arXiv subjects

Gholamreza Moradi

Publications and source records attributed to Gholamreza Moradi.

5 recordsLinked to original sources

arXiv2025

A Practical Approach to the Design of an S-Band Image-Rejecting Dual-Conversion Super-Heterodyne RF Chain of a Receiver Considering Spur Signals

This paper presents a typical design of the RF section of a radar receiver, the chain within a superheterodyne dual-conversion architecture. A significant challenge in this framework is the occurrence of spur signals, which negatively impact the dynamic range of the RF chain. When addressing this issue, the paper introduces an innovative approach to mitigate (or even wipe out) these undesired effects, utilizing two mutually verifying MATLAB codes. These codes have been tested with two distinct commercial mixers and could be applied to any superheterodyne configuration with various mixers. The presented method makes the Spurious-Free Dynamic Range (SFDR) of the chain the least different from the dynamic range of the chain. Also, the selection of other components gets optimized to align with spurious signals consideration, with explanations provided for these choices. Moreover, two filters of the RF chain, the second and the third, have been designed to reduce implementation costs. Various Microwave software and full-wave analyses were employed for detailed design and analysis, with the results compared to evaluate their performance.

eess.SP↗

arXiv2023

Performance Improvement of True Time Delay Based Centralized Beamforming Control with the Modulation Instability Phenomenon for Wireless-Array Antennas

This paper proposes a novel method to enhance the performance of the modulator for fifth-generation wireless communication (5G) by exploiting modulation instability (MI). We show that MI can reduce the bias voltage of the modulator ($V_π$) by generating carrier side-band gain, and increase the modulation BandWidth (BW), resulting in higher channel capacity, without changing the modulator structure. In receive mode of the array antenna, where the signal is very weak, high-frequency amplification is a high demanding solution to mitigate coverage issue. We also present a developed microwave-photonic beamforming bit-controller system for receiver-transmitter phased array antennas (PAAs), which are essential for high-capacity wireless communications like 5G. We employ a modulated frequency comb exploiting MI fiber to achieve an amplified true-time delay (TTD) technique for wide-coverage PAA beamforming and show that it can steer wideband high-frequency signal to a specific direction angle, avoiding beam-squint.

physics.optics↗

arXiv2023

An Accurate Model to Estimate 5G Propagation Path Loss for the Indoor Environment

This paper presents a new large-scale propagation path loss model to design a fifth-generation (5G) wireless communication system for indoor environments. Simulations for the indoor environment, for all polarization at non-line-of-sight (NLOS) and line-of-sight (LOS), which are performed per meter over a distance of 47 m between each of the separated transmitter antenna (TX) and the receiver antenna (RX) positions to compare better the proposed extensive flexible path loss model with previous models. All the simulations are conducted at the Abu-rayhan buildings at the Amirkabir University of Technology. The results demonstrated that the simple presented model with a single parameter denoted ZMS can predict the expansive path loss over distance more accurately. The values of the path loss exponent (PLE) for the LOS scenario are simulated and achieved at 3.63, 1.81, and 3.42 for the V-H, V-V, and V-Omni antenna polarizations, and for NLOS is 6.11, 4.21, and 5.23 at the 28 GHz frequency for all the polarization antenna type V-H, V-V, and V-Omni, appropriately.

cs.IT↗

arXiv2019

A Low-Profile Polarization-Adjustable Ring Slot Antenna for Millimeter-wave Applications

In this letter, a dual port antenna with polarization adjustability is proposed. The loading effect of four ring slots stimulates a hybrid mode in the antenna that generates eight magnetic monopoles with high gain in boresight. Due to symmetrical configuration, adding a 90 degree-rotated port provides a dual polarized antenna. Through controlling the phase difference between the two ports, six types of polarization can be demonstrated. A prototype is fabricated and measured in 28 GHz. Antenna shows a maximum gain of 13 dBi, X% bandwidth and a good cross-polarization level in all polarization states. Distinct features including low-profile, low-cost, single-layered and no feeding network makes the antenna a suitable candidate for upcoming millimeter-wave applications.

eess.SP↗

arXiv2015

A Perfect Terahertz Metamaterial Absorber

In this paper the design for an absorbing metamaterial with near unity absorbance in terahertz region is presented. The absorber's unit cell structure consists of two metamaterial resonators that couple to electric and magnetic fields separately. The structure allows us to maximize absorption by varying dielectric material and thickness and, hence the effective electrical permittivity and magnetic permeability.

physics.optics↗