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.

This work proposes a novel probe-fed circular patch antenna which has been fractaled and reconfigured to deliver enhanced performance. The circular ground plane is made defected using Cantor-square fractal geometry which reduces the cross-polarization level by about 12 dB. Further, by appropriate positioning of a PIN diode switch in the ground slot, the fractal Circular Microstrip Patch Antenna (CMPA) is enabled to achieve frequency reconfiguration. A prototype of the proposed antenna is fabricated and tested for the assessment of various parameters. The proposed fractal reconfigurable antenna has a peak gain well above 6 dB, high radiation efficiency, and a maximum bandwidth of about 700 MHz in the X-band (8-12 GHz). The present work aims to focus on the huge potential of fractal reconfigurable antennas in modern dynamic wireless communication systems.

This paper proposes a conformal multiple band four port MIMO antenna for next generation vehicular communications in the extended UWB. The single element consists of a monopole antenna resembling a U-shaped structure with two branches folded and complimentary to each other. It uses coplanar waveguide feeding with a defected ground structure. The antenna is printed on a Kapton Polyamide flexible substrate having a thickness of 0.25 mm. The antenna has dimensions of 0.8λ x 0.8λ x 0.001λ. It resonates at 2.6 GHz, 3.9 GHz and 5.6 GHz which are used in vehicular communications, and can be used in sub-6 GHz 5G applications. It also provides band notches at 2.1 GHz, 3.5 GHz and 4.5 GHz which enables it to mitigate the interferences from any narrow band devices operating in that range. All MIMO parameters are simulated and compared with the measured results, and are found to be in good agreement. The designed antenna can be mounted at any position of the vehicle as it has a conformal structure.

The C-band RDRA with a defective ground structure operated at resonant frequency 6.2 GHz is best suitable for satellite uplink applications. In the C-band, the broad aperture slot and pentagonal-shaped defective ground structure (DGS) offer excellent isolation and great efficiency. The simple prototype of designed pentagonal DGS RDRA is fabricated, tested, and validated. The proposed C-band RDRA has a fractional bandwidth of 12.14%, a return loss of -30 dB, a gain of up to 7.95 dB, and a minimal VSWR at the resonance frequency of 6.2 GHz. It offers a broad beamwidth of 110.87˚ in the E-plane, 43.73˚ in the H-plane, and 91.5% efficiency.

Nanostructure based perovskite solar cell with high performance is the emphasis of study in current work keeping in view the improvement in cell efficiency. In the first part of the study, a plane-layered solar cell is studied by adding a 1D photonic crystal at the bottom of the cell in order to facilitate the photon rotation process. However, in the second part of the study, it is observed that addition of grating enhances the light absorption due to photons trapping. Following that, the light absorption of three different structures is compared. The observations reveal that short-circuit current density (Jsc) is found to be -39.93 mA/cm², which is 87.29% higher than that for a planar structure exhibiting the Jsc value as -21.32 mA/cm². Ultimately, the efficiencies of these perovskite solar cells based on nanostructures are observed to be significant as well. For the proposed solar cell structure, an 87.24% improvement in the power conversion efficiency (PCE) is observed i.e., from 14.03% for the planar structure to 26.27%.

An ultra-wide band (UWB) antenna with C-band and X-band notches for wireless communication is presented. The designed structure is printed on a material of ``Rogers 4350B'' with ε_r = 3.66, tanδ = 0.0037 and a thickness of 0.508 mm. This structure is designed to operate at a UWB range starting from 3.3 GHz up to 10.15 GHz with a stopband range from 6.75 GHz to 8.5 GHz. The rejected bands are the upper C-band (6.75 GHz-8 GHz) and the uplink X-band of the satellite (space to earth) from 7.25 GHz to 7.75 GHz. The overall antenna size is optimized, and its dimensions are 21 × 30 × 0.508 mm³. The antenna gain varies from 2.1 to 4.2 dBi at the passband, and its total radiation efficiency is 96.4%. The suggested structure is designed and simulated using CSTMWS software. Moreover, a prototype of the proposed structure is fabricated and measured. The fabrication process was done using photolithography techniques, and the measurements were done using an R&S vector network analyzer. Good agreement is achieved between the simulated and measured results.

For the sake of decoupling the six-pole radial active magnetic bearing (AMB) with mutual coupling of two degrees of freedom, nonlinear and unstable disturbance, a hybrid active disturbance rejection control strategy based on improved genetic algorithm (HADRC-IGA) is proposed. Firstly, the configuration, magnetic circuit and suspension force model of the six-pole radial AMB are explained and established. Secondly, the HADRC-IGA is designed which is improved on the linear active disturbance rejection control (LADRC). Thirdly, the simulation is carried out, which shows that the capacity of resisting disturbance and the decoupling efficiency of two degrees of freedom of the HADRC-IGA are better than that of conventional LADRC. Finally, the experimental platform is constructed, and the experiments are conducted, which verify the performance of the proposed decoupled control system.

A comprehensive overview of dielectric resonator antenna (DRA) is presented in this paper. Several techniques have been reported in the literature for the performance improvement of DRA. Over the past few decades, circularly polarized (CP) DRAs have been widely explored to mitigate multipath fading and polarization losses in comparison to linearly polarized (LP) antennas. Apart from this, high data transfer rate is required, which needs the development in the field of multi-input-multi-output (MIMO) antenna designs. This includes the increase in the channel capacity without exploiting the limited constraints like signal power and bandwidth. Thus, exploring the concept of MIMO in DRA along with the diversity performance features leads to the development in this field. Furthermore, to mitigate the conduction losses at THz and optical frequencies, high-efficiency DRA proves rationale in extending towards the higher frequency ranges. These scintillating features pave the path for efficient devices integration and on-chip applications at higher frequency ranges where the performance of metallic radiator degrades. Also, the dispersive properties of metal conductivity lead to plasmonic behaviour resulting in the dissipation losses at the optical frequencies. These losses can be substantially mitigated using DRAs. This can be efficiently realized for the future application that requires the manipulation of high-resolution light.

This work proposes and experimentally evaluates a single layer bandpass frequency selective surface (FSS) that resonates at X-band (8-12 GHz). The metal plate of the unit cell has a half-Jerusalem cross slot of size 0.15λ₀, where λ₀ is the wavelength corresponding to 10 GHz centre frequency. The effects of unit cell parameters on filter response are analyzed through parametric analysis. The results reveal that the proposed bandpass FSS exhibits good polarization stability and angular stability at oblique angles up to 45˚. Furthermore, negligible frequency deviations in both TE and TM polarizations have also been achieved using this structure. A prototype of the bandpass FSS was fabricated on an FR4 substrate to validate the proposed design which includes 10×10 elements in a dimension of 45 mm × 45 mm × 1.6 mm. Measurements show that the bandpass FSS has a fractional bandwidth of 40% centered at 10 GHz from 8 GHz to 12 GHz. The unique feature of the proposed filter is its ability to operate in the whole X band (8-12 GHz) by tuning the filter elements.

Microwave imaging of small scatterers is an inverse scattering problem, and recently, the MUSIC algorithm has been proposed to solve this type of problem. The MUSIC algorithm, by assuming that the number of targets is a priori known, can locate the scatterers from the peaks of the well-known pseudospectrum. The noise and multiple scattering create ambiguity to detect the number of targets. Usually, information-based algorithms such as Akaike information criterion (AIC) and minimum description length (MDL) are employed for source number estimation. However, in the cases of low signal-to-noise ratio (SNR) and close targets, the performance of these methods is seriously degraded. In the present work, we propose a two-step approach to enumerate the scatterers in microwave imaging applications for cases where traditional methods fail. Firstly, the MUSIC algorithm is applied to locate all possible targets by assuming the maximum number of targets, and secondly, we can discriminate between the real and unreal targets by using a novel formula that acts as a spatial filter. The efficiency of the proposed method has been examined through various simulation tests using numerical and experimental datasets, and the results verify that the method can accurately specify the location and the number of scatterers in 2D microwave imaging applications.