Papers by Khalil Sayidmarie
Progress In Electromagnetics Research M
Focused arrays are attracting increased interest because of their wide range of applications. Foc... more Focused arrays are attracting increased interest because of their wide range of applications. Focusing the antenna's radiation in the near field requires proper phase distribution of the array elements that must be fed through many phase shifters. This work presents a design idea for a focused circular array antenna, whose focal distance can be varied by only a single variable phase shifter. The idea is implemented on a dual ring circular array having a six-wavelength diameter and focused at five wavelengths by using a single fixed phase shifter. Theoretical analysis and computer simulations of a sample design using MATLAB and CST Microwave Studio show that a phase change of 0.9π leads to a four wavelength change in the focal distance. A formula for the estimation of the depth of field DOF is derived. The proposed array offers a simple method to vary the focal length continuously by a single variable phase shifter. This idea can be utilized in hyperthermia, RFID, and imaging applications, where the position of the focal spot needs to be moved along the normal to the array.
AL Rafdain Engineering Journal, Dec 28, 2005
Tunable Plasmonic Resonances Below Schottky Diode Band-gap Based on Elliptical Nanoantennas
Nanoantennas are suitable components for detection of optical radiation at energies below the ban... more Nanoantennas are suitable components for detection of optical radiation at energies below the bandgap energy of the semiconductor and higher than Schottky barrier of metal/semiconductor interface in photodetectors. Elliptical nanodisk antennas (ENAs) on a Gallium Arsenide (GaAs) substrate are studied to tune the optical response across the near-infrared band. The resonance wavelength, normal field enhancement, and bandwidth of plasmonic resonance are tailored by controlling the size and elliptical aspect ratio. The results are compared with circular nanodisk antennas (CNAs) and ring nanoparticle antennas (RNAs). Silver and gold metal types for nanoantennas are also studied for electric field enhancement, where the Drude model of metals are considered. The surfaces plasmon is proven by comparing with the perfect electric conductor of silver and gold nanoantennas. The obtained results prove that the designed nanoantennas can be used to enhance the operation of photodetectors and solar cells.
Sine-to-Square Waveform Conversion Technique
IETE Technical Review, Oct 1, 1986
A new circuit configuration that converts a sinusoidal waveform into a square one is proposed. Th... more A new circuit configuration that converts a sinusoidal waveform into a square one is proposed. The circuit is basically a comparator whose threshold level is proportional to the amplitude of the input signal. The effect of variation in the level of the input signal is thus eliminated and a constant duty cycle output is obtained.
A microstrip-fed pentagon patch monopole antenna for ultra wideband applications
This paper presents a novel design of microstrip-fed pentagon patch monopole antenna for ultra wi... more This paper presents a novel design of microstrip-fed pentagon patch monopole antenna for ultra wideband (UWB) applications. This antenna consists of a pentagon patch with suitable dimensions on the upper side of a dielectric substrate; a 50-Ω microstrip feed line and a slotted ground plane. Numerical analysis for the antenna dimensional parameters using CST Microwave Studio is performed and presented. The radiation characteristics of the proposed antenna such as radiation pattern, gain, impedance bandwidth are investigated. The proposed antenna provides a compact size, an UWB frequency range of 3.6-14.7 6GHz (121.6% relative bandwidth), and a maximum gain of 4dBi. These features including the good radiation characteristics of the antenna satisfy the requirements of UWB systems.
Improvement of array radiation pattern by element position perturbation
Amplitude-only beam scanning in linear antenna arrays
... A 3-element array is studied first, then the idea is extended to a 7-element array. Simulatio... more ... A 3-element array is studied first, then the idea is extended to a 7-element array. Simulation results show appreciable scan angles with minor variation in the mainbeam level. Some degradation in the array pattern is noticed at large scan angles. Index Terms. INSPEC: ...
IEEE Transactions on Antennas and Propagation, Dec 1, 2019
A dual-function slot antenna at microwave and millimetre-wave (mm-wave) band is proposed. The des... more A dual-function slot antenna at microwave and millimetre-wave (mm-wave) band is proposed. The design consists of a slot printed on the edge of the structure ground plane. A short-circuited varactor diode is used to achieve frequency tunability from 2.05 to 2.7 GHz (4G, WLAN) with a maximum realized gain of 4.5 dBi. For mm-wave band, the slot works as a connected slot antenna array (CSAA) by using 8 periodic feeders with a wide bandwidth of 23-29 GHz (5G) and a maximum realized gain of 12.5 dBi. To enhance functionality, two slots are arranged orthogonally for multiple-input multiple-output (MIMO) application. The whole structure is implemented using Rogers 5880 substrate with a board size of 70 × 60 × 0.381 mm 3. The envelope correlation coefficient (ECC) and isolation are calculated, showing satisfactory MIMO characteristics. The minimum ECC value is 0.01, while the isolation is more than 20 dB among different feeding ports. Due to the integration of 4G and 5G operation into a single narrow slot, the proposed antenna system is compact, simple and planar in structure, and thus, attractive for future mobile handheld devices.
A Circular Dipole Nanoantenna with Improved Performance
IOP conference series, May 1, 2021
A two-sided frequency selective surface (FSS) is proposed to shield two bands of the mobile frequ... more A two-sided frequency selective surface (FSS) is proposed to shield two bands of the mobile frequencies (EGSM-900 and DCS-1800). The FSS consists of an array of square concentric-rings cells printed on both sides of the substrate to offer better shielding of the two mobile frequencies. The CST Microwave suit is used for the simulations. The equivalent circuit model for the two-sided FSS is analysed and the transmission frequency in terms of the two stop frequencies is estimated. The obtained shielding is better than 40 dB across the two bands. The proposed FSS can be used to reduce mobile radiation or to isolate halls from nearby mobile base stations. The bandwidth of the FSS cell can be increased by using ring pairs of unequal sizes on the two sides of the substrate.
Applied Computational Electromagnetics Society Journal, Jan 2, 2023
This paper proposes a fractal monopole antenna based on a sectoral-shaped patch. To improve the g... more This paper proposes a fractal monopole antenna based on a sectoral-shaped patch. To improve the gain of the proposed antenna over a larger bandwidth, the matching was enhanced by attaching two rectangular stubs to the feeding line. The antenna, which is built on an FR4 epoxy substrate with ε r =4.3 and a loss tangent of 0.018 has a compact size of 28 mm×31 mm×1.6 mm. The antenna covers the UWB range and extends to about the 22 GHz frequency, as well as offers omnidirectional radiation patterns. The optimized configuration was fabricated and tested. The impedance bandwidth of the proposed antenna is about 155% with a reflection coefficient better than −10 dB and has a maximum gain of nearly 4 dBi with a relatively stable omnidirectional radiation pattern.
A simple self-interference cancellation technique for full duplex communication
Recently, a considerable attention has been paid for full duplex communication. Full duplex allow... more Recently, a considerable attention has been paid for full duplex communication. Full duplex allows transmitting and receiving at same frequency simultaneously. As a result, the spectral efficiency can be increased two times by utilizing this type of communication. Nevertheless, the substantial issue of applying full duplex communication is the self-interference signal. This paper presents a new method of antenna cancellation with symmetric antenna placements to cancel the self-interference signal. Three monopoles antennas are modelled by using Computer Simulation Technology (CST) program; one as a receive antenna, while others as transmit antennas. The cancellation of the method is calculated by utilizing Matlab code. Moreover, many factors that could degrade the system performance are investigated. Results illustrate that this technique provides higher than 50 dB cancellation in a typical situation. However, results show a decline in the efficiency of the technique when there is an inaccuracy of placing the antennas, or amplitude mismatch between two transmitted signals. The obtained simulation results are verified by testing the technique practically. The results show that the practical prototype can provide more than 40dB cancellation over a wide band frequency.
Progress In Electromagnetics Research C
A concentric circular array consisting of two rings is proposed to focus the radiated field at a ... more A concentric circular array consisting of two rings is proposed to focus the radiated field at a point in the near-field zone. In the proposed two-ring array, the radius of the outer ring was chosen so that the radiated fields from all elements on the two rings add constructively at the focal point, thus no phase shifter is needed in this design. The N elements of the inner ring are uniformly excited in unity amplitude and zero phase, while the M elements on the outer ring are excited uniformly in phase, and given uniform magnitude excitations of N/M. Therefore, two deep nulls are achieved on both sides of the focus to enhance the focal width. The focusing properties are investigated by exploring the array parameters, such as variation of the focused field along the normal to the array, field distribution on the focal plane, and depth of field (size of the focal spot). Computer simulations using the MATLAB environment are performed by point source radiators. For verification, the array was simulated using the CST microwave studio, and the obtained results showed good agreement. The array is useful for hyperthermia and imaging applications.
To effectively detect the targets in any direction, the radar antenna should be in the form of a ... more To effectively detect the targets in any direction, the radar antenna should be in the form of a planar array that has a large number of elements. In such a case, partially adaptive planar arrays, where only a few elements are adaptive, are often necessary to reduce the system’s cost and increase the speed of the tracking capability. In this paper, only the perimeter elements of the planar arrays are selected to be adaptive while maintaining the good radiation characteristics as that of the fully adaptive planar arrays with, of course, lower cost and fewer RF components. Unlike a previous method that consists of optimizing only two edge elements in the linear arrays, the proposed planar array with optimized perimeter elements is quite sufficient to provide enough degrees of freedom to control the sidelobe pattern and place the desired nulls efficiently. Simulation results show that the required radiation pattern with asymmetric sidelobes and desired nulls can be obtained by optimizi...
International Journal of Electrical and Computer Engineering (IJECE), 2019
In this paper, a new approach to the design of an UWB monopole antenna with dual band-notched cha... more In this paper, a new approach to the design of an UWB monopole antenna with dual band-notched characteristics is presented. The antenna has the form of an elliptical monopole over a ground plane having an elliptical slot to achieve the UWB. The dual-band notch function is created by inserting a U-shaped and a C-shaped slots on the radiating patch, thus no extra size is needed. The proposed antenna shows a good omnidirectional radiation pattern across the band from 3.2 to more than 14 GHz. The dual band-rejection is for 4.88-5.79GHz centered at 5.4GHz and 7.21-8.46 GHz centered at 7.8 GHz. The antenna prototype using the FR-4 substrate with εr=4.3 has a compact size of 25mm×25 mm ×1.45mm. The fabricated prototype showed experimental results comparable to those obtained from the simulations.
Iraqi Journal for Electrical And Electronic Engineering, 2014
In this paper, a compact two-element cylindrical dielectric resonator antenna (CDRA) array with c... more In this paper, a compact two-element cylindrical dielectric resonator antenna (CDRA) array with corporate feeding is proposed for X-band applications. The dielectric resonator antenna (DRA) array is excited by a microstrip feeder using an efficient aperture-coupled method. The designed array antenna is analyzed using a CST microwave studio. The fabricated sample of the proposed CDRA antenna array showed bandwidth extending from 10.42GHz to 12.84GHz (20.8%). The achieved array gain has a maximum of 9.29dB i at frequency of 10.7GHz. This is about 2.06dB i enhancement of the gain in comparison with a single pellet CDRA. The size of the whole antenna structure is about 5050mm 2 .
IEEE Access, 2019
A new compact Cylindrical Dielectric Resonator Antenna (CDRA) with a defected ground for ultra-wi... more A new compact Cylindrical Dielectric Resonator Antenna (CDRA) with a defected ground for ultra-wideband applications is presented. The structure is based on two cylindrical dielectric resonators asymmetrically located with respect to the center of an offset rectangular coupling aperture, with consideration of three and four Dielectric Resonators (DR). The resonant modes generated by the defected ground are studied and investigated. A parametric optimization study of the antenna design has been carried out to determine the optimal dimensions of the defected ground plane, resulting in an impedance bandwidth of over 133% that covers the frequency band from 3.6 GHz to 18.0 GHz. A power gain of about 7.9 dBi has been achieved. Design details and measured and simulated results are presented and discussed. INDEX TERMS Cylindrical dielectric resonators antenna, ultra-wideband, defected ground structure.
Progress In Electromagnetics Research M, 2023
Focused arrays are attracting increased interest because of their wide range of applications. Foc... more Focused arrays are attracting increased interest because of their wide range of applications. Focusing the antenna's radiation in the near field requires proper phase distribution of the array elements that must be fed through many phase shifters. This work presents a design idea for a focused circular array antenna, whose focal distance can be varied by only a single variable phase shifter. The idea is implemented on a dual ring circular array having a six-wavelength diameter and focused at five wavelengths by using a single fixed phase shifter. Theoretical analysis and computer simulations of a sample design using MATLAB and CST Microwave Studio show that a phase change of 0.9π leads to a four wavelength change in the focal distance. A formula for the estimation of the depth of field DOF is derived. The proposed array offers a simple method to vary the focal length continuously by a single variable phase shifter. This idea can be utilized in hyperthermia, RFID, and imaging applications, where the position of the focal spot needs to be moved along the normal to the array.
The frequency selective surfaces (FSS) are drawn great interests for their wide range of applicat... more The frequency selective surfaces (FSS) are drawn great interests for their wide range of applications. In this paper, a simple and compact shape for the FSS is proposed, in which the resonant element is a conducting strip that is folded into the shape of the letter-U and placed on a dielectric sheet. The folding of the strip reduces the element length to ½ of the effective wavelength, which is a considerable size reduction in comparison with other shapes. An example of the FSS was designed to reject the WiMAX frequency of 3.5 GHz and was investigated using the CST software package. The transfer characteristics were shown for the two cases of the vertical and horizontal polarizations of the incident electric field. The obtained rejection at the stopband was about 35dB. The obtained results are explained by considering the surface current distribution and electric field at the strip as well as the metamaterial behavior across the reject band. This approach gives better insight to understand the frequency selective property of the FSS.
Microwave Backscattering from a Metallic Cylinder and the Effect of a Concealing Dielectric Plate
IETE Journal of Research, 1985
The field backscattered by a metallic cylinder due to an incident wave of arbitrary linear polari... more The field backscattered by a metallic cylinder due to an incident wave of arbitrary linear polarization is investigated. It is shown that maximum depolarization occurs when the cylinder is at 45° to the incident polarization. The influence of shielding the cylinder by various dielectric plates is demonstrated experimentally.
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Papers by Khalil Sayidmarie