Session: 5H SAW SYSTEM APPLICATIONS Chair: B. R. Potter Vectron International. 5H-1 8:30 a.m.

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1 Session: 5H SAW SYSTEM APPLICATIONS Chair: B. R. Potter Vectron International 5H-1 8:30 a.m. DESIGN OF MINIATURIZED RF SAW DUPLEXER PACKAGE H. DONG* 1,T.X.WU 1,C.A.FINCH 2, B. P ABBOTT 2, and K. S. CHEEMA 2, 1 University of Central Florida, Orlando, FL, 2 SAWTEK Inc., Apopka, FL. Corresponding hdong99@yahoo.com Surface acoustic wave (SAW) technology has been featured in numerous publications for more than a decade because of the performance advantages and design flexibility. With the increasing of the frequency, the electrical effects become more important. The accurate prediction of the frequency response relies on a combination of good acoustic modeling techniques, rigorous die and package parasitic model. This paper provides a comprehensive methodology for the analysis and design of the RF SAW duplexer package. The Ansoft High Frequency Structure Simulator (HFSS), based on the finite element method (FEM), is used to model the duplexer package. The port definition in HFSS for the complex package structure is discussed. The die parasitics model is obtained by Agilent s Momentum. Then we combine the die parasitics model with the resonators to get the die results. We assemble the package results and die results in Agilent s Advanced Design System (ADS) to get the total response. Simulation and measurement results are compared and good agreement is found. Small insertion loss and high isolation in stop band are very important specifications in the SAW duplexer package design. Based on this methodology, several new ideas are proposed and improvements of the isolation can be achieved. The technique developed in this paper reduces the design cycle time significantly and can be applied to various RF SAW device packages. 5H-2 8:45 a.m. PHASE ACCURACY FOR SAW RFID TAG DEVICES C. S. HARTMANN*, P. BROWN, and J. BELLAMY, RF SAW, Inc., Richardson, TX, USA. Corresponding chartmann@rfsaw.com The Global SAW Tag [1] is projected to be a very large-volume SAW device application. Relative phase accuracy of ±0.05 radians is required for the impulse response of the Global SAW Tag after subtracting the temperature drift, varying delay time, and other known effects. This corresponds to a relative accuracy of 2.5 ppm since a typical tag device has more than radians 347

2 of phase at 2.45 GHz. The method for achieving this performance will be presented for a 128-bit tag device with 32 in-line reflector taps. By using a single acoustic channel, all tag pulses must travel along the same physical path on the substrate surface. The method also makes use of a unique floating-electrode reflector structure, compensation of multiple-phase distortion effects, high-quality SAW wafer processing, and precise definition of the requirements for the phase accuracy of an RFID system. [1] C. S. Hartmann, A Global SAW ID Tag with Large Data Capacity, Proc IEEE Ultrasonics Symposium, pp H-3 9:00 a.m. HIGH ATTENUATION SAW IF FILTER FOR DIGITAL TERRESTRIAL TV H. WACHI*, T. TAKEZAKI, S. MITOBE, M. KOSHINO, and Y. EBATA, Fujitsu Media Devices Limited. Corresponding wachi@fmd.ed.fujitsu.co.jp In digital terrestrial broadcasting system, adjacent high-level signals of coexistence analog system act as a spurious signal, which causes the generation of intermodulation and a bit error after digital demodulation. Therefore, a band pass filter with a large out-of-band rejection is required in IF stage in digital TV receiver set. Generally, for a high-rejection transversal SAW filter with apodized transducer, overlapped length of comb finger tends to be very narrow in sidelobe portion of apodized transducer. In spite of compensating diffraction effect, the high suppression level cannot be realized due to second order effects in such narrow overlapped region. The developed SAW filter has dual-track structure and keeps total aperture length that equals to that of conventional single-track structure. The filter characteristics of each track are different from each other and objective frequency response of each track is determined as overlapped length in side-lobe region become larger. Moreover, every overlapped length of each track, which is settled at the same position in propagation direction, is designed as synthesized SAW intensity generated each position is similar to conventional single-track case. The developed filter achieves 50dB attenuation level with 20-lambda total aperture length. The improved attenuation level, which is similar to the case of 4-times larger aperture of conventional filter, has been successfully realized with conventional aperture length. 5H-4 9:15 a.m. UNIDIRECTIONAL SAW TRANSDUCER FOR GHZ FREQUENCIES ON 128 LINBO 3 S. LEHTONEN* 1, V. P. PLESSKY 1,2, C. S. HARTMANN 3, and M. M. SALOMAA 1, 1 Helsinki University of Technology, Espoo, Finland, 2 GVR Trade SA, Bevaix, Switzerland, 3 RF SAW, Inc., Dallas, TX, USA. Corresponding saku@focus.hut.fi 348

3 A SPUDT structure employing λ/4 and wider electrodes is introduced. The considerable difference between the rather low reflectivity of short-circuited λ/4 electrodes and the high reflectivity of floating electrodes on 128 LiNbO 3 is exploited. In particular, λ/2-wide second-harmonic reflectors can be used [1]. To minimize the reflectivity of the IDTs, the metallisation ratio in the transducer sections can be chosen depending on the aluminium thickness used (h/λ = 2-6%). A few topologies containing 3 or more electrodes per section are proposed. In this way it is possible to optimize the piezoelectric coupling and reflectivity per wavelength. With increased number of electrodes per section, the proposed SPUDT structure gradually transforms into a group-type unidirectional IDT. Utilizing the structure introduced, the properties of a simple filter for the 2.45 GHz ISM band consisting of two identical SPUDT transducers with their forward directions towards each other have been numerically studied [2]. The simulated performance of a matched filter is very promising. The IL is approximately 3 db, and the 3 db bandwidth is about 100 MHz. SAW filters, tags, sensors and other SAW devices utilizing these unidirectional transducers, operating at 2.45 GHz, will have critical dimensions of about 0.4 µm, accessible for mass production with standard optical lithography. The low loss level, being directly related to the reading distance, is a crucial factor for SAW-tags. [1] S. Lehtonen, V. P. Plessky, and M. M. Salomaa, Short reflectors operating at the fundamental and second harmonics on 128 LiNbO 3, Proc IEEE Ultrasonics Symp., pp [2] J. Ribbe, On the coupling of integral equations and finite elements / Fourier modes for the simulation of piezoelectric surface acoustic wave components, PhD Thesis, CMAP / Ecole Polytechnique, H-5 9:30 a.m. A COMPACT AND HIGH OPTICAL TRANSMISSION SAW TOUCH SCREEN WITH ZNO THIN-FILM PIEZOELECTRIC TRANSDUCERS T. KATSUKI*, S. SANO, Y. TAKAHASHI, and F. NAKAZAWA, Fujitsu Laboratories Ltd. Corresponding t katsuki@jp.fujitsu.com We developed a compact and high optical transmission touch screen using surface acoustic waves (SAWs) generated by ZnO thin-film piezoelectric transducers. It has a 200 dots per inch (dpi) resolution and a 1.4 mm frame width. The V-shaped comb-type electrode structure enables a highly accurate detection of touched positions on the screen even for narrow frame widths. Using a single glass substrate enables a 98 % optical transmission and provides a scratchproof screen. We used a single phase transducer (SPT) constructed with a ZnO piezoelectric thin film sandwiched between a planar electrode and a comb-type electrode for reducing the ZnO film thickness. The optimum film thickness varies with the period length of the comb-type electrode. When an inter digital transducer 349

4 (IDT) structure has no counter electrode, the electromechanical coupling factor reaches a maximum value at approximately h/λ=0.4, where h is the ZnO film thickness and λ is the period length of the comb-type electrode. The SPT structure reaches a local maximum at approximately h/λ=0.02. Therefore, we designed the ZnO thin film thickness to meet the local maximum, and we reduced the thickness to 1/20. This method reduces fabrication time and costs. The ZnO thin film is deposited on an aluminum-metal planar electrode by RF magnetron reactive sputtering with a ZnO ceramic sputter target. Before depositing the ZnO thin film, the electrode surface is dry-etched with Ar plasma to remove the natural oxide film. Doping copper into aluminum electrodes prevents hillocks caused by the high temperature during the ZnO sputtering. This way, the ZnO film on the aluminum metal electrode has a high quality and efficiently converts electric signals into SAWs. The developed touch screen has a high resolution, a high optical transmission, a scratchproof screen, and it is compact. The screen is ideally suited for mobile information and communication applications such as PDAs or cellular phones. 5H-6 9:45 a.m. DESIGN CONSIDERATION ON ULTRA-WIDEBAND-SAW DEVICES OPERATING AT GHZ FREQUENCY RANGE H. YOSHIDA*, C. KANESHIRO, K. KOH, and K. HOHKAWA, Kanagawa Institute of Technology. Corresponding koh@ele.kanagawa-it.ac.jp Relative bandwidths of most SAW devices are restricted within a few percent, because of a large insertion loss due to a small coupling coefficient of piezoelectric material. The advent of a new material with a high coupling coefficient, such as KNbO3, and/or the co-integration capability with the semiconductor active devises would open new application areas, such as analog signal processing circuits and UWB communication band. In this paper, we investigate performance of wideband SAW devices with the bandwidth more than 300 to 500 MHz at a center frequency around a few GHz. For estimating basic problems on ultra wide band devices at a high frequency range, we adopted responses of a correlator with phase-coded transducer having a special phase code, derived by the Golay complementary code. We intend to apply these devices on the sensing device and local area CDMA communication systems with the pulse position spread spectrum signal modulation scheme. We clarify difference of the effect of so-called second order effect on these devices from that of narrowband width devices and propose an electrode structure of IDTs for realizing a high performance device. We report a basic experimental result of a wideband SAW correlator with phase-coded transducers. We also designed and estimated programmable devices, in which an array of semiconductor active device is connected to each tapping electrodes of the correlation device. In this study, we assumed two types of device, such as a linear and a nonlinear, which would be fabricated by using the epitaxial lift off (ELO) film bonding technology. We show 350

5 simulation results on these devices including noise characteristics, and discuss problems and potentials in a near future. Session: 1I THERAPY Chair: G. ter Haar Institute for Cancer Research, Royal Marsden Hospital 1I-1 10:30 a.m. FEASIBILITY OF HAEMOSTASIS IN PROSTATE USING A FLAT TRANS-URETHRAL TRANSDUCER C. LAFON*, S. CHESNAIS, Y. THEILLRE, J. Y. CHAPELON, and D. CATHIG- NOL, Inserm U556, Lyon, France. Corresponding lafon@lyon.inserm.fr The objective of this work is to demonstrate the feasibility of trans-urethral application of collimated high intensity ultrasound in order to coagulate blood vessels in prostate. A preliminary study was performed for assessing the density, position and size of blood vessels in human prostate. The diameter of the vessels ranged between 0.1 and 1mm in a window 1cm deep from the urethra. This study resulted in the choice of rabbit liver as a complying animal model. The coagulating tool is a flat 6x10mm 2 transducer compatible with trans-urethral application. It operates at a frequency of 10MHz for a good trade-off between therapeutic depth and temperature elevation. The external face of the transducer was water-cooled during sonication. The applicator was coupled with an imaging probe. Doppler and conventional ultrasound imaging were performed before and after treatment and used to evaluate haemostasis. The effect of intensity, exposure duration and angular step between elementary exposures on therapeutic depth and thrombosed vessels density was studied. A mixture of ink and gelatine was perfused in the liver after treatment for differentiating permeable from thrombosed vessels. The therapeutic depth ranged from 6 to 10mm. Hyperechoic spots were observed on sonograms for a few minutes right after treatment and a permanent hypoechoic zone remains in the treated zone. It corresponds in size to the histologicaly assessed zone of coagulation. A significant fall in Doppler signal amplitude immediately after treatment demonstrated the applicator s ability to achieve haemostasis. The coagulation rate obtained by dividing the vessel density of the treated sample by the vessel density of the controls ranged between 51% and 99%. We demonstrated that a miniature flat ultrasound 10MHz-transducer can be used to coagulate blood vessels with a diameter less than 1mm and located at a distance less than 1cm from the organ surface. This makes our transducer suitable for trans-urethral application of high intensity ultrasound to coagulate prostatic tissues and vessels. The permanent hyposignal on ultrasound scan was most likely due to temperature dependence of attenuation and back scattering coefficients. This work has been supported by a grant from EDAP, Vaulx-en-Velin, France. 351