In this article, we present two efficient leaky-wave antennas (LWAs) with stable radiation pattern, operating at 60 GHz. Both antennas exhibit attractive properties such as significantly reduced beam-squint, low loss, low sidelobes, high directivity, and simple manufacturing. The beam-squint of conventional LWAs is reduced by refracting the leaked waves in a dispersive lens and the low sidelobe levels

Presents the table of contents for this issue of the publication.

Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.

It is with heartfelt sadness that we inform you of the tragic loss of our Associate Editor Prof. Mojgan Daneshmand, who was a passenger on the Ukraine International Airlines flight that crashed after takeoff from Teheran International Airport on January 8, 2020. Her husband, Prof. Pedram Mousavi, and their daughters, Darya and Darina, also died in the crash. Prof. Daneshmand and Prof. Mousavi were

This article presents a compact absorptive filtering patch antenna. It consists of a filtering patch antenna and a bandstop filter (BSF), with their transfer functions being complementary to each other. A slot is fabricated in each of the patch and ground, giving a total of two radiation nulls for the lower bandedge. By using a dual-stub feed, two radiation nulls are also obtained for the upper bandedge

General formulas are proposed for thoroughly evaluating the radiation efficiency of traveling-wave antennas operating in any radiating regime. Indeed, existing theoretical models only work in the scanned-beam region, where the radiating mode is considerably above cutoff and the perturbation method applies. The analysis provided here extends the application of the perturbation method close to the cutoff

A longitudinally slotted TE 20 -mode-driven substrate integrated waveguide (SIW) leaky-wave antenna (LWA) with low side-lobe and low cross-polarization is proposed and presented for millimeter-wave applications. In this work, a pair of long slots is etched symmetrically on the top broadside of an SIW working in the TE 20 mode. With the odd-symmetry of TE 20 mode field distribution, the even-symmetrically

A hybrid metasurface (HMS) is proposed to form a low-profile wideband antenna array. The antenna element is an array of $4\,\,\times4$ square metal patches and fed by a $50~\Omega $ microstrip line through an H-shaped coupling slot on the ground plane. Only are the edge patches of HMS antenna element grounded by shorting pins for the suppression of surface waves and cross-polarization levels as well

A very low-profile sub-THz high-gain frequency beam steering antenna, enabled by silicon micromachining, is reported for the first time in this paper. The operation bandwidth of the antenna spans from 220 to 300 GHz providing a simulated field of view of 56°. The design is based on a dielectric filled PPW leaky-wave antenna fed by a pillbox. The pillbox, a two-level PPW structure, has an integrated

This article presents a type of miniaturized high-efficiency patch antennas for UHF radio frequency identification (RFID) reader applications based on the composite right-/left-handed (CRLH) negative order resonance. Miniaturization is achieved by using the first negative order resonance (−1st mode). These proposed CRLH resonators are realized by etching gap on the patch surface, which acts as a series

In this article, a new 3-D printed dual tapered nested antenna design is presented. The antenna is composed of two tapered helical arms that wrap around each other in opposite orientations to exhibit orthogonal circular polarization schemes. The nested tapered helices are 3-D laser printed with copper platting. The outer helical arm is tailored to resonate at 2.4 GHz, while the inner arm is designed

A wideband and low-profile cross-slot pattern reconfigurable antenna for electromagnetic imaging systems is proposed. The antenna is designed to cover the human chest area with steerable unidirectional radiation patterns at 0.7–0.9 GHz. The antenna is comprised of a corrugated cross-slot as the main radiator, and four parasitic slots with four p–i–n diodes operating as reflectors. An embedded feeding

In this article, a novel on-glass antenna which is transparent, miniaturized, and multiband is presented. First, the antenna achieves more than 80% transparency. This is realized by removing as much as possible the metal pattern, without compromising the operational electric current flow. Second, the antenna is electrically small, $0.13\lambda \times 0.19\lambda $ at 0.95 GHz. This is realized by choosing

In this article, an ultra-wideband metasurface lens is designed and integrated into an antipodal Vivaldi antenna (AVA) to improve its radiation directivity without affecting its efficiency and return loss characteristics. The metasurface lens consists of high permittivity metamaterial unit cells which resonate at frequencies far away from the operation bandwidth of 1–6 GHz. Electric field distributions

This article presents the design and optimization of a deployable 1 m mesh reflector compatible with a 12U-class CubeSat. This antenna is designed for telecommunication and is compatible with NASA’s deep-space network (DSN) at ${X}$ -band (i.e., uplink: 7.145–7.19 GHz; downlink: 8.4–8.45 GHz) and Ka -band frequencies (i.e., uplink: 34.2–34.7 GHz; downlink: 31.8–32.3 GHz). Three right-handed circularly

A novel cylindrical Luneburg lens operating at 26 GHz-band using hole drilling technology are reported, aiming at proper radiation patterns. The cylindrical Luneburg lens antenna converge microwaves in the plane perpendicular to the generatrix of the cylinder. An E-plane-focused cylindrical Luneburg lens antenna with the thickness of 20 mm and diameter of 88.2 mm is proposed for working at 26 GHz.

This article presents a 3-D-printed dielectric rod antenna with wideband circular polarization. The proposed dielectric device comprises two main components: a launching part and a radiating part. The launching part consists of three cylindrical sections with stepped permittivity for wideband impedance matching to the rectangular waveguide feed. The radiating part is a tapered dielectric rod with two

A fully metallic radiating element is presented in this article for single and dual circular polarization applications. The shape of the radiating element corresponds to a bow-tie-shaped field rotator designed to generate two orthogonal modes in quadrature as a basis for circular polarization. The bow-tie-shaped basic element is able to provide low axial ratio with a compact, easy-to-manufacture profile

For the first time, a planar and low-profile magnetic loop antenna is proposed for designing an omnidirectional metal-mountable radio frequency identification (RFID) tag antenna. The proposed tag antenna, which consists of an annular slot exciter, a shorted patch, two shorting stubs, and four notches, can be easily made on one side of a flexible polyimide film. It has a dimension of 38 mm $\times \

This article presents a study of transmission through arrays of periodic sub-wavelength apertures. Fundamental limitations for this phenomenon are formulated as a sum rule, relating the transmission coefficient over a bandwidth to the static polarizability. The sum rule is rigorously derived for arbitrary periodic apertures in thin screens. By this sum rule we establish a physical bound on the transmission

A switchable $S$ -/ $C$ -band antenna array is presented with dual polarization and modularity. A $2\times 2\,\,S$ -band antenna array can be reconfigured into a $4\times 4\,\,C$ -band antenna array within the same physical aperture. A narrow ground strip inside the slot-ring antenna is used to reduce the mutual coupling between antenna elements and suppress the null in the radiation patterns in the

In this article, a miniaturized dual-band dual-polarized slot antenna array is proposed for base station applications. It consists of two closely located $1 \times 4$ subarrays for the digital cellular system (DCS) and wideband code division multiple access (WCDMA) operations. The band-notched slot antenna (BNSA) is designed and adopted as the subarray element with radiation-suppression characteristic

This article presents a novel design of filtering reflectarray antenna, an integrated module for the combination of filtering and high-gain radiation performance. The filtering reflectarray consists of two-section metal pixel waveguide elements, which can realize the optimized aperture reflection phase distributions in the operating band $f_{1~ \le }f~ _{\le }~f_{2}$ to yield high-gain radiation. Below

A novel wideband-connected parallel slot array for wide-angle scanning applications is proposed in this article. Different from conventional connected slot arrays, the proposed array consists of dual parallel slots, where the introduced parasitic slot acts as an additional series capacitor. The connected parallel slot array can realize low and moderate active input impedances and achieve wide bandwidth

A complete and unified time- and frequency-domain study on 4-D antenna arrays including mutual coupling effect is presented in this article. The “instantaneous” active reflection coefficient (ARC) or power pattern as a function of time and the “averaged” ARC or power pattern as a function of frequency are introduced to evaluate the port matching and the mutual coupling in 4-D arrays, respectively.

The self-curing decoupling technique is substantially extended to apply to multi-input multi-output (MIMO) antenna arrays in mobile terminals. Using this proposed technique, the mutual coupling between antennas can be reduced by inlaying lumped element capacitors on the ground plane. The decoupling method does not require any physical connection or obstruction between coupled antennas. The significance

This article presents the design and demonstration of Gaussian-beam transmitarray antennas at millimeter-wave frequencies. The main design tradeoffs and theoretical performances are first investigated numerically. Next, two antenna prototypes are designed in ${V}$ -band and fabricated in printed-circuit-board technology. These prototypes are validated experimentally through transmission measurements

In this article, integrated millimeter-wave (mmW) broadband circularly polarized (CP) single-beam/multibeam antennas (MBAs) are reported. The antennas comprised a Berry-phase (BP) transmit-array (TA) containing three layers of slotted elliptical metallic resonator arrays and a cluster of substrate integrated waveguide (SIW) -fed CP source radiators with an anisotropic impedance surface (AIS) superstrate

A conformal circularly polarized (CP) series-fed microstrip array design for broadside radiation is presented. The array aperture under design is conformal to a cylindrical surface of a given radius. The approach we present primarily addresses focusing of the CP major lobe of the conformal array by proper dimensioning of the aperture spacings. The proposed analytical models yield the values of the

A compact beam-scanning flat antenna array with high gain based on the substrate- integrated waveguide (SIW) is presented in this article. The radiation elements are the continuous transverse stub (CTS) constructed by SIW, which are arrayed on the substrate. The SIW-CTS array has a 4 dB higher gain than the traditional CTS array with the metal parallel plate waveguide and the theoretical explanation

We present a novel antenna based on 2 bit digital coding metasurface and perform convolution operations on the coding antenna to manipulate the radiation waves. Different from the conventional array antennas, we propose to use the metasurface to change the radiation phase of elementary antenna (EA) in a more modular and simpler manner. The radiation beams can be arbitrarily controlled by designing

Millimeter-wave communications require multibeam beamforming to utilize wireless channels that suffer from obstructions, path loss, and multipath effects. Digital multibeam beamforming has maximum degrees of freedom compared to analog-phased arrays. However, circuit complexity and power consumption are important constraints for digital multibeam systems. A low-complexity digital computing architecture

A novel and generalized methodology of mode conversion based on the transmissive metasurfaces is studied in this article. The mathematic formulations, the design criterions, and procedures have been presented in detail. To further demonstrate the proposed methodology, four typical examples are designed. Subsequently, a prototype with the input mode of circular waveguide TM 0,1 mode is designed, fabricated

The ray-series (RS) method, which is practically more tractable and feasible than the transfer matrix (TM) method for the time-domain analysis, is examined and applied for investigation of temporal reflection and transmission responses of an $N$ -layer structure for a plane wave incidence. These responses are represented by reduced reflection and transmission coefficients associated with unit step

Issues in modal tracking in the presence of crossings and crossing avoidances between eigenvalue traces are solved via the theory of point groups. The von Neumann–Wigner theorem is used as a key factor in predictively determining mode behavior over arbitrary frequency ranges. The implementation and capabilities of the proposed procedure are demonstrated using characteristic mode decomposition as a

The pulsed EM-field signal transfer between two co-planar small-loop antennas located on a half-space with dielectric and conductive properties is analyzed analytically with the help of the Cagniard–DeHoop technique and the Schouten–Van der Pol theorem. The analysis yields a closed-form time-domain expression for the open-circuit voltage induced across the ports of the receiving antenna. Limiting cases

Hydraulic fracturing is critical for unconventional oil and gas production. Recently, galvanic methods, including borehole-to-surface and surface-to-borehole electromagnetic methods, have been applied in hydraulic fracture evaluation. However, conventional computational electromagnetic methods require huge computational cost to simulate the common galvanic fracture model, which consists of a long cased

In many applications, electromagnetic scattering from inhomogeneous objects embedded in multiple layers needs to be simulated numerically. The straightforward solution by the method of moments (MoM) for the volume integral equation method is computationally expensive. Due to the shift-invariance and correlation properties of the layered-medium Green’s functions, the stabilized-biconjugate gradient

We propose an automatic, solution based, localized meshing refinement for increasing the accuracy of integral-equation solution for multi-scale electromagnetic problems. The procedure starts with a local measure of the boundary condition error, via testing on zero-order basis functions defined on the finest level mesh. Then, the adaptive mesh refinement (h-refinement) is obtained by nonconformal submeshing

The time domain-electric field integral equation (TD-EFIE) and its differentiated version are widely used to simulate the transient scattering of a time dependent electromagnetic field by a perfect electric conductor (PEC). The time discretization of the TD-EFIE can be achieved by a space-time Galerkin approach or, as it is considered in this contribution, by a convolution quadrature using implicit

The spectral numerical mode-matching (SNMM) method is developed to simulate the 3-D layered multiregion structures. The SNMM method is a semi-analytical solver having the properties of dimensionality reduction to reduce the computational costs; it is especially useful for microwave and optical integrated circuits where fabrication is often done in a layered structure. Furthermore, at some layer interfaces

The use of massive multiple-input multiple-output (MIMO) systems is becoming progressively feasible, as well as progressively important, as the carrier frequency increases. Terahertz (THz) frequencies lead to smaller-sized RF components including antennas, so that even antenna arrays with a large number of antennas have a reasonable form factor while providing large beamforming gain and multi-user

3-D electromagnetic (EM) scattering and inverse scattering of magnetodielectric objects with arbitrary anisotropy embedded in layered uniaxial media are studied. The stabilized biconjugate gradient fast Fourier transform (BCGS-FFT) method is employed to solve the forward scattering problem formulated by the combined field volume integral equation (CFVIE). In the inversion, we use the variational Born

As vector wavefunctions are available to represent incident and scattered fields in an isotropic dielectric-magnetic medium endowed with magnetoelectric gyrotropy, a transition matrix can be conceptualized to relate the scattered field coefficients to the incident field coefficients for scattering by an arbitrary scatterer composed of a linear medium. The elements of the transition matrix must satisfy

The mean radiative temperature ( $T_{mr}$ ) is a key function controlling the sky noise temperature in microwave receiving systems. A generalized parametric prediction (GPP) model of $T_{mr}$ for microwave slant paths in all-weather conditions is formulated and presented. The proposed GPP model is aimed at being multifrequency and surface-temperature scaled, valid for elevation angles from 5° to 90°

Radio atmospherics (sferics for short) are electromagnetic (EM) pulses discharged by lightning return strokes and can be used for D region remote sensing. A frequency-domain full-wave (FDFW) numerical model is developed to simulate sferics propagation in earth ionosphere waveguide (EIWG). For a certain sampling frequency, EM fields of sferics are decomposed into a series of plane waves in the spectral

This article studies both experimentally and numerically the backscattering radar cross section (RCS) and Doppler spectrum characteristics from 2-D linear and nonlinear time-varying sea-like surface at UHF band under low grazing incidence. The small slope approximation and choppy wave model are applied to solve rough surface scattering and generate nonlinear sea waves, respectively. A coherent Doppler

Monitoring the physical parameters from devices inside the body, using ultra wideband (UWB) technology, enables the development of high bandwidth demanding applications in real time. The relative movement of the nodes deployed in the body, due to breathing, can give rise to a frequency shifting effect, increasing the fading level in the propagation channel during transmissions. In this article, therefore

This article presents details about an extensive channel measurement campaign and subsequent statistical channel models for the characterization of 300 GHz channels for wireless rack-to-rack (R2R) and blade-to-blade (B2B) communications in a data center-like environment. Measurements were conducted in various scenarios such as R2R line-of-sight (LoS), R2R obstructed-LoS (OLoS), R2R reflected-non-LoS

We present a variant of a boundary integral equation proposed by M. Herberthson in 2008–2010 for high-frequency plane wave scattering by perfectly conducting obstacles. This integral equation, as some of its predecessors, is entirely dedicated to a single direction of incidence. A significant reduction in the system size can then be obtained by looking for a pseudo-current, which is the actual surface

Wireless power transfer (WPT) plays critical roles in powering deep-tissue implants, which also contributes to several emerging advances for biomedical engineering. To enable a high-power density region in implants, this article presents a method, termed the self-phasing technology, to focus electromagnetic fields from various paths at a deep-tissue spot. By performing the phase-conjugated operation

This article presents a microwave imaging (MWI) algorithm that can incorporate prior structural information, also known as spatial priors (SP), about the object being imaged to enhance the achievable image quantitative accuracy. This algorithm: 1) is fully automated and 2) can work with both complete and partially available structural information. The core idea of this imaging algorithm is to use a

A new method of designing full-wavelength dipoles (FWDs) is presented. A dual-polarized antenna is built based on FWDs for base station applications as an example. The antenna has four FWDs arranged in a square loop array form. The employed FWDs are bent upward to maintain a small aperture size, so that the realized element still fits in traditional base station antenna (BSA) array. The antenna is

A shared-surface dual-band antenna is proposed for 5G operation using characteristic mode analysis (CMA). The surface is the integration of a metasurface at the ${S}$ -band and a partially reflective surface (PRS) at the Ka -band. The resonant mode of the metasurface is excited by a microstrip-fed slot, and the PRS with a pair of substrate-integrated waveguide (SIW)-fed slots are employed to form a

A compact, single-layered substrate-integrated waveguide (SIW) filtenna with parasitic patch is synthesized and designed. A half-mode substrate-integrated rectangular cavity (HMSIRC) is adopted as the first stage resonator to reduce the circuit size. A parasitic patch functioning as the last stage resonator as well as the radiator is arranged closely to the HMSIRC so as to enhance the operational bandwidth

This communication presents a metamaterial (MTM)-loaded compact dual-band circularly polarized antenna system suitable for multiple bio-telemetric applications. The proposed antenna system operates in the industrial, scientific, and medical (ISM) bands with center frequencies: 915 MHz (902–928 MHz) and 2450 MHz (2400–2480 MHz). The integration of an MTM structure with epsilon-very-large property on

A singly fed wideband circularly polarized (CP) substrate-integrated dielectric resonator antenna (SIDRA) is proposed for millimeter-wave (mm-wave) applications. The SIDRA consists of an inner cylindrical dielectric resonator (DR), an outer ring DR, and a substrate-integrated waveguide (SIW) cavity. To generate CP fields, a cross-slot formed by two rectangular slots with different lengths is utilized

This communication presents the design of a compact loop antenna with independent frequency tuning. The proposed antenna consists of a feed line fed by a $50~\Omega $ coaxial probe and four resonating arms on the adjacent sides of the feed line. The two outer resonating arms are directly coupled to the feed line and the other two inner resonating arms are coupled to the outer arms. The proposed antenna

A novel wideband resonant cavity antenna (RCA) with compact partially reflective surface (PRS) is presented, which is composed of a superstrate and a feed antenna. The superstrate is a dielectric slab with double-deck periodic array structure, where the superstratum is composed of square loop cells and substratum is composed of square loop aperture cells. This shows positive reflection coefficient

In this communication, a biotelemetry device for scalp implantation is proposed with an ultraminiaturized and simple-structured implantable antenna that exhibits dual-band characteristics in the industrial, scientific, and medical bands (915 MHz and 2.45 GHz). The proposed system incorporates two batteries and microelectronic components in a total volume of 434.72 mm 3 . The recommended antenna has