European Telecommunications Standards Institute

We present UGR-MINDVOICE, the University of Granada (UGR) multimodal electroencephalography (EEG) and audio dataset for overt and covert speech in Iberian Spanish intended for basic neuroscience and brain-computer interface (BCI) research. The dataset features EEG and audio recordings from 15 native Spanish speakers engaged in both overt and covert speech production tasks. This dataset is unique in its inclusion of all Spanish phonemes and a diverse set of words spanning various semantic categories and different usage frequencies. Validation of the dataset confirmed the presence of robust sensory event-related potentials, including the visual P100 and the auditory N1 (N100), indicating reliable early perceptual processing and sustained participant attention to both visual and auditory stimuli. Additionally, the EEG data were classified into rest, covert speech, and overt speech conditions with an accuracy of 81.40%, demonstrating active participant engagement in the tasks. By providing synchronised EEG and audio data for overt speech, along with EEG data for the same stimuli during covert speech, UGR-MINDVOICE constitutes a valuable resource for advancing research in basic neuroscience and brain-computer interfaces, particularly in the domain of silent speech communication. The full dataset is openly available on the Open Science Framework (OSF) ( https://osf.io/6sh5d ), and all accompanying code and analysis scripts are provided in a public GitHub repository ( https://github.com/owaismujtaba/mind-voice ). • UGR-MINDVOICE is the first open-access EEG-audio dataset designed specifically for Iberian Spanish, capturing both overt and covert speech across all Spanish phonemes and a wide range of lexical items. • The dataset supports the development of brain-computer interfaces for silent speech decoding, offering a non-invasive alternative to intracranial methods and enabling communication for individuals with severe motor impairments. • With high-density EEG, multimodal stimuli (text, audio, and images), and carefully controlled tasks, UGR-MINDVOICE enables robust modelling of speech production and perception.

Self-diplexing stacked-patch antennas (SD-SPAs) are attractive for multi-band satellite navigation applications due to their compact form factor and elimination of external diplexers. However, conventional designs exhibit limited inter-port isolation (∼15 dB), which typically restricts their operation to receive-only scenarios, especially in high-power transceiver systems. This paper introduces a dual-metallic-cavity architecture that achieves high-performance self-diplexed operation through a hierarchical hybrid decoupling strategy. Two independent cavities confine the lower- and upper-band resonant modes, while concentric conductive rings on the upper-band ground plane further reduce inter-band coupling. The upper cavity incorporates a miniaturized annular-notched patch stacked with a cross-shaped parasitic element, increasing fractional bandwidth while the reduced footprint of the crosshead inherently limits UB-to-LB leakage compared to larger-area elements. Rotation of the upper-band radiator about the vertical axis provides additional fine adjustment of inter-band isolation. Experimental results demonstrate inter-port isolation ranging from 22.1 dB to 34.5 dB for the lower band and from 37.5 dB to 46.1 dB for the upper band, while maintaining radiation efficiency, circular polarization purity, phase-center stability, and group delay performance. These findings confirm that the dual-cavity architecture enables high-power transmit/receive operation for multi-band navigation systems without compromising essential electromagnetic characteristics.

We study the fundamental properties of pointwise semi-Lipschitz functions between asymmetric spaces, which are the natural asymmetric counterpart of pointwise Lipschitz functions. We also study the influence that partial symmetries of a given space may have on the behavior of pointwise semi-Lipschitz functions defined on it. Furthermore, we are interested in characterizing the pointwise semi-Lipschitz structure of an asymmetric space in terms of real-valued pointwise semi-Lipschitz functions defined on it. By using two algebras of functions naturally associated to our spaces of pointwise real-valued semi-Lipschitz functions, we are able to provide two Banach–Stone-type results in this context. In fact, these results are obtained as consequences of a general Banach–Stone-type theorem of topological nature, stated for abstract function spaces, which is quite flexible and can be applied to many spaces of continuous functions over metric and asymmetric spaces.

This paper focuses on the parameterization of the multipath propagation model (MPM) for indoor broadband power line communications (PLC), which up to now has been established in an heuristic way. The MPM model was initially proposed in the PLC context for outdoor channels in the band up to 20 MHz, but its number of parameters becomes extremely large when used to model indoor channel frequency responses (CFR), which are much more frequency-selective than outdoor ones, and the band is extended to 80 MHz. This work proposes a fitting procedure that addresses this problem. It allows determining the model parameters that yield the best fit to each channel of a large database of single-input single-output (SISO) experimental measurements acquired in typical home premises of different European countries. Then, the statistics of the MPM parameters are analyzed. The study unveils the relation between the model parameters and the main characteristics of the actual CFR like the frequency selectivity and the average attenuation. It also estimates the probability density function (PDF) of each parameter and proposes a fitting distribution for each of them. Moreover, the relationship among the main parameters of the model, as well as their impact on the performance of PLC communication systems are also explored. Provided results can be helpful for the development of MPM-based models for indoor broadband PLC.

This article presents a beamforming network based on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$6 \times 6$</tex> Nolen matrix using lumped elements throughout the entire matrix, on a single layer in the UHF band. The methodology for designing branch-line couplers and phase shifters is based on the equivalence between transmission lines and lumped elements. The large number of ports implies more accurate design considerations and optimizations, which are explained in detail first. The matrix was designed on Roger 4003 substrate using SMD-type lumped elements in a 1005 package. The design's central frequency is 922 MHz, but the operating frequency is guaranteed to be between 905 and 930 MHz, which is within the ISM band. The simulated results are in agreement with the ideal values for the differential phase, with a maximum dispersion of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm \mathbf{1 5}^{\boldsymbol{\circ}}$</tex>. The maximum insertion loss is 2.6 dB due to the lumped elements. The radiation patterns at the output ports indicate good results in terms of beam scanning. The overall matrix size is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10.9 \times 5.8 ~\text{cm}$</tex>. Hence, this feeding network exhibits the correct behavior for a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$6 \times 6$</tex> Nolen matrix, and its footprint is eleven times smaller than it would be if implemented using microstrip lines.