Hiromi Yatsuda

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

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.

Modeling of parasitic effects for flip-chip SAW filters

An equivalent circuit with parasitics is described to predict stop band frequency response of flip-chip surface acoustic wave (SAW) filters, 3.2/spl times/2.5 mm/sup 2/ and 2.5/spl times/2.0 mm/sup 2/ in size. An input to output coupling capacitance and a common ground inductor provide a distinct trap response in the stop band. In order to improve the stop band response of the filter, a design technique utilizing parasitics is proposed.

Liquid-Phase Shear Horizontal Surface Acoustic Wave Immunosensor

In this paper, we describe liquid-phase immunosensors based on shear horizontal surface acoustic waves (SH-SAWs), which can be directly dipped into a liquid. The sensor devices are fabricated using an SH-SAW delay line on quartz and LiTaO3 substrates, which is composed of a transmitting floating electrode unidirectional transducer (FEUDT), receiving FEUDT, and a biochemical reaction area between them. These FEUDTs are protected from liquids by a glass lid and epoxy walls, which are constructed using a photolithography technique. Therefore, the sensor devices can be directly dipped into a liquid and a liquid can be directly applied onto the surface of the sensor devices. In order to evaluate basic characteristics of the sensor devices, glycerol–water mixture liquids of different viscosities were used. For evaluations of their applicability to immunoassay, human serum albumin antigen–antibody reactions were investigated.

Surface Acoustic Wave Filter Using Floating Electrode Slanted Finger Unidirectional Transducers

This paper describes a wide-band surface acoustic wave (SAW) filter designed to achieve large stop-band attenuation. The SAW filters using slanted finger interdigital transducers are suitable for mid- or wide-band filters. To achieve a stop-band attenuation of more than 80 dB, two SAW filters using slanted finger unidirectional transducers (SFUDTs) were cascaded. Since these SFUDT filters have center-to-center distances that differ by one-fourth of the acoustic wavelength at the center frequency, the triple transit echo was effectively compensated. A cascaded-pair SFUDT SAW filter with a fractional bandwidth of 15 percent was designed and fabricated on a 128°Y-X LiNbO3 substrate. An insertion loss of 14 dB, amplitude ripples of 0.5 dB and stop-band attenuation of 80 dB or more were achieved.

IIDT type low-loss SAW filters with improved stopband rejection in the range of 1 to 2 GHz

Interdigitated interdigital transducer (IIDT)-type surface acoustic wave (SAW) filters with suppressed sidelobes and reduced insertion losses are described. The filters are composed of multiple withdrawal-weighted IDTs in different withdrawal positions. An 878-MHz filter composed of 13 IDTs was designed by this method. This filter has a minimum insertion loss of 1.6 dB and a stopband rejection of about 30 dB. Three filters with center frequencies of 0.9 GHz, 1.5 GHz, and 1.9 GHz were fabricated using the lift-off process. Their frequency responses are almost the same, and the insertion losses are less than 3 dB.<<ETX>>

Automatic computer-aided design of SAW filters using slanted finger interdigital transducers

This paper describes a design procedure for surface acoustic wave (SAW) filters using slanted finger interdigital transducers (SFIT) that are suitable for mid-band or wideband applications. The SFITs cannot represent the impulse response directly, in contrast to apodized IDTs. A design method for SFITs based on a building-block approach in the frequency domain is described. An automatic computer-aided design tool for SFIT filters has been achieved. The SFIT filters can be designed using a withdrawal weighting for stop-band responses, an aperture weighting for pass-band amplitude responses, and a distance weighting for pass-band phase responses. In addition, a SFIT pattern for photo mask can be automatically designed using this tool. Using this tool, an SFIT filter with a relative bandwidth of 15% was designed on an x-cut 112y-direction LiTaO/sub 3/ substrate.

Miniaturized SAW filters using a flip-chip technique

This paper describes a miniature surface acoustic wave (SAW) filter, 3.2/spl times/2.5/spl times/0.9 mm/sup 3/, which is applicable for radio frequency (RF) stage filters in mobile phones. The SAW filter is reduced in size by using a flip-chip assembly technique. The technique uses gold bumps on the SAW chip and gold-gold thermosonic face-down bonding. The gold bumps are formed onto the wafer by a conventional wire bonding machine using gold wire. The thermosonic face-down bonding enables the connection of gold bumps on the SAW chip, with gold metallized pads, on a ceramic package at a temperature below 200/spl deg/C. This bonding ensures that the SAW chip is fixed mechanically, and connected electrically, with the package. Frequency responses of a 950-MHz flip-chip SAW filter are compared with responses of a SAW filter with a conventional package. The results of reliability tests for flip-chip SAW filters are shown.This paper describes a miniature SAW filter, 3.2×2.5×0.9 mm3, which is applicable for RF-stage filters in mobile phones. The SAW filter is reduced in size by using a flip-chip assembly technique. The technique uses gold bumps on the SAW chip and gold-gold thermosonic face-down bonding. This bonding provides that a SAW chip is fixed mechanically and connected electrically with a package. A frequency response of a 950 MHz flip-chip SAW filter and results of reliability tests are shown

Analysis of Mass Loading Effect on Guided Shear Horizontal Surface Acoustic Wave on Liquid/Au/Quartz Structure for Biosensor Application

A numerical analysis of a shear horizontal surface acoustic wave (SH-SAW) immunoassay biosensor has been investigated. The numerical calculation method proposed by Campbell and Jones has generally been used to calculate SAW propagation characteristics. In this paper, a numerical calculation method for SH-SAW propagation characteristics, which is a modified method of Campbell and Jones involving the effect of liquid viscosity is applied to quartz. A mass loading sensitivity of a 250 MHz SH-SAW delay-line biosensor was calculated and compared with the experimental results. It can be concluded from the results that viscosity sensitivity is dominant over mass loading sensitivity for 250 MHz SH-SAW biosensors.

Flip-chip STW filters and frequency trimming method

This paper describes 2.4 GHz and 3.5 GHz flip-chip narrow-band filters using surface transverse waves (STWs) on quartz for oscillator applications. A Q of about 1300 and insertion losses of 3 dB and 5 dB are achieved for 2.4 GHz and 3.5 GHz flip-chip STW filters, respectively. Also, oscillator characteristics using the flip-chip STW filters are presented. In addition, trimming methods for flip-chip STW filters are described. We have succeeded in frequency trimming using CF/sub 4/ chemistry, in situ monitoring the center frequency for flip-chip STW filters with 3.2 mm/spl times/2.5 mm ceramic packages.

Repetitive Immunoassay with a Surface Acoustic Wave Device and a Highly Stable Protein Monolayer for On-Site Monitoring of Airborne Dust Mite Allergens

This work describes a sensor to be incorporated into the on-site monitoring system of airborne house dust mite (HDM) allergens. A surface acoustic wave (SAW) device was combined with self-assembled monolayers of a highly stable antibody capture protein on the SAW surface that have high resistance to pH change. A sandwich assay was used to measure a HDM allergen, Der f 1 derived from Dermatophagoides farinae. Capture antibodies were cross-linked to a protein G based capture layer (ORLA85) on the sensor surface, thereby only Der f 1 and detection antibodies were regenerated by changing pH, resulting in fast repetition of the measurement. The sensor was characterized through 10 repetitive measurements of Der f 1, which demonstrated high reproducibility of the sensor with the coefficient of variation of 5.6%. The limit of detection (LOD) of the sensor was 6.1 ng·mL(-1), encompassing the standard (20 ng·mL(-1)) set by the World Health Organization. Negligible sensor outputs were observed for five different major allergens including other HDM allergens which tend to have cross-reactivity to Der f 1 and their mixtures with Der f 1. Finally, the sensor lifetime was evaluated by conducting three measurements per day, and the sensor output did not substantially change for 4 days. These characteristics make the SAW immunosensor a promising candidate for incorporation into on-site allergen monitoring systems.