A. Aleksandrovas “Arbitrary position and width pulse sequences for ultrasonic imaging and measurements” doctoral thesis defence

Author, Institution: Arturas Aleksandrovas, Kaunas University of Technology

Science area, field of science: Technological Sciences, Electrical and Electronic Engineering 01T

Scientific Supervisor: Prof. Dr. Linas Svilainis (Kaunas University of Technology, Technological Sciences, Electrical and Electronics Engineering – 01T)

Scientific Advisor: Assoc. Prof. Dr. Alberto Rodriguez Martinez (Miguel Hernandez University of Elche, Technological Sciences, Electrical and Electronics Engineering – 01T)

Dissertation Defence Board of Electrical and Electronics Engineering Science Field:
Prof. Dr. Liudas Mažeika (Kaunas University of Technology, Technological Sciences, Electrical and Electronics Engineering – 01T), chairman,
Dr. Jorge Camacho (Spanish National Research Council (CSIC), Technological Sciences, Electrical and Electronics Engineering – 01T),
Prof. Dr. Luca de Marchi (University of Bologna, Technological Sciences, Electrical and Electronics Engineering – 01T),
Prof. Dr. Vaidotas Marozas (Kaunas University of Technology, Technological Sciences, Electrical and Electronics Engineering – 01T),
Prof. Dr. Dangirutis Navikas (Kaunas University of Technology, Technological Sciences, Electrical and Electronics Engineering – 01T).

 The doctoral dissertation is available at the library of Kaunas University of Technology (K. Donelaičio St. 20, Kaunas).

Annotation:
The quality of the ultrasonic measurements is determined by the received signal energy, bandwidth and correlation properties. Ultrasonic transducers and signal propagation alters the spectral content of signals, the signal-to-noise ratio and correlation properties decrease. Conventional signals do not allow these losses to be corrected or inefficiently exploit the amplitude-time range dedicated for the excitation, excitation electronics are complex. New rectangular spread spectrum excitation signals have been proposed: arbitrary position and width pulse sequences (APWP). The novelty of the proposed APWP approach is that the optimization of the APWP sequence accounts the system transmission function, thus enhancing the desired signal properties. Signals combine the useful properties of rectangular pulses and spread spectrum signals, allow to control the correlation properties and spectral shape, do not require complex excitation electronics, and efficiently utilize the amplitude-time range dedicated for the excitation.
The proposed signals provide an opportunity to improve the measurement quality when measuring flow, distance or thickness. The results of the work are also applicable in imaging, because the wider spectrum yields a better resolution, while smaller sidelobes and a higher signal-to-noise ratio allow to increase the contrast. Signals are extremely effective in spectroscopy when seeking to maximize the spectral coverage, its smoothness and uniform signal-to-noise ratio over the frequency range.