Showing papers on "Interdigital transducer published in 2007"

Surface acoustic wave concentration of particle and bioparticle suspensions

Abstract: A rapid particle concentration method in a sessile droplet has been developed using asymmetric surface acoustic wave (SAW) propagation on a substrate upon which the droplet is placed. Due to the asymmetry in the SAW propagation, azimuthal bulk liquid recirculation (acoustic streaming) is generated. Once the local particle concentration is sufficiently high within a particular streamline of the acoustic streaming convective flow, shear-induced migration gives rise to an inward radial force that concentrates the particles at the centre of the droplet. In this paper, a SAW device consists of a 0.75-mm thick, 127.68° Y–X-axis-rotated cut, X-propagating LiNbO3 for a substrate and an interdigital transducer electrode (IDT) with 25 straight finger pairs in a simple repeating pattern, 12 mm aperture, and a wavelength of λ = 440 μm was patterned on the substrate. The IDT was then driven with a sinusoidal signal at the resonance frequency f 0 of 8.611 MHz. To investigate the effect of particle type and size on the concentration process, three types of particles were used in this study, including fluorescent particles (1 μm), polystyrene microspheres (3, 6, 20, 45 μm), and living yeast cells (10–20 μm). Different RF powers were applied ranging from 120 to 510 mW. The concentration processes occurs within 2 to 20 s, depending on the particle size, type and input radio frequency (RF) power, much faster than currently available particle concentration mechanisms due to the large convective velocities achieved using the SAW device. Moreover, this concentration method is efficient, concentrating the particles into an aggregate one-tenth the size of the original droplet. Most importantly, bioparticles can also be concentrated by this method; we have verified that yeast cells are not lysed by the SAW radiation during concentration. By using the rapid concentration process described in this work, the breadth of applications and measurement sensitivity of SAW biosensor systems should be greatly enhanced.

Micromachined thin film plate acoustic resonators utilizing the lowest order symmetric lamb wave mode

Abstract: Thin film integrated circuits compatible resonant structures using the lowest order symmetric Lamb wave propagating in thin aluminum nitride (AlN) film membranes have been studied. The 2-mum thick, highly c-oriented AlN piezoelectric films have been grown on silicon by pulsed, direct-current magnetron reactive sputter deposition. The films were deposited at room temperature and had typical full-width, half-maximum value of the rocking curve of about 2 degrees. Thin film plate acoustic resonators were designed and micromachined using low resolution photolithography and deep silicon etching. Plate waves, having a 12-mum wavelength, were excited by means of both interdigital (IDT) and longitudinal wave transducers using lateral field excitation (LW-LFE), and reflected by periodical aluminum-strip gratings deposited on top of the membrane. The existence of a frequency stopband and strong grating reflectivity have been theoretically predicted and experimentally observed. One-port resonator designs having varying cavity lengths and transducer topology were fabricated and characterized. A quality factor exceeding 3000 has been demonstrated at frequencies of about 885 MHz. The IDT based film plate acoustic resonators (FPAR) technology proved to be preferable when lower costs and higher Qs are pursued. The LW-LFE-based FPAR technology offers higher excitation efficiency at costs comparable to that of the thin film bulk acoustic wave resonator (FBAR) technology

Optimal design on SAW sensor for wireless pressure measurement based on reflective delay line

Abstract: This paper presents optimal design on wireless pressure micro-sensor based on surface acoustic wave (SAW) reflective delay line. Using the coupling-of-modes (COM) analysis, the device was simulated, and the effect of reflector configuration and interdigital transducer (IDT) structure on the performance of the devices was studied. From the COM simulation results, a 440 MHz SAW-based pressure sensor based on a reflective delay line on 41 ◦ YX LiNbO3 with shorted circuit grating reflectors and single-phase unidirectional transducers (SPUDT) structure was developed experimentally. Using the network analyzer, the SAW sensor was wirelessly characterized, and the experiment results were well matched with simulation data. Sharp reflection peaks, low insertion loss and few spurious signals between the peaks were observed. Obtained pressure sensitivity was 2.67 ◦ /kPa.

Suppression of Transverse Mode Responses in Ultra-Wideband SAW Resonators Fabricated on a Cu-Grating/15°YX-LiNbO 3 Structure

Abstract: This paper discusses a technique to suppress spurious transverse mode responses appearing in ultra-wideband SAW resonators fabricated on a Cu- grating/15degYX-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/15degYX-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.

Annular interdigital transducer focuses piezoelectric surface waves to a single point

Abstract: We propose and demonstrate experimentally the concept of the annular interdigital transducer that focuses acoustic waves on the surface of a piezoelectric material to a single, diffraction-limited, spot. The shape of the transducing fingers follows the wave surface. Experiments conducted on lithium niobate substrates evidence that the generated surface waves converge to the center of the transducer, producing a spot that shows a large concentration of acoustic energy. This concept is of practical significance to design new intense microacoustic sources, for instance for enhanced acouto-optical interactions.

Acoustic wave device and filter using the same

Abstract: An acoustic wave device includes a piezoelectric substrate, a resonator having comb electrodes that are provided above the piezoelectric substrate and excite an acoustic wave, and a capacitor that is provided above the piezoelectric substrate and is connected in series or parallel with the resonator, the capacitor including electrodes that horizontally face each other above the piezoelectric substrate. The electrodes of the capacitor are further from the piezoelectric substrate than the comb electrodes of the resonator.

Lamb wave type frequency device and method thereof

Abstract: A Lamb wave type high frequency device comprises: a piezoelectric substrate (20); an interdigital transducer (IDT) electrode (30) formed on a first main surface of the piezoelectric substrate; a reinforcing substrate (50) connected to a second main surface of the piezoelectric substrate; a space portion (54) formed in one of the piezoelectric substrate and the reinforcing substrate, an area of the space portion being larger than a region in which a Lamb wave is propagated; and a connecting surface (52) formed in a periphery of the space portion.

Non-hysteresis and perfect linear piezoelectric performance of a multilayered lithium niobate actuator

Abstract: A LiNbO3 piezoelectric single crystal is expected to have superior linearity and non-hysteresis in piezoelectric performance. By optimizing the cutting angle (36° Y-cut), the thickness of the piezoelectric constant becomes as large as 38 pC/N, and a multilayered structure enables the piezoelectric displacement to become larger. The effective piezoelectric coefficient becomes comparable to that of a PZT actuator. To realize an ultra-high precise positioning system, a multilayered LiNbO3 actuator was fabricated to examine the piezoelectric vibration characteristic and linearity. By investigating the relationship between applied voltage and the piezoelectric displacement, it was confirmed that this actuator had superior linearity and non-hysteresis performance. The effective piezoelectric constant was measured at 380 pC/N, and the maximum displacement at 700 V was more than 250 nm.

Detection and High-Precision Positioning of Liquid Droplets Using SAW Systems

Abstract: The capability to accurately handle liquids in small volumes is a key point for the development of lab-on-chip devices. In this paper, we investigate an application of surface acoustic waves (SAW) for positioning micro-droplets. A SAW device based on a 2 times 2 matrix of inter-digital transducers (IDTs) has been fabricated on a (YXl)/128deg LiNbO3 substrate, which implies displacement and detection in two dimensions of droplets atop a flat surface. Each IDT operates at a given frequency, allowing for an easy addressing of the active channel. Furthermore, very low cross-talk effects were observed as no frequency mixing arose in our device. Continuous as well as pulsed excitations of the IDTs have been studied, yielding, respectively, continuous and step-by-step droplet displacement modes. In addition, we also have used these two excitation types to control the velocity and the position of the droplets. We also have developed a theoretical analysis of the detection mode, which has been validated by experimental assessment.

Method and apparatus for imaging utilizing an ultrasonic imaging sensor array

Abstract: The subject invention pertains to a piezoelectric device structure for improved acoustic wave sensing and/or generation, and process for making same. The piezoelectric thin film field effect transducer can be a thin film transistor (TFT) with either a piezoelectric film gate or a composite gate having a dielectric film and a piezoelectric film. The TFT structure can be either a top gate device or a bottom gate device. In an embodiment, the piezoelectric device structure can be used to form an array of piezoelectric thin film field effect transducers. A TFT switch can drive each piezoelectric transducer in the array. The piezoelectric transducers can both generate and sense acoustic waves. In a sensing mode, a signal from an acoustic wave can be collected at a readout terminal of the piezoelectric transducer. In a generating mode, an excitation signal can be applied across the piezoelectric transducer while the switch is 'on'.

8E-6 Extended FEM/SDA Software for Characterising Surface Acoustic Wave Propagation in Multi-Layered Structures

Abstract: 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/42degYX-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 SiO, layer sandwiching the grating electrodes in reduces the SAW reflectivity.

Application of RF Varactor Using Ba x Sr 1-x TiO 3 /TiO 2 /HR-Si Substrate for Reconfigurable Radio

Abstract: In this paper, the potential feasibility of integrating BaxSr1-xTiO3 (BST) films into Si wafer by adopting tunable interdigital capacitor (IDC) with TiO2 thin film buffer layer and a RF tunable active bandpass filter (BPF) using BST based capacitor are proposed. TiO2 as a buffer layer is grown onto Si substrate by atomic layer deposition (ALD) and the interdigital capacitor on BST(500 nm)/TiO2(50 nm)/HR-Si is fabricated. BST interdigital tunable capacitor integrated on HR-Si substrate with high tunability and low loss tangent are characterized for their microwave performances. BST/TiO2/HR-Si IDC shows much enhanced tunability values of 40% and commutation quality factor (CQF) of 56.71. A resonator consists of an active capacitance circuit together with a BST varactor. The active capacitor is made of a field effect transistor (FET) that exhibits negative resistance as well as capacitance. The measured second order active BPF shows bandwidth of 110 MHz, insertion loss of about 1 dB at the 1.81 GHz center frequency and tuning frequency of 230 MHz (1.81-2.04 GHz).

Operation Mechanism of Double-Mode Surface Acoustic Wave Filters with Pitch-Modulated IDTs and Reflectors

Abstract: One of the authors (KH) previously proposed pitch-modulated interdigital transducers (IDTs) and reflectors for developing low-loss and wideband longitudinally coupled double-mode SAW (DMS) filters. This paper discusses how a wide and flat passband is realized by applying the pitch-modulated IDTs and reflectors to DMS filters. It is shown that the pitch-modulated structure enables one to adjust the location of multiple resonance frequencies simultaneously by varying an effective reflective position with frequency. That is, the IDTs are pitch-modulated so that the outer portion has slightly larger pitch than the inside, and the pitch of the outermost reflectors is made largest. Accordingly, higher-order SAW resonances occur between the two pitch-modulated IDTs. The outer portion of each IDT acts as a reflector, and the inner portion is mainly responsible for SAW excitation. Lower-order SAW resonances occur between the two reflectors.

Surface acoustic wave resonator, surface acoustic wave filter using the surface acoustic wave resonator, and antenna duplexer

Abstract: The present invention provides a surface acoustic wave resonator capable of improving the leak of a surface acoustic wave in the transverse direction and reducing the spurious and having superior characteristics. In a surface acoustic wave filter according to the present invention, an interdigital transducer electrode and reflector electrodes are formed on a piezoelectric substrate, and a SiO 2 thin film is further formed thereon. The interdigital transducer electrode includes a bus-bar electrode region, a dummy electrode region and a finger overlap region, and the SiO 2 thin film is removed from upper sections of the bus-bar electrode regions in the interdigital transducer electrode.

Bio surface acoustic wave (saw) resonator amplification for detection of a target analyte

Abstract: The present invention relates generally to a signal amplification method for a SAW resonator microsensor for analyzing test samples, containing target analyte including proteins and nucleic acids. The invention relates to at least one surface acoustic wave resonator unit comprising a plurality of three-dimensional interdigital transducer electrode (IDTE) and reflector micro channels located on a piezoelectric substrate surface. The invention further relates to a change of solid/liquid volume ratio in said three- dimensional micro channels; said changes of the liquid/solid volume ratio can be di rected correlated to the target analyte concentration in a test sample.

Combination of e-Beam Lithography and of High Velocity AlN/Diamond-Layered Structure for SAW Filters in X Band

Abstract: In this work, we report on the fabrication results of surface acoustic wave (SAW) devices operating at frequencies up to 8 GHz. In previous work, we have shown that high acoustic velocities (9 to 12 km/s) are obtained from the layered AIN/diamond structure. The interdigital transducers (IDT) made of aluminum with resolutions up to 250 nm were successfully patterned on AIN/diamond-layered structures with an adapted technological process. The uniformity and periodicity of IDT were confirmed by Held emission scanning electron microscopy and atomic force microscopy analyses. A highly oriented (002) piezoelectric aluminum nitride thin film was deposited on the nucleation side of the CVD diamond by magnetron sputtering technique. The X-ray diffraction effectuated on the AIN/diamond-layered structure exhibits high intensity peaks related to the (002) AlN and (111) diamond orientations. According to the calculated dispersion curves of velocity and the electromechanical coupling coefficient (K2), the AlN layer thickness was chosen in order to combine high velocity and high K2. Experimental data extracted from the fabricated SAW devices match with theoretical values quite well.

Surface acoustic wave excitation device

Abstract: [Problems] To provide a surface acoustic wave excitation device for efficiently exciting the surface acoustic wave on the surface of a material such as glass having free size and shape for making mechanical vibration available. [Means to Solve the Problems] The surface acoustic wave excitation device according to the present invention comprises a non-piezoelectric member 30 such as glass, a piezoelectric member 20 , interdigital transducers 11 interposed between the non-piezoelectric member 30 and the piezoelectric member 20 , and pre-pressurizing means 42 for pressing the piezoelectric member 20 onto the non-piezoelectric member 30 by way of the interdigital transducers. Alternating voltage is applied to the interdigital transducers 11 for exciting the surface acoustic wave on the non-piezoelectric member 30 . Standing waves are generated in the piezoelectric member 20 by applying alternating voltage to the interdigital transducers 11 , thereby allowing alternating strains to propagate to the non-piezoelectric member 30 such as a glass substrate or the like by way of the electrodes 11 and exciting the surface acoustic wave for making mechanical vibration of the non-piezoelectric member 30 available.

SAW Filters Composed of Interdigital Schottky and Ohmic Contacts on AlGaN/GaN Heterostructures

Abstract: We proposed surface acoustic wave (SAW) filters composed of interdigital Schottky and ohmic contacts on AlGaN/GaN heterostructures. The contribution of the SAWs appeared in the radio frequency characteristics of the filters when the Schottky contacts were reverse biased. Onsets of the SAW signals and the threshold voltage of simultaneously fabricated high-electron mobility transistors were found to almost agree with one another. We also obtained an isolation of >40 dB. These results suggest that SAW-based functional devices are likely to be realized using AlGaN/GaN heterostructures with interdigital Schottky and ohmic contacts

Monolithically Integrated Tandem Waveguide-Type Acoustooptic Modulator Driven by Surface Acoustic Waves

Abstract: A waveguide-type acoustooptic modulator (AOM) using coplanar AO coupling due to a surface acoustic wave (SAW), that is, Bragg diffraction, in a tapered crossed-channel proton-exchanged (PE) optical waveguide on a 128°-rotated Y-cut LiNbO3 substrate for an optical wavelength of 1.55 µm has been proposed. In this study, a monolithically integrated tandem waveguide-type AOM driven by SAW was designed and fabricated. The structure considered was a 2×4 optical switch, in which the input ports of two second 1×2 switches were connected to the two output ports of the first 2×2 switch on the same substrate. An interdigital transducer (IDT) with a period length of 32 µm and an overlap length of 2 mm was fabricated in the first and second stages of the AO interaction region. Diffraction efficiency was measured at a driving frequency of approximately 120 MHz. A diffraction efficiency of approximately 90% was obtained for each stage. When both stages were driven at the same frequency, a peak diffraction efficiency of 63% was obtained. Furthermore, the optical frequency shifts for the sum of two driving frequencies and the difference frequency ranging from DC to 5 MHz were observed.

Surface acoustic wave device

Abstract: PROBLEM TO BE SOLVED: To provide a surface acoustic wave device capable of establishing compatibility between excellent propagation characteristics and wide band of frequency characteristics. SOLUTION: A transversal filter 10 as one type of a surface acoustic wave device has a sapphire substrate 11, a propagation layer 12 formed of GaN thin film on the sapphire substrate 11, an input side interdigital transducer 13 formed on the surface of the propagation layer 12, and an output side interdigital transducer 14. In this filter 10, the interdigital transducers 13 and 14 are formed so that a a11-20} direction being a direction where a surface acoustic wave to be excited by the interdigital transducers 13, 14 propagates at the lowest velocity in the surface of the propagation layer 12 may be aligned with the arrangement direction of the electrode fingers of the interdigital transducers 13, 14, and the line width and arrangement pitch of the electrode fingers may be changed in a direction orthogonal to the arrangement direction. COPYRIGHT: (C)2007,JPO&INPIT

Ring waveguide resonator on surface acoustic waves

Abstract: A simple regular electrode structure for surface acoustic wave (SAW) devices is proposed. The structure consists of an interdigital transducer in the form of a ring placed on the Z cut of a hexagonal piezoelectric crystal. Finite thickness electrodes produce the known slowing effect for a SAW in comparison with this SAW on a free surface. The closed “slow” electrode region with the “fast” surrounding region forms an open waveguide resonator structure with the acoustic field concentrated in the electrode region. If the radius of the structure is large enough for a given wavelength, an acceptable level of radiation losses can be reached. The electrical admittance of such resonator does not have sidelobes.

Low-Loss and Wide-Band Double-Mode Surface Acoustic Wave Filters Using Pitch-Modulated Interdigital Transducers and Reflectors

Abstract: 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 DMS 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.

Anisotropic acousto-optic diffraction by leaky wave radiation in ZX-LiNbO3

Abstract: The anisotropic light diffraction by bulk acoustic waves (BAWs) radiated by an interdigital transducer (IDT) operating at the leaky surface acoustic wave resonance in ZX-lithium niobate has been experimentally studied at an optical wavelength of 633nm in the range of acoustic frequencies from 35to190MHz. The possibility of optical probing of the IDT-radiated BAW properties is demonstrated. The experimentally determined values of the BAW propagation angle and velocity are 25° and 4050m∕s, respectively.

Power Flow Angles for Slanted Finger Surface Acoustic Wave Filters on Langasite Substrate

Abstract: Power flow angles (PFAs) on a langasite (LGS) substrate with Euler angles of (0°, 138.5°, ψ), ψ=25.7 to 27.7° are investigated for slanted finger interdigital transducer (SFIT) surface acoustic wave (SAW) filters by an electrical and optical methods. In the electrical method, several tilted SFIT SAW filters with different tilt angles for (0°, 138.5°, ψ) LGS substrates were designed, and the frequency responses of the filters were measured. In the optical method, the PFAs were directly measured by optical probing for a parallel interdigital transducer (IDT) with wide propagation area on the substrate. As a result, a good correlation between electrical and optical measurements of the PFAs is obtained, but the calculated PFAs are slightly different from the measured PFAs. A good frequency response of a tilted 380 MHz SFIT SAW filter with an appropriate tilt angle corresponding to the PFA on the substrate is obtained even though the aperture is small.

Surface acoustic wave packages and methods of forming same

Abstract: A sensor package generally includes a substrate and one or more sensing elements, located on a surface of the substrate. A lid, such as for example a glass cap, is coupled to the substrate such that the lid and substrate define a sealed cavity accommodating the sensing element(s). The lid has at least one conductive via or well electrically coupled to the sensing element(s) inside the cavity and arranged so as to provide an electrical connection to the exterior of the lid for connecting with external circuitry. The substrate can be a piezoelectric substrate and each sensing element can consist of an interdigital transducer such that the substrate and interdigital transducer(s) define a surface acoustic wave sensor. A surface acoustic wave sensor system for sensing torque includes the sensor package and leads wire bonded to the conductive vias for attaching the sensor package to an antenna.

Acoustic wave device and method for fabricating the same

Abstract: A surface acoustic wave device includes a piezoelectric substrate, at least one interdigital transducer (IDT) electrode provided on the piezoelectric substrate, and an insulator layer to improve a temperature characteristic arranged so as to cover the IDT electrode. When a surface of the insulator layer is classified into a first surface region under which the IDT electrode is positioned and a second surface region under which no IDT electrode is positioned, the surface of the insulator layer in at least one portion of the second surface region is higher than the surface of the insulator layer from the piezoelectric substrate in at least one portion of the first surface region by at least about 0.001λ, where the wavelength of an acoustic wave is λ.

P6G-4 High Q-factor STW-Resonators on AT-Cut of Quartz

Abstract: Surface transverse wave-resonators with resonant frequency near 1900 MHz on AT-cut of quartz with different periods of interdigital transducer and reflectors are reported It is established that for metal thickness to wavelength ratio 19% the use of reflectors with gradually increasing periodicity gives the highest resonance Q-factor Application of uniform reflectors with center frequency immediately shifted down to set the resonance at the center of reflection stopband results in 92% decrease of Q-factor that is attributed to the bulk wave scattering at the break of periodicity Fabricated test samples of one-port resonators show unloaded Q-factors up to 7200

Optimal Design of an RSPUDT-Based SAW Filter with Constant Group Delay

Abstract: This paper describes the application of resonant single-phase unidirectional transducers (RSPUDTs) to the development of low-loss SAW filters with constant group delay in transition bands as well as in the passband. A low-loss SAW filter with constant group delay was designed and fabricated on a 128degYX-LiNbO3 substrate. Experimental results were in good agreement with the design; the group delay deviation of 20 ns was realized over the range of plusmn8 MHz at the center frequency of 512 MHz. The minimum insertion loss and -3 dB bandwidth were 4.3 dB and 8.5 MHz, respectively. The application of this technique is also extended to develop high-performance wideband filters employing quasi-slanted interdigital transducers.

Double-resonance SAW filters

Abstract: A novel surface acoustic wave filter on a leaky-wave substrate is studied. It features a hiccup-type resonance occurring around a distributed gap between two long interdigital transducers. Compared to a classical coupled resonator filter, it enables a relatively narrow passband (1% to 2% of center frequency) with low insertion loss, steep skirts, and improved suppression levels. The structure consists of long transducers having the number of fingers greater than 1/K2 and 1/K, where K2 is the coupling coefficient of the substrate material and K is the reflectivity per wavelength, separated with short transducer sections constituting a distributed gap. A strong, localized resonance is formed in the gap region, in addition to the resonance arising in the long structures - hence, the name double-resonance filter. The substrate studied here is 42deg-rotated lithium tantalite. We show experimental results for both single-ended and unbalanced-to-balanced filters at 1.6 GHz, having a minimum insertion loss of 1.07 dB, suppressions of 30 dB, and absolute -3-dB bandwidth of 29 MHz (1.9% of the center frequency). For the balanced device, the amplitude imbalance over the passband ranges from -0.6 dB to 2 dB arid the phase imbalance from 1deg to 4.5deg. Furthermore, we have measured the acoustical power distributions using a scanning laser interferometer, and we compare these results with the profiles simulated using a coupling-of-modes model

Super Low Velocity/Piezoelectric Substrate Structure with High Reflections and Applications for Surface Acoustic Wave Wide Band Resonators and Low-Loss Unidirectional Transducer Filters

Abstract: In this paper, the propagation characteristics and reflectivities of TeO2 grating/128° Y–X LiNbO3, 36° Y–X LiTaO3, and 5° Y–X LiNbO3 are analyzed and applied to resonators and, conventional and dispersive unidirectional transducers. Theoretical results of thin film gratings show the large impedance ratio, for example, thin film grating shows r=0.96 at a thickness of H/λ=0.01, for 128° Y–X LiNbO3. The experimental results for an interdigital transducer (IDT) resonator of thin film/Al/128° Y–X LiNbO3 with N=100,W=20λ,H/λ=0.01 show an admittance of 1.0 S. The experimental unidirectional transducer filter using thin film TeO2 (H/λ=0.015)/Al/128° Y–X LiNbO3 show a 1.6 dB insertion loss at 500 MHz without matching. Moreover filters with the phase linear, flat wide band, and low loss characteristics are developed using dispersive unidirectional IDT.