نشریه صنایع الکترونیک
سال یازدهم شماره 4 (پیاپی 44، زمستان 1399)

Graphene transfer from a metal substrate to the dielectric one is often the first step in graphene device fabrication. in order to achieve the proper performance of these devices surface cleanliness and maximum coverage of transferred graphene are crucial. In this paper wet transfer method and the effects of each stage of the process on transferred graphene quality have been investigated and also the reasons of tear formation and contamination during transfer process have been studied. In this research scanning electron microscopy images has been employed because of graphene surface morphology observation. by applying van der pauw method and measuring electrical resistance which itself depends on coverage percentage and contamination area , the quality of transferred graphene has been evaluated. The results are confirmed by raman spectroscopy in which spectra peaks display crystalline network defects and doping concentration. Finally an optimal process with 95% coverage level and 700 ± 50 ohm electrical resistance has been presented.

In this paper, bulk and thin-film structures of the semi-Heusler Pr-Ni-Bi compound is investigated based on the ab initio density functional theory approach, to study the electronic structure, magnetism, and transport in these systems. Equilibrium crystal structures are obtained for the  and  phases which shows that the  phase is more stable and the application of -2.94GPa hydrostatic pressure causes a phase transition from the  phase to the  phase. Also, in the  phase, the magnetic moment of the system is larger. The calculated density of states and band structure for the  phase shows that the system has a half-metallic behavior and an energy gap equal to 0.351eV appears on the Fermi level, in the spin minority channel. The Seebeck coefficients and power factors are calculated for 200, 300 and 400 Kelvin temperatures and various chemical potentials. Results show that this compound has a moderate thermoelectric performance in the bulk structure which is notably enhanced in the thin film.

In Battery Management Systems (BMS), State of charge of Battery (SOC) estimation is very important to ensure performance and to prevent overcharging and discharging. So far, various methods have been presented to estimate state of charge of Battery. In most of these methods, the statistical characteristics of process noise and measurement are assumed to be known. By choosing the wrong statistical characteristics of process noise and measurement, the performance of the filters is affected and the accuracy of the charging state estimation is reduced and may even lead to divergence. To solve this problem, in this paper, adaptive robust square-root cubature filter is used to estimate state of charge of battery and the least squares recursive algorithm is used to estimate the battery parameters. The proposed method, along with the benefits of reducing computational cost, has advantages such as increased compatibility leading to greater numerical stability and better performance. This is because in the proposed method, all variance matrices remain positive definite. In addition, the proposed method is robust to inaccurate noise information as well as non-Gaussian noise. To evaluate the performance of the proposed method, this method is compared with the classical methods. To evaluate the performance of the proposed method, this method has been compared with the classical method of estimating the state of charge of a battery. The results show the effective performance of the proposed method compared to the other methods.

This paper focuses on designing multiple-controller for nonlinear dynamic systems. An algorithm is proposed that integrates two stages of selecting the nominal local models and designing the local controllers. The proposed algorithm does not need to a priori knowledge about the system and a prior experience to choose the gridding threshold. In order to design the local controllers, the stability and performance criteria are integrated and the local controllers have a simple Proportional-Integral (PI) structure. Although the simple local PI controllers lead to have a simple global multiple-controller, but the bump phenomenon occurs when switching between the active local controller in the closed-loop and another controller in the off-line controllers set waiting to take over the control loop. In order to solve the lift-off and landing issues by switching among different local controllers, a linear quadratic bumpless transfer method is used in the closed-loop. The off-line local controllers were not fed by the error signal to have a bumpless switch. Therefore, the proposed multiple-controller design method provides support to have a gentle switch among different local controllers. To evaluate the proposed method a nonlinear CSTR is simulated. The simulation results demonstrate the success of the proposed method in set-point tracking with a smooth control signal in comparison with the opponents.

The Internet of Things (IoT) is an important part of realizing the smart city and the network coverage of IoT plays a crucial role in this regard. Various parameters such as bandwidth, transmission power, noise and environmental conditions are effective in IoT network coverage. The LoRaWAN is one of the main low-power long-distance protocols for the IoT communication. Implementing the infrastructure, providing IT solutions based on LoRa technology, and securing communication infrastructure are among the capabilities offered in this area. The purpose of this article is to describe the parameters needed to improve performance and increase LoRaWAN coverage. Accordingly, different bandwidth and broadcast factor parameters are tested in the noisy environment and the noise impact on the coverage and bit rate are achieved. Finally, a parameter-based application is implemented and a low-cost, high-coverage, and fixed data rate method is discussed and simulated to make a parking lot intelligent in Tehran.

In this paper, broadband antennas with reconfigurable capability in circular polarization are presented for use in communication links. To achieve the impedance bandwidth and its relatively good circular motion, a German has been proposed that has a falcate patch and two L-shaped probes for feed lines. The proposed antennas can create a left-hand or right-hand circular polarization using an RF switch located in the feeding network. The two structures are analyzed and simulated. The first structure, which is a single antenna and a sample of which was made, has a measured impedance bandwidth 62% (S11 <-10dB) and 3dB axial ratio 49% (AR <3dB). The second structure is an array antenna 1*2 with two falcate patches, four L-shaped probes, and two Wilkinson power dividers. In this array, sequential rotation feeding networks used for enhancement axial ratio bandwidth. According to the simulated results, the impedance bandwidth and AR of the array antenna are 67% (1.31-2.62GHz) and 60% (1.3-2.4GHz), respectively, which is wider than the single antenna. The maximum gain of the array antenna is 10dB in effective bandwidth. These antennas can be used in communication links, electronic support measurement, jamming systems in L and S bands.

This paper develops a permittivity measurement method using a multilayer microstrip structure. It provides modeling and analysis of the proposed structure. The employed method introduces new blocks in the multilayer microstrip model, which can cause more accurate characterization results. These blocks are for modeling the effect of different layers of the transmission line including the material under test and the other layers. Here, a multilayer planar measurement kit is provided for extracting the dielectric parameters of different materials. This measurement kit can measure relative permittivity as well as loss tangent for dielectrics. In addition, this kit can be used for characterization of solid and liquid dielectrics. The measurement setup is typically designed and fabricated for 2 GHz frequency, although it can cover higher frequencies e.g. X bands. The dominant mode and the higher order modes of the resonator can be used for measuring material parameters, in a wide range of frequency. The analytic, simulation and measurement results illustrate good agreement with each other, which confirms the accuracy of the proposed routine.

In this paper a cavity backed slot antenna (CBSA) has been designed and fabricated in ridge gap waveguide technology. To increase the bandwidth of cavity backed slot antenna, two perturbations have been made at to corners of the RGW cavity. The perturbations cause to deviation of resonance frequencies of two degenerate TM100 and TM010 modes . The slot is embedded at the optimum place on the top plate of RGW cavity to create the radiation performance. The cavity is fed by a RGW which has been connected to WR62 waveguide port via staircase transition. parametric study is done to obtain optimum dimensions and position of slot, perturbation and transition using HFSS software. The simulation results show about 10 % bandwidth for S11

In this paper, a new capacitive tilt micro-sensor based on the liquid is designed, analyzed and simulated. This sensor has a cylindrical structure and parallel plates of its capacitors are formed on the two ends of cylinder. Distance between plates is filled equally with the Silicone oil and air. Proposed micro-sensor measures the slope around x-axis. There are three capacitors in the structure of the sensor which have a common plate while other three plates are 60ᵒ sectors of a circle which lie in 60ᵒ apart in a circle. Output of this sensor (out) is defined as a special function of structural capacitors. When cylinder rotates around x-axis, the Silicone oil level remains horizontally while position of the plates with respect to the oil varies. Meanwhile this occurrence changes structural capacitors and consequently (out). In this paper, with a detailed analysis, effect of tilt application to the sensor and its capacitances is drawn using MATLAB. Moreover this structure has been simulated using COMSOL Multiphysics. Obtained simulation and analytical results are in good agreement with each other. Proposed tilt micro-sensor measures the deflection between 0 ° to 360 ° with the sensitivity of 8.011 fF/deg.