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Author

Ahmed A. Kishk

Other affiliations: Concordia University Wisconsin
Bio: Ahmed A. Kishk is an academic researcher from Concordia University. The author has contributed to research in topics: Antenna (radio) & Wideband. The author has an hindex of 10, co-authored 97 publications receiving 509 citations. Previous affiliations of Ahmed A. Kishk include Concordia University Wisconsin.

Papers published on a yearly basis

Papers
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Patent
08 Aug 1996
TL;DR: In this article, an improved subreflector antenna with lower sidelobes than prior art sub-reflector antennas is described, where a tapered, anisotropic, corrugated sub reflector is attached to a waveguide and located at the focus of a near-parabolic deep dish main reflector.
Abstract: An improved subreflector antenna with lower sidelobes than prior art subreflector antennas is disclosed herein A tapered, anisotropic, corrugated subreflector is attached to a waveguide and located at the focus of a near-parabolic deep dish main reflector The subreflector has corrugations of varying depth The varying depths of the corrugations result in varying reactance, or reactance taper, of the subreflector This taper is designed in such a manner to guide or steer the energy from the antenna feed to the main reflector in such a manner as to help assure sharply reduced sidelobes Further, the subreflector is physically shaped so as to further steer or guide the energy in the desired direction The deep geometry of the main reflector allows the reduced sized subreflector to be positioned within the rim of the main reflector such that the combination can be covered by a flat radome

158 citations

Journal ArticleDOI
TL;DR: In this paper, a gap waveguide-based compact monopulse array antenna, which is formed with four unconnected layers, was designed for millimeter-wave tracking applications at 85-105 GHz.
Abstract: This paper presents a gap waveguide-based compact monopulse array antenna, which is formed with four unconnected layers, for millimeter-wave tracking applications at $W$ -band (85–105 GHz). Recently developed gap waveguide technology removes the need for galvanic contact among metallic layers of waveguide structures, and thereby, makes the proposed antenna suitable for easy and low-cost manufacturing. In this context, a low-loss planar Magic-Tee is designed to be used in a monopulse comparator network consisting of two vertically stacked layers. The gap waveguide planar monopulse comparator network is integrated with a high-efficiency $16\times 16$ corporate-fed slot array antenna. The measured results of the comparator network show the amplitude and phase imbalance values to be less than 0.5 dB and 2°, respectively, over the frequency band of interest. The fabricated monopulse array antenna shows relative impedance bandwidths of 21% with input reflection coefficients better than −10 dB for the sum and difference ports. The null in the difference radiation pattern is measured to be 38 dB below the peak of the sum radiation pattern at 94 GHz. The measured gain is about 30 dBi for the same frequency. The low-loss performance of the comparator network and the feed network of the proposed array, together with the simple and easy manufacturing and mechanical assembly, makes it an excellent candidate for $W$ -band compact direction-finding systems.

100 citations

Journal ArticleDOI
TL;DR: In this paper, an advanced wave engineering technique based on unidirectional frequency generation and spatial decomposition in general space-modulated (STM) slabs is introduced.
Abstract: This paper introduces an advanced wave engineering technique based on unidirectional frequency generation and spatial decomposition in general space–time-modulated (STM) slabs. The extraordinary wave engineering provided by such slabs is comprised of unidirectional wavefront shaping, nonreciprocal frequency generation, and spatial decomposition of ST harmonics (STHs). We first derive a rigorous analytical solution for the wave scattering from general ST permittivity- and permeability-modulated (STP&PM) slabs. The analytical solution considers the most general form of spatiotemporal variation and wave incidence, i.e., oblique incidence and scattering from time-periodic spatially aperiodic/periodic STP&PM slabs. The spatial aperiodicity may be utilized for further spectrum engineering and suppression of undesired STHs. Next, it will be shown that an equilibrated ST refractive-index-modulated slab with equal permittivity and permeability modulation strengths exhibits highly enhanced nonreciprocity. The FDTD numerical simulation of general STM slabs is presented, providing extra leverage for the analyses of wave propagation and scattering in such media. We show that oblique incidence to an STM slab yields nonreciprocal spatial decomposition of generated STHs. The explored peculiar properties of STM slabs under oblique incidence is expected to pave the way for the realization of new class of subharmonic generators, radars, illusion cloaks, and spatial mixers and isolators.

55 citations

Journal ArticleDOI
TL;DR: In this article, a high-gain array antenna, diplexer, and circuitry consisting of a transmitter (Tx) and a receiver (Rx) monolithic microwave integrated circuits (MMICs) on a carrier board is successfully integrated into one package with a novel architecture and a compact form.
Abstract: This paper presents the design and realization of a high data rate radio front-end module for point-to-point backhaul links at E-band. The design module consists of four vertically stacked unconnected metal layers without any galvanic and electrical contact requirements among the building blocks, by using gap waveguide technology. The module components are a high-gain array antenna, diplexer, and circuitry consisting of a transmitter (Tx) and a receiver (Rx) monolithic microwave integrated circuits (MMICs) on a carrier board, which is successfully integrated into one package with a novel architecture and a compact form. The diplexer consists of two direct-coupled cavity bandpass filters with channels at 71–76 GHz and 81–86 GHz with a measured return loss of 15 dB and an isolation greater than 50 dB. A wideband $16\times 16$ slot array antenna with a measured gain of more than 31 dBi is used to provide high directivity. The measured results show that the packaged transmitter provides a conversion gain of 22 and 20 dB at 76 and 86 GHz, respectively, with an output power of 14 and 16 dBm at 1-dB gain compression point, at the same frequencies. The packaged receiver shows an average conversion gain of 20 dB at 71–76-GHz and 24 dB at 81–86-GHz bands. A real-time wireless data transmission is successfully demonstrated with a data rate of 8 Gbit/s using 32-quadrature amplitude modulated signal over 1.8-GHz channel bandwidth with spectral efficiency of 4.44 bit/s/Hz. The proposed radio front end provides the advantages of low loss, high efficiency, compact integration, and a simple mechanical assembly, which makes it a suitable solution for small-cell backhaul links.

53 citations

Journal ArticleDOI
TL;DR: In this article, a compact structure with slot splitting meandered lines defected ground is proposed to reduce the mutual coupling between two microstrip antennas with a center-to-center distance of 0.38λ.
Abstract: A compact structure with slot splitting meandered lines defected ground is proposed to reduce the mutual coupling between two microstrip antennas with a center-to-center distance of 0.38λ. The meandered line defected ground structure is symmetrically etched on the ground between the microstrip antennas. The proposed structure is optimized and explained by the common/differential mode theory. For experimental verification, the structure is fabricated and measured. Simulation and measurement results with excellent agreement show that the mutual coupling can be reduced significantly using the proposed structure. In addition, significant improvement is achieved in radiation efficiency, realized gain, and the decoupled array's envelope correlation coefficient.

49 citations


Cited by
More filters
01 Jan 2016

733 citations

Patent
16 Oct 2015
TL;DR: In this paper, the authors describe a system that receives, by a feed point of a dielectric antenna, electromagnetic waves from a core coupled to the feed point without an electrical return path, and radiates a wireless signal responsive to the electromagnetic waves being received at the aperture.
Abstract: Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.

330 citations

Patent
17 May 2016
TL;DR: In this paper, a distributed antenna and backhaul system provide network connectivity for a small cell deployment using high-bandwidth, millimeter-wave communications and existing power line infrastructure, rather than building new structures, and installing additional fiber and cable.
Abstract: A distributed antenna and backhaul system provide network connectivity for a small cell deployment. Rather than building new structures, and installing additional fiber and cable, embodiments described herein disclose using high-bandwidth, millimeter-wave communications and existing power line infrastructure. Above ground backhaul connections via power lines and line-of-sight millimeter-wave band signals as well as underground backhaul connections via buried electrical conduits can provide connectivity to the distributed base stations. An overhead millimeter-wave system can also be used to provide backhaul connectivity. Modules can be placed onto existing infrastructure, such as streetlights and utility poles, and the modules can contain base stations and antennas to transmit the millimeter-waves to and from other modules.

298 citations

Patent
07 Jun 2016
TL;DR: In this article, a distributed antenna system is provided that frequency shifts the output of one or more microcells to a 60 GHz or higher frequency range for transmission to a set of distributed antennas.
Abstract: A distributed antenna system is provided that frequency shifts the output of one or more microcells to a 60 GHz or higher frequency range for transmission to a set of distributed antennas. The cellular band outputs of these microcell base station devices are used to modulate a 60 GHz (or higher) carrier wave, yielding a group of subcarriers on the 60 GHz carrier wave. This group will then be transmitted in the air via analog microwave RF unit, after which it can be repeated or radiated to the surrounding area. The repeaters amplify the signal and resend it on the air again toward the next repeater. In places where a microcell is required, the 60 GHz signal is shifted in frequency back to its original frequency (e.g., the 1.9 GHz cellular band) and radiated locally to nearby mobile devices.

296 citations

Patent
15 Sep 2014
TL;DR: In this article, the authors describe a device that facilitates transmitting electromagnetic waves along a surface of a wire that facilitates delivery of electric energy to devices, and sensing a condition that is adverse to the electromagnetic waves propagating along the surface of the wire.
Abstract: Aspects of the subject disclosure may include, for example, a device that facilitates transmitting electromagnetic waves along a surface of a wire that facilitates delivery of electric energy to devices, and sensing a condition that is adverse to the electromagnetic waves propagating along the surface of the wire. Other embodiments are disclosed.

288 citations