Due to the restriction of the low-resolution systems and the interference of background clutter and environmental noise in the exploration process, the traditional classification and recognition algorithms of conventional radar for aircraft targets have low accuracy and poor feature stability. To solve the above problems, this paper proposes to apply high-order cumulant spectrum and deep convolutional neural network (CNN) to feature the extraction and classification of aircraft target radar echoes. Firstly, analyze the high-order statistical characteristics of aircraft echoes, calculate their bispectra, and then enhance the generated bispectrum dataset. Finally, use the augmented dataset to train and test the deep CNN, and obtain the final classification and recognition results. Experimental results show that the proposed method can accurately classify and identify multiple aircraft targets in the dataset, indicating that the bispectral features can better reflect the target characteristics, and the classification method combined with the deep learning model has good classification and identification performance and noise robustness.

This work introduces a novel compact 4-element MIMO antenna in the form of a q for use in the X-band. The proposed antenna has a footprint of 25 × 25 mm² and can be easily produced using a FR-4 epoxy substrate. The antenna consists of a 50-ohm microstrip line connected to ground and four q-shaped radiators. The antenna's impedance matching characteristics were analysed by performing a parametric study on its several parameters. The antenna has excellent impedance matching capabilities and operates between 7.2 GHz and 12.6 GHz. By utilising the connected ground technique and placing radiating elements in an orthogonal orientation, we can achieve isolation of greater than 15 dB. The measured and simulated results demonstrate the antenna's high peak gain of > 4 dBi and high radiation efficiency of > 90%, as well as its good impedance bandwidth (S₁₁ ≤ 10 dB) and isolation (S₂₁/S₃₁/S₄₁ of ≥ 15 dB). The presented antenna is a good option for X-band applications because its envelope correlation coefficient (ECC) is less than 0.00001, total active reflection coefficient (TARC) less than -10 dB, channel capacity loss (CCL) less than 0.03 bits/sec/Hz, and mean effective gain (MEG) less than -3 dB.

To utilise maximum amount of available optical energy it is necessary to design a solar cell with minimum reflectance from its surface. Broadband anti-reflection coatings are essential elements for improving the photo current generation of photovoltaic modules. The vast majority of antireflection coatings are required for matching an optical element into air. In this work, we choose the substrate of the structure that has an index sufficiently higher than the available thin film materials to enable the design of high performance antireflection coatings. This high index substrate is silicon (Si) of refractive index 3.54 at design wavelength 500 nm. Quarter wavelength optical thicknesses (QWOTs) of films of various dielectrics are coated with refractive indices calculated by ``Root-Principle''. The reflection spectra of visible radiation in normal and oblique incidence with antireflection coatings up to six layers will be analysed to achieve nearly zero reflectance.

We propose an original and detailed investigation of a moving dielectric half-space with oblique plane wave incidence, by using the Finite Difference Time Domain (FDTD) method. In our FDTD program, movements are implemented by changing positions of the interfaces at different time instants, through the classical FDTD time loop. With this ``brute-force'' approach, time is implicitly absolute, and Voigt-Lorentz transformations are not implemented. This technique is suitable for non-relativistic electromagnetic problems with moving bodies, thus for most encountered electromagnetic problems. We analyze the transmitted and reflected waves, for different speeds, different refractive indices, and different incidence angles. Based on the obtained results, we derive several analytical formulas for the reflection coefficients, transmission coefficients, Doppler frequency shifts, and angles of transmission and reflection. These formulas are validated by full-wave electromagnetic simulations and are in agreement with the literature. The electric field distribution obtained at time instants is also studied.

A multi-band microstrip patch antenna consisting of an elliptical shape patch with four triangular-shaped arms mounted on a Rogers AD255C substrate with coaxial feed technique to cover 1720 MHz for 2G, 2120 MHz for 3G, 2372 MHz for 4G, and 3536 MHz for Sub-6 GHz 5G wireless communication applications is proposed in this paper. The antenna is designed by exciting a dominant & its orthogonal as well as higher order TM^z_mn0 modes based on cavity model-circular patch theory and then reshaped to an elliptical shape to get the resonance at desired bands. A Characteristics Mode Analysis (CMA) is used for computing electromagnetic resonance frequencies in conducting bodies. A radiating characteristic of the proposed antenna structure is analyzed and verified using CMA technique for target applications frequencies. The CMA demonstrates that the proposed antenna resonates at 1728 MHz, 2127 MHz, 2358 MHz, and 3436 MHz, making them suitable for use as multi-band antenna for 2G, 3G, 4G, and Sub-6 GHz 5G applications respectively after proper feeding. A simulated bandwidth at -10 dB return loss is 23 MHz (1707-1730 MHz) for 2G, 34  MHz (2104-2138 MHz) for 3G, 18 MHz (2364-2382  MHz) for 4G, and 67 MHz (3499-3566  MHz) for Sub-6 GHz 5G applications. The simulated peak gains are 6.29 dBi, 7.08 dBi, 4.51 dBi & 6.18 dBi which are validated by measured results at the respective resonant frequencies. An overall dimension of the proposed antenna is 100×100×3.175 mm³. The proposed antenna was simulated by CST Studio Suite 2020. Measurement was done for the fabricated antenna which shows good agreement with simulated ones. The proposed multi-band antenna with low complexity & easy design offers a quasi-omnidirectional radiation pattern and performance improvement.

This paper proposes a single feed circularly polarised patch antenna with reactive impedance surface (RIS) and metamaterial superstrate (MS) to improve bandwidth and gain for Wi-Fi and Wi-Max applications that demand high gain, wide band, and directional antennas. In this paper, we demonstrate the performance of several antenna designs, including a slot-loaded patch on a single substrate, an antenna on a dual layer substrate with RIS, and an antenna with RIS and MS. The cavity formed by the superstrate and antenna ground plane functions as a Fabry-Perot resonator (FPR) that enhances bandwidth and gain simultaneously. The final optimised antenna has a significantly wider impedance bandwidth (IBW) of 17.32% (5.01 GHz - 5.96 GHz) and an axial ratio bandwidth (ARBW) of 6.29% (5.23 GHz-5.57 GHz) than the conventional slot loaded patch antenna. The proposed antenna gain is 11.73 dB, which is around 9 dB increase over the gain of a standard antenna.

A compact planar edge ultra-wideband (UWB) antenna is designed to operate at a frequency range of 3.5 GHz to 10.4 GHz for water quality detection. The design was constructed on an FR4 substrate with an overall dimension of 30 × 35× 1.6 mm³. The presented design is used to detect the presence of salt in the water in terms of reflection coefficient (S₁₁). The proposed antenna's performance was examined by increasing the salinity of the three water samples: distilled water, reverse osmosis (RO), and raw water. The results showed the decrease of the S₁₁ with the increment of salt in the water samples. In addition, the antenna showed good sensitivity as the resonance frequency of the antenna shifted to a lower frequency as the dielectric constant of water increased. Hence, the proposed UWB antenna can be prominently suitable for monitoring water quality and sensors.

Photonic crystal fiber sensors could be used for a variety of purposes including food preservation, manufacturing, biomedicine, and environmental monitoring. These sensors work based on the novel and adaptable photonic crystal fiber (PCF) structures, and controlled light propagation for the measurement of amplitude, phase, polarization, the wavelength of the spectrum, and PCF incorporated interferometry techniques. A new design of PCF was presented in this paper, and a hexagonal microstructured fiber structure was designed. The proposed PCF can successfully compensate for the chromatic dispersion by the influence of the pressure. As a result, a PCF pressure sensor was then successfully developed. The pressure sensitivity of this PCF was measured. We developed a simulation to understand the relationship between pressure and dispersion. In this work, all simulations are discussed, and the pressure sensitivity was numerically calculated for three wavelengths 1.1 µm, 1.4 µm and 1.7 µm to be respectively -0.01 (ps/nm/km)/bar, -0.0207737 (ps/nm/km)/bar and -0.0236908 (ps/nm/km)/bar.

The magnetically mediated thermoacoustic imaging with magnetic nanoparticles (MNPs), which is excited by nonuniform pulsed envelope magnetic field, is constructed here, and the results of the magnetic susceptibility distribution of nanoparticles are extracted. In this paper, the theoretical model of the nonuniform magnetic field based on space-time separation is solved, and the Rosensweig model is used to obtain the heat generation of MNPs under the excitation of the pulsed envelope magnetic field. To solve the inverse problem, the heat source distribution is calculated by the time inversion method according to the sound pressure propagation formula under adiabatic conditions. After filtering out the effect of the non-uniform magnetic field, the magnetic susceptibility distribution can be obtained. The reconstruction results from simulation and experiment are consistent with the original distribution of MNPs and the distribution of the magnetic susceptibility. This method is expected to be applied to the precise diagnosis and treatment of tumors and provide a new idea for the precise localization and distribution image reconstruction of nanoparticles in vivo.

A sensorless control method based on active disturbance rejection control (ADRC) and left inverse of fuzzy neural network is proposed to realize the sensorless control of permanent magnet synchronous motor (PMSM) for machine tools. Firstly, on the basis of analyzing the mathematical model of PMSM and the theory of left inverse system, a left inverse system observer is constructed. Secondly, after verifying the left reversibility of the PMSM control system, the fuzzy neural network is used to construct the left inverse system, and the left inverse system is connected with the PMSM control system in series to realize the sensorless control of the PMSM. Thirdly, according to the mathematical model of PMSM and the sensorless speed observation results, an ADRC method to improve the sensorless control effect is proposed. Finally, the experimental platform of the sensorless control method based on ADRC fuzzy neural network left inverse is built. The experimental results show that the method can estimate the speed and position well.

Two novel ultra compact flexible tri-band antennas with coplanar waveguide (CPW) feed and asymmetric coplanar strip (ACS) feed arrangements are presented in this paper. These antennas are fabricated on an extremely thin substrate with dielectric constant (ε_r) 3.5 and loss tangent (tanδ) 0.027. The folded geometry of the antennas contributes to the size reduction. While the CPW fed tri-band antenna (19 mm × 19 mm) exhibits bandwidth of 130 MHz, 600 MHz, and 1550 MHz in the lower, middle and upper frequency bands, the ACS fed tri-band antenna (19.5 mm × 15 mm) exhibits 80 MHz, 600 MHz, and 2220 MHz bandwidth respectively. Design equations are developed, and an appropriate circuit model is recommended. The performance of the antenna is investigated for various bending conditions. Simple geometry, compactness, flexibility, and stability under bending conditions over multiband make these incredibly thin antennas quite appealing for ISM 2.4/5.2 GHz, Wi-Fi 2.4/5 GHz, WLAN 2.4/5.2/5.8 GHz and WiMAX 3.5/5.5 GHz applications.

An end fire antenna architecture based on transmission line (TML) theory is suggested. N element end fire antenna array could be constructed with N-1 elements of full wave dipole antennas and one half wave dipole antenna without additional impedance matching network. The N dipole antennas are placed with each other with a distance of quarter wave length, while the one half wave dipole antenna is at the outer most of the array, the farthest from the feeding point of the antenna array. And three 24 GHz dipole end-fire antenna arrays with gains of 7.1, 8.4 and 9.4 dB respectively are presented to explain and verify this end fire antenna architecture based on transmission line theory. Simulation and measurement results of the three end-fire antennas are given and compared. This 24 GHz end-fire antenna architecture could be utilized in 24 GHz planar end-fire antenna arrays to increase the effective isotropic radiated power (EIRP) of the transmitter.

Quantum-based systems are an emerging topic of research due to their potential for increasing performance in a variety of classical systems. In radar and communication systems, quantum technologies have been explored in an effort to increase the correlation performance in the low signal-to-noise ratio (SNR) regime. While this increase has been shown both mathematically and in the laboratory using bipartite states, systems utilizing multi-partite squeezing and entanglement may lead to an even further performance increase. We investigate this by analyzing the correlation coefficient for a tripartite system electric field measurement to determine how it compares to the bipartite systems in the current literature for the same transmit powers. This is done by defining a tripartite wave function in terms of the mean photon number per mode then determining the covariance matrix from this wave function. This work is important in understanding how alternative states of light can be used for quantum radar applications.

This article presents a textile dual band antenna printed on an artificial heart (AH) bag for various Wireless Body Area Network (WBAN) communications. The textile dual band antenna operates at two different operating frequencies 2.4 GHz and 5 GHz. The two operating frequencies are reserved for IEEE 802.11b/g/n/ax and IEEE 802.11j WLAN standard. The designed antenna has a frequency bandwidth of (2.3642-2.5375 GHz) for the lower frequency of 2.4 GHz and (4.598-5.1683 GHz) for the upper frequency of 5 GHz. The dual band antenna is integrated with the proposed AH bag that is made from textile material. The effects of both different materials and dimensions of the proposed AH bag in the characteristics of the proposed antenna are investigated. The effect of the human body on the electrical performance of the proposed antenna integrated with the AH bag is presented. The amount of electromagnetic absorbed energy through the human body is also determined in terms of the specific absorption rate (SAR). The obtained SAR value is less than 0.12 W/Kg. This value meets the IEEE standards. Experimental verification for antenna integrated with AH bag and human body is presented.

In this work, we have designed and fabricated a non-invasive flexible biosensor with a simple and printable structure for blood glucose monitoring. The proposed sensor has been experimentally proven to monitor blood sugar levels through frequency shifts. A cylindrical design with a coplanar waveguide (CPW) feeding technique has been proposed. A targeted frequency of 2.4 GHz with the best S₁₁ at -22.623 dB and a bandwidth of 323 MHz was obtained. However, after propagating through the finger phantom, the signal is sensitive to the blood glucose levels with a significant frequency shift. The biosensor worked well at 1.55-1.88 GHz, representing a finger, without a phantom in the ISM band of 2.4 GHz. There is a bit of shifted frequency during the biosensor measurement with less than a 1.41% error. The overall size of the biosensor is 50.66 mm x 60.31 mm. The biosensor uses a flexible Dupont Pyralux substrate; thus, the index finger is easy to insert. 25 volunteers were involved in this experimental blood glucose. For this, we use an invasive device to measure the volunteers' blood glucose levels. The invasive measurement results obtained are used as a reference for the blood sugar levels of each sample. The test results using a cylindrical biosensor show a frequency shift at 7.5 MHz for every mg/dl of blood sugar levels, with a sensitivity of 0.43 1/(mg/dL). This frequency shift can be used to observe changes in the concentration of sugar levels in the blood. This flexible sensor is a good alternative biosensor for measuring blood glucose levels due to its low cost and printable structure.

In this paper, the Wiener-Hopf technique is used to analyze the plane wave diffraction rigorously by a semi-infinite parallel-plate waveguide with five-layer material loading for E polarization. Introducing the Fourier transform of the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations satisfied by unknown spectral functions. The Wiener-Hopf equations are solved exactly via the factorization and decomposition procedures leading to exact and approximate solutions. Taking the Fourier inverse of the solution in the transform domain, the scattered field in the real space is explicitly derived. For the region inside the waveguide, the scattered field is expressed in terms of the waveguide TE modes, whereas the field outside the waveguide is evaluated asymptotically with the aid of the saddle point method leading to a far field expression. Numerical examples of the radar cross section (RCS) are presented for various physical parameters and farfield scattering characteristics of the waveguide are discussed in detail.

In this paper, an electronic textile (E-textile) antenna design using machine learning (ML) algorithms such as polynomial regression, k-nearest neighbor (kNN), random forest regression, and deep neural network (DNN) is proposed for achieving the optimized solution. These ML techniques, including DNN, have been implemented on a python framework and support in selecting efficient optimum design parameters for a co-planar waveguide fed textile antenna to attain the maximum impedance bandwidth performance in 3-24 GHz band, respectively. Moreover, the accuracy of the predicted response values obtained by these ML methods has also been validated by verifying with the CST simulation software tool.

An eddy current damper for an optimized rotation magnetized direction (RMD) permanent magnet thrust bearing (PMTB) was analyzed in this paper. Initially, optimization of critical design variables was performed for a particular bearing volume for maximum force as well as stiffness. Then, generalized curve fit equations were established to obtain a correlation between different geometrical parameters concerning the outer diameter and airgap. Furthermore, the axial force of the optimized RMD configuration calculated using mathematical model was validated using the results of FEA in ANSYS. Finally, finite element simulation was performed to evaluate the damping forces generated by an eddy current damper (ECD) for an optimized thrust bearing. Analysis has shown that eddy current dampers can improve system damping.

Wideband designs of a U-slot cut square microstrip antenna using bow-tie and H-shape ground plane profiles are proposed on an electrically thinner substrate. The modified ground plane optimizes the input impedance at patch resonant modes on the thinner substrate, which yields wider bandwidth. Against the conventional ground plane design on substrate thickness > 0.06λ_g, the bow-tie shape ground plane offers 0.03λ_g reduction in total substrate thickness, 10% increment in the bandwidth with a peak broadside gain of 6.1 dBi. The design methodology to realize a similar configuration as per a specific frequency spectrum is presented, which yields similar response.

This article proposes an approximate analytical formulation to calculate the low-frequency magnetic shielding of a rectangular metallic box, with all walls perforated periodical holes. The solution is obtained by the combination of two submodels: the finite conductivity box with the holes covered and the perfect conductor box with the holes present. The first submodel represents the diffusion effect of magnetic field penetration through the conducting shell, and the second one denotes the aperture effect of magnetic field leakage through the holes. The total shielded magnetic field is the superposition of these from the two submodels. For the diffusion effect, an existing empirical formula based on the shape factor is used. To solve the second submodel, we employ two approximate methods: the method of images and the surface-impedance method. The method of images models each hole in the walls as an equivalent magnetic dipole and its images based on Bethe's small aperture coupling theory. A PEC box is first considered. Comparisons with finite element simulations show that the method of images has better accuracy than the surface-impedance method. Then, a cubic aluminum box of 0.2 m in length is treated, which verifies that combining the two submodels can produce results in good agreement with finite element simulations for frequencies up to 10 MHz. In addition, the dependence of the shielding effectiveness on frequency is also analyzed.