This paper presents a novel localization method in multiple-input multiple-output (MIMO) systems based on the implementation of passive repeaters. In addition to their ability to enhance performance in MIMO systems by enriching scattering in line-of-sight MIMO environments, and extending coverage area and accessing blind spots in none line-of-sight MIMO environments, passive repeaters can help in localizing users by taking advantage of their spreading in the communication environments. In the proposed method, the target area is divided into a grid. Each location in this grid has a unique field interference created by repeaters. Because of the unique field interference, each location causes a unique field signature at the base station when a user in that location transmits signals. The field signature corresponding to the center of each grid cell is used as a fingerprint for localizing users in that cell, and for all cells, a bank of matched filters corresponding to all stored fingerprints is constructed. Using only the spatial coherence of the measured fields, there is no need for synchronization between users and the base station. When a signal arrives at the base station, the generated field signature is correlated with the bank of matched filters, and the location is determined based on the maximum correlation value. The numerical analysis is performed to verify the validity of the proposed method, and it is found that by means of passive repeaters, the user location can be determined with no need of calculating additional parameters.

This paper introduces and validates a compact two-dimensional Electromagnetic Bandgap (EBG) structure for the improvement of signal integrity (SI) and power integrity(PI) by suppressing Simultaneous Switching Noise (SSN). SSN bandwidth can be increased by using the proposed T bridge compact planar structure. The proposed structure is simulated using Ansys HFSS Software. Simulated and measured results by Vector Network Analyzer provide 3.13 GHz to 11.40 GHz frequency bandgap with good mitigation of SSN at -30 dB noise suppression reference. It will almost cover S, C, and X bands from electromagnetic frequency spectrum. This will be useful for satellite and terrestrial communication and radar communication applications. The proposed structure analyzes signal integrity issues using eye diagram in MATLAB and power integrity in HFSS with input impedance respectively. The main purpose of this work is to provide a compact structure to improve signal and power integrity by the suppression of power/ground noise. Comparative study is also performed with the proposed structure and reference board with similar dimensions.

This paper presents a proposal for a high birefringμeμnce photonic crystal fiber (C-PCF) with a doped liquid into two first ring holes, which is analyzed by the finite element method. It is demonstrated that the proposed fiber has a birefringence value of about 2.643 × 10^-2 at wavelength λ = 1.55 µm and temperature T = 25˚C. Also, a high chromatic dispersion of -272 ps/nm/km, an effective area of 1.693 µm², and a confinement loss of 0.058 dB/m for the x-polarization method were obtained at the same wavelength and temperature. The temperature influence on the modal properties has also been studied. We will demonstrate through the result that the fiber we propose can be used in both sensing and chromatic dispersion applications such as flattened dispersion fibers.

Breast cancer is, by far, the most diagnosed disease for the death of women worldwide. Researchers are working with an alternative technology to detect the tumours before it reaches the terrible stage because of the numerous limitations in the current imaging approach. This article suggests a promising technique by utilising non-ionizing microwave signal and artificial intelligence especially deep learning algorithms for early detection of breast cancer. This contribution will present a method to detect and classify the tumour category using backscatter signals obtained from antenna simulation in CST microwave studio software. The post-processed scattering parameters are utilized to create image through MATLAB programming environment. The high intensity in the image represents the precise position of tumour. The automatic classification of tumour is achieved by YOLOv5 deep learning model from the created microwave images. A training dataset with fifty image samples are formed by preprocessing and then augmentation is applied to create final dataset with 1000 samples. This approach can identify the location and type of early-stage tumour with size of 5 mm.

This letter presents a wideband polarization reconfigurable antenna based on liquid metal (LM) switches. It consists of single-fed crossed bowtie dipoles, a parasitic element grounded via a metallic post, a dual-cavity-backed reflector and liquid metal switches. The two arms of one dipole are loaded with two symmetrical identical slots, and on top of the slots, two sets of fixed-length movable liquid metal columns filled in polytetrafluoroethylene (PTFE) tubes are attached as switches. The altering between linear polarization (LP) and circular polarization (CP) can be achieved by changing the positions of the liquid metal switches. The dual-cavity structure is applied to obtain unidirectional radiation and enhance the circularly polarized performance. A prototype with overall size of 127 × 127 × 57 mm³ is designed and fabricated. The measured results indicate that the impedance bandwidth (IBM) of the antenna is from 1.06 to 2.46 GHz (79.54%) and the axial ratio bandwidth (ARBW) is from 1.39 to 1.91 GHz (31.52%) for CP state. In addition, the IBW for LP state is from 1.06 to 2.30 GHz (73.81%). Moreover, the peak gains can reach 7.73 dBic in CP state and 9.21 dBi in LP state.

Electromagnetic scattering of a Gaussian beam wave from an array of parallel homogeneous anisotropic circular cylinders is presented. The transmitted fields in the anisotropic cylinders are expressed as an infinite summation of eigen-plane waves with different polar angles. The expression of the Gaussian beam is represented as a product of a well-known scattering of a plane wave and a weighting function. The incident field is expressed in local cylindrical coordinates and the scattered field is the summation of contribution of all cylinders. Using the addition theorem of Hankel function, the expression of the scattered field can be transformed from local coordinates to others. By enforcing the boundary conditions on the surface of each cylinder, an infinite set of equations is obtained which can be written in a matrix form. Scattering cross sections and near fields are analyzed and compared finally.

In this paper, a new space-time adaptive processing (STAP) method based on improved nested arrays and pulses configurations is proposed. Specifically, we first decompose the sensor array into two uniform linear arrays (ULAs) plus a separate sensor, similarly for pulse trains. Then, the original received signals from the physical array and pulse trains are introduced into the virtual domain, where the virtual clutter plus noise covariance matrix (CNCM) estimation is performed. Since the system has more virtual sensors and pulses from the perspective of virtual domain, the degrees of freedom (DOF) capability is effectively enhanced to improve the angle and Doppler resolution of radar. With the spatial-temporal smoothing technique, the STAP filter is designed by reconstructing the CNCM and virtual signal steering vector. Simulation results validate the effectiveness and superiority of the proposed algorithm.

An outer rotor coreless bearingless permanent magnet synchronous generator (ORC-BPMSG) is a multivariable, nonlinear, and strongly coupled system. In order to realize the precise control of the ORC-BPMSG, a decoupling control strategy based on online least squares support vector machine (OLS-SVM) inverse system and internal model controllers is proposed. Firstly, on the basis of introducing its operation principle, the mathematical model is established. Secondly, on the basis of analyzing its reversibility, a real-time inverse system of ORC-BPMSG is obtained by using OLS-SVM, and it is connected in series with the original system to form a pseudo-linear system, which realizes the linearization and decoupling of the ORC-BPMSG. Thirdly, the internal model controller is designed to perform closed-loop control of the pseudo-linear system. Finally, the simulated and experimental results show that the proposed control strategy has better stability and decoupling performance than the decoupling control strategy based on the LS-SVM inverse system and PID (Proportion Integral Derivative).

A compact, gain-enhanced, linearly tapered slot antenna (LTSA) with hook-shaped slots in the ground plane and a combined director, consisting of a metallic strip director and double-sided metamaterial (DS-MTM) loading surrounding it, is proposed for ultra wide band (UWB) applications. Hook-shaped slots are appended in the ground plane for miniaturization, whereas a combination of the metallic strip and DS-MTM loading placed above the LTSA is used for gain enhancement. Performance of the proposed combined director is compared with other commonly used director configurations in the literature, such as single strip director, two strip directors, and two-layers of DS-MTM. It was found that gain enhancement effect of the proposed combined director is the greatest over the UWB band, compared to other director configurations. The fabricated prototype of the proposed antenna operates from 2.83 GHz to 11.31 GHz (119.9%) for a voltage standing wave ratio less than 2 with moderate gain of 3.2-7.5 dBi. The dimensions of the proposed LTSA in terms of the free space wavelength at the lowest frequency (λ₀) are 0.28λ₀ × 0.30λ₀ × 0.0075λ₀ (30 mm × 32 mm × 0.8 mm), which are very compact.

Micro-variation monitoring radar based on the differential interference principle can monitor objects prone to micro deformation. However, it is easily affected by human and environmental factors to cause the radar image to loss coherence in the long-term monitoring work, thus affecting the normal monitoring of radar. Therefore, it is of great significance to study the change detection method of micro-variation monitoring radar images, which can provide reference information and quantitative analysis for monitoring work. In this paper, a method of landslide area identification and detection based on micro-variation radar image is proposed. Based on the radar coherence coefficient image of time series, the difference image is produced by logarithmic ratio cumulation. The difference map is decomposed and denoised by wavelet transform, and then the final difference map is produced by reconstructing the processed wavelet coefficients. Finally, the improved K-means is used to cluster the difference map to get the change detection result image. The actual monitoring data of a mining area is used for variation detection. The results show that the proposed method retains the detailed information of the change area and removes a lot of noise. The difference map is easier to cluster, and the clustering result is more accurate.

A three-dimensional negative index (NI) metamaterial (MTM) is realized at terahertz (THz) frequencies. The structure is comprised of orthogonally oriented cross-bars with arrows on each corner embedded in a dielectric cube. The proposed 3-D MTM is symmetric along all the principal axes and shows a polarization-insensitive, wide-incident-angle negative refractive index regime centered at 0.862 THz with an operational bandwidth of 0.234 THz (27.15{%}). Using staircase approximation, the proposed 3-D NI MTM has been designed into a THz parabolic planoconcave lens (PCL). A PCL made of a NI medium is a counterpart of a positive index planoconvex lens and focuses on the near-field region. The designed PCL shows 3-D focusing functionality for linearly and circularly polarized THz waves at 0.85 THz. The designed PCL has a short focal length and high numerical aperture (NA) with sub-wavelength focusing spot sizes. The computed FWHMs along transversal directions are 0.46λ(x) × 0.49λ(y) for transverse electric (TE) polarized wave, 0.46λ(x) × 0.49λ(y) for left-circularly polarized (LCP) wave and 0.50λ(x) × 0.42λ(y) for right-circularly polarized (RCP) wave, respectively. The corresponding back focal lengths of the realized PCLs are 1.07λ, 1.03λ and 0.98λ and the focal depths are 0.40λ, 0.48λ and 0.41λ for linear, LCP and RCP polarized waves, respectively. A short review of recent progress in manufacturing techniques for the fabrication of the proposed 3-D MTM is further highlighted. Since the proposed 3-D MTM PCL configurations show the far-field focusing of linearly/circularly polarized waves, imaging with high optical power requirements can be met for THz waveband applications.

In this paper, the possibility of synthesizing a linear antenna array for multiple objectives with the thinning approach is demonstrated. The thinning space is constrained to three cases (side, central, and random) parts instead of a fully filled linear array. In the case of the side part, a set of elements located on both edges of the array are removed with the optimized elements close to the center remaining unchanged. As in the case of the central part, only a set of elements close to the center are removed. In the case of a random selection of elements, the cancellation process is carried out randomly within the sides and the center. Since the amplitude weights of the elements located on the edges of the array have a small amplitude excitation, the method of side thinning gives better results than the other two cases. Moreover, in cases of side and random thinning, the last element of each side is excluded from the thinning process to maintain the aperture size. The convex algorithm (CA) is used to perform such thinning optimization. CA optimization efficiently computes a multi-objective function in coordination with the thinned array technique, such as preserving the main beam width in all cases with the reduction of the sidelobe levels, generating one or more nulls, and steering the main beam in a certain direction. The simulation results, in all cases, show that 30%-40% of the array elements can be turned off with achieving a multi-objective radiation pattern.

A multiband fractal monopole antenna has been developed for wireless applications. A triangular monopole antenna is considered for this design to achieve the requirement of WLAN and WiMax. Annular rings are etched out from the basic antenna using the fractal concept. To increase its electrical length, notches are introduced at the edges. The volume of an antenna is 54×57×1.6 mm³. Various changes in the ground plane have been done to get the optimum result. The frequency bands at which the antenna resonates are 3.5 GHz, 5.35 GHz, and 6.1 GHz. These bands are best suitable for the WiMax (3.5 GHz) and wireless local area network (5.35 and 6.1 GHz) applications. The simulated and the experimental results show a good match.

The paper presents a new compact directional antipodal Vivaldi antenna that can be employed in modern imaging applications. To obtain wide-band impedance bandwidth in the proposed antenna, a stair case slot is introduced in both the tapered region along with a triangular ground plane. In addition, by means of introducing a parasitic patch close to the centre of radiators, a more directional radiation characteristic is attained within the operational bandwidth. Based on the simulation results, the antenna designed on FR4 substrate provides a wide impedance bandwidth (S₁₁ < -10 dB) of 6.2 GHz i.e., between (3.8-10 GHz) with a gain between 3.5 to 7.5 dB suitable for variety of imaging applications. The designed single feed antenna is compact, low profile and trimmed to provide a triangular geometry with light weight. To validate the directional radiation performance of the antenna, it is fabricated and integrated with a signal generator and spectrum analyzer to obtain the image of a uniform target object i.e., cylinder using the standard back projection Radon transform algorithm. The proposed setup along with the algorithm are promising for the civil and medical applications on applying to other shapes of objects.

To reduce the loss of a drive motor and improve the output efficiency of the drive motor, this paper explores the influencing factors of core loss of an embedded combined magnetic pole drive motor (ECMPDM) for new energy vehicles. The mathematical model of the core loss of the drive motor is established. The monitoring points are selected in different areas of the stator to analyze the distribution of magnetic density, and the correctness of the model is preliminarily verified. Taking the motor core loss as the primary objective of optimization, the multi-objective optimization of the stator slot structure size is carried out by the response surface analysis method. The average value of the stator core loss and the radial magnetic density amplitude of the B point is taken as the two optimization objectives, and the optimal solution of the model is selected by the Pareto frontier distribution diagram. The optimal stator structure is analyzed, and the core loss value is calculated by three methods and compared with the simulation value. The prototype experiments of the optimized motor are carried out, and the no-load core loss experiment, the rated voltage characteristic experiment, and the peak power characteristic experiment are carried out, which verify the rationality of the optimized size and structure of the embedded combined magnetic pole drive motor for new energy vehicles and provide a possibility for the analysis of the temperature field of the embedded combined magnetic pole drive motor for new energy vehicles.

A copper strip and conductive paint-based low profile stripped helical antenna for circular polarization over wide axial-ratio (AR) bandwidth are presented. Impacts of strip widths and geometric parameters of the helix on antenna performance (impedance bandwidth, reflection coefficient, AR, gain) are analyzed thoroughly. In terms of performance parameters, the proposed design is also compared with traditional designs of wire and strip-based helical antennas. Proper impedance matching in the proposed design is achieved by the non-conformal placement of the strip. For easing the fabrication complexity, the antenna is again simulated with a dielectric-based supportive structure, and the impact of this additional support is discussed. The antenna is then constructed on a 3D printed polylactic acid (PLA) based structure. Finally, the 1.3-turn strip-based helical antenna with a radius of 18 mm provided impedance and 3-dB AR bandwidths of 99% and 82.52%, respectively. The maximum gain of 9.40 dBi was found at 2.05 GHz in 3-dB AR bandwidth. The height of the presented antenna is 0.35 λ₀, where λ₀ is the free space wavelength at the frequency of 2.65 GHz. Low profile and wide AR bandwidth facilitate the use of this antenna in space communication.

A novel compact composite right/left-handed (CRLH) substrate integrated waveguide (SIW) based leaky wave antenna (LWA) is proposed. Mushroom-inspired unit cell is utilized to achieve CRLH transmission property as well as energy leakage. Periodically loaded metallic vias, which act as an internal 1:2 power divider, are along the center line of the SIW structure, leading to a compact antenna size. The LWA can be regarded as an antenna array whose two elements are excited by two newly produced quasi-TE10 modes, respectively, and therefore, the antenna peak gains are enhanced. Good agreements are obtained between the simulated and measured results. Continuous beam scanning feature indicates that the proposed design is a balanced frequency scanning work operating in Ku-band.

A compact extreme wide band (EWB) modified ellipsoid monopole antenna utilising electromagnetic band gap (EBG) technology is developed on a Rogers RT/Duroid 5880 substrate for high frequency millimetre (mm) wave applications including cellular, satellite, radar, and medical imaging. The proposed antenna design has an overall dimension of 40 mm x 30 mm x 0.787 mm and achieves EWB characteristics with a frequency range of 23.16 GHz to 776.59 GHz, a fractional impedance bandwidth (FBW) of 188.41%, and a bandwidth ratio (BR) of 33.53 by using a tapered feed and an EBG technique. The proposed antenna design attained a maximum peak gain of 17.91 dB and a peak radiation efficiency of 99.4%. On the basis of its high impedance wide bandwidth (IBW), FBW, BR, peak gain, and peak radiation efficiency, as well as its omnidirectional radiation properties at resonant frequencies, this compact antenna has the potential to be utilised for EWB applications. The HFSS 3-D solver is applied to characterize and analyse antenna performance.

Optical analog computing has recently sparked growing interest due to the appealing characteristics of low energy consumption, parallel processing, and ultrafast speed, spawning it complementary to conventional electronic computing. As the basic computing unit, optical logic operation plays a pivotal role for integrated photonics. However, the reported optical logic operations are volumetric and single-functional, which considerably hinders the practical cascadability and complex computing requirement. Here, we propose an on-chip combinational optical logic circuit using inverse design. By precisely engineering the scattering matrix of each small-footprint logic gate, all basic optical logic gates (OR, XOR, NOT, AND, XNOR, NAND, and NOR) are realized. On this foundation, we explore the assembly of these basic logic gates for general-purpose combinational logic circuits, including optical half-adder and code converter. Our work provides a path for the development of integrated, miniaturized, and cascadable photonic processor for future optical computing technologies.

Embroidery has been recently introduced as a new method to realize sensors especially for wearables. In this paper, we present a slot-loaded embroidered patch antenna to provide a simplified setup which allows the antenna to act as a stand-alone resonator. The design procedure, simulation and implementation of an embroidered sensor are presented and discussed. It is demonstrated that this structure can be used without any need for external antennas as a wireless sensor. To demonstrate the feasibility of this technique, the design process using a slot-loaded antenna to achieve a high Q antenna, fabricated on an FR4 substrate, is presented and discussed. This structure is then manufactured, with practical results shown to agree with simulated results. Using this as a basis for subsequent designs, an embroidered slot-loaded patch is presented and discussed. We demonstrate this capability in an experiment where a set of solvents inside plastic bottles were interrogated using the embroidered antennas.