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David Lloyd - IEEE Xplore Author Profile

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This paper introduces a novel unit cell able to provide dual band operation for binary Reconfigurable Intel-ligent Surfaces (RIS). The operating bands are at 1.67 and 4.28 GHz with narrow bandwidths of 100 MHz approximately. The proposed cell shows stability with respect to variation in the incidence angle up to 30 deg for the TE polarized waves. To assert the wave control function, simulations ar...Show More
This paper outlines a methodology for assessing breakdown power in guiding structures under varied pressure and gas discharge conditions. Using a rectangular waveguide as an example, analytical equations and advanced electromagnetic simulation tools such as CST and HFSS are employed to evaluate breakdown power accurately. CST-Spark3D simulations demonstrate the impact of different pressures on bre...Show More
In satellite communication systems, Low Pass Filters (LPFs) are used to remove harmonics generated from the power source, minimize interference, and enhance the signal-to-noise ratio. Through the filter design process, various aspects must be considered such as the insertion loss, bandwidth, weight, and size. A stepped Impedance filter is a typical topology to realize the LPFs. The stepped impedan...Show More
This paper investigates the generation of vortex beams using a graphene metasurface at terahertz frequency band. A design of $20 \times 20$ unit-cell elements is described at 1.2THz. Each element is a graphene ring patch printed on silicon dioxide grounded substrate of $75 \times 75 \times 25 \mu \mathrm{m}^{3}$. The plane-wave excitation is investigated. The graphene reconfigurable surface conduc...Show More
A wideband periodic leaky-wave antenna (LWA) is proposed in this paper. By using lossy dielectric material inside the wedge-like guide as medium for wave propagation, a leaky mode is excited and results in widening the bandwidth. For certain tangential losses, this leaky-wave antenna achieves 20.34% 3-dB gain bandwidth with maximum gain of 19.7 dBi. The antenna experiences low side lobe level (SLL...Show More
This paper introduces a printed ridge gap waveguide (PRGW) hybrid coupler for millimeter wave applications in the Ka-band. The coupler achieves 33% bandwidth with more than 15 dB isolation and return losses. A small amplitude and phase imbalances of less than 0.3 dB and 3 degrees, are obtained, respectively by applying a combined design of two individual 8.34 dB couplers in cascaded manner. Simula...Show More
Low Earth Orbit (LEO) satellites are regaining interest in the wireless communications community as they will be heavily used in future wireless communication networks. LEO satellite transceivers require high-gain antennas with stable characteristics within the operating bandwidth. Horn antennas are commonly used as feeders for such transceivers. Moreover, multiple satellite systems use dual-polar...Show More
This paper introduces a comparator network for monopulse radars at the millimeter wave Ka band (26-29GHz). The network design is based on four Magic T’s connected in an assembly through various bend junctions and lines. The network is implemented using gap waveguide technology where each Magic T consists of a hybrid coupler loaded with a 90° phase shifter at the output ports. The full comparator n...Show More
Advances in wireless and satellite communications have created a demand for high-power microwave and millimeter-wave components due to cost, loss, and manufacturing complexity considerations. One of the newest and most promising guiding technologies is the Gap Waveguide, which is expected to have an effective role in mmWave and submmWave applications, not only in 5G communications but also in othe...Show More
In this paper, a design of a wideband Dielectric Resonator Antenna (DRA) with a stable high gain is proposed. The antenna design covers 14 GHz of bandwidth (S11<-10 dB) for the frequency range from 26 GHz to 40 GHz while delivering a high gain of 6.8 dBi at broadside (at 36.5 GHz).Show More
In this article, an ultra-wideband quad ridge horn antenna, covering two full successive bands, specifically K and Ka bands is introduced. The proposed antenna can carry vertical and horizontal signals simultaneously with a deep matching level over the entire band. The introduced antenna shape is proposed based on a mathematical formulation that minimizes the discontinuity between the feeding stru...Show More
In this paper, 8x8 series-fed patch antenna arrays for automotive radar phased arrays at 77 GHz are introduced. The proposed planar array antenna is composed of eight patch antennas with a series feed configuration, which are fed by a 1-to-8 feeding network. The designed array configurations operate over an impedance bandwidth of 75-80 GHz. All simulations are carried out using the CST Microwave S...Show More
In this paper, the effect of Split Ring Resonator (SRR) loading on mutual coupling reduction of Magneto Electric (ME)-dipole antennas fed through printed ridge gap waveguide (PRGW) is presented for millimeter-wave 5G applications. A miniaturized ME-dipole antenna with a −10 dB impedance bandwidth of 27 to 37 GHz and a peak gain of 10 dBi at 33 GHz is designed as the elementary antenna. As a proof ...Show More
A compact ultra-wideband printed ridge gap waveguide directional couplers for millimeter-wave applications are presented in this paper. A multi-layer coupling technique between two resonant patches is adopted to achieve a wider operating bandwidth with better amplitude and phase balance compared to single-layer technology. For this purpose, a systematic design procedure is deployed to achieve seve...Show More
In this article, a novel planar magic tee based on ridge gap waveguide (RGW) technology is proposed. The proposed design consists of a 3 dB hybrid coupler integrated with a 90° phase shifter implemented using a tapered dielectric slab. Each component is designed individually where the overall structure is globally optimized to achieve a deep matching level with minimum phase and amplitude imbalanc...Show More
Low Earth Orbit (LEO) satellites are regaining the interest of the wireless communications society, as they will be heavily utilized in future wireless communication networks. Transceivers of LEO satellites need high gain antennas with stable characteristics within the operating bandwidth. Corrugated horn antennas are the most commonly used feeds for such antennas. In addition, various satellite s...Show More
This communication presents a drone-to-satellite beam-forming antenna with multifunctional purposes. A glass material with a gradient coating configuration is exploited to realize a transparent structure. Beam tilting is obtained by controlling the phase distribution of an antenna by means of an inexpensive and passive surface. Simultaneously, solar cells are implemented on the proposed structure ...Show More
This communication presents a unique design of a dual-polarized wideband passive beam-switching antenna at millimeter-wave (mm-wave) bands for multiple-input–multiple-output (MIMO) pattern diversity applications, which exhibits low correlation between the ports and a broad tilt bandwidth (BW). A magnetoelectric (ME) dipole fed by a printed ridge gap waveguide (PRGW) as a quasi-TE source is conside...Show More
A 2-D beam switching dipole antenna working at 60 GHz is proposed. To realize this, a folded electric-field coupled (ELC) resonator is designed to achieve a high-refractive-index medium in the band of 57–64 GHz. By integrating an array of ELC resonators in the off-center of a printed dipole antenna in the E- and H-planes forming high-refractive-index medium lenses (metalenses) in each plane, the m...Show More
Recent communication systems are utilizing space diversity as a mean to increase the system capacity. Accordingly, the need for wideband and compact antennas has experienced a remarkable growth to support these new systems. In this article, a wideband antenna is proposed based on stripline technology. The proposed antenna is compact to enable the utilization of this structure as building block in ...Show More
A dual-polarized cavity antenna is proposed within a back-to-back perfect magnetic conductor (PMC) packaging, created for two inverted microstrip feed lines with a common ground. For the x-polarized radiation (RF1), the cavity is excited via a slot etched in the ground, whereas a fork divider directly excites the cavity to generate orthogonal y-polarized radiation (RF2). The design and analysis ar...Show More
In this paper, a high gain magneto-electric (ME) dipole scanning antenna array for millimeter-wave applications is presented. The antenna array is fed by a printed ridge gap waveguide (PRGW) Butler matrix to have four beams elevated at 20 o from the broadside direction. A hybrid gain enhancement technique including AMC mushroom shapes around the antenna array with a perforated dielectric substrate...Show More
A millimeter-wave wideband circularly polarized antenna with an improved gain is designed in this paper. The gain enhancement of 5 dB at 35 GHz is achieved by loading the CP antenna with FSS superstrate. The simulation results show that the proposed antenna has a wide -10 dB impedance bandwidth of 58.2%, a 3-dB AR bandwidth of 35%, a 3-dB gain bandwidth of 30%, and a maximum gain of 11.9 dBic at 3...Show More
The millimeter-wave (mm-wave) band is expected to be the optimal solution for future wireless communication systems as it provides a wide bandwidth, which enhancing data transmission rate. Therefore, high-directive antennas, principal elements for mm-wave wireless communications, are used at the mm-wave band as they can overcome the negative effect of high path losses. A transmit-array antenna (TA...Show More
The manuscript presents the design and characterization of a wideband front-end receiver, based on hollow waveguide technology, for the wireless access point (WAP) applications. The Ka-band receiver is comprised of a low-loss beam-switching antenna network (BSAN) with two-dimensional (2D) scanning property. For demodulation, the receiver uses an efficient six-port network (SPN) that is composed of...Show More