Biomedical subjects

Alexander N Kalashnikov

Publications and source records attributed to Alexander N Kalashnikov.

3 recordsLinked to original sources

PubMed2005

New architectures for feedthrough SAW recursive devices.

This paper presents an analysis of a new type of feedthrough recursive surface acoustic wave (SAW) device. The device combines a conventional SAW structure with positive feedback in a way that allows use of selective properties of the SAW structure, control of the central frequency and bandwidth, achieving significantly higher quality factors for given dimensions of the structure, and reduction of the sidelobe level. Several possible implementations are discussed from a simple one that uses external circuitry to the most advanced that includes digital supervisory control. Equations are presented that relate the central frequency, bandwidth, and sidelobe level to the parameters of the SAW structure and feedback loop. The simulation results were found to be in good agreement with experimental data. These data show the control of the central frequency within 1%, a 10-fold increase in the quality factor compared to the original SAW structure, and a reduction of the side-lobe level by 20 dB irrespective of the influence of second order effects and random manufacturing fluctuations.

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PubMed2005

Errors and uncertainties in the measurement of ultrasonic wave attenuation and phase velocity.

This paper presents an analysis of the error generation mechanisms that affect the accuracy of measurements of ultrasonic wave attenuation coefficient and phase velocity as functions of frequency. In the first stage of the analysis we show that electronic system noise, expressed in the frequency domain, maps into errors in the attenuation and the phase velocity spectra in a highly nonlinear way; the condition for minimum error is when the total measured attenuation is around 1 Neper. The maximum measurable total attenuation has a practical limit of around 6 Nepers and the minimum measurable value is around 0.1 Neper. In the second part of the paper we consider electronic noise as the primary source of measurement error; errors in attenuation result from additive noise whereas errors in phase velocity result from both additive noise and system timing jitter. Quantization noise can be neglected if the amplitude of the additive noise is comparable with the quantization step, and coherent averaging is employed. Experimental results are presented which confirm the relationship between electronic noise and measurement errors. The analytical technique is applicable to the design of ultrasonic spectrometers, formal assessment of the accuracy of ultrasonic measurements, and the optimization of signal processing procedures to achieve a specified accuracy.

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PubMed2002

The influence of fabrication errors on the stopband magnitude responses of SAW devices.

This article is devoted to the analysis of the influence of manufacturing errors on the magnitude responses of surface acoustic wave (SAW) devices. Analytical analysis of these random errors provides statistical distributions of the relevant responses and their parameters. It allows significant reduction in the modeling computations compared to the Monte Carlo method, and it provides possibilities for further analytical analysis. After the application of the statistical analysis to different potential structures of SAW devices, it is possible to choose the least sensitive one during the design process without the need of costly trials. Experimental analysis confirmed the existence of some of the features predicted both theoretically and by modeling. The experimental procedure for the evaluation of the fabrication error variances is described. The application of these results to the design process of the SAW devices allows simplification of the requirements for the manufacturing equipment and/or improvement of the devices' parameters, especially stopband suppression.

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