نشریه صنایع الکترونیک
سال نهم شماره 1 (پیاپی 33، بهار 1397)

Underwater acoustic communication channels have particular characteristics such as: high attenuation, the time-varying nature of propagation environment and low speed of the sound, which make it difficult to send information through these channels. Due to the variability of the environment, communication channels in this media are doubly-selective in both time and frequency domain. The time-varying channel can be expressed using expansion basic functions in order to following the temporal variation of the channel. In this paper, orthogonal Laguerre functions expansion is used to express an underwater MIMO-OFDM acoustic communication channel in which the MIMO-OFDM system uses adaptive beamforming at receiver. In order to have matching between the channel and receiver in the proposed system, digital Laguerre filters is used instead of conventional TDL filters in the beamformer. The results show that the proposed system has low computational complexity. Also it has a considerable improvement in the performance of the underwater acoustic communication system.

Communication satellites are generally outside the Earth's atmosphere and the most important characteristic of this environment is the existence of high energy ionizing radiations of MeV energy. The semiconductor materials used in satellites are highly vulnerable to environmental impacts of radiations and electrical, optical and physical characteristics of these materials will be affected and the circuit efficiency will degrade. Because of these problems the available and cost-accessible techniques should be considered. Nowadays, there are many small satellites with the telemetry and telecommunication missions. The high cost of putting satellites in their orbits and problems related to the integration of satellites and their carriers are among the reasons for the development of nano satellites. Reducing the size of components, circuits become more sensitive and circuits with nano dimensions are more vulnerable to space radiations. Quantum cellular automata circuits with the minimum power consumption are a suitable way for the construction of arithmetic circuits in the nanoscale. Providing a method to increase the fault tolerance and simulation of this method for QCA binary wire is discussed in this paper.

There are many techniques to track satellites, that each of them has advantages and disadvantages. The monopulse trackingis the most accurate and most valid one. This paper describes the designing procedure, implementation and testing of remote sensing ground station monopulse tracking receiver. A single aperture monopulse feed in x x band and four feed antenna in s band are being used in ground station. A monoscan converter is used to avoid monopulse amplitude and phase error variation.The tracking receiver uses an ARM processor. Finally system performance is validated by bore sightequipment’s. here are many techniques to track satellites, that each of them has advantages and disadvantages. The monopulse trackingis the most accurate and most valid one. This paper describes the designing procedure, implementation and testing of remote sensing ground station monopulse tracking receiver. A single aperture monopulse feed in x x band and four feed antenna in s band are being used in ground station. A monoscan converter is used to avoid monopulse amplitude and phase error variation.The tracking receiver uses an ARM processor. Finally system performance is validated by bore sightequipment’s.

A single-diode circuit model with a voltage-dependent series resistance is introduced for Organic Solar Cell (OSC). This modified equivalent circuit model benefits from simplicity of the equivalent circuit while it predicts the device behavior accurately. Voltage dependency of series resistance of OSCs is mainly related to the internal processes of charge transport. The received charges at electrodes are influenced by space charge effect and many other physical parameters including exciton lifetime, dissociation rate, and free carrier recombination. The carrier transport process from donor/acceptor interface to electrodes is governed by its mobility. Also, the carrier mobility of organic material depends on the field variation. The voltage-dependent series resistance is not often used in today’s OSC circuit models due to the lack of a reliable field-dependent extraction method. This refined model expands its application in finding optimum bias, behavior analysis and efficiency improvement of OSCs. In this paper, as the first step, voltage-dependent series resistance is modeled. Then a new algorithm is proposed for extracting the voltage-dependent series resistance. Finally, the consistency of the extracted field dependent series resistance with previous literature is discussed. It is shown that the average mean square errors (MSE) of the predicted J-V characteristics by the new approach for five cells under test are improved by a factor of 106 in comparison with those of a constant value Rs approach.

The electrocardiographic signal represents the electrical activity of the heart and one of its applications is diagnosis of cardiac arrhythmias. However there are complications against analysis of a long record. Therefore, certain automatic diagnosis methods are needed. In this paper, an algorithm using a combination of wavelet features and SVM classifier is proposed. For this purpose, the signal noises are removed initially by digital filtering and then by wavelet transform. Then, the R waves are extracted through Pan-Tompkins algorithm. Afterwards, the features of each heartbeat are determined by discrete wavelet transform (DWT) and feature space dimension are reduced by PCA transform. Classification is done through SVM with different kernels. MIT-BIH arrhythmia database and MATLAB Software are used for evaluation of the proposed method in comparison with well-known Feed-Forward Neural Network (FFNN). Five groups including normal heartbeats (N), left bundle branch block (LBBB), right bundle branch block (RBBB), atrial premature beats (APB), and paced beat (PB) are classified through SVM with accuracy of 95.68% in the best case while the obtained classification accuracy for FFNN method is 90.30%. Results show that the proposed algorithm can detect cardiac arrhythmias more effectively.

This article have provided time-based boost controller to convert the voltage of 1.8V to 2.8-3.4 Volts. The timing controller like the digital controller is designed for switching frequency about megahertz, but this controller doesn’t need to use a digital converter and modulation bandwidth with high precision. In this paper, a current control oscillator and delay have used an Integrator and derivative for control circuit respectively. To improve settling time of the output voltage a transistor Mk is used as a feedback with output that the output voltage reaches faster to the final amount. With this technique, the settling time is reduced about 72%. In additional Converter operates over a range switching frequency 485 KHz to 1.42 MHz. In this paper, the effects of non-ideal of the elements, as well as the stability conditions of the control circuit, have been analyzed. Boost converter has been simulated in a standard 0.18µm CMOS process. Also, Circuit efficiency is achieved 87.08% for 3.3V output voltage.

In this paper, we investigate fundamental design principles of surface acoustic wave devices based on 128° YX cut lithium niobate. Surface acoustic wave devices have many applications in gas, temperature, humidity, pressure, torque sensing and also in RF filters. 3D FEM simulations have been done in this article and effect of various parameters like pitch size and the number of electrodes pairs, amplitude and frequency of applied electrical signal and thickness of the substrate on propagating acoustic wave has been investigated. The results show the frequency of the electrical signal is inversely proportional to electrodes pitch size and displacement of atoms are proportional to signal amplitude. Also, the optimum number of pairs of electrodes for electrical signal voltage of 50 V and substrate propagation loss of 0.01 dB per wavelength is equal to 34 pairs. On the other hand, for proper propagation of Rayleigh wave, substrate thickness must not be smaller than half of the pitch size.

In this work, we have investigated the structural and electronic properties of native point defects as well as Ag doping in ZnO applying first principles calculations based on density functional theory. The effect of point defects such as VO and VZn are studied in the increasing and decreasing of p-type carriers. In addition, structural properties, formation energies, defect levels of VO, VZn, Agi, AgO and AgZn are calculated to show the possibility of achieving p-type doping in different environment. VO and VZn are calculated to be donor and acceptor defects, with defect levels of 0.16 eV and 0.20 eV under the conduction band and above the valance band, respectively. At O-rich condition, Ag could replace Zn sites in ZnO crystal structure, which induces an acceptor level 0.14 eV above the top of valance band. As a results, Ag dopant may leads to p-type ZnO in O-rich condition with a proper acceptor level.

Image encryption is a crucial component of data security nowadays. Due to its inherent properties such as sensitivity to initial condition, ergodicity and systematic parametrization chaos systems have been extensively used in image encryption. However, one needs to optimize the chaos for each image being encrypted to provide high quality encryption. Features such as high entropy or low pixel correlation are measures of interest in image encryption. In this paper, we propose a novel technique to optimize a chaos based image encryption algorithm. The image is confused using logistic map as chaos function and diffused by modified Knuth shuffling algorithm. We use the logistic map parameters as encryption key. We then harness TLBO and GSA evolutionary algorithms to speed up the optimization process of these parameters. The optimization method yields parameters that lead to lowest correlation among adjacent pixels or highest entropy. We compare the quality and security of our cryptosystem with some famous image encryption methods in the literature.

In this paper, a voltage controlled LC oscillator is proposed for various frequency band. In the design of the oscillator, the active inductor has been used with a controllable negative resistance method, which improves phase noise and has low power consumption. The circuit is simulated by ADS. The simulation results in the 0.18 μm TSMC CMOS technology shows that the oscillator has a phase noise of -143.682 dBc/Hz in band 1 (1.2 GHz) and at offset 1 MHz. The adjustable frequency range is from 0.72 to 1.25 GHz. Power consumption in the oscillator core is 2.6 to 3.4 mW, which is supplied from 1.8 volt source. Also, the oscillator has a phase noise of -136.174 dBc/Hz in band 2 (1.57 GHz) and at 1 MHz offset. The adjustable frequency range is 1.29 to 1.85 GHz. Power consumption in the oscillator core is also 2.6 to 3.5 mW. The simulation results indicate that the power consumption has been reduced by about 50%, and the phase noise has been improved by 16% to -136.174 dBc/Hz.

In this paper, a radiometer system include Low Noise Amplifier (LNA), mixer and local oscillator, Ku band detector, different frequency band filters, acquisition and processing system are designed for achievement maximum gain and minimum noise. The goal of this design is fabrication a discrete radiometer system for detect very low power in Millimeter Wave (MMW) band, and Another contribution of this design is achieve to the minimum Noise Equivalent Temperature Difference (NETD) with regularize and analyze parameter. For this purpose and due to the available equipment, intended systems are designed and in return for one degree temperature difference in system input, we have 2.51 microvolt changes in output voltage, and leading to fabricate optimum operational PMMW systems. In the following, in order to evaluate the designed system, the output image from the designed system is made up. After the formation of the image, due to the inherent blurring of the PMMW image, the processes of improving and improving the visual quality of the image are executed on the image. In the image processing section, new proposals for super resolution, fusion and their sequence of actions, are presented. The above mentioned methods have been applied to output simulated images and resulted in improved output images.

Clustering is one of the most important field of data mining that aims to divide data into meaningful subsets which are called clusters. This technique involves the process of finding natural groupings in the data set based on the similarities and di similarities which a little or no information about data are available. Over the decades, many clustering algorithms are created in different approaches or a combination of them. In this paper, an algorithm based on density and hierarchical approaches is presented. DBSCAN is one of the algorithms presented in the density-based approach. This algorithm requires two parameters that its determination is a great challenge. In the proposed method, DBSCAN algorithm parameters can be set without user involvement, so that potential clusters are found automatically. The clusters which are so close to each other are merged together until the quality of the final clusters to be enhanced properly. Thus, clusters could be more accurate and high quality. Finally, in order to test the new proposed algorithm, the real dataset in the UCI machine learning repository was used. The results indicate that the new algorithm is more efficient and accurate, and its speed is better than previous methods.