Mohsen Hayati | Razi University of Kermanshah, Iran (original) (raw)

Papers by Mohsen Hayati

Wireless networks, Mar 8, 2024

Scientific Reports, Jan 14, 2024

This paper introduces a novel design approach based on the dual-band harmonic control circuit and... more This paper introduces a novel design approach based on the dual-band harmonic control circuit and bandpass filter for dual-band power amplifiers. The circuit schematic of the proposed approach is constructed using four resonators and RFC inductors. The first two resonators are dedicated to controlling the second harmonics, while the third and fourth resonators serve as a harmonic blocker, allowing only the main signals to pass through to the load. Subsequently, all components are replaced by circuits based on microstrip elements, forming the proposed OMN. This OMN includes a novel wideband bias circuit, elliptically coupled resonators, and a new dual-band bandpass filter. To ensure compatibility with the transistor, a compensator line has been integrated. As a result, a dual-band power amplifier has been fabricated and measured at two operating frequencies, 2.1 GHz and 2.91 GHz. The measured values for drain efficiency, output power, and power gain at 2.1 GHz are 75.98%, 37.5 dBm, and 12.5 dB, respectively. Similarly, at 2.91 GHz, these values are 75.73%, 37.24 dBm, and 12.24 dB, respectively. Dual-band microwave power amplifiers (PA) represent a critical advancement in contemporary microwave technology. These amplifiers possess the remarkable capability to amplify microwave signals in two distinct frequency bands simultaneously. In the rapidly evolving landscape of wireless communication and data transmission, they play an integral role, guided by the latest references 1-12 and cutting-edge research. These amplifiers not only enhance signal strength but also contribute significantly to the efficiency and reliability of microwave systems. Recently, several concepts have been employed in the design of dual-band PAs, each addressing the enhancement of a particular parameter. Designing amplifiers that can operate in two frequency bands requires the use of special harmonic control and biasing circuits. So that, unlike wideband amplifiers, they only operate in two specific bands, and other frequencies between the two bands are blocked. In this regard, the proposed schematic circuit for designing a dual-band PA based on compact elements is illustrated in Fig. 1a. In this circuit, two inductors, RFC1 and RFC2, are utilized; each resonating at one of the amplifier's operating frequencies. In 1-4 radial stub structures are employed as biasing circuits specifically designed for dual-band amplifiers. Additionally, the proposed circuit in Fig. 1a employs two inductive-capacitive resonator circuits, each resonant at the second harmonic of amplifier's operating frequency (@2f o1 or @2f o2), while jointly controlling both second harmonics. In essence, this section represents the harmonic control circuit (HCC), which has been previously implemented using various techniques 5-10. The presented HCC in 5 used two lines, each having a total length equal to a quarterwavelength at each of the amplifier's operating frequencies. In 6 , the design incorporates 8 quarter-wavelength lines as HCC. The presented HCC in 7 is based on the network parameter extraction method, while 8 utilizes the precise harmonic control approach. The HCCs of 9 and 10 relies on impedance transformers and reactance compensation networks, and centered around a flexible network configuration with crossed transmission lines, respectively. In 13 , instead of using harmonic rejection filters, a narrow-band diplexer is used. Furthermore, in the circuit depicted in Fig. 1a, two resonators, each comprised of an inductor and a capacitor in parallel, are evident. These resonators, resonating at the operational frequencies of the amplifier (@f o1 or @f o2), effectively block all harmonics, with the exception of the first harmonic. These results in the generation of pure sinusoidal signals delivered to the load. In essence, this section serves as a harmonic blocker circuit, permitting only the passage of the first harmonics. Regrettably, prior research has given less attention to this aspect of dual-band PAs, posing a significant challenge in the design of an alternative circuit for this particular function.

Wireless Networks, Jul 29, 2021

Aeu-international Journal of Electronics and Communications, Sep 1, 2021

Abstract A low pass filtering power divider (LPFPD) with good isolation and extensive suppression... more Abstract A low pass filtering power divider (LPFPD) with good isolation and extensive suppression of harmonics has been presented. In the design of the Wilkinson power divider, a new structure has been proposed by replacing two quarter wavelength stubs of the conventional Wilkinson power divider (CWPD) with a combination of trapezoidal, circular, and rectangular resonators. In this power divider, the undesired harmonics have been suppressed. The WPD has a miniaturized structure, which the normalized circuit size (NCS) is 0.1 λg × 0.08 λg and the operating frequency is located at 1.67 GHz. Ultimately, the power divider has been fabricated and tested. The return loss is about 28 dB and the isolation between the output ports is higher than 23 dB. The experimental results mimic the early design results. Thus, the proposed WPD has a good performance and can be used in many communication systems.

Micro and nanostructures, Mar 1, 2022

Microwave and Optical Technology Letters, Feb 27, 2014

The subnominal condition is defined as only the zerocurrent switching (ZCS) condition is satisfie... more The subnominal condition is defined as only the zerocurrent switching (ZCS) condition is satisfied. On the other hand, as the Figure 5 BER versus SNR plot for Rayleigh channel with MISO OFDM-QPSK system.

The Applied Computational Electromagnetics Society Journal (ACES), 2015

In this paper, the invasive weed optimization technique for compacting a microstrip elliptic low ... more In this paper, the invasive weed optimization technique for compacting a microstrip elliptic low pass filter is proposed and validated. At the first step, the invasive weed optimization (IWO) technique is used to replace the shunt resonators transmission lines of the conventional filter with arbitrary n-segments Step Impedance Transmission Lines (SITLs) for compacting it. To validate the proposed method, the shunt resonator transmission lines of a seventh-order elliptic lowpass filter are replaced with proper SITLs which cause more than 30% compactness in this step. Then the IWO technique is applied on the general filter configuration to design a wideband harmonic suppression and compact elliptic low pass filter. This method extends the stop band bandwidth more than 8.5 f0 and also increases the compactness to 47%. The measurement results of the final optimized fabricated filter are in good agreement with the simulation ones.

International Journal of Electrical and Computer Engineering, Apr 26, 2007

In this paper, the application of neural networks to study the design of short-term temperature f... more In this paper, the application of neural networks to study the design of short-term temperature forecasting (STTF) Systems for Kermanshah city, west of Iran was explored. One important architecture of neural networks named Multi-Layer Perceptron (MLP) to model STTF systems is used. Our study based on MLP was trained and tested using ten years (1996-2006) meteorological data. The results show that MLP network has the minimum forecasting error and can be considered as a good method to model the STTF systems.

A new design of microstrip lowpass filter with wide stopband and sharp roll-off is presented. The... more A new design of microstrip lowpass filter with wide stopband and sharp roll-off is presented. The structure consists of a rhombic shaped resonator. For high and wide rejection level in stopband, the rhombic shaped suppressing cells are added to the resonator structure. To achieve a filter with a small size the transmission lines are folded. The overall figure of merit of the presented filter has high value equal to 975. The proposed lowpass filter with-3 dB cutoff frequency at 1.5 GHz is designed, fabricated and measured. The measured results are in good agreement with the simulated results.

International Conference on Communications, Jul 23, 2010

In this paper, a new model for further reducing the size and increasing the bandwidth (BW) of a c... more In this paper, a new model for further reducing the size and increasing the bandwidth (BW) of a class miniaturized elliptic-function low-pass filter has been presented. A compact elliptic-function low pass filter using microstrip stepped-impedance semi-hairpin resonators has been developed and a multiple cascaded filter using semihairpin resonators has been designed. The overall BW of the proposed low-pass filter has been shown to be increased by more than 40% with a size reduction about 80% compared with the conventional ones.

International Journal of Microwave and Wireless Technologies, Aug 8, 2019

In this paper, a microstrip lowpass filter adopting two main resonators with steep transition ban... more In this paper, a microstrip lowpass filter adopting two main resonators with steep transition band and wide rejection band has been introduced. The first main resonance cell consists of meandered transmission lines which are loaded by modified T-shaped patches. The second main resonator is composed of high-impedance lines loaded by polygon patches. To obtain a steep skirt performance, the first and second resonators have been combined. Moreover, employing eight high–low impedance folded stubs and two rectangular open-stubs as suppressing cells has resulted in improving the stopband features. To comprehend the frequency behavior of the employed resonators and also their combination, the formulas of the transmission coefficient, reflection coefficient, and the transmission zeros of their equivalent LC circuits have been extracted, separately. According to the measurement results, the −3 dB operating frequency of this filter is 1.65 GHz. Moreover, a relative stopband bandwidth equal to 166% with a corresponding attenuation level of 23 dB and a sharp roll-off rate (393.61 dB/GHz) have been achieved. In the passband region from DC to 1.632 GHz, the insertion loss and return loss are better than 0.0763 and 15.85 dB, respectively, proving an acceptable in-band performance. Finally, the implemented structure brings about a high figure-of-merit equal to 81 672.

International Journal of Electronics, Oct 18, 2016

ABSTRACT In this paper, a class E power amplifier (PA) with operating frequency of 1 MHz is prese... more ABSTRACT In this paper, a class E power amplifier (PA) with operating frequency of 1 MHz is presented. MOSFET non-linear drain-to-source parasitic capacitance, linear external capacitance at drain-to-source port and linear shunt capacitance in the output structure are considered in design theory. One degree of freedom is added to the design of class E PA, by assuming the shunt capacitance in the output structure in the analysis. With this added design degree of freedom it is possible to achieve desired values for several parameters, such as output voltage, load resistance and operating frequency, while both zero voltage and zero derivative switching (ZVS and ZDS) conditions are satisfied. In the conventional class E PA, high value of peak switch voltage results in limitations for the design of amplifier, while in the presented structure desired specifications could be achieved with the safe margin of peak switch voltage. The results show that higher operating frequency and output voltage can also be achieved, compared to the conventional structure. PSpice software is used in order to simulate the designed circuit. The presented class E PA is designed, fabricated and measured. The measured results are in good agreement with simulation and theory results.

Aeu-international Journal of Electronics and Communications, Nov 1, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Iete Journal of Research, Jul 25, 2019

In this paper, the design of a novel efficient QCA-based universal logic gate (ULG) is presented.... more In this paper, the design of a novel efficient QCA-based universal logic gate (ULG) is presented. Compact and efficient implementation layout with only one clock phase delay and also the implementation of the 13 standard functions without extra ULG or gate are the advantages of the proposed ULG. The results show that the proposed ULG is an efficient tool in designing any QCA circuit. Also, an accurate artificial neural network (ANN) model of the proposed ULG is presented. This model can be simply imported into any circuit simulators such as HSPICE, MATLAB Simulink and etc., for modeling and simulation of QCA circuits at the Gate level with high precision in a short time.

Optical Engineering, Sep 25, 2020

Abstract. A dual, wide band pass metal–insulator–metal plasmonic filter based on nanocomposite me... more Abstract. A dual, wide band pass metal–insulator–metal plasmonic filter based on nanocomposite media in the near-infrared band, 0.75 to 2.5 μm wavelength range, is proposed. Simulation results show that the pass bands can be adjusted to proper ranges by changing the size of the device and the relative permittivity of the dielectric region. Due to the importance of small structures in optical integration, we focused on tuning the transmitted bands by changing the dielectric relative permittivity. Realization of any desired relative permittivity for the dielectric region may be difficult using general dielectrics. In this way, the dielectric region is designed based on nanocomposite media, which no previous studies have focused on. Dielectric region is realized by a polymeric medium, poly-methyl-methacrylate, that consists of random distribution of guest spherical silver nanoparticles. The proper permittivity and consequently, the desired pass bands are obtained by changing the fill fraction of guest nanoparticles.

IEEE Journal of Emerging and Selected Topics in Power Electronics, Mar 1, 2018

In this paper, design and analysis using analytical expressions for the inverse class-E power amp... more In this paper, design and analysis using analytical expressions for the inverse class-E power amplifier (PA) operating at the outside nominal operation, i.e., class-En PA, is presented. This operation is defined as non-zero current switch (n-ZCS) and non-zero derivative current switch (n-ZDCS) conditions. The generalized design equations as a function of design specifications, load-resistance and a given dc-supply voltage are derived. Two degrees of the design freedom achieved thanks to n-ZCS and n-ZDCS that are utilized for the simultaneous satisfaction of design specifications, such as peakswitch-voltage and peak-switch-current along with a given loadresistance. The output power capability is affected by n-ZCS and n-ZDCS conditions, which can be obtained in the desired value using the controlled adjustment of introduced deviation parameters. In order to prove the validity of the proposed design methodology, an inverse class-E PA operating in 2 GHz with output power of 23 dBm is implemented in 0.25-µm AlGaAs-InGaAs pHEMT technology. There is a close agreement between the theoretical and simulation results and the measurements of the fabricated prototype PA, which proved the validity of the obtained design expressions. Index Terms-High-efficiency, inverse class-E power amplifier, non-zero current switch (n-ZCS), non-zero derivative current switch (n-ZDCS), monolithic microwave integrated circuit (MMIC), outside nominal.

Journal of Computational Electronics, Mar 7, 2014

In order to further development of the microelectronic systems and to achieve the circuits with h... more In order to further development of the microelectronic systems and to achieve the circuits with higher speed, higher density and lower power consumption, new technologies to replace the conventional CMOS technology must be introduced. Quantum-dot cellular automata (QCA) is an emerging nanotechnology that provides a new method for computation at the nanoscale regime. In this paper, two methods e.g. artificial neural network and a mathematical algorithm based on the QCA cell-cell response function named Tansig method are used for the modeling and simulation of QCA circuits at the cell level. The accuracy and performance of the proposed methods are analyzed through few circuits. The results of these two approaches are compared with each other and QCADesigner software. The results show the feasibility and acceptable accuracy of these types of simulations. Also, these methods enable the simulation of large QCA circuits at the cell level with acceptable precision in a short time with the ability to implement in other circuit simulators such as HSPICE and so on.

Optik, Feb 1, 2018

In this paper, the performance of a double junction solar cell with a novel structure, i.e., made... more In this paper, the performance of a double junction solar cell with a novel structure, i.e., made up of two layers of copper zinc tin sulfide (CZTS) & copper indium gallium diselenide (CIGS) and two layers of anti-reflector coatings namely zinc telluride (ZnTe) and cadmium sulfide (CdS) on the top layer of the cell are studied and optimized. To obtain an optimized performance, the effect of CIGS band gap changes on the efficiency is studied. For establishing the current matching in two sub-cells, the effect of thickness of ZnTe and CdS anti-reflectors layers is investigated for optimum short circuit current. The optimized proposed double junction CZTS/CIGS solar cell has an efficiency and fill factor of 45.37 percent and 86.37 percent, respectively.

With the advancement of electronic device technology and the development of nanometer dimensions ... more With the advancement of electronic device technology and the development of nanometer dimensions in this field, as well as decreasing dimensions for higher integration and better device performance, power consumption as well as more sophisticated functions require the use of material with physical and chemical properties. Suitable for nanometers, it is becoming increasingly popular as carbon nanotubes are a viable alternative. With the increase in the electric charge density, the emergence of quantum phenomena, such as quantum tunneling, has created problems for the creation of destructive and leaky currents. Meanwhile, structure simulation plays a key role in understanding and improving device performance. This article uses MOSCNT 1.0 software. This software is programmed with MATLAB code and is executable with MATLAB software The Poisson-Schrödinger equations can be solved automatically using the Non-Equilibrium Green Function (NEGF) by MOSCNT 1.0 software. In fact, MOSCNT 1.0 software presents a mathematical model describing the mechanism of Carbon Nanotube Field Effect Transistors (CNFETs) operation. Simulations by solving all equations are able to derive some of the characteristics of a carbon nanotube effect transistor, including I-V diagram.

Electronics Letters, Jul 1, 2017

Background and Objectives: In this paper, an ultra-wide stopband microstrip low pass filter (LPF)... more Background and Objectives: In this paper, an ultra-wide stopband microstrip low pass filter (LPF) with sharp roll-off and compact size is designed and fabricated. Also, proposed filter is designed, simulated, optimized, fabricated and measured and we can see a good agreement between the simulations and measurement results. Methods: T-shaped and stepped impedance have been used, because these structures have a very small dimensions. This method provides a suitable cut off frequency. Results: The cut off frequency at-3dB is 3.1GHz. In the proposed structure, the insertion loss is lower than 0.12dB and the return loss is greater than 15dB. In order to achieve a-20dB attenuation level in the stopband, a modified L-shaped structure is utilized. This filter has an ultra-wide stopband that is expanded from 3.37GHz to 37.5GHz. Also, the suppression level is greater than-20dB. The fabricated LPF has a size about 16.6 × 13.5 mm 2 which is equal to 0.28ƛg × 0.22ƛg, where ƛg is the guided wavelength at 3.1GHz, which is very small. Conclusion: A microstrip LPF with 3.1GHz cutoff frequency consisting of Tshaped and stepped impedance resonators has been proposed, simulated and fabricated. The transition band (-3 to-40dB) is 0.38GHz, which is a very sharp response. The stopband of the proposed filter is from 3.37 to 37.5 GHz which is equal to 12.1f c. There was a significant agreement between the simulation and the measured results. With all these features, these filters are widely used in wireless communication systems.