Dhirgham Kamal Naji

@nahrainuniv.edu.iq

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

Dhirgham Kamal Naji


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https://researchid.co/dhirgham

RESEARCH INTERESTS

Antennas, Wave propagation, Communications Enginnering
14

Scopus Publications

313

Scholar Citations

11

Scholar h-index

11

Scholar i10-index

Scopus Publications

  • Antenna Design for Ultra-Wideband System Using a Fractal H-Shaped Structure for Enhanced Filtering and Narrowband Operation
    Noor K. Mohsin, Dhirgham K. Naji
    Al Nahrain Journal for Engineering Sciences, 2025
    In this work, for ultra-wideband (UWB) applications, a passive filter antenna with edge chamfering is investigated in this paper. The performance of an optimized UWB antenna design that achieves an advanced fractional impedance bandwidth of 102% is confirmed by simulation and experimentation. The performance of the antenna is improved by integrating a lowpass filter (LPF) into the fed line, which suppresses high-frequency radiation with a central frequency of 3.5 GHz (WiMAX), the UWB antenna has been transformed into a narrowband antenna, offering a 43.7% fractional bandwidth that spans the frequency range from 2.7 GHz to 3.9 GHz. A stepped impedance transmission line and an extended fractal H-shaped structure integrated in the microstrip feedline make up the filtering network. Using CST Microwave Studio (CST MWS), key performance parameters such as the radiation patterns, efficiency, gain, and reflection coefficient (S11) were examined. In its prototype, the antenna reduces its size by 5% and is made on a FR4 substrate with a permittivity coefficient of 4.3 and a loss tangent of 0.02. A maximum gain of 1.7 dBi and a peak efficiency of 78% at the center frequency were verified experimentally. The center frequency was verified experimentally. The tiny antenna, which measures 0.30λ₀ × 0.37λ₀ × 0.008λ₀, performs well and is appropriate for UWB applications. The design makes a significant addition to the realm of UWB technology by incorporating elements that improve its ability to adapt.
  • Design of a Compact Sub-6 GHz Wideband Filtering Patch Antenna without Extra Structure
    Noor Kareem Mohsin, Dhirgham Kamal Naji
    Progress in Electromagnetics Research C, 2025
    : This paper presents a new compact filtering patch antenna (FPA) design that achieves a wideband impedance bandwidth (IBW) without extra structure. It addresses the limitations of traditional FPAs, which often rely on extra elements to enhance bandwidth and filtering performance. The proposed FPA consists of a radiating patch with an inscribed circular slot, excited by a feedline integrated with a quarter-wavelength matching stripline, all located on the top side of an FR4 substrate. A partial ground plane with a T-shaped symmetrical branch strip is printed on the bottom side of the substrate. The combination of T-shaped strips and the matching stripline creates the first radiation-null f n 1 near the lower edge of the passband antenna’s gain response. Furthermore, the introduction of a circular slot into the radiating patch creates a second radiation-null f n 2 in the upper edge of the passband region. This not only enhances the IBW but also contributes to the antenna’s efficient filtering characteristics. Simulation tools CST Microwave Studio (MWS) and High-Frequency Structure Simulator (HFSS) are used to evaluate key performance parameters, including reflection coefficient ( s 11 ) , realized gain, and radiation patterns. A fabricated prototype validates these simulations, demonstrating a − 10 dB fractional IBW of 47.36% (2.9–4.7GHz). Based on CST and HFSS simulation results, the design exhibits high selectivity with suppression levels of over 22dB and 23.7dB at the lower and upper stopband edges, respectively, while maintaining a flat gain across the passband. The antenna also provides omnidirectional radiation patterns and has a compact size of 29 × 35 × 0 . 8 mm 3 , making it more promising for 5G sub-6GHz applications.
  • Compact Dual-Band Monopole Antennas with Fractal-Based Half-and Quarter-Circular Folded Loops for WiMAX and WLAN Applications
    Dhirgham Kamal Naji
    Progress in Electromagnetics Research C, 2024
    : 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
    Progress in Electromagnetics Research C, 2023
    |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, Dhirgham Kamal Naji
    Proceedings 2023 12th IEEE International Conference on Communication Systems and Network Technologies Csnt 2023, 2023
    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, Dhirgham Kamal Naji
    Progress in Electromagnetics Research C, 2022
  • Optimization Design Methodology of Broadband or Multiband Antenna for RF Energy Harvesting Applications
    Reham M. Yaseen, Dhirgham Kamal Naji, Amina M. Shakir
    Progress in Electromagnetics Research B, 2021
  • Miniature slotted semi-circular dual-band antenna for WiMAX and WLAN applications
    Dhirgham Kamal Naji
    Journal of Electromagnetic Engineering and Science, 2020
    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.
  • Printed 5g mimo antenna arrays in smartphone handset for lte bands 42/43/46 applications
    Haneen Sobhi Aziz, Dhirgham Kamal Naji
    Progress in Electromagnetics Research M, 2020
  • Compact dual-band MIMO antenna system for LTE smartphone applications
    Progress in Electromagnetics Research C, 2020
  • Optimization design methodology of miniaturized five-band antenna for RFID, GSM, and WiMAX applications
    Ayia A. S. A. Jabar, Dhirgham Kamal Naji
    Progress in Electromagnetics Research B, 2019
  • Design of miniaturized quad-band dual-arm spiral patch antenna for RFID, WLAN and WiMAX applications
    Ayia A. S. A. Jabar, Dhirgham Kamal Naji
    Progress in Electromagnetics Research C, 2019
  • Design of a compact orthogonal broadband printed MIMO antennas for 5-GHZ ISM band operation
    Dhirgham Naji
    Progress in Electromagnetics Research B, 2015
  • Design and simulation of RFID aperture coupled fractal antennas
    Dhrgham. K. Naji, Jaber. S. Aziz, Raad S. Fyath
    International Journal of Engineering Business Management, 2012

RECENT SCHOLAR PUBLICATIONS

  • Antenna Design for Ultra-Wideband System Using a Fractal H-Shaped Structure for Enhanced Filtering and Narrowband Operation
    NK Mohsin, DK Naji
    Al-Nahrain Journal for Engineering Sciences 28 (4), 515-523 , 2025
    2025
  • Design of a Compact Sub-6 GHz Wideband Filtering Patch Antenna without Extra Structure
    NK Mohsin, DK Naji
    Progress In Electromagnetics Research C 155, 165-175 , 2025
    2025
    Citations: 1
  • 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
    2024
    Citations: 1
  • 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
    2023
    Citations: 6
  • Sidelobe Suppression of Antenna Array Using Harmony Search Algorithm
    YA Mohammed, DK Naji
    2023 IEEE 12th International Conference on Communication Systems and Network … , 2023
    2023
    Citations: 2
  • “Electrically Loaded Resonators Based Miniaturized Fractal Filtering Printed Antennas
    MR Saadallah, DK Naji
    Journal of Optoelectronics Laser 41 (6), 522-534 , 2022
    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
    2022
    Citations: 2
  • 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
    2021
    Citations: 7
  • 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
    2020
  • Compact Dual-Band MIMO Antenna System for LTE Smartphone Applications
    HS Aziz, DK Naji
    Progress In Electromagnetics Research C 102, 13-30 , 2020
    2020
    Citations: 26
  • 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
    2020
    Citations: 60
  • 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
    2020
    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
    2019
    Citations: 7
  • 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
    2019
    Citations: 36
  • Design of Compact Dual-band and Tri-band Microstrip Patch Antennas
    DK Naji
    International Journal of Electromagnetics and Applications 8 (1), 26-34 , 2018
    2018
    Citations: 35
  • 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
    2016
    Citations: 28
  • 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
    2015
    Citations: 15
  • 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
    2014
    Citations: 5
  • 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
    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
    2013
    Citations: 2

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
    2020
    Citations: 60
  • 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
    2019
    Citations: 36
  • Design of Compact Dual-band and Tri-band Microstrip Patch Antennas
    DK Naji
    International Journal of Electromagnetics and Applications 8 (1), 26-34 , 2018
    2018
    Citations: 35
  • 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
    2016
    Citations: 28
  • Compact Dual-Band MIMO Antenna System for LTE Smartphone Applications
    HS Aziz, DK Naji
    Progress In Electromagnetics Research C 102, 13-30 , 2020
    2020
    Citations: 26
  • 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
    2012
    Citations: 18
  • 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
    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
    2013
    Citations: 14
  • 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
    2013
    Citations: 11
  • Miniaturized Dual-Fractal Antenna Structure for RFID Tags
    DK Naji, RS Fyath
    International Journal of Electromagnetics and Applications 3 (4), 103-119 , 2013
    2013
    Citations: 11
  • 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
    2012
    Citations: 11
  • 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
    2020
    Citations: 9
  • 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
    2021
    Citations: 7
  • 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
    2019
    Citations: 7
  • 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
    2023
    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
    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
    2014
    Citations: 5
  • Sidelobe Suppression of Antenna Array Using Harmony Search Algorithm
    YA Mohammed, DK Naji
    2023 IEEE 12th International Conference on Communication Systems and Network … , 2023
    2023
    Citations: 2
  • 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
    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
    2013
    Citations: 2