Full-wave Analysis Research Articles

An Analytical Approach for the Estimation of the Far-Field Reduction Obtained by Placing Closed Conductor Loops in Proximity to a Chip

A recent study proposed a technique to mitigate the far-field emission and susceptibility of printed circuit boards (PCBs) with the use of a suspended metal loop. This article provides, with the help of the small-loop theory, a methodology to analytically predict and further estimate the electromagnetic field (EMF) distribution and level at very large distances from the emitting PCB (as is the case for CISPR radiated emission measurements up to 10 m test distances), where full-wave simulations and experiments are very challenging (if not impossible as a practical matter). The suitability of the methodology was assessed for various radiator size and frequency as well as the loop radius and configuration with respect to the emitting PCB. As proof-of-concept, full-wave simulations and measurements have been performed. The root-mean-squared error (RMSE) was considered as the measure of the accuracy between the analytical and full-wave numerical results. It has been demonstrated that, whatever the loop radius and/or position with respect to the radiating integrated circuit (IC), the proposed methodology can approximate the far-field EMFs with low RMSE values. Moreover, as far as the emitting IC is concerned, independently of its size and radiating frequency (except near the loop resonance), a good precision was achieved with the analytical model compared to the full-wave numerical analysis. Furthermore, the approach was found to be effective not only on-axis but also off-axis of the suspended conductor loop. Apart from the required computational power for full-wave simulations, thanks to the proposed methodology, it is possible to significantly reduce the huge difference in computational time for numerical ( $\gg$ 30 min, depending on the distance) and analytical ( $ few seconds, independently of distance) analyses.

A Hybrid FDTD–SPICE Method for Predicting the Coupling Response of Wireless Communication System

This article presents a hybrid finite-difference time-domain–simulation program with integrated circuit emphasis (FDTD–SPICE) method for analyzing the system-level coupling responses of the wireless communication system with antenna, metallic enclosures, braided shielded cable, and lumped element, when illuminated by an external electromagnetic pulse (EMP). In the hybrid method, a system-level SPICE model combining antenna and braided coaxial cable is proposed to predict the coupling effects including front-door and back-door couplings. FDTD is used to calculate the induced current on the outer conductor of the coaxial cable, which is then incorporated into the system-level SPICE model as an additional current source. Because the hybrid method avoids meshing the antenna and cable, it has higher computational efficiency than full-wave analysis. A typical microstrip antenna system is selected as a case to demonstrate the accuracy and effectiveness of this proposed method by comparing the numerical results with those obtained by CST. Then, considering the influence of the incident conditions of external EMP, the coupling voltages of the microstrip antenna system are calculated. Furthermore, a typical filter circuit is analyzed to illustrate the practicability of the proposed method. The obtained coupling response information demonstrate that the proposed method is available for designing electromagnetic protection of the inner circuits of the wireless communication system against the impact of external incident wave.

Co-Design and Validation Approach for Beam-Steerable Phased Arrays of Active Antenna Elements With Integrated Power Amplifiers

An approach for designing a beam-steering active phased array of antenna elements with integrated power amplifiers (PAs) is presented. It is based on an amplifying active integrated unit cell (AiUC) concept, where the AiUC comprises a radiating slot element, a GaN high-electron-mobility transistor (HEMT), its input matching, and dc biasing/feeding circuitry. The HEMT is embedded in the antenna element, being directly impedance-matched to HEMT’s drain output, i.e., without using any intermediate and potentially lossy impedance matching network. The proposed co-design approach involves a full-wave analysis of the AiUC passive part (naturally including elements mutual coupling effects) along with the subsequent full-system harmonic balance simulations. Furthermore, we extend the standard definition of the scan element pattern (SEP) to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">active</i> SEP (ASEP) that accounts for nonlinear effects of PAs on the AiUC performance. We show that the ASEP is, in general, power-dependent and has a different shape compared with the SEP. The proposed approach has been demonstrated for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band AiUC design example. It was verified through an active waveguide simulator, which is equivalent to the 23.7° H-plane beam-steering case. Measurements are in good agreement with simulations, revealing AiUC 47% peak drain efficiency and 33 dBm maximum radiated power. The predicted scan range is ±60° and ±37° in the E- and H-planes, respectively.

Antenna array design on flexible substrate for wireless power transfer

PurposeIn this work, a microstrip antenna array for wireless power transfer (WPT) application is reported. The proposed 4 × 4 antenna array operating at 16 GHz is designed using a flexible Kapton polyimide substrate for a far-field charging unit (FFCU).Design/methodology/approachThe proposed antenna is designed using the transmission line model on a flexible Kapton polyimide substrate. The finite element method (FEM) is used to perform the full-wave electromagnetic analysis of the proposed design.FindingsThe antenna offers −10 dB bandwidth of 240 MHz with beam width and broadside gain found to be 29.4° and 16.38 dB, respectively. Also, a very low cross-polarization level of −34.23 dB is achieved with a radiation efficiency of 36.67%. The array is capable of scanning −15° to +15° in both the elevation and azimuth planes.Originality/valueThe radiation characteristics achieved suggest that the flexible substrate antenna is suitable for wireless charging purposes.

Full-Wave Leaky-Wave Analysis of 1-D Periodic Corrugated Metal Surface Antennas

A full-wave leaky-wave analysis of 1-D periodically corrugated metallic surfaces with wide gaps is presented. Such wide gaps, in the order of half-wavelength, are employed in the most cited designs for corrugated metallic antenna implementation due to the high attainable gain performance. A full-wave periodic unit cell method is described and implemented on a corrugated metal surface design for the first time. The results are compared with the known matrix pencil method. The complex dispersion characteristics verify that these structures operate as leaky-wave antennas. The calculated wavenumber of the leaky mode is then used for the analytical calculation of the radiation patterns of a finite-size antenna, based on a simple array factor approach and a near-field inspection of the electric fields of the simulated unit cell. The calculated patterns are compared to those obtained from a commercial simulation software (CST Microwave Studio), exhibiting a very good agreement.

Three-dimensional full-wave transient analysis of switches and faults using a method of moments solution of the electric field integral equation

Three-dimensional full-wave electromagnetic transient (EMT) analysis of switches and faults is shown to be possible in the time domain (TD) from numerical solutions of Maxwell's equations in the frequency domain (FD). The electric field integral equation is solved by the method of moments for the initial fault or switch condition (open/closed). The problem is then cast into subsequent FD problems based on the principle of superposition. At each stage, the FD solution is converted into TD and modified by appropriate functions selected to enforce the desired switch operation (closing/opening) in the next stage. This is also applicable to applying and clearing faults at desired times. In order to navigate between the TD and FD solutions, the fast Fourier transforms are applied and a systematic procedure for obtaining a numerically convergent solution is introduced. For slow transients, results exhibit excellent agreement with simulations obtained from an EMT-type program. However, when faster transients are considered (e.g. in gas-insulated substations), the proposed method is shown to provide more realistic results than those computed by the conventional EMT simulations.

1‐D reconfigurable graphene‐strips leaky‐wave antenna with different feeders for wide scanning angles

This paper introduces electronic-beam switching graphene-strips leaky-wave antenna (GS-LWA) for THz wireless communications with different feeding structures. The antenna is constructed from graphene-strips printed on silicon oxide substrate with total dimensions of 1350 × 300 × 35 μm3. The graphene tunable conductivity is used to control the GSLWA radiated beam direction without changing its physical structure. A scanning range of 94° (from −68° to 26°) is achieved at 2 THz using different codes. The effect of different plane wave launchers on the radiation characteristics of GS-LWA is investigated. A planar substrate integrated waveguide horn antenna as a plane wave launcher is designed. It introduces a peak gain of 18.2 dBi with a bandwidth of 21.95% and SLL of 10.6 dB. End-fire radiation from parabolic reflector is employed to launch plane-wave in the GS-LWA. A matching BW of 0.82 THz is achieved with peak gain of 18 dBi. A coplanar fed Yagi-Uda like structure element is studied using a single element and two elements array. The two elements array provided the highest matching of −40 dB over BW of 6% and gain of 16.5 dBi. Finally, tapered microstrip line is investigated. It introduced the lowest SLL −16.1 dB with a gain of 17.5 dBi and BW of 39.57% (from 1.5 to 2.24 THz). The selection of proper feeding structure depends on the required matching BW, peak radiated gain, and the lowest SLL. Full-wave analysis of the GS-LWA launched by different feeding methods is introduced.

High-Gain Conical-Beam Planar Antenna for Millimeter-Wave Drone Applications

In this communication, a high-gain planar antenna with a conical beam (CB) is presented for millimeter-wave drone applications. The proposed antenna comprises a vertical monopole and a circular side reflectors. The high-gain CB is achieved by in-phase reflections from the planar annular-distributed side reflectors which is realized by a series of via walls using the printed-circuit-board (PCB) fabrication. The proposed structure was numerically and experimentally demonstrated. Full-wave analysis shows a 10 dB impedance bandwidth (BW) of 26.50–29.96 GHz, corresponding to 12.26% of the fractional BW, whereas the measured data account for 11.6% in the frequency range of 26.63–29.91 GHz. Meanwhile, a maximum peak gain of 8.51 dBi is observed at a beam-pointing angle of 22°, with a high radiation efficiency of 88.3%. Owing to these valuable features of high gain, good CB radiation performance, and simple planar structure, the proposed antenna is a promising candidate for millimeter-wave drone applications.

A Phased Array Antenna with New Elements Designed Using Source Transformations

Transformation electromagnetics/optics (TE/TO) has been shown to be a useful technique in designing electromagnetic devices with very unique properties. Here, the concepts of transformation optics for single elements is extended to an array of “pinwheel” shaped elements for the first time. Through full-wave finite element analysis (FEA), it is shown that a transformed “pinwheel” linear array can be designed to operate identically to a uniformly spaced linear dipole array. Thus, the “pinwheel” antenna array will maintain all the advantages of array processing of a simple dipole antenna array. The proposed method has applications in structurally integrated and conformal phased arrays for wireless communications, radars, and sensing where structural and mechanical constrains do not align with antenna performance.

Design formulas for liquid crystal phase shifter based on microstrip transmission line

Closed-form analytical formulas are presented to calculate a figure of merit (FoM) of a liquid crystal (LC) phase shifter (PS) based on microstrip transmission line (MS TL). New expressions are derived to account for anisotropic loss of LC and loss in the superstrate. Although approximate, the presented framework provides a useful insight into the effect of numerous design parameters of the LC PS, such as geometric dimensions of TL or complex permittivity of LC and the superstrate. Comparison with the full-wave numerical analysis of Maxwell's equations showed good agreement in the calculated effective permittivity, dielectric and conductor losses and the FoM for operating frequencies up to 12 to 15 GHz. Furthermore, reasonable quantitative agreement for the FoM is maintained for geometries of interest even at millimeter wave frequencies, up to 30 GHz.

Shaped-Beam Reflectarray Design by Means of Social Network Optimization (SNO)

In this work, an innovative approach for the design of a shaped-beam reflectarray (RA) is presented. It is based on the use of a novel evolutionary algorithm (EA), named Social Network Optimization (SNO), that presents good capabilities in terms of convergence and reliability, and therefore it is suitable for optimizing a complex problem such as the one of interest. The full-wave analysis of a small–medium configuration designed with the proposed approach and the experimental characterization of a prototype proved the effectiveness of the adopted method.

Millimeter-wave multi-mode circular antenna array for uni-cast multi-cast and OAM communication

This paper investigates uni-/multi-cast and orbital angular momentum (OAM) mode data transmission in orthogonal directions by the utilization of a new circular antenna array, operating at 28 GHz. In the horizontal plane the proposed antenna array operates as multimode transmitter (i.e., it provides broad-, uni- and/or multi-cast communication), while in the vertical direction OAM transmission occurs (i.e., it is capable of generating up to 15 spatially orthogonal OAM modes). Antenna array is designed using twelve, low-complexity, electromagnetically coupled microstrip patch antennas with high radiation efficiency. Each of these can transmit power of equivalent order of magnitude in both horizontal (i.e., broadside radiation pattern) and vertical direction (i.e., endfire radiation pattern) over electromagnetic waves of orthogonal electric components. This property leads to the formation of uni-/multi-cast and OAM modes in the horizontal plane and vertical direction, respectively. Antenna was tested through full-wave electromagnetic analysis and measurements in terms of impedance matching, mutual coupling and radiation pattern: good agreement between simulated and measurement results was observed. Specifically, it presents up to 8.65 dBi and 6.48 dBi realized gain under the uni-cast (in the horizontal plane) and OAM mode (in the vertical plane), respectively. The proposed antenna array is perfect candidate for high spectral efficiency data transmission for 5G and beyond wireless applications, where orthogonality in communication links and OAM multiplexing is a requirement.

Investigation on Electromagnetic Properties of PLA/Carbon/Copper Antennas for Breast Cancer Detection

Breast cancer is the most common cancer of women in the globe. Microwave imaging has low power and longer wavelength signals to receive information about breast tissues and guarantees a safer and more accurate modality for regular breast control. So, the antenna is a crucial element in the microwave imaging system. This study involves analysis of the simulation results of the linear and planar microstrip array antennas in terms of high gain. In the series antenna design stage, the antenna models with high gain and directional radiation are aimed. 1x4 and 2x2 array antenna models are prepared with PLA/Carbon insulating material. Array antennas, three-dimensional full-wave electromagnetic structure analysis are designed using the CST (Computer Simulation Technology) Microwave Studio program. In the design phase, the transmission line losses of the array antennas are tried to be optimized by using T-junction and Wilkinson power divider techniques and impedance matching is realized. Also, the redundant areas in the turns are removed to minimize the undesirable reflections in the transmission line and to reduce the capacitive loading. Since the 1x4 array antenna performs better than the 2x2 array antenna, it was preferred for breast cancer simulation.

Full-Wave Analysis of A Line-Fed Rectangular Patch Antenna Using FDTD Method with Mur's and PML ABCs.(Dept.E)

Full-Wave Analysis of A Line-Fed Rectangular Patch Antenna Using FDTD Method with Mur's and PML ABCs.(Dept.E)

Impact of substrate and bending angle on the performance of microwave PCB sensors for permittivity measurements

A design topology for a microwave planar permittivity sensor focused on manufacturing simplicity is proposed. Its operation is based on the first-notch frequency of the reflection parameter. The impacts of substrate and bending angle on the performance of this type of sensor are comparatively analyzed. Three flexible substrates are considered in comparison to three rigid ones. By full-wave electromagnetic analysis, the sensors have been simulated in contact to a material under test with a relative permittivity ranging between 1 and 20. The resulting shifts in the first-notch frequency show the potential of flexible environmentally-friendly substrates, such as liquid crystal polymer and paper, for the development of the sensors. In the flexible cases, the bending angles have been varied from 0 to 120∘, producing deviations in S11 first-notch frequency of 0.4 to 4.7%. The simulation methodology is validated by experimental characterization of a prototype on Rogers 4003C laminate.

Resonant Frequency and Bandwidth of Superconducting Microstrip Antenna Fed through a Slot Cut into the Ground Plane

In this work, an efficient analysis is presented to accurately predict the resonant frequency and bandwidth of superconducting microstrip antenna fed through a slot cut into the ground plane. The effect of the superconductivity of the rectangular patch is introduced in the Full-wave analysis based on Gorter-Casimir two fluid model together with London brothers equations. In order to check the accuracy of the proposed approach, the obtained results have been compared with theoretical and experimental data reported in the literature. Finally, the influence of the slot on the resonant frequency and half-power bandwidth of the superconducting antenna has been investigated.

A Class of Lightweight Spherical-Axicon Dielectric Lenses for High Gain Wideband Antennas

A class of lightweight spherical-axicon-like dielectric lenses suitable for enhancing broadband antennas performances is presented. The proposed lenses, sized according to a reference massive lens, are formed by thin dielectric sheets spaced equiangularly on the azimuth plane (petal-shaped lens), or regularly orthogonally arranged along the lens axis (disks-shaped lens), thus yielding construction simplicity and significant weight reduction. While petal-shaped dielectric lenses are shown to yield mild gain increase, lenses made by thin dielectric disks, orthogonally periodically arranged along the lens optical axis, offer performances much closer to those achieved by comparable massive refractive spherical-axicon dielectric lenses. The time-domain and the focusing characteristics of the proposed lenses are investigated. Then, a Floquet’s mode-based model is proposed to describe the stop-band characteristics of stacked-disk lenses, illustrating the mechanism underpinning their sudden performance degradation observed at the stop-band onset frequency. Full-wave analyses, based on a locally conformal finite integration technique (FIT), implemented in CST Studio Suite™ and validated by measurements or highly accurate FEM simulations, illustrate the excellent characteristics of the proposed lenses to operate with narrowband as well as ultra-wideband (UWB) waveforms.

The Design and Analysis of Electronically Reconfigurable Liquid Crystal-Based Reflectarray Metasurface for 6G Beamforming, Beamsteering, and Beamsplitting

Reconfigurable intelligent surfaces (RISs) are becoming increasingly popular in the field of wireless communications, given their potential to ameliorate the challenges faced in millimeter-wave wireless communications. Specifically, liquid crystal (LC)-based RISs have demonstrated numerous advantages over other types of RISs in terms of cost, complexity, and radiation efficiency in the high-frequency regime. This paper presents the design, algorithms, implementation routines, and simulation of a novel reconfigurable LC-based reflectarray metasurface operating at 108 GHz. The scanning range of the proposed device is ±40° (azimuthally and horizontally), with an average scanning beamwidth of 8.6°. We present semi-analytical findings on the scalability and phase continuity of our design, showing how key performance indicators (KPIs) are affected by dimension and phase degree-of-freedom changes. We demonstrate agreement between our semi-analytical models and full-wave analysis, focusing on genetic algorithm (GA)-optimized beam manipulations. Our results present a feasible workflow that enables dynamic beamforming, beamsteering, and multibeams at 108 GHz, and is easily scalable for applications in other 6G and beyond frequency spectra.

Design and Experiment of a Quasi-Optical Mode Converter

Quasi-optical mode converter is an important component to realize the high-efficiency output for a high-power gyrotron oscillator. In this paper, design and experiments of a quasi-optical mode converter, consisting of a Denisov-type launcher and three quasi-optical mirrors, are carried out for the development of 140 GHz/TE28,8 mode gyrotron oscillator. Based on scalar diffraction method, the field distribution at the radiation aperture of the Denisov-type launcher is optimized to make the vector correlation of the aperture field with the ideal Gaussian field reach 96.2%. Based on the geometric optics method and the Gaussian beam matching method, the focusing mirror and the beam shaping mirrors were designed. A 3D full-wave analysis software Surf3D was used to obtain the field distribution on each mirror surface and the output window, which shows that the output beam with Gaussian mode content of 96.67% is obtained at the output window. The total power conversion efficiency of the quasi-optical mode converter is 93.98%. The design and experiments of the quasi-optical mode converter are performed to use the output signal of the self-developed TE28,8 mode generator as its input one under the conditions of the simulated demonstration for its conversion characteristics and the strict control for machining precision as well as the process of the converter assemble and testing. The tested results indicate that the design is in good agreement with the experiment, which is helpful for engineering design and experimental demonstration of the quasi-optical mode converter development.

A Nanoplasmonic Branchline Coupler for Subwavelength Wireless Networks

This article presents the new nanoplasmonic branchline coupler (BLC) by using an edge coupled coplanar waveguide (CPW) with a finite length suspended backed conductor. The proposed coupler is designed by using the theoretical transmission line (TL) method, which is established based on the basic characteristics of the related CPW structures. For this purpose, the normalized propagation constant, propagation length, and characteristic impedance of the conductor backed coplanar waveguide (CBCPW) structure are studied and analyzed by applying a fullwave analysis using CAD simulation software tool CST microwave studio suite. Mainly, the coupling coefficient of the BLC can be controlled by changing the length of the backed conductor. In this article, the BLC is designed and analyzed by using a finite length backed conductor based on the theoretical TL method at a 3-dB coupling coefficient. This newly designed coupler can operate at two arbitrary optical frequency bands (O-band and L-band). Hence, it allows us to exchange many other couplers with their narrow bandwidths using this branchline coupler for subwavelength nanoscale wireless network applications and photonic integrated circuits (PICs).