The combination of low peak sidelobe level (PSLL) with wide sector nulling digital beamforming (DBF) is achieved for large planar array antennas. This combination is carried out using the iterative Fourier transform (IFT) method. The method is based on the iterative Fourier technique to derive element excitations from the prescribed array factor using successive forward and backward Fourier transforms. A 1024-element rectangular uniformly spaced array is used as an example to demonstrate the performance of the proposed method. Numerical examples show that the proposed method achieves very low PSLL with very wide nulling sectors up to the half plane of the far-field pattern. Moreover, numerical results show that the proposed method is effectively functional even when the mainbeam is steered to directions other than the broadside.

In this paper, a compact negative-group-delay (NGD) microstrip bandpass filter is proposed. The NGD characteristic is achieved by coupling a resistor-loaded microstrip line to a square open-loop resonator. To improve the selectivity, the square open-loop resonator is loaded with an open-circuited stub for realizing two transmission zeros (TZs) in the upper stopband. To verify the proposed method, an NGD microstrip bandpass filter with a size of 0.58λ_g × 0.35λ_g is designed and fabricated. From the measured results, the NGD time of -1.08 ns at the center frequency of 1.995 GHz is obtained with the NGD bandwidth of 34 MHz (1.977-2.011 GHz), in which the insertion loss is less than 7.5 dB, and the return loss is greater than 20 dB. Furthermore, three TZs at 1.520, 2.495, and 2.735 GHz are achieved with good stopband attenuation.

In this paper, we focus on the beamforming design in a two way amplify-and-forward relay network with energy harvesting, in which a three-node system consisting of two transmitters and one relay is considered. Specifically, we investigate the joint beamforming and power splitting scheme to obtain the maximum weighted sum rate. The formulated problem is non-convex and challenging. We equivalently transform it into a more tractable problem via successive convex approximation and constrained concave-convex procedure. Then, an iterative algorithm is proposed. Numerical results demonstrate the superiority of the proposed method, as well as the eect of dynamic power splitting in improving the sum rate of relay network.

Metasurfaces enable a new avenue to create electrically thin multi-layer structures, on the order of one-tenth the central wavelength (λ_c), with engineered responses. Altering the sub-wavelength spatial features, e.g. λ_c/80, on the surface leads to highly tunable electromagnetic scattering characteristics. In this work, we develop an ultra-wideband frequency selective metasurface (FSmS) that completely encompasses the Ku-band from 12-18 GHz with steep band edges. The geometrical structure of the metasurfaces is optimized by a multi-objective genetic algorithm mimicking evolutionary processes. Analysis is performed from one- to four-layer metasurface structures with various thicknesses. Computational electromagnetic simulations for these frequency selective metasurfaces (FSmS) are presented and discussed. The concepts presented in this work can be applied to design metasurfaces and metamaterials from the microwave to the optical regimes.

This paper aims at developing an approach allowing to detect, locate and characterize soft faults (i.e. isolation damage) in branched network composed of shielded twisted pair (STP) cables. To do so, a distributed reflectometry diagnosis where several sensors (reflectometers) are placed at different ends of the network is used to maximize the diagnosis coverage. The soft fault identification is achieved by using the Multi-Carrier Time Domain Reflectometry (MCTDR) combined with a Multi-Layer Perceptron Neural Network (MLP-NN). The main novelty here lies in the fact that the MLP-NN method is used for data fusion from several distributed reflectometers, which would eliminate ambiguities related to the fault location. The required datasets for training and testing of the NN are generated by simulation. Simulation and experimental results are dedicated to the validation of the proposed approach for locating and characterizing the soft faults in branched networks.

High Q-factor bandstop filter based on broadside-coupling between U-shaped coplanar waveguide (CPW) resonator and CPW through-line (CPWTL) is proposed in the present paper. The CPWTL is printed on the top layer of the dielectric substrate whereas the CPWR is printed on the bottom layer. Only over very narrow frequency band, around the resonant frequency of the CPW resonator (CPWR), the microwave power flowing in the CPWTL is coupled to (absorbed by) the CPWR leading to a bandstop filter of very high Q-factor. A CPWR with side ground strips of finite width is shown to have much higher Q-factor than that of infinitely extending side ground planes. Owing to the lower profile of the CPW with finite-width, the radiation loss is reduced, and the structure has narrower frequency band for coupling, which results in much higher Q-factor than other published works. The dimensions of the CPWTL are optimized for impedance matching whereas the dimensions of the U-shaped CPWR are optimized to obtain the highest possible Q-factor. The effect of the loss tangent of the dielectric substrate material on the Q-factor is investigated. A prototype of the proposed filter is fabricated and experimentally studied for more understanding of the underlying physical principles of operation and for experimental investigation of the filter performance. The experimental measurements show good agreement with the corresponding simulation results.

In this paper, an X-band, nonuniform and passive beam steering reflectarray antenna is presented. The beam steering is done with a small movement of a large element, i.e. the ground plane. The maximum ±7.5° beam scanning from the antenna broadside is achieved by only ±0.05λ ground tilting. In the proposed structure, the beam steering capability is provided by using passive elements that eliminate the need for active biased circuits. The linearity of beam scanning as a function of ground tilting is also investigated. Compared to the previous similar works, the antenna's half-power beamwidth and side lobe level are improved by about 9° and 20 dB, respectively. A primarily proposed reflectarray is fabricated to validate our claim.

A new design of dual and triple band rectangular microstrip antennas employing modified ground plane profiles is proposed. Slots introduced in the ground plane not only tune the higher order mode resonance frequency of the radiating patch but also alter the current distributions on the ground which yields multi-band response showing reduced cross polar level radiation pattern. Dual and triple band antennas yield 1 to 2% of impedance bandwidth at each frequency with gain around 1.5 to 2 dBi. Also in the multi-band design, 35% reduction in patch size against the conventional half wavelength counterpart is obtained. Further resonant length formulation at modified patch modes is presented which gives closer prediction of calculated frequency than the simulated value. The proposed multi-band design can find applications in personal communications systems requiring frequency agile capabilities.

In this article, a high gain dual band rectenna is proposed for energy harvesting applications. A dual band antenna is designed and optimized to operate at 3.5 GHz and 5.8 GHz frequency bands. The antenna is based on a multilayer substrate structure excited by aperture-coupling feed. In order to achieve a maximum gain of the antenna in both bands, a rectangular cell optimized by genetic algorithms is etched on the radiating element (patch). This antenna was simulated and fabricated, and the results show a good agreement in both bands (3.5 and 5.8 GHz) with a high gain of 10.2 dBi and 8.92 dBi for the first and second bands, respectively. A dual-band rectifier is also designed and studied to harvest the radio frequency energy absorbed by the antenna to DC energy at these frequency bands (3.5 GHz and 5.8 GHz). This rectifier shows a good performance in terms of conversion efficiency which achieves 44% in the first band and 29% in the second band. As a result, an output voltage of 656.88 mV for a low input power of 0 dBm is observed when the rectifier operates at both bands.

A linear polarization beam splitter operating in terahertz band is proposed and experimentally verified in this paper. The unit cell of beam splitter is composed of the top ``I'' type metal pattern, the middle dielectric layer, and the bottom metal layer. Each subarray structure of the device consists of four unit cells that rotate progressively at an angle of 45˚. The horizontal and vertical sub-arrays form the gradient metasurface of 4×4. The incident linear polarized terahertz wave is reflected by the device and divided into four beams with approximately equal power, while having different propagating directions in the 0.18-0.30 THz band. The proposed terahertz beam splitter has the advantages of small size, low cost, and easy processing, and it can be applied to terahertz stealth and terahertz imaging.

Spectrum sensing is one of the key functionalities in cognitive radios which enables opportunistic spectrum access. In this paper, a cooperative spectrum sensing (CSS) algorithm is developed to alleviate the problems of hidden terminals under impulsive noise environments. Firstly, the logarithmic similarity measure detector (LSMD) is constructed to solve the problem of outliers caused by impulsive noise. On the one hand, LSMD contains no free parameters, which is easy to implement. On the other hand, logarithmic similarity measure (LSM) converts logarithmic operations into multiplication operations, and then the computational cost can be greatly reduced. Moreover, original data fusion strategy is designed to reduce the amount of computation of CSS, while the accuracy of CSS is noticeably improved compared with the ``OR'' rule CSS. Besides, the solution of the unknown parameter of LSMD is directly given by theoretical analysis, and then the CSS exhibits higher efficiency. Simulation results show that the proposed method achieves much higher detection probability than the existing techniques under various scenarios.

This paper presents the design and development of a multi-element multi-segment half-sectored Cylindrical Dielectric Resonator Antenna (MEMSh-CDRA) with coaxial probe feed. The input and radiation characteristics of the proposed MEMS h-CDRA are investigated through the Ansoft HFSS simulation software. To validate the antenna performance, the proposed h-CDRA is fabricated and experimentally investigated. The simulation results are compared with measured data, and they are in good agreement with each other. The proposed MEMS h-CDRA is excited with coaxial probe feed, which excites TM_01δ dominant mode fields in the h-CDRA elements. The proposed MEMS h-CDRA provides wide bandwidth (≈ 120.3%) with gain of 6.45 dBi at resonant frequency (6.4 GHz). The measured gain is more than 4.0 dBi in entire operating frequency band (5.3 GHz-13.0 GHz) with monopole type radiation pattern. The bandwidth as well as gain enhancement is experimentally observed in the proposed structure. The proposed antenna has found suitable application for WLAN and WiMAX as well as X-band wireless applications.

Buried iron pipeline is an important part of urban infrastructure. In order to accurately obtain the location information of buried iron pipeline, here, we establish a forward model of magnetic anomaly in buried iron pipeline based on magnetic dipole reconstruction (MDR) method that determine four inversion parameters and two inversion objective functions. The vertical magnetic field data with different proportion noises are taken as observation values respectively to invert the parameters of underground pipeline and its location (buried depth) by using the adaptive mutation particle swarm optimization (AM-PSO) inversion algorithm. The errors of inversion and observation of vertical magnetic field are compared by substituting the inversion parameters into forward formulas. The results show that the AM-PSO inversion algorithm can accurately invert the pipeline depth, and the inversion error of the pipeline depth is less than 5%, which is acceptable in practical engineering. The inversion of the vertical magnetic field can basically coincide with the observed vertical magnetic field of the original model. At the same time, it is verified that the AM-PSO inversion algorithm is insensitive to magnetic anomaly noise data. In this study, the effectiveness of AM-PSO inversion algorithm method for pipeline depth inversion is analyzed, and an effective optimization inversion method is provided for underground iron pipeline depth inversion.

This paper focuses on the design, development, and integration of a V2X shark-fin antenna. A novel planar Electronically Switched Parasitic Array Radiator (ESPAR) antenna, operating at 5.9 GHz, is proposed. The antenna exhibits pattern reconfigurability i.e. one quasi-omni and two directive beams, low cost, reduced complexity and small dimensions. Therefore, it is considered as an ideal candidate for integrating inside a shark-fin casing. The ESPAR antenna prototype is fabricated and tested in three different measurement scenarios: (a) free-space, (b) inside shark-fin, and (c) shark-fin with ground plane. A good correlation between simulated and experimental results has been obtained. The proposed antenna involves a reconfigurable impedance matching network that is integrated in the antenna design, and thus, it demonstrates a satisfactory impedance matching for all antenna states. A considerable gain enhancement (3-4 dB) is also recorded between the omnidirectional and two directive patterns.

A novel dual band-notched CPW-fed UWB MIMO antenna with mutual coupling reduction characteristics is presented in this paper. The proposed antenna uses CPW feeding to expand the antenna bandwidth. The measured impedance bandwidth with S₁₁ < -10 dB is 137% from 3 GHz to 16 GHz. The overall size of the antenna is 46 mm × 32 mm × 1.6 mm. In order to achieve the dual band-notched characteristics, a cup-shaped branch is added to the grounding plate, and a step impedance resonator (SIR) is added to the microstrip line.By adding periodic strip branches on the back of the antenna, the mutual coupling between the two antennas is significantly reduced, which meets the requirements of practical applications. In addition, the proposed antenna has a compact size and can provide a stable radiation pattern, which is suitable for UWB communication systems.

To solve the real-time through-wall detection problem in the presence of wall ambiguities, an approach based on the kernel extreme learning machine (KELM) is proposed in this paper. The wall ambiguity and propagation effect are included in the single-hidden-layer feedforward networks, and then the technique converts the through-wall problem into a regression problem. The relationship between the scattered data and the target properties is determined after the KELM training process. Numerical results demonstrate the good performance in terms of the effectiveness, generalization, and robustness. Compared with the support vector machine (SVM) and least-squares support vector machine (LS-SVM), the KELM provides almost the same estimated accuracy but at a much faster learning speed, which greatly contributes to solving the real-time detection problem. In addition, the situations of two targets, different target radiuses, and noisy circumstances are discussed.

An all-fiber parametric oscillator which is pumped by a mode-locked Er-doped picosecond fiber laser is proposed for the generation of multi-wavelength picosecond lasing pulses. The length of a fiber-coupled optical delay line is adjusted so that the first signal wavelength is tuned closer to the pump wavelength to facilitate the generation of more lasing wavelengths. 10 orders of cascaded four-wave-mixing processes are achieved and picosecond pulses at 17 lasing wavelengths from 1264.7 nm to 1842.4 nm are demonstrated. To the best of our knowledge, this is the largest number of lasing wavelengths reported so far from a fiber optical parametric oscillator pumped with an ultrashort-pulse laser.

Space borne accurate emitter localization has become an important and indispensable part of electronic warfare (EW) systems. In this paper, a system-level approach to design space borne receiver for accurate localization of long range co-channel radars (e.g. a network of similar surveillance radars) is presented. Due to the wide frequency range of modern radar signals, the receiver should have wide instantaneous bandwidth and requires high sampling rate analog-to-digital converters (ADCs). To address this issue, we propose a receiver structure with an appropriate sub-Nyquist sampling scheme and fast sparse recovery algorithm. The proposed sub-Nyquist sampler employs a three dimensional uniform linear array (ULA), followed by a modulated wideband converter (MWC). To accurately estimate the location of the co-channel radars from sub-Nyquist samples, a novel quad-tree variational Bayesian expectation maximization (QVBEM) algorithm is proposed. The QVBEM algorithm minimizes the computational load and grid mismatch error by iteratively narrowing the search area. This is done by smart grid refinement around radars' locations. To evaluate the performance of the proposed receiver, location finding of pulsed radars is studied through numerical simulations in various scenarios. The results show that the proposed QVBEM method has a significantly lower estimation error than conventional deterministic and Bayesian approaches, with a reasonably computational complexity.

A bearingless switched reluctance motor (BSRM) has the same body structure as a switched reluctance motor (SRM), but the winding method is different. The accurate analysis of thermal characteristics is especially important for the service life and safety performance of the two motors. According to the initial design parameters, the initial size calculation equations of SRM and BSRM are given, and the ontology design parameters are obtained according to the same design goal. The two-dimensional finite element model is established, and the stator rotor iron loss is analyzed. The distribution characteristics of iron loss of SRM and BSRM are summarized. Secondly, the three-temperature field model of the motor is built, and the reasonable boundary conditions are set. The temperature distribution law of the two motors is analyzed. It is concluded that the BSRM components have lower loss and lower temperature rise under the same design target.

In this paper, the design of a miniature antenna dedicated to be implanted in a small animal and intended to work in the European UHF RFID (865-868 MHz) band is presented. One of the goals of this work is the miniaturization of the radiating element while preserving its efficiency to allow a reliable communication between an external interrogating reader and the implanted device. The radiating element is a small rectangular loop antenna associated with a dipole allowing impedance matching. The antenna has dimensions of 2.4 mm x 25.4 mm x 0.5 mm and integrates an Impinj Monza 4 chip presenting an impedance of 5.5-j74 Ohms at 868 MHz. The antenna is designed and optimized by using the ANSYS HFSS software. The obtained results show a simulated radiation efficiency of 0.7% and simulated total gain of -17.5 dBi. A prototype is realized, and RSSI measurements have demonstrated the possibility of reliable wireless communications between the implanted antenna and an external reader. In addition, Specific Absorption Rate (SAR) calculation indicates that this implanted antenna meets the required safety regulations.