Vol. 98

This paper details the work of the LAPLACE Electromagnetism Research Group to develop an original measuring setup dedicated to the detection of an EMDrive like force. Recent peer-reviewed experimental results [1, 2] were obtained using similar setups based on a torsion pendulum combined with an optical sensor. These very accurate measurement setups are appropriate for measuring such an extremely weak force. They also appear costly, which may discourage other research teams from working on this topic. Our main goal is then to provide an alternative configuration, based on a commercial precision balance, in order to build a measuring setup more affordable, handy, and accurate enough to measure an EMDrive like force. Our experimental system is capable of feeding a truncated cone shaped 2.45 GHz resonant cavity with power up to 140 W. To calibrate the EMDrive force and avoid false positive thrusts, an original setup has been proposed and evaluated. It allows us to really consider that the parasitic effects do not alter the hypothetical force measurement by the use of force direction switching during the measurement.

High resolution wide swath (HRWS) imaging and ground moving target indication (GMTI) are similar in terms of system architecture and are based on a multi-channel system in the azimuth direction. However, in order to achieve their respective performance requirements, the HRWS SAR requires a lower pulse repetition frequency (PRF), and the GMTI system requires a relatively higher PRF. In consideration of this contradiction, the parameters of the moving target are introduced into the reconstructed filtering vector constructed by each signal reconstruction algorithm, so that the HRWS imaging of the moving target can be realized. In this paper, considering the characteristics of the Relax algorithm, a motion-adapted signal reconstruction algorithm is proposed, and the iterative process of the new method is described in detail. This method can perform GMTI on moving targets with a lower PRF without changing the PRF of the HRWS SAR system. By the simulation of point target echo, and comparing with the traditional signal reconstruction algorithms, the reliability and effectiveness of the new method are verified.

Today, worldwide more than five billion of wireless devices are directly communicating for voice and data transmission. The amount of data utilization has increased remarkably and here comes 5G technology with more prominent features, offering high data rate, low latency rate, efficient EM spectrum utilization, an immense machine-2-machine communication, etc. The efficient implementation of 5G technologies requires efficient and compact antennas. This work presents a novel multiband rectangular dielectric resonator antenna for future 5G wireless communication system, having stacked radiator with semi-circular slots etched on the left and right sides of an upper radiator. Additionally, a semi-elliptical slots rectangular microstrip patch antenna of the same dimensions for the purpose of comparison is designed. 28 and 38 GHz, which are the proposed 5G bands by most researchers, are the core target of this work. Alumina with a high relative permittivity of 9.8 is used as a radiator in the design of DRA, while common in the design of both proposed antennas, Rogers RT/DUROID 5880 with a relative permittivity of 2.2 having standard thickness is used as substrate material. Both the proposed antennas have an overall same size of 13 x 11.25 mm². The proposed dielectric antenna resonates at 25.4, 34.6, and 38 GHz with a 7.34, 4.04 and 3.30 GHz of wide impedance bandwidth covering the targeted 5G, 28 and 38 GHz bands, having a good return loss of -34.7, -31.8 and -33.5 dB, respectively. Further, the proposed dielectric antenna has a maximum radiation efficiency of 97.63%, with overall radiation efficiency greater than 90%, and maximum gain of 7.6 dBi is also noted. On the other hand, the proposed microstrip antenna resonates at 28 and 38 GHz with a 1.49 and 1.01 GHz of moderate impedance bandwidth, having -23.6 and -27.1 dB of satisfactory return loss. Further, the proposed patch antenna has a maximum radiation efficiency of 90.33% at 28 GHz, with overall radiation efficiency of greater than 84%, and moderate gain of 5.45 dBi is also noted. Both the proposed antennas have a nearly omnidirectional radiation pattern at resonance frequencies, with VSWR less than 2. Comparative study of the two proposed antennas regarding radiation efficiency, return loss, gain, data rate and impedance bandwidth evidently shows that performance of DRA over MPA at millimeter wave is very good. The proposed antennasare simulated in CST Microwave studio v18.

We introduce a six-switch integrated ultra wideband (UWB) - frequency reconfigurable system for cognitive radio applications. With respect to the requirements of the cognitive radio, this proposed design incorporates a UWB section for sensing the frequency spectrum, and the same design is frequency reconfigured using switches to get narrow bands for communicating within the spectrum. The proposed design has a compact size of 40 mm x 40 mm x 1.6 mm and is printed on an FR4 substrate with relative permittivity 4.4. The first configuration of switches allows the antenna to have UWB characteristics from 3.10 to 12 GHz and beyond as per simulations and 3.13 to 12 GHz and beyond as per measurements. Configurations II to V cover the ultrawide band from 3.54 to 12 GHz through five narrow bands. Measured results match well with the simulated one. The comparative analysis of the antenna in terms of frequency reconfigurability is also included in this work which proves that the proposed design is an effective candidate for Cognitive Radio applications.

Symmetrically excited meandered microstrip line RF coil elements are widely utilized in multichannel approaches which have been proposed to be integrated in ultra-high field MRI system (i.e., 7T and higher). These elements have demonstrated strong magnetic field in the deep areas in the object under imaging. Designing a radio frequency (RF) coil array that employs these elements without decoupling networks might cause non-optimized driving performance of coil array which in turn result in non-clear image. In this paper, two different methods of decoupling have been studied: port decoupling and array elements decoupling. For port decoupling, the coil elements have been designed at Larmor frequency (297.3 MHz) whereas for array elements decoupling, the coil elements have been designed at higher frequencies but matched at Larmor frequency. Port decoupling does not always mean element decoupling. Conventional decoupling methods, such as single capacitor or inductor, face challenges to realize the coil element decoupling for meandered microstrip arrays. An optimized reactive (T-shaped) network is needed in order to achieve element decoupling which in turn prevents distortion of the EM field. All simulation results have been obtained using the CST time domain solver (CST AG, Darmstadt, Germany).

In this paper, the investigation about a metal-insulator-metal (MIM) compound plasmonic waveguide is reported, which possesses the transmission property of plasmon induced transparency (PIT) and exhibits the potential application of refractive index sensing. The waveguide structure consists of an MIM-type bus waveguide, a horizontally placed asymmetric H-type resonator (AHR), and a circular ring resonator (CRR). The AHR is directly coupled with the bus waveguide, whilethe CRR is directly coupled to the AHR, but is indirectly coupled to the bus waveguide. Due to the destructive interference between two different transmission paths, PIT effect can be observed in the transmission spectrum. The finite element method (FEM) is used to study the PIT effect in detail. The results show that the transmission characteristics can be flexibly adjusted by changing the geometric parameters of the structure, and the proposed waveguide structure has potential application prospects in the area of temperature and refractive index sensing with higher sensitivity, better figure of merit, and in the area of slow light photonic devices.

A new structure design of a multi-band suspended stepped slot microstrip patch antenna with copper ground plane for future mobile communications is proposed and presented. A parametric study for the effect on the proposed antenna is done on a par with the integration of a polycrystalline silicon solar cell. The compact low profile proposed antenna is developed using Printed Circuit Board (PCB) technology on a substrate, FR4 with physical size of 50×50 mm². Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for Wi-Max and future mobile communications. The measured result reveals that the presented stepped slot patch antenna with copper ground plane offers impedance bandwidth of 3.94% (covering 5.46 GHz-5.68 GHz band), 3.06% (covering 7.08 GHz-7.3 GHz band), and 9.26% (covering 8.34 GHz-9.15 GHz band). The same radiating patch with solar ground plane offers impedance bandwidth of 4.58% (covering 5.12 GHz-5.36 GHz band) and 3.06% (covering 7.32 GHz-8.02 GHz band) for future mobile communications. Good VSWR and radiation pattern characteristics are obtained in the frequency band of interest.

In this work we describe a model for the computation of the scalar and vector potentials associated with known electric and magnetic fields, as well as for the inverse problem. The formulation is general, but the applications motivating our study are related to the requirements for advanced modeling of charged particle dynamics in plasma-driven electromagnetic environments. The dependence of the electromagnetic field and its potentials in space and time is assumed to be separable, where the spatial part is connected to established solutions of the static problem, and the temporal part is derived from a phenomenological description based on time-series of measurements. We benchmark our model in the simple problem of a finite current-carrying conductor, for which an analytical solution is feasible, and then present numerical results from simulations of a magnetospheric disturbance in geospace.

There is a large body of literature for electrically-small loop receiving antennas including more recent work in demagnetization effects for magnetic materials which are used for reducing antenna size. Optimal design of loop antennas requires understanding the electromagnetic principles and is limited by the accuracy of predicting the electromagnetic parameters (resistance, inductance, capacitance, effective permeability, sensitivity). We present the design principles for electrically-small loop receiving antennas including recommended formulas, a novel approach to optimal design, and an application example for use in the VLF/LF band (1-100 kHz) for two different ferrite-core loop antennas including the optimum coil parameters. Using a ferrite magnetic core greatly complicates analysis and prediction of resistance, inductance, and sensitivity as a function of frequency due to the dependence on core material properties, core geometry, and wire coil geometry upon the core (capacitance is typically negligibly affected). Experimental results for the two ferrite-core loop antennas and an air-core loop antenna validate the optimal design approach with good overall agreement to theoretical prediction of resistance, inductance, and sensitivity. Discussion and comparison between air-core and ferrite-core designs demonstrate the trade-off between outer diameter, length, and mass vs. sensitivity.

In this paper, a dual notch Ultra Wideband (UWB) monopole antenna with compact dimensions of 37.8×27.1×1.6 mm³ is presented. Octagon patch with defected ground structure is used to attain the wide frequency range of 3.17 GHz-11.61 GHz with ultra-wide impedance bandwidth of 8.33 GHz. The band notch characteristics in WiMAX (3.2 GHz-3.67 GHz) and WLAN (4.32 GHz-5.81 GHz) bands are achieved using inverted pi-slot in the radiating element and a pair of double split ring resonators (DSRRs) on either sides of the feed respectively. Reconfigurability in the bands is obtained by using BAR64-02 pin diodes switching at the appropriate placement in the antenna structure. The proposed antenna exhibits efficiency of 88% in operating and 20% in non-operating frequencies. The proposed antenna is designed, simulated and optimized using HFSS 19 electromagnetic tool. The measured results are tested using combinational analyzer in chamber with antenna measurement setup for validation and found in good matching with simulation.

In this paper, a compact Giuseppe Peano, Cantor Set and Sierpinski Carpet fractals based hybrid fractal Antenna (GCSA) is designed and developed for Industrial, Scientific and Medical (ISM) band applications. The proposed GCSA is a hybrid fractal design which is created by fusing Giuseppe Peano, Cantor set and Sierpinski carpet fractals together. The optimization of the microstrip line feed position is performed by using a Firefly Algorithm (FA). The substrate material employed for proposed GCSA is a low-priced, easily available FR4 epoxy of thickness 1.6 mm. By varying the geometrical dimensions of the radiating patch, a data set of 58 GCSAs is randomly generated for the realization of Artificial Neural Network (ANN) and FA approaches. The designed structure is fabricated and then measured results are evaluated. The proposed GCSA is capable of resonating at 2.4450 GHz with S(1,1) < -10 dB. The measured bandwidth of the operating ISM band is 101 MHz. The quantitative performance of three different ANN types reveals that Feed Forward Back Propagation ANN (FFBPN) shows minimum error in comparison to other two ANN types. The simulated, experimental and optimized results show a good match that specifies the preciseness of the measurement.

In this research, the potential of L-band SAR data is evaluated for tropical peatland forest biomass estimation using polarimetric features and field data. For this, ALOS-2 full polarimetric data are acquired over central Kalimantan, Indonesia. Total 54 sampled plots (20 m x 20 m) were established in the study site; diameter at breast height (DBH) and tree species of every tree were collected in each plot. Locally developed allometric equations were used to convert field data to biomass and plot level biomass, and the upscaling factor was applied to upscale plot level biomass to standard tones per hectare scale. Backscattering coefficient (σ_o) was computed for HH, HV, VH and VV polarization. Similarly, eigen decomposition was performed to extract: entropy (E), alpha (α), and anisotropy (A); also diversity indices were computed. Yamaguchi decomposition was performed to extract scattering behavior of forest in central Kalimantan. All polarimetric parameters were upscaled to one-hectare scale. Field data were divided into training plots (70 percent → 42 plots) and validation plots (30 percent → 12 plots). Nonlinear regression analysis was performed between polarimetric parameters and training plots. Perplexity, Shannon index, entropy, Gini Simpson index, index of qualitative inversion, Reyni entropy (order 2), σ_HV, alpha, σ_VV, and volumetric scattering component were found significantly correlated (ranging R² from 0.67 to 0.49) with the field data. The corresponding nonlinear model was inverted, and biomass maps were computed for the individual model. The resultant biomass maps were validated using validation set of referenced measurements. Perplexity, Shannon index, entropy, Gini Simpson index, index of qualitative inversion, Reyni entropy (order 2), σ_HV, alpha, σ_VV and volumetric scattering exhibited a significant correlation between field biomass and predicted biomass computed using developed model. R² for validation ranges from 0.95 to 0.81 with RMSE ranging from 13.59 Mgha^-1 to 25.63 Mgha^-1. The estimated biomass in study site ranges from 49.31 Mgha^-1 to 290.60 Mgha^-1.

Wide bandwidth and high gain designs of sectoral microstrip antennas gap-coupled with parasitic arc shape patches are proposed. In 1800 MHz frequency band, optimum response with bandwidth of more than 50% and peak gain of 10 dBi is obtained for 30° sectoral angle employing two gap-coupled arc shape patches. Further gap-coupled variations of slot cut single arc shape patch with 60° sectoral patch is presented. This design yields bandwidth of above 930 MHz (~53%) with peak gain of more than 10 dBi. The comparison for the proposed gap-coupled sectoral variations with reported antennas is presented. Proposed gap-coupled sectoral configurations are single layer and thus simple in design and yet offers bandwidth and gain of larger than 50% and 10 dBi, respectively.

In the development of hand gesture based Human to Machine Interface, the Doppler response feature extraction method plays an important role in translating hand gesture of certain information. The Doppler response feature extraction method from hand gesture sign was proposed and designed by combining time and frequency domain analysis. The extraction of the Doppler response features at the time domain is developed by using cross correlation, and the time domain feature is represented by using peak value of cross correlation result and its time shift. The Doppler response feature of frequency domain is extracted by employing a discriminator filter determined by the frequency spectrum observation of Doppler response. The proposed method was employed as a pre-processing for Continuous Wave (CW) radar output signals, which is able to relieve the pattern classification of Doppler response associated with each hand gesture. The simulation and laboratory experiment using HB 100 Doppler radar were performed to investigate the proposed method. The results show that the combination of all three features was capable of differentiating every type of hand gestures movement.

With reference to the mask-constrained power synthesis of shaped beams through fixed-geometry antenna arrays, we elaborate a recently proposed approach and introduce an innovative effective technique. In particular, the proposed formulation, which can take into account mutual coupling and mounting platform effects, relieson a nested optimization where the external global optimization acts on the field's phase shifts over a minimal number of `control points' located into the target region whereas the internal optimization acts instead on excitations. As the internal optimization of the ripple is shown to result in a Convex Programming problem and the external optimization deals with a reduced number of unknowns, a full control of the shaped beam's ripple and sidelobe level is achieved even in the case of arrays having a large size and aimed at generating large-footprint patterns. Examples involving comparisons with benchmark approaches as well as full-wave simulated realistic antennas are provided.

In this paper, a three-port pattern diversity antenna with a Fabry-Perot cavity (FPC) using a partially reflective surface (PRS) for 5.2 GHz Wireless Local Area Network (WLAN) access points is proposed. The topology of three coaxial-fed circular patch antennas provides an initial beam tilt of 15˚. The PRS aperture, at a height of approximately λ/2, is then shaped in such a way for the antenna to radiate at 0˚, +25˚, -25˚, which results in total coverage of 90˚. The antenna system has an impedance bandwidth of 2% ranging from 5.16 GHz-5.25 GHz (90 MHz bandwidth), covering the IEEE 802.11a band, for a gain of 10 dBi throughout the band and across the ports. The shaped PRS structure provides a gain enhancement of 4.5 dB. The mutual coupling between any two ports in the three-port antenna system is less than 17 dB for a port-to-port distance of 0.67λ.

An improved wideband cavity-backed antenna and a planar phased array with wideband wide-angle impedance matching (WAIM) are provided in this paper. A step-shaped cavity is applied in the antenna, so the relative bandwidth of VSWR < 2 can be improved to more than 52% without increasing the cavity profile. Furthermore, a planar phased array constructed by the cavity-backed antenna can work with a wide-angle scanning range of ±60° at both E- and H-planes. Due to the wide-angle scanning range, the impedance matching for the phased array will be unstable in the required wideband. Consequently, the matching layer with metamaterials has been loaded on the phased array. The VSWR is controlled within 2 in E-plane and 3.5 in H-plane during the scanning range of ±60° in wide bandwidth.

We present design and computational simulation of multiband, polarization-independent, and thin frequency-selective structures for microwave frequencies, and their fabrication via a very low-cost inkjet-printing procedure. The structures are constructed by periodically arranging unit cells that consist of U-shaped resonators, while polarization-independency is achieved by applying rotational arrangements. Various configurations are obtained by considering double and single U-shaped resonators, as well as rotational and complementary relationships between the corresponding unit cells on the top and bottom surfaces. We observe that complementary arrangements provide resonances with better quality, particularly by allowing the smaller resonators to operate as desired. Measurements on the fabricated samples demonstrate the feasibility of both effective and very low-cost inkjet-printed frequency-selective structures with multiband and polarization-independent characteristics.

For direct suspension force control (DSFC) strategy of Bearingless Brushless DC Motor (BBLDCM), combined with super-twisting algorithm, a second-order sliding mode (SOSM) controller is designed by direct suspension force. The control precision, robustness, and jitter suppression of the suspension subsystem are improved. The direct suspension force control based on the second-order sliding mode (SOSM-DSFC) controller solves the influence of external disturbance on the self-stabilizing suspension, effectively suppresses the rotor jitter problem, and improves the robustness of the rotor suspension.

Aparticular challenge encountered in designing massive MIMO systems is how to handle the enormous computational demands and complexity which necessitates developing a new highly efficient and accurate approach. Considering the large antenna array employed in the Base-Station (BS), in this work, we present a new paradigm to significantly reduce the simulation runtime and improve the computational efficiency of the combined rigorous simulations of the antenna array, 3-D channel model, and radiation patterns of the User Equipment (UE). We present an approach for evaluating a closed-loop massive MIMO channel capacity using 3-D beamforming to take advantage of spatial resources. The approach subdivides an M×N array at the BS into columns, rows, rectangular, or square subarrays, each consisting of a sub-group of antenna elements. The coupling is rigorously taken into account within each subarray; however, it is ignored among the subarrays. Results are demonstrated for a dual-polarized microstrip array with 128 ports. We consider simulation runtimes with respect to two different propagation environments and two different Signal-to-Noise-Ratios (SNRs). It is shown that the maximum difference in the closed-loop capacity evaluated using rigorous electromagnetic simulations and our proposed approach is 2.4% using the 2×(8×4) approach for both the 3-D Channel Model in the 3rd Generation Partnership Project (3GPP/3D) and the 3-D model in the independent and identically distributed (i.i.d/3D) model with a 46% reductional in computational resources compared with the full-wave antenna array modeling approach.