Mutual Coupling Characteristics Research Articles

Study of the mutual coupling characteristics of the oxidation thermal effect and microstructural evolution of gas-containing coal

Besides be affected by coal confining pressure, coal seams are also be affected by the surrounding pressure during mining. To understand the heat release characteristics and microstructural evolution of oxidization within coal under different gas pressures is of great significance. For this reason, a combination of theoretical research and test analysis was adopted, which includes differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and mercury intrusion method (MIP). The influences of gas phase transformation and migration on the oxidation and spontaneous combustion processes of gas-containing coal under different gas pressures were explored. The distributions and variations in heat release, gas derivation, pore structure and functional group characteristics during the oxidation of gas-containing coal were analysed. We clarified the cross-coupling attributes of heat, seepage and chemical properties in the oxidation of gas-containing coal. The experimental results show that the methane within coal migrates outward in pores with the increase of temperature, which inhibits the penetration and adsorption of oxygen, thereby inhibiting the coal‑oxygen composite reaction and delaying the heat accumulation within coal. There is a positive correlation between loose and porous characteristics of coal and gas pressure. With the continuous increase of coal temperature, the pore connectivity of high-pressure gas-containing coal is enhanced, which increases the risk of coal spontaneous combustion. The research results are of great significance to the theoretical research on the prevention and prediction of spontaneous combustion of gas-containing coal.

Acoustic Scattering Characteristics and Geometric Parameter Prediction for Underwater Multiple Targets Arranged in a Linear Pattern

The construction of wind farm pilings, submarine pipelines, and underwater submarines involves multiple cylinders. However, there is currently a lack of economic research on predicting the mechanism and characteristics of mutual coupling of acoustic scattering from multiple cylindrical targets. This study investigates the mechanism and prediction method of acoustic scattering for the structural distribution characteristics of underwater multi-cylindrical targets. A model of a multi-cylindrical target’s two-dimensional acoustic field was established using the finite element method. Numerical calculations were then carried out to elucidate the scattering characteristics of the frequency–angle spectrum in far-field omnidirectional scattering. The simulation of echoes in the time domain explains how echoes propagate and interact with each other, and provides formulas for calculating interference and resonance frequencies. The frequency calculation formula extracts key features from the spectrum, providing a basis for predicting the characteristics of multi-cylindrical targets in terms of scale and spatial position. Measurement experiments were conducted on a double-cylindrical target in a water tank, and the theoretical calculations and experimental data were used to estimate the target’s radius and distance. The actual layout confirms the accuracy of the interference and resonance frequency prediction formulas. This study offers a valuable solution for refined feature extraction and spatial estimation of underwater targets.

Design of a Tripod-Shaped Radiator Patch Antenna for Ultra-Wideband Direction Finding.

As UWB technology develops and devices become smaller, miniaturization techniques for an array antenna system are required. In addition, more in-depth research is needed for UWB direction-finding techniques using channel impulse response (CIR) data. This paper proposes an ultra-wideband (UWB) antenna using a single-radiator multiple-port (SRMP) design for the direction-finding systems of smart devices. The proposed SRMP antenna was designed using a single tripod-shaped patch that can replace the array system. The tripod-shaped radiator was optimized using the edge shape design function to improve its broadband and mutual coupling characteristics. For performance verification, the proposed antenna was fabricated, and the reflection coefficient, mutual coupling, and radiation patterns were measured in a fully anechoic chamber. The proposed antenna has an operating frequency band of 6.1 GHz (from 5.8 GHz to 11.9 GHz) for port 1 and a measured mutual coupling of -14.8 dB at 8 GHz. The SRMP antenna has measured maximum gains of 3.5 dBi for port 1 and 2.9 dBi for port 2. To examine the direction-finding performance, the fabricated antenna was connected to a circuit module with a DW3000 chip, which is widely employed in commercial mobile UWB systems. The direction of arrival (DoA) results using the measured CIR data show root-mean-square (RMS) errors of 1.57° and 4.58° at distances of 30 cm and 60 cm.

Research on coupling control of multiple permanent magnet synchronous motors based on NAISMC and SMDO.

The synchronous control system of multi-permanent magnet motor has the characteristics of many parameter variables and mutual coupling. The use of sliding mode control to optimize the parameters in the multi-permanent magnet motor system not only ensures the stability of the system operation, but also improves the control accuracy of the system, which is of great importance in practical applications. Based on this background, the study combines the new adaptive integral sliding mode control (NAISMC) with the improved sliding-mode disturbance observer (SMDO) and uses it for the multi-permanent magnet synchronous motor (MPMSM). In NAISMC, the controller updates and adjusts the parameters of the controller using an adaptive algorithm according to the state of the system and the error signals, which further improves the stability and robustness of the system. SMDO utilizes the principle of the sliding-mode observer to estimate the disturbance of the system, and eliminates the effect of the disturbance on the system by introducing a compensation term. The sliding mode observer calculates the disturbance estimate by comparing the difference between the actual and the estimated outputs. The disturbance estimate is finally used to generate the corresponding compensation signal to eliminate or minimize the effect of the disturbance on the system. NAISMC is combined with SMDO and used in the deviation coupling control of MPMSM. The study established a simulation experiment environment in MATLAB, set the simulation time to 0.4s, and the rated speed of the motor to 1000r/min. The improved sliding mode control scheme is tested, and the results show that the motor output speed, tracking error and electromagnetic torque variation under the improved sliding mode control scheme are smaller than those under the traditional sliding mode control scheme. Under the same simulation conditions, the multi-motor speed synchronization error under the improved sliding mode control scheme is around 0r/min, and its error value is close to 0, so the control effect is higher. In conclusion, the optimization scheme proposed in this study can effectively improve the stability and control accuracy of the multi-motor system.

Design of a Compact Indirect Slot-Fed Wideband Patch Array with an Air SIW Cavity for a High Directivity in Missile Seeker Applications

This research proposes a compact indirect slot-fed wideband patch array antenna for a missile seeker application. The proposed single antenna consists of three dielectric layers for a radiator, an air substrate-integrated waveguide (SIW) cavity, and an indirect feeding network. The rectangular patch is used as a radiator on the first substrate layer, and the air SIW cavity (ASIWC) is employed to obtain high directivity and low mutual coupling characteristics in the second substrate layer. In the third layer, an indirect feeding structure is used to achieve the wideband characteristics in the Ka-band. The single element is extended to a 4 × 1 linear array with fabrication, and the fabricated array characteristics are measured in a full anechoic chamber. The measured operating fractional frequency bandwidth is 9.2%, and the measured array gain is 11.7 dBi at the bore-sight direction (θ0 = 0∘).

Design of a Relocatable Antenna Element Module for a Ku-Band Reconfigurable Array with Low Mutual Coupling

In this study, a modular array antenna with low mutual coupling is proposed for operation in a Ku-band (12–18 GHz) reconfigurable array, which consists of a ground frame board, element blocks, spacing blocks, and connecting rods. The modular element blocks can be freely mounted at any positions on a 46 × 9 grid on the ground frame board. The proposed modular array structure can be used to easily check the performance of different array structures by changing the element positions due to its low mutual coupling characteristics. An expanded view of the proposed array antenna structure is also provided, showcasing how the antenna modules, ground modules, base ground, ground frames, and aluminum rods have been constructed. The value of mutual coupling measured between the adjacent elements is less than -22.9 dB in the E-plane and -18.5 dB in the H-plane. Moreover, the measured radiation efficiency and gain patterns of the active element are shown.

A novel shaped antenna for designing UWB-MIMO system in microwave communications

This paper designed and fabricated a UWB-MIMO antenna based on novel inverted comma-shaped antenna and a CPW-feeder structure. The proposed single monopole antenna is designed by combing an elliptical geometry with merging several circular shapes. The novel structure provides a wide impedance bandwidth from 2.469 to 14.203 GHz. The dimensions of the designed unit cell are 21 mm × 16 mm (0.172λL×0.131λL) and the overall size of dual symmetric antennas is 21 × 34 × 1 mm3. This compact antenna is then used to design 2 × 2 Multiple Input Multiple Output (MIMO) antennas. The proposed low-profile MIMO antenna contains two similar geometries placed with a T-shaped decoupling structure. Measurement results show multiple diversity metrics of the MIMO antenna such as low-value mutual coupling characteristics, better channel capacity losses of less than 0.29 bits/s/Hz, envelope correlation coefficient smaller than 0.004 by far-field radiation, total active reflection coefficient below − 10 dB, diversity gain of less than 9.98 dB and acceptable mean effective gain (MEG ≤ 0.5, MEG ratio = 1). The proposed antenna offers a maximum peak gain value of 6.18 dBi at operating frequency of 13.4 GHz.

Compact Wearable UWB MIMO Antenna with Reduced Mutual Coupling and Notch Characteristics of WLAN Band

Compact Wearable UWB MIMO Antenna with Reduced Mutual Coupling and Notch Characteristics of WLAN Band

Prototype Verification of Self-Interference Suppression for Constant-Amplitude Full-Duplex Phased Array with Finite Phase Shift

In view of the strong self-interference problem when the practical phased array system is simultaneously applied for transmission and reception, under the constraints including limited quantization number, constant envelope amplitude, scanning mode, wideband signal mode, etc., this work studies it and proposes the amplitude-phase joint adjustment method and the phase-only method for beamforming optimization. Through digital simulation design, electromagnetic simulation evaluation and principle test verification, under the actual array system conditions, including 6-bit phase quantization or phase step size of 5.625° and amplitude 0.5 dB quantization step, when the transmitting beam is pointing (0°, 0°), the research has achieved a performance of 11.9~14.4 dB for self-interference suppression; at the same time, the optimized beam shape is maintained well, and the ratio of the main lobe to the side lobes does not change significantly, but the beam gain has a loss of about 2~3 dB. In addition, we studied the interference suppression performance and beam feature retention performance of the optimized beamforming weights in the case of array scanning and broadband signals, and analyzed the influence of the changes in the mutual coupling characteristics between elements caused by scanning and frequency changes on the cancellation performance. This provides a reference for the application research of the simultaneous transmitting and receiving self-interference suppression technology in the actual array system state.

On the Design and Analysis of Compact Super-Wideband Quad Element Chiral MIMO Array for High Data Rate Applications

This paper presents a compact, bouquet-inspired, four-element MIMO array for super wideband (SWB) applications. The proposed unit element monopole antenna has compact geometry, and it is deployed by the fusion of an elliptical and circular-shaped radiator. The convoluted geometry and semi-elliptical ground plane, along with the narrow rectangular slit defected ground structure, provides a wide impedance bandwidth. The designed unit cell has the dimensions of 32 mm × 20 mm × 0.8 mm, operates from 2.9 to 30 GHz (S11 ≤ −10 dB) and provides a bandwidth dimension ratio (BDR) of 2894. The proposed low-profile diversity array without any decoupling structures consists of four orthogonally placed, uncorrelated antennas with an inter element spacing of 0.05 λ0, occupies an area of 57 mm × 57 mm and provides dual polarization. The performance metrics of the diversity array were validated for frequencies over ultra-wideband, using mutual coupling characteristics, envelope correlation coefficient (ECC) by far-field radiation, diversity gain (DG), total active reflection coefficient (TARC), channel capacity loss (CCL) and cumulative distribution function (CDF) analysis. The measured mutual coupling over the operating band was less than −18 dB, the ECC was less than 0.004 and the TARC was less than −15 dB, and a better CCL of ˂0.28 bits/s/Hz was achieved by the fabricated antenna.

Design of a Monopulse System Using a Single Patch Radiator with a Simple Multi-Mode Substrate Integrated Waveguide Feeding Network

This paper proposes the design of a single radiator monopulse antenna with a substrate integrated waveguide (SIW) multi-mode feeding system to reduce the aperture size and simplify the feeding structure. The proposed antenna can effectively reduce the overall system size by using a single patch radiator, compared to conventional systems that require multiple radiators. In addition, to simplify the structure of the pattern comparator we use a SIW multi-mode feeding system with TE10 and TE20 modes. To verify the feasibility, the patch antenna with the SIW multi-mode feed is fabricated, and its antenna characteristics of reflection coefficients, mutual coupling, and radiation patterns are measured in a full anechoic chamber. The accuracy of the direction of arrival (DOA) estimation is further improved by applying the derived calibration factor to the resulting sum and difference ratio. The results demonstrate that the proposed antenna is suitable for compact and lightweight monopulse systems with the single radiator and the simple multi-mode feeding network.

Improving magnetic coupling characteristics of square coupler ICPT system by round corner design

In this paper, a round corner design optimization method for the square coupler is proposed to improve its mutual inductive coupling characteristics by analyzing the relationship between structural characteristics and coupling characteristics of the circular and square couplers. The influence of the optimization parameter on the mutual inductive coupling characteristics and the selection method of the optimal optimization parameter is given. Based on the optimal parameter, the coupling characteristics of circular, square, and optimized square couplers are comprehensively compared under the different gap and horizontal offset distances. Through the simulation and experimental results, the optimized square coupler corresponding to the optimal parameter can combine parts of the advantages on the coupling characteristics of the circular and square couplers, thereby maximizing the mutual inductive coupling characteristics of the square coupler. Besides, the coupling characteristics among the circular, square, and optimized square coils are analyzed. The method to use the optimized square coil as the emitter coil, and use the circular and square coil as the receiver coil, respectively, can have better interoperability.

Modeling an Attack-Mitigation Dynamic Game-Theoretic Scheme for Security Vulnerability Analysis in a Cyber-Physical Power System

The rapid development of advanced information and communication technology has made modern power systems evolve into more complicated cyber-physical power systems (CPPSs) with mutual coupling characteristics between cyber systems and power systems, and at the same time, the CPPSs have to confront some newly emerged risks owing to cyber system unreliability or cyberattacks. In this paper, regarding the cyber and physical attacks in a CPPS, the operation risks and vulnerabilities of transmission lines are discussed in detail by building relevant game-theoretic models. Under two possible cyberattack scenarios, namely time delay of system recovery and distributed denial of service, a three-stage defender-attacker-defender tri-level mathematical programming model is proposed based on dynamic game theory of complete information. In particular, the objective functions and corresponding constraint conditions in each level are analyzed and constructed elaborately. For the solution of this proposed tri-level programming model, a solution method based on an improved particle swarm optimization approach combined with sequential quadratic programming technique is applied during analysis. Finally, the proposed model is validated through two case studies, and some preliminary concluding remarks are summarized.

An Intelligent Deep Learning-Based Direction-of-Arrival Estimation Scheme Using Spherical Antenna Array With Unknown Mutual Coupling

Spherical antenna array (SAA) has become highly attractive where hemispherical scan coverage is required as it can provide uniform directivity in all the scan directions. Various direction-of-arrival (DoA) estimation methods suffer from different problems, such as low accuracies in mismatched conditions, high computational complexity and poor estimation in a harsh environment. Another critical concern is mutual coupling (MC) characteristics between the array elements. These problems affect the quality of the navigation signal in harsh environments. This paper presents a robust DoA estimation and mutual coupling compensation technique based on convolutional neural network (CNN) for Spherical Array. Spherical harmonic decomposition (SHD) is used to facilitate feature extraction in two sets, which contains different features about the elevation and azimuth of the source for DoA estimation. The features serve as input to the learning technique for separate estimation of elevation and azimuth, which consequently reduce computational complexity as against the joint estimation of DoA. Learning methods for DoA estimation with few frames and dense search grids within the spherical array configuration are presented. To solve the MC error, the DoA estimation scheme is also used to obtain accurate spectrum peak in the multipath scenario with unknown MC and sharper spectrum peak via the unique structure of the MC matrix and spatial smoothing algorithms. In all, experimental results, which is the ground truth to test any procedure, show the effectiveness, validity, and potential practical application of the proposed technique.

Research on the Coupled Risk of Key Nodes in Maritime Transport Based on Improved Catastrophe Theory

Defining the degree of risk of maritime transport nodes is an important basis for studying the security status of maritime transport passages. However, some important straits or canals are key nodes in the maritime transport passage, and their system security conditions are affected by the interaction of uncertainty risk factors. This study addresses the issue of the security status of transport nodes from the perspective of the characteristics of influencing factors. With a focus on catastrophes and the mutual coupling characteristics of the factors that influence the security of maritime transport nodes, a model based on principal component analysis (PCA) and catastrophe theory (CT) is constructed, and the coupled risk degree of the key nodes in Chinese maritime transportation is empirically analysed. The results show that the Taiwan Strait has the lowest risk degree and that the Windward Strait has the highest risk degree among the key nodes in Chinese maritime transport. From the perspective of the security status of these key nodes, most nodes are currently in a stable and safe state.

Modelling and control of a back‐to‐back MMC–HVDC system using ADPSS

Back-to-back modular multilevel converter–high-voltage direct current (MMC–HVDC) can realise the asynchronous interconnection of two regional power grids. It can effectively solve the power grid stability problems caused by AC–DC power transfer and avoid the risk of large-scale blackouts. Existing MMC–HVDC modelling methods are usually based on Power Systems Computer Aided Design/Electromagnetic Transients including DC (PSCAD/EMTDC), immensely simplifying the AC system. The simplified model is incapable to reflect the interaction characteristics accurately. To solve this problem, a hybrid simulation model of an actual back-to-back MMC–HVDC system is built using Advanced Digital Power System Simulator (ADPSS). ADPSS is a software developed by China Electric Power Research Institute that can realise multi-time scale hybrid simulation to simulate the mutual coupling characteristics accurately. The model includes the electromagnetic transient simulation model of the DC system, and the control system is designed. Steady-state and transient simulations are carried out to verify its function. In summary, the study provides a better reference for the analysis and designing of the practical system.

Application of SRR to achieve performance improvement and multi‐band characteristics in aperture antennas

This study presents a split-ring resonator (SRR) loaded tri-band open-ended waveguide (OEW) antenna that has higher gain, higher front-to-back radiation ratio and lower mutual coupling characteristics compared to a simple OEW antenna.Tri-band response of the proposed OEW antenna has been achieved by placing three SRRs on the waveguide transverse plane with uniform spacing between them. The reduced mutual coupling makes the antenna suitable for array applications. Lumpled element equivalent circuit of the proposed antenna has also been presented.

An Accelerated Single-Pole Trip Scheme for Zone-2 Faults of Distance Relays

This study presents a new accelerated single-pole trip scheme for distance relays zone-2 single-phase-to-ground faults. A novel nonpilot scheme for detecting the remote-end circuit breaker (CB) operation based on measured signals of unfaulted phases is presented. The proposed method is founded on mutual coupling characteristics of different fault stages between faulted and unfaulted phases. Single-pole tripping of the remote-end CB causes variation of induced voltage on unfaulted phases. The current signals due to this variation are utilized as indicators to issue the accelerated single-pole trip command. The algorithm proficiency in various conditions is tested and impacts of different elements, such as fault resistance, fault location, tower configuration, etc., on its performance are analyzed. Implementation of the new accelerated trip method results in dependability improvement, while it has no adverse effect on the protection security. Extensive simulation results confirm that the proposed method is well capable of protecting internal faults and provides a fast, accurate, and reliable protection technique.

Mutual Coupling Reduction in Microstrip Patch Antenna Arrays Using Parallel Coupled-Line Resonators

This letter presents the implementation of a pair of parallel coupled-line resonators (PCRs) for isolation enhancement in planar microstrip patch array antennas. Each PCR consists of three coupled lines separated by a small coupling distance. The attempted configuration provides band-reject characteristics at the design frequency of 3.5 GHz. Two such PCRs are replicated to provide higher order rejection that enhances the bandstop characteristics. The designed PCR is deployed in a two-element microstrip patch antenna array, and the mutual coupling characteristics are studied. The proposed PCR-based decoupling unit cell provides additional 12–26.2-dB coupling reduction with an enhancement of antenna gain up to 1.25 dB. The prototype antenna is fabricated, and the simulation results are validated using experimental measurements.

Compact transmit receive hybrid electromagnetic isolation in antenna array transceiver system for full duplex applications

This study presents a hybrid electromagnetic isolation mechanism in a transceiver array antenna operating at 5.8 GHz. Maximum isolation between transmitting and receiving array antennas, at a very close spacing (3 mm = 0.058 λ 0 ), and minimum mutual coupling between each array elements is achieved without antenna radiation pattern degradation. The achieved separation is equivalent to 44% size reduction compared with conventional half wavelength spacing criterion. Each of the transmitting and receiving array antennas is a four-element linear microstrip patch array antenna. The employed hybrid isolation technique is composed of defected ground structure, to minimise coupling between array elements, and uniplanar electromagnetic bandgap, to minimise the coupling between the transmitting and receiving antennas. The resulting transceiver array antenna system fulfils -35 dB mutual coupling between array elements, and 60 dB isolation between opponent transmitting and receiving array antennas. The proposed design procedures are discussed and analysed using electromagnetic full wave simulations. Results were verified through experimental measurements for reflection coefficient, mutual coupling and radiation characteristics in which a good agreement with simulated results is granted.