A method is discussed for achieving a wideband low-loss longitudinally coupled double mode surface acoustic wave (SAW) (DMS) filter using a leaky SAW on a 36 degrees Y-X LiTaO/sub 3/ and 64 degrees Y-X LiNbO/sub 3/ substrate with a high electromechanical coupling factor. Its characteristics are analyzed by computer simulation. With the use of the first-mode and third-mode resonance on a 64 degrees Y-X LiNbO/sub 3/ substrate and the selection of the optimum values for the distance between input and output interdigital transducers (IDTs), the electrode film thickness and the input/output IDT pair number, it is possible to achieve favorable characteristics with a 1-dB bandwidth of 33 MHz, and insertion loss of 2.1 dB, and an attenuation in the rejection band of 28 approximately 38 dB. >

Wideband low loss double mode SAW filters

This paper gives a historical account of the development of Rayleigh-wave, or surface acoustic wave (SAW), devices for applications in electronics. The subject was spurred on initially by the requirements of pulse compression radar, and became a practical reality with the planar interdigital transducer, dating from 1965. The accessibility of the propagation path gave rise to substantial versatility, and a huge variety of devices were developed. Passive SAW devices are now ubiquitous, with applications ranging from professional radar and communications systems to consumer areas such as TV, pagers and mobile phones. The paper describes the extensive work, particularly in the 1970s, to investigate SAW propagation in crystalline media, including piezoelectric coupling diffraction and temperature effects. This led to identification of many suitable materials. Concurrently, many devices began development, including pulse compression filters, bandpass filters, resonators, oscillators, convolvers and matched filters for spread spectrum. In the 1970s, many of these became established in professional systems, and the SAW bandpass filter became a standard component for domestic TV. In the 1980s and 9Os, SAW responded to the new call for low-loss filters, particularly for mobile phones. With losses as low as 2 dB required (and subsequently achieved) at RF frequencies around 900 MHz, a raft of new technologies was developed. Additionally, for IF filters special techniques were evolved to reduce the physical size needed for narrow bandwidths. Such devices are now manufactured in very large quantities. In order to satisfy these needs, new types of surface wave, particularly transverse leaky waves, were investigated, and materials using such waves now have their place alongside more traditional materials.

History of SAW devices

New ultrasonic micromanipulation techniques for small particles in liquid based on the forces due to radiation pressure of high-frequency ultrasound are proposed, using VHF-range leaky wave transducers. The proposed manipulator has the advantages of the efficient generation of high-frequency ultrasonic waves into very small quantities of liquid containing small particles such as biomaterials, and the isolation of electrodes of the transducer from the liquid. Transportation and trapping of 100-µm-diameter small glass spheres in water are confirmed by preliminary experiments at a frequency of 49 MHz and acoustic intensity of about 8 mW/mm2.

Ultrasonic Micromanipulation of Small Particles in Liquid

The properties of piezoelectric leaky surface waves (PLSWs) in LiNbO/sub 3/, LiTaO/sub 3/, quartz, etc. are summarized. Applications of leaky surface waves, (e.g., in filters with a low-loss and wide bandwidth, voltage-controllable oscillators with a wide bandwidth for mobile communications systems, and temperature stable oscillators) are presented. In particular, it is shown that PLSWs have better properties than surface acoustic waves (SAWs) and that the boundary between metal and free surfaces is important for low-loss devices. Possible future applications of leaky surface waves are described. >

Applications for piezoelectric leaky surface waves

The development of sensors using surface acoustic wave (SAW) devices has been attracting attention A shear horizontal SAW (SH-SAW) sensor can detect the properties and chemical reactions in liquids To realize practical applications of the SAW sensor, it is necessary to discuss its properties In this paper, SH-SAW sensors with a floating electrode unidirectional transducer (FEUDT) or an interdigital transducer (IDT) are compared and the insertion loss and phase characteristics are measured Also, the phase shift between sample and reference liquids is evaluated The results indicate that the SH-SAW sensor with the FEUDT is suitable for liquid measurements The SH-SAW sensor with the FEUDT is then mounted in a newly developed SH-SAW sensing system The system configuration is the same as that of a vector voltmeter measurement system However, circuits have been developed that reduce its size Using this system, several liquids are measured The obtained results agree well with the theoretical values

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Development of a Shear Horizontal Surface Acoustic Wave Sensor System for Liquids with a Floating Electrode Unidirectional Transducer

A new single-phase unidirectional transducer utilising the difference between excitation and reflection positions caused by the floating electrodes of open and short metal strips inserted into the interdigital transducer within a half wavelength is described.

New low-loss SAW filter using internal floating electrode reflection types of single-phase unidirectional transducer

A new single-phase unidirectional transducer utilising the difference between excitation and reflection positions caused by the change of the electromechanical coupling coefficient within a half or one wavelength is described.

H. Furuyashiki

Papers

New low-loss SAW filter using internal floating electrode reflection types of single-phase unidirectional transducer

Low-loss SAW filter using internal reflection types of single-phase unidirectional transducer