مجله مهندسی برق و الکترونیک ایران
سال هجدهم شماره 4 (زمستان 1400)

Operational amplifiers are one of the most widely used basic blocks in analog and mixed systems. In this paper, a four-stage transduction operational amplifier with low die occupancy is proposed. In this structure, an all-differential block is used as the fourth stage and the compensation network. The proposed amplifier compensation is done with a single and small MOSCAP. This has improved the GBW and FOM because of reducing the number and amount of the compensating capacitor while reducing the die occupancy.  The simplicity and robustness of the proposed design make it possible to implement in a chip with dimensions of 210x250 μm. The proposed four-stage amplifier is simulated using standard TSMC 0.18µ CMOS technology. The advantage of the design is the presentation of a structure that can be implemented and is robust to changes in circuit parameters in implementation. According to simulation, DC gain, power consumption, slew rate, GBW, and PM are obtained 120dB, 545µW, 2.12 V/µS, 16.4 MHz, and 88⁰, respectively.

In this paper, the analysis, simulation and fabrication of high-efficiency broadband parallel-circuit Class-E power amplifier (PA) for satellite communication systems has been presented. The PA’s broadband characteristics are achieved through analysis of the load network using double reactance compensation technique, second and third harmonic control circuits. The proposed circuit has been simulated by ADS 2014 and simulated results by ideal and real elements have been evaluated. A high power LDMOS transistor AFT09MS007N was used as an active device. Then for validation, a prototype of the proposed PA has been fabricated and tested. The measured results show that the drain efficiency (DE) and power added efficiency (PAE) are more than 75% and 69% over 400-460 MHz frequency range, respectively. In addition, the maximum values DE of 83% and PAE of 75% for input power of 27 dBm and drain voltage of 12 V has been obtained. Finally, the simulated and measured results are in a good agreement.

An interleaved buck converter is presented in this paper that its operation is improved by providing soft switching condition. The proposed converter is included two similar buck converters and just one auxiliary circuit. The auxiliary circuit provides the soft switching condition for both main switches. In addition, soft switching condition is provided for auxiliary switch and diodes. The freewheeling diodes in output are replaced with synchronous switches to reduce the conduction losses in this converter. Simulation results of a 220 W – 100 kHz buck converter are presented to justify the validity of the theoretical analysis after analyzing the proposed converter and its operating modes. Bode diagram is also provided to compare transient responses of the proposed and regular buck converter. Moreover, efficiency curve of the proposed converter are presented for comparison with the same converter in hard switching condition that illustrate improvement of the converter efficiency.

Today, with the ever-increasing use of mobile devices, power consumption besides cost and performance has become an important parameter in the design of digital systems. Approximate computational blocks, with acceptable accuracy, have a positive impact on all three criteria of cost, power, and performance; approximate or inaccurate calculations has been accepted more than ever as a new approach to the design of digital systems. In this paper, an approximate adder is designed and the error rate is evaluated. Then, by using this adder, an approximate multiplier is also proposed. This multiplier is used in smoothing and sharpening application in the image processing applications. Using these computing blocks has led to saving 63% of dynamic power consumption, 70% static power saving, 25% decrease in design area and 33% improvement in latency. Also, the amount of error of system due to the use of approximate calculations is on average 33%, which does not have a negative effect on the function of the application in smoothing and sharpening.

In this paper, a low voltage OTA has been designed and simulated using independent gate FinFET transistors for low power applications. Pseudo differential input stage and self-bias techniques have been used for rail-to-rail operation of the input stage of the amplifier. Furthermore, by using double gate FinFET instead of CMOS transistors, frequency response and power dissipation have been improved. For the independent gate FinFET, one gate has been used for biasing and the other has been used for input signal. DFC method has been used for frequency compensation employing small capacitor. 20nm PTM model has been used for amplifier simulations using HSPICE. Simulation results show that amplifier gain is 39.27dB with 45.05 degrees PM and unity gain frequency is 8.26 MHz with a 3pF loading capacitor. The total power dissipation is 37.75 µW, using 0.5V supply voltage and 0.267V output stage DC voltage.

In this paper, we proposed a two-channel demultiplexer based on two-dimensional (2D) photonic crystal (PhC) circular nano-resonator. the structure consists of two photonic crystal filters. At first, we analyze the photonic crystal filter. In this analysis, the structure is optimized by scanning the radius of nano-resonators central rods and radius of scattering rods. The results reveal that the average quality factor, average transmission coefficient, average crosstalk, and average channel width are respectively obtained as 3506.9, 94.3%, -25.35 dB, and 0.45 nm. The advantages of this design is simple structure and small size, which can be used in WDM systems.

In this paper, a broadband optical modulator containing two bilayers of graphene and h-BN is designed and analyzed. Graphene monolayers with sub-wavelength thickness and tunable absorption rates have become a key element in optical device design. The h-BN dielectric layer has been used to maintain the properties of graphene monolayers in structures containing two or more graphene layers. In this paper, the proposed optical modulator structure consists of two bilayers of graphene and h-BN layers which apply voltage to the graphene layers which modifies the chemical potential of graphene and by controlling the amount of graphene absorption, modulation of the light output is provided. The proposed structure for the modulator is studied by calculating the modulatorchr('39')s performance characteristics through the FDTD method. The proposed modulator has a proper performance in the wavelength range of 1800-1300 nm and it exhibits the modulation depth 0.12 dB/µm and the extinction ratio 12 dB with the insertion loss 0.16 dB/µm at wavelength of 1550 nm.

In this paper, GaN/AlGaN heterojunction high electron mobility transistors (HEMTs) with intrinsic spacer layer and back gate have been proposed. The effect of the back gate and intrinsic GaN spacer layer on transistors’ DC and AC behavior have been studied. Performance parameters such as drain current, transconductance, cutoff frequency, maximum oscillation frequency, subthreshold swing and drain induced barrier lowering (DIBL) have been calculated for all designs. The mentioned parameters have been compared between the proposed single-gate and double-gate structures which show the improved performance of the transistor with added back gate. In addition, the effect of adding the intrinsic space layer to the proposed doube gate HEMT has been investigated. The calculation of the frequency response shows that the cut-off frequency of the proposed HEMT is 272 GHz which has considerably increased compared to the 132 GHz for the double gate HEMT without spacer layer. The results reveal that adding the back gate and the intrinsic spacer layer to the structures, both have resulted in improved DC and AC characteristics of the HEMT.

In this paper, a double gate junctionless tunnel field effect transistor (JLTFET) with multi material gate (MMG) structure is presented, and the performance of the transistor has been investigated based on the energy band diagram. All simulations have been carried out using the two dimensional Silvaco Atlas simulator. The effect of the conduction band minima on the abruptness of transition between the ON and OFF states has been hown. Selection of the appropriate value of the gate work function of the proposed structure can give low OFF current, low subthreshold swing, high ON current and improved ION/IOFF. Also, in this paper, the electrical characteristics of MM DG Tunnel FET have been compared with single and dual material gates structures. The proposed structure presented low threshold voltage, high ON current and high ION/IOFF in comparison with the other structures. Finally, high transconductance and high cut-off frequency were observed in multi material double gate device in comparison to other structures.

In this paper, a digital calibration technique is presented to correct the effect of circuit non-idealities in pipelined analog-to-digital converters (ADCs). This method consists of two parts. Firstly, the circuit errors are roughly estimated with a background calibration scheme. Then, in the second part, the estimated errors are finely adjusted to follow the process and temperarure variations. In the proposed calibration method, a combination of equalization, comparator threshold voltage adjustment and histogram of decision poinits techniques along with the geometrical transfer characteristics of the backend ADC on the errors are utilized. The proposed calibration scheme is utilized in a 12-bit, 100 MS/s pipelined ADC with 12 1.5 bit/stage with capacitor non-flip-around (CNFA) struture and 2-bit backend flash ADC. The circuit level simulated values of signal-to-noise and distortion ratio (SNDR) and spurious free dynamic range (SFDR) are improved about 31 dB and 41 dB, respectively, compared to the non-calibrated ADC.

Design of the delay element, a key building block of the time to digital converters (TDCs), is a challenging part of the ADPLL design. Beside the analyzing different types of variable delay elements, a novel delay element design is proposed to minimize the propagation delay and increases resolution of the TDCs proportionally. In addition, sensitivity of the proposed design to mismatch and process variations is less than the conventional designs. To validate the effectiveness of the idea, a new 8bit TDC is designed which uses a tunable gain time amplifier (TA) and achieves the sub picosecond resolution. By utilizing a calibration circuit, the TA gain variation reduces to less than 1%. Simulation results in 0.18µm CMOS technology show 35% reduction in TDC resolution and some 20% improvement in power consumption.

In recent years, the widespread growth of GHz electronic systems and communication devices and also the widespread use of equipment such as radars, mobile communication systems, GPS and home appliances have increased the electromagnetic waves interferences and magnetic contamination. The shielding of these waves is necessary in various applications to reduce the electromagnetic waves contamination. This contamination causes malfunction of electronic and telecommunication devices and also damages biological structures and living species. Widespread applications of electromagnetic waves shielding in the military industry can be referred to detection technology that camouflage and eliminate the target by removing the reflection signal from the target to the radar. These types of materials are called radar absorbing materials (RAM) which are used in various ways such as color coating. As a result, the purpose of the electromagnetic shielding materials is to produce a composite or coating that is used in camouflaging military industries, protecting living tissues from electromagnetic waves, and protecting electronic and telecommunication devices from disturbing waves. Nanocomposites containing conducting polymers have suitable properties for operation in this field. In this paper, the mechanism and function of EMI shielding materials made of polymer nanocomposite coatings are investigated.

Considering the importance of zinc oxide thin films (ZnO) in the fabrication of sensors and solar cells, this study aims to analyze and simulate the ZnO growth process by magnetron sputtering system. In this regard, the mathematical model in RSD2013 software was studied and then the results of the simulation of the ZnO growth process in plasma Ar/O2, have been analyzed. The accurate time-dependent differential equations used in this software, model some of the physical phenomena, including as the chemical absorption of reactive gas through the target and the substrate, the direct and knock-on implantation of reactive gas particles in the target, the formation of compound components in subsurface of the target, the deposition of sputtered particles on the substrate surface while returning the fraction of those particles to the target, and the redeposition of sputtered particles on the target surface. The results of the simulation will be helpful in improving the quality of fabricated ZnO thin films growth by reactive sputtering system.

The detection of acetone using a gas sensor at low concentrations is very important due to its application in the diagnosis of diabetes from breathing, whereas common gas sensors usually do not have such capability. Measurement of acetone in human exhalation is a valid method for diagnosing diabetes, but due to the small amount of acetone in breathing (less than 10 ppm), measuring it using commercial gas sensors has many challenges. In this study, acetone absorption was demonstrated by zeolite A and then the performance of the TGS2602 gas sensor was improved by using zeolite A in acetone gas detection. First, the sensor response was investigated in acetone concentration levels less than 10 ppm. The acetone-contaminated air was then passed through a zeolite substrate to absorb the acetone in the zeolite surface. Immediately after the adsorption stage, the zeolite was heated to 450 ◦C to release the absorbed acetone at once and to create a higher instantaneous concentration in the sensor chamber compared with the initial gas concentration. Due to the increase in concentration at the time of release, the sensor response was improved. With this method, the concentration of the acetone in the sensor chamber increased more than 50 times compared to the incoming acetone polluted air, which increased the sensor response by 7 times. To evaluate the efficiency of the built-in system, the effect of factors such as the mass of the zeolite used, the air flow rate, the adsorption/desorption temperature and the adsorption time were investigated. It has been observed that the sensor equipped with zeolite pre-concentrator, as an easy way, low-cost, and reliable method, increases the detection capability of the commercial sensor beyond the detection threshold.

Parameter estimation of photovoltaic cell model based on measured characteristics is difficult due to the nonlinear behavior of the diode in the model and its exponential relation. Existence of two diodes in double-exponential model makes this estimation more difficult. A hybrid optimization algorithm is implemented based on explorative characteristic of invasive weed algorithm, probabilistic models of distribution estimation and utilizing dispersion capacities of a mixed Gaussian–Cauchy distribution to estimate parameters of the single and double diode models of photovoltaic cells as an optimization problem. The fitness function is defined as the root mean square error between current-voltage curves of the model output and the measured points. The proposed method is implemented for a practical photovoltaic cell based on measured characteristic and the obtained results are compared with other 8 optimization algorithms. The statistical comparison of the difference between current-voltage curve of the optimized circuit model and the measurements verifies more suitable performance of the implemented algorithm compared with others.

Many factors affect the performance of lithium-ion battery-based systems (such as satellites and electric vehicles). One of the most important ones is the imbalance of battery cells due to continuous charging and discharging, the temperature of the battery environment and the process of making batteries. With the imbalance of the lithium-ion battery pack cells, their battery capacity and useful life are reduced, and in some cases, it even causes the battery pack to explode and explode. So far, various methods have been proposed to balance lithium-ion battery cells. This paper presents a new configuration for the lithium-ion battery balancing circuit. The proposed circuit has an automatic balancing process and the energy transfer in it occurs depending on the cell in both switching cycles. As a result, its balancing speed has increased significantly compared to similar designs. The proposed circuit for 42 watts in the simulated Orcad Capture software, which has an efficiency of 81% and an equalization time of 1.5 milliseconds (according to the modeled conditions of the battery pack in the simulation) at a voltage difference of 0.5 volts between weak and strong cells, and the results The result indicates the proper operation of the proposed circuit.

One of the ways to minimize fuel consumption in automobiles is to use cylinder-controlled valves. Traditional mechanical and hydraulic systems cannot achieve a fast time adaptation between the engine and the instantaneous position of the vehicle. With the separate control of each valve in the cylinder, it is possible to fully adjust the timing between the valves and instantaneous movement of the car. Sensor controllers usually have either a technical problem or are not economically viable. So the research of car companies is moving towards replacing the sensorless approach, to avoid overwhelming computation on the one hand, and to be more flexible against interference, on the other. Modern valves that work with electromagnetic force are known as electromagnetic valves. These valves are composed of two coiled inductors with a ferromagnetic core facing each other. This coiled ferromagnetic core creates an electrical-mechanical resonance system that provides the ground for the valves to move in the cylinder. In this article, the electronic controller part of the electromagnetic valve is analyzed, designed, and tested.

Sparse matrices appear in a number of problems related to science and engineering. The performance of algorithms designed for solving such problems depends significantly on the bandwidth of the problem matrix.  The bandwidth of a sparse symmetric matrix is the distance from the main diagonal beyond which all elements of the matrix are zero. Minimizing the bandwidth of a matrix is an NP-complete problem. Considering the importance of this problem, numerous algorithms have so far been presented for its solution among which metaheuristic algorithms have performed much better than other algorithms. The issue with using metaheuristic algorithms for addressing this problem is that the bandwidth size, which has been employed for comparing the quality of solutions produced by these algorithms in almost all previous studies, is not an appropriate measure, and therefore cannot direct the search process towards high-quality solutions. In this research, the above-mentioned issue is investigated, and a new approach is presented for dealing with it.

Network function virtualization (NFV) is an emerging technology. NFV enables networks to use software defined virtual functions such as firewalls, load balancers, and WAN accelerators, conventionally running on dedicated hardware. In order to provide NFV resources and meet SLA (Service Level Agreement) conditions, minimize energy consumption and utilize physical resources efficiently, dynamic resource allocation in cloud is an essential task. Since network traffic is changing rapidly, an optimized resource allocation strategy should consider resource auto-scaling property for NFV services.in order to scale cloud resources, we should predict NFV workload. Existing prediction methods are providing poor results for highly volatile and fluctuating time series such as cloud workloads. So, we propose a multiband decomposed wavelet prediction by GMDH ensemble algorithm for NFV traffic preciction. We evaluate the proposed model with two cloud workload traces. The results show the MAPE of prediction by the wavelet -GMDH method improved by 7.2% in compare to best perevious work in recent papers.

As the complexity of low-power designs grows, more efficient and automated tools are needed to functionally verify them. Simultaneous verification of both the design functionality and the consistency of power management controllers with the low-level power intent is a big challenge. This paper presents a method which attempts to resolve such a problem for complicated processors with tens of power domains. In order to ensure that the functionality of the processor after inserting power management controllers does not change, an efficient equivalence checking is performed between the low-power implementation model and its specification model. However, this kind of verification is not sufficient due to non-functional behavior of system-level power management strategies. Therefore, the proposed method checks the consistency between PMU and UPF by high-level power rules which are extracted from UPF. The experimental results show that the proposed method helps the designers not only to create a correct high-level power management controller but also to identify the low-power functional bugs in their designs.

Vision-based simultaneous localization and mapping in GPS-denied and indoor environments is one of the most important requirements for robot navigation. One of the major challenges to real-time implementation is the limited processing power on small flying robots. In this article, a method for enhancing RGB frames using histogram equalization and blind/reference less image spatial quality evaluator is presented. Some publicly available RGB-D dataset are employed to evaluate the proposed technique with our hybrid method using real-time appearance-based mapping. The problem is expressed as a graph configuration and is optimized using the Levenberg-Marquardt optimization approach. The results of evaluation on online data sets and experiments using designed flying robot indicate reduction in absolute translational error in comparison with the ground truth. Also, the accuracy and robustness of the proposed method have improved at least 17% with respect to environmental conditions and system noise.