SAW Comb Research Articles

Multifrequency characterization of viscoelastic polymers and vapor sensing based on SAW oscillators

Simplified relations for the changes in SAW velocity and attenuation due to thin polymer coatings and vapor sorption are presented by making analytic approximations to the complex theoretical model developed earlier by Martin et al. [Anal. Chem. 66 (14) (1994) 2201–2219]. The approximate velocity relation is accurate within 4% for the film thicknesses up to 20% of the acoustic wavelength in the polymer film, and is useful for analyzing the mass loading, swelling and viscoelastic effects in SAW vapor sensors. The approximate attenuation relation is accurate within 20% for very thin films, (less than 2% of the acoustic wavelength in the film). Based on these relations, a new procedure for determination of polymer viscoelastic properties is described that exploits the frequency dependence of the velocity and attenuation perturbations, and employs multifrequency measurement on the same SAW platform. Expressions for individual contributions from the mass loading, film swelling and viscoelastic effects in SAW vapor sensors are derived, and their implications for the sensor design and operation are discussed. Also, a new SAW comb filter design is proposed that offers possibility for multimode SAW oscillator operation over a decade of frequency variation, and illustrates feasibility for experimental realization of wide bandwidth multifrequency SAW platforms.

SAW Comb Filter Designs for Multi-Frequency Chemical Sensors and Polymer Viscoelasticity Probes by Combining Remez-Rung Ladder and FM Chirp Transducers

not Available.

Tunable SAW comb filter

The tunable saw comb filter is described. The principle of the filter is based on changing the phase shift in the closed loop of an amplifier by means of a variable mangetoacoustic SAW delay line.

Effect of Li/Nb Ratio on the SAW Velocity of 128°Y–X LiNbO3 Wafers

The effects of the composition on the SAW velocity and the electro-mechanical coupling constant (k2) of 128°-rotated Y-cut X-propagating (128°Y–X) LiNbO3 wafers have been quantitatively investigated. The composition of the wafer was determined from the Curie temperature detected by DTA measurements and the SAW velocity from the measurements on a 70 MHz band SAW Comb filter. From the experiments, both the SAW velocity and the k2 obviously depended on the composition of the wafer. Variations of the SAW velocity and the k2 per 1 Li2O mol% were 43.4 m/sec and 0.43%. At the composition of 48.6 Li2O mol% which was reported as the congruent melt composition by Carruthers et al.,1) the SAW velocity and the k2 were 3986 m/sec and 5.8%, respectively.

TV Tuning Systems with SAW Comb Filter

We have successfully developed two TV tuning systems which apply a SAW comb filter device in a new way. One is an automatic channel indicating system and the other is a frequency synthesizer. The SAW comb filter has comb peaks at the frequencies where channels are allocated. A channel number is recognized by counting the number of comb peaks which the local oscillator signal of a tuner goes through. The SAW comb filter has a minimum electrode width of 1 mu m. It has four sets of IDT's to cover all TV channels, fabricated on a single chip.

TV Tuning Systems with SAW Comb Filter

TV Tuning Systems with SAW Comb Filter