Davoud Zarifi

• University of Kashan

This work presents a high-gain D-band slot array antenna with a corporate-fed distribution network designed by the gap waveguide. The gap waveguide technology is employed for overcoming the challenge of appropriate electrical contact related to the mechanical assemblage of the antenna feed network and the radiation layer. The antenna includes $24\...

A slot array antenna with dual‐circular polarisation (CP) is presented in this paper. To overcome the fabrication and loss challenges in mm‐wave frequencies, the gap waveguide technique is utilised. The right and left hand circular polarisation (RHCP and LHCP) radiations are achieved using slots‐fed stepped septum polariser on the longitudinal slot...

The current paper presents a six-port low-loss waveguide coupler based on ridge gap waveguide structure with potential application in various mmWave wireless systems. The challenges in the fabrication faced in mmWave frequencies can be overcome by using the gap waveguide technology. The excitation of presented six-port junction is done by standard...

This paper presents a design of a 4×4 circularly polarized (CP) patch antenna array based on gap waveguide (GW) sequential feeding network. The proposed antenna single element consists of an aperture coupled circular patch antenna. A two-level sequential feeding network, that is used to enhance the polarization bandwidth, is designed, and investiga...

In this paper a novel multi-layer slot array antenna based on printed ridge gap waveguide (PRGW) technology with dual circular polarization (CP) at Ka band is proposed. This antenna consists of five layers, two dielectric substrates as a transition from PRGW to coax line and a branch line coupler (BLC) as an antenna feeding network, and three metal...

The design and fabrication of a wideband millimetre‐wave 0‐dB coupler is proposed in this paper using gap waveguide technology for low‐loss and high‐power applications in 30‐GHz frequency band. To overcome the fabrication challenges in millimetre‐wave frequencies, the gap waveguide technique is utilised. Two gap waveguide‐based coaxial‐ and wavegui...

This paper proposes a wideband coaxial line to rectangular waveguide transition to use in high-power microwave systems. The proposed structure consists of a supershape excitation probe in a rectangular waveguide. The structure’s performance was measured and verified by fabricating a prototype. It was found that the measurement results are in good a...

A novel wideband high-power single-pole two-throw (SP2T) switch based on gap waveguide technology is presented in this article. The proposed switch has a SP2T structure and consists of three standard WR62 waveguide ports. Due to the advantage of gap waveguide technology, the switch design structure requires no electrical contact between its differe...

This paper presents a novel wideband gap waveguide mechanical switch for low-loss and high-power radar and satellite applications. The proposed design has contactless waveguide structures and therefore the different conducting layers are not required to make physical contact joints. This property can make the structure more flexible and simple to f...

A broadband magic-T junction for millimeter-wave applications is proposed in this article. Gap waveguide technology is employed to overcome fabrication and assembly challenges at millimeter-wave frequencies. The measured results for a fabricated prototype are in good agreement with the simulations. The measurements indicate that the fabricated stru...

The design, development and fabrication of compact microstrip ring-hybrid couplers are presented in the present paper. In order to obtain miniaturization, λ/4 microstrip lines in a conventional microstrip ring-hybrid are equivalently substituted with quarter-wavelength supershape transmission lines. The results show that almost 74% size reduction c...

This article deals with the design of a broadband cavity‐backed microstrip‐fed wide‐slot antenna array for L‐band applications. For verification purpose, a sample 1 × 4‐element antenna array has been designed, manufactured and tested. Experimental results have shown satisfactory agreement with the simulation. The proposed antenna array exhibits a m...

Due to the development of mobile communication devices, the miniaturized antenna design is becoming an important consideration today. In this paper, a new small microstrip antenna is proposed in which the patch is curved along its width to force the electrical currents to move in a longer path. Consequently, the electrical size of patch is increase...

In this article, a broadband 3-dB directional coupler is proposed using groove gap waveguide (GGW) structures. Gap waveguide technology has been introduced to overcome manufacturing and assembling challenges of different millimeter-wave components and devices. The presented coupler has wideband coupling flatness with low return loss in 60-GHz frequ...

H-plane horn antenna using gap waveguide technology is proposed. The advantage of this technology is its air-filled feature, which improves the impedance matching compared with substrate integrated waveguide (SIW) horn antennas. Corrugated walls as soft surfaces are used on the outer surfaces of the upper and lower horn plates, which act as barrier...

This article deals with the design of Moreno cross‐guide couplers based on supershapes for X‐band applications. Crossed‐waveguide couplers are mainly used due to their compact structures. In these couplers, cross‐aperture structures are usually employed to offer flat coupling and high isolation. In the present article, the possible shapes for apert...

A class of wideband directional couplers suitable for achieving different coupling levels are proposed in this work. The proposed couplers have been implemented using double-layer groove gap waveguide at millimeter-wave frequency range. They are composed of two parallel groove gap waveguide parts placed on top of each other in such a way that the c...

A groove gap waveguide diplexer is presented for Ku‐band applications. The manifest advantage of using this technology is its ability to remove requirement of electrical contact between the different layers of the structure. The proposed diplexer is composed of coupled gap waveguide resonators without additional waveguide elements. A prototype is f...

In this paper, the low loss groove gap waveguide is used for the design of a filter-horn antenna in the millimeter wave (mmw) frequency band of 60 GHz. The antenna consists of three sections: transition from rectangular waveguide WR- 15 to the groove gap waveguide, 3rd order coupled resonator band pass filter and horn antenna. The antenna pattern i...

A wideband 8 ×8-element slot antenna array based on ridge gap waveguide feeding network has been proposed for mmWave applications. The antenna sub-array consists of four radiating slots which are excited by a groove gap cavity layer. Compared with previously published works, the proposed planar antenna array has quite wide impedance bandwidth. The...

This communication presents a wideband aperture-coupled patch antenna array based on Ridge Gap Waveguide (RGW) feed layer for 60-GHz applications. The novelty of this antenna lies in the combination of relatively new gap waveguide technology along with conventional patch antenna arrays allowing to achieve a wideband patch antenna array with high ga...

In this letter, a groove gap waveguide (GGW) based 3-dB directional coupler is proposed. The designed component is composed of three parts: GGW structure, extra matching pins and GGW to standard SMA transition. The designed quadrature 3-dB coupler is optimized to work in the Ku-band covering 13–15 GHz. Measured results show that over 14.3% bandwidt...

Wideband design of power dividers, T-junctions, and transitions based on groove gap waveguide (GGW) technology is presented in this paper with the goal to use these components in high-gain millimeter-wave antenna array design at 60-GHz frequency range. Since this GGW technology does not require electrical contact between the different metal layers...

This paper presents an analytical method for the reconstruction of permittivity profile of an inhomogeneous slab. The proposed method which is based on state transition matrix combines state space formulation and frequency domain data. This methodology and formulation lead to an accurate inversion of complex inhomogeneous profiles. Comparing with o...

This paper deals with the design and experimental verification of a dual-band metamaterial radar absorbing structure for the reduction of radar cross section (RCS) of a microstrip antenna. A Metamaterial Absorber (MMA) is designed to work in X-band with absorption rate near 100%. To demonstrate the effective performance of the proposed structure, i...

Anechoic chambers are used for indoor antenna measurements. The common method for anechoic chamber construction is to cover all inside walls by the EM absorbers. A fully metallic parabolic chamber is presented in which the propagation of the EM waves inside the chamber is controlled and they are guided to an absorber. In the proposed method, an app...

In this paper, a wideband microstrip line to groove gap waveguide (GGW) transition is proposed. The designed structure is composed of two parts: a 50-Ohm microstrip that feeds a planar probe and a GGW structure. The transition structure is optimized to work at V-band from 50 to 70 GHz.

A wideband high-gain high-efficiency 16 × 16-element slot antenna array is presented for 60-GHz band applications. The antenna is designed based on gap waveguide technology. The most important advantage of using this technology is its ability to decrease complexity and cost of fabrication because there is no requirement of electrical contact betwee...

In this paper, a high gain high efficiency 16×16-element slot antenna array is presented for 60 GHz applications. The antenna is designed based on gap waveguide technology. A corporate feed network is realized by a texture of pins and a guiding ridge in a bottom plate. The simulated results show about 16% of reflection coefficient bandwidth (|S11|...

This paper deals with the design of low loss wideband power dividers based on groove gap waveguide (GGW) technology. The advantages of GGW power dividers are low insertion loss, high power handling capacities, ease of fabrication and compatibility with integrated microwave networks. A 64-way power divider is designed and used as the feeding network...

A free-space method for the reconstruction of longitudinally inhomogeneous chiral material is proposed in this paper. The developed technique is based on the use of state transition matrix method. The proposed approach provides the permittivity profile of the medium in terms of the reflection and transmission coefficients. To test the performance o...

A free-space method for the reconstruction of longitudinally inhomogeneous chiral material is proposed in this paper. The developed technique is based on the use of state transition matrix method. The problem is first formulated as an inverse scattering one based on a state transition matrix in terms of the unknown constitutive parameters. By using...

This paper presents a new method to model inhomogeneous media in commercial electromagnetics software, especially FEKO. In this method, the inhomogeneous medium is fragmented to some homogeneous pieces. If the size of these pieces is chosen correctly, then the electromagnetic behaviors of them and inhomogeneous medium are the same. Since creating t...

In this study, the computation and properties of the state transition matrix of inhomogeneous planar layered media are investigated. Furthermore, non-reciprocity of inhomogeneous planar layered media is shown using the transition matrix method. This theorem says that the plane wave transmission coefficients for a slab with inhomogeneity along the d...

This study presents an analytical approach for the electromagnetic characterization of one-dimensional inhomogeneous media. The proposed approach provides the permittivity profile of the medium in terms of the reflection and transmission coefficients. The inverse solution of the permittivity profile is obtained with the help of the state-transition...

An effective non-iterative method is developed for determination electromagnetic parameters of complex materials with anisotropy. Unlike the existing methods, the proposed method can extract the electromagnetic tensor parameters of materials with off-diagonal anisotropy using co- and cross-polarized reflection and transmission without using iterati...

This study presents a parameter retrieval technique based on the state space approach for the electromagnetic characterisation of biaxial anisotropic structures. First, the formulation of a 4 x 4 transition matrix method for the analysis of forward scattering problems is reviewed; then a procedure for the extraction of the constitutive tensor param...

A dual-band artificial magnetic material and then a dual-band double-negative metamaterial structure based on symmetric spiral resonators are presented. An approximate analytical model is used for the initial design of the proposed structures. The electromagnetic parameters of the proposed metamaterial structure retrieved using an advanced paramete...

The electromagnetic characterization method based on the state space approach, which has been proposed for parameter retrieval of uniaxial chiral composites is extended in order to extract the electromagnetic parameters of biaxial bianisotropic media as well. The properties of state transition matrix of a biaxial bianisotropic layer are presented a...

We present the design, characterization, and experimental verification of a dual-band metamaterial absorber (MA) in the microwave frequencies. The proposed MA consists of a metallic gammadion-shaped structure and a complete metal layer, separated by a dielectric spacer. The results show that the proposed MA has two absorption peaks at nearly 5.6 GH...

In this paper, a novel near zero refractive index metamaterial is designed and used as a superstrate of a microstrip antenna. In order to decrease the return loss, particle swarm optimization (PSO) is used to optimize the metamaterial structure. One of the important factors in the antenna designing, which influences the radiation efficiency, is to...

An analytic frequency domain technique is presented for reconstructing constitutive parameters of uniaxial chiral media. First, forward analysis of the problem is discussed using 4 × 4 transition matrix method. Based on this analysis, a procedure is illustrated for retrieving all the constitutive tensor parameters of uniaxial chiral slab. In the pr...

An analytical approach is introduced to analyze scattering and wave propagation in the problem involving a line source near an inhomogeneous chiral slab based on combination of Fourier transform and Taylor's series expansion. In this method, Taylor's series expansion is used for all electromagnetic parameters and Fourier transformed electric and ma...

The parameter retrieval method based on the causality principle and Kramers-Kronig relations, which has been proposed for extracting effective parameters of metamaterials (MTMs) is extended to extract effective parameters of chiral metamaterials (CMMs) aswell. Using Kramers-Kroning relations, the branch selecting problem which is the challenge of e...

In this paper, the propagation of electromagnetic waves through an infinite slab of biaxial chiral medium is analytically formulated for an arbitrary incidence using the 4×4 transition matrix method. In this powerful method, a state vector differential equation is extracted whose solution is given in terms of a transition matrix relating the tangen...

This paper deals with the introduction of an approach for the electromagnetic characterization of homogeneous chiral layers. The proposed method is based on the state-space approach and properties of a 4×4 state transition matrix. Based on this, first, the forward problem analysis through the state-space method is reviewed and properties of the sta...

An electromagnetic inversion method is presented to reconstruct the constitutive parameters of an inhomogeneous bianisotropic slab. The measured co- and cross-reflection and transmission coefficients are used to extract the electromagnetic parameters profiles of the inhomogeneous bianisotropic media from the proposed method, using truncated Fourier...

A general method of analyzing the wave propagation and scattering problem for inhomogeneous planar-layered chiral media is presented. It is assumed that the constitutive parameters are known at all or only at some points along the thickness of the inhomogeneous chiral layer. The analysis is based on using finite difference method to solve a state v...

This paper presents a frequency domain technique for reconstructing the constitutive parameters of inhomogeneous planar layered chiral media based on an optimization approach. The measured co- and cross-re°ection and transmission coe±cients are used to extract pro¯les of electromagnetic parameters of the inhomogeneous chiral media. To identify the...

An analytical method based on combination of Fourier transform and Taylor's series expansion is presented for analyzing interaction of electromagnetic cylindrical waves with inhomogeneous planar layered media. In the proposed method, constitutive parameters and Fourier transformed electric and magnetic fields of inhomogeneous layer are expressed us...

In this paper, the applications of chiral layers and metamaterials as radar absorbing materials are investigated. A perfect electric conductor plate covered by a chiral metamaterial is considered and after the formulation of the problem, reflection of the structure under an oblique plane wave incidence of arbitrary polarization is investigated. The...

In this paper, miniaturized chiral metamaterial (CMM) structures with smaller unit cells or lower resonant frequencies are investigated. In achieving this purpose, three general ideas are proposed: using dendritic fractal geometry, using some wideband antenna designs, and utilizing echelon meandered structures. Based on these methods, some miniatur...

A novel dual-band chiral metamaterial based on the conjugated gammadions structure is proposed. Simulation and experimental results, which are in a very good agreement, indicate that the proposed structure exhibits giant optical activity and a negative refractive index for right and left circularly polarized waves due to its strong chirality in two...

In this paper, an analytic frequency domain method based on Taylor’s series expansion is investigated to analyze different terminated homogeneous and inhomogeneous planar layered chiral media. The validity of the presented method is verified considering some special types of chiral media, and then the application of inhomogeneous planar layered chi...

In this paper, an analytic frequency domain method based on Taylors series expansion is introduced to analyze inhomogeneous planar layered chiral media for an arbitrary linear combination of TM and TE polarizations.

Development of chiral metamaterial (CMM) structures in order to achieve miniaturized CMMs and dual-band CMMs are aimed in this paper. In achieving the first purpose, two general ideas are proposed: using dendritic fractal geometry, and using wideband antenna designs. Based on these methods, some miniaturized CMM structures are designed. Afterwards,...

Abstract In this paper, the reflection and transmission of an electromagnetic plane wave from (through) planar layered of inhomogeneous bi-anisotropic media are considered. Inhomogeneous layers are decomposed into thin homogeneous sub-layers, and the method of propagators is used for analysis of the wave interaction with planar multi-layered of hom...

In this paper, an analytic frequency domain method based on Taylor's series expansion approach is introduced to analyze inhomogeneous planar layered chiral media for an arbitrary linear combination of T M and T E polarizations. In the presented method, electromagnetic parameters of inhomogeneous chiral media and also the electric and magnetic field...

This paper presents the application of chiral metamaterial covers for improving the circularly polarized microstrip antenna performance. Semi-planar chiral metamaterial structures with a near zero refractive index are designed and utilized for enhancing the directivity of circularly polarized single and array patch antennas. Numerical results show...

A novel dual-band semi-planar chiral metamaterial structure is proposed in this paper. The optical characteristics and effective parameters of the proposed structure extracted using simulation results show that the proposed structure exhibits: 1) exceptionally greater optical activity compared with other published similar semi-planar chiral metamat...

The influence of semi-planar chiral metamaterial (CMM) structures on the important characteristics of circularly polarized (CP) antennas is investigated in this paper. Based on this idea, CP planar two-arm Archimedean spiral (ARSPL) antenna and helical antenna are designed and the effects of chiral covers on their gain (or directivity), axial-ratio...