Dhirgham Kamal Naji

@nahrainuniv.edu.iq

Electronic and Communications Department
Al-Nahrain University, Baghdad, Iraq



                 

https://researchid.co/dhirgham

RESEARCH INTERESTS

Antennas, Wave propagation, Communications Enginnering

12

Scopus Publications

270

Scholar Citations

10

Scholar h-index

10

Scholar i10-index

Scopus Publications

  • Compact Dual-Band Monopole Antennas with Fractal-Based Half-and Quarter-Circular Folded Loops for WiMAX and WLAN Applications
    Dhirgham Kamal Naji
    The Electromagnetics Academy
    : In this paper, two new types of dual-band antennas are presented: a coplanar waveguide (CPW)-fed fractal monopole antenna (FMA) and an asymmetric coplanar strip (ACS)-fed fractal half-monopole antenna (FHMA). These antennas are designed to operate in two distinct bands suitable for 3.5/5.5GHz WiMAX and 5.2/5.8GHz WLAN applications. Both antennas possess the property of self-similarity by employing half-and quarter-circular folded loops, respectively, which represent the antennas’ radiating elements. A design procedure based on a conventional circular patch antenna (CPA) is performed, with evolution steps leading to the achievement of the proposed two antennas with the above-mentioned features. To validate the design concept, two simulator programs (CST MWS and HFSS) were used to extract the simulated results regarding reflection coefficient s 11 , gain, efficiency, and radiation patterns. According to the agreement between the CST and HFSS simulated results, prototypes of the FMA and FHMA are fabricated on an FR4 substrate with a dielectric constant of 4.4, a height of 0.8mm, and overall sizes of only 26 × 20 mm 2 and 12 × 19 mm 2 , representing nearly 73% and 40% reduction in size, respectively, compared with the size of 26 × 33 mm 2 for the CPA. The simulated and measured s 11 results are in good agreement, illustrating the two antennas operating over the desired bands ( s 11 ≤ − 10 dB): 3.5-/5.5-GHz (3.40–3.69 and 5.25– 5.85GHz) WiMAX and 5.2/5.8-GHz (5.15–5.35 and 5.72–5.85GHz) WLAN. Furthermore, the peak realized gain values are greater than 2dBi, efficiency exceeding 90%, and nearly omnidirectional radiation at both bands. Based on the achieved results and antennas’ compactness, they can be highly recommended for the use in WLAN and WiMAX applications.

  • A Compact Dual-Band CPW-Fed Slotted-Ring Monopole Antenna with Circular Fractal Elements for WiMAX and C Bands Applications
    Dhirgham Kamal Naji
    The Electromagnetics Academy
    |This paper presents a new compact dual-band slotted-ring monopole antenna (SRMA) with circular fractal elements (CFEs) design for WiMAX and C bands applications. Good improvements are obtained in widening the upper-frequency band of the proposed antenna and in miniaturizing its overall size. Antenna miniaturization is accomplished by employing a coplanar waveguide (CPW)-fed fractal-shaped SRMA loaded at its inside and outside of the ring’s peripherals by two types of CFEs, namely, CFE1 and CFE2. The dual-band capability of antenna is realized by introducing in its ring’s center a circular slit to act as a key parameter for band rejection characteristic. The design procedure starts from a conventional circular monopole antenna (CMA), and evolution steps of antenna are performed until achieving the proposed CPW-fed SRMA with aforementioned features. The simulated results in terms of re(cid:13)ection coefficient, gain, efficiency, and radiation patterns are obtained by using CST MWS and HFSS programs. Due to the agreement between the CST and HFSS simulated results, the prototype of the antenna is fabricated on one side of an FR4 substrate with a volume of 20 (cid:2) 22 (cid:2) 0 : 8 mm 3 . Then the measured re(cid:13)ection coefficient is conducted, and it agrees well with the simulated counterpart. As observed from measurement, the antenna operates at two distinct bands of 3.15{3.75 GHz and 5.02{ 7.58 GHz that exhibits the proposed antenna to cover WiMAX, WLAN, C, 4G LTE, 5G, and Sub-6 GHz bands. Also, the proposed antenna exhibits an acceptable gain and efficiency across the operating bands along with omnidirectional radiation pattern.

  • Sidelobe Suppression of Antenna Array Using Harmony Search Algorithm
    Yaseen A. Mohammed and Dhirgham Kamal Naji
    IEEE
    In this paper, sidelobe suppression problem in the antenna radiation pattern is taken into consideration. Dealing with this optimization problem, an algorithm that is called Harmony Search Algorithm (HSA) is proposed and compared with existing and used algorithms in the literature, Particle Search Algorithm (PSO) and Artificial Bee Colony (ABC). A statistical comparison is carried out to examine the differences in performance. The results show that HSA can be used to suppress sidelobes with considerably short processing time.

  • Optimal Design of a Circularly Polarized Antenna for LTE Bands 42/43 Applications
    Saja Alaa Gheni and Dhirgham Kamal Naji
    The Electromagnetics Academy

  • Optimization Design Methodology of Broadband or Multiband Antenna for RF Energy Harvesting Applications
    Reham M. Yaseen, Dhirgham Kamal Naji, and Amina M. Shakir
    Progress In Electromagnetics Research B The Electromagnetics Academy

  • Miniature slotted semi-circular dual-band antenna for WiMAX and WLAN applications
    Dhirgham Kamal Naji
    Journal of Electromagnetic Engineering and Science Korean Institute of Electromagnetic Engineering and Science
    In this paper, a new approach is presented for designing a miniaturized microstrip patch antenna (MPA) for dual-band applications. The proposed MPA consists of a semi-circular patch radiator fed by a 50-Ω coplanar waveguide (CPW) structure with a tapered-ground plane for enhancing impedance bandwidth over the dual-band. By inserting a folded U-shaped slot into the semi-circular patch, the proposed antenna introduces an additional higher-order mode but does not modify the resonance frequency of the lower-order mode of the patch, yielding the desired dual-band response. For antenna miniaturization, the circular-shaped radiator of the reference antenna (RA) was converted into a semi-circular radiating patch. Agreement between CST and HFSS simulated results led us to manufacture a prototype of the designed antenna on one side of an inexpensive FR-4 substrate with an overall dimension of 17 × 18 × 0.8 mm<sup>3</sup>. The measured result in terms of reflection coefficient S11 confirms that the antenna operates in both 3.5 GHz (3.4–3.7 GHz) and 5.8 GHz (5.725–5.875 GHz) bands suitable for use in WiMAX and WLAN applications, respectively. Moreover, besides an area reduction of 32% compared with the RA counterpart, the proposed antenna has other features, a simple geometry, and is easy to manufacture in comparison with previously reported antenna structures.

  • Compact dual-band MIMO antenna system for LTE smartphone applications


  • Printed 5g mimo antenna arrays in smartphone handset for lte bands 42/43/46 applications
    Haneen Sobhi Aziz and Dhirgham Kamal Naji
    Progress In Electromagnetics Research M EMW Publishing

  • Optimization design methodology of miniaturized five-band antenna for RFID, GSM, and WiMAX applications
    Ayia A. S. A. Jabar and Dhirgham Kamal Naji
    The Electromagnetics Academy
    This paper presents a novel design methodology for the design and optimization of a miniaturized multiband microstrip patch antenna (MPA) for wireless communication systems. Two design steps are used to do that. In the first step, an initial antenna is designed by a trial and error approach to operate nearly in the desired frequency bands, but the level of impedance matching (s11 < −10 dB) for one or more bands is unsatisfactory, or some bands are uncovered by the antenna. The second design step is used after that to achieve optimized antenna by applying an optimization algorithm to effectively fine-tune the impedance matching of the initial deigned antenna to closely satisfy all the desired frequency bands. As an illustrative example, the proposed optimization methodology is used for designing a miniaturized multiband MPA suitable for operating at five different frequency bands, 915 MHz (RFID band), 1850 MHz (GSM band), (ISM — Industrial, Scientific, Medical), 2.45 and 5.8 GHz, and 3.5 GHz (WiMAX band). The proposed MPA used here is composed of two patch structures printed on both sides of an FR4 substrate occupying an overall size of just 28×28 mm2. The final optimized antenna is fabricated, and its simulated and measured results are coinciding with each other validating the design principle. Moreover, simulation antenna performance parameters, surface current distribution, realized peak gain, and efficiency besides the radiation patterns at the desired frequency bands are obtained using CST MWS.

  • Design of miniaturized quad-band dual-arm spiral patch antenna for RFID, WLAN and WiMAX applications
    Ayia A. S. A. Jabar and Dhirgham Kamal Naji
    The Electromagnetics Academy
    In this paper, a new design approach is presented for achieving a miniaturized quad-band microstrip patch antenna (MPA) suitable to be used for 915-MHz (UHF band), 2.45and 5.8-GHz (ISM band), and 3.5-GHz (WiMAX band). The proposed antenna is called modified square spiral antenna (MSSA) which is composed of a modified dual-arm square spiral patch strip structure and a taperedground plane with coplanar wave-guide (CPW)-fed configuration to feed this antenna, all printed on the top side of an FR4 substrate. The proposed antenna is designed through intermediate systematic design steps of antennas starting from a conventional strip-fed rectangular MPA and ending by achieving MSSA. A CST Microwave Studio (CST MWS) is used to model the designed antenna, and simulation results, in terms of return loss (S11), realized peak gain and efficiency, besides radiation patterns, are obtained. To validate the design concept, the antenna structure is fabricated, and the simulated and measured S11 results nearly coincide with each other. The proposed antenna is characterized by miniaturized size of 28 × 28 mm2, and based on measured −10-dB S11 result, MSSA has four bands, band 1: 915 MHz (872–929 MHz), band 2: 2.45-GHz (2395–2510 MHz), band 3: 3.5-GHz (3470–3550 MHz), and band 4: 5.8-GHz (5698–5900 MHz).

  • Design of a compact orthogonal broadband printed MIMO antennas for 5-GHZ ISM band operation
    Dhirgham Naji
    The Electromagnetics Academy
    This paper presents a new design approach for compact orthogonal broadband printed multiple-input multiple-output (MIMO) antennas based on a coplanar waveguide (CPW)-fed hexagonalring monopole antenna (HRMA) element. The design procedure of the basic radiating element is initiated from a stripline (SL)-fed circular monopole antenna (CMA). Then various antennas involved in the design evolution process are introduced to attain a compact CPW-fed HRMA. This basic antenna element has a compact size of 13 × 10 mm2, 50% smaller than SL-fed CMA, and a prototype of this antenna is built and tested. Based on HRMA element, compact twoand four-element MIMO antenna systems are designed, fabricated and experimentally demonstrated for 5-GHz ISM band operation. The MIMO antenna systems use orthogonally configured of identical closely spaced HRMA elements, with CPW-fed printed on one side of the substrate to achieve good isolation. Design simulation is carried out with the aid of Computer Simulation Technology Microwave Studio (CST MWS) and confirmed with High Frequency Structure Simulator (HFSS). The experimental results are in close agreement with the simulated ones, which validates the design principle. Based on experimental results, the two MIMO antenna systems have an impedance bandwidth of more than 2 GHz, good isolation of less than 15 dB, and a low envelope correlation coefficient of better than −26 dB across the frequency band of (4–6 GHz), which are suitable for 5-GHz MIMO applications.

  • Design and simulation of RFID aperture coupled fractal antennas
    Dhrgham. K. Naji, Jaber. S. Aziz, and Raad S. Fyath
    SAGE Publications
    Different fractal antennas based on aperture coupled feeding technique are studied, analysed and compared for size reduction, low profile, and good omini-dirctional pattern suitable for RFID applications. The results are used as a guideline to propose modified fractal shapes patch antennas having lower size reduction parameters. All the designed antennas are based on zero - order square patch antenna where different fractal geometries are introduced to miniaturize the size of antenna for 5.8 GHz band. A maximum reduction in patch antenna size of 59.80 % is achieved when using modified Minkowski pre-fractal patch antenna.

RECENT SCHOLAR PUBLICATIONS

  • Compact Dual-Band Monopole Antennas with Fractal-Based Half- and Quarter-Circular Folded Loops for WiMAX and WLAN Applications
    DK Naji
    Progress In Electromagnetics Research C 149, 12 2024

  • A Compact Dual-Band CPW-Fed Slotted-Ring Monopole Antenna with Circular Fractal Elements for WiMAX and C Bands Applications.
    DK Naji
    Progress In Electromagnetics Research C 137 2023

  • Sidelobe Suppression of Antenna Array Using Harmony Search Algorithm
    YA Mohammed, DK Naji
    2023 IEEE 12th International Conference on Communication Systems and Network 2023

  • “Electrically Loaded Resonators Based Miniaturized Fractal Filtering Printed Antennas
    MR Saadallah, DK Naji
    Journal of Optoelectronics Laser 41 (6), 522-534 2022

  • Optimal Design of a Circularly Polarized Antenna for LTE Bands 42/43 Applications
    G Saja, A., N Dhirgham, K.
    Progress In Electromagnetics Research C 120, 223-241 2022

  • Optimization Design Methodology of Broadband or Multiband Antenna for RF Energy Harvesting Applications
    RM Yaseen, DK Naji, AM Shakir
    Progress In Electromagnetics Research B 93, 169-194 2021

  • Design of A Dual-Wide Band BPF Utilizing Parallel Coupled Microstrip Lines and A Centered Arrow-Shaped Resonator
    AL Khudaraham, DK Naji
    Al-Nahrain Journal for Engineering Sciences 23 (2), 153-158 2020

  • Compact Dual-Band MIMO Antenna System for LTE Smartphone Applications
    HS Aziz, DK Naji
    Progress In Electromagnetics Research C 102, 13-30 2020

  • Miniature Slotted Semi-Circular Dual-Band Antenna for WiMAX and WLAN Applications
    DK Naji
    JOURNAL OF ELECTROMAGNETIC ENGINEERING AND SCIENCE 20 (2), 115-124 2020

  • Printed 5G MIMO Antenna Arrays in Smartphone Handset for LTE Bands 42/43/46 Applications
    HS Aziz, DK Naji
    Progress In Electromagnetics Research M 90, 167-184 2020

  • Optimization Design Methodology of Miniaturized Five-Band Antenna for RFID, GSM, and WiMAX Applications
    AASA Jabar, DK Naji
    Progress In Electromagnetics Research B 83, 177-201 2019

  • Design of Miniaturized Quad-Band Dual-Arm Spiral Patch Antenna for RFID, WLAN and WiMAX Applications
    AASA Jabar, DK Naji
    Progress In Electromagnetics Research C 91, 97-113 2019

  • Design of Compact Dual-band and Tri-band Microstrip Patch Antennas
    DK Naji
    International Journal of Electromagnetics and Applications 8 (1), 26-34 2018

  • Compact Design of Dual-band Fractal Ring Antenna for WiMAX and WLAN Applications
    DK Naji
    International Journal of Electromagnetics and Applications 6 (2), 42-50 2016

  • Design of a Compact Orthogonal Broadband Printed MIMO Antennas for 5-GHz ISM Band Operation
    DK Naji
    Progress In Electromagnetics Research B 64, 47–62 2015

  • An Alternative Look to Design of Wideband Planar Monopole Antennas Based on Parasitic Elements for C-band Wireless Applications
    DK Naji
    International Journal of Electromagnetics and Applications 4 (3), 61-69 2014

  • Plasma Effect on TM01 Mode Rectangular Microstrip Antenna for Space Telemetry and Telecomands Subsystems Applications
    AAA Mohammed, DK Naji
    International Journal of Engineering and Innovative Technology (IJEIT) 3 (2 2013

  • A Design Methodology for Miniaturized Fractal Slot RFID Antennas Using Particle Swarm Optimization
    DK Naji, JS Aziz, RS Fyath
    Journal of Emerging Trends in Computing and Information Sciences 4 (5), 477-489 2013

  • Fractal RFID Antenna Miniaturization
    DK Naji, JS Aziz, RS Fyath
    Lambert Academic Publishing 2013

  • A dual-band U-slot PIFA antenna with ground slit for RFID applications
    DK Naji, A Kareem, AA Mohammed
    Journal of Emerging Trends in Computing and Information Sciences 4 (2), 213-220 2013

MOST CITED SCHOLAR PUBLICATIONS

  • Miniature Slotted Semi-Circular Dual-Band Antenna for WiMAX and WLAN Applications
    DK Naji
    JOURNAL OF ELECTROMAGNETIC ENGINEERING AND SCIENCE 20 (2), 115-124 2020
    Citations: 48

  • Design of Miniaturized Quad-Band Dual-Arm Spiral Patch Antenna for RFID, WLAN and WiMAX Applications
    AASA Jabar, DK Naji
    Progress In Electromagnetics Research C 91, 97-113 2019
    Citations: 29

  • Design of Compact Dual-band and Tri-band Microstrip Patch Antennas
    DK Naji
    International Journal of Electromagnetics and Applications 8 (1), 26-34 2018
    Citations: 28

  • Compact Design of Dual-band Fractal Ring Antenna for WiMAX and WLAN Applications
    DK Naji
    International Journal of Electromagnetics and Applications 6 (2), 42-50 2016
    Citations: 27

  • Compact Dual-Band MIMO Antenna System for LTE Smartphone Applications
    HS Aziz, DK Naji
    Progress In Electromagnetics Research C 102, 13-30 2020
    Citations: 21

  • Design and Simulation of RFID Aperture Coupled Fractal Antennas
    DK Naji, JS Aziz, RS Fyath
    International Journal of Engineering Business Management 2, 1-14 2012
    Citations: 16

  • Design of a Compact Orthogonal Broadband Printed MIMO Antennas for 5-GHz ISM Band Operation
    DK Naji
    Progress In Electromagnetics Research B 64, 47–62 2015
    Citations: 15

  • A dual-band U-slot PIFA antenna with ground slit for RFID applications
    DK Naji, A Kareem, AA Mohammed
    Journal of Emerging Trends in Computing and Information Sciences 4 (2), 213-220 2013
    Citations: 14

  • Miniaturized Dual-Fractal Antenna Structure for RFID Tags
    DK Naji, RS Fyath
    International Journal of Electromagnetics and Applications 3 (4), 103-119 2013
    Citations: 11

  • Compact Broadband CPW-fed Taper-shaped Monopole Antenna with L-slots for C-band Applications
    DK Naji
    International Journal of Electromagnetics and Applications 3 (6), 136-143 2013
    Citations: 10

  • Printed 5G MIMO Antenna Arrays in Smartphone Handset for LTE Bands 42/43/46 Applications
    HS Aziz, DK Naji
    Progress In Electromagnetics Research M 90, 167-184 2020
    Citations: 9

  • Design of Miniaturized Fractal RFID Tag Antenna with Forced Impedance Matching
    DK Naji, JS Aziz, RS Fyath
    International Journal of Electromagnetics and Applications 2 (5), 129-139 2012
    Citations: 9

  • Optimization Design Methodology of Miniaturized Five-Band Antenna for RFID, GSM, and WiMAX Applications
    AASA Jabar, DK Naji
    Progress In Electromagnetics Research B 83, 177-201 2019
    Citations: 7

  • Optimization Design Methodology of Broadband or Multiband Antenna for RF Energy Harvesting Applications
    RM Yaseen, DK Naji, AM Shakir
    Progress In Electromagnetics Research B 93, 169-194 2021
    Citations: 6

  • Design and Simulation of Miniaturized Minkowski Fractal Aperture-Coupled Antenna for 5.8 GHz RFID Applications
    DK Naji, JS Aziz, RS Fyath
    Journal of Emerging Trends in Computing and Information Sciences 3 (7), 1013 2012
    Citations: 6

  • An Alternative Look to Design of Wideband Planar Monopole Antennas Based on Parasitic Elements for C-band Wireless Applications
    DK Naji
    International Journal of Electromagnetics and Applications 4 (3), 61-69 2014
    Citations: 5

  • A Compact Dual-Band CPW-Fed Slotted-Ring Monopole Antenna with Circular Fractal Elements for WiMAX and C Bands Applications.
    DK Naji
    Progress In Electromagnetics Research C 137 2023
    Citations: 4

  • Optimal Design of a Circularly Polarized Antenna for LTE Bands 42/43 Applications
    G Saja, A., N Dhirgham, K.
    Progress In Electromagnetics Research C 120, 223-241 2022
    Citations: 2

  • A Design Methodology for Miniaturized Fractal Slot RFID Antennas Using Particle Swarm Optimization
    DK Naji, JS Aziz, RS Fyath
    Journal of Emerging Trends in Computing and Information Sciences 4 (5), 477-489 2013
    Citations: 2

  • Sidelobe Suppression of Antenna Array Using Harmony Search Algorithm
    YA Mohammed, DK Naji
    2023 IEEE 12th International Conference on Communication Systems and Network 2023
    Citations: 1