نشریه پژوهش های نوین در سامانه های دفاع الکترونیکی
سال دوم شماره 1 (بهار 1402)

In this article, we first defined the basics of metamaterials and electromagnetic absorbers, and then investigated the CR-SRR resonator using metamaterial absorbers. One of the features of this design and simulated structure is much smaller dimensions than the previously designed structure, which saves its construction costs. The metamaterial designed in this article was investigated and simulated numerically and experimentally for radar and Wi-Fi applications. This metamaterial creates three resonance frequencies of GHZ 3.3, GHZ 2.5 and GHZ 1.8. The total dimensions of the simulated unit cell are 8 × 8 × 274.1 mm. 3.3 GHz frequency is used in weather radar. The 20.5GHz frequency is widely used in Wi-Fi for high-bandwidth and high-speed applications. The design of the metamaterial resonator with optimized dimensions increases the bandwidth to more than 32% and improves the dispersion parameter S to 50.60% in the Wi-Fi frequency range. These features have increased the sensitivity and distinctive performance of the metamaterial resonator simulated in this article.

Distributed consensus networks are systems that use calculations and local communication between network nodes in order to reach a common value. In these networks, consensus means reaching an agreement on a specific value of interest that depends on the state of all agents. The consensus algorithm is a protocol that determines the exchange of information between an agent and all its neighbors in the network. In this research, while expressing the concept of consensus in distributed networks, we have tried to express the effects of adverse factors (noise, fading …) on consensus algorithms. Also in this research, considering the vectored signals, average consensus control for discrete-time networks with first-order agents and for fix and switching directional topology has been investigated, and then by simulation, the results, and the convergence rate has been compared with previous works that used scalar signal. Since for the design of the control inputs of the network, the data of each agent(drone) is obtained from the integration of the local state of that agent with the state of the neighboring agents which is affected by random communication noise, the necessary and sufficient conditions to reach the average consensus for the fixed and switching directional topology has been obtained.

The use of new technologies in electronic warfare is inevitable. One of the new weapons in this field are lasers. Laser weapons destroy a target by directing a laser beam and aiming it at the target. Laser means light amplification by the method of inductive emission of radiation. In this paper, it has been tried to use the features of photonic crystal structures and connect it to the body of air fighters to reduce the destructive power of these weapons to its minimum level. Due to the property of the photonic band gap of photonic crystals and the creation of several waveguides in the dielectric rods, the incident light of the laser is deflected and directed into the waveguides, and the laser light has the least collision with the fuselage. The structure is made of hexagonal lattice, which has the lowest amount of light leakage from the waveguide. Another important feature of the proposed structure is that all the dielectric rods have the same radius, which makes the design and implementation easier..

In recent years, rough set theory has become one of the powerful solutions in solving the problem of artificial intelligence and data mining. But the classic version of the Raff set theory is not very suitable for discussing feature reduction in imperfect information systems. An incomplete information system refers to data tables that do not have a value in some attribute directories. Feature selection based on fuzzy rough sets is an effective approach to select the best subset of features. Fuzzy set theory and rough set theory are two distinct but complementary theories that deal with uncertainty in data. The salient features of both theories are within the scope of fuzzy rough tuning theory. This hybrid theory is useful as a potential tool for data mining, especially for feature selection. However, there are relatively few studies on incomplete data with time intervals. The purpose of this paper is to present a fuzzy set approach based on overcoming information systems with incomplete value. Since feature reduction is an NP-hard problem, a fast and effective approximation algorithm is required.. In this paper A new optimization approach known as water cycle algorithm has been used to solve this problem. The presented method was tested on the known UCI dataset. The results of the experiments show that the fuzzy rough and the proposed algorithm gave appropriate results, which is reasonable.

The wide application of wideband RF amplifiers in a variety of telecommunication and electronic circuits has led researchers to optimize their design. An important issue in the design of RF amplifiers is the consideration of transistor values resistors and bias voltages which complicate the design of manual calculations. In this paper the structure of a inductorless wideband amplifier is proposed by the user and the values of the circuit components including transistor width, resistor values and bias voltages are designed and proposed by multi-objective algorithms and power gain (S21) input impedance (S11) noise number (NF) and power consumption are optimized by these algorithms. The results obtained by using detailed element models in the simulation show the considerable ability of these algorithms to find the values of the best-valued circuit components. The algorithm programs were written with Matlab and the circuit was simulated by Hspice with 0.18 µm technology.

This paper presented a reconfigurable dipole antenna for use in wireless communication. The antenna comprises the liquid metal (mercury) injected into the microchannels, by employing soft lithography methods, microfluidic channels are fabricated with Polydimethylsiloxane. The antennas can resist mechanical deformation and return to their original position after the removal of applied stress. The initial length of the antenna is 2cm which can stretch up to 2.4cm. The resonant frequency and radiation patterns in E and H planes can be tuned by increasing the length of the dipole antenna (in COMSOL). To validate the measured antenna, the resonant frequency and radiation patterns are compared with the results of the finite element methods software. Similar results are obtained. This antenna can be used in pressure-based sensors and sensors that can be installed on the body. Compared to other manufactured antennas, this antenna has a better gain at the central frequency of 5 GHz. The innovation of this research is the design and construction of a stretchable antenna with a higher gain than other similar antennas.