Design of In-phase and Quadrature Two Paths Space-Time-Modulated Metasurfaces

<p>Space-time-modulated metasurfaces can manipulate electromagnetic waves in space and frequency domain simultaneously. In this paper, an analytical design of space-time- modulated metasurfaces with modulation elements composed of two paths, In-phase (I) and Quadrature (Q), is proposed. The model is derived analytically, the space/frequency domain manipulations are achieved by designing the dimension and time sequence of I and Q paths. In the specular reflection direction, an objective frequency shift of the reflected first order harmonic can be obtained. While, in other directions, the opposite first order harmonic can be easily controlled by changing the dimension of I/Q paths and the objective first order harmonic remains unchanged. Furthermore, with a small dimension of I/Q paths, the first order harmonic can be used for beam scanning by pre-designing the start time of the modulation element. To realize the space-time-modulated metasurface with the required periodically time-varying responses, 2-bit unit-cells loaded with dynamically switchable pin diodes are employed as I/Q modulation. Both analytical and numerical results demonstrate that space and frequency domain manipulations of the reflected fields by the first order harmonics can be simultaneously obtained. The proposed designs have potential applications in wireless communications, radar camouflaging, and cloaking.<br></p>

JDAT: Joint-Dimension-Aware Transformer with Strong Flexibility for EEG Emotion Recognition

<div>Electroencephalography (EEG) emotion recognition, an important task in Human-Computer Interaction (HCI), has made a great breakthrough with the help of deep learning algorithms. Although the application of attention mechanism on conventional models has improved its performance, most previous research rarely focused on multiplex EEG features jointly, lacking a compact model with unified attention modules. This study proposes Joint-Dimension-Aware Transformer (JDAT), a robust model based on squeezed Multi-head Self-Attention (MSA) mechanism for EEG emotion recognition. The adaptive squeezed MSA applied on multidimensional features enables JDAT to focus on diverse EEG information, including space, frequency, and time. Under the joint attention, JDAT is sensitive to the complicated brain activities, such as signal activation, phase-intensity couplings, and resonance. Moreover, its gradually compressed structure contains no recurrent or parallel modules, greatly reducing the memory and complexity, and accelerating the inference process. The proposed JDAT is evaluated on DEAP, DREAMER, and SEED datasets, and experimental results show that it outperforms state-of-the-art methods along with stronger flexibility.</div>

JDAT: Joint-Dimension-Aware Transformer with Strong Flexibility for EEG Emotion Recognition

<div>Electroencephalography (EEG) emotion recognition, an important task in Human-Computer Interaction (HCI), has made a great breakthrough with the help of deep learning algorithms. Although the application of attention mechanism on conventional models has improved its performance, most previous research rarely focused on multiplex EEG features jointly, lacking a compact model with unified attention modules. This study proposes Joint-Dimension-Aware Transformer (JDAT), a robust model based on squeezed Multi-head Self-Attention (MSA) mechanism for EEG emotion recognition. The adaptive squeezed MSA applied on multidimensional features enables JDAT to focus on diverse EEG information, including space, frequency, and time. Under the joint attention, JDAT is sensitive to the complicated brain activities, such as signal activation, phase-intensity couplings, and resonance. Moreover, its gradually compressed structure contains no recurrent or parallel modules, greatly reducing the memory and complexity, and accelerating the inference process. The proposed JDAT is evaluated on DEAP, DREAMER, and SEED datasets, and experimental results show that it outperforms state-of-the-art methods along with stronger flexibility.</div>

Neural language processing across time, space, frequency and age: MEG-MVPA classification of intertrial phase coherence

Language is a key part of human cognition. Whereas many neurocognitive abilities decline with age, for language the picture is much less clear and how exactly language processing changes with aging is still unknown. To investigate this, we employed magnetoencephalography (MEG) and recorded neuromagnetic brain responses to auditory linguistic stimuli in healthy participants of younger and older age using a passive task-free paradigm and a range of different linguistic stimulus contrasts, which enabled us to assess neural language processes at multiple levels (lexical, semantic, morphosyntactic). By using machine learning-based classification algorithms to scrutinise intertrial phase coherence of MEG responses in source space, we found significant differences between younger and older participants across several frequency bands and for all tested processing types, which shows multiple changes in the brain’s neurolinguistic circuits which may be due to both healthy aging in general and compensatory processes in particular.

Design of In-phase and Quadrature Two Paths Space-Time-Modulated Metasurfaces

<p>Space-time-modulated metasurfaces can manipulate electromagnetic waves in space and frequency domain simultaneously. In this paper, an analytical design of space-time- modulated metasurfaces with modulation elements composed of two paths, In-phase (I) and Quadrature (Q), is proposed. The model is derived analytically, <a>the space/frequency domain</a> manipulations are achieved by designing the dimension and time sequence of I and Q paths.<a> In the specular reflection direction, an objective frequency shift of the reflected first order harmonic can be obtained. While, in other directions, the opposite first order harmonic can be easily controlled by changing the dimension of I/Q paths and the objective first order harmonic remains unchanged.</a> Furthermore, with a small dimension of I/Q paths, the first order harmonic can be used for beam scanning by pre-designing the start time of the modulation element. To realize the space-time-modulated metasurface with the required periodically time-varying responses, 2-bit unit-cells loaded with dynamically switchable pin diodes are employed as I/Q modulation. Both analytical and numerical results demonstrate that space and frequency domain manipulations of the reflected fields by the first order harmonics can be simultaneously obtained. The proposed designs have potential applications in wireless communications, radar camouflaging, and cloaking.</p>

Design of In-phase and Quadrature Two Paths Space-Time-Modulated Metasurfaces

<p>Space-time-modulated metasurfaces can manipulate electromagnetic waves in space and frequency domain simultaneously. In this paper, an analytical design of space-time- modulated metasurfaces with modulation elements composed of two paths, In-phase (I) and Quadrature (Q), is proposed. The model is derived analytically, <a>the space/frequency domain</a> manipulations are achieved by designing the dimension and time sequence of I and Q paths.<a> In the specular reflection direction, an objective frequency shift of the reflected first order harmonic can be obtained. While, in other directions, the opposite first order harmonic can be easily controlled by changing the dimension of I/Q paths and the objective first order harmonic remains unchanged.</a> Furthermore, with a small dimension of I/Q paths, the first order harmonic can be used for beam scanning by pre-designing the start time of the modulation element. To realize the space-time-modulated metasurface with the required periodically time-varying responses, 2-bit unit-cells loaded with dynamically switchable pin diodes are employed as I/Q modulation. Both analytical and numerical results demonstrate that space and frequency domain manipulations of the reflected fields by the first order harmonics can be simultaneously obtained. The proposed designs have potential applications in wireless communications, radar camouflaging, and cloaking.</p>

Over-Sampled Codes Design for PCFM Waveforms based WideBand BeamPattern Synthesis

The paper focuses on the design of over-sampled sequence to realize pulse coded frequency modulated(PCFM) waveform based wideband beampattern synthesis. It aims to solve the problem with space-frequency nulling having spectrally contained constant modulus waveforms. Specifically, it considers to minimize the OOB spectral power of the individual code sequences, hence, the individual waveforms during the design process. <div><br></div>

Over-Sampled Codes Design for PCFM Waveforms based WideBand BeamPattern Synthesis

The paper focuses on the design of over-sampled sequence to realize pulse coded frequency modulated(PCFM) waveform based wideband beampattern synthesis. It aims to solve the problem with space-frequency nulling having spectrally contained constant modulus waveforms. Specifically, it considers to minimize the OOB spectral power of the individual code sequences, hence, the individual waveforms during the design process. <div><br></div>