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Search Results: 1 - 10 of 556498 matches for " Dalia Mohammed Nasha Elsheakh;Magdy F. Iskander;Esmat Abdel-Fattah Abdallah;Hala A. Elsadek;Hadia Elhenawy "
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Microstrip Array Antenna with New 2D-Electromagnetic Band Gap Structure Shapes to Reduce Harmonics and Mutual Coupling
Dalia Mohammed Nasha Elsheakh;Magdy F. Iskander;Esmat Abdel-Fattah Abdallah;Hala A. Elsadek;Hadia Elhenawy
PIER C , 2010, DOI: 10.2528/PIERC09112008
Abstract: This paper presents microstrip array antenna integrated with novel shapes of 2D-electromagnetic band-gap structure (2D-EBG). Three different shapes of 2D EBG are used for harmonic suppression, optimizing the current distribution on the patches and decreasing the mutual coupling between array elements. As a result, the performance of the antenna array is improved. The three novel shapes of 2D-EBG presented are star, H shaped and I shaped slots. Simulated and measured results verify the improved performance of the array antenna compared to the antenna without EBG as well as antenna array with conventional EBG shapes. The harmonic suppression and reflection coefficients are improved by about 18 dB. Minimum mutual coupling is less than -20 dB, and the antenna size is reduced by 15% compared to the original size.
Ultra-Wideband and Miniaturization of the Conventional Inset Feed Microstrip Patch with Modified Ground Plane for Wireless Applications
Dalia Mohammed Nasha Elsheakh;Hala A. Elsadek;Esmat Abdel-Fattah Abdallah;Magdy F. Iskander;Hadia Elhenawy
PIER Letters , 2009, DOI: 10.2528/PIERL09061104
Abstract: In this paper, ultra-wideband and miniaturization, technique for the microstrip monopole patch antenna (MMPA) in wireless applications is presented. Ultra-wideband was achieved by using Printed modified ground plane on a dielectric substrate with 50- microstrip feed line. This technique allows the bandwidth of the MMPA to be ultra-wideband with satisfactory radiation properties and reduce the antenna size. The proposed antenna with modified ground plane provides an mpedance bandwidth (S < -10 dB) more than 5.5 GHz corresponding to 116% of fundamental resonant frequency with reduction in antenna size by 20% from original size. For further improvement in antenna characteristics, electromagnetic band-gap (EBG) structure is used. The surface wave was suppressed so the antenna bandwidth was increased to be 3--11 GHz corresponding to 170%, and the antenna size was reduced 43% of its original size. Two types of EBG are used. Holes are drilled around the patch, and embedded circular patches of the electromagnetic band-gap structure with suitable dimension are used. Details of the proposed antenna design have been described, and the typical experimental results are presented and discussed. Commercial software high frequency structure simulator (HFSS) version 11 was used for the antenna design.
Reconfigurable Single and Multiband Inset Feed Microstrip Patch Antenna for Wireless Communication Devices
Dalia Mohammed Nasha Elsheakh;Hala A. Elsadek;Esmat Abdel-Fattah Abdallah;Magdy F. Iskander;Hadia M. El-Henawy
PIER C , 2010, DOI: 10.2528/PIERC10011503
Abstract: Two novel designs for compact reconfigurable antennas are introduced for wireless communication devices. These designs solve the steering frequency problem by tracking the desired resonance frequency or by generating various operating frequency bands to be selected electronically. In the first design, the length of the rectangular defected ground structure (RDGS) is electrically adjusted to change the resonant frequency of the MPA. While in the second design different turns of spiral AMC ground plane generate frequency bands, or modes, that are selected/optimized to serve different communication systems simultaneously. These systems may include various combinations of bluetooth, S-band and wireless local-area network (WLAN). These designs have several advantages as the total antenna volume can be reused, and therefore the overall antenna will be compact, although, the radiation of the MPA is kept fixed without any degradation. The designs are verified through both numerical simulations and measurement of a fabricated prototype. The results confirm good performance of the single and multiband reconfigurable antenna designs.
Ultra-Wide Bandwidth Microstrip Monopole Antenna by Using Electromagnetic Band-Gap Structures
Dalia Mohammed Nasha Elsheakh;Hala A. Elsadek;Esmat Abdel-Fattah Abdallah;Hadia M. El-Henawy;Magdy F. Iskander
PIER Letters , 2011, DOI: 10.2528/PIERL11020805
Abstract: A novel compact design for ultra-wide bandwidth (UWB) planar monopole antenna is presented in this paper. The basis for achieving the UWB operation is through using semicircular microstrip monopole antenna with modified ground plane in the form of semi circular umbrella like shape. This shape produces bandwidth ranging from 3 to 35 GHz with discontinuities from 7 GHz to 10 GHz, from 12.5 GHz to 17.5 GHz and from 22 GHz to 40 GHz. The antenna size is reduced by 27% relative to the size of conventional rectangular monopole patch antenna. Metamaterial structures are used for further antenna performance improvement. Two types of metamaterial namely EBG and DGS are studied. First, embedding metallo EBG (EMEBG) is used to eliminate ripples in the operating band and also further reducing the antenna size by more than 30% as compared to the proposed patch. The antenna design provides an impedance bandwidth of more than 33 GHz. Second, four arms spiral defected ground structure (SDGS) is used as a ground plane with four arms to further improve the antenna performance. The SAMC reduced the antenna size by more than 48% as compared to the proposed antenna patch, increased bandwidth, and decreased the cross polarization effect. Finally, embedded EBG together with SDGS ground plane are studied to take advantages of both techniques.
Investigated New Embedded Shapes of Electromagnetic Bandgap Structures and via Effect for Improved Microstrip Patch Antenna Performance
Dalia Mohammed Nasha Elsheakh;Hala A. Elsadek;Esmat Abdel-Fattah Abdallah;Magdy F. Iskander;Hadia M. El-Henawy
PIER B , 2010, DOI: 10.2528/PIERB09122004
Abstract: Three novel shapes of mushroom-like electromagnetic band-gap (EBG) structures are presented in this paper. The three shapes are based on rectangular metal strip with different combinations. The performances of the three-shape structures are studied by using both incident plane wave method and transmission coefficient approach. The effect of height and via location are also studied to achieve multi or wide band gap. These shapes are embedded in microstrip patch antenna substrate. The performance of the MPA is improved as increasing the antenna gain by 5 dBi, decreasing the surface current so improving the antenna radiation pattern as well as reducing the antenna size by more than 70% compared to the original size. The new shapes of EBG structure are integrated with MPA as a ground plane, where the conducting ground plane is replaced by a high impedance surface EBG layer. Parametric studies are conducted to maximize their impedance bandwidth and gain. It is found that the antenna bandwidth increased by about four times than original band and its gain is similarly increased. Sample of these antennas are fabricated and tested, to verify the designs.
Design of Low SAR Planar Monopole Antenna for Mobile Wireless Communication Applications
Dalia Mohammed Nasha Elsheakh;Esmat Abdel-Fattah Abdallah
PIER M , 2013, DOI: 10.2528/PIERM12121504
Abstract: Simple internal multiband monopole antenna with low SAR for most of wireless mobile communication applications is presented in this paper. The proposed antenna is a unequal arms monopole antenna with a meander strip in the other substrate side. The antenna has a simple structure and is sufficiently small in size to be easily fit on the housing of mobile or USB dongle with size 18 × 15 × 0.8 mm. The antenna is designed to operate at multi-bands to occupy most of allocated wireless communication devices by using high frequency structure simulator ver. 13 (HFSS). The proposed antenna has acceptable gain and efficiency while providing broadside radiation pattern that covers the horizontal plane. The antenna design and experimental results are in agreement. Moreover, the specific absorption rate (SAR) in the human head is investigated by CST 2012 Microwave Studio Hugo Voxel Model.
A Reconfigurable UWB Bandpass Filters with Embedded Multi-Mode Resonators  [PDF]
Eman Gamal Ouf, Ashraf S. Mohra, Esmat Abdel-Fattah Abdallah, Hadia Elhennawy
Open Journal of Antennas and Propagation (OJAPr) , 2018, DOI: 10.4236/ojapr.2018.63005
The two proposed filters described here satisfy the Federal Communications Commission Ultra-wideband (FCC-UWB) specifications and also control the center frequency and bandwidth of the filters passband. These filters consist of two distinguishing parts, Electromagnetic bandgap (EBG)-embedded multiple- mode resonator (MMR) and interdigital coupled lines to realize high performance in the operation band with a compact size of 14.0 mm × 10.1 mm. The main advantage of the two proposed filters is that three different bands are tuned. The 1st tuned band is from 3.5 GHz to 11.4 GHz for the first filter and from 3.1 GHz to 11.6 GHz for the second proposed filter, respectively. The 2nd tuned band is from 3.5 GHz to 7.5 GHz for the first filter and from 3.1 GHz to 7.8 GHz for the second proposed filter, respectively. While the 3rd tuned band of the first proposed filter is from 3.5 GHz to 5.9 GHz and from 3.1 GHz to 5.8 GHz for the second proposed filter. The bandwidth of the filters can be changed by increasing the length of the outer open circuited stubs which are controlled by using switching matrix equipment (mini circuit, replacement of PIN diodes). To validate the design theory, a reconfigurable UWB bandpass filters (BPFs) with EBG Embedded MMR are designed, fabricated and measured. Good agreement is found between simulated and measured results.
Analysis and Design of Universal Compact Flexible UHF RFID Tag Antenna
Tamer Gaber Abo-Elnaga;Esmat Abdel-Fattah Abdallah;Hadia M. El-Henawy
PIER B , 2011, DOI: 10.2528/PIERB11091102
Abstract: The main goal of this paper is to present a design procedure for a flexible compact universal UHF RFID tag antenna suitable for worldwide UHF RFID applications. Systematic design procedure is introduced through the derivation of dipole input impedance general relation using induced EMF method considering wire radius effect. T-matched chart is used to match the tag input impedance with the chip input impedance and finally develop a flow chart to summarize the design procedure. The proposed antenna compactness trend is achieved through applying meandering and Franklin shape to conventional printed dipole antenna. Flexibility trend is achieved through using liquid crystal polymer LCP material as antenna substrate. The proposed antenna covers the frequency band 865 MHz to 1078 MHz and occupies an area of 1306.6 mm. The computed radar cross section RCS and conjugate match factor CMF insure that the proposed antenna structure is easily detectable and achieves acceptable matching level. Power reflection coefficient PRC is computed, measured and good agreement is obtained. Other antenna parameters such as radiation efficiency, gain and radiation pattern are also calculated. The proposed antenna is cheap, flexible and suitable for UHF RFID universal application.
Microstrip Antennas: Future Trends and New Applications
Hala A. Elsadek,Esmat A. Abdallah,Dalia M. Elsheakh,Heba Badr El-Din El-Shaarawy
International Journal of Antennas and Propagation , 2013, DOI: 10.1155/2013/890764
Production of Bacillus licheniformis ATCC 21415 Alkaline Protease in Batch, Repeated Batch and Continuous Culture
Ahmed, S. A.,Abdel-Fattah, A. F.
Malaysian Journal of Microbiology , 2010,
Abstract: Bacillus licheniformis ATCC 21415 cells were immobilized on different carriers using different methods of immobilization including physical adsorption, covalent binding, ionic binding and entrapment. The immobilized cells were prepared by covalent binding on wool (as a new carrier) through 1% glutaraldehyde had the highest enzyme activity (9.0 U/mL) with the highest specific productivity (6.17 U/g wet cells/h). Alkaline protease production and the stability of biocatalyst were investigated in both free and immobilized cells. The results showed that the immobilized cells were more efficient for enzyme production by repeated batch fermentation (5 cycles, 480 h) with 57% residual activity whereas the free cells retained 35% after 2 cycles. In continuous production the highest enzyme activity (9.9 U/mL) was obtained at a dilution rate of 0.1/h while the highest enzyme yield (763.6 U/h) and the highest reactor productivity (3.32 U/mL/h) were attained at a dilution rate of 0.4/h. Packed-bed bioreactor was a successful method for continuous production of alkaline protease for a long time (168 h) with 53% relative activity. The bioreactor affected the highest specific productivity (118.2 U/g wet cells/h) which was 12-24 times higher than other systems of enzyme production.
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