Tom 73 (2022): Zeszyt 4 (August 2022)

Recently, graphene-patch antennas have been widely used in communication technology, especially in THz applications due to the extraordinary properties of graphene material. Herein, a graphene-based rectangular microstrip patch antenna is designed on an FR4 substrate material (ɛ_r = 4.3). A single and double-faced superstrate MTM is placed upon the radiating patch for di erent purposes, such as enhancing the overall antenna performance, protecting the patch from environmental jeopardies, and generating a multiband resonance frequency. A single face superstrate triangle SRR unit was used to produce a dual-band frequency at 3.5 and 4.331 THz. The S₁₁ of the dual-band structure is achieved to be −26.78 dB and −46.25 dB with a bandwidth of 400 GHz and 460 GHz, respectively. The double face superstrate MTM unit cell of the triangle SRR printed on the opposite face gives another resonant frequency, so, triple frequency bands of 2.32, 3.35, and 4.38 THz with a wide impedance bandwidth of 230, 520, and 610 GHz, were generated, respectively. The double-face superstrate MTM not only enhances the antenna performance but also generates another resonant frequency that could be used in the next 6G communications. The proposed antenna is designed and optimized using two commercial 3D full-wave software, CST Microwave Studio and Ansoft HFSS, to validate the results.

This paper presents findings for active-clamped flyback (ACF) DC-DC converter 57 W used as an auxiliary power-supply of a wireless inductive-charging system 800 V. Measurements of magnetizing and leakage inductances for three transformers demonstrated how big differences between them could be depending on chosen vendor. Comparison of simulated and measured Bode plots showed that, even when those plots were not matched, one could design a compensator that ensures stable operation. Evaluation of cross-regulation when output with low power (9.62 % of total) was regulated showed that such approach was feasible too. The switching frequency vs output-power and drain-source voltage of switch vs output-power graphs are presented for the first time. Comparison of bandwidth, phase-margin and gain-margin vsinput-power, between the ACF and conventional flyback converter were discussed too. Those quantities were changeable with load and input-voltage as expected. The conventional flyback converter in DCM has higher bandwidth than the ACF which resulted in lower phase- and gain-margins. That showed that it cannot have the same compensator as an ACF.

This paper addresses the self-nulling phenomenon also known as the self-cancellation in adaptive beamformers. Optimum beamforming requires knowledge of the desired signal characteristics, either its statistics, its direction-of-arrival, or its response vector. Inaccuracies in the required information lead the beamformer to attenuate the desired signal as if it were interference. Self-nulling is caused by the desired signal having large power (high SNR) relative to the interference signal in case of the minimum variance distortion less response beamformer, and low power desired signal in the case of the constant modulus algorithm (CMA) beamformer, which leads the beamformer to suppress the desired signal and lock onto the interference signal. The least-square constant modulus algorithm is a prominent blind adaptive beamforming algorithm. We propose two CMA-based algorithms which exploit the constant modularity as well as power or DOA of the desired signal to avoid self-nulling in beamforming. Simulations results verify the effectiveness of the proposed algorithms.

Wireless Power Transfer (WPT) technology has recently gained popularity in applications and research topics. It enables the transfer of electrical energy from a source to a load without connecting wires physically. The WPT system is commonly studied classically using integer order capacitors and inductors. Nonetheless, such integer order based systems have drawbacks, such as low output power, poor transmission efficiency and sensitivity to parameter variations. This paper proposes a fractional order resonant WPT circuit whereby both the transmitting and receiving ends are composed of a fractional capacitor and inductor to overcome such problems. In this paper, the overall performance is studied based on its output power and efficiency considering a series-parallel topology. The effect of fractional order in fractal elements will be analyzed to observe the optimal combination of components to achieve the maximum output power with higher efficiency. Through a comparative analysis of the results, several combinations of circuit parameters can provide a theoretical understanding for implementing an experimental system.

Routing protocol for low power and lossy networks (RPL) has been proposed for power, memory, and processing constrained devices. Owing to their constrained, RPL-based networks are exposed to a wide range of security attacks that mainly include control message tampering. In this paper we propose and study a modified version number attack, based on flooding the network by falsified incremented version numbers. The obtained results show that the modified attack led to an immense increase in the overhead, 1426%, compared with the attack-free case, and an increase of 182 % in the total energy consumption. When it comes to PDR a degradation to 4.7% has been recorded, affecting the reliability of the network. On the other hand, the latency also showed an increase from 0.24 s in the attack-free case to 0.89 s, which is mainly due to the high congestion created by the attack.

Quantum-dot Cellular Automata (QCA) is a rival to complementary-metal-oxide-semiconductor (CMOS)-based technology and one of the most cutting-edge nano-scale technologies. The multiplexer is a fundamental component in the fields of nano communication and nano computation. The investigative item of this article is the QCA multiplexer, and a handful of the best multiplexers were chosen as samples for the current experiment. The QCA layouts were designed in the QCADesigner-2.0.3 simulation engine environment, and the best one was reported after successfully experimenting on a total of eight samples. The co-ordinate-based energy was estimated using QCADesigner-E (QDE), and the non-adiabatic energy waste was investigated using QCAPro. According to the coordinates-based technique, the overall energy waste of the best energy-saving QCA multiplexer is 5.90 meV, with an average energy loss per cycle of 0.537 meV. Another approach, QCAPro-based, was used to estimate the energy loss at three different levels of tunneling at a constant temperature, yielding an overall energy loss of approximately 12 to 15 meV for the energy-efficient multiplexers..

Channel equalization is the efficient method for recovering distorted signal and correspondingly reducing bit error rate (BER). Different type of equalizations, like feed forward equalization (FFE) and decision feedback equalization (DFE) are canceling channel effect and recovering channel response. Separate optimization of tap coefficients for FFE and DFE does not give optimal result. In this case FFE and DFE tap coefficients are found separately and they are not collaborating. Therefore, the final equalization result is not global optimal. In the present paper new analytical method for finding best tap coefficients for FFE and DFE joint equalization is introduced. The proposed method can be used for both NRZ and PAM4 signals. The idea of the methodology is to combine FFE and DFE tap coefficients into one optimization problem and allow them to collaborate and lead to the global optimal solution. The proposed joint optimization method is fast, easy to implement and efficient. The method has been tested for several measured channels and the analysis of the results are discussed.

Spam annoys users and poses a security threat. This article proposes a spam filter based on geographical location of the sender determined by IP geolocation. This filter was implemented as a plugin to the SpamAssassin anti-spam software. The plugin allows to define a penalty score for specific countries sending spam. The proposed filter was tested on a dataset of 1500 e-mails consisting of 1200 spam and 300 legitimate e-mails. The Matthews correlation coefficient of the filter has a value of 0.222. This indicates that the proposed spam filter contributes to the correct spam filtering.

This letter proposes a concept to discriminate an electrical fault from a cyber attack in the modern power system. A cyber attack factor is introduced which may mislead the bus voltage stability virtually at load buses. The proposed cyber attack models are validated by executing multiple cyber attacks at a time on Western system coordinating council (WSCC) 9 bus test power system by using Siemens PSS/E and MATLAB softwares. Further, the impact of electrical fault and cyber attack on the WSCC 9 bus test power systems voltage stability has been analysed to develop a discrimination algorithm in reference to chosen load index. Despite its simplicity, the proposed discrimination algorithm is robust, accurate and quite suitable to develop intelligent measures for mal-operations against cyber attacks in the smart electric grid.

This paper concentrates on an algorithm with model predictive control for current and distributed MPPT for cascaded H-bridge multilevel photovoltaic (PV) inverter applications. In conventional method, in each sampling period, a discrete-time model is employed to predict the current future values for all vectors of voltage. The voltage vector will be approved if it minimizes the cost function. Because multilevel inverter has so many available voltage vectors, there is a large quantity of calculations, hence it makes difficult in implementing the normal control method. A varied control strategy that extensively decreases the calculations volume and eliminating common-mode voltage is proposed. To raise the PV modules performance and enlarge the systems power, a distributed maximum power point tracking (MPPT) control scheme for each phase of multilevel inverter is offered, that allows its DC-link voltage to be regulated separately. The recommended approach is double-checked by using a model simulated in MATLAB-Simulink software.