Ahmed Kishk

Concordia University Montreal · Department of Electrical and Computer Engineering

An infinitesimal dipole model (IDM) for an antenna including mutual coupling is used to model the radiation patterns of aperiodic arrays. Each radiating element is modelled by a set of infinitesimal dipoles. The mutual coupling between the elements is calculated and the far field radiation pattern of the antenna is computed in a fast and efficient...

Low-profile directional ultra-wideband (UWB) antennas are strongly demanded in many UWB applications. However, few such UWB antennas have been reported. To meet the demands, an original novel low-profile directional UWB antenna-the self-grounded Bow-Tie is developed and presented here. This new UWB antenna has a compact and simple geometry, and ult...

Some focusing properties of Fresnel zone plate (FZP) lens antennas in the near-field region are presented at the ka-band. Simulated and measured results of the FZP antenna show displacement of the maximum intensity of the electric field along the axial direction from the focal point toward the antenna aperture. This displacement increases as the an...

An H-shape ultrawideband (UWB) dielectric resonator (DR) mounted on a vertical ground plane edge with broadside radiation patterns is evaluated for breast tumor detection. In order to scan the whole breast, the proposed DR sensor can be attached to the skin without a need for matching medium. The sensor has a wide half power beamwidth, therefore pa...

A very fast and efficient method for designing compact antenna arrays preserving the maximum channel capacity of multi input multi output (MIMO) systems using infinitesimal dipole model (IDM) theory is presented. Using this method each antenna element is replaced by a set of infinitesimal dipoles producing the same electric fields of the antenna. T...

A novel wideband dual-sense circularly polarized (CP) helical array antenna with enhanced isolation is proposed for the C-band satellite applications. The left-handed CP (LHCP) and the right-handed CP (RHCP) radiation in the same band are realized by using two concentric helical antennas with different radii and winding directions for the first tim...

A broadband dual-polarized cup dielectric resonator antenna (CDRA) with stable omnidirectional radiation patterns is presented in this correspondence. Both omnidirectional horizontally polarized (HP) and vertically polarized (VP) radiation patterns can be attained by exciting electric-dipole/TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xm...

CFP of a special issue in sensors

A novel single helix antenna with wideband and dual circularly polarized (CP) characteristics is proposed in this communication. The left-handed CP (LHCP) and right-handed CP (RHCP) radiations are achieved by exciting the helical antenna from the top end and bottom end, respectively. A grounded copper plane is loaded to the top of the helix to supp...

This paper proposes a circularly polarized ultra-thin flexible antenna with a flexible rectifier and power management unit (PMU) for smartwatch/wristband applications. The flexible antenna is compact (0.17λ0 × 0.20λ0 × 0.0004λ0) and has a stepped ground plane. A parasitic element is used at the substrate bottom to reduce the specific absorption rat...

An efficient and advanced decoupling technique is presented to significantly reduce the mutual coupling in the E -plane between two tightly-spaced half-split cylindrical dielectric resonator antennas (CDRAs). The proposed design offers around 59% reduction in the overall electrical footprint compared to the reference 2-port full CDRA antenna exhi...

A broadband high-gain multilayer transmitarray operating in X-band is proposed in this work. Unlike most transmitarrays achieving phase compensation by changing their element sizes, the length of striplines of the proposed transmitarray is adjusted to control a wider range of phase responses of identical array elements. By reducing the mutual coupl...

Due to the explosive growth of wireless communications, cost-effective streamline measurement of wireless devices’ peak beam is a highly desirable over-the-air testing demand. The directional antenna in the device under test (DUT) is usually subject to housing effects or manufacturing and assembly errors, causing deviations in its peak beam directi...

The microwave energy-harvesting (MEH) and microwave power transfer (MPT) technologies have become the most emerging areas of research nowadays. The microwave rectifier circuit is the bottleneck of both the MEH and MPT systems. The efficiency of the system depends on the power conversion efficiency (PCE) of the rectifier. Due to the recent advanceme...

This work presents a miniaturized quad-element multi-input multi-output (MIMO) antenna with low mutual coupling, inherent isolation, and easy upgradability for an Internet of Things (IoT) based high-speed smart digital entertainment network using ultra-wideband (UWB) technology. Ultra Wideband (UWB) technology is anticipated to play a significant r...

A low cost high gain circularly polarized antenna is proposed, the proposed antenna achieves a gain of 20-dBi, and an axial ratio bandwidth of 6.5%. The proposed antenna is extremely low in cost as it uses Printed Ridge Gap Waveguide (PRGW) technology. The use of PRGW technology suppresses the parasitic and back-lobe radiation from the feed, which...

A 2 x 2 multiple input multiple outputs (MIMO) circularly polarized CP-MIMO antenna is designed. An artificial magnetic conductor backs the slots to eliminate back radiation. Each slot is coupled to two orthogonal printed microstrip lines from a power divider that equally divides the power with a 90° phase difference for CP radiation. The proposed...

An intra-band pattern-corrected decoupling vertical conducting wall is realized by dielectric substrate with conductor cladding on both side wall between two tightly spaced H-plane microstrip patches with λ 0 /20 edge-to-edge spacing. The wall is grounded and two symmetrical slots are etched on the vertical substrate. The measured results agree wit...

A unique high gain antenna array with a 3D-printed dielectric polarizer is proposed. The packaging of the antenna array feeding structure is eliminated by aggregating the feeding network in between the antenna elements. This has a significant advantage in maintaining neat and symmetric radiation characteristics with low cross-polarization levels. T...

Extensive efforts have been made in designing large multiple-input multiple-output (MIMO) arrays. Nevertheless, improvements in conventional antenna characteristics cannot ensure significant MIMO performance improvement in realistic multipath environments. Array decorrelation techniques have been proposed, achieving correlation reductions by either...

This work proposes a novel millimeter-wave wideband circularly polarized antenna array for Internet of Things (IoT) applications. The proposed design addresses the issues of having IoT sensors deployed in remote locations or over large geographical regions. Elliptically-shaped dielectric resonator antennas (DRAs) are used as array elements to impro...

RF-based wireless energy harvesting (WEH) and wireless power transfer (WPT) are gaining attention due to their capability of powering various sensors and devices. A low-power device can be fed wirelessly by capturing ambient RF energy through a WEH system. In the case of a high-power device, a WPT system can provide the required amount of power usi...

Dielectric resonator magnetoelectric dipole (DRMED) arrays with enhanced isolation, reduced cross-polarization, and backward radiation are proposed for base station (BS) applications. The proposed antenna comprises an elevated dielectric res-onator antenna (DRA) on a small metal plate above a sizeable common ground plane. The DRA is designed in its...

In this work, a simplified analysis with a low dielectric-filled $Ka$ -band Y-junction circulator is designed and fabricated for the first time based on substrate-integrated gap waveguide (SIGW) technology. A new design equation is tailored based on a low dielectric filling considering the effect of fringing fields around the ferrite disk. The pr...

A novel high-isolation, monostatic, circularly polarized (CP) simultaneous transmit and receive (STAR) anisotropic dielectric resonator antenna (DRA) is presented. The Proposed antenna is composed of two identical but orthogonally positioned annular sectoral anisotropic dielectric resonators. Each circularly polarized (CP) resonator consists of alt...

A novel high-isolation dual-polarized in-band full-duplex (IBFD) dielectric resonator antenna (DRA) for satellite communications using a decoupling structure is proposed. Good isolation between transmit and receive ports is achieved by placing two identical linearly polarized resonators orthogonal to each other. Each resonator consists of a main re...

A sector-shaped compact $\pi/8$ partial substrate-integrated waveguide cavity antenna from the $\rm {TM}_{220}$ diagonal mode of the SIW cavity is presented. A 61 $\%$ size miniaturization is achieved compared to the SIW rectangular cavity in its complete mode configuration. The compact cavity radiator is used as an element of a compact 8-port...

p> A sector-shaped compact π/8 partial substrate-integrated waveguide cavity antenna from the TM220 diagonal mode of the SIW cavity is presented. A 61% size miniaturization is achieved compared to the SIW rectangular cavity in its complete mode configuration. The compact cavity radiator is used as an element of a compact 8-port multiple-input multi...

p> A sector-shaped compact π/8 partial substrate-integrated waveguide cavity antenna from the TM220 diagonal mode of the SIW cavity is presented. A 61% size miniaturization is achieved compared to the SIW rectangular cavity in its complete mode configuration. The compact cavity radiator is used as an element of a compact 8-port multiple-input multi...

A novel high-isolation, monostatic, circularly polarized (CP) simultaneous transmit and receive (STAR) anisotropic dielectric resonator antenna (DRA) is presented. The proposed in-band full-duplex (IBFD) CP-DRA system consists of two identical but orthogonally positioned anisotropic annular sector dielectric resonators composed of an alternating st...

Low-power wireless sensors will play a big role in smart city applications. These sensors require a power supply to function. Batteries are not optimal for such numerous sensor networks because of their limited life and need for regular maintenance; hence, they are not a universal solution. RF energy harvesting (RFEH) and wireless power transfer (W...

Low-power wireless sensors will play a big role in smart city applications. These sensors require a power supply to function. Batteries are not optimal for such numerous sensor networks because of their limited life and need for regular maintenance; hence, they are not a universal solution. RF energy harvesting (RFEH) and wireless power transfer (W...

This paper proposes a simple novel technique for self-isolating a MIMO antenna for mm-wave applications. MIMO antenna elements with inter-element separation of 0.2 mm (0.023λ at 35 GHz) and measured high isolation (> 50 dB) are presented. By observing the concentration of surface waves on the radiating patch, several rigorously optimized slots of d...

A high gain, low-cost antenna structure is designed for a smart car parking system. The antenna uses Printed Ridge Gap Waveguide (PRGW) technology, which is fully shielded, and suppresses any parasitic radiation from the feed, and minimizes back-lobe radiation. The proposed antenna uses a single MSL feed point, which eliminates the need for any com...

A new compact multifunctional pattern reconfigurable $2\times 2$ antenna array at 3.65 GHz with high gain and 16 (Multiple Input Multiple Output) MIMO modes is proposed. The single-element antenna includes 4 U-slots etched on the ground plane, with orthogonal slot orientations for polarization un-correlation, and fed using a reconfigurable feeding...

Novel multilayer Butler matrix (BM) miniaturizing layouts applicable to any $N$ $\times$ $N$ are proposed, reducing the conventional size by more than twofold. The layouts eliminate crossover couplers, considerably enhancing compactness and isolation. A $4$ $\times$ $4$ multilayer BM is designed based on the layouts, and the components...

The main cause of inefficiency in a rectenna is impedance mismatch between the receiving antenna and the rectifier. Rectifiers operate at different frequencies of interest, including 0.9 GHz, 1.8 GHz, 2.1 GHz, 2.45 GHz, 5.8 GHz, and above 5.8 GHz. However, these rectifiers are optimized to achieve maximum PCE at a particular frequency of interest a...

A space-shared full-duplex antenna with high isolation is proposed for universal serial bus (USB) dongles. A compact antenna with a compact size of 22 mm x 4 mm comprises a loop and dipole antennas, working as a vertical monopole and a horizontal dipole, respectively. The dipole-type is fed by a microstrip-slotline transition with filtering charact...

p>In this paper, a simple novel technique to self-isolate multiple-input-multiple-output (MIMO) antenna array elements for mm-wave applications is proposed. MIMO antenna arrays with inter-element separation of 0.2 mm (0.023λ at 35 GHz) and measured high isolation (>50 dB) are presented. Several rigorously optimized slots of different shapes, positi...

p>In this paper, a simple novel technique to self-isolate multiple-input-multiple-output (MIMO) antenna array elements for mm-wave applications is proposed. MIMO antenna arrays with inter-element separation of 0.2 mm (0.023λ at 35 GHz) and measured high isolation (>50 dB) are presented. Several rigorously optimized slots of different shapes, positi...

The requirements of 5G/6G promote progress in the miniaturization of the antenna array, which promotes the development of a closely spaced decoupling technique. However, the present techniques face the common problem of beam tilt if the spacing is close. Thus, a pattern-corrected, closely-spaced technique is proposed in this paper for the two patch...

Dual-band base station antenna (BSA) arrays with shared aperture have attracted considerable attention for the fifth-generation (5G) communication. The focus is mainly on decoupling between lower-band (LB) and higher-band (HB) antennas (i.e., cross-band decoupling). The in-band BSA decoupling techniques are usually not applicable to broadband dual-...

We introduce, for the first time, a new class of flexible bandstop frequency selective surface that provides very stable nearfield (NF) characteristics in the X -band, unlike the traditional FSSs. The structure's building block uses two layers of patches to reach the NF stability through their interaction. Periodic convoluted square loops on one...

A high-power Y-junction circulator is proposed for radar applications in the Ku-band (12–18 GHz). The design consists of two identical circulators combined using power splitters at all ports. The overall circulator network achieves 20-dB isolation level and return loss over the Ku-band with a peak power level of 14 kW. An internally matched divider...

A dual-polarized 1×4 slot antenna array is proposed supporting a millimeter-wave application. The dual-polarized antenna is excited with two microstrip lines based on Substrate Integrated Gap Waveguide. The simulated return loss for both ports achieves a sufficient matching level over 10% bandwidth and beyond 12 dBi Gain for both polarizations. The...

RF energy harvesting (RFEH) is an emerging technique in the field of wireless technology. The key components of this system are receiving antenna, matching network, and rectifier circuit. A rectifier circuit based on a tuned matching circuit is demonstrated in this paper for RFEH applications. The topology of this rectifier circuit is suitable for...

In practice, the broadband feeding network on the back side of an antenna can have a non-negligible effect on the antenna's back-radiation due to the feeding network's radiation contribution. Thus, a back-radiation cancellation scheme is proposed by co-designing the antenna and its feeding network to solve this problem. The antenna and its feeding...

A wideband cup dielectric resonator antenna (CDRA) with a monopole-like mode is presented. A new coil feeding structure is used, creating an equivalent magnetic current loop above the ground plane, exciting the CDRA $\textrm {TM}_{01 \delta } $ mode and an equivalent electric dipole at the adjacent frequency band. Thus, a broad bandwidth is achie...

Quantization of phase and/or amplitude has far-reaching effects on the radiation characteristics of the phased array (PA), including gain, minor lobe level, and point deviation. Traditionally, one common method to address such a nonlinear distortion is using random-phasing to interrupt the error periodicity. Here, we show that the distortion due to...

Rectifier is a fundamental element of a rectenna system that converts RF energy to direct current (dc). We proposed a triple-band rectifier using a novel matching technique and single series diode topology. First, we designed a single band rectifier and then converted it into a dual- and triple-band rectifier by introducing an appropriate transmiss...

A novel wideband self-decoupled loop-coupled antenna element is proposed for the fifth-generation (5G) multiple-input multiple-output (MIMO) smartphones. The proposed loop-coupled antenna element generates two resonance modes of 0.75 and 1 λ. With the help of these two resonance modes, a wide bandwidth is achieved. The self-decoupled performance is...

In this paper, the ports voltage and current of the TL are obtained using a new form of TL equation and its derivative. A system of linear equations is obtained according to the coupled versions of the telegrapher equations and the boundary conditions at terminals. The solution to that system of equations provides both far-end and near-end crosstal...

Orbital angular momentum (OAM) carrying vortex beams has been studied and realized using different methods. However, the designed devices are usually capable of generating fixed OAM modes. Here, the concept of a modular radiating system based on tightly cascaded transmitarrays (TAs) provi-ding a compact and user-accessible modular radiating system...

Dielectric resonator antenna (DRA) arrays with enhanced isolation and front-to-back ratio (FBR) are proposed in this letter. Specifically, each DRA element is mounted on a small and separated ground plane; all the DRA elements (with small ground planes) share a large common ground plane. Each DRA element is excited by two differential probes at its...

We investigate the dispersion, attenuation, amplification, and the area of solutions of electromagnetic (EM) waves in a lossy progressively disturbed medium. Approximate, rigorous, and numerical methods are fully developed for a lossy environment, and the differences, merits, and drawbacks are discussed. A new representation of the Floquet theorem...

A simple antenna with a 20-dBi gain is proposed. A thorough analysis of the propagation mechanism accompanied by a unique physical insight is provided. The realized structure has a low profile, low-cost, and compact features. A detailed insight into applying the Fresnel–Huygens principle is provided.

An array with large element spacing is designed for wide scanning. The element is designed to suppress the grating lobe by combining two radiation modes. The two modes are the $\mathrm{T}{\mathrm{E}_{\boldsymbol{1}\delta 1}}$ mode of a square dielectric resonator antenna (DRA) and the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:x...

A very small focal-to-diameter (F/D) ratio transmitarray for compact antenna test range (CATR) application is proposed in this article. The transmitarray comprises a feed antenna, a metasurface for phase modulation (MPM), and another one for amplitude modification (MAM). MPM and MAM are implemented using the same metasurface cell but with different...

Environmental sensors have come a long way over the last decade, surged in variety and capabilities. Such growth was impossible without developing wireless technologies, particularly antennas, thanks to advanced numerical computation software and artificial intelligence (AI). Sensors have numerous applications in industrial environments for purpose...

An efficient single-layer printed feed is used with a low-cost 3D printed polarizer. The feed is made on a single substrate layer. The proposed antenna gain is 15 dBi, and the overlapped impedance-axial ratio bandwidth is 20%. The proposed structure is a low-cost structure that can be fabricated in any modest fabrication facility. The feed does not...

A compact septum-based orthomode transducer (OMT) is designed to provide dual circularly polarized states for horn antennas. The OMT is back-fed by two rectangular ports separated by a stepped tapered septum from thick to thin walls towards the common port. The OMT covers 16.7% fractional bandwidth in the V-band (55 - 65 GHz), which coincides with...

The design and analysis of a compact printed Archimedean spiral electromagnetic bandgap (EBG) structure are presented for frequency shielding in microwave circuits, including antenna and bandpass filters. The EBG characterization resonating at 7.7 GHz is done through a performance matrix such as transmission and reflection coefficients and equivale...

Ground-penetrating radars (GPR) using ultrawideband (UWB) technology have attracted a lot of research interests worldwide for high-resolution sensing and material characterization. This research contribution, therefore, introduces a miniaturized lightweight UWB antenna with high-gain characteristics for applications in handheld GPR systems. The hig...

This paper comprises three parts, which exhaustively investigates the noise shaping approach in analog beamforming of phased array antenna. Specifically, the impact of digital filter design on different phased array applications is studied. In the first part, an overview of noise shaping in a hexagonal lattice phased array is investigated for the f...

In this paper, the characteristics of four spiral-facet structures are studied for RF energy harvesting (RFEH) applications for increasing the harvesting power from the surrounding atmosphere. A rectangular dielectric resonance antenna (RDRA) is selected and placed above an FR4-epoxy substrate. Metallic rectangular spirals are then placed on the di...

This work proposed a solution of structures built from stacking several dielectric substrates with the conducting cladding aiming for electrical contact between them (PEC-PEC). At millimeter-wave frequencies, surface roughness or imperfect flat surfaces present possible gaps that cause severe unexpected leakage. Many engineers overlooked this probl...

The recent advancement in commercial electromagnetic computational solvers, along with the computational processing resources gives a huge advantage for antenna designers to study complex structures and optimize their performance. In addition, the huge leap in processors speeds, and the advent of parallel processing techniques made it possible to r...

Correlations and mutual couplings in antenna arrays lead to performance deterioration of multiple-input-multiple-output (MIMO) systems. The relation between mutual coupling and correlation is complex, especially in non-isotropic multipath environments. Reducing mutual coupling does not guarantee an eventual reduction of the overall correlation and...

A simple antenna with a 20-dBi gain is proposed. A thorough analysis of the propagation mechanism accompanied by a unique physical insight is provided. The realized structure has a low profile, low-cost, and compact features, a detailed link to the Fresnel-Huygens principle is provided.

A surrogate-assisted defected ground structure design is proposed to suppress simultaneously E- and H-plane couplings in a 22 microstrip antenna array at 2.45 GHz. The DGS is designed and analyzed based on the magnetic current and mode theory. Machine learning is employed to sweep the DGS parameters within defined limits and fine-tune them to obtai...

This letter proposes a hybrid decoupling structure consisting of a neutralization dielectric board, metal baffle, and feeding network to enhance the isolation in a compact large-scale base station array. Both the neutralization- and partition-based schemes are utilized to reduce the mutual coupling between antennas. The neutralization dielectric bo...

A compact multi-layer substrate integrated waveguide (SIW) monopulse antenna array operating at X-band is proposed. The structure consists of four stacked layers, including one layer for the radiating 4 × 4 rectangular microstrip antenna elements and two SIW layers for the comparator network. The sum and difference modes provide orthogonal radiatio...

In this paper, a design of a monopole-based four-element MIMO array antenna is proposed. The design is based on a novel technique that makes a patch be a ground plane of the next patch. Thus, each patch has a dual function. This method is named the sharing technique. Thus, for the first time, two of such antennas can be merged, providing a subminia...