Cortical Processing of Binaural Cues as Shown by EEG Responses to Random-Chord Stereograms

Spatial hearing facilitates the perceptual organization of complex soundscapes into accurate mental representations of sound sources in the environment. Yet, the role of binaural cues in auditory scene analysis (ASA) has received relatively little attention in recent neuroscientific studies employing novel, spectro-temporally complex stimuli. This may be because a stimulation paradigm that provides binaurally derived grouping cues of sufficient spectro-temporal complexity has not yet been established for neuroscientific ASA experiments. Random-chord stereograms (RCS) are a class of auditory stimuli that exploit spectro-temporal variations in the interaural envelope correlation of noise-like sounds with interaurally coherent fine structure; they evoke salient auditory percepts that emerge only under binaural listening. Here, our aim was to assess the usability of the RCS paradigm for indexing binaural processing in the human brain. To this end, we recorded EEG responses to RCS stimuli from 12 normal-hearing subjects. The stimuli consisted of an initial 3-s noise segment with interaurally uncorrelated envelopes, followed by another 3-s segment, where envelope correlation was modulated periodically according to the RCS paradigm. Modulations were applied either across the entire stimulus bandwidth (wideband stimuli) or in temporally shifting frequency bands (ripple stimulus). Event-related potentials and inter-trial phase coherence analyses of the EEG responses showed that the introduction of the 3- or 5-Hz wideband modulations produced a prominent change-onset complex and ongoing synchronized responses to the RCS modulations. In contrast, the ripple stimulus elicited a change-onset response but no response to ongoing RCS modulation. Frequency-domain analyses revealed increased spectral power at the fundamental frequency and the first harmonic of wideband RCS modulations. RCS stimulation yields robust EEG measures of binaurally driven auditory reorganization and has potential to provide a flexible stimulation paradigm suitable for isolating binaural effects in ASA experiments.

Active Patch Antenna for Wi-Fi 5, 6 and Wi-Fi 6E Applications

The article discusses a planar patch antenna with a metamaterial integrated into the structure, which allows the antenna to function in the upper Wi-Fi 5, 6 frequency range and the Wi-Fi 6E range. For the study, we built graphs of S-parameters, radiation patterns; on the basis of the resulting structure, we formed a MIMO antenna array for which we determined the main characteristics - the envelope correlation coefficient and the multiplexing efficiency

Miniaturized MIMO Antenna with Low Inter-radiator Transmittance and Band Rejection Features

In this article, compact a multiple-input and multiple-output (MIMO) system with flag-shaped radiators and a mountain-shaped ground plane is presented. Isolation is enhanced with the help of a decoupling stub placed between radiators, where two bands are stopped with the help of slits etched into the radiators. The overall size of the proposed antenna is 15 mm ×25 mm ×1.6 mm. The reflection coefficients are less than -10 dB between 3–10.9 GHz, except the bands WiMAX (3.2–3.7 GHz) and WLAN (5–6 GHz); similarly, measured and simulated transmission coefficients are less than -20 dB across the entire band of UWB. The envelope correlation coefficient (ECC) is less than 0.02 and the diversity gain is greater than 9.9 dB. The gain, ECC, radiation pattern, multiplexing efficiency, diversity gain and various other parameters are discussed and evaluated in detail.

Компактная 4x4 MIMO антенна для UWB устройств с копланарным питанием и подавлением Wi-Fi и WLAN

В статье представлена компактная MIMO антенна с питанием копланарным волноводом для UWB устройств. Четырехэлементная антенна с питанием копланарным волноводом выполнена в виде излучателя. Развязка между элементами с одинаковой поляризацией и ортогонально поляризованными элементами составляет более 20 и 25 дБ, соответственно. Дополнительный элемент используется для улучшения развязки на более высокой частоте. Смоделированная и измеренная ширина полосы пропускания предложенной широкополосной UWB (ultra wideband) MIMO антенны, определяемая по входному сопротивлению IBW (impedance bandwidth) по уровню 10 дБ, составляет от 3,6 до 10,3 ГГц. Для предложенной антенны также смоделированы и/или измерены коэффициент отражения, развязка, диаграммы направленности, коэффициент корреляции по огибающей ECC (envelope correlation coefficient), полный активный коэффициент отражения TARC (total active reflection coefficient), коэффициент передачи при приеме на разнесенные антенны DG (diversity gain) и потери по пропускной способности канала CCL (channel capacity loss). Получены значения коэффициентов ECC Ј 0,0022, DG > 9,9 дБ, TARC имеет минимальные отклонения при различных углах, а CCL < 0,4 бит/с/Гц при ширине полосы пропускания, определяемой по входному сопротивлению, по уровню 10 дБ. Данная антенна может быть использована в портативных UWB устройствах.

INTERCONNECTION OF VIVALDI ANTENNAS IN THE MIMO ANTENNA ARRAY

Рассматривается MIMO антенная решетка, сформированная из двух антенн Вивальди, которые должны обеспечить работу в частотном диапазоне, выделенном для сетей пятого поколения - 24,25-24,65 ГГц. Для определения основных параметров антенны применялось моделирование, на основе которого были установлены основные характеристики MIMO антенной решетки: коэффициент корреляции огибающей, коэффициент усиления при разнесенном режиме, эффективность сложения. По результатам было определено, что при расстоянии между антеннами в 6,13 мм достигаются максимально возможные характеристики MIMO антенной решетки, а для стабильного функционирования достаточным является расстояние в 2,45 мм. В статье приводятся размеры исследуемой антенны, графики обратных потерь (S - параметров), диаграммы направленности, коэффициентов корреляции огибающих, коэффициента усиления при разнесенном режиме, эффективности сложения при различных расстояниях между антенными элементами. Обеспечение стабильности работы MIMO антенной решетки является важной задачей, так как все современные системы связи используют эту технологию для реализации многоканальной передачи, а следовательно, для повышения скорости передачи информации. Для определения геометрических характеристик и выполнения моделирования применялось специализированное программное обеспечение The article discusses a MIMO antenna array formed of two Vivaldi antennas, which should provide operation in the frequency range allocated for fifth generation networks - 24.25-24.65 GHz. To determine the main parameters of the antenna, we applied modeling, on the basis of which we determined the main characteristics of the MIMO antenna array: the envelope correlation coefficient, the diversity gain, the multiplexing efficiency. According to the results, we determined that with a distance between antennas of 6.13 mm, the maximum possible characteristics of a MIMO antenna array are achieved, and a distance of 2.45 mm is sufficient for stable operation. The article gives the dimensions of the antenna under study, graphs of return loss (S11 - parameters), radiation patterns, envelope correlation coefficient, diversity gain, multiplexing efficiency at different distances between the antenna elements. Ensuring the stability of the MIMO antenna array is an important task since all modern communication systems use this technology to implement multichannel transmission, and, consequently, to increase the information transfer rate. We used specialized software to determine geometric characteristics and perform modeling

Compact Wideband MIMO Diversity Antenna for Mobile Applications Using Multi-Layered Structure

A closely packed wideband multiple-input multiple-output (MIMO)/diversity antenna (of two ports) with a small size of less than 18.5 mm by 18.5 mm is proposed for mobile communication applications. The antenna can be orthogonally configured for corner installation or by placing it on a back-to-back structure for compact modules. To enhance the isolation and widen the bandwidth, the antenna is structured with multiple layers having differing dielectric constants. The feeding through a via significantly reduces the ground waves. A multi-fidelity surrogate model-assisted design exploration method is employed to obtain the optimized antenna geometric parameters efficiently. The antenna design was investigated using electromagnetic simulation and a physical realization of the optimal design was then created and subjected to a range of tests. The specific parameters investigated included reflection coefficients, mutual coupling between the input ports, radiation patterns, efficiency and parameters specific to MIMO behavior: envelope correlation coefficient and pattern diversity multiplexing coefficient. It was found that the antenna has an impedance bandwidth of approximately 4 GHz, mutual coupling between input ports of better than −18 dB and an envelope correlation coefficient of less than 0.002 across the operating band. This makes it a good candidate design for many mobile MIMO applications.

Demodulation Method for Loran-C at Low SNR Based on Envelope Correlation–Phase Detection

Loran-C is the most important backup and supplement system for the global navigation satellite system (GNSS). However, existing Loran-C demodulation methods are easily affected by noise and skywave interference (SWI). Therefore, this article proposes a demodulation method based on Loran-C pulse envelope correlation–phase detection (EC–PD), in which EC has two implementation schemes, namely moving average-cross correlation and matched correlation, to reduce the effects of noise and SWI. The mathematical models of the EC, calculation of the signal-to-noise ratio (SNR) gain, and selection of the EC schemes are given. The simulation results show that compared with an existing method, the proposed method has clear advantages: (1) The demodulation SNR threshold under Gaussian channel is only −2 dB, a reduction of 12.5 dB; (2) The probability of the demodulated SNR threshold, being less than zero under the SWI environment, can reach 0.78, a 26-fold increase. The test results show that the average data availability of the proposed method is 3.3 times higher than that of the existing method. Thus, our demodulation method has higher engineering application value. This will improve the performance of the modern Loran-C system, making it a more reliable backup for the GNSS.

Analysis of the Envelope Correlation Coefficient of MIMO Antennas Connected with Suspended Lines

Inserting a suspended line is a widely used technique to reduce the envelope correlation coefficients (ECC) of multiple-input multiple-output (MIMO) antennas, but its ECC reduction mechanism has not been carefully investigated so far. In this paper, MIMO antenna pairs connected with different suspended lines were evaluated using a full-wave simulation and measurement results. We calculated the surface current density at the center of the suspended line inserted between the antenna elements and found that the derivative of the surface current density was closely related to the ECC values. Furthermore, parametric studies showed that the suspended line length determines the ECC reduction bandwidth of the MIMO antenna, and the antenna length controls the ECC minimum frequency point. These guidelines provide useful insights into designing a low ECC MIMO antenna employing a suspended line.

Compact MIMO Slots Antenna Design with Different Bands and High Isolation for 5G Smartphone Applications

In this paper, two elements of the multi-input multi-output (MIMO) antenna had been used to study the five (3.1-3.55GHz and 3.7-4.2GHz), (3.4-4.7 GHz), (3.4-3.8GHz) and (3.6-4.2GHz) 5G bands of smartphone applications that is to be introduced to the respective US, Korea, (Europe and China) and Japan markets. With a proposed dimension of 26 × 46 × 0.8 mm3, the medium-structured and small-sized MIMO antenna was not only found to have demonstrated a high degree of isolation and efficiency, it had also exhibited a lower level of envelope correlation coefficient and return loss, which are well-suited for the 5G bands application. From the fabrication of an inexpensive FR4 substrate with a 0.8 mm thickness level, a loss tangent of 0.035 and a dielectric constant of 4.3, the proposed MIMO antennas that had been simulated under the five different band coverage were discovered to have demonstrated a respective isolation level of about 14dB, 12dB, 21.5dB, 19dB and 20dB under a -10dB impendence bandwidth. In the measurement and fabrication outcomes that were derived from the use of the prototype MIMO in the (3.4-3.8) band of the Europe and Chinese markets, the proposed MIMO was thus found to have produced a better performance in terms of efficiency, isolation, and envelope correlation coefficient (ECC).