Moataza Hendi - Academia.edu (original) (raw)

Papers by Moataza Hendi

Microwave and Optical Technology Letters, 2001

Figure 9 Simulation result for the varactor-tuned TLR᎐HSMR BPF be 5.68 dB, and can be improved by... more Figure 9 Simulation result for the varactor-tuned TLR᎐HSMR BPF be 5.68 dB, and can be improved by a smaller gap for the integrated varactor diode. IV. CONCLUSIONS A new microstrip-ring bandpass filter with a harmonicsuppression characteristic has been suggested in this paper. This filter, with a 100 MHz bandwidth at 5.775 GHz, has been designed, fabricated, and successfully demonstrated. The new microstrip-ring bandpass filters are attractive for high-performance filters with harmonic suppression and good flatness within the passband. Also, the varactor-tuned microstrip-ring bandpass filter was designed and demonstrated with a highharmonic-suppression ratio and a tuning bandwidth of 450 MHz. These planar structures can be applied to MMIC, RFIC, and RF-photonic devices. These types of circuits can be easily fabricated with slot-line and CPW structures. If microstripring bandpass filters with harmonic suppression are fabri-Ž. cated on an HTS high-temperature superconductor , the insertion and return loss characteristics with narrow bandwidth are expected to be enhanced.

Journal of Manufacturing Science and Engineering-transactions of The Asme, Nov 20, 2009

Extensive work had been conducted on spot-welding due to its rapidly increasing industrial import... more Extensive work had been conducted on spot-welding due to its rapidly increasing industrial importance. The resistance spot-welding involves complicated phenomena, as several effects are found in the process, e.g., temperature, surface roughness, pressure, and eddy current effects. Most of the work exerted for analyzing the spot-welding process neglect the effect of the eddy current generated during the flow of the huge welding main current through the assembly of electrodes and work sheets. This work presents an analytical method to investigate the generation of eddy current and to determine the total effective welding current in spot-welding. The current distribution on the work sheet when it is fed by a conducting electrode is also investigated. The obtained current formula is based on electromagnetic principles, where a very strong magnetic field is generated in the core of the electrodes as well as in the materials of work sheets due to the flow of very high amperage. The final resultant effective current is the superposition of the electrode welding current and the induced eddy current in the electrode and work piece assembly. The results offer a viable mathematical model, which can be applied for a precise prediction of the effective value of welding current in spot-welding processes, if applied in a comprehensive model including all involved effects.

Journal of Circuits, Systems, and Computers, Dec 1, 2010

Journal of Electrical Systems and Information Technology, Sep 1, 2014

The process of transferring the natural gas from the gas well to the gas separation plant encount... more The process of transferring the natural gas from the gas well to the gas separation plant encountered some delay time depending on the distance between this well and the factory, the cross section of the transport line, the geometry of this transport line, the well pressure and others. To control the factory inlet pressure by controlling the choke valve existing at the well head, the delay time makes the traditional control systems to fail. In this framework we aim to solve this problem by presenting a novel controller design and delay modeling technique. The presented technique is compared to the previous control system design and delay approximation techniques.

Sadhana-academy Proceedings in Engineering Sciences, Apr 6, 2019

The Ka band has found applications in satellite, and radar communications. It is also expected th... more The Ka band has found applications in satellite, and radar communications. It is also expected that this band will be utilized for 5G applications. This paper presents single-and double-beam microstrip reflectarrays with single layer and compact size for Ka band communications at 28 GHz. Three different unit cells are investigated in this paper. Single-and double-beam reflectarrays are investigated. The reflectarrays are designed at 28 GHz with a physical size of 10k 9 10k. A pyramidal horn antenna is used for the feeding purpose. The focal-length-to-diameter (F/D) ratio is equal to one. Two different scenarios for single-beam reflectarrays are presented: one with a broadside direction and the other with a 10°tilt angle. The simulation results show that for the broadside single-beam scenario, it is possible to achieve a gain up to 28.5 dB, and a 1-dB gain-bandwidth up to 30.7%. On the other hand, the presented reflectarray for the single-beam design at 10°tilt angle gives a gain of about 26.4 dB, a side lobe level (SLL) of about-15.6 dB, and a 19.3% gain-bandwidth. For the double-beam reflectarray, four different designs at different angles of 5°, 10°, 15°, and 20°have been simulated and compared. Moreover, the simulation results on the double-beam reflectarray show that the double-beam design at 10°is better from the gain and SLL perspectives. Two prototypes for broadside single-beam reflectarrays have been fabricated and measured. The measurement results show a good match with the simulation results. Gain flatness is guaranteed for both the simulated and measured results over the band of interest.

This paper presents a compact dual-feed patch antenna capable of achieving dual-polarized radiati... more This paper presents a compact dual-feed patch antenna capable of achieving dual-polarized radiation suitable for applications demanding frequency reuse or polarization diversity. Circular polarization is obtained by feeding the antenna with 90° phase shift between its two ports using Wilkinson power divider having λ/4 difference between its outputs. This proposed circularly polarized antenna is suitable for GPS applications.

Progress In Electromagnetics Research M

Imperial journal of interdisciplinary research, 2017

: UWB microstrip antennas with improved performance, radiation pattern uniformity, and directivit... more : UWB microstrip antennas with improved performance, radiation pattern uniformity, and directivity enhancement is proposed in this communication. In this article, a simple UWB microstrip antenna is demonstrated; we show that a metal ground plane can serve as a cooperative radiator to achieve broadening impedance bandwidth, directivity enhancement, and radiation pattern uniformity over a broadband frequency. It will be demonstrated that a required UWB starting frequency can be achieved by tuning the mutual coupling between the circular patch and metal ground plane. Proposed antenna is suitable for small / large wireless devices applications and ultra-high frequency applications as see through wall and concert application.

Microwave and Optical Technology Letters

International Journal of RF and Microwave Computer-Aided Engineering

International Journal of Speech Technology, 2018

This paper is concerned with reflectarray antenna design with multiple unit cells in order to enh... more This paper is concerned with reflectarray antenna design with multiple unit cells in order to enhance the gain at the design frequency, while keeping an acceptable bandwidth to work for 5-G mobile base station applications. The design is based on five unit cells. The design begins with an investigation of the phase responses of all unit cells. It is required to choose a unit cell that can span 360° with linear characteristics. Unfortunately, none of the unit cells has perfectly linear phase characteristics. Each of them has a limited linear phase region. The proposed reflectarray design method selects the most linear region from each phase curve for selecting the appropriate unit cell with the appropriate size for each required phase using a phase gradient approach. With this approach, piece-wise linear phase characteristics are adopted for the design of the reflectarray to enhance the gain at the design frequency.

Iranian Journal of Science and Technology, Transactions of Electrical Engineering, 2019

This paper presents two designs of reflectarrays with two different unit cells: a novel broadband... more This paper presents two designs of reflectarrays with two different unit cells: a novel broadband microstrip unit cell and a 3D all-metal unit cell. The microstrip unit cell consists of two concentric octagonal rings plus an octagonal patch with an empty cross inside. On the other hand, the all-metal unit cell is composed of a pure copper cuboid. These reflectarrays are designed to work around 28 GHz for suitable 5G operation. A pyramidal horn antenna is used for the feeding purpose. The F/D ratio is equal to one. The reflectarray is 107 mm × 107 mm in dimensions. The simulation results show that the reflectarray based on the microstrip unit cell achieves a 1-dB gain-bandwidth of about 31.2% with a gain equal to 27.2 dB at 28 GHz. On the other hand, the all-metal reflectarray achieves a 1-dB gain-bandwidth of 14.5% and a gain equal to 28.5 dB at 28 GHz. From the obtained results, it is clear that the microstrip reflectarray is superior from the gain-bandwidth perspective, while the allmetal reflectarray is superior from the gain perspective. The microstrip reflectarray has been fabricated, and its performance has been measured. A good agreement between the simulation and measurement results has been achieved.

International Journal of Microwave and Wireless Technologies, 2017

This paper presents a new optically controlled reconfigurable ultra-wideband antenna using reconf... more This paper presents a new optically controlled reconfigurable ultra-wideband antenna using reconfigurable optical router with photonic crystal substrate. The proposed antenna has three optical switches. The optical switches are made by placing silicon wafers over three slots etched on the resonator. The coplanar fed microstrip antenna can work at eight modes using optically controlled switches. This design proposes triple narrow notched bands at center frequencies 3.5 GHz “WiMAX”, 5.5 GHz “WLAN” and 8.4 GHz “X-band satellite communication”. The proposed antenna satisfies the voltage standing wave ratio requirement of <2 in the frequency band between 2.6 and 11.8 GHz except for the three rejected bands. According to the incident light, the physical properties of these switches can be changed from an insulator state (OFF state) to a near-conducting state (ON state). The incident light is coupled to the optical switches using a reconfigurable optical router. The proposed antenna pro...

Journal of Circuits, Systems and Computers, 2010

In this paper, a novel neural technique is proposed for FET small-signal modeling. This technique... more In this paper, a novel neural technique is proposed for FET small-signal modeling. This technique is based on the discrete cosine transform (DCT) and the Mel-frequency cepstral coefficients (MFCCs). The input data to traditional neural systems for FET small-signal modeling are the scattering parameters and the corresponding frequencies in a certain band, and the outputs are the circuit elements. In the proposed technique, the input data are considered random, and the MFCCs are calculated from these inputs and their DCT. The MFCCs are used to give a few features from the input random data sequence to be used for the training of the neural networks. The objective of using MFCCs is to characterize the random input sequence with features that are robust against measurement errors. The MFCCs extracted from the DCT of the inputs increase the robustness against measurement errors. There are two benefits that can be achieved using the proposed technique; a reduction in the number of neural ...

Applied Optics, 1995

A detailed analysis of a microwave reflection pattern that is due to periodically photoexcited la... more A detailed analysis of a microwave reflection pattern that is due to periodically photoexcited layers of semiconductor material in a waveguide is presented. Different photoconductivity profiles that are due to different excitation conditions with different materials are tested. The diffusion of carriers in the direction of propagation can strongly affect the passband-filtering responses, especially the efficiency and the bandwidth. These configurations can be used as light-induced tunable filters and as a variable matching section between different levels of impedances.

Applied Optics, 1997

A time domain analysis of an optically controlled digital microstrip switch for microwave integra... more A time domain analysis of an optically controlled digital microstrip switch for microwave integrated circuits on Si substrates is studied. A new model for high-frequency pulse propagation on a microstrip optical switch for different optical parameters is presented. A frequency-dependent macromodel for a microstrip line with a gap is implemented in Spice 3, taking into consideration high-frequency pulse dispersion, conductor and dielectric losses, metallization thickness, gap length, and different optical parameters such as optical energy, surface recombination velocities, and diffusion of generated carriers. In addition, the developed model has been used to optimize the switching frequency, gap length, level of optical power, and suitable substrate material parameters.

Microwave and Optical Technology Letters, 2011

The antenna structure is fabricated and tested. The photograph of fabricated antenna is shown in ... more The antenna structure is fabricated and tested. The photograph of fabricated antenna is shown in Figure 7. The measured return loss plot of proposed antenna is shown in Figure 2. The measured results are in agreement with simulated results. The variation in measured return loss can be attributed to inaccuracy in dimensions of radiating patch and ground plane as metal-plated antenna has to be mechanically fabricated, impedance mismatch due to feed tip of SMA connector and increase in ground plane dimensions due to SMA connector. 4. CONCLUSIONS A novel metal-plated tuning fork-shaped monopole antenna is proposed. The proposed antenna offers less than À15 dB cross-polarization, more than 88% antenna efficiency, and its gain varies from 1.7 to 5 dB over the UWB range. The gain difference along two transverse axis is <3 dB for frequencies less than 9.1 GHz and it increases to 5.5 dB at 10.6 GHz. Omnidirectional radiation bandwidth is increased by using rectangular strips on both sides of a semiannular ring monopole antenna and a thin foam dielectric between radiating structure and ground. The radiation patterns are nearly omnidirectional over UWB frequency range. One drawback of this antenna is mechanical fabrication, which may cause inaccuracy in dimensions and performance degradation.

2010 IEEE Antennas and Propagation Society International Symposium, 2010