橋本 研也

In this paper, we discuss the nonlinear performance difference between surface acoustic wave (SAW) and bulk acoustic wave (BAW) resonators, which include intermodulation distortion (IMD) or triple-beat (TB) products, and indicate the importance of reducing even-order nonlinearities of BAW resonators. We were able to validate the accuracy and efficiency of our proposed simulation technique for BAW devices by comparing the results of our simulation with experimental data. We verified that our circuit model is a high-performance tool that can be used to predict BAW device nonlinearities, and we propose how to suppress even-order nonlinearities by employing a thin-film bulk acoustic resonator (FBAR) duplexer for wideband code division multiple access (WCDMA) band 1. Finally, we introduce highly linear FBAR duplexers. (C) 2010 The Japan Society of Applied Physics

In this paper we analyze for the first time quantitatively the acoustic losses in a film bulk acoustic wave resonator (FBAR), which are expected to deteriorate the device performance. To this end, we regard the effective acoustic admittance, conduct laser probing measurements and finite element modeling (FEM). For our device under test (DUT) at the anti-resonance frequency, we compare the relative power of observable modes in the active and passive area and point out the relevant energy loss mechanism in terms of a single mode. By scattering analysis of the resonator's border region, we can identify the respective excitation mechanism within the active area and therefore can consider specific countermeasures to improve the device performance. Practically applied for the first time, the utilized methods and the overall procedure are explained in detail and are applicable to investigate acoustic energy loss as well at other frequencies as in other devices. (C) 2010 The Japan Society of Applied Physics

This paper describes the characterization of SAW propagation in layered substrate and overlayered structures. The software based on the finite element method and spectral domain analysis was newly developed and applied to the characterization of SAW propagation under an infinitely-long Al interdigital transducer on a rotated Y-cut LiTaO(3)/sapphire substrate. Because of the finite LiTaO(3) thickness, a series of spurious resonances appears. It is shown that the excitation strength of the spurious resonances changes with frequency as well as the rotation angle, which reflects the frequency and rotation angle dependence of the energy leakage. Next, the analysis was carried out for SAWs propagating in a SiO(2) layer/Al IDT/42 degrees YX-LiTaO(3) structure. It is shown that the influence of the SiO(2) layer is significantly dependent on the location where the SiO(2) layer is deposited. In particular, it is shown that when the SiO(2) layer is deposited only on top of the electrodes, the SAW reflectivity increases compared with when the SiO(2) layer is deposited between and on top of electrodes.

In this paper, we describe a focus adjustment system designed especially for a fast-mechanical-scanning laser probe for radio-frequency surface and bulk acoustic wave devices. When high spatial resolution is necessary for the observation, one needs an objective lens of large magnifying power with extremely shallow focal depth. Then, a small inclination of a measurement device may cause severe defocus resulting in blurred images. We installed the focus adjustment system in the laser probe, and showed that even with inclination, high-quality information of the wave field can be acquired without reducing the scanning speed. (C) 2009 The Japan Society of Applied Physics

In this paper, we describe the development of an integrated software environment for the image processing of complex data captured using a phase-sensitive surface and bulk acoustic wave (SAW/BAW) laser probe system. The developed software displays the amplitude and phase images of the acquired results and a motion movie of the field pattern. Prior to fast Fourier transform (FFT) and/or inverse FFT (IFFT) operation, we can extract or withdraw specific data in x-y or beta(x)-beta(y) space by using the mouse on the image. Using the software with a graphical user interface, efficient diagnosis of SAW/BAW devices is made possible. (C) 2009 The Japan Society of Applied Physics

This paper describes the application of the developed fast-scanning laser probe system to the diagnosis of frequency dependence of lateral energy leakage occurring in RF bulk acoustic wave (BAW) devices. According to wavenumber domain analyses, dispersion relation for the device under test is derived, the leakage behaviors at different frequencies are shown as images, and energy of each lateral mode is evaluated quantitatively. The cause of the lateral energy leakage and its frequency dependence are discussed. It is shown that the cause of lateral energy leakage is the higher order transverse modes which are not excited at frequency higher than a cut-off frequency (f(c)) for the longitudinal extension mode. It is demonstrated that by using this laser probe system, the lateral energy leakage variation upon frequency can be seen intuitively, and the underlying mechanism for the leakage can be analyzed and explained clearly. (c) 2009 The Japan Society of Applied Physics

This paper proposes a new design technique for a ladder-type filter to reduce the passband width without sacrificing the insertion loss, out-of-band rejection, and steepness of the transition bands. First, it is shown that 2 transmission zeros can be generated by connecting an additional resonator in either series or parallel arm of the ladder filter topology. This new filter topology can be designed systematically by the derived-in transformation. Second, it is demonstrated that the narrow bandwidth, sharp transition bands, and large out-of-band rejection are simultaneously realized by applying the present technique to specifically designed ladder-type filters. Finally, this technique is applied to the design of a SAW filter fabricated on the Cu-grating/15 degrees YX-LiNbO(3) structure.

In this paper, we describe a full-wave analysis of an SiO2 overlay with a finite thickness/metal grating/rotated Y-cut X-propagating LiNbO3 (YX-LN) substrate structure. The effects of the thickness and surface topology of the SiO2 overlay and the metal grating selection upon the excitation and propagation characteristics of acoustic guided modes are discussed in detail. It is shown that in the structure there propagate three acoustic guided modes. One type of mode concentrates the energy near the metal grating and generates piezoelectric boundary acoustic waves (PBAWs) with a relatively large electromechanical coupling factor when the SiO2 thickness becomes semi-infinite. Another mode concentrates its energy near the top surface of the SiO2 overlay and generates the Rayleigh-type surface acoustic wave (SAW) on SiO2 when the thickness is semi-infinite; with an increase in SiO2 thickness, it rapidly loses its piezoelectric coupling. The remaining mode is a series of guided modes trapped in the SiO2 layer, in which the SiO2 layer behaves as a waveguide because of its low acoustic wave velocities. (c) 2009 The Japan Society of Applied Physics

In this paper, we describe the fabrication of Al grating electrodes embedded in a slotted SiO2 film on a 128 degrees YX-LiNbO3 substrate in order to control both reflection characteristics and the temperature coefficient of frequency (TCF) of surface acoustic wave (SAW) devices. First, the fabrication process is discussed. It is shown that the combined usage of ion milling and reactive ion etching enables independent control of the thicknesses of the slotted SiO2 film and grating electrodes to be embedded in the slots. Next, the process is applied to the fabrication of an SAW transversal filter, showing the possibility of controlling the reflection characteristics and TCF independently. (c) 2009 The Japan Society of Applied Physics

This paper describes full-wave analysis of piezoelectric boundary acoustic waves (PBAWs) propagating along a metallic grating sandwiched between 2 semi-infinite layers. In the analysis, the finite element method (FEM) is used for the grating region while the spectral domain analysis (SDA) is applied for an isotropic overlay region as well as a piezoelectric substrate region. The combination of the FEM and SDA makes the numerical analysis very fast and precise. As an example, the analysis was-made on the PBAWs propagating in an SiO(2) overlay/Cu grating/rotated Y-cut LiNbO(3) structure. It is shown that both the shear-horizontal (SH) type and Rayleigh-type PBAWs are supported in the structure, and that their velocities are very close to each other. Thus spurious responses due to the Rayleigh-type PBAW should completely be suppressed for device implementation. Discussions are made in detail on the influence of Cu grating thickness, substrate rotation angle, and metallization ratio on excitation and propagation characteristics of the SH- and Rayleigh-type PBAWs.

A droplet manipulator working with low driving power was developed by using the surface acoustic wave (SAW) technology. The manipulator was driven at a relatively high frequency of 350 MHz to increase the SAW power density. First, a single-phase unidirectional transducer (SPUDT) was designed. Because of its low insertion loss of 1.5 dB and high directivity of 10 dB, the SPUDT successfully conveyed a 100-nl water droplet with RF input power of 18 dBm (60 mW). Second, the SPUDT design was extended to a curved transducer to focus and launch the SAW energy into the narrow waveguide. Owing to the increased SAW power density, the required SAW power was reduced to 15 dBm (30 mW) for the 100-nl droplet manipulation. In addition, fabrication of liquid injectors was discussed for the formation of tiny droplets. (C) 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(4): 49-55, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10232

A high-accuracy modeling methodology for electrical characteristics of transmission electrodes on SAW substrates is established. In order to design SAW filter accurately, it is necessary to extract precise SAW material parameters from the measurement value of the reference SAW resonator. When measuring the SAW resonator, transmission lines are needed for feeding to contact probes. De-embedding procedure, which removes the influence of transmission lines, is very important for accurate characterization of the SAW resonator. In this paper, we apply the improved de-embedding procedure using Short, Open, and Thru calibration patterns. The de-embedded transmission line is separated in four parts and extracted the RLGC equivalent. circuit model for each part. Furthermore, we derive the frequency characteristic of resistance element of the transmission line. Finally, de-embedding the transmission line accurately, we can get intrinsic characteristic of the SAW resonator. This method must be very useful to extract SAW material parameters and we can design SAW filters more effectively. (C) 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(2): 49-55, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10230

This paper demonstrates a novel method to evaluate the reflection behavior of a waveguide mode at an arbitrary reflective geometry by a time harmonic simulation based on the finite element method (FEM). In the FEM model, we insert a damping mechanism at the acoustic input port. This facilitates the evaluation of the scattering behavior in the frequency domain. Our approach supersedes the time consumption and calculation power necessary for the time to frequency domain conversion. We check validity of this approach and demonstrate its effectiveness for the evaluation of the scattering behavior at the free boundary of a plate and a stepped waveguide. ©2009 IEEE.

In this paper, we discuss the nonlinear performance difference between surface acoustic wave (SAW) and bulk acoustic wave (BAW) resonators, which are inter-modulation-distortion (IMD) and triple-beat (TB) products, and indicate the importance to reduce even-order nonlinearity of BAW resonator. Then, we were able to validate the accuracy and efficiency of our proposed simulation technique on BAW devices by comparing our simulation with experimental data. We verified that our circuit model is a high-performance tool that can be used to predict BAW device nonlinearities. Finally, we produced the thin film bulk acoustic resonator (FBAR) duplexer with highly linear performances for wideband code division multiple access (WCDMA) band 1. ©2009 IEEE.

The UMTS Band I and Band IV systems have a wide frequency interval between transmitting (Tx) and receiving (Rx) bands. When developing a small-sized SAW duplexer for this application, one needs a substrate with a large electromechanical coupling factor (K2) and a good temperature coefficient of frequency (TCF). Although a SiO2/Al/LiNbO3 structure meets these two requirements, it also supports a certain number of unwanted spurious responses. As previously discussed by the authors, the Rayleigh-mode spurious can be suppressed by controlling the cross-sectional shape of a SiO2 overlay deposited on resonator electrodes. Here, we analyzed the Rayleigh-mode spurious behavior of a non-flat SiO 2/Al/LiNbO3 structure by using FEM/SDA. In this study, we applied the extended FEM/SDA to the non-flat SiO2/Al/LiNbO 3 structure. The SiO2 structure has a trapezoidal shape, which we developed for suppressing the spurious responses. The analysis indicates that the spurious level due to the Rayleigh-mode decreased with a decrease in the average width of the trapezoidal region. Furthermore, the results of simulation agree well with those obtained experimentally. We have analyzed the behavior of Rayleigh-mode spurious on the non-flat SiO 2/Al/LiNbO3 structure. It was shown that the spurious level changes in both the shape and mass of SiO2 on resonator electrodes. ©2009 IEEE.

This paper describes the enhancement of the measurement speed by compensating delay time caused in detection electronics. As a demonstration, an SAW field in a one-port resonator was visualised by the developed system. It is shown that under optimal compensation, the influence of the delay time can be dissolved, and that a high quality image is obtained even when the two-way data scan is applied. Compared with the conventional system, the sampling rate was made double. ©2009 IEEE.

This paper describes an attempt to develop extremely wideband multi-mode surface acoustic wave (MMS) filters in GHz range. The Cu-grating/15°YX- LiNbO3 (15-LN)-substrate structure is employed. First, a design tool developed for the present purpose is detailed. Precise simulation is performed using a modified coupling-of-modes (COM) model, where the coupling between propagating surface and bulk acoustic waves is taken into account. Parameters necessary for the simulation are determined experimentally. Next, this simulation tool is used to design a wideband MMS filter employing pitch-modulated IDTs proposed by the authors. It is shown that a factional bandwidth of more than 12% is achievable by successfully using six SAW resonances supported in the MMS structure. The designed MMS filter was fabricated on a Cugrating/15-LN-substrate structure. The passband width of 12.6% and the minimum insertion loss of 1.2 dB were experimentally obtained around 850 MHz. The measured result was in good agreement with the simulation. ©2009 IEEE.

This paper proposes a focusing method based on multiple scanning of a device surface to be observed, which is particularly-suitable for a fast-mechanical-scanning and phase-sensitive laser probe for radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices. When high spatial resolution is required for the observation, one needs an objective lens of large magnifying power with extremely shallow focal depth. Accordingly, an uneven surface and tiny inclination of a BAW device cause acquired images a considerable defocus, by which it is difficult to obtain precise and reliable field quantities related to acoustic waves in the device. The proposed method is shown to be most effective in avoiding this sort of defocus and able to focus the entire surface. By this method, for example, we could clearly observe power leakage in an FBAR structure. ©2009 IEEE.

This paper discusses the requirements for piezoelectric thin film applications to radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices. First, we survey the basic properties of RF SAW/BAW devices. We then discuss how device performances depend on the acoustic and piezoelectric properties of the piezoelectric thin films. Next, we discuss the effects of crystal grains and their boundaries within the thin films, and show how the binding strength of crystal grains affects the excitation and propagation of acoustic waves. Finally, we present basic design and characterization procedures for an SAW transversal filter employing an AlN/diamond structure.

This paper describes a focus adjustment system particularly designed for the fast-mechanical-scanning and phase-sensitive laser probe for radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices. When high spatial resolution is necessary for the observation, one needs an objective lens of large magnifying power with extremely shallow focal depth. Then a tiny inclination of a measurement device may cause severe defocus resulting in blurred images. We installed the focus adjustment system in the laser probe, and showed that even there is the inclination, high quality information of the wave field c an be acquired without slowing down the scanning speed. The laser probe with the focus adjustment function is applied to the characterization of RF SAW devices operated in 2 GHz range. It is shown the spatial resolution better than 0.5 mu m is obtainable.

This paper describes how the propagation characteristics of shear-horizontal (SH) type piezoelectric boundary acoustic waves (PBAWs) change with overlay and metallic grating materials. We theoretically investigated the PBAW characteristics for various combinations of the overlay and metallic grating materials, and attempted to validate the qualitative prediction previously discussed and find the possible best material combination. The results are in agreement with the qualitative prediction. That is, large electromechanical coupling factor K(2) is obtained when materials having small mass densities rho and materials having extremely large rho shear modulus c(44) are chosen, respectively, for overlay and metallic grating. When VX-LiNbO(3) is assumed as a substrate, for example, the best choice seems SiO(2) and An for overlay and metallic grating, respectively. Although metals with extremely large rho and c(44) such as W and Ta offer large K(2), they may not he acceptable for practical applications for their large electric resistivity.

We have developed an X-band filter utilizing air-gap-type film bulk acoustic resonators (FBARs). The air-gap structure is simple and cost-effective. Results from both simulations and experiments demonstrate that a dome-shaped air gap was formed between the substrate surface and the bottom electrode and that an air-gap-type FBAR structure was possible. The air gap can be formed on the flat substrate using stress control of piezoelectric and metal films without using a thick sacrificial layer. As a result, the fabricated X-band FBAR operated successfully with a keff2 of 6.30%, a resonance Q of 246, and an antiresonance Q of 462. The fabricated filter had a center frequency of 9.07 GHz, a fractional bandwidth of 3.1% and a minimum insertion loss of 1.7 dB. © 2008 The Japan Society of Applied Physics.

This paper described recent advance in the detection system for the fast-scanning and phase-sensitive laser probing system for surface acoustic wave (SAW) devices operating in a 2 GHz range. Electric and electro-optic components were examined, and high sensitivity and high signal-noise ratio were achieved in a 2 GHz range without reducing the signal bandwidth. The developed detection system was installed to the laser probe system, and its performance was demonstrated by the SAW field visualisation of a shear-horizontal SAW device operating in a 2 GHz range. [DOI: 10.1143/JJAP.47.4108]

In this paper. we describe the development of a miniature surface acoustic wave (SAW) duplexer for Band I in the standard of the Third-Generation Partnership Project (3GPP) at a 2 GHz band. We employed a shear-horizontal SAW on a SiO2 overlay/thick Al elcctrode/5 degrees YX-LiNbO3 Structure. which offers a high electromechanical coupling coefficient (K-2) as well as a small temperature coefficient of frequency (TCF). This feature is crucial for the realization of a wide duplex gap between the transmitting and receiving, bands in the Band I specification. We investigated experimentally that the Spurious response Caused by the Rayleigh-mode could effectively be suppressed by controlling the cross-sectional shape of a SiO2 overlay on interdigital transducer (IDT) electrodes. In addition. the result also showed how this spurious response depends on IDT design parameters. i.e., electrode pitch and metallization ratio. The developed SAW duplexer was installed in a 2.5 x 2.0 mm(2) package, and exhibited a low insertion loss. a high out-of-band rejection and a small TCF. [DOI: 10.1143/JJAP.47.4052]

This paper describes a circuit model for the analysis of nonlinearity in the filters based on radio-frequency (RF) bulk acoustic wave (BAW) resonators. The nonlinear output is expressed by a current source connected parallel to the linear resonator. Amplitude of the nonlinear current source is programmed proportional to the product of linear currents flowing in the resonator. Thus, the nonlinear analysis is performed by the common linear analysis, even for complex device structures. The analysis is applied to a ladder-type RF BAW filter, and frequency dependence of the nonlinear output is discussed. Furthermore, this analysis is verified through comparison with experiments.

This paper describes the application of the developed fast-scanning laser probe system to the diagnosis of frequency dependence of lateral energy leakage occurring in RF BAW devices. According to wavenumber domain analyses, dispersion relation for the device under test is derived, the leakage behaviors at different frequencies are shown as images, and energy of each lateral mode is evaluated quantitatively. The cause of the lateral energy leakage and its frequency dependence are discussed. It is shown that the cause of lateral energy leakage is the higher order transverse modes which are not excited at frequency higher than a cut-off frequency (f(c)) for the longitudinal extension mode. It is demonstrated that by using this laser probe system, the lateral energy leakage variation upon frequency can be seen intuitively, and the underlying mechanism for the leakage can be analyzed and explained clearly.

This paper proposes a new design technique for a ladder-type filter to reduce the passband width without sacrificing the insertion loss, out-of-band rejection and steepness of the transition bands. First, it is shown that two transmission zeros can be generated by connecting an additional resonator in either series or parallel arm of the ladder filter topology. This new filter topology can be designed systematically by the derived-m transformation. Secondly, it is demonstrated that the narrow bandwidth, sharp transition bands and large out-of-band rejection are simultaneously realised by applying the present technique to specifically designed ladder-type filters. Finally, is technique is applied to the design of a SAW filter fabricated on the Cu-grating/15 degrees YX-LiNbO3 structure.

This paper describes full-wave analysis of the SiO(2) overlay with finite thickness/metal grating/rotated YX-LN substrate structure. The influence of thickness and surface topology of the SiO(2) overlay, metal grating selection (copper or aluminum) upon excitation and propagation characteristics of acoustic guided modes are discussed in detail. It is shown that in the structure there propagate several types of acoustic guided modes. One type of mode concentrates the energy near the metal grating, and becomes the piezoelectric boundary acoustic waves with relatively large electromechanical coupling when SiO(2) thickness becomes semi-infinite. Another mode concentrates its energy near the top surface of the SiO(2) overlay and becomes the Rayleigh-type SAW on SiO(2) when thickness is semi-infinite. With an increase in SiO(2) thickness, it rapidly loses its piezoelectric coupling. The remaining mode is a series of guided modes bounded in the SiO(2) layer, in which the SiO(2) layer behaves as a waveguide because of its low acoustic wave velocities.

This paper describes a circuit model for the analysis of nonlinearity in the filters based on radio-frequency (RF) bulk acoustic wave (BAW) resonators. The non-linear output is expressed by a current source connected parallel to the linear resonator. Amplitude of the non-linear current source is programmed proportional to the product of linear currents flowing in the resonator. Thus the non-linear analysis is performed by the common linear analysis even for complex device structures. The analysis is applied to a ladder-type RF BAW filter, and frequency dependence of the non-linear output is discussed. Furthermore, this analysis is verified through comparison with experiments.

Preparation of piezoelectric AlN thin films on diamond substrates, and their application to SHF SAW devices are discussed. It is confirmed that DC-TFTS method enable to prepare highly c-axis oriented AlN films on polycrystalline diamond substrates. The AlN surface was smooth enough to fabricate fine electrodes with the width of the order of sub-microrts. Transversal filters working around 5 GHz were fabricated to characterise SAW propagation on the Al-electrodes/AlN/diamond-substrate structure. The theory and measurements of the devices suggested that the largest reflectivity of Al-grating is achieved when the thickness of electrodes is about 0.20p for the AlN thickness is 0.85p, where p is the grating electrode pitch. Considering the facts, a one-port resonator was fabricated, which has relatively thick electrodes in order to realise high Q-factor. The measured Q-factor and capacitance ratio of the resonator were 650 and 155, respectively. It is seen from these results that the optimisation of the thickness for the electrodes as well as AlN films is very important to develop high performance SHF SAW devices using Al-electrode/AlN/diamond-substrate structure.

This paper describes full-wave analysis of piezoelectric boundary acoustic waves (PBAWs) propagating along a metallic grating sandwiched in between two semi-infinite layers. In the analysis, the finite element method (FEM) is used for the grating region while the spectral domain analysis (SDA) is applied for an isotropic overlay region as well as a piezoelectric substrate region. Combination of the FEM and SDA makes the numerical analysis very fast and precise. As an example, the analysis was made on the PBAWs propagating in an SiO(2) overlay/Cu grating/rotated Y-cut LiNbO(3) structure. It is shown that both the shear-horizontal (SH) type and Rayleigh-type PBAWs are supported in the structure, and that their velocities are very close to each other. Thus spurious responses due to the Rayleigh-type PBAW should completely be suppressed for device implementation. Discussions are made in detail on the influence of Cu grating thickness, substrate rotation angle, and metallization ratio on excitation and propagation characteristics of the SH- and Rayleigh-type PBAWs.

This paper describes the development of a new laser probe for radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices. The Sagnac interferometer was introduced for the selective detection of RF vertical motion associated with RF SAW/BAW propagation and vibration. A high-pass characteristic of the interferometer makes the measurement very insusceptible to the low-frequency vibration. Combining such a feature with the advanced scanning technique and optimized detection system, we were successfully able to maximize the scanning speed without sacrificing the signal-to-noise ratio and sensitivity of the measurement. The system was applied to the characterization of RF SAW/BAW devices and showed its effectiveness in device diagnosis.

This paper reviews physical properties of piezoelectric boundary acoustic waves (PBAWs) and their application to miniature and high performance RF filters. First, basic properties of PBAWs are discussed. It is shown that PBAWs are supported in various structures provided that highly piezoelectric material(s) are employed as structural member(s). For example, PBAWs are trapped near the electrode region in the SiO2/heavy grating electrode/rot. YX-LN structure. This means that PBAW properties in the structure are independent of the SiO2 layer thickness. This is a significant advantage for mass production. Rot. YX-LN possesses piezoelectric coupling with the Rayleigh-type PBAW as well as the SH-type one. It is shown that the coupling can be negligible when the device structure is properly designed. The PBAW devices employing SiO2/Au electrodes/0-15 degrees YX-LN are now being mass-produced. Because of the removed cavity from the chip surface, the packaged device size can be reduced dramatically. The minimum insertion loss achieved is comparable to that of conventional SAW filters in a relatively large device size. The SiO2 layer is effective in achieving the improved temperature coefficient of frequency.

The paper describes the development of an integrated software environment for the image processing of complex data captured by phase-sensitive SAW/BAW laser probe system. By the software using graphical user interface, efficient diagnosis of SAW/BAW devices is made possible. The developed software displays the amplitude and phase images of acquired results, and a motion movie of the field pattern. The 2D fact Fourier transform (FFT) and inverse FFT (IFFT) are performed just by clicking a related button on the interface. Prior to the FFT and/or IFFT operation, we can extract or withdraw specific data in x-y or beta(x)-beta(y) space by mouse operation on the image. This makes the wave domain analysis such as selective visualization of spurious resonance modes most handy.

This paper discusses a technique to suppress spurious transverse mode responses appearing in ultra-wideband SAW resonators fabricated on a Cugrating/ 15 degrees YX-LiNbO3 structure. The basic idea of the technique is inserting length- and width-weighted dummy electrodes between a bus-bar and interdigital electrodes. For practical device design, an analysis was made to show how the profile (field distribution) of both dominant and spurious transverse modes depends on the length and width (equivalent to SAW velocity) of the dummy electrodes. IDT-type SAW resonators were fabricated on a Cu-grating/15 degrees YX-LiNbO3 structure using the length- and width-weighted dummy electrodes. The experimental results were in good agreement with the theoretical analysis and prediction, showing that the proposed technique is effective in suppressing the spurious responses caused by the transverse modes.

This paper proposes use of pitch-modulated interdigital transducers (IDTs) and reflectors for the realization of low-loss and wideband longitudinally coupled double-mode surface acoustic wave (DMS) filters. This technique offers drastic improvement of the device performances through the introduction of a sufficient number of degrees of freedom in the DMS filter design. Namely, the pass-band becomes wide and flat, and insertion loss can be reduced through the suppression of the bulk acoustic wave (BAW) scattering. First, it is shown how the BAW scattering loss can be reduced by the use of the pitch-modulated structure. The DIMS filter with this structure is designed so that the frequency response becomes similar to that of the filter with the conventional unmodulated structure, and device performances are compared both theoretically and experimentally. It then is demonstrated how the total device performances are improved by the use of this technology when the device is designed optimally for given specifications. Adding to the reduced bulk wave scattering loss, various distinctive features offer drastic improvement of total device performances.

A high accuracy modeling methodology for electrical characteristics of transmission electrodes on SAW substrates is established. In order to design SAW filter accurately, it is necessary to extract precise SAW material parameters from the measurement value of the reference SAW resonator. When measuring the SAW resonator, transmission lines are needed for feeding to contact probes. De-embedding procedure, which removes the influence of transmission lines, is very important for accurate characterization of the SAW resonator.<br>In this paper, we apply the improved de-embedding procedure using SHORT, OPEN and THRU calibration patterns. The de-embedded transmission line is separated four parts and extracted the RLGC equivalent circuit model for each part. Furthermore, we derive the frequency characteristic of resistance element of the transmission line. Finally, de-embedding the transmission line accurately, we can get intrinsic characteristic of the SAW resonator. This method must be very useful to extract SAW material parameters and we can design SAW filters more effectively.

A droplet manipulator working with low driving power was developed by using the surface acoustic wave (SAW) technology. The manipulator was driven at a relatively high frequency of 350MHz to increase the SAW power density. First, a single phase unidirectional transducer (SPUDT) was designed. Because of its low insertion loss of 1.5 dB and high directivity of 10 dB, the SPUDT successfully conveyed a 100 nl water droplet with RF input power of 18 dBm (60 mW). Second, the SPUDT design was extended to a curved transducer to focus and launch the SAW energy into the narrow waveguide. Owing to the increased SAW power density, the required SAW power was reduced to 15 dBm (30 mW) for the 100 nl droplet manipulation. In addition, fabrication of liquid injectors was discussed for the formation of tiny droplet.

本研究では、低温合成が可能な水熱合成法を利用して超高品質のエピタキシャルPZT(チタン酸ジルコン酸鉛)薄膜を成膜した。DE-ヒステリシス曲線による強誘電性の評価と共に、厚み方向の超音波励振を利用した圧電特性をMasonの等価回路により評価した。測定では裏面反射により1～3GHzの間で7.29MHz間隔での共振―反共振ピークを検出し、予測と一致する結果を得た。

The preparation of piezoelectric AlN thin films of high quality onto diamond substrates using DC-TFTS method and its application to SHF SAW devices are discussed. FWHM (=3.4°) of the rocking curve of XRD suggested that the c-axes of AlN films may well align perpendicular to the film surface. Transversal filters based on Sezawa wave were fabricated to verify whether the prepared AlN/diamond structure can be applied to low loss SAW devices in an SHF range. The propagation loss was experimentally estimated to be 0.08 dB/λ at the centre frequency of 6.12 GHz. Further reduction in the propagation loss was attempted by using small-grain-diamond substrates.

This paper describes the development of the extended version of the FEM/SDA software for the characterisation of SAW propagation in layered substrate and overlayered structures. First, the newly developed software was applied to the characterisation of SAW propagation under an infinitely-long Al interdigital transducer (IDT) on rotated Y-cut LiTaO3/sapphire substrate structure. Because of the finite LiTaO3 thickness, a series of spurious resonances appears. It is shown that the excitation strength of the spurious resonances changes with frequency as well as the rotation angle, which reflects the frequency and rotation angle dependence of the energy leakage. Next, the analysis was carried out for SAWs propagating in an SiO2 layer/Al IDT/42 degrees YX-LiTaO3 structure. It is shown that the influence of the SiO2 layer is significantly dependent on the location where the SiO2 layer is deposited. That is, the SiO2 layer on the IDT electrodes tends to increase the SAW reflectivity, whereas the SiO2 layer sandwiching the grating electrodes in reduces the SAW reflectivity.

Numerical synthesis of frequency response is discussed for a ladder type filter consisting of ultra-wideband SAW resonators on Cu-grating/15 YX-LiNbO3 structure. For the synthesis, two parameters of each resonator, i.e., the static capacitance and resonant frequency were numerically optimised, while the capacitance ratio and figure of merit were fixed at specific values determined by substrates and grating electrodes employed. First, six-stage SAW ladder type filters having the passband width of 7 to 21% were designed. The result showed that the specified bandwidth is successfully synthesised. Next, a six-stage ladder type filter having the passband width of 8% was fabricated on Cu-grating/15 YX-LiNbO3 structure for experimental discussion. It was shown that the measured frequency response of the filter was in good agreement with the design, where some in-band spurious dips were removed by weighted dummy electrodes. By making analysis on the behaviour of resonant and anti-resonant frequencies of each resonator, it is shown that the method can be extended to the synthesis of filters having sophisticated frequency responses. The result suggested that the proposed method could become one of the powerful design tools for SAW ladder type filters with specified passband width.

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 &lt; 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-LiNbO3-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. (c) 2006 Elsevier B. V. All rights reserved.

This paper proposes a simple technique to suppress the reflection coefficients S-11 and S-22 of surface acoustic wave (SAW) filters. Two identical SAW filters are sandwiched in between two quadrature hybrids, where their two ports are used as input and output, and others are terminated by matched loads. First, it is shown by simulation that both vertical bar S-11 vertical bar and vertical bar S-22 vertical bar are suppressed to be less than -20 dB without deteriorating the transmission characteristics. Next, two hybrids using microstrip lines were fabricated, and two RF SAW filters for GSM850 were sandwiched in between them. The result showed that the maximum vertical bar S-11 vertical bar within the passband was improved from -12.5 dB to -21.7 dB, i.e., 9.2 dB suppression of vertical bar S-11 vertical bar was achieved by sacrificing only the insertion loss of less than 0.6 dB. We also attempted to replace the microstrip lines with lumped elements. In this case, the maximum vertical bar S-11 vertical bar within the passband was improved more than 7.5 dB with the increased insertion loss of less than 1.5 dB. Finally, simple discussion is given on the inclusion of the transformer function in the quadrature hybrid.

This paper describes the development of a high-speed laser probe system for surface acoustic wave (SAW) devices. A fast scanning rate of 2.5 kS/s is realized by continuous stage translation and successive acquisition of the detector output by a high-speed data-logger. Trigger pulses are generated from the output of a high-precision linear-scale installed in the translation stage and fed to the data-logger for the synchronization with the stage movement. The phase-sensitive, knife-edge method is used for the optical detection. This makes the system very unsusceptible to low-frequency mechanical vibration caused by the fast stage translation. The system is applied for the characterization of spurious resonance modes in SAW devices. In conjunction with skillful use of image processing in wavenumber domain, it is shown how the present system is effective in the diagnosis and development of SAW devices.

This paper aims at reducing the insertion loss of surface acoustic wave (SAW) filters with constant group delay using Cu electrodes based on resonant single-phase unidirectional transducers (RSPUDTs). Theoretical analysis indicates that the reflectivity of a Cu-electrode/128 degrees YX-LiNbO3 structure is about two times larger than that of an Al-electrode/128 degrees YX-LiNbO3 structure of the same thickness. The high reflectivity of Cu electrodes is effective in increasing the variable range in the reflectivity, which provides more degrees of freedom in the optimization of RSPUDT. A constant-group-delay filter is designed and fabricated. Experimental results are in fairly good agreement with the design; group delay deviation of 30 ns is realized over the range of +/- 6.5 MHz at the center frequency of 490 MHz where the minimum insertion loss is 6.1 dB.

This paper presents an innovative design technique to achieve a low-loss SAW filter by Quasi-slanted finger interdigital transducers (Q-SFITs). As subfilters, resonant single-phase unidirectional transducers (RSPUDTs) with constant group delay are used. The distances and apertures of subfilters are optimized to realize Q-SFIT filters with low loss, wide bandwidth and small group delay deviation. By this procedure, a Q-SFIT filter is designed and fabricated on a 128 degrees YX-LiNbO3 substrate. The experimental results agree with the simulation, and the minimum insertion loss of 5.2 dB and small group delay deviation of 56 ns were simultaneously achieved.