<p>This paper presents a novel technique for improving the performance of a modal filter by using an electromagnetic absorber. The study considers a two-conductor modal filter based on a microstrip transmission line. The authors analyzed the effect of the absorber on the MF performance in suppressing conducted and radiated interferences (in the near and far fields). The frequency characteristics of the device were then redefined into the time characteristics in the Advanced Design System. As an excitation, the authors used an ultra-wideband interference pulse of 155 ps (at 0.5 level) and then employed N-norms to estimate and characterize the decomposed pulses. The results show that the use of the absorber can significantly improve the attenuation of the ultra-wideband interference. It was experimentally demonstrated that the value of N1 decreased by a factor of 4.31, N2 – by a factor of 6.52, N5 – by a factor of 1.87. In terms of radiated interference in the near field, the improvement in attenuation of each norm achieved at least 2.81 times. The analysis of the characteristics in the far field showed that the use of the electromagnetic absorber allows reducing the transmission coefficient on average by 2.25 times at a distance of 1 m. To validate the measurement results, the electrodynamic simulation of the modal filter characteristics in the frequency range up to 6 GHz was carried out and showed full agreement with the experimental results.</p>

Since the end of the 19th century, radioelectronic devices (REDs) have actively penetrated into all modern community spheres. Achievements in the fields of radio engineering and electronics, as well as computing, information, telecommunications, and other technologies, have greatly contributed to this. The main elements of REDs are antennas and microwave devices. For example, linear (wire) antennas are the basis of long-distance communication agency networks of various law enforcement agencies and departments. The manufacturing of REDs requires the regular and rapid appearance of more and more advanced types with minimal costs. At the same time, the design complexity of REDs and the tightening of EMC requirements caused by the growth of upper frequencies of useful and interfering signals, the mounting density, as well as the capabilities of generators of intentional electromagnetic impacts, together with the need to take into account inter-element, inter-unit, and inter-system interference, require more and more accurate designs of REDs. However, this becomes impossible without computer modeling, which saves the time and financial resources required for their development, as well as to evaluate the correctness of the proposed technical solutions. During the design process, as a rule, a multivariate analysis or optimization of the product is performed. In this case, methods of computational electrodynamics (one of which is the method of moments) are used. They are based on the replacement of continuous functions with their discrete analogues (construction of a grid), which reduces the problem to the solution of a system of linear algebraic equations (SLAE). The problem’s complexity depends on the complexity of the SLAE solution, which is determined by its order (which in turn is determined by the complexity of the simulated object and its surrounding area) and by the number of the required SLAE solutions for each problem (determined by the upper frequency of the signal, the number, and range of the optimized parameters). This dramatically increases the computational cost, which becomes the main constraint for the optimal design. Therefore, reducing the computational cost for the analysis and optimization of RED elements (in particular, linear antennas) is an important scientific problem. Meanwhile, finding new antenna structures that meet all the desired features (low price, required characteristics, manufacturable design with small dimensions and windage, etc.) is no less important today. One of the promise solutions for these problems is using a wire grid and sparse antennas for modeling and constructing antennas. Since the last century, a lot of research has been performed on them. The aim of this paper is to review their history and the main related aspects such as computational, acceleration, and optimization used methods, the fields of their application, and their evolution to this moment. In addition, this paper provides a possible future implementation of wire-grid and sparse antennas from the authors’ point of view by presenting a new method that is under research to obtain effective wire sparse antennas.

This paper focuses on the combination of the method of moments and the wire-grid approximation as an effective computational technique for modeling symmetrical antennas with low computational cost and quite accurate results. The criteria and conditions for the use of wire-grid surface approximation from various sources are presented together with new recommendations for modeling symmetrical antenna structures using the wire-grid approximation. These recommendations are used to calculate the characteristics of biconical and horn antennas at different frequencies. The results obtained using different grid and mesh settings are compared to those obtained analytically. Moreover, the results are compared to those obtained using the finite difference time domain numerical method, as well as the measured ones. All results are shown to be in a good agreement. The used recommendations for building a symmetrical wire-grid of those symmetrical antenna elements provided the most advantageous parameters of the grid and mesh settings and the wire radius, which are able to give a quite accurate results with low computational cost. Additionally, the known equal area rule was modified for a rectangular grid form. The obtained radiation patterns of a conductive plate using both the original rule and the modified one are compared with the electrodynamic analysis results. It is shown that the use of the modified rule is more accurate when using a rectangle grid form.

With the growth of the radioelectronic complexity and the demand for cutting edge devices, the need to protect them and increase their reliability is also rising. There are many methods to provide this. Modal reservation is one of the most effective, reliable, and least complicated methods used nowadays. Using this method in tracing and mounting of printed circuit boards can guarantee both electromagnetic compatibility (by using modal filtering) and reliability (by using the cold redundancy) of the final electronic device. Modal reservation was proposed in 2015, and since then, massive research has been conducted on its investigations and development including 18 patents for inventions. Most of these studies have been devoted to modal reservation in terms of conducted emissions. However, up to now, a general and comprehensive review of modal reservation and investigations of its application with respect to radiated emissions has not been performed. Therefore, this paper aimed at presenting such a review on the history and recent research on modal reservation, concentrating on the studies related to radiated emissions. In addition, this paper analyzes current studies on the efficiency of using modal reservation under climatic impact.

This paper presents a novel technique for improving modal filter (MF) performance by using an electromagnetic absorber which shows a significant improvement in attenuation of ultra-wideband interference. The authors analyzed the effect of the absorber on the MF performance in suppressing conducted and radiated interferences (in the near and far fields). As an excitation, the authors used an ultra-wideband pulse of 155 ps (at 0.5 level) and then employed N-norms to estimate and characterize the decomposed pulses. It was experimentally demonstrated that the value of N1 decreased by a factor of 4.31, N2by a factor of 6.52, N5by a factor of 1.87. In terms of radiated interference in the near field, the improvement in attenuation of each norm achieved at least 2.81 times. The analysis of the characteristics in the far field showed that the use of the electromagnetic absorber allows reducing the transmission coefficient on average by 2.25 times at a distance of 1 m.INDEX TERMS Electromagnetic compatibility and interference, modal filter, ultra-wideband pulse, electromagnetic absorbers, microwave measurement, TEM-cells.