Dhirgham Kamal Naji
@nahrainuniv.edu.iq
Electronic and Communications Department
Al-Nahrain University, Baghdad, Iraq
RESEARCH INTERESTS
Antennas, Wave propagation, Communications Enginnering
Scopus Publications
Scholar Citations
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Scopus Publications
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.
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.
Saja Alaa Gheni and Dhirgham Kamal Naji
The Electromagnetics Academy
Reham M. Yaseen, Dhirgham Kamal Naji, and Amina M. Shakir
Progress In Electromagnetics Research B The Electromagnetics Academy
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.
Haneen Sobhi Aziz and Dhirgham Kamal Naji
Progress In Electromagnetics Research M EMW Publishing
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.
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).
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.
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.