This paper proposes an improved design of a W-band slot array antenna, based on a ridge waveguide and a rectangular micro-coaxial line. To achieve a high gain and wideband antenna with element spacing smaller than half a wavelength, a broadband transition of rectangular coaxial line to ridge waveguide was designed. The improved design has bandwidth around 15.4 GHz (94.8 GHz-110.2 GHz), and the simulated realized gain is about 14.6 dB. Measured results of the fabricated antenna demonstrate that the gain at theta = 0°, and VSWR is better than 13 dB and 2.7, respectively. The antenna's size is about 12 mm × 5.5 mm × 0.46 mm.

A new technique to reduce the mutual coupling between closely-spaced, single-layered patch antenna elements is presented. The proposed design comprises an integrated novel decoupling structure to generate an out-of-phase decoupling signal to effectively lower the coupling between the elements. In addition, coplanar L-probes and interdigital filter shaped slits on the ground plane are incorporated to further improve the isolation. The realized isolation level is about 28 dB at the frequency of operation. This is a significant achievement for a single-layered low-profile structure, wherein the center-to-center element spacing is only around 0.25λ₀, and more importantly, no shorting vias are used.

A design technique to develop the desired pattern with uniform spacing between elements for a resonant linear slot array on the broad wall of a rectangular waveguide is discussed in this study. First, linear array pattern synthesis is used to achieve the amplitude and phase of the array element. Then both radiation pattern synthesis and the array input impedance matching are achieved using the least-squares method. In addition, the error function is created by combining the three terms of impedance matching, array pattern synthesis, and slot design equations. Genetic algorithm (GA) and the conjugate gradient (CG) technique are used to minimize the acquired error function. The utilized approach results in precise pattern synthesis, good impedance matching, development of appropriate design equations, and power loss minimization. The computing needs were also reduced using the suggested antenna design. The approach is particularly beneficial since it integrates slot parameter dimensions and impedance matching with array pattern synthesis, resulting in a faster and more accurate design. Full-wave simulation Software HFSS was utilized to validate the suggested design method. Moreover, the measurements were conducted on a prototype designed to validate the simulation's accuracy and the designed antenna practicality, and excellent agreements between theoretical predictions and simulation results were achieved.

The narrow beam-width 120 GHz industry, scientific, and medical band compact substrate integrated waveguide (SIW) driven antenna's design and characterization are discussed in this study. A low-cost fabrication is ensured by the employment of a single RO4350B substrate layer with SIW feeding. A transition from SIW to a rectangular waveguide is made for measuring purposes. The radiation pattern has been measured. By determining the right feeding phases for the 20 elements, a Deep Neural Network (DNN) is used to softly compute the beam steering. The weighted hybrid Modified Gravitational Search Algorithm (MGSA) - Particle Swarm Optimization (PSO) approach and neural network with back-propagation technique are utilized to beam-steer by anticipating the appropriate feeding phases of the antenna array elements. To evaluate the effectiveness of the approaches, a number of sample instances are given that beam-steer the pattern in a variety of directions. In addition to allowing for the establishment of crucial analytical equations for the synthesis of antenna arrays, the neural network synthesis method also offers a great deal of flexibility between the system parameters in input and output, which makes the synthesis possible due to the explicit relationship given by them. The conventional technique of the phased array is compared with our DNN model for implementing beam steering.

A circularly polarized dual band wearable antenna using frequency selective surface backed reflector for radio frequency identification reader resonating at global ultra-high frequency band (860-960 MHz) & ISM band (2.4 GHz) is proposed in this work. For circular polarization, the corner is truncated at the opposite end of a square patch with periodic slots over the patch for getting an orthogonal electric field in both the X & Y axis direction. Another truncated inner square slot patch miniaturizes the antenna further for stable frequency response. Finally, the periodic frequency selective surface-based reflector is used for gain enhancement & crosstalk reduction. The simulated & measured results for antenna over human body are plotted against the required bandwidth. The return loss and maximum radiated gains of -31 dB and 8.30 dB are achieved at a resonating frequency of 2.4 GHz with the reading range and Specific Absorption Rate (SAR) of 6.98 m and 0.77 watt/kg respectively. At 865 MHz the return loss & maximum radiated gain is -23 dB & 5.31 dB with the reading range & SAR of 5.21 m & 0.65 watt/kg respectively. The proposed UHF RFID antenna is circularly polarized with the axial ratio bandwidth less than 3 dB with approximately 15% (860-965 MHz & 2.4-2.45 GHz) range. The designed wearable antenna provides better isolation when FSS is incorporated while enhancing the gain for longer read range. The FSS reflector below the antenna reduces the SAR for on-body wearable applications. This RFID antenna can be used efficiently for WBAN applications as a portable RFID reader wearable antenna for remote sensing & real time monitoring.

Interrupted Sampling Repeater Jamming (ISRJ) is an electronic countermeasure against radar echo signals that generates many false targets to mask the real target echoes, which seriously affects radar target detection performance. Most of the ISRJ suppression methods require accurate estimation of the signal parameters, and the estimation methods are complex. Based on the characteristics of discontinuous ISRJ sampling and orthogonality between multi-carrier phase coding (MCPC) signal's subcarriers, we propose a method for ISRJ identification and suppression based on an improved MCPC signal. By analyzing the pulse compression of the echo, we found that different types of intermittent sampling interference have different peaks after pulse compression. Based on this feature, we introduce Fractional Fourier Transform to filter out interference. Theoretical analysis and simulation results show that the method can effectively suppress the three classical ISRJ interferences. The method suppresses ISRJ during echo processing without any parameter estimation for real scenes and has stronger robustness than other existing schemes.

A compact metamaterial-loaded wideband monopole antenna is reported in this paper for wireless applications. Initially, a monopole antenna with a single stub was designed to resonate at 4 GHz. Still, it suffers from low gain, so to enhance the antenna parameters, a metamaterial unit cell was considered along the feed line and ground plane. Double split ring resonator (DSRR) is a modified unit cell of a typical split ring resonator (SRR) designed to achieve a good coupling effect. The dimensions of the proposed DSRR unit cell are 0.17λ₀ × 0.17λ₀, where λ₀ is the free space wavelength at 4 GHz. It achieved an impedance bandwidth (-10 dB) in the frequency range of 3.38 GHz to 4.08 GHz & 4.64 GHz to 5.2 GHz, having a 19.49% bandwidth in the 1st band and 11.7% bandwidth in the 2nd band. A wideband was achieved in the frequency range of 3.39 GHz to 5.13 GHz with 47.9% bandwidth when the number of stubs was increased to four. A maximum gain of 3.3 dBi was attained with bidirectional radiation in the E-plane, and it was omnidirectional in the H-plane. By increasing the number of stubs, two resonant modes were merged, making it wideband and suitable for WLAN applications like Wi-Fi & WiMAX & Satellite Communications.

In this manuscript, quad port highly isolated sextuple-band notched ultra-wideband (UWB) multiple input multiple output (MIMO) antenna is designed and experimentally investigated. The suggested design employs four antenna elements fabricated over a Rogers RT Duroid 5880 substrate and placed orthogonal to each other by deploying polarization diversity technique for good isolation. By combining polarization diversity technique with a fan shaped de-coupler isolation could be improved even more. Ameliorated frequency selectivity of notch bands can be accomplished by loading each antenna element with four U-shaped slots and C-shaped stubs adjacent to the feed line to exhibit band rejection of 3.18-3.51 GHz (9.86%), 3.71-3.99 GHz (7.27%), 4.59-4.76 GHz (3.63%), 5.18-5.34 GHz (3.04%), 7.47-7.74 GHz (3.55%), and 9.29-9.55 GHz (2.76%) to surmount the possible intrusion from WiMAX, C-band, INSAT, WLAN, X-band, and radio navigation (RN) band. Besides, an RLC equivalent circuit has been examined by correlating with the outcome of the reported notch band UWB-MIMO antenna that evinces highly selective notch bands. The suggested antenna works in the frequency range of 2.1-11.2 GHz which is suitable for UWB applications. Simulation and experimental validation is done to analyze the response of the suggested antenna with respect to notch frequencies, current distributions, peak gain, radiation patterns, envelope correlation coefficient, diversity gain, mean effective gain, total active reflection coefficient, channel capacity loss, and multiplexing efficiency.

In this article, two antennas having partial ground plane, slot loading with microstrip line feeding are proposed for wireless and biomedical applications. Antennas resonate at 2.4 GHz with two different bandwidths. The first antenna having 20% bandwidth, i.e., the Ultra Wide Band (UWB) of 2.10 GHz-2.61 GHz that can be utilized for wireless application and the Federal Communication Commission (FCC) allotted band of 2.36 to 2.39 GHz for medical applications falls in this range. The UWB antenna has undergone additional tuning to make it appropriate for biomedical application. Additionally a parametric analysis of antenna's slot length, width and dielectric constant is performed to optimize the performance characteristics. The antenna is fabricated and tested using Vector Network Analyzer. The acquired results from simulation and measurement are in close match.

In this paper, an unequal Filtering Power Divider (FPD) adopting a novel dual-band resonator and inter-digital feeding lines structure is presented. By integrating the resonator and modifying coupling mode, filtering and unequal power distribution are all achieved on the base of the deformed Wilkinson power divider. Two sets of cascading resonators operating at 2.45/4.44G with the same structure are proposed for WIFI and other application. Keeping with the unchanged coupling mode, the unequal ratio of 2:1 is arrived by adjusting the strength of coupling. The two resonant frequencies can be adjusted independently to ensure the flexibility of the design. For verifying the theoretical designs and simulated results, a fabricated FPD is exhibited, analyzed and measured. The simulated results are in good agreement with the measured ones with slight variations.

This paper presents the general numerical dispersion relationship for the three-dimensional (3-D) Radial Point Interpolation (RPIM) method in lossy media. A similar analysis has also been carried out and compared with the traditional Finite-Difference Time-Domain (FDTD) method. Both methods investigate dispersion, numerical loss, and anisotropy versus electric conductivity. The RPIM reveals lower numerical loss errors (NLE) in a wide conductivity range at the considered frequency. Furthermore, the numerical experiments show that a slight increase in the conductivity, for the lossless case, has almost removed the numerical anisotropy dispersion, which improves the numerical resonance frequency precision. Therefore, this effect can be used as an anisotropy optimization technique for lossless media. Based on a close examination of the experimental results around the resonant frequency, the numerical error for the lossless case was divided by ten. As a result, the experimental and theoretical resonance frequencies are found to be in good agreement.

Microwave staring correlated imaging (MSCI) is a super-resolution imaging technique based on temporal-spatial stochastic radiation fields (TSSRFs), which requires an accurate calculation of the electromagnetic field at the imaging plane. However, systematic errors always exist in practice, such as the time synchronization and frequency synchronization errors of radar systems, which make it difficult to calculate the required TSSRFs accurately, and this deteriorates the imaging results. Meanwhile, some imaging algorithms have problems such as high computational complexity. In this paper, an intelligent MSCI method based on the deep neural network (DNN) is proposed, which can accomplish imaging directly from the echoes, avoiding the computation of TSSRFs. A multi-level residual convolutional neural network (MRCNN) is developed for the DNN, and simulations and experiments are carried out to obtain the dataset for training and testing the MRCNN. Compared with the conventional MSCI methods, the imaging results verify the effectiveness of intelligent MSCI in terms of imaging quality and computational efficiency.

In this paper, a broadband circularly polarized (CP) microstrip antenna array for S-band is proposed. The antenna consists of a parallel rotating feed network, sixteen units with cut corners, adding rectangular perturbations, and the guided patches with 45˚ oblique rectangular slots. The guided patches increase the impedance bandwidth of the antenna, and the feed network with a 90˚ phase difference increases the axial ratio bandwidth. The simulation and measurement results show that the S₁₁ curve is 2.45~4.15 GHz; the impedance bandwidth is 51.5%; the frequency with the axial ratio less than 3 dB is 2.54~3.74 GHz; the working bandwidth is 1.2 GHz; the CP bandwidth is 38.2%; the gain is 18.72 dB at the S-band center frequency. The advantages of the designed antenna are high gain, wide bandwidth, and a good radiation pattern. It can be applied to early warning radar in S-band. It also completely covers China Mobile's 2.6 GHz spectrum and can be used as a base station antenna if taking no account of the polarization method. The antenna has a simple structure, which is suitable for applications.

This paper presents a low-profile, flexible and wearable slot antenna for on-body communication. The proposed antenna is designed on a thin polyamide substrate of 0.25 mm height, which is flexible, elastic, and robust in nature. A rectangular patch with different slots acts as the main radiator, and partial ground acts as the bottom conducting plane for the proposed antenna. The designed antenna was able to resonate in the desired frequency band with a good return loss (S₁₁) by modifying the size of the ground plane along its width and placing a small cut on the ground. The designed antenna achieved a good -10 dB impedance bandwidth of 710 MHz and a peak gain of 7.2 dBi at 5 GHz. The designed antenna was checked for detuning in a bending scenario. The specific absorption rate (SAR) was evaluated, and the values were found to be within standard limits. The designed antenna was fabricated and tested in this study. The results showed good agreement between the simulated and measured values of the antenna parameters. The small size, low weight, and flexibility of the proposed antenna make it a good candidate for wearable devices in the WLAN/WBAN environment.

A systematic study of a low SLL (sidelobe level) two-way pattern in shared aperture arrays is presented. Three or two-weight excitations are used for the elements of the transmit and receive arrays depending on the requirements. The receive array has a smaller number of elements by not receiving from some of the edge elements of the transmit array. The condition of appearance of certain minor lobes of the transmit array pattern at certain nulls of the receive one helps to find the ratio between the number of elements of the receive and transmit arrays. In the case of more than one possible ratio, the optimum ratio is the one that gives the lowest SLL. In the three-weight array the total number of the transmit elements is equal to the that of the two higher excitations plus the number of elements of the highest one. In the two-weight excitation the higher weight elements of the transmit array are chosen to be approximately one half of the total elements. The excitations of both arrays are found by equating the level of the higher two unequal sidelobes of the two-way array factor. The three-weight array design is presented for the first time while the two-weight case gives lower peak SLL than those of the literature. Our work contains the important steps of the design and the main aspects of the implementation. The resulting peak SLL of the two-way array pattern reaches up to less than -51.2 dB and less than -56.5 dB, for the two- and three-weight cases, correspondingly.

In this paper, a flexible 2-port MIMO antenna with dual band-notched properties is designed and built for wireless body area network applications. The antenna's performance in its flat and bent states is measured using liquid crystal polymer as a substrate. Two UWB slot antenna components are arranged parallelly with linked ground. Furthermore, to achieve high port isolation, a decoupling device in the form of a fence is positioned between two antenna units. The measured operating bandwidth can reach 3.0-15.7 GHz, with blocking bands of 5.0-6.5 and 7.0-7.9 GHz. Port isolation (S₂₁) is better than 20 dB. This antenna has fine radiation properties, high isolation, and flexibility, according to the bending and flat antenna tests. It has a promising future for wearable Internet of Things applications.

In order to reduce the multipath fading caused by the reflection of various obstacles in short-distance communication, this paper designs a quaternion MIMO millimeter wave antenna working at 28 GHz. The antenna design adopts an inverted trapezoidal radiation patch and a slotted trapezoidal ground plate structure, so that the S₁₁ of the antenna is lower than -10 dB in the frequency band of 24~32 GHz. By using a 1×2 array structure as the unit of MIMO antenna, the gain of the antenna at 28 GHz is 7.5 dBi. The isolation degree of each port is lower than -25 dB by orthogonal placement of each unit. The performance of the antenna is tested by the physical production test. The actual test results show that the operating bandwidth of the antenna is consistent with the simulation results. The gain at 28 GHz is slightly lower than the simulation results by 0.1 dBi, and the isolation of each port is lower than -18 dB, which is 7 dB away from the simulation results but still meets the requirement of -15 dB for MIMO communication. The measured results show that the antenna can be used in MIMO short-distance communication system.

As one of the most important technologies for the next generation very-large scale integrated circuit fabrication, extreme ultraviolet (EUV) lithography has attracted more and more attention in recent years. However, in EUV lithography, the optical distortion of the printed image on wafer always has negative impacts on the imaging performance. Thus, to enhance the imaging performance of EUV system, especially for small critical dimensions, in this work, a novel optical proximity correction (OPC) system based on the deep learning technique is proposed. It includes a forward module and an inverse module, where the forward module is employed to fast and accurately map the mask to the corresponding near field of the plane above the stack to help the construction of training dataset for the inverse module operation, and the inverse module is employed to fast and accurately map the target printed image to the corrected mask. Numerical examples demonstrate that compared with traditional full-wave simulation, the forward module can greatly improve the computational efficiency including the required running time and memory. Meanwhile, different from time consuming iterative OPC methods, the corrected mask can be immediately obtained as the target printed image is input using the trained inverse module.

On the basis of artificial magnetic conductors (AMCs), a dual-band MIMO antenna is suggested. For WBAN and WLAN applications, the frequency ranges supported by this antenna system are 2.36-2.51 GHz and 5.03-6.12 GHz. The proposed dual-band MIMO antenna is made up of two vertically positioned dipole antenna elements. A simple double circle-based AMC array is suggested to decrease radiation exposure to people while increasing forward gain. The antenna and the 3×3 AMC array are both printed on an FR4 substrate. The presented antenna with the AMC structure is manufactured and measured in order to confirm the simulated results in terms of S-parameters, radiation patterns, gain, and diversity parameters. According to the measurements, the suggested antenna exhibits peak gains of 3.34 dBi and 7.48 dBi at 2.45 GHz and 5.8 GHz, respectively. The SAR value of body tissue can be reduced by around 99% while the front-to-back ratio (FBR) is noticeably enhanced. The proposed AMC-supported MIMO antenna is applicable for WBAN and WLAN applications based on the above good performances.

Within the framework of the first-order small perturbation method, we derive the statistics of the layered rough surface index and the normalized difference polarization index for three-dimensional layered structure with slightly rough interfaces illuminated by a monochromatic plane wave and for multilook returns. We establish closed-form expressions for the probability density function and the cumulative distribution function. The first- and second-order moments are given by relation recurrences. We validate from Monte Carlo simulations the obtained theoretical formulas.