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This letter presents a planar inverted-F antenna (PIFAs) system for Wireless Fidelity 6 (Wi-Fi 6) and Wi-Fi 6E applications with compact size and high isolation. To realize decoupling in a guided way, single-mode structure is proposed based on common mode and differential mode theory. For the demonstration, the mutual coupling between two back-to-back asymmetric PIFAs was reduced by etching two slots on the ground. The measured results show that the two PIFAs, respectively, achieve the impedance bandwidth of 5.14–6.03 GHz and 5.90–7.24 GHz, and the port isolation higher than 17.4 dB across 5.14–7.24 GHz frequency band. [ABSTRACT FROM AUTHOR]

In this paper, we derive an upper bound on load-threshold of coded slotted ALOHA (CSA) for slot erasure channel (SEC) and that for packet erasure channel (PEC), respectively. In SEC, by exploiting the analogy between Gaussian elimination of solving linear equations and the iterative successive interference-cancellation (SIC) decoding procedure of CSA, we derive the upper performance bound for SEC. Subsequently, in PEC, utilizing density evolution to track the average probability of packet-decoded failure within the SIC decoding process, we obtain the upper bound for PEC. Moreover, we propose a numerical search algorithm of these bounds under a given calculating precision. The numerical results indicate that the asymptotic upper limit on load-threshold of CSA over SEC is always less than that over PEC with any given erasure probability and average transmission rate. [ABSTRACT FROM AUTHOR]

A simple, high gain, and dual-polarized patch antenna array for Wi-Fi 6/6E application is proposed in this communication. Different from the conventional feeding method, the patches are driven by coupling dipoles that are printed on the same board. The dipoles are specially designed to be T-shaped to adjust the impedance matching. Broadband covering both 5 and 6 GHz bands of Wi-Fi 6/6E is achieved. The feeding circuit is easily integrated on the board with only parallel dual line utilized. A prototype is fabricated and tested to validate the concept. The measured and simulated results are in good agreement. The measured bandwidth with $S_{11} < -10$ dB for two ports are 5.12–7.50 and 5.15–7.50 GHz with the isolation higher than 30 dB. Moreover, the measured gains are higher than 9.76 and 9.61 dBi for two ports over the operating band with a peak value of 12.05 dBi. The proposed antenna array shows great potential in the application of Wi-Fi mesh. [ABSTRACT FROM AUTHOR]

In this communication, we present a longitudinally slotted substrate integrated slot (SIS) leaky-wave antenna (LWA) for point-to-point communication. To mitigate the dispersion of traditional substrate integrated waveguide (SIW) LWAs, an SIS is proposed by etching a long straight slot along the SIW. The loaded slot mitigates the dispersion of SIW due to the special electric field distribution. Anti-TE10 mode is excited inside the SIS. Then, longitudinal slots are symmetrically loaded on both sides of the long slot. The prototype of SIS LWA is validated by the simulated and experimental results. A frequency bandwidth of 10.3% is realized with the beam squinting within 7° and realized gain of 13.9 ± 0.7 dB at a fixed angle of −7°. The proposed antenna is intended for point-to-point communication. [ABSTRACT FROM AUTHOR]

Major depressive disorder (MDD) is a common and severe psychiatric illness marked by loss of interest and low energy, which result in the highest burden of disability among all mental disorders. Clinical MDD diagnosis still utilizes the phenomenological approach of syndrome-based interview, which leads to a high rate of misdiagnosis. Therefore, it is highly imperative to explore effective biomarkers to enable precise personalized diagnosis. There still exist two main challenges due to complexity of MDD and individual differences. On the one hand, discriminative features need to be investigated to better reflect the characteristics of MDD. On the other hand, the performance from shallow and static learning models is still not satisfactory. To overcome these issues, we propose a novel Multi-Stage Graph Fusion Networks (MSGFN) for major depressive disorder diagnosis. At first, functional connectivity is calculated to better characterize interactions between white matter and gray matter. Second, multi-stage features are obtained by a deep subspace learning model, and a number of graphs are constructed under the self-expression constraints at each stage. Finally, a novel graph convolutional fusion module is proposed with graph convolutional operations to integrate features and graph at each stage. Extensive experiments demonstrate the superior performance of the proposed framework. Our source code is available on: https://github.com/LIST-KONG/MSGFN-master. [ABSTRACT FROM AUTHOR]

To solve the motion planning problems of redundant manipulators disturbed by the periodic noise from device hardwares or their surroundings, a Taylor-type discrete-time circadian rhythms neural network (TD-CRNN) method is proposed, developed, and studied in this article. First, a representative bicriteria optimization scheme combining torque criterion and acceleration criterion is presented for the redundant manipulator. Second, inspired by a continuous-time circadian rhythms model, the corresponding TD-CRNN model is derived based on the Taylor discrete formulation. Third, the 0-stability, convergence, and consistency of the proposed TD-CRNN model are analyzed theoretically and proved strictly. Finally, to confirm the capacity of the resisting periodic noise in the tracking problem of manipulators, two groups of comparative simulations and experiments conducted by the proposed TD-CRNN model are performed before the conclusion is given. [ABSTRACT FROM AUTHOR]

To realize the robust control of multirotor unmanned aerial vehicle (UAV) systems, adaptive multilayer neural dynamics (AMND) controllers are proposed and analyzed. The proposed AMND controllers with the strong anti-perturbation property can drive multirotor UAVs to track time-varying tasks and deal with parameter uncertainty problems. First, the design method of the general multilayer neural dynamics (MLND) controllers is introduced and analyzed. Second, based on the design method, the attitude angles, height, and position controllers of a UAV system are designed. Third, according to the adaptive control theory, a novel AMND controller is designed, which can self-tune the parameters of the UAV. Finally, the proposed AMND method applies to a real-world hexrotor UAV system to illustrate its reliability. Mathematical analysis, computer simulations, and experiments verify the reliability, stability, and effectiveness of the proposed controllers which are used to track time-varying tasks. [ABSTRACT FROM AUTHOR]

Many scientific research and engineering problems can be converted to time-varying quadratic programming (TVQP) problems with constraints. Thus, TVQP problem solving plays an important role in practical applications. Many existing neural networks, such as the gradient neural network (GNN) or zeroing neural network (ZNN), were designed to solve TVQP problems, but the convergent rate is limited. The recent varying-parameter convergent-differential neural network (VP-CDNN) can accelerate the convergent rate, but it can only solve the equality-constrained problem. To remedy this deficiency, a novel barrier varying-parameter dynamic learning network (BVDLN) is proposed and designed, which can solve the equality-, inequality-, and bound-constrained problem. Specifically, the constrained TVQP problem is first converted into a matrix equation. Second, based on the modified Karush–Kuhn–Tucker (KKT) conditions and varying-parameter neural dynamic design method, the BVDLN model is conducted. The superiorities of the proposed BVDLN model can solve multiple-constrained TVQP problems, and the convergent rate can achieve superexponentially convergence. Comparative simulative experiments verify that the proposed BVDLN is more effective and more accurate. Finally, the proposed BVDLN is applied to solve a robot motion planning problems, which verifies the applicability of the proposed model. [ABSTRACT FROM AUTHOR]

In this article, the repetitive motion control of redundant manipulators is investigated. First, a repetitive motion control scheme is presented, and a continuous zeroing neural network (CZNN) model is obtained for solving the scheme. Meanwhile, the development of a discrete zeroing neural network (DZNN) model is desired for convenient computational processing. Based on this, this article proposes a 6-step discretization formula, which has high precision. By using the 6-step discretization formula and the 4-step backward difference formula, a 6-step DZNN (6SDZNN) model is further proposed to handle the repetitive motion control scheme. Theoretical analyses verify the efficacy of the 6SDZNN model. Additionally, some discrete forms of conventional models are developed for comparison. Computer simulations on the basis of the 4-link redundant manipulator are carried out, verifying the theoretical analyses and showing the efficacy of the 6SDZNN model. Finally, physical experiments on the basis of the Kinova Jaco2 manipulator substantiate the practicability of the 6SDZNN model. [ABSTRACT FROM AUTHOR]

As for time-varying tracking control problems, many neural-dynamics-based control methods have been proposed because of their high efficiency. The varying-parameter convergent neural dynamics design method with the characteristic of super-exponential convergence has been applied to design controllers for unmanned aerial vehicles. Although the varying-parameter convergent neural dynamics controller has a fast convergence speed, it still needs long enough time to achieve tracking theoretically. By combining the finite-time activation function with the varying-parameter convergent neural dynamics design method, a finite-time-gain-adjustment design method is proposed and proved theoretically in this paper. This controller can make state variables of the system converge to their time-varying targets in finite time. Compared with some traditional methods, contrastive experiments and application to a multi-rotor unmanned aerial vehicle system illustrate that the proposed controller has finite convergence time, better anti-noise performance, and faster convergence speed, which enable the multi-rotor unmanned aerial vehicles to track time-varying targets more quickly and accurately, so as to achieve more complex and efficient control tasks. [ABSTRACT FROM AUTHOR]

In this article, a two-port microstrip antenna (MSA) with high isolation is presented for simultaneously supporting wireless fidelity 6 (Wi-Fi 6) and wireless fidelity 6E (Wi-Fi 6E) applications. Due to the narrow guard band between Wi-Fi 6 (5.15–5.83 GHz) and Wi-Fi 6E (5.92–7.125 GHz), the mutual coupling near common edge frequencies cannot be sufficiently suppressed by existing filters. To mitigate the mutual coupling over the guard band of a symmetrical two-port MSA, the common-mode (CM)/differential-mode (DM) cancellation theory was utilized. Then, the operating frequencies of two ports were tuned to Wi-Fi 6 and Wi-Fi 6E bands, without deteriorating the original decoupling performance. Finally, two filters were loaded to realize high isolation over the whole working bandwidth. For the demonstration, a prototype was fabricated and measured. The measured results show that the proposed two-port MSA achieves the impedance bandwidth of 5.49–5.9 and 5.89–7.14 GHz and the isolation over 20 dB across the whole band. The results indicate that the proposed antenna is a promising candidate for Wi-Fi 6 and Wi-Fi 6E applications. [ABSTRACT FROM AUTHOR]

In distribution networks with a high penetration of photovoltaic (PV), a coordination between reactive power compensation (RPC) of PV inverter and active power compensation (APC) of battery energy storage system (BESS) is always used in voltage regulation (VR). Since using a periodical VR inevitably increases communication utilization, how to design a new event-triggered one to reduce communication burden while achieving comprehensive voltage governance with the required minimum BESS sizing? Therefore, an event-triggered hybrid VR method is proposed in this paper. Firstly, an event-triggered communication is designed based on the changes in bus voltage and sensitivity, thereby defining all operating instants into transmission and ordinary sampling types. For the voltage violation issue at the transmission instants, a network-wide coordinated proportional RPC-APC is then designed, which keeps constant during one transmission interval. For the additional voltage fluctuation at the ordinary sampling instants in the interval, a local RPC-APC is additionally designed to yield a fast suppression without using any communication. In addition, the required minimum BESS sizing is obtained by calculating the total APC for VR requirement, which gives a reference in configuring BESS. Finally, the case study is conducted to demonstrate the effectiveness of this method. [ABSTRACT FROM AUTHOR]

A broadband and omnidirectional coverage dual-antenna pair with horizontally polarized (HP) radiation for Wi-Fi 6/6E application is presented in this article. The dual-antenna pair is composed of two open cavity antennas (OCA) with the apertures partially sealed. By sealing the aperture partially, the dimension of the proposed half-OCA (HOCA) is reduced dramatically without changing the matching bandwidth and the radiation performance. Compared with other OCAs with the omnidirectional radiation, the proposed dual-antenna pair realizes omnidirectional coverage in azimuth plane by the back-to-back combination of two unidirectional OCAs, which also makes the antenna have multiple-input multiple-output (MIMO) performance. Besides, a broadband covering both 5 and 6 GHz bands of Wi-Fi 6/6E is also achieved. A prototype was fabricated and tested to validate the concept. In well agreement with the simulated results, the measured bandwidth with $S_{11} < -10$ dB for two ports are 5.03–7.35 GHz and 5.09–7.53 GHz, respectively, with the isolation higher than 22.67 dB. Besides, the measured gain > 5 dBi and ECC < 0.05 are achieved over the operating band. The proposed antenna shows great potential in the Wi-Fi 6/6E application. [ABSTRACT FROM AUTHOR]

In this letter, a vertically polarized 360° azimuth scanning phased array based on a wide beamwidth element is proposed. The proposed array consists of two back-to-back linear arrays. The broadside and endfire scanning modes are combined to realize 360° beam scanning in the azimuth plane (H-plane). A 2 × 8 array working at 3 GHz has been fabricated and measured. The array scans from −180° to 180° in the H-plane with the measured peak gain of 10.8 dBi, the measured gain fluctuation less than 2 dB. The total height of the proposed array is 0.32 λ, showing its potentials in aircraft-based application. [ABSTRACT FROM AUTHOR]

This research first proposes the general expression of Zhang et al. discretization (ZeaD) formulas to provide an effective general framework for finding various ZeaD formulas by the idea of high-order derivative simultaneous elimination. Then, to solve the problem of future equality-constrained nonlinear optimization (ECNO) with various noises, a specific ZeaD formula originating from the general ZeaD formula is further studied for the discretization of a noise-perturbed continuous-time advanced zeroing neurodynamic model. Subsequently, the resulting noise-perturbed discrete-time advanced zeroing neurodynamic (NP-DTAZN) algorithm is proposed for the real-time solution to the future ECNO problem with various noises suppressed simultaneously. Moreover, theoretical and numerical results are presented to show the convergence and precision of the proposed NP-DTAZN algorithm in the perturbation of various noises. Finally, comparative numerical and physical experiments based on a Kinova JACO2 robot manipulator are conducted to further substantiate the efficacy, superiority, and practicability of the proposed NP-DTAZN algorithm for solving the future ECNO problem with various noises. [ABSTRACT FROM AUTHOR]

This article demonstrates an electronically scanned reflectarray antenna based on liquid crystal (LC). The LC-based reflectarray element was designed as a periodically loading of parallel H-shaped polygons on two metal layers. To realize a tunable reflection phase and reduce the inhomogeneity effect of LC, an $8~\mu \text{m}$ -thick LC layer was designed as a varactor rather than a substrate. In simulations, the adjustable reflection-phase range of the proposed element was 180° in the frequency band 21–21.5 GHz. The design concept was verified on a reflectarray prototype containing 26 rows of the basic elements. In addition, a 32-channel control circuit was designed and fabricated for biasing. The measured results confirmed a tunable phase range of 150° at 23.8 GHz. The disagreements between the simulated and measured results are discussed, and a test process is proposed. As a proof of concept, the main beam was steered to 0°, −40°, and −60° in one plane. The result confirmed the high beam-steering capability of the proposed reflectarray with measured gains above 18 dB at 23.8 GHz. This work provides useful references for the design and measurement of LC-based reflectarray antennas. [ABSTRACT FROM AUTHOR]

In order to resist periodic interfere in robot hardware or environment, a Runge–Kutta type discrete-time circadian rhythms neural network (RK-DCRNN) model is proposed, and investigated to plan the motion of redundant robot manipulators. To achieve the optimal control, a quadratic programming-based acceleration-level hybrid tri-criteria (ALHT) scheme is first designed, which simultaneously minimize the acceleration norm, torque norm, and joint-angle shift-free indices. Second, according to the neural dynamic design method, a continuous-time circadian rhythms neural network model is exploited, and then based on the Runge–Kutta numerical differential method, a discrete-time circadian rhythms neural network model is obtained. Third, the convergence of the proposed RK-DCRNN model is proved by detailed mathematical derivation. Fourth, comparative simulations and physical experiments verify that the proposed RK-DCRNN model can suppress the accumulation of position error in the motion planning of manipulators. [ABSTRACT FROM AUTHOR]

In this article, a cloud-edge collaboration based control framework is proposed for the voltage regulation and economic operation in incremental distribution networks (IDN). The voltage regulation and economic operation, usually considered in separated aspects, can be integrated in a hierarchical control method by coordinating the active power and reactive power of distributed generators (DGs) and distributed storages (DSs) in an “active” mode. Promising the voltage security of the IDN, the upper level multiobjective optimization is formulated to maximize the consumption of the DGs, moreover, the lower level model predictive control (MPC) aims to regulate the dynamics of the DGs and DSs based on the established state space model. Time delay in the downstream channel is considered due to the open environment of the proposed control framework, which can be eliminated by using the PCM derived from the MPC considering model uncertainty. Finally, simulation results demonstrate the validity and robustness of the proposed method. [ABSTRACT FROM AUTHOR]

This article describes a compact dual-polarized endfire antenna array for fifth-generation (5G) millimeter-Wave (mm-Wave) mobile application. The dual-polarized endfire antenna element is constructed by a compact open-ended cavity with cavity mode for vertical polarization (VP) radiation and open-slot mode for horizontal polarization (HP) radiation. With the integrated design of VP and HP elements, the proposed antenna shows a much more compact size compared to existing schemes. To enhance the bandwidth of low-profile VP radiation, a slot is etched on the cavity to create a new mode for dual-resonance response, realizing a wide bandwidth of 24.5–29.5 GHz for both polarizations. In addition, radiation pattern modification techniques are employed to achieve good endfire beams with a high front-to-back ratio for both polarizations, thus enabling a high peak gain of 10.3 and 11.3 dBi for VP and HP, respectively. A wide beam scanning range of ±50° with realized gain above 7 dBi is realized at 27 GHz for both polarizations. In virtue of compact size, wide bandwidth, high gain, and good spatial coverage, the proposed design strategy is promising for future 5G mm-Wave mobile phones. [ABSTRACT FROM AUTHOR]

Via the Euler forward-difference rule, an Euler-type discrete-time circadian rhythms neural network model (E-DTCRNN) is proposed, developed, and investigated for motion planning of the redundant robot manipulator affected by periodic noises. In this article, an Euler-type discrete-time zeroing neural network model (E-DTZNN) is presented as comparison. The E-DTCRNN model is 0-stable, consistent, and convergent. In addition, through a hybrid torque and velocity optimization scheme synthesized by the proposed E-DTCRNN and the traditional E-DTZNN, a tracking trajectory is designed and applied to the motion planning of the redundant robot manipulator. Finally, groups of simulations and physical experiments verify the efficacy and noise suppression ability of the proposed E-DTCRNN model for motion planning of the manipulator. [ABSTRACT FROM AUTHOR]

A high-gain low-profile leaky-wave antenna (LWA) for vertically-polarized (VP) fixed-beam endfire radiation is proposed in this article. The LWA is composed of two back-to-back half-mode waveguides with grooves etched at the margins of both radiation edges. By etching grooves, the phase velocity of the traveling wave can be tailored to slower than the wave velocity in free space for fitting the Hansen–Woodyard condition. Compared with periodic LWAs, the proposed antenna continuously radiates at two symmetric apertures, contributing to a high endfire gain. A prototype is fabricated and tested to validate the concept. The measured and simulated results are in good agreement. A simulated gain of 14.29 dBi and a measured gain of 13.37 dBi are achieved within an antenna length of $3.05\lambda _{0}$. Moreover, a measured overlapping bandwidth of 2.74–3.17 GHz (14.3%) is realized with $S_{11} < - 10$ dB and gain variation less than 3 dB. To the best of the authors’ knowledge, the proposed VP endfire LWA realizes the highest aperture efficiency and shows great advantages in high gain, low profile, and wide bandwidth. [ABSTRACT FROM AUTHOR]

In this article, a dual-linearly polarized endfire antenna is proposed with high gain and stable radiation patterns. A double-sided slot array antenna (DSSAA) and a corrugated rectangular metal strip (CRMS) are employed to realize vertical and horizontal polarization (HP), respectively. Omnidirectional radiation pattern is obtained by etching transverse slots on both sides of the top and bottom metallic plates of a cavity. Based on the double-sided slot antenna, a DSSAA is proposed and fed by an air-substrate parallel strip line (PSL) for stable endfire radiation patterns. Then, the top plate of the DSSAA is reused as a CRMS for HP and compact size. To verify this concept, an all-metal prototype was fabricated and measured. Both the simulation and experimental results show that the DSSAA and the CRMS could offer the highest endfire gains of 12.5 and 12.9 dB, respectively, within a footprint of $3.47\lambda _{0} \times 0.72\lambda _{0} \times 0.13\lambda _{0}$ ($\lambda _{0}$ is the free-space wavelength at the center frequency). Moreover, an overlapping bandwidth of 7.6% is realized with $\vert S_{11}\vert < -10$ dB, gain variation less than 3 dB. This work may provide useful references for designing dual-polarized endfire antennas with stable radiation patterns, high gain, and compact size. [ABSTRACT FROM AUTHOR]

Redundant robot manipulators are usually applied to various complex scenarios where harmful noise especially periodic calculating noise always exists. In order to avoid the task failure affected by the periodic noise, a circadian rhythms neural network (CRNN) is applied to solve motion planning problems of redundant robot manipulators suffering from the periodic noise. First, in this article, we formulate a tracking problem of redundant manipulators as a convex quadratic programming (QP) problem. Second, the QP problem is converted into a matrix equation. Third, based on the neural dynamic design method, a CRNN model is exploited and developed to solve the matrix equation of the tracking problem. Comparative simulations between the proposed CRNN and the traditional zeroing neural network show that the CRNN has better robustness and performance on solving the end-effector tracking task. Two physical experiments are conducted to further certify the effectiveness, robustness, and practicability of the proposed CRNN. [ABSTRACT FROM AUTHOR]

In this paper, we consider single carrier system with transmit diversity and a new multi-antenna transmission waveform is carefully designed to enable low-complexity anti-interference adaptive equalization. We propose a new space-frequency adaptive equalization method which makes use of the mutual interferences among different antennas from the desired user rather than attempts to completely remove them. We further propose two different ways to significantly reduce the computational complexity based on the idea of subband-wise processing with little sacrifice of equalization performance. Simulation results show that the proposed method exhibits a significant gain over conventional anti-interference schemes. [ABSTRACT FROM AUTHOR]

Future generations of wireless services will always need more efficient strategies for the use of the available frequency spectrum, given the ever-increasing demand for high-speed data services. One of such strategies is given by in-band full-duplex (IBFD) systems, also called simultaneously transmit and receive (STAR) systems, that are considered because spectrum efficiency is not maximized with the current practice of half-duplex communication, where a node either transmits or receives a signal in a single channel. In fact, all currently deployed wireless networks require two separate channels to achieve bi-directionality: Frequency Division Duplex (FDD) and Time Division Duplex (TDD) are the two most commonly-used techniques. This channel separation prevents the self-interference that has been seen as an insurmountable technical problem. Promoted by the popularity of small cell wireless systems, recent works have provided experimental evidence and methodologies for IBFD systems, where a node transmits and receives signals at the same time and on the same frequency band ,. IBFD systems not only increase spectral efficiency, but also minimize overhead and timing constraints. This increases throughput and allows for the possibility of real-time sensing of spectrum occupancy for cognitive devices. Even though IBFD systems have their primary application for bidirectional communication topology (where there are two data flows: terminal A sends data to terminal B, and terminal B sends data to terminal A), a different body of recent works has focused on IBFD in other settings including relay, base-station and multi-hop topologies –. [ABSTRACT FROM AUTHOR]

This article presents a co-linearly polarized (LP) stacked two-port antenna with compact size and broadside radiation patterns for in-band full-duplex (IBFD) application. The proposed IBFD antenna consists of a patch antenna and a substrate integrated waveguide (SIW) cavity-backed slot antenna (CBSA). The patch antenna and the CBSA are used as the transmitter (Tx) and receiver (Rx), respectively. The Rx is placed above the Tx for compact size. Linear polarization and broadside radiation patterns are achieved in this article. A cavity-patch coupling (CPC) path is added for canceling the slot-patch coupling (SPC) by using four probes to connect the top layer of the SIW cavity and the metal ground. Parametric studies show that the two coupling paths can be adjusted independently. Experimental results illustrate that the measured highest isolation over 40 dB is obtained with a compact size of $30\times 30\times {4}$ mm3 ($0.63\lambda _{0} \times 0.63\lambda _{0} \times 0.08\lambda _{0}$ , $\lambda _{0}$ is the free-space wavelength at the center frequency of about 6.29 GHz). The measured −10 dB bandwidths of the Tx and Rx antennas are 430 and 100 MHz, respectively. The proposed stacked IBFD antenna is validated with the merits of identical polarization, same radiation direction, and compact size. [ABSTRACT FROM AUTHOR]

In this article, a compact co-polarized decoupled antenna for full-duplex application working at 1.71 GHz is proposed. The antenna is composed of two back-to-back air-dielectric planar inverted-F antennas (PIFAs) with zero edge-to-edge distance. The whole system is included in a compact volume of $0.45\lambda _{\mathrm {\mathbf {0}}} \times 0.45\lambda _{\mathbf {0}} \times 0.02\lambda _{\mathbf {0}}$. The proposed antenna is designed based on the common mode (CM)/differential mode (DM) cancellation theory and its design guideline is illustrated in detail. Isolation maximum of 42 dB, broadside gain of 6.7 dB, and efficiency of 90% have been achieved in the proposed structure. There is a 1.9 dB gain difference between the broadside gain and the maximum gain. The proposed antenna shows its potentials in the radio frequency front-end incorporate design. [ABSTRACT FROM AUTHOR]

High penetration and fluctuation of renewable energy resources are threatening the voltage security of the integrated hybrid energy system (IHES). This article focuses on providing a fully distributed method to ensure the voltage security and information privacy of the IHES. First, a multiagent system based control scheme is presented, in which the upper level agent is responsible for the voltage security of the whole system, and the local dynamic performance of each distributed energy resource (DER) unit is formulated in the lower level unit agent. Second, a distributed model predictive control (DMPC) based coordinated voltage control method is proposed, by which only partial information exchange is needed in the interaction. Furthermore, the diverse requirements on voltage quality of each microgrid in the IHES are considered in this article and it provides a novel paradigm in this field compared with the traditional methods. To study the stability of the resultant DMPC, the Nash equilibrium is achieved and theoretically proved to ensure the convergence of the proposed method. Finally, the validity of the proposed method is verified by virtue of the simulation and experimental test results. [ABSTRACT FROM AUTHOR]

Neural networks as well as the related neural dynamics have been widely exploited to conduct online computing operations for solving various problems in recent years. This article makes progress along this direction by proposing a saturation-allowed neural dynamics (SAND) model for solving the perturbed time-dependent system of linear equations with noise-tolerant capacity. Specifically, by elaborately constructing a new general framework enhanced by the error-integration information and nonlinear projection functions (PFs), a SAND model is proposed and investigated under various additive noises. In addition, theoretical analyses reveal that the proposed SAND model is of global convergence with zero theoretical error. Moreover, when the value of PF is strictly limited by bounds, i.e., a saturation function, the upper bound of the residual errors of the proposed SAND model is subject to the noises and the bounds of PF. Computer simulation results, as well as robot experiments, verify the superior property of the proposed SAND model for solving the perturbed time-dependent system of linear equations, compared with the state of the prior art. [ABSTRACT FROM AUTHOR]

Joint-drift problems could result in failures in executing task or even damage robots in actual applications and different schemes have been presented to deal with such a knotty problem. However, in these existing schemes, there exists the coupling in coefficients for eliminating the drift in the joint space and the equality constraint for completing the given task in the Cartesian space, thereby, theoretically, leading to a paradox in achieving zero joint drift in the joint space and zero position error in the Cartesian space simultaneously. A novel joint-drift-free (JDF) scheme synthesized by a projected zeroing neural network (PZNN) model for the motion generation and control of redundant robot manipulators perturbed by disturbances is proposed and analyzed in this article. Besides, the PZNN model could adopt saturated or even nonconvex projection functions. The proposed scheme completely decouples the interferences of joint errors in the joint space and position errors in the Cartesian space for the first time. Beyond that, theoretical analysis is conducted in order to validate that the PZNN model is of global convergence to the theoretical kinematics solution to the motion generation of robots, and that the joint-drift problems are thus remedied. Moreover, several simulations and physical experiments on the strength of different robot manipulators are carried out to confirm the superiority, efficiency, and accuracy of the proposed JDF scheme synthesized by the PZNN model for remedying joint-drift problems of redundant robot manipulators in noisy environments. [ABSTRACT FROM AUTHOR]

In this article, a wideband and highly-integrated quad-element multiple-input multiple-output (MIMO) antenna is proposed for the first time, to adapt to the size-limited environment in fifth-generation (5G) smartphones. First, the wideband decoupling between two extremely closely-spaced open-slot antennas with face-to-face and back-to-back configurations are investigated. Then, based on the complementary antenna pairs, wideband integrated quad-element MIMO antennas are implemented by the ingenious combination of these antenna pairs. For validation, an 8 × 8 MIMO system, constituted by two sets of integrated quad-antenna configurations, is simulated, fabricated, and measured. Both the simulated and measured results show that the 8 × 8 MIMO system can provide isolation of better than 10 dB between any two ports and a total antenna efficiency of 52.8%–70.8%/40.5%–75.0% across 3.3–5.0 GHz. Compared with the existing integrated quad-antenna design schemes, the proposed solution can expand the bandwidth from less than 200 to 1700 MHz, covering the entire 5G N77, N78, and N79 bands. In addition to the integrated quad-antenna design, further extension to integrated multiantenna configurations is also discussed by the flexible combination of complementary antenna pairs, which paves the way for future higher-order MIMO system in smartphones. [ABSTRACT FROM AUTHOR]

As an increasing number of unmanned aerial vehicles (UAVs) have been widely applied in many aspects, controllers with higher performance are preferred. In this paper, a new varying-parameter adaptive multi-layer neural dynamic based controller (termed as VP-AMND controller) design method is proposed and applied to controllers of multi-rotor UAVs. First, a varying-parameter convergent neural dynamic (VP-CND) based controller is proposed and its convergence and robustness are theoretically proven. Second, by incorporating the adaptive control method into the VP-CND controller, the VP-AMND controller design method is proposed, of which the global stability, fast convergence speed and strong robustness can be guaranteed. Different from traditional triple zeroing dynamic (TZD) and VP-CND controllers, the proposed VP-AMND controller with self-tuning rates can estimate the unknown disturbances and enhance the stability of the system in the face of uncertainty. Third, computer simulation results verify that the multi-rotor UAVs with VP-AMND controllers can track time-varying trajectories quickly and solve the parameter uncertainty and disturbances problems effectively. [ABSTRACT FROM AUTHOR]

To solve a general time-varying Sylvester equation, a novel integral recurrent neural network (IRNN) is designed and analyzed. This kind of recurrent neural networks is based on an error-integral design equation and does not need training in advance. The IRNN can achieve global convergence performance and strong robustness if odd-monotonically increasing activation functions [i.e., the linear, bipolar-sigmoid, power, or sigmoid-power activation functions (SP-AFs)] are applied. Specifically, if linear or bipolar-sigmoid activation functions are applied, the IRNN possess exponential convergence performance. The IRNN has finite-time convergence property by using power activation function. To obtain faster convergence performance and finite-time convergence property, an SP-AF is designed. Furthermore, by using the discretization method, the discrete IRNN model and its convergence analysis are also presented. Practical application to robot manipulator and computer simulation results with using different activation functions and design parameters have verified the effectiveness, stability, and reliability of the proposed IRNN. [ABSTRACT FROM AUTHOR]

A quadratic programming based neural dynamic (QPND) controller design method is proposed for time-varying trajectory tracking of unmanned aerial vehicles (UAVs). Different from the traditional controller frameworks which only use pitch and roll angles to achieve the horizontal movement of the UAV, all the three attitude angles, i.e., roll, pitch and yaw angles, are applied for horizontal moving in this paper. There are at least three great superiorities of the proposed QPND controller. Firstly, three attitude angles can be coordinated control since the quadratic programming framework incorporates three attitudes. Secondly, the new framework enables the UAV to achieve the additional performance criteria or to perform subtasks. Third, the new controller can track time-varying trajectories due to neural dynamic approach. Specifically, the design process of the controller is divided into position controller design, attitude controller design and quadratic programming formulation. Finally, simulation experiments verify the feasibility and high efficiency of the proposed controller and its superiority compared with some state-of-the-art UAV controllers. [ABSTRACT FROM AUTHOR]

Because of the simple structure and strong flexibility, multirotor unmanned aerial vehicles (UAVs) have attracted considerable attention among scientific researches and engineering fields during the past decades. In this paper, a novel adaptive multilayer neural dynamic (AMND)-based controllers design method is proposed for designing the attitude angle (the roll angle φ, the pitch angle θ, and the yaw angle ψ), height (z), and position (x and y) controllers of a general multirotor UAV model. Global convergence and strong robustness of the proposed AMND-based method and controllers are analyzed and proved theoretically. By incorporating the adaptive control method into the general multilayer neural dynamic-based controllers design method, multirotor UAVs with unknown disturbances can complete time-varying trajectory tracking tasks. AMND-based controllers with the self-tuning rates can estimate the unknown disturbances and solve the model uncertainty problems. Both the theoretical theorems and simulation results illustrate that the proposed design method and its controllers with strong anti-interference property can achieve the time-varying trajectory tracking control stably, reliably, and effectively. Moreover, a practical experiment by using a mini multirotor UAV illustrates the practicability of the AMND-based method. [ABSTRACT FROM AUTHOR]

In this article, an inductance-based decoupling scheme is proposed to reduce the mutual coupling between extremely closely spaced microstrip antennas. The original strong coupling can be effectively suppressed by simply inserting a lumped inductance in between. To offer a systemic design guideline for this decoupling strategy, a mode cancellation method, based on the synthesis of common mode (CM) and differential mode (DM), is proposed. The inserted inductance plays a role of tuning CM and DM impedances to a similar status, which has an equivalent decoupling effect according to the theory of microwave network. Alternatively, the lumped inductance could also be replaced by an inductive connecting strip for a concise topology. To validate the proposed decoupling concept, a prototype is simulated, fabricated, and measured. The experimental results show that the poor isolation of 5 dB is improved to better than 15.4 dB across the entire matched bandwidth of 2.394–2.530 GHz, with an extremely close edge-to-edge distance of 0.016 λ0 and center-to-center distance of 0.44 λ0. Furthermore, the validation of extending to large-scale 1-D and 2-D arrays is also discussed. Featuring simple structure, compressed dimension, strong-coupling suppression, and good radiation performance, the proposed decoupling scheme possesses promising potential for antenna array applications. [ABSTRACT FROM AUTHOR]

Zeroing neural network (ZNN), as an important class of recurrent neural network, has wide applications in various computation and optimization fields. In this article, based on the traditional-type zeroing neural network (TT-ZNN) model, an adaptive fuzzy-type zeroing neural network (AFT-ZNN) model is proposed to settle time-variant quadratic programming problem via integrating an adaptive fuzzy control strategy. The most prominent feature of the AFT-ZNN model is to use an adaptive fuzzy control value to adaptively adjust its convergence rate according to the value of the computational error. Four different activation functions are injected to analyze the convergence rate of the AFT-ZNN model. In addition, different membership functions and different ranges of the fuzzy control value are discussed to study the character of the AFT-ZNN model. Theoretical analysis and numerical comparison results further show that the AFT-ZNN model has better performance than the TT-ZNN model. [ABSTRACT FROM AUTHOR]

To make manipulators fulfill end-effector maintaining tasks, such as writing or drawing tasks in a complex environment, two hybrid multiobjective motion planing schemes, i.e., end-effector posture-maintaining and obstacle avoidance (hybrid PM-OA) schemes are proposed and investigated for wheeled mobile redundant robot manipulators. Specifically, the end-effector posture maintaining, obstacle avoidance, and joint physical limits are considered in a quadratic programming (QP) problem. With these two hybrid PM-OA schemes, the wheeled mobile robot manipulators can maintain its end-effector posture, avoid the obstacle and joint physical limits during executing end-effector tasks. The hybrid PM-OA schemes are finally formulated into a piecewise-linear projection equations (PLPEs) and solved by a recurrent neural network (RNN). Computer simulations are given to substantiate the effectiveness, accuracy, safety, and practicability of the proposed hybrid PM-OA schemes. Comparisons with other schemes and simulations further show that the proposed hybrid PM-OA schemes are more suitable for applications. [ABSTRACT FROM AUTHOR]

Hybrid and intermittent characteristics of the distributed energy resources (DERs) bring great challenges to the security control and economic dispatch (ED) of the microgrids. To bypass these hurdles, this article proposes a multiagent system-based integrated design of security control and ED to guarantee the effective and economical operation of the interconnected microgrids. First, a hierarchical control scheme is constructed by two-level unit agents, in which the switching control and dynamic regulation are fully implemented with the corresponding hybrid behaviors based on the differential hybrid Petri-net (DHPN) model. Based on the DHPN model, a novel dynamic ED integrated with security control is proposed to overcome the issues that cannot be solved in conventional models. Furthermore, to reduce the computational complexity and unified the mathematical model of the DERs, the inverter-based power control strategy is converted to a predictive control model which can be decomposed into several subsystems. In the optimization process, all the subsystems are implemented in a fully distributed, communication free, and rolling optimization manner based on the distributed model predictive control (DMPC). The validity of the proposed design is demonstrated according to the simulation results in case studies. [ABSTRACT FROM AUTHOR]

This communication proposes a wideband decoupling technique to suppress the strong coupling between two extremely closely spaced open-slot antennas and implements a wideband integrated slot antenna pair for fifth-generation (5G) metal-rimmed smartphones. By simply inserting a connecting line between two closely spaced open-slot antennas, a top slot structure can be constituted with odd- and even-mode resonances in the lower and higher bands, respectively, to cancel the original strong mutual coupling. In addition to the decoupling effect, the top slot can also expand the effective radiation aperture of the antenna pair for the bandwidth improvement. The proposed slot antenna pair, with a compact footprint of 28 × 7 ×1.8 mm3, shows good impedance matching, isolated and diversity performance across 3.3–5.0 GHz. Then, an 8 × 8 multiple-input multiple-output (MIMO) system, constituted by four sets of slot antenna pairs, is simulated, fabricated, and measured. Both the simulated and experimental results show that the 8 × 8 MIMO system can offer isolations of better than 10.8 dB and envelope correlation coefficients (ECCs) of less than 0.14 between all eight ports across 3.3–5.0 GHz. Also, a total efficiency of 55.0%–83.1% and 52.5%–83.1% is achieved for Ant1 and Ant2, respectively. Featuring wide bandwidth, compact size, high integration level, and metal rim compatibility, we forecast the proposed solution has great potential for future 5G smartphones. [ABSTRACT FROM AUTHOR]

In this letter, a novel reconfigurable 0°/90° phase shifter is proposed. Compared with the conventional phase shifters, the proposed one uses fewer reconfigurable devices and becomes more compact. Two states of a meander line are used to generate the 90° phase shift, making it suitable for the 2-D beam steering 2-bit array application. A phase shifter prototype on F4B was measured to validate its design theory. Four phase states (i.e., 0°, 90°, 180°, and 270°) are realized through the combination of the phase shifter and the array radiation element. A 2 × 4 array working at 1.5 GHz was fabricated and measured to verify the performance of the proposed phase shifter. When different phase states are switched, the measured peak gain of the array varies from 10.6 to 11.2 dBi. [ABSTRACT FROM AUTHOR]

We demonstrate a distributed feedback (DFB) semiconductor laser based on i-line lithography and surface periodic current injection technologies with a lasing wavelength of 795 nm, which corresponds to the D1 spectrum of Rb and has many applications with respect to alkali vapor lasers and atomic clocks. The maximum output power, side mode suppression ratio (SMSR), and single-longitudinal-mode tunable range of our device are 50.89 mW (at 20 °C), 34.56 dB, and 12.792 nm, respectively. The rate of change in wavelength with temperature of the laser is 0.401 nm/°C, which is equivalent to that of a Fabry-Perot (FP) laser and much better than that of a general DFB device. This device has a cavity the same as an FP laser without any etching gratings, meanwhile the lasing spectrum behaves a single longitudinal mode characteristic as a DFB laser. [ABSTRACT FROM AUTHOR]

In this article, a general decoupling method based on a new perspective of common mode (CM) and differential mode (DM) cancellation is proposed. For two closely spaced antennas, the mutual coupling effect can be analyzed and solved by exciting them simultaneously with in-phase (CM) and out-of-phase (DM) signals. It is theoretically proved that, if CM and DM impedances are the same, the mutual coupling effect between two separated antennas can be totally eliminated. Therefore, we can solve the coupling problem by CM and DM impedance analysis and exploit the unique field properties of characteristic modes to assist in antenna decoupling in a physical intuitive way. To validate the feasibility of this method, two practical design examples, including the decoupling between closely spaced dipole antennas and planar inverted-F antennas, are proposed. Both design examples have demonstrated that the proposed method can provide a systemic design guideline for antenna decoupling and achieve better decoupling performance compared to the conventional decoupling techniques. We forecast the proposed decoupling scheme, with a simplified decoupling procedure, has great potential for the applications of antenna arrays and multi-input multi-output (MIMO) systems. [ABSTRACT FROM AUTHOR]

In this communication, a special Fabry–Perot (FP) cavity antenna with a slender structure is proposed to realize an omnidirectional radiation pattern with horizontal polarization. In our design, a partially reflective strip consisting of periodical slots is placed over the aperture of a long and narrow cavity, thus generating an FP resonance with a uniform electric field distribution along this aperture. As the slot arrays are excited in phase and with a nearly identical amplitude, the proposed slender architecture can provide a horizontally polarized omnidirectional radiation pattern with an enhanced directivity. The proposed antenna is prototyped with a length of $2.95\lambda $ ($\lambda $ is the free space wavelength at the center frequency). In well agreement with the simulation results, the experiment verifies that an omnidirectional pattern is achieved over the operating band (2.41–2.5 GHz), with a realized gain of 7.1–8.52 dBi and a gain variation on the E-plane less than 2.3 dB. In virtue of the low-profile all-metal structure, high efficiency (>86%), and enhanced gain, the proposed slender FP antenna is promising for future wireless communication applications. [ABSTRACT FROM AUTHOR]

Varying-parameter recurrent neural network, being a special kind of neural-dynamic methodology, has revealed powerful abilities to handle various time-varying problems, such as quadratic minimization (QM) and quadratic programming (QP) problems. In this paper, a novel power-type varying-parameter recurrent neural network (PT-VP-RNN) is proposed to solve the perturbed time-varying QM and QP problems. First, based on the generalization of time-varying QM and QP problems, the design process of the PT-VP-RNN is presented in detail. Second, the robustness performance of the proposed PT-VP-RNN is theoretically analyzed and proved. What is more, two numerical examples are simulated to illustrate the robustness convergence performance of PT-VP-RNN even in a large disturbance condition. Finally, two practical application examples (i.e., a robot tracking example and a venture investment example) further verify the effectiveness, accuracy, and widespread applicability of the proposed PT-VP-RNN. [ABSTRACT FROM AUTHOR]

In recent years, many models with high precision for redundant manipulator tracking control have been proposed based on precise kinematics equations. Nevertheless, without precise kinematic equations, developing a model with high precision for tracking control is meaningful. With the help of zeroing neural dynamics (ZND), a continuous ZND model with adaptive Jacobian matrix is obtained. For better computer operation and easier understanding, developing corresponding discrete ZND (DZND) model is also significant. Therefore, two DZND models (termed DZND-I model and DZND-II model) are proposed in this article on the basis of two discretization formulas, respectively. Meanwhile, theoretical analyses are conducted to ensure the efficacy of DZND-I model and DZND-II model. Finally, the efficacy of the two DZND models with adaptive Jacobian matrix is substantiated by experimental results on the basis of the four-link manipulator, UR5 manipulator, and Jaco2 manipulator, respectively. [ABSTRACT FROM AUTHOR]