In this paper, we present an efficient numerical method to calculate the frequency and time responses of the field scattered by an object buried between two random rough surfaces for a 2-D problem. This method is called Generalized PILE (GPILE) method because it extends the PILE method which considers only two surfaces or an object buried under a surface. The GPILE method solves the Maxwell equations rigourously by using a simple matrix formulation. The obtained results have a straightforward physical interpretation and allow us to investigate the influence of the object buried between the two rough surfaces. We distinguish the primary echo of the upper surface, the multiple echoes coming from the lower surface and those arising from the object. The GPILE method is applied to simulate the Ground Penetrating Radar (GPR) signal at nadir. The resulting time response helps the user to detect the presence of the object buried between the two random rough surfaces.

Photonic integrated circuits (PICs) and microwave integrated circuits (MICs) have been widely studied, but both of them face the challenge of miniaturization. On one hand, the construction of photonic elements requires spaces proportional to wavelength, and on the other hand, electromagnetic compatibility issues make it challenging to reach high-density layouts for MICs. In this paper, we review the research advances of miniaturized PICs and MICs based on surface plasmon polaritons (SPPs). By introducing SPPs, miniaturized photonic elements at subwavelength scales are realized on PICs, which can be used for highly integrated interconnects, biosensors, and visible light wireless communications. For MICs, since the metals behave as perfect conductors rather than plasmonic materials at microwave frequencies, plasmonic metamaterials are proposed to support spoof SPPs. Spoof SPPs possess similar characteristics to SPPs and can be used to realize high-density channels on MICs. Moreover, combining the latest theoretical research on SPPs, future tendencies of SPP-based MICs are discussed as well, including further miniaturization, digitization, and systematization.

To improve the performance (low torque ripple, high average torque and high efficiency) of the external rotor switched reluctance motor (ERSRM), a preference multi-objective optimization framework for design and control of an ERSRM based on CD-NSGA-II (Chi-square distance fast non-dominated sorting genetic algorithm) with gradient targets is investigated. Firstly, the structure of the ERSRM is introduced, and the comprehensive sensitive analysis that evaluates the influence of each design variable on optimization objectives is presented. Secondly, the initialization of population, cross-mutation method and sorting method of conventional NSGA-II are improved. Then, the practicability of this method was proved by standard test functions. Finally, the NSGA-II and CD-NSGA2-II are combined with the visual basic script (VBS) script to optimize the ERSRM, respectively. Finite-element analysis results confirmed the validity and superiority of the optimized design.

Benefit from the high resolution, penetrating and all weather advantages of millimeter-wave (MMW) imaging, MMW imaging plays an important role in remote sensing, security inspection, navigation, etc. Among the MMW imaging systems, synthetic aperture imaging radiometer (SAIR) utilizes aperture synthetic technology to achieve higher imaging resolution, but the perception information is insufficient, resulting in poor image quality. In order to improve the image quality of passive SAIR MMW image effectively, we propose a novel multichannel depth convolutional neural network (MDCNN) in this paper. Aiming at the characteristics of original MMW images with more noise in low-frequency information and less features in high-frequency information, wavelet transform is incorporated into the MDCNN to obtain the high and low frequency components firstly. Then, dense residual block and skip connection technology are adopted to denoise and enhance target information in the four independent channels respectively. Finally, high quality MMW images are synthesized by inverse wavelet transform. The simulation results show that the reconstructed images of MDCNN have better image quality (such as image contour and texture details) than other deep learning-based methods.

In order to obtain the analytical expression of the position of sparse array sensors under the condition of a given total array sensor number, a sparse array design method based on direct-connection of 4 uniform linear arrays (DCUA4) is proposed. By using the only known parameter of the total array sensor number, the sensor number and spacing parameters of four subarrays are obtained by mathematical operation, then the four subarrays are directly connected to realize the design of sparse array. It is proved that the aperture of the sparse array is large, and there are no holes. Because all the sensors are allocated to four subarrays, the number of small spacing sensor pairs in the array is controlled The performance of the proposed array is simulated based on the spatial smoothing MUSIC (SS-MUSIC) algorithm. The simulation results show that the proposed DCUA4 can produce a large virtual array aperture, realize high-precision direction of arrival (DOA) estimation under underdetermined conditions, and resist the influence of low mutual coupling.

The growing interest in collision avoidance automotive radar systems in K-band necessitates the development of dedicated antenna systems with 45˚ inclined linear polarization (LP). In this letter, a 45˚ inclined LP array antenna with Taylor distribution is proposed, designed, and fabricated.

Broadband differences interferometeric analysis of a three-layer planar polymer optical waveguide is proposed and optimized to detect the concentration of hemoglobin in blood. The dispersion characteristic and cutoff film thickness of proposed waveguide are obtained by matching the field at various boundaries. The obtained cutoff film thickness for TE₀ and TM₀ modes is 0.09 µm, 0.1 µm at operating wavelength 400 nm, and 0.19 µm and 0.23 µm at operating wavelength 800 nm, respectively. The effective refractive indices of TE₀ and TM₀ modes are obtained at two considered wavelength i.e. 400 nm and 800 nm, and hence the difference of their propagation constant is calculated. It is observed that the propagation constant of these modes decreases with the increase of wavelength. Also, the difference of propagation constant attains its maximum value at certain wavelength and decreases either side of this wavelength. The interference maxima signals at output are considered as sensing signal. The maxima of interference signals, close to the maximum value of propagation constant, are shifted sufficiently with the change in cover refractive index. The maximum sensitivity 3.8 nm/RIU is obtained in the proposed broadband differences interferometeric analysis of waveguide at film thickness 300 nm. Hence, at this film thickness the sensing signal changes by 0.68 nm/g/L of hemoglobin concentration in blood.

This article presents a circularly polarized (CP) dual lens (DL) antenna with high gain and wide axial ratio (AR) bandwidth for automotive radar applications. Proposed antenna system provides low AR and scan loss over a wide angular range. It consists of a linearly polarized (LP), wide band, aperture coupled planar feed antenna, an extended hemispherical lens and a planoconvex lens with thin parallel plates and air slabs. In-lens polarizer mounted to the flat surface of the planoconvex lens converts LP wave to CP state. Fundamental design rules to obtain CP is defined. A CP DL design in low dielectric permittivity material (ε_r=3) is introduced. It achieves simulated efficiency that varies between 75 and 82% within the 77-81 GHz automotive radar band. AR is below 2.2 dB for all scan angles up to 25˚. Realized gain at boresight radiation is 25.6 dBic at the center frequency. 0.85 dB scan loss is observed at ±30˚ scan angle. A frequency-scaled prototype has been fabricated by additive manufacturing process with fused deposition modeling, and the concept is proved by the experimental results in 22-28 GHz band.

In this paper, a rectangular embedded dual band Electromagnetic Band Gap (EBG) structure at frequencies 2.45/5.8 GHz useful in industrial, scientific, and medical (ISM) band for various wearable applications is proposed. The main intent of this work is to design a dual band EBG to reduce specific absorption rate (SAR). The unit cell which is a part of the EBG structure is formed using a rectangular patch. It has a U shaped rectangular slot and a stretched strip with a rectangular patch at end. EBG unit cell simulation is accomplished by solving eigen mode problem in High Frequency Structure Simulator (HFSS). EBG structure has to be suitably designed and fine tuned for specified band stop property to reduce surface waves. It must improve front to back ratio (FBR). With placing antenna on human body, frequency detuning occurs which is undesirable thus emphasizing the need of improvement in impedance bandwidth. This improvement can be achieved by a suitable design of EBG structure. In this work, the proposed EBG structure is integrated with a dual-band monopole antenna at frequencies 2.45/5.8 GHz for wearable application. The evaluation of antenna performance on a four layer body model is carried out. Simulations are used to demonstrate EBG array structure effectiveness for the reduction of Specific Absorption Rate (SAR) on the four layer body model. Computed SAR values for tissue in 1 g and 10 g are within standard prescribed limits. It is concluded that the proposed dual band antenna is appropriate for wearable applications. Proposed EBG array is fabricated and integrated with a twin E-shaped monopole antenna. The measurement of reflection coefficient, radiation pattern, and transmission coefficient of fabricated EBG array is carried out. The measured and simulated results show good agreement. Antenna performance in the event of bending condition and on-body condition is assessed.

With the development of communication technology, people's requirements for information transmission rate are getting higher and higher. Compared with the previous sub 6G frequency band, terahertz communication has a larger bandwidth and a higher rate. This paper studies the influence of azimuth angle of arrival (AoA) and azimuth angle of departure (AoD) on the received signal strength in the 220 GHz-320 GHz frequency band, as well as the influence of the signal passing through different obstacles, different dry humidity and material thickness on the signal power.

A novel metamaterial-based circular patch multi-input multi-output (MIMO) antenna is designed with a `C'-shaped defected ground structure for high isolation. A 4 × 4 mm<sup>2</sup> unit cell for a ring resonator has been designed and exhibited double negative material (DNG) properties from 1.0 to 2.92 GHz and 13.68 to 17.67 GHz and Mu negative material (MNG) from 4.70 to 13.67 GHz. The proposed antenna structure is designed by embedding the ring resonator-based meta-structure to a circular patch antenna and fabricated with dimensions 0.245λ<sub>0</sub>×0.409λ<sub>0</sub> (15×25 mm<sup>2</sup>). The proposed antenna operating at 8.50 to 14.23 GHz for X and lower Ku bands is used in the Unmanned Arial Vehicle (UAV's) applications. The spacing between elements is 0.088λ<sub>0</sub> (5.4 mm) on an FR4 epoxy substrate, and the `C'-shaped structure on the back of the antenna improves the isolation of more than 24 dB in the operating band. Distance between the antenna elements plays a crucial role, and parameters affected by this are optimized by introducing machine learning. For future predictions, a linear regression model was created to optimize the parameters' linear dependencies like isolation and return loss on the distance between the antenna elements. The radiation efficiency and gain of the antenna are enhanced by 92% and 6.02 dB at 13.22 GHz, respectively. The MIMO antenna's simulated results of diversity and other parameters are in the acceptable range with the measured results used for X-band radar applications. The proposed decoupling technique is simple to understand and implement.

In this paper, minimum variance distortionless response (MVDR) algorithm for adaptive Beamforming is applied to a linear array under known mutual coupling among half wavelength dipole (HWD) antennas. This algorithm will minimize the signals from all interference directions while keeping the desired signal undistorted. The problem of calculating mutual coupling coefficient of the array HWD antennas formed into a matrix has been considered. The obtained results show the effectiveness of the proposed method, in which the optimum weighting of adaptive antenna arrays is accomplished by computing the weight vector that achieves maximum towards the desired signal and nulls towards interferers. Also, performance evaluation of this algorithm in terms of complexity, convergence speed, and amplitude response will be present. It is shown from the simulation results that the performance of the beamforming algorithm considering the mutual coupling effect can be improved by the proposed compensation method. We also simulate the signal-to-interference-plus-noise ratio (SINR) with different input signal-to-interference ratio (SIR). The different results obtained are in good agreement with those of the literature.

This article introduces a unique dual-band notched Ultra Wide Band (UWB) Multiple Input Multiple Output (MIMO) antenna. The planned MIMO antenna has two identical Mushroom-shaped radiators with a combined dimension of 18×34×1.6 mm³. Inverted L-structured stubs are joined to the antenna's ground to provide enhanced port isolation. The proposed antenna achieves improved isolation of -23 dB over 3.08-12.8 GHz bandwidth. Two novel strips are extruded in the antenna's ground and mushroom-shaped radiator to introduce a notched WiMAX band (3.37-4.30) and WLAN (5.08-5.80) GHz band. The presented antenna's peak gain is achieved from 2 to 4.8 dBi, and the antenna's radiation efficiency is attained between 78 and 90% except for (3.37-4.30) GHz and (5.08-5.80) GHz stopped bands.

A flexible antenna with high robustness is presented for wireless body area networks (WBANs) in-body communications. The coplanar waveguide (CPW) fed hexagon slot structure is employed to obtain a wide bandwidth of 34.4%. A parasitic patch is used to enhance in-body gain to -3.36 dBi. With these advantages, the proposed antenna is insensitive to frequency shift and gain reduction caused by environmental changes. Besides, the proposed low-profile antenna on a flexible substrate is well fit for wearable applications.

A compact size UWB circularly polarized (CP) dual-port MIMO antenna is designed for Ku/K band applications. The proposed antenna contains a revised circle-shaped slot from the radiation patch on the front-side and a stepped-feed line on the back-side of the substrate. The orthogonal position of the antenna ports allows us to produce isolation of more than 30dB and has a (-10 dB) impedance bandwidth of 68% (14.3-29.3 GHz) at two resonant frequencies 15.6 GHz and 24.7 GHz respectively. 3 dB ARBW in the operating bands is 14.6% and 6.7%, respectively. The total size of the MIMO antenna is is 0.1λ × 0.05λ × 0.003λ mm³ at a lower frequency. Diversity characteristics like ECC, DG, TARC & CCL are determined to confirm the MIMO antenna's work qualities. Ringing resonating frequencies are observed at lower operating bands and are responsible for gain degradation. The proposed antenna has excellent characteristics for satellite and NASA's Tracking Data Relay Satellite application.

Wireless power transmission system (WPTS) based on electromagnetic induction is a promising way to power a gastrointestinal capsule robot (CR) for wireless diagnosis, which typically consists of a one-dimensional (1-D) power transmitting coil (PTC) to excite an alternating magnetic field and a three-dimensional (3-D) power receiving coil (PRC) to induce signal. However, it is difficult to apply a 3-D PRC to practical medical applications since the oversize bodily form of the mounting receiver brings the extra challenge of design for microCR. This paper proposes a novel WPTS with space-saving architecture by combining a two-dimensional (2-D) power transmitting coil (PTC) outside the human and 1-D PRC onboard the CR, which can permit CR to accomplish the mission of exploring the intestinal space with wireless energy supplying owing to small size related to 1-D PTC. The analytical expressions of the magnetic flux density, magnetic field orientation, and uniform magnetic field excited by the designed PTC are derived. Simulated and experimental outcomes are implemented to achieve the desired magnetic field strength and direction by changing the transmission current of PTC, which verifies the feasibility and effectiveness of developed methods. And the magnetic field uniformity is greater than 44%. It can basically cover the 20 cm×20 cm area of the human abdomen at all times, which can permit the operational requirements of the CR in the practical case.

We propose the design of a dual-band nano-structured polarizer that allows the transmission of two different linear polarizations within different frequency bands. A broad-band transmission window in the visible range exists for the x-polarization, whereas the y-polarization transmits efficiently in the near-infrared range. The transmittance exceeds 80% for the target polarization in both cases under normal incidence. This operation is achieved by an orthogonally patterned metallic surface having a long metal wire along the x-axis with four other small metal wires along the y-axis and allowing for a strong localized slit resonance to operate in the desired passband. The appropriate metal length and air gap choice lead to intense slit resonances in the spectral region of choice. The proposed design can be optimized for either ultrawide single band operation or dual-band perpendicular polarization operation.

In this paper, a novel dual-frequency circularly polarized (CP) antenna applied to BDS system is presented. CP radiation is achieved by etching slotted circular patches of complementary open-loop resonators, which are excited by a feeding network consisting of a double-layer power divider. The circular patch is miniaturized by a complementary split-ring resonator (CSRR) etched on the patch. The overall dimension of the antenna is only 0.32λ₀×0.32λ₀×0.0104λ₀, where λ₀ is the corresponding free space wavelength at 1.268 GHz. The proposed antenna has 50 MHz (1.25-1.30 GHz) and 60 MHz (1.53-1.59 GHz) impedance bandwidth and 20 MHz (1.25-1.27 GHz) and 20 MHz (1.55-1.57 GHz) axial ratio bandwidth, respectively. The antenna profile is low, which is easy to install. Because of these performance indexes, the antenna has superior practicability in BDS system.

Contactless identifying different life states can result in improved rescue strategies in post-disaster rescues (such as earthquake and mine accident). If the buried targets are identified extremely endangered with very poor life states, the rescuing principles should be time first. Conversely, if the life states of the buried targets are relatively good, more reliable and safer methods should be given priority although they may cost a little more time. Unfortunately, there are few corresponding reports in life states identification, and current researches mainly focus on detecting or locating under penetration condition. This paper conducts a research on the change laws of physiological parameters of six New Zealand white rabbits, 3 females and 3 males. Experimental condition is under water and food deprivation to simulate one of the typical trapped situations of buried targets in post-disaster rescuing missions. Respiration is synchronously detected by an ultra-wideband (UWB) system in non-contact and an RM6240E system in contact. Heart rate, weight, and anal temperature are measured in contact measurement meanwhile. Over the time under water and food deprivation condition, there are typical and regular varieties in the respiration waveforms and heart rate values, which provide the possibility to identify different life states. Particularly, the respiration waveform changes in UWB radar signals are envisioned to be applied in practical post-disaster rescue where only UWB radar can penetrate ruins through penetrating measurement method.

The present work demonstrates the design of a wideband 2×1 reconfigurable beam steering array for wireless communication systems. The designed antenna is powered by a microstrip line, and consisting of a two rectangular-shaped radiating elements and a rectangular planar ground. Its dimensions are the following: 0.67λ₀ x 0.53λ₀ x 0.03λ₀. It executes three reconfigurable operating states by turning on and off two PIN diodes to change the direction of the main beam, as well as a beam tilt ranging from (±30°) to (±38°). A progressive analysis in order to enhance the the antenna characteristic performances is furnished. The proposed reconfigurable antenna bandwidth is 18.18% (simulated), 18.84% (theoretical) and 19.42% (measured). The presented antenna has a maximum gain of 8.62 dB (simulated) and 8.45 dB (measured), and a higher efficiency ratio of 80% to 86% over the operating band (5 GHz-6 GHz). The designed antenna is fabricated using a low loss Rogers RT5880 substrate of 2.2 relative permittivity. The simulated, theoretical and measured results are presented and exhibit good accord, including the S₁₁ parameter and radiation patterns. In addition to the pattern reconfiguration, the obtained results are useful in order to improve the overall gain, antenna bandwidth and efficiency.