Distributed beamforming (DBF) is an efficient technique for reliable communications in wireless sensor networks (WSNs). In DBF based networks, the randomly distributed nodes cooperate together to form a randomly distributed antenna array (RAA) which has a main beam directed towards the intended receiver. Due to the nodes randomness, the DBF results in poor pattern characteristics such as high side lobe level (SLL) and pattern asymmetry around the main beam sides. In this paper, a fast deterministic algorithm for SLL reduction of open loop distributed antenna arrays is introduced. Unlike the existing state of the art optimization techniques for SLL reduction, the proposed algorithm provides a fast deterministic solution for energy transmission or the weight of each node without changing its location. Consequently, the exhaustive search burden of the optimization based techniques for the optimum weights is avoided. The simulation results reveal that the proposed algorithm has superior performance to the optimization techniques in terms of execution time, synthesized SLL, and half power beam width (HPBW).

The goal of this paper is to design a dual band antenna for the integration of LTE-R 700-MHz band along with 5G (3.5 GHz) band applications for future advanced railway communication. A design study of the dual band antenna is proposed and discussed in detail. An ellipse-shaped ring patch is designed for the LTR-R 700-MHz band, and the 5G (3.5 GHz) band is added by keeping the circular patch in proximity to the feed line of the antenna to make it a stacked antenna configuration. Circular patches with varying dimensions are used to increase the bandwidth at 3.5-GHz band. The antenna has a size of 180 mm x 60 mm and is fabricated on an FR4 substrate with dielectric constant 4.4 (tanδ = 0.025). The observed bandwidth is approximately 100 MHz and 500 MHz for each frequency band respectively.

A computationally efficient, integrated and dynamic model has been developed for the design of a planar Slow Wave Structure (SWS) and beam-wave interaction analysis of a planar THz Traveling Wave Tube (TWT) with sheet beam. A Staggered Double Vane-Slow Wave Structure (SDV-SWS) is used for its numerous advantages over other types of SWSs. The integrated model determines RF performance of a planar TWT directly from the given beam voltage and center frequency by performing three different tasks, (i) determining geometrical parameters of a SDV-SWS of maximum possible bandwidth and high interaction impedance, (ii) determining RF circuit parameters of a SDV-SWS, and (iii) performing beam-wave interaction analysis of a planar TWT. The model was developed by adopting numerically computing environment, MATLAB. Also, highly accurate numerical techniques with double precision were used, e.g. Sixth Order Runge Kutta Method was used for electron beam dynamic. The model was used to design and simulate a 0.22 THz Sheet Beam TWT of 100W output power. The energy balance factor was achieved within ±0.001% over a very wide dynamic range from even 100 dB below saturation to more than 10 dB above saturation. The power growth of the forward wave was achieved with exactly 1 dB/dB. The program is fast enough for interactive use on a standard computer with a basic configuration. The model has been compared with the published works using 3D electromagnetic field simulator for demonstrating its accuracy.

We present design and computational simulation of multiband, polarization-independent, and thin frequency-selective structures for microwave frequencies, and their fabrication via a very low-cost inkjet-printing procedure. The structures are constructed by periodically arranging unit cells that consist of U-shaped resonators, while polarization-independency is achieved by applying rotational arrangements. Various configurations are obtained by considering double and single U-shaped resonators, as well as rotational and complementary relationships between the corresponding unit cells on the top and bottom surfaces. We observe that complementary arrangements provide resonances with better quality, particularly by allowing the smaller resonators to operate as desired. Measurements on the fabricated samples demonstrate the feasibility of both effective and very low-cost inkjet-printed frequency-selective structures with multiband and polarization-independent characteristics.

The possibility of application Clavin type radiators in combined two-frequency antenna arrays with diode switching of vibrator and slot elements is validated. The conventional Clavin elements with passive monopoles operating at the main frequency and two active monopoles operating at the alternative frequency are used as the combined array radiator. Radiation fields of combined arrays at both frequencies are analyzed. It is shown that the alternative wavelength should not exceed the main wavelength by more than 25%.

For direct suspension force control (DSFC) strategy of Bearingless Brushless DC Motor (BBLDCM), combined with super-twisting algorithm, a second-order sliding mode (SOSM) controller is designed by direct suspension force. The control precision, robustness, and jitter suppression of the suspension subsystem are improved. The direct suspension force control based on the second-order sliding mode (SOSM-DSFC) controller solves the influence of external disturbance on the self-stabilizing suspension, effectively suppresses the rotor jitter problem, and improves the robustness of the rotor suspension.

Aparticular challenge encountered in designing massive MIMO systems is how to handle the enormous computational demands and complexity which necessitates developing a new highly efficient and accurate approach. Considering the large antenna array employed in the Base-Station (BS), in this work, we present a new paradigm to significantly reduce the simulation runtime and improve the computational efficiency of the combined rigorous simulations of the antenna array, 3-D channel model, and radiation patterns of the User Equipment (UE). We present an approach for evaluating a closed-loop massive MIMO channel capacity using 3-D beamforming to take advantage of spatial resources. The approach subdivides an M×N array at the BS into columns, rows, rectangular, or square subarrays, each consisting of a sub-group of antenna elements. The coupling is rigorously taken into account within each subarray; however, it is ignored among the subarrays. Results are demonstrated for a dual-polarized microstrip array with 128 ports. We consider simulation runtimes with respect to two different propagation environments and two different Signal-to-Noise-Ratios (SNRs). It is shown that the maximum difference in the closed-loop capacity evaluated using rigorous electromagnetic simulations and our proposed approach is 2.4% using the 2×(8×4) approach for both the 3-D Channel Model in the 3rd Generation Partnership Project (3GPP/3D) and the 3-D model in the independent and identically distributed (i.i.d/3D) model with a 46% reductional in computational resources compared with the full-wave antenna array modeling approach.

A ridged horn antenna with metallic grid sidewalls is proposed and quantitatively analyzed. Simulated and measured results indicate that the operating band is from 1.0 to 20.0 GHz with the reflection coefficient less than -10 dB, and the relative bandwidth is as high as 180.95%. The gains are greater than 10 dBi in the frequency band of 2.6-20 GHz, greater than 16 dBi in the frequency band of 10-20 GHz with the gains fluctuation less than 1 dB. In the whole operating band, the radiation patterns radiate directionally along the normal direction of the horn aperture and do not split. In this paper, the ridged horn antenna with metallic girds is analyzed quantitatively. A modified equivalent traveling wave current model of the ridged horn antenna is proposed, which matches better to the patterns of the ridged horn antenna in high frequency band. The working mechanism of metallic grid sidewalls is also analyzed quantitatively, and the reason that metal strips can improve the matching performance of ridged horn antenna in low frequency band, restrain the patterns splitting in high frequency band and improve the antenna gains is explained. The proposed antenna has the characteristics of ultra-wideband, stable gains, miniaturization, and directional radiation patterns with no splitting main lobe in ultra-wideband. The proposed ridged horn antenna can be used for the measurement in a microwave anechoic chamber.

The estimation of the direction of arrival (DOA) and the estimation of the number of signal sources are very important techniques in modern communications. The effect of mutual coupling can degrade the performance of the estimation algorithms. Mutual coupling compensation is used to mitigate this effect. However, errors remain when the compensation is carried out with such methods as minimum description length (MDL) to estimate the number of signal sources. This work presents a new method based on threshold decision to estimate the number of signal sources in presence of mutual coupling. The results of computer simulations demonstrate that the proposed method outperforms the MDL method.

This paper presents a novel reconfigurable filtering antenna with three tunable states used for IoT applications. The frequency reconfigurability is achieved using the combination of a hairpin filter and an open loop filter in the structure with the switching of p-i-n diodes. The open-loop filter structure provides two narrow band states at 2.4 GHz and 7.8 GHz, and the hairpin filter provides a single narrow band state at 10.4 GHz. The frequency reconfiguration is obtained without compromising the compact size of the designed circuit along with the targeted frequency bands at lower WLAN (2.47 GHz), WiMAX (3.42 GHz), INSAT C-band (7.18 GHz), fixed/mobile satellite service in X-band (8.4 GHz), direct broadcast service in Ku-band (12.14 GHz) applications. The prototype is constructed on an FR4 substrate and tested for validation in an anechoic chamber. The designed antenna provides excellent radiation characteristics and considerable gain at resonant frequencies. The proposed reconfigurable antenna is also tested using the CDAC Cmote device in the real-time environment and found more suitable for the IoT based communication applications.

In the installation of a dynamic wireless power transmission system of rail transit, the distance change among coils causes large power loss under high power conditions. Due to the limitation of detection surface and Doppler effect as well as other deficiencies, the traditional ranging methods cannot be adapted to fast, continuous, and large-area dynamic ranging in the wireless power transmission of rail transit. Therefore, the paper proposes a single coil dynamic wireless power efficiency optimization method based on electromagnetic induction for the first time. The distance between the transmitter and receiver is taken as the intermediate quantity, and the relationship between the detection coil amplitude and the wireless power transmission efficiency is constructed. Firstly, based on electromagnetic field theory, a quantitative relationship among the detection coil amplitude, wireless power transmission efficiency, and coil distance is established. Then detection experimental platform is designed. Finally, relevant experiments are accomplished through the established experimental platform. The experimental results show that for the area with low power transmission efficiency on the whole dynamic wireless power transmission line, relevant ranging data can be obtained by detecting the amplitude.

Due to suppressing the interference from WLAN (2.4-2.484 GHz), WiMAX (3.3-3.7 GHz), INST (4.5-4.8 GHz), X-band (7.25-7.75 GHz) and ITU band (8.01-8.5 GHz) signals in ultra-wideband (UWB) communication systems, a novel UWB antenna with five notch bands is proposed. Based on the methodologies of loading parasitic stubs and etching slots, the antenna is designed with five band rejection elements: a curved stub, a split square ring-shaped slot and a pair of vertical slots introduced in the patch, two C shaped stubs symmetrically set near the feed line, and a pair of L-shaped slots etched on the ground plane. The test results show that the antenna operating from 1.95 to 10.73 GHz is capable of rejecting the frequency bands around 2.4 GHz, 3.5 GHz, 4.6 GHz, 7.5 GHz, and 8.4 GHz. Meanwhile, in passbands the antenna has approximate omnidirectional radiation patterns and a peak gain higher than 1.7 dBi. The proposed antenna with dimensions of 31 × 35 × 1.5 mm³ is simple in structure and meets the requirements of UWB systems applications.

Graphite receives tremendous attentions as filler for conducting composite due to its low cost and high electrical conductivities. In this work we use polyvinylidene fluoride (PVDF) as insulating matrix and graphite (Gr) as a filler to develop conducting composite films using solvent casting technique. The dielectric properties of the developed PVDF-Gr films were analysed for the frequency range of 100 kHz to 10 MHz. The morphology of the obtained films was investigated by scanning electron microscopy. The EMI shielding properties of the PVDF-Gr composite films were evaluated theoretically using ɛ′, tan δ, and σ in the desired radio frequency region. Mechanical strength of the films was tested by universal testing machine. Due to advantages such as light weight, flexibility, and low cost the developed film with the thickness of ~0.15 mm had very good potential to be used for fabricating electromagnetic compatible electronic devices.

In this paper, a center-fed substrate integrated waveguide (SIW) inclined slot array antenna is designed for a one-dimensional active phased array. A novel coaxial-to-SIW transition is employed to realize the central feed for enhancing bandwidth. The antenna prototype printed onto a single-layer Rogers 5870 is composed of 32×16 inclined slots working at Ku-band. As shown in measured result, the bandwidth with return loss < -10 dB is from 16.6 to 17.1 GHz, and the sidelobe levels of arrays are below -24.8 dB at 16.8 GHz in H planes. The measured gain is 31.8 dB at 16.8 GHz with the aperture efficiency of 65%. The active phased array is assembled by an antenna and 32 Tx/Rx modules, and the measured results show that the main lobe can obtain a wide-angle scanning from -45 to 45 degrees in E planes. The antenna array is suitable for low profile small active phased array radars and communication systems that require spatial wide-angle scanning.

This article presents a bandstop Frequency Selective Surface (FSS) prototype based on square split ring resonators (SSRRs) and a square loop (SL) structure for Ultra Wide Band (UWB) frequency range. Triple band notches are obtained at WiMAX (3.3-3.6 GHz), WLAN (5-6 GHz) and Satellite communication X-band (7.2-8.4 GHz). To make this proposed design work as a band-stop filter, two SSRRs are positioned at the top layer of the substrate to resonate at WiMAX and WLAN frequency band respectively. A single SL is located at the bottom of the substrate that resonates at Satellite communication X-band. Attenuation more than 20 dB is observed at all notched frequencies. An angular stability from 0˚ to 40˚ is obtained. Compact size, simple structure, low cost material, single layer, easy fabrication, and wide coverage are some of the feathers of this proposed FSS. The dimension of proposed unit cell of FSS is 10x10 mm².

An inverse method for parameters estimation of dielectric cylinders (dielectric properties, location, and radius) from amplitude-only microwave information is presented. To this end two different Artificial Neural Networks (ANN) topologies were compared; a Multilayer Perceptron (MLP) and a Convolutional Neural Network (CNN). Several two-dimensional (2D) simulations, with different sizes and locations of homogeneous dielectric cylinders employing the Finite Differences Time Domain (FDTD) method, were performed to generate training, validation, and test sets for both ANN models. The prediction errors were lower for the CNN in high Signal-to-Noise Ratio (SNR) scenarios, although the MLP was more robust in low SNR situations. The CNN model performance was also tested for 2D simulations of dielectrically homogeneous and heterogeneous cylinders placed in acrylic holders showing potential experimental applications. Moreover, the CNN was also tested for a three-dimensional model simulated as realistic as possible, showing good results in predicting all parameters directly from the S-parameters.

In this paper, a hexagonal-shaped multiple-input multiple-output (MIMO) patch antenna is presented. It covers the S band (2-4 GHz), WLAN (2400-2480 MHz & 5150-5350/5725-5875 MHz), UWB (3.1-10.6 GHz), and X band (8-12 GHz) applications. The proposed structure is simulated and fabricated on an FR4 substrate with overall dimensions of 0.186λ₀ x 0.373λ₀ and separation of two patches with a distance of 0.053λ₀ (where λ₀ is the wavelength at 2 GHz). The single UWB patch antenna is derived from the triangular-shaped edge cuttings in the bottom of the rectangular patch antenna with partial & defected ground. The proposed MIMO structure produces simulated results from 2 GHz to 13.3 GHz and measured results from 2.1 GHz to 12.9 GHz, with good agreement. The proposed structure resonates at 3.4 GHz, 5.8 GHz, 10.2 GHz and 11.8 GHz. Isolation improved to below -20 dB by placing an E-shaped tree structure and parasitic element. The radiation efficiency and peak gain values are 78-94% and 1.4-6.6 dB, respectively. Diversity performance of the proposed structure is verified with low envelope correlation coefficient (ECC < 0.04), high diversity gain (DG > 9.985), and acceptable total active reflection coefficient (TARC < -10 dB) values.

An optimized dual-bandnotched antenna for Ultra-Wide Bandapplications, using the Genetic Algorithm (GA), is presented. By optimizing a Defected Ground Structure (DGS) in the ground plane of the UWB antenna, two notches are created at the desired frequency bands of 3.5 GHz and 5.8 GHz, respectively. A good agreement between the measurement and simulation results is observed. The optimized DGS shows good performance and accuracy compared to conventional approaches.

In this paper, the radar target recognition is given by frequency-diversity RCS (radar cross section) together with kernel scatter difference discrimination. The frequency-diversity technique means to collect electromagnetic signals by sweeping the operation frequencies. Such a technique is usually utilized in inverse scattering and radar target recognition because different frequencies each may contain important information of a target. By using the frequency diversity RCS technique, one can reduce the times of spatial measurement. This is an important contribution since it is always difficult to build a spatial radar measurement in practical battlefield environments. To enhance the pattern recognition, the collected RCS data are processed by the kernel scatter difference discrimination, which is improved from the Fisher discrimination. To investigate the capability of tolerating environmental fluctuation, each simulated RCS data is added by a random component prior to implementing pattern recognition. Numerical simulation shows that our recognition scheme is still very accurate even though the RCS contains a random component.

This paper investigates a low-profile Multiple Input Multiple Output (MIMO) antenna with enhanced gain based on Defected Ground Structure (DGS). The proposed antenna consists of two sets of four elements (2 x 2), and it is yielded at the central frequency of 5.5 GHz for Wireless Local Area Network (WLAN) applications. Being on RT5880 with height of 1.575 mm, the overall dimensions of MIMO antenna and single array are 145 x 88 x 1.575 mm³ and 75 x 82 x 1.575 mm³, respectively. To get high gain and low mutual coupling for antenna, a Defected Ground Structure (DGS) is proposed and integrated on ground plane. At 5.3 GHz, the gain of antenna achieves approximately 9.5 dBi while mutual coupling level is under -20 dB. Besides, the MIMO antenna witnesses a radiation efficiency of 93%. The measurement results are compared to simulation ones to verify the performance of the proposed antenna.