M. Tayyib “Spread spectrum signals application in resonant ultrasonic spectroscopy measurements” doctoral dissertation defence

Author, Institution: Muhammad Tayyib, Kaunas University of Technology

Science area, field of science: Technological Sciences, Electrical and Electronic Engineering, T001

Research supervisor: Prof. Dr. Linas Svilainis (Kaunas University of Technology, Electrical and Electronic Engineering, T001)

Dissertation Defence Board of Electrical and Electronic Engineering Science Field:
Prof. Dr. Elena Jasiūnienė (Kaunas University of Technology, Technological Sciences, Electrical and Electronic Engineering, T001) – chairperson
Assoc. Prof. Dr. Luca De Marchi (University of Bologna, Italy, Technological Sciences, Electrical and Electronic Engineering, T001)
Prof. Dr. Vaidotas Marozas (Kaunas University of Technology, Technological Sciences, Electrical and Electronic Engineering, T001)
Prof. Dr. Marco Ricci (Sapienza University of Rome, Italy, Technological Sciences, Electrical and Electronic Engineering, T001)
Senior Researcher Dr. Egidijus Žukauskas (Kaunas University of Technology, Technological Sciences, Measurement Engineering, T010)

Dissertation defence meeting will be at Rectorate Hall of Kaunas University of Technology (K. Donelaičio 73-402, Kaunas)

The doctoral dissertation is available at the library of Kaunas University of Technology (Gedimino 50, Kaunas) and on the internet: M. Tayyib el. dissertation.pdf

© M. Tayyib, 2026 “The text of the thesis may not be copied, distributed, published, made public, including by making it publicly available on computer networks (Internet), reproduced in any form or by any means, including, but not limited to, electronic, mechanical or other means. Pursuant to Article 25(1) of the Law on Copyright and Related Rights of the Republic of Lithuania, a person with a disability who has difficulties in reading a document of a thesis published on the Internet, and insofar as this is justified by a particular disability, shall request that the document be made available in an alternative form by e-mail to doktorantura@ktu.lt.”

Annotation: This thesis addresses a key limitation in air-coupled resonant ultrasound spectroscopy: the severe degradation of measurement accuracy caused by overlapping reflections when using long-duration spread-spectrum signals for improved signal-to-noise ratio. The main contribution is a comprehensive solution consisting of three interconnected innovations:

1. SNR-optimized APWP signals — a generalized spectral shaping technique that compensates for frequency-dependent transduction losses and maximizes usable bandwidth (from ~480 kHz to 670 kHz at –20 dB).
2. Inverse filter-based pulse compression with gating and decompression to resolve overlapping reflections in long chirps (up to 350 µs), reducing bias errors.
3. ResidualUNet1D deep learning model for automated reflection separation, achieving up to 45 dB reminder energy for short signals and ~32 dB for 300 µs signals.

The proposed methods were validated through simulations on Vitis vinifera leaves and experiments on polycarbonate plates. Results show consistent and significant reduction in bias errors for velocity, attenuation, density, and thickness compared to conventional LFM, NLFM, and pulse excitations. The work demonstrates that spectral loss compensation combined with overlapping signal resolution enables high-accuracy air-coupled TRUS using only a single transducer pair.