Multi-transit Echo Suppression for Passive Wireless Surface Acoustic Wave Sensors Using 3rd Harmonic Unidirectional Transducers and Walsh-Hadamard-like Reflectors

Author

Luis Manuel Rodriguez Cordoves, University of Central Florida

Keywords

Multi transit echo, double transit echo, echo suppression, saw, surface acoustic wave sensor, passive wireless sensor, walsh hadamard, walsh hadamard like saw reflectors, tunable antenna, reflective delay line sensor, ofc, cdma, bpsk, am bpsk, pwm bpsk, third harmonic coupling of modes model, 3rd harmonic spudt, 3rd harmonic gudt, nelder mead optimization

Abstract

A passive wireless surface acoustic wave sensor of a delay-line type is composed of an antenna, a transducer that converts the EM signal into a surface acoustic wave, and a set of acoustic reflectors that reflect the incoming signal back out through the antenna. A cavity forms between the transducer and the reflectors, trapping energy and causing multiple unwanted echoes. The work in this dissertation aims to reduce the unwanted echoes so that only the main transit signal is left--the signal of interest with sensor information. The contributions of this dissertation include reflective delay-line device response in the form of an infinite impulse response (IIR) filter. This may be used in the future to subtract out unwanted echoes via post-processing. However, this dissertation will use a physical approach to echo suppression by using a unidirectional transducer. Thus a unidirectional transducer is used and also optimized for 3rd harmonic operation. Both the directionality and the coupling of the 3rd harmonic optimized SPUDT are improved over a standard electrode width controlled (EWC) SPUDT. New type of reflectors for the reflective delay-line device are also presented. These use BPSK type coding, similar to that of the Walsh-Hadamard codes. Two types are presented, variable reflectivity and variable chip-lengths. The COM model is used to simulate devices and compare the predicted echo suppression level to that of fabricated devices. Finally, a device is mounted on a tunable antenna and the echo is suppressed on a wireless operating device.

Notes

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Graduation Date

2017

Semester

Fall

Advisor

Malocha, Donald

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Electrical Engineering and Computer Science

Format

application/pdf

Identifier

CFE0006912

URL

http://purl.fcla.edu/fcla/etd/CFE0006912

Language

English

Release Date

December 2017

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

STARS Citation

Rodriguez Cordoves, Luis Manuel, "Multi-transit Echo Suppression for Passive Wireless Surface Acoustic Wave Sensors Using 3rd Harmonic Unidirectional Transducers and Walsh-Hadamard-like Reflectors" (2017). Electronic Theses and Dissertations. 6679.
https://stars.library.ucf.edu/etd/6679