等,并以此获得优化的器件设计参数。在理论优化分析的基础上,以41°YX LiNbO₃为压电基片,结合铝电极试验制作了采用单向单相换能器(SPUDT)与3个短路栅反射器的440 MHz SAW反射型延迟线器件,并与理论分析结果予以对比与评价分析。