نشریه مهندسی مخابرات جنوب
پیاپی 49 (پاییز 1402)

In this paper, a fourth-order, OTA-free, single-bit, low-consumption discrete-time (DT) delta-sigma (ΔΣ) modulator with CIFF structure is proposed for hearing aid applications. In portable medical devices such as hearing aids that are used permanently, the battery life and energy dissipation are very important. In a typical delta sigma modulator, the power-hungry parts are the OTA. Therefore, the elimination of OTAs is a challenge, and the proposed modulator uses new differential parametric amplifiers, with dynamic thresholde in even stages and inverter-based amplifiers in odd delta sigma stages instead of the OTAs. The dynamic threshold PMOS technique has been used for the first time in differential MPA, and the theoretical analyzes and simulations performed show better performance than the traditional method. Also, a chopper circuit is used on the first fstage to reduce the harmonics and flicker noise. The proposed differential modulator is simulated using standard 180 nm CMOS technology, which achieves 90.5 dB SFDR and 64 dB SNDR with an input bandwidth frequency of 10 kHz and an oversampling ratio of 128. The power supply is 1V and the FOMW were obtained as 3.43 PJ/step.

With the ever-increasing number of Internet of Things devices, their security is becoming a very worrying issue. Weak security measures enable attackers to attack IoT devices. One of these attacks is the distributed denial of service(DDOS) attack. Therefore, the existence of intrusion detection systems in the Internet of Things is of special importance. In this research, the majority voting group approach, which is a subset of machine learning, has been used to detect and predict attacks. The motivation for using this method is to achieve better detection accuracy and a very low false positive rate by combining several machine learning classification algorithms in heterogeneous Internet of Things networks. In this research, the new and improved CICDDOS2019 dataset has been used to evaluate the proposed method. The simulation results show that by applying the majority voting Ensemble method on five attacks from this data set, this method respectively has achieved accuracy of detection 99.9668%, 99.9670%, 100%, 99.9686% and 99.9674% in identifying DNS, NETBIOS, LDAP, UDP and SNMP attacks which better and more stable performance in detecting and predicting attacks have achieved than the basic models .

Network function virtualization technology transforms hardware middleboxes into sets of software-based Virtual Network Function (VNF ) that can host the growing demand for latency-sensitive services at the fog-cloud computing-based networks. Dynamic placement of service functions chain by reusing (VNF) instances can improve resource utilization and save time. To address this problem, we propose a parallelized service function chain placement method by reusing (VNF)  in fog-cloud computing-based networks. Here, the placement problem is configured using deep reinforcement learning approaches with the aim of maximizing long-term cumulative reward. By sharing (VNF) s in parallel, this method can achieve computational acceleration in providing online services. In addition, the proposed method increases the ability to accept future requests by extracting the distribution of the initialized (VNF) s. The simulation results show the superiority of the proposed method, where considering the monetary cost criterion of more than 7%, it performs better than the best existing methods.

In this paper, an adaptive concept of virtual generator based controller for dynamic stability of microgrids consisting of low inertia resources. For this purpose, considering a set of energy storage systems dispatched in the network, a controlled islanding scheme  is provided to dynamically control the microgrid frequency. In this context, based on the concept of center of inertia, the proposed virtual generator scheme is developed through mathematical formulation. Also, from the Inter-area torques evaluated by microgrid control areas in the  center of inertia frame are used as input signals of the developed virtual generator based controller. For the energy storage systems, an equivalent dispatch model is provided and developed through the microgrid dynamic model for improving frequency stability during inter-area oscillations. The proposed virtual generator-based controller is an online and non-model-based scheme which controls several microgrid systems together as an integrated network connected to the upstream network. In order to evaluate the ability of the proposed scheme, realtime simulations are carried out on one  test system consisting of several microgrids. Numerical results demonstrate the effectiveness of the proposed scheme in increasing system inertia constant resulting in a proper dynamic performance with a high damping ratio in facing severe inter-area oscillation.

This article reviews some of the smart antennas used in Eyewear, which can receive frequencies of 700-960 MHz and 2.7-1.7 GHz, as well as Wi-Fi 5G (5.18-5.85 GHz) and Wi-Fi 6e (5.925 -7.125 GHz) to be used in wireless Eyewear glasses. Since the antennas of Eyewear devices that work in 4G, 5G cellular communication standard and Wi-Fi 6 internal wireless communication is a new category, first a general study for antenna bandwidth in different locations is done. Given that, these antennas are designed as mutual elements (coupled) and are mostly placed on FR4 or polycarbonate substrate. Then the MIMO antennas used in these glasses are investigated and gain, efficiency and SAR studies are performed along with different modes. In order to obtain a good adaptation to the use cases, the human head is always considered in the simulations. After that, antenna designs with suitable dielectric cover and frame are suggested.

In today's electronic and digital world, increasing demand for portable systems has led the electronics industry and chip design technology to reduce power consumption methods, and therefore power consumption has become an important criterion in this field. Also, increasing the speed of chips and reducing the propagation delay of circuits has always been an important goal of digital design engineers. Since the Adder element is one of the important elements in many digital systems, so today various Adders with different technologies and design approaches have been proposed, each of which has certain advantages and disadvantages. This paper presents a low-power single-bit full-adder cell design that is based on pass-transistor logic.This circuit is used in the arithmetic logic units of digital signal processors and also in several electronic and digital communication systems that operate within the frequency range of in 1GHz. The proposed cell exploits the pass transistor techniques and XOR-XOR structures to improve the design parameters namely power consumption, propagation delay, power–delay product, and the number of transistors. The proposed circuit is designed using 180nm CMOS technology and the simulation results show that for a supply voltage of 1.8V, the power consumption, delay, and power–delay product have been achieved as 83 W, 89ps, and 7fJ respectively.