Gholamreza Moradi

Amirkabir University of Technology

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Abdolali Abdipour

Amirkabir University of Technology

Reza Sarraf Shirazi

Amirkabir University of Technology

Rashid Mirzavand

University of Alberta

Ayaz Ghorbani

Amirkabir University of Technology

Mohammad Saeid Ghaffarian

University of Alberta

Pedram Mousavi

University of Alberta

Masoud Movahhedi

Yazd University

Somayeh Khajepour

Amirkabir University of Technology

Ahad Tavakoli

Amirkabir University of Technology

Mohammad Mahdi Honari

University of Wisconsin–Madison

Cooperative Institutions

Amirkabir University of Technology

117

University of Tehran

Sharif University of Technology

University of Alberta

Chinese Academy of Sciences

Iran University of Science and Technology

Islamic Azad University, Tehran

Shahid Beheshti University

K.N.Toosi University of Technology

ICT Research Institute

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An ultra-wideband Rotman lens using modified dummy sidewalls

IEICE Electronics Express (2011)

Moein Nazari Ahmad Mortezaie Ayaz Ghorbani Gholamreza Moradi

A wideband design model for 4×4 microstrip Rotman lens is presented, with a precise behavior of return loss of the ports and their phase centers. The procedure for choosing the optimum geometrical parameters of lens and modifying the curvature of sidewalls yield a very wideband lens. Based on the presented model, a prototype has been built for the true time delay phasing of an antenna array for the frequency range from 8GHz to 26GHz. The fabricated 4×4 Rotman lens has an average amplitude error of 0.5dB and phase errors of 2 degree. All the beams have a fixed position in frequency band and the maximum deviation of the beams from the ideal position is less than 0.65 degree.

Wideband

Phaser

Position (finance)

Return loss

10.1587/elex.8.1228

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Citations (3)

Wideband Vertically Polarized Antenna With Endfire Radiation for 5G Mobile Phone Applications

IEEE Antennas and Wireless Propagation Letters (2020)

Maryam Faizi Khajeim Gholamreza Moradi Reza Sarraf Shirazi Shuai Zhang Gert Frølund Pedersen

This letter presents a wideband slotted substrate integrated waveguide (SIW) antenna for millimeter-wave (mm-wave) fifth-generation (5G) mobile handset applications. The antenna is vertically polarized and has a small clearance of 3.3 mm. To realize a wide operating bandwidth, two sets of vias are employed to perform a change in SIW height. Furthermore, a pair of U-shaped slots is used in both top and bottom faces of SIW to improve impedance matching and front-to-back radiation ratio. The antenna achieves a measured -6 dB bandwidth of 35.7% (23.4-33.6 GHz) and a -10 dB bandwidth of 17.4% (26.2-31.2 GHz). The beamforming capability of the antenna array is investigated. The antenna array has good scanning performance and achieves large spatial coverage.

Wideband

10.1109/lawp.2020.3009097

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Citations (35)

Modeling and Jitter Improvement of SRD-Based Ultra-Wideband Pulse Generator

IEEE Transactions on Microwave Theory and Techniques (2014)

Ali Kheirdoost Gholamreza Moradi Eessam Elkholy Abdolali Abdipour Aly E. Fathy

Step recovery diode (SRD)-based ultra-wide band (UWB) pulse generators (PGs) suffer from jitter caused by AM-to-PM conversion, SRD shot noise, and clock jitter. These noise sources significantly impact the accuracy of UWB systems if very high precision ranging/positioning is required. Jitter behavior caused by the transmitter and receiver is mostly detrimental in the equivalent time-sampling receiver. Thus, a mathematical model for simulation of the jitter and amplitude variation effect in the equivalent time-sampling technique has been developed and used in SystemVue simulations. A criterion as an estimate of system accuracy is defined as signal-to-distortion ratio (SDR) and used. Similarly, a model for AM and PM noise analysis for an SRD-based UWB PG is developed that was validated experimentally. In addition, SRD shot-noise contribution on output jitter was evaluated using the proposed model. Based on these models, methods to reduce the output jitter of the system have been recommended. Simulation showed that clock jitter and SRD shot noise led to pronounced output jitter, with shot noise the primary cause. For a typical SRD-based UWB PG, an output jitter of around 3 ps has been achieved using improvement techniques based on the proposed method, compared to a 15-ps jitter before improvement. These measured results are in good agreement with our predictions.

Wideband

10.1109/tmtt.2014.2331290

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Citations (11)

Performance Amelioration of an Active Integrated Spiral Antenna System for UWB Applications

International workshop on Antenna Technology: Small and Smart Antennas Metamaterials and Applications (2007)

Mahdi Jalali Abdolali Abdipour Ahad Tavakoli Gholamreza Moradi

This paper describes the implementation of an active integrated spiral antenna for UWB (ultra-wideband) applications. By integrating a low-noise amplifier with antenna, the voltage standing wave ratio (VSWR) can be kept low for a large bandwidth and this antenna indicate a 13 dB improvement in gain compared with one using a passive antenna with the same design, resulting in an improved spiral antenna performance for UWB. For the designed circuit in the UWB frequency range (3.1-10.6 GHz), the gain of the LNA is better than 13 dB, its noise figure is less than 3 dB, S ₁₁ and S ₂₂ are less than -13 dB, respectively

Spiral antenna

10.1109/iwat.2007.370140

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Citations (2)

Phaseless near‐field to far‐field transformation based on source current reconstruction and signal subspace optimization

International Journal of RF and Microwave Computer-Aided Engineering (2021)

Mohammad Bod Gholamreza Moradi Reza Sarraf Shirazi

In this article, an algorithm for the phaseless near-field (NF) to far-field (FF) transformation based on the source current reconstruction method (SRM) is proposed. The algorithm starts with decomposing the equivalent currents of the antenna under test (AUT) into a deterministic and ambiguous current. The deterministic portion of the current is determined from the phaseless signal subspace-based optimization method (SOM), while several iterative forward-backward propagations add the ambiguous portion. It is shown that with the SOM initialization, no further prior information about the antenna under test is needed and the iterative scheme can converge to the desired result within a few iterations. A simulation and a measurement example validate the proposed algorithm. All results show an accurate, fast, and stable phaseless field transformation is obtained.

SIGNAL (programming language)

Signal subspace

10.1002/mmce.22913

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Citations (1)

Improvements in the Noise Theory of the MMIC Distributed Amplifiers

IEEE Transactions on Microwave Theory and Techniques (2008)

Emad Hamidi Mahmoud Mohammad‐Taheri Gholamreza Moradi

Exact and simple expressions have been obtained for the intrinsic noise figure of monolithic microwave integrated circuit distributed amplifiers (DAs). The method has been applied on both MESFET and HBT DAs. It has been shown that the complexity of the obtained formulas is much less than that of the previously published literature. The results of the new theory are then compared with that of the previous theories and it has been shown that the results exactly match.

MESFET

Distributed amplifier

Heterojunction bipolar transistor

Network Analysis

Microwave engineering

10.1109/tmtt.2008.927310

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Citations (6)

Modified Transition for Substrate Integrated Waveguide(SIW) Structures

Bulletin de la Société Royale des Sciences de Liège (2016)

Amirhossein Askarian Gholamreza Moradi

In this paper a new X-band SIW to Microstrip transition based on SIW structure is proposed. The recent transition has better performance in terms of return loss than those of in the traditional Microstrip tapers transition. Chebyshev multi-section matching transformer is utilized in order to inter-stage network between Microstrip and SIW, whereof it is the most optimum and efficient in matching networks theory. The 5th-order Chebyshev polynomial is employed to get about 30 dB return loss. For this purpose, curve-fitting technique is utilized to obtain a mathematical function based on Chebyshev polynomial which presents the optimum position of vias in SIW transition. In order to validation of theoretical method and results, a full-wave simulation is carried out by CST STUDIO SUITE software.

Return loss

10.25518/0037-9565.5281

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Citations (0)

Signal and noise improvement of a distributed FET mixer

Gholamreza Moradi Abdolali Abdipour Forouhar Farzaneh

A traveling wave distributed mixer is studied. It is shown that increasing the drain-source capacitances in a distributed FET mixer simultaneously improves its conversion gain and noise figure. Besides, it is shown that proper loading of input and output elements can improve the device performance. The simulation results are well matched with the measurements and also with the results of the existing certified simulators.

SIGNAL (programming language)

10.1109/edmo.2002.1174972

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New trends for mm-wave FET structures

Abdolali Abdipour Gholamreza Moradi

This paper discusses some new viewpoints of signal and noise performances of mm-wave FETs. The effect of reactive (capacitive and inductive) electrode loading and the influence of the slicing procedure in sliced modeling of mm-wave FETs have been studied. The proposed model takes into account not only the active coupling elements but also the capacitive and inductive coupling elements of the device. The results show that a proper sliced model with a suitable electrode loading may improve the device signal and noise performances.

Capacitive coupling

SIGNAL (programming language)

Inductive coupling

10.1109/apmc.1999.833690

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Citations (0)

FULL-WAVE SEMICONDUCTOR DEVICES SIMULATION USING ADI-FDTD METHOD

Progress In Electromagnetics Research M (2010)

Rashid Mirzavand Abdolali Abdipour Gholamreza Moradi Masoud Movahhedi

10.2528/pierm10010604

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Citations (23)