Abstract
Research on Programmable Electromagnetic Surfaces has gained considerable attention as an enabling technology for 6G communications, particularly at millimeter-wave and sub-THz bands. However, RISs face challenges related to the need for high-performance reconfigurable techniques that offer compact size and reduced power consumption at high frequencies. Moreover, the experimental characterization of unit cell performance using a waveguide remains a challenging issue. This paper discusses the design and performance analysis of a 1-bit reconfigurable unit cell at the Dband using non-volatile reconfigurable technology. The efficiency analysis of the unit cell was performed using periodic boundary conditions and waveguide configurations to mitigate simulation risks and validate the proposed design at the unit cell level. All simulation configurations confirmed an operational bandwidth of 25.65 GHz across the 147.8-173.45 GHz range, with a reflection loss of less than 1 dB and a phase difference within 180 degrees +/- 20 degrees.

Abstract
A comparative analysis of Ka and D-band unit cells is presented using a Waveguide Simulator and infinite array models with a Floquet port. Initially, a single-unit cell design is employed with a tapered transition section. Subsequently, a 1 x 2-unit cell is designed and integrated into standard rectangular waveguides WR-34 and WR-7. For the Ka-band, the results obtained from both models exhibit excellent agreement in terms of magnitude and phase. In the D-band, the 1 x 2-unit cell demonstrated low loss for both techniques, and the phase responses were reasonably accurate with differences of less than 40 degrees. At such high frequencies (145-175 GHz), the Waveguide Simulator offers a viable solution for assessing the behavior of the unit cell without the need for a full array.

Abstract
This paper addresses two challenges that are intertwined and are key in informing signal processing methods restoring natural (voiced) speech from whispered speech. The first challenge involves characterizing and modeling the evolution of the harmonic phase/magnitude structure of a sequence of individual pitch periods in a voiced region of natural speech comprising sustained or co-articulated vowels. A novel algorithm segmenting individual pitch pulses is proposed, which is then used to obtain illustrative results highlighting important differences between sustained and co-articulated vowels, and suggesting practical synthetic voicing approaches. The second challenge involves model-based synthetic voicing restoration in real-time and on-the-fly. Three implementation alternatives are described that differ in their signal reconstruction approaches: frequency-domain, combined frequency- and time-domain, and physiologically inspired filtering of glottal excitation pulses individually generated. The three alternatives are compared objectively using illustrative examples, and subjectively using the results of listening tests involving synthetic voicing of sustained and co-articulated vowels in word context. © 2025 Elsevier B.V., All rights reserved.

Abstract
Whispers are common and essential for secondary communication. Nonetheless, individuals with aphonia, including laryngectomees, rely on whispers as their primary means of communication. Due to the distinct features between whispered and regular speech, debates have emerged in the field of speech recognition, highlighting the challenge of effectively converting between them. This study investigates the characteristics of whispered speech and proposes a system for converting whispered vowels into normal ones. The system is developed using multilayer perceptron networks and two types of generative adversarial networks. Three metrics are analyzed to evaluate the performance of the system: mel-cepstral distortion, root mean square error of the fundamental frequency, and accuracy with f1-score of a vowel classifier. Overall, the perceptron networks demonstrated better results, with no significant differences observed between male and female voices or the presence/absence of speech silence, except for improved accuracy in estimating the fundamental frequency during the conversion process. © 2025, Universidade do Porto - Faculdade de Engenharia. All rights reserved.

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