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The purpose of this study is to obtain the optimal frequency for low-frequency transmission lines while minimizing losses and maintaining the voltage stability of low-frequency systems. This study also emphasizes a reduction in calculations based on mathematical approaches.

Telegrapher’s method has been used to reduce large calculations in low-frequency high-voltage alternating current (LF-HVac) lines. The static compensator (STATCOM) has been used to maintain voltage stability. For optimal frequency selection, a modified Jaya algorithm (MJAYA) for optimal load flow analysis was implemented.

The MJAYA algorithm performed better than other conventional algorithms and determined the optimum frequency selection while minimizing losses. Voltage stability was also achieved with the proposed optimal load flow (OLF), and statistical analysis showed that the proposed OLF reduces the frequency deviation and standard error of the LF-HVac lines.

The optimal frequency for LF-HVac lines has been achieved, Telegrapher’s method has been used in OLF, and STATCOM has been used in LF-HVac transmission lines.

The purpose of the paper is the simulation of nonuniform transmission lines.

The method involves a Magnus expansion and a numerical Laplace transform. The method involves a judicious arrangement of the governing equations so as to enable efficient simulation.

The results confirm an effective and efficient numerical solver for inclusion of nonuniform transmission lines in circuit simulation.

The work combines a Magnus expansion and numerical Laplace transform algorithm in a novel manner and applies the resultant algorithm for the effective and efficient simulation of nonuniform transmission lines.

The design, fabrication and experimental validation of defected microstrip structure (DMS) are proposed to address the problem of near-end crosstalk (NEXT) and far-end crosstalk (FEXT) between the microstrip transmission lines in a printed circuit board.

The proposed DMS evolved with the combination of spur line (L-shaped DMS) and U-shaped DMS topologies. This technique reduces the strength of electromagnetic coupling and suppresses crosstalk by optimizing the capacitive and inductive coupling ratio between the linked microstrip lines. The practical inductance value is much more significant in DMS than in defected ground structures (DGS), but the capacitance value remains the same.

A DMS unit is etched on the aggressor microstrip line instead of the DGS circuit. Because there is no leakage via the ground plane and the circuit size is far smaller than with DGS, the enclosure issue is disregarded. DMS structures have a larger effective inductance and are resistant to electromagnetic interference. A tightly coupled transmission line structure with minimal separation between the coupled microstrip line is designed using DMS. Further research must be conducted to improve the NEXT, FEXT and spacing between the transmission lines.

Simulation and actual measurement results show that the proposed DMS structure can effectively suppress crosstalk by analysing the S-parameters, namely, S_12, S_13 and S_14, with measured values of 1.48 dB, 20.65 dB and 21.099 dB, respectively. The data rate is measured to be 1.34 Gbps as per the eye diagram characterization. The results show that the NEXT and FEXT are reduced by approximately 20 dB in the frequency range of 1–11 GHz for mixed signals. The substantial measured results in the vector network analyser coincide with the computer simulation technology microwave studio suite simulation results.

The purpose of this paper is to design a suitable guard trace to reduce the electromagentic interference between two closely spaced high frequency transmission lines. A novel cross-shaped resonator combined via fence is passed down to alleviate far-end and near-end crosstalk (NEXT) in tightly coupled high-speed transmission lines. The distance between the adjacent transmission lines is increased stepwise as a function of trace width.

A rectangular-shaped resonator via fence is connected by a guard trace has been proposed to overcome the coupling between the traces that is separated by 2 W. Similarly, by creating a cross-shaped resonator via fence connected by guard trace that reduces the spacing further by 1.5 W.

A tightly coupled transmission line structure that needs separation by a designed unit cell structure. Further research needs to be conducted to improve the NEXT, far-end crosstalk (FEXT) and spacing between the transmission lines.

This study portrays a novel method that combines the resonators via fence with a minimum spacing between the tightly coupled transmission lines which reduce the NEXT and FEXT; thereby reducing the size of the routing area. The resultant test structures are characterized at high frequencies using time domain and frequency domain analysis. The following scattering parameters such as insertion loss, NEXT and FEXT of the proposed method are measured as 1.504 dB, >30 dB and >20 dB, respectively.

The purpose of this paper is to gain a better understanding on how metasurfaces behave, in terms of currents in each unit cell. A better knowledge of their behavior could lead to an ad-hoc design for specific applications.

The methodology used is both theoretical and numerical; it is based on circuit theory and on an optimization procedure.

The results show that when the knowledge of the current in each unit cell of a metasurface is needed, the most common approximations currently used are often not accurate. Furthermore, a procedure for the termination of a metasurface, with application-driven goals, is given.

This paper investigates the distribution of the currents in a 2D metamaterial realized with magnetically coupled resonant coils. Different models for the analysis of these structures are illustrated, and the effects of the approximations they introduce on the current values are shown and discussed. Furthermore, proper terminations of the resonators on the boundaries have been investigated by implementing a numerical optimization procedure with the purpose of achieving a uniform distribution of the resonator currents. The results show that the behavior of a metasurface (in terms of currents in each single resonator) depends on different properties; as a consequence, their design is not a trivial task and is dependent on the specific applications they are designed for. A design strategy, with lumped impedance termination, is here proposed.

This study aims to model and investigate low-loss wave-propagation modes across random media. The objective is to achieve better channel properties for applying radio links through random vegetation (e.g. forest) using a beamforming approach. Thus, obtaining the link between the statistical parameters of the media and the channel properties.

A beamforming approach is used to obtain low-loss propagation across random media constructed of long cylinders, i.e. a simplified two dimensional (2D) model of agroforests. The statistical properties of the eigenmode radio wave propagation are studied following a Monte Carlo method. An error quantity is defined to represent the robustness of an eigenmode, and it is shown that it follows a known Lognormal statistical distribution, thereby providing a base for further statistical investigations.

In this study, it is shown that radio wave propagation eigenmodes exist based on a mathematical model. The algorithm presented can find such modes of propagation that are less affected by the statistical variation of the media than the regular beams used in radio wave communication techniques. It is illustrated that a sufficiently chosen eigenmode waveform is not significantly perturbed by the natural variation of the tree trunk diameters.

As a new approach to obtain low-loss propagation in random media at microwave frequencies, the presented mathematical model can calculate scattering-free wave-propagation eigenmodes. A robustness quantity is defined for a specific eigenmode, considering a 2D simplified statistical forest example. This new robustness quantity is useful for performing computationally low-cost optimization problems to find eigenmodes for more complex vegetation models.

For privacy protection, federated learning based on data separation allows machine learning models to be trained on remote devices or in isolated data devices. However, due to the limited resources such as bandwidth and power of local devices, communication in federated learning can be much slower than in local computing. This study aims to improve communication efficiency by reducing the number of communication rounds and the size of information transmitted in each round.

This paper allows each user node to perform multiple local trainings, then upload the local model parameters to a central server. The central server updates the global model parameters by weighted averaging the parameter information. Based on this aggregation, user nodes first cluster the parameter information to be uploaded and then replace each value with the mean value of its cluster. Considering the asymmetry of the federated learning framework, adaptively select the optimal number of clusters required to compress the model information.

While maintaining the loss convergence rate similar to that of federated averaging, the test accuracy did not decrease significantly.

By compressing uplink traffic, the work can improve communication efficiency on dynamic networks with limited resources.

Global sensitivity analysis (SA) by means of Sobol’ indices enhanced with different surrogate modeling techniques is performed in this work. The purpose is to investigate the influence of measurement uncertainties and the environment characteristics themselves on the desired field uniformity in reverberation chambers (RCs). This yields an efficient apparatus for the stirring and chamber design process.

The technique of Sobol’ indices, as a candidate of global SA methods, is suitable for high fluctuations due to its robustness, which can be addressed to the stochastic nature of the RC environment. The aim of using surrogate modeling techniques is to compute the indices efficiently with a moderate number of required simulations. The powerfulness of this approach is introduced in a simple numerical example in which the physical phenomena can be identified more straightforwardly.

This method can provide useful knowledge in the lower frequency range, where the ideal properties of the electromagnetic field in RCs cannot be established, and the importance of the setup parameters can vary from configuration to configuration. In addition, it can serve as a basis for setup adaptation during parallelized electromagnetic compatibility tests, which would result in a more time- and cost-saving option in industrial applications in the future.

Despite the previous attempts, a profound investigation of multiple setup parameters is still a hot topic. The main contribution of this work is the extension of the application area of the method of Sobol’ indices to RCs, which has not been done so far.

The purpose of this paper is to study, a bridged-T topology with inductorless passive network used as a bandpass (BP) negative group delay (NGD) function.

The BP NGD topology under study is composed of an inductorless passive resistive capacitive network. The circuit analysis is elaborated from the equivalent impedance matrix. Then, the analytical model of the C-shunt bridged-T topology voltage transfer function is established. The BP NGD analysis of the considered topology is developed in function of the bridged-T parameters. The NGD properties and characterizations of the proposed topology are analytically expressed. Moreover, the relevance of the BP NGD theory is verified with the design and fabrication of surface mounted device components-based proof-of-concept (PoC).

From measurement results, the BP NGD network with −151 ns at the center frequency of 1 MHz over −6.6 dB attenuation is in very good agreement with the C-shunt bridged-T PoC.

This paper develops a mathematical modeling theory and measurement of a C-shunt bridged-T network circuit.

This paper aims to focus on the inclusion of the frequency behavior of grounding system effect on surge arrester (SA) model parameters’ estimation.

The grounding system impedance and its frequency behavior are the factors that have influence on the SA performance. Up to now, the grounding system impedance effect and the frequency behavior of the soil parameters have not been studied for the estimation of the parameters of the SA frequency-dependent model. In this paper, the grounding system’s influence on the SA dynamic model has been simulated for rod- and counterpoise-shaped electrodes. Particle swarm optimization with a grey wolf optimization algorithm has been implemented as an optimization algorithm to adjust the parameters of the SA dynamic model.

The results show that the frequency behavior of the grounding impedance and soil electrical parameters can impress the optimum parameters of the SA frequency-dependent model and should be considered for more reliable results. Also, the results evidence that the proposed optimization method provides more accurate results compared to other optimization methods.

To the best of the authors’ knowledge, this work is one of the first attempts to investigate the effect of frequency grounding system on SA frequency-dependent model parameters.