This article reports an SDR (software-defined radio) operating as a receiver for near-field measurement, aiming at EMC pre-compliance tests. The SDR replaces professional-grade RF instrumentation with benefits, with the lower costs. Its software application is based on Open-source GNU-Radio, which grants a higher versatility to the signal processing and visualization, requiring a single laptop to analyze the data and control the whole system, in real time. Reported tests used two commercial PCB magnetic field probes, and a proof-of-concept near-field imaging is performed in an S-shaped transmission line at 1100 MHz.

In this paper, a new Surface Wave (SW) diplexer in frequency bands of 11.6 GHz and 19.3 GHz is presented based on the frequency variations of the refractive angle when an SW enters from a Scalar Impedance Sheet (SIS) to a Tensor Impedance Sheet (TIS). In this structure, a SIS has been placed alongside a TIS, and using three launchers, SW is excited and received on them. To achieve an SW diplexer, the structure is designed in a way that the refractive angle changes in the expected range when SW enters from SIS to TIS. Finally, the proposed structure is fabricated and measured by printed circuit technology. The measurement results at 11.6 GHz and 19.3 GHz show that this structure has 3.6 dB and 4.1 dB insertion losses and 33.5 dB and 37 dB isolations in the two bands, respectively. These measurements are in good agreement with mathematical modelling and simulations.

A compact and broadband uniplanar Microstrip Antenna (MSA) is proposed for endfire radiation at sub-6 GHz 5G frequency band. The proposed antenna consists of a semi-elliptical radiating element and a U-shaped ground plane. The use of semi-elliptical radiating element results in a wide impedance bandwidth (BW) and compact size. The U-shaped ground plane further improves the bandwidth due to the increased coupling from radiating element to ground. An endfire radiation pattern, 3.8 dBi peak gain, and 49.8% bandwidth (BW) are achieved while a compact size of 0.47λ₀×0.13λ₀×0.008λ₀ (where λ₀ is the wavelength in free space at the center frequency) is kept. A parametric study based on CST-MWS simulations is also presented together with an equivalent circuit analysis to see the effects of various dimensional parameters of the uniplanar MSA with an elliptical radiating element. To validate the simulation results, prototype of the proposed antenna was fabricated and tested. The measured results are in good agreement with the simulated ones.

Crosstalk between interconnected lines is considered from two perspectives in this study. From a physical space perspective, the four transmission lines are reduced to two transmission lines. Meanwhile, the replacement of signal transmission of four-channels 2PAM (Pulse Amplitude Modulation) with signal transmission of two-channels 4PAM can reduce the quantity of transmission line and increase the space between the transmission lines. Thus, it can reduce the crosstalk. Under the same signal-to-noise ratio (SNR), the change in symbol error rate (SER) after signals of four-channels 2PAM are changed to those of two-channels 4PAM is given. Results show that the latter has an advantage in anti-crosstalk compared with the former in terms of the influence of crosstalk on SER. From the signal space perspective, applying signal linear combination transformation can convert the multiplexing signals in the interconnects into orthogonal mode. This process can cancel the crosstalk. In this study, the two methods are combined to save wiring while reducing crosstalk. ADS simulation results show that the eye pattern of 4 PAM signal recovers well by saving half the number of transmission lines.

A compact substrate integrated folded waveguide (SIFW) H-plane horn antenna array with simultaneous omnidirectional and directional radiation characteristics for potential utilization to high-speed wireless communication is presented in this article. The realization of the proposed design has been accomplished by placing the apertures of nine exponentially tapered SIFW H-plane horns towards the circumference of a cylindrical substrate with an angular separation of 40˚ between the horns. Every horn flaring includes a column of three slots. Centre probe feed technique has been used to excite the antenna. The radiation of the field by the horn apertures and through the slots of the horns flaring, respectively, results in an omnidirectional and a directional radiation pattern at 13.8 GHz and 18.42 GHz, with the gain of 7 dBi and 10.92 dBi. The proposed antenna has performed well and is in good agreement between simulation and measurement. The dimension of the antenna is 37.3 mm (diameter) × 1 mm (height) (1.71₀×0.046₀ at 13.8 GHz and 2.29λ₀×0.061λ₀ at 18.42 GHz). SIFW technology makes low profile antenna. The proposed design can be a promising option to be used as a low-profile antenna for high-speed wireless communication.

An ultra-compact fiber tip Michelson interferometer (MI), primarily aimed for a reproducible and stable high-temperature sensing probe, is developed and demonstrated. Both single-mode fiber (SMF) and polarization maintaining fiber (PMF) are considered and compared. The tip MI is fabricated by only using a one-step partial-polishing technique, which forms a half oblique and half vertical end face and functions as a beam splitter. A wide spectra analysis proved that the interferometer has an optical path difference (OPD) that is consistent across samples. When the lead-in fiber suffers from bending or twisting, the interference spectrum for the PMF case is more stable than that for the SMF case. Experimental results show a linear average temperature sensitivity of 15.15 pm/˚C in the range of 100˚C to 1000˚C for three tested PMF samples, and the difference between the sensitivities of the samples is less than 4.0%. The ease of fabrication, highly compact structure, reproducibility, and excellent resistance to mechanical disturbance performance suggest that the proposed PMF tip MI is highly promising as a high temperature sensing probe with high spatial resolution.

This paper presents analytical and numerical studies of electromagnetic wave propagation through an interface between a regular right-handed material (RHM) and a left-handed metamaterial (LHM). The interface is graded along the direction perpendicular to the boundary plane between the two materials, chosen to be the x-direction. The permittivity ε(ω, x) and permeability μ(ω, x) are chosen to vary according to hyperbolic tangent functions. We show that the field intensities for both TE- and TM-cases satisfy the same differential equations, and we obtain remarkably simple exact analytical solutions to Helmholtz' equations for lossy media. The obtained exact analytical results for the field intensities along the graded RHM-LHM composite are in line with the expected properties of RHM-LHM structures. Finally, we perform a numerical study of the wave propagation over an impedance-matched graded RHM-LHM interface, using the software COMSOL Multiphysics, and obtain an excellent agreement between the numerical simulations and analytical results. The results obtained in the present paper are not limited to any particular application, and are generally useful for all cases of wave propagation over impedance-matched two- and three-dimensional interfaces between RHM and LHM media. The advantage of the present method is that it can model smooth realistic material transitions, while at the same time including the abrupt transition as a limiting case. Furthermore, unlike previously existing solutions, the interface width is included as a parameter in the analytical solutions in a very simple way. This enables the use of the interface width as an additional degree of freedom in the design of practical RHM-LHM interfaces.

A pattern reconfigurable microstrip patch antenna with two parallel parasitic patches placed close to both sides of a rectangular driven patch is investigated and presented in this article. Four switchable shorting posts are used to enable the parasitic elements to act either as a reflector or director for beam reconfiguration, based on the operating state of four associated PIN diode switches. To avoid large change in the dimension of both parasitic patch and ground plane, and minimize its effect on beam steerability and return loss, two PIN diodes are placed on the top face and the other two on the slots etched on the ground plane. Radiation pattern of the proposed antenna can be reconfigured into four distinct directions in the H-plane with radiation maximum at +40˚, 0˚, -40˚ and ±45˚. With overall compact dimension of (35×55) mm² and acceptable return loss for all reconfigurable modes around 6.2 GHz frequency, the proposed antenna is a potential candidate for Wi-Fi 6E application. The measured peak gain varies between 3.9 dBi and 5.2 dBi with an average of 4.6 dBi for all beam tilt angles. Consistency between the simulated and experimental results validates the design theory and its promising application.

A compact and hexagon-shaped microstrip patch antenna operating in three bands is described in this paper. Multiband functionality of the antenna is achieved by adding two inclined strips and cutting modified slots on the radiating patch. The antenna consists of a hexagonal patch and partial ground plane, has the total dimensions of 15×17 ×1.6 mm³, operates over three frequencies 5.40 GHz, 6.76 GHz, and 8.82 GHz for WLAN, TV satellite broadcasting, WiMAX (5250-5850 MHz), IEEE 802.11a (5.47-5.725 GHz), 5G Unlicensed band (5.2-5.7 GHz), weather monitoring, and radar applications. This antenna has the novelty that it can also be used as a reconfigurable antenna, and the notched bands can be controlled. Simulation of the proposed antenna is carried out using HFSS-15 software. To verify the simulated results, and a prototype of the proposed antenna is fabricated. After measurement, simulated and measured results are in good agreement.

In this article, a slot-antenna array with wideband and high-isolation for multiple-input multiple-output (MIMO) systems is presented that can be used in fifth-generation new radio (5G NR) communication. The MIMO antenna system is realized by loading six identical antennas (Ant1-Ant6) into an FR4 substrate to form a six-port array for a 6×6 MIMO system. Each antenna element is a slot antenna type that is composed of a T-shaped open slot and an L-shaped 50 Ω microstrip line. Each T-shaped slot is formed by inserting an I-shaped open branch in the center of the ground plane's U-shaped slot. The L-shaped microstrip line is placed on the upper surface of FR4 to enable coupling feeding in the 3.3 to 5.10 GHz frequency range to cover the 5G NR bands N77/N78/N79. The isolation is increased to more than 18.1 dB by etching the T-shaped slot between the radiation elements on the metal plate. The proposed antenna system was fabricated and tested. The experimental results indicate that the MIMO system can cover the frequency range of 3.20-5.15 GHz with a return loss of 6 dB and provides isolation greater than 16.2 dB. Additionally, a total efficiency greater than 50% and envelope correlation coefficient of less than 0.02 are obtained. The performance under hand-on scenarios is also good. Simulated and measured results indicate that the stated results are consistent. The test results indicate that the antenna satisfies the 5G communication requirements.

This paper presents a triple band proximity fed 2x1 array antenna with defected ground plane. The proposed antenna configuration is composed of two radiating elements, and both radiating elements are made of a pattern similar to the first iteration level David fractal geometry. The proposed David fractal 2x1 array antenna is designed and simulated on an FR-4 substrate of thickness 1.6 mm and dielectric constant 4.3 by using the CST Microwave Studio simulation tool. In order to improve the radiation characteristics of the antenna an H-shaped defect is etched in the ground plane. The antenna is fabricated and tested. The experimental data show good agreements with simulation results. The fabricated triple band fractal 2x1 array antenna resonates at 2.527 GHz, 3.329 GHz and 3.742 GHz having bandwidths of 303 MHz, 99 MHz, and 102 MHz, respectively. The proposed fractal array antenna can be used in mobile applications such as Wi-Fi, WLAN, Bluetooth and Wi-Max.

In this manuscript, a modified spokes wheel shaped two port MIMO (Multi-Input-Multi-Output) antenna with stub loaded ground plane has been presented and experimentally analysed for multiband and EU (European Union) 5900 to 6400 MHz for future 5G mobile terminal applications. The proposed MIMO antenna consists of two radiating patches, and its ground plane is modified to achieve the multiband characteristics as well as enhanced isolation. Initially, a rectangular notch, at the center of ground plane (Ground-1), is employed and reveals four resonant points. Further, the ground plane is modified again by employing two inverted L-shaped stubs along with a series of horizontal rectangular stubs (Ground-2) for enhancing the isolation and reducing the mutual coupling between the elements of proposed MIMO antenna. The antenna with ground-2 exhibits seven frequency bands (S₁₁ ≤ -10 dB) 2.2, 6.0, 7.9, 9.6, 11.1, 12.7, and 15.6 GHz with corresponding isolation (S_12/21) -19.47, -31.22, -34.63, -30.05, -27.16, -39.08, and -22.28 dB. Diversity performance parameters of the proposed MIMO antenna such as ECC, DG, CCL, TARC, and MEG are also in acceptable limits at each operational frequency band. The proposed MIMO antenna is designed and fabricated on a low cost FR4 glass epoxy substrate, and the simulations are carried out by using FEM based Ansys HFSS V13 simulator. Simulated and measured results are compared and found in good agreement with each other.

This article presents a new Butler matrix made on stacked Printed Circuit Boards (PCBs). The matrix is based on Substrate Integrated Waveguides (SIW) and microstrip lines. Transitions using through metallic vias are designed and optimized for the crossover sections of the matrix. The other components of the circuit are as follows: 3-dB SIW directional coupler, 45° phase-shifter, and SIW dual-slot linear antenna array. Different sections of the matrix were simulated, fabricated, and tested. Using the full structure with radiating elements, we obtained good numerical and experimental results in terms of radiations patterns for the different beam directions, impedance matching, and isolation between the input ports.

This paper presents the design of a novel aperture coupled cylindrical dielectric resonator antenna with linear polarization and circular polarization. The linearly polarized cylindrical dielectric resonator antenna (LP CDRA) with proposed aperture and microstrip feed line excites three hybrid radiating modes (HEM₁₁₁, HEM_21δ and HEM_13δ) in three impedance bands. The circularly polarized cylindrical dielectric resonator antenna (CP CDRA) with proposed aperture and flag shaped feed line excites six different hybrid radiation modes (HEM_11δ, HEM_21δ−like, HEM_21δ, HEM_12δ, HEM_13δ, HEM_14δ) in three impedance band and three CP bands. Different sense of CP is reported. The antennas operate in both C and X bands.

In this paper, a dual-model based adaptive sampling method is proposed for the fast calculation of broadband electromagnetic scattering. The difference between the rational function model (RFM) and cubic-spline (CS) based polynomial model issued to generate new frequency samples adaptively. Then, the cubic Hermite interpolation is used to approximate the final broadband RCS curve. The radar cross section (RCS) at each frequency sample is computed by the method of moment (MoM) which is accelerated by the adaptive cross approximation (ACA). Numerical results demonstrate that the proposed method is able to obtain the broadband RCS curve with high accuracy and reduce the computation time significantly. Compared with the method of moment and adaptive cross approximation method, the adaptive algorithm improves the computational efficiency by 77.13% in the sphere case, 83.79% in the rail model and nearly 90.72% in the missile example. In addition, the method proposed in this paper has the characteristics of nonuniform sampling and strong applicability and flexibility, which is able to combine other matrix compressed methods to effectively solve problems in electromagnetic field.

A four-stage switched beam antenna array at millimeter-wave (mm-wave) frequencies is designed, fabricated, and experimental results are demonstrated. A novel rectangular loop dipole antenna (RLDA) applying the quasi Yagi-Uda concept is designed to achieve high gain and wide bandwidth with end-fire radiation. This RLDA with director has a return loss better than 10 dB over a frequency range of 32 GHz to 37 GHz and a peak gain of 8.5 dB. The proposed high gain end-fire RLDA antenna in combination with a 4x4 Butler Matrix(BM) creates the switched beam configuration and generates four beams in the directions of 15˚±2˚, -45˚±4˚, 38˚±2˚, and -15˚±1˚ at 33.5 GHz, 34.5 GHz, and 35.5 GHz with successive input port excitation. The switched beam configuration has overall dimensions at 34.5 GHz is 26 mm x 25.8 mm (3.03λ x 3.0λ).

This paper reports the investigation of a one-dimensional (1D) photonic crystal (PhC) sensor with improved performance for detecting different categories of cancer cells. The sensing region consists of a vertical slot (VS) introduced inside the periodic Bragg mirror. The structure operating principle is based on the change of the refractive index (RI) of the analyte incorporated in the VS, which leads to the shift in the resonant wavelength peak. The sensing properties have been numerically simulated and analyzed using the transfer matrix method (TMM). The study shows that the optimization process of the structure tends to enhance sensitivity. From the result of the numerical simulation, it is found that the final optimized sensor exhibits the higher sensitivity of 3201 nm/RIU than other similar devices. We believe that the obtained results will be valuable for designing highly sensitive PhC sensors.

A novel two-element UWB-MIMO ground antenna is designed by using the theory of characteristic modes. The proposed antenna has a simple and compact coplanar structure, which consists of a rectangular metal ground, a four-stage stepped patch, a double L-shaped patch with a corner cut and a rectangular substrate. By analyzing the most relevant characteristic modes of the metal ground in UWB, the expected characteristic modes are excited by the capacitive coupling elements and the hybrid loading of the capacitive and inductive coupling elements, so as to reduce the size, broaden the bandwidth and improve the isolation. The simulated and measured results show that the proposed antenna obtains ultra-wide impedance bandwidths (2.7-12.6 GHz for Port 1 and 3.0-11.0 GHz for Port 2). Furthermore, the proposed antenna also achieves high gains (3.1-7.3 dBi for Port 1 and 2.7-5.8 dBi for Port 2), stable radiation patterns and good diversity characteristics (the minimum isolation > 16 dB, the envelope correlation coefficient < 0.01, the channel capacity loss < 0.08 bps/Hz, and the total active reflection coefficient < -4.1 dB, etc.) in the whole impedance bandwidth. The research results can provide a useful reference for the design of UWB-MIMO ground antennas based on the theory of characteristic modes.

An aperture coupled printed antenna using frequency selective surface (FSS) reflector is reported in this paper. The proposed antenna includes two layers of FSS reflectors designed with an array of 7×5 crossed elements on the top substrate to achieve wideband, high gain and improved directivity. The antenna implements an aperture coupled radiating element on the bottom substrate which serves as a source feed antenna to the FSS reflector. The proposed structure has an overall dimension of 30×32×1.6 mm³ operating between 6.5 and 8.3 GHz with an impedance bandwidth of 1.8 GHz. The results reveal that the impedance bandwidths in excess of 82.3% and 44.5% have been achieved compared to the source feed antenna and antenna with single layer FSS, respectively. Further, the peak gain of 6.25 dB is also achieved in the operational frequency band with a two-layer FSS which is 29.4% and 15.8% more than the antenna without FSS and antenna with single FSS layer. Due to compact structure, wideband, high gain, and fabrication simplicity, the proposed antenna may be suitable for long distance communication systems.

Wideband designs of proximity fed regular shape microstrip antennas using bow-tie and H-shape ground plane profile are proposed in 1000 MHz frequency range. The modified ground plane alters the quality factor of the patch cavity which enhances the impedance bandwidth. In terms of the results obtained for bandwidth and gain together, circular and square patches backed by bow-tie shape ground plane, followed by circular patch backed by H-shape ground plane yield optimum results. For substrate thickness of 0.097λ_g, against the conventional ground plane, bow-tie shape gives 12% and 24% bandwidth increment for circular and square patches, respectively, and H-shape ground plane yields bandwidth increment by 17% in circular patch. All these wideband designs offer peak gain around 6 dBi with a broadside radiation pattern. Further, modified ground plane profile helps in optimizing the proximity fed antennas on lower substrate thicknesses. Amongst all the configurations, for ~0.03λ_g reduction in the substrate thickness, SMSA using bow-tie shape ground plane yields 19% increase in the impedance bandwidth against the equivalent thicker substrate design with a peak broadside gain of above 6 dBi. Thus, proposed modified ground plane antennas yields bandwidth improvement but for a smaller substrate thickness.