In this paper, a design of a low profile cavity backed antenna consisting of bilateral slots is developed for generating two frequencies. Here, the whole antenna including substrate integrated waveguide (SIW) cavity is constructed from only one substrate with the height of 0.026λ0. The long transversal slot at the ground plane is excited by TE210 mode of the cavity and produces one hybrid mode resonance at 9.85 GHz. When the short transversal slot cut is incorporated in the top portion of the cavity, TE310 mode is perturbed, which results in generating an additional hybrid mode resonance at 14 GHz. Both these hybrid modes help to create a dual-band response. A sample of the proposed design is fabricated, and it has been verified experimentally that the bandwidths of the proposed design are 530 MHz (5.48%) and 440 MHz (3.15%) at lower and higher resonant frequencies, respectively. The antenna renders measured peak gains of 6.62 dBi and 6.44 dBi at 9.85 GHz and 14 GHz, respectively. The cross-polarization level of maximum -20 dB and same polarization planes are obtained at both the operating frequencies.
A rectangular Dielectric Resonator Antenna (DRA) four element Multiple in Multiple Out (MIMO) is proposed for 5G application, and each element is supplied with slot-coupled microstrip feed. The entire construction has a dimension of 20 mm × 40 mm. Four Dielectric Resonators are mounted exactly above the slot. In order to improve the isolation, metamaterial is printed on top of the dielectric resonators, which move away the solidest coupling fields. As the metamaterial structure interacts with the electromagnetic fields, field distributions are disturbed which results in reduction of coupled fields. Since the metamaterials are printed on top of the dielectric resonator, the proposed antenna structure has simplest and compact design. The proposed structure is operating with an impedance bandwidth of 2.23 GHz with operating range from 26.71 GHz to 28.91 GHz, which covers the 28 GHz (27.5 GHz-28.35 GHz) band allotted by Federal Communications Commission (FCC) for 5G application. With all four-port excitation, the proposed structure shows a broadside radiation pattern with gain above 7 dBi in the entire operating bands. The Envelope Correlation Coefficient (ECC) for operating bands is within the target value. They are designed and fabricated to validate the proposed antenna. The simulated and measured values are nearly equal, which means that the proposed MIMO DRA is the right choice for mm-Wave 5G implementation.
This paper proposes a novel electromagnetic band gap (EBG) structure based on a dual-layer dual-patch unit (DLDP-EBG) cell to improve isolation and decrease envelope correlation between MIMO slot antenna array elements. A wideband MIMO slot antenna array operating in the frequency range of 4.2-6.5 GHz (43%) is deployed. The antenna array is based on slotted rectangular microstrip radiating elements printed on the top surface of two stacked FR4 substrates to widen the array impedance bandwidth. A 2 x 7 dual-layer DLDP-EBG unit cell is inserted between the array elements to reduce the mutual coupling and detect the individual beams of each antenna in opposite directions. An isolation improvement of up to 56 dB is maintained throughout the working bandwidth of the antenna, when the EBG is inserted. Also, the DLDP-EBG unit cells reduce the envelope correlation coefficient by 5-30 dB across the whole operating bandwidth by detecting the radiation beams of the individual antenna elements in opposite directions. The MIMO array gain and radiation eciency have been improved after using the EBG structure due to the reduction in mutual coupling and surface wave mitigation between the array elements. The proposed low-prole MIMO slot antenna array is the first in literature to exhibit such wideband isolation improvement, gain enhancement, and correlation reduction behavior simultaneously.
Tunable negative electromagnetic properties: permittivity, permeability, and refractive index, in mimic Chlorophyll metamaterial structures in the X- and Ku-band regimes are theoretically and numerically demonstrated. A very broad negative permeability covering the majority of the X- and Ku bands, from 8 GHz to 16 GHz, is observed, while five negative permittivity bands are found within the same range. The two aforementioned properties result in a broad, greater than 25% bandwidth, low-loss negative-refractive index transmission band. These negative electromagnetic properties can be effectively tailored within the low-loss multi-transmission and the high-loss multi-absorption bands in the operating frequency range by modifying the structure's tiller part or the artificial hydrophobic or Phytol tail. By focusing either on the transmission or the absorption bands, these passive always-on bio-inspired metamaterials could be utilized in microelectronic, communication and photonic, and optic devices.
To predict the residual electric field inside an electromagnetic (EM) shield under illumination of different HEMP waveforms, a method based on NARX neural network is proposed in this paper. The model can be established from input-output data of EM shield without knowing enclosure and internal structural details. To evaluate the precision of the prediction method, two error criteria based on energy and field amplitude are provided in this paper. As a numerical example, the double exponential pulse with 10% to 90% rise time of 2.5 ns, the pulse width at half maximum of 23 ns, and the corresponding residual electric field are taken as the training data. The EM simulation is used to establish the model of residual electric field inside the shield. The NARX neural network is then built and trained. Other double exponential pulses, with different rise times and pulse widths, and their residual field are taken as the checking data. The results show that the error of the prediction method is sufficiently small for actual use.
In this article, the authors present a hepta band metamaterial inspired hybrid fractal octagonal shape antenna for wireless applications. Multiband characteristics in the proposed design are achieved by hybrid fractal form of Moore curve and Koch curve with metamaterial loading. A well matched impedance bandwidth (S11 ≤ -10 dB) is accomplished at seven microwave frequency bands Upper L band (1.93~2.08 GHz), S band WiMAX (3.3~3.7 GHz), C band WLAN (5.4~5.9 GHz), C band IEEE INSAT application (6.5~7.2 GHz), X band terrestrial broadband, space communication and Radio Navigation (RN) application (8.51~11.05 GHz), Lower Ku band direct broadcast satellite service (12.2~12.7 GHz), and Middle Ku band satellite communication operating band (14.73~15.84 GHz) covering various wireless applications. The antenna achieves hexa/penta band characteristics during switching ON/OFF state of PIN diode placed between the Moore curve structure (attached with centered SRR cell) and feedline. Radiation patterns are found in stable forms at all the resonant frequencies. Measured results of the proposed design are compared with simulated ones indicating good agreement between them.
This article presents a compact size and high isolation 2×2, Multi-Input Multi-Output (MIMO) antenna for Industrial Scientific and Medical (ISM) band and 5G lower frequency band of 5G applications. Mutual coupling has been a great challenge in these applications. To improve isolation between elements of 1×2 MIMO antennas, a mushroom-shaped electromagnetic bandgap (EBG) and a fractal shaped EBG have been investigated. The overall size of the proposed antenna is 38.2×95.94×1.6 mm3 with inter-element spacing (edge to edge) of 0.140λ. The proposed antenna has been designed, simulated, fabricated, and tested. The resulting outcome shows that the antenna operates in the band of 2.43-2.50 GHz and radiates in TM10 mode. By using fractal shaped EBG, isolation of -24.67 dB is achieved. Apart from isolation, other performance parameters of the MIMO antenna are verified. The proposed antenna is suitable for weather radar, surface ship radar, satellite communication, and wireless local area network (WLAN) applications.
Electromagnetic Band Gap (EBG) structures can be employed near the feed line of a UWB monopole antenna, to reject the already existing narrowband radio signals operating within the spectrum of an Ultra Wide Band (UWB) antenna. Multiple EBG structures are required to reject multiple interfering bands. However, since the ground plane of a monopole antenna is limited, there is a need for compact EBG structures. This paper presents the application of a Two Via Slot (TVS) EBG to reject the interfering upper Wireless Local Area (WLAN) band (5.725 GHz-5.825 GHz) from the spectrum of a fork-shaped UWB monopole antenna. The simulated results demonstrate that the TVS EBG gives better performance in terms of higher and sharper Voltage Standing Wave Ratio (VSWR) value at the rejection band while occupying least ground plane area than Conventional Mushroom Type (CMT) EBG, Edge Located Via (ELV) EBG, slotted-patch ELV EBG, and semi-circular EBG. The proposed design is fabricated and measured. The measurement results prove that the antenna successfully achieves wide impedance bandwidth from 3 GHz to 12 GHz while rejecting the frequencies from 5.4 GHz to 5.9 GHz.
A simulation tool to characterize the radar cross section of a pedestrian in near field is presented in the paper. The tool has been developed in order to predict and optimize the performance of the short-range radar systems employed in autonomous vehicle operations. It is based on an analytical model which joins the modeling of the human body with the theory of the physical optics. Our studies first focused on the implementation of the electromagnetic code where the human body, the radiation properties of the antenna and the scenario to be analyzed have been analytically expressed. Then, the proposed model has been validated in terms of accuracy comparing simulated and experimental data regarding the radar cross section of a metal sphere and of an adult, in the frequency range 23-28 GHz. In the end, an evaluation of the performance in terms of required computer memory and execution time has been carried out, comparing the proposed simulation tool with other numerical computational methods.
This paper introduces a balanced (differential) multiband reconfigurable (tunable) bandstop filter (BSF) using all lumped elements. The main features of the design include its ultra-compact size as well as flexibility to control any frequency band independently in terms of both center frequency and absolute bandwidth (ABW). In the proposed structure, the corresponding non-resonating nodes (NRN) of the symmetrical bisections are connected to N number of LC π-circuits (N-band cell) through capacitors. Again, in each symmetrical bisection, K number of NRNs are series cascaded through LC π-circuits. This results in a Kth order N-band stopband (notch) response in differential mode (DM) operation whereas provides a passband response when excited by a common mode (CM) signal. Reconfiguration of any DM stopband is obtained by using tunable capacitors for the corresponding LC π-circuit in each N-band cell and also, for its coupling capacitors to the NRNs. To validate the proposed topology, a dualband differential tunable BSF is designed and fabricated where both DM stopbands are controlled independently in the range of 1.16 GHz-1.32 GHz. Also, the bandwidth of each band is varied independently by 20-50 MHz without affecting the other band. At any tuning state, DM stopband rejection for each band is found to be ≥19 dB, resulting in a minimum CMRR value of 19 dB. The fabricated prototype occupies an area of 0.13λg×0.04λg (21 mm×7 mm) where λg is the guided wavelength at the center frequency of the entire spectral range, and the experimental results show a good agreement with the simulation results.
A meandered line multi-resonator design is proposed for a chipless Radio Frequency Identification (RFID) tag. The tag is equipped with a set of identical resonant elements and two orthogonally polarized monopole ultrawide band (M-UWB) antennas. The proposed multi-resonator design is realized on an FR-4 substrate (εr = 4.4; tanδ = 0.01) in a surface area of 13 x 17 mm2, occupying a coding density of 4.52 bits/cm2 by encoding 10 bits of data. The bit is encoded using absence/presence coding and frequency shift coding technique. The data can be read and transmitted from the multi-resonator structure through the orthogonally polarized M-UWB antennas operating in the frequency range of 2 GHz to 4.5 GHz. The span of the meandered line multi-resonator design is 13 mm x 17 mm. The tag is designed using ADS software and tested using vector network analyzer (VNA).
Propagation mechanisms for short range, low altitude conditions are reviewed for their use in communications of unmanned aerial vehicles (UAVs). This study is based on measurements conducted in an obstacle-free area. The testbed is made up of a testing UAV (in particular a drone) and a set of four ground station terminals (GSTs) located in a football field; the antenna heights of radios (onboard the drone and GSTs) are equal to 1.4 m and the maximum distance between them is 50 m. Under these conditions, a plane earth geometry is well suited, and therefore the two-ray propagation model is considered. Measurement results for a radial configuration of the drone with respect to a ground station follow the trend of this model, but with a shift, which is attributed to the scattering from the grass. Then, an adjusted two-ray model is proposed for which experiments report good results. For another configuration where the drone has different positions in a square area of 30 × 30 m and there are four ground stations in the corners of the square, the general trend of the power decay of measurement results follows this model, but in some positions a difference around it is found even for locations at the same distance drone-GTSs. This behavior is attributed to the interaction of the print circuit board to the radiation characteristics of the antenna used in the radios. Thus, this effect is also analyzed by simulations, whose results show a deformation of the antenna radiation pattern, concentrating the energy in a certain direction and reducing it in another.
The paper presents a method of extracting noise source impedance of electrical equipment under working condition. Firstly, based on the theory of two-port network, the measurement method of noise impedance is analyzed theoretically, and the injection probe and receiving probe are calibrated by two known resistors. No special calibration fixture is needed to calibrate the injection probe and receiving probe. Secondly, the port structure of the noise impedance measurement method is analyzed, and the noise source impedance is calculated by using the theory of microwave transmission. Compared with the traditional method, this method does not require calibration fixture and simplifies the experimental process. Finally, passive devices and active systems are tested respectively, and the experimental results show that the method is effective and feasible.
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.
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.
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 TM01δ 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.