Fibre Bragg Gratings (FBGs) offer several advantages including their immunity to electromagnetic fields making them excellent in situ sensors for feature extraction in electrical machines condition monitoring. However, the pre-requisite of bonding FBGs circumferentially on either the machine cast frame or stator windings can introduce undesired sensing characteristics. This is because the FBG relies on adhesives as the transfer medium for any sensed parameter between the machine and sensor. Whilst FBG sensors rely mainly on wavelength shift, an intolerably low signal-to-noise ratio will result in difficulty in measuring such shifts. As a complementary signature, differential optical power can be combined with wavelength shift to broaden the feature extraction capability of FBG sensors. This makes power level (dBm) an important sensing parameter for FBG sensors. The effect of varying number of bonding points on transmitted optical power is investigated using unstripped and stripped bare fibres as well as an actual FBG sensor. Increasing the number of bonding points beyond an optimum number has been observed to significantly attenuate the optical signal power level and quality for a given dynamic range. Hence, as the number of bonding points is increased, the level of attenuation should be closely monitored to ensure that the optimum number is not exceeded if excellent and accurate FBG sensing characteristics are to be realised.
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.
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.
In this paper, a novel wide axial ratio bandwidth (ARBW), high gain, and low profile left-hand circularly polarized [4×4] elliptical microstrip array suitable for Ku-band satellite TV reception applications is introduced. A careful study has been done to get the optimum design to be suited for these application requirements. A circularly polarized microstrip patch with two stubs opposite to each other to produce two orthogonal modes is presented. The proposed element has 1.49 GHz 10-dB return loss bandwidth (RLBW), 0.44 GHz 3-dB Axial-ratio band (ARBW), and 6.9 dBi gain. A novel substrate integrated waveguide (SIW) feeding structure is investigated. Using the advantage of the output ports phase response of the SIW feeding network, two structures have been investigated. First, a [2×2] circular array has been designed, and although it has reached a good RLBW, this structure dose not achieve the required ARBW for the above-mentioned application. Further, a compact [2×2] sequential feeding network is designed to widen the ARBW. The measurement shows a very good result with about 12 dBi gain, 14.8% RLBW, and 12% ARBW. Finally, a [4×4] duple sequential feeding array is designed to increase the gain of the antenna to about 19 dBi, with 13% RLBW and 20.7% ARBW. In addition to that, the final antenna profile is 0.0184λ.
In this paper, a wideband antenna is designed systematically based on characteristic mode analysis (CMA). The antenna consists of a rectangle, a semi-annular ring, and a microstrip line. The radiating behavior and resonant frequencies of the radiating element are analyzed by using first four characteristic modes. First two modes only have wideband behavior and are excited by CPW feeding technique. The proposed antenna is printed on a low cost FR4 substrate with a size of 35x50x1.6 mm3 and impedance bandwidth ranging from 1.6 to 3.8 GHz for the applications of GSM, DCS, LTE, and WIMAX. To validate the proposed approach, the wideband antenna is fabricated and tested. A wide impedance bandwidth of 81% with |S11| < -10 dB is achieved for both simulation and measurement results.
There are millions of people in the world exposed to weather-related land deformation hazards. These weather-related mass movement activities are most likely due to climate change, the decrease of permafrost area, the change in precipitation pattern, etc. Landslide is the most common land deformation incidents reported in Malaysia for the past few years. Therefore, Remote Sensing and Surveillance Technologies (CRSST), Multimedia University (MMU), Malaysia has developed the ground-based synthetic aperture radar (GBSAR) as a tool to monitor the high-risk area, which is prone to landslide continuously. Preliminary testing of the GBSAR has been conducted in Cameron Highland, Malaysia to verify the performance of the GBSAR and its capability of detecting landslide. However, the phase stability of the GBSAR is one of the most crucial factors that affect the detection capability of GBSAR, especially when it comes to the sub-mm measurement. This paper reports the phase stability study of the GBSAR and presents an empirical model for interferometric phase statistics.
Development and optimization of printed spiral coils have significant impacts on the efficiency and operating range for magnetic resonant wireless power transfer (WPT) applications. In this paper, the effects of different material losses (substrate and conducting coating) of printed coils are considered and experimentally studied in this paper. For the purposes of comparison and finding the dominated losses, lossy loaded capacitors with equivalent series resistances have also been investigated. A four-coil system with an external capacitor-loaded (ECL) magnetic resonant WPT system is considered, and a self-resonant coil is designed and compared. Results show that the ECL resonant coil has higher efficiency than the self-resonant coil with the same size and distance between the transmitting and receiving coils. Through observing the simulated results and analyzing experimental data, it can be concluded that the dominant cause of the decrease in efficiency of this ECL-WPT system is the strip resistive loss of coil of 57% and the ohmic loss in ECL of 37%. Meanwhile, the substrate loss significantly impacts on the efficiency of the self resonant coil. The overall measured efficiency is about 66% of the ECL coil at a distance of 50 mm when the above loss factors are considered. The measured results are in good agreement with the analysis and simulations.
This paper presents the design and analysis of a dual-band circularly polarized (CP) microstrip patch antenna for WLAN and vehicular communication applications. In this antenna, an L-shaped slot is cut, and a square parasitic patch with diagonally opposite corners cut is loaded in offset beneath to monopole antenna to realize dual band CP response with wideband response. The antenna exhibits dual band CP response at 2.45 GHz (WLAN) and 5.9 GHz (Vehicular) having 20.45% and 15.73% of simulated impedance bandwidth and 6.84% and 14.16% of axial ratio bandwidth for WLAN and Vehicular band respectively. The measured impedance bandwidth (S11 < -10 dB) is 19.43% and 12.73% for WLAN and vehicular band respectively. The antenna design is simple and fabricated using an economical glass epoxy FR4 substrate with size of 45 × 40 mm2. The measured results are found in good agreement with simulated results. The proposed antenna is analyzed using transmission line equivalent circuits, and the details are presented and discussed.
Electrical impedance tomography (EIT) is a technique for reconstructing conductivity distribution by injecting currents at the boundary of a subject and measuring the resulting changes in voltage. Sparse reconstruction can effectively reduce the noise and artifacts of reconstructed images and maintain edge information. The effective selection of sparse dictionary is the key to accurate sparse reconstruction. The EIT image can be efficiently reconstructed with adaptive dictionary learning, which is an iterative reconstruction algorithm by alternating the process of image reconstruction and dictionary learning. However, image accuracy and convergence rate depend on the initial dictionary, which was not given full consideration in previous studies. This leads to the low accuracy of image reconstruction model. In this paper, Recursive Least Squares Dictionary Learning Algorithm (RLS-DLA) is used to learn the initial dictionary for dictionary learning of sparse EIT reconstruction. Both simulated and experimental results indicate that the improved dictionary learning method not only improves the quality of reconstruction but also accelerates the convergence.
In this paper, the performance of relay selection in an energy harvesting aided mixed radio frequency (RF)/free space optical (FSO) system with transmit antenna selection (TAS) over atmospheric turbulence and pointing error is presented. The source of multiple antennas employs TAS to send information to the destination via multiple relay nodes. Also, the energy-limited source uses selection combining technique to harvest energy from multiple relay nodes. As a result, all the relay nodes act as a wireless power transmitting node as well as data receiving node. Moreover, it assumes that the RF/FSO links follow Rayleigh/Malaga (M) distributions with non-zero boresight (NB) pointing error on the FSO link. Therefore, the system outage probability closed-form expression is then derived which is utilized to obtain the system throughput. In addition, the results demonstrate the significant effect of atmospheric turbulence and NB pointing error on the system performance with multiple relays, and source transmit antenna offers the system better performance. The accuracy of the derived expressions is thus validated through Monte Carlo simulations.
This paper proposes a new method of calculating currents in three-phase overhead medium and high voltage networks by measuring the magnetic fields generated in the close vicinity of the power line conductors. A mathematical model for magnetic fields is presented in the form of second order partial differential equations that are derived from Maxwell's equation. The analysis of the magnetic field surrounding overhead conductors is performed using Finite Element Method. The least squares method is used for the formulation of equations for estimating currents from the measured magnetic fields for each phase. A computational program for detail analysis is developed in MATLAB. A plan for measurement points is developed for triangular arrangement of conductors. Field measurement with increased number of measuring points gives better results than those with the single points.
In this paper, we consider a MIMO wiretap system in wireless sensor networks (WSNs), where the confidential signal sent to the legitimate receive (Bob) may be eavesdropped by the eavesdropper (Eve). Assuming that only partial channel state information (CSI) can be obtained by the transmitter, we consider both worst case (WC) and outage-constrained (OC) robust secrecy optimizations. To solve the WC design, we propose to linearize these logarithmic determinant terms. After linearization, we tackle the CSI uncertainty using the Nemirovski lemma. Then, an alternating optimization (AO) algorithm is proposed to solve the reformulated problem. On the other hand, to solve the OC design, we transform the probabilistic constraint into safe and tractable reformulation by the Bernstein-type inequality (BTI) and large deviation inequality (LDI), and an AO algorithm is proposed. Numerical results are provided to demonstrate the performance of the proposed scheme.
Greater design flexibility and newer miniaturization techniques are highly sought after by the commercial antenna industry and researchers. Micro-Strip Patch Antenna (MSPA) is finding huge applications in various fields of communication. In the present paper, the novel idea of Double-Elliptical Micro-strip Patch Antenna (DEMPA) is proposed for antenna miniaturization and higher design flexibility. The Double-Elliptical Patch (DEP) is made as the combination of two half-elliptical patches having the same minor axis and different semi-major axes or the same major axis and different semi-minor axes. A DEP with different lengths of horizontally arranged semi-major axes and centrally given feed was considered here. The length of semi-major axis for right half-elliptical patch was varied while keeping the length of semi-major axis for left half-elliptical patch fixed. Design of DEMPA was carried out using Ansoft HFSS software, and the antenna has been fabricated and tested. The measured results were in good agreement with the simulated ones. The percentage reduction in effective patch area was found to be 8.33 for DEMPA compared to the corresponding elliptical patch antenna. The DEMPA covered the entire frequency range of Ultra Wide Band (UWB). With this novel shape, greater design flexibility along with miniaturization is achieved. The axial ratio analysis showed that the resulted antenna was of linear polarization.
A novel compact Ultra-Wideband Multiple Input Multiple Output (UWB-MIMO) antenna with enhanced bandwidth is proposed. The bandwidth of the designed antenna ranges from 1 to 30 GHz which covers L, S, C, X, Ku, K bands and some part of Ka-band. A square slot & inverse L-shaped strip is used to improve the isolation amid antenna elements. The suggested antenna achieves Mutual Coupling and Envelope Correlation Coefficient below -17 dB and 0.15 respectively. MIMO performance parameters like Mean Effective Gain is around 0 dB, and Total Active Reflection Coefficient is less than -10 dB. The Channel Capacity Loss and Effective Diversity Gain are less than 0.3 bits/s/Hz and 9.2 dB, respectively. The radiation efficiency of the designed antenna is around 80% over the complete frequency range. The overall dimensions of designed antenna are 27× 17 × 1.6 mm3.
The magnetic field distribution of an axially magnetised cylinder with elliptical profile is analytically modelled and analysed in this paper. An accurate and fast-computed semi-analytical model is developed, based on the charge model and geometrical analysis, to compute the three components of the magnetic field generated by this elliptical cylinder in three dimensional space. The accuracy of the model is verified using Finite Element Analysis. The analytical expressions are efficient for calculating the implementation of the magnetic field, taking less than one millisecond to execute on a modern PC. Using the fast-computed analytical model, the distribution of the magnetic field of an axially magnetised cylinder with different elliptical profiles is studied and compared with that of a circular cylinder. The variations in magnetic field strength of axial, azimuthal and radial components can be used in novel sensing applications. The derived analytical model can be extended to calculate the magnetic field of arc-shaped elliptical and circular cylinders with axial magnetization, which can be used in Halbach arrangements.
A planar wideband circularly-polarized (CP) antenna array is designed for an X-band CubeSat. The design is a two-level sequential phase architecture, consisting of a 4 × 4 element array composed of sequentially rotated of 2 × 2 subarrays. Each subarray consists of sequentially rotated 2 × 2 antennas using metasurface. These antenna elements are incorporated with a two-level sequentially rotated phase network in order to obtain wideband characteristic and high gain. The final prototype with a size of 100 mm × 100 mm × 2.032 mm yields a measured |S11| < -10 dB bandwidth of 50% (6-10 GHz) and measured axial ratio < 3-dB bandwidth of 40.7% (6.45-9.75 GHz). Additionally, the proposed design achieves a good broadside right-hand CP radiation with a peak gain of 17.0 dBic, 3-dB gain bandwidth of 20.4% (7.5-9.2 GHz), and radiation efficiency of > 82%. With these features, the proposed antenna can be compatible with any CubeSat standard structure, as well as other small satellites.
In this paper, a novel passive antenna cancellation technique for a full-duplex system is presented. This includes three patch antennas with a developed coupler that are constructed and integrated with the feed network to reduce the self-interference signal without the need for other components, thus achieving a complete antenna cancellation method. Computer Simulation Technology (CST) microwave studio is utilized to simulate the design model. A prototype was fabricated and tested practically to validate the proposed design. The computed results are compared with measurements. The proposed technique provides up to 68 dB cancellation at the operating frequency 2.45 GHz, and this decreases to 40 dB at 70 MHz bandwidth, and to 36 dB at 100 MHz bandwidth.
Cellular technology is moving towards its 5th generation (5G) that will employ millimeter wave (mmWave) frequencies in the attempt to offer more spectrum and multi-Gigabit-per-second (Gbps) data rates to mobile devices.Various unfavorable propagation phenomena affect mmWave communications, rain attenuation being the most severe one. Various rain attenuation prediction models can be taken into account in the design of terrestrial links based either on cumbersome statistical regression, when sufficient local experimental data are available, or on analytical models where only local rain rate measurements are provided. In this paper, a new prediction method for the rain attenuation is proposed based on a bivariate model for the numerical estimation of the effective path length of a millimeter wave terrestrial link and on Weibull distribution forthe representation of the point rainfall rate statistics. To validate the proposed prediction method, the actual data taken into account are extracted from experiments included in the databank of ITU-R SG3.The numerical results obtained show a significant improvement of the prediction accuracy compared to existing prediction models.
A compact ultra-wideband (UWB) antenna with tunable band notched characteristics is proposed. Varactor loaded, two via edge located (TVEL) and fractal electromagnetic band gap (EBG) structures are designed for tunable band-notched characteristics. The varactor diode near the TVEL EBG tunes the band notch frequency for WiMAX (2.8-4.0 GHz) band, while another varactor near fractal EBG structure tunes band-notch frequency for WLAN (4.7-6.2 GHz) band. The varactors are independently controlled to achieve WiMAX and WLAN notched band. Notch frequencies can be continuously tuned by varying the bias voltage across the varactors. The proposed antenna of 24×24 mm2 dimensions is fabricated on an FR4 substrate. A good agreement between simulation and measurement results is obtained. A continuous band notch tuning from 2.8 to 4.0 GHz and 4.7 to 6.2 GHz is obtained using varactor diodes having capacitance in a range of 0.497-2.35 pF.
A novel and effective architecture of tunable multiband balanced bandstop filter (MBBSF) is introduced for the first time in this paper. Each symmetrical bisection of the proposed branch line structure consists of K series cascaded tunable N-band sections to realize a reconfigurable K-th order N-band response in differential mode (DM) operation. The main advantage lies on the fact that all these N bands can be tuned simultaneously or each band independently. Moreover, it maintains a high common mode rejection ratio (CMRR) for all the tuning states by incorporating open stubs in the symmetrical plane of the balanced structure. To validate the proposed topology, a balanced dualband tunable BSF is designed where the two DM stopbands tune in the range of 1.16 GHz-1.29 GHz and 1.6 GHz-1.76 GHz, respectively. The lower and the upper bands maintain a constant absolute bandwidth (ABW) of 115 MHz and 135 MHz, respectively, and stopband rejection is better than 20 dB for each band. The fabricated prototype occupies an area of 0.31λg2, and the experimental results show a good agreement with the simulation results.
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