This paper presents a single stage 2-way Wilkinson Power Divider (WPD) suitable for Internet of Things (IoT) low frequency applications in the band from 200 MHz to 1 GHz. It is realized using a meandered line, and an open shunt stub matching network is added to get a compact structure. Moreover, a Vertical Periodic Defected Ground Structure (VPDGS) is added below each arm in order to improve the performance at the center frequency without adding extra length to the divider. The size of the proposed power divider is 30 × 15.3 mm2 (0.082λg × 0.041λg). The fabricated power divider achieves a fractional bandwidth of 107%, an input return loss of better than 10 dB, an output return loss of 20 dB, an isolation of better than -10 dB and maximum exceeded insertion loss of 0.9 dB. The proposed compact power divider is implemented on Rogers RT/ Duroid 5880 with thickness 0.254 mm in order to bend on any conformal surface.
In this study, a novel, low-profile, polarization-insensitive, and compact band-notched absorber is presented. The objective of the proposed work is to design a miniaturized FSS-based band-notch absorber with high angular stability exhibiting strong operational bandwidth of 130.5% (1.7 GHz to 8.09 GHz). The absorber consists of a reflecting band sandwiched between two absorption bands. The absorption bands lie in between 1.7 GHz to 3.75 GHz and 5.65 GHz to 8.09 GHz respectively. The strong reflection band with 1 dB insertion loss lies in the frequency range from 4.25 GHz to 5.12 GHz. The proposed absorber structure comprises multiple layers with a metal sheet at the bottom. Total thickness of the band notch absorber is only 0.064λL (where λL is the wavelength corresponding to the lowest frequency of operation). The top layer comprises a modified swastika frame metallic structure loaded with lumped resistors placed on a dielectric substrate. Two air layers, one below the top layer and the other above the bottom metal, are inserted. In between two air layers a dielectric layer with a metallic rectangular ring pattern is positioned. The four-fold symmetrical structure results in polarization insensitive response. The equivalent circuit of the proposed structure is developed for understanding the underlying working principle of band notch absorbers. The surface current distribution has also been studied. The designed absorber is fabricated, and measurements are done in an anechoic chamber. The measured results show good agreement with the simulated ones.
In active phased arrays, T/R module performance drifts due to active components' aging and thermal effect. Hence periodic online field calibration is required during the deployment of a radar system. This paper presents an innovative design of a precise and consistent calibration network consisting of a buried leaky coaxial cable (LCX) and a calibration switch network (CSN) for fast periodic field calibration of an active phased array. In the antenna plate, leaky coaxial cables are buried within the wall of the cavity-backed antenna to realize calibration lines. A 1:30 way Wilkinson power divider/combiner is realized as a calibration switching network for simultaneous excitation of multiple calibration lines to characterize multiple radiating elements in the active array. An S-Band (3.3 GHz ± 200 MHz) experimental active array with 64T/R modules is configured and tested in the near-field test range (NFTR) to demonstrate the performance of the proposed calibration network. Simultaneous excitation of multiple radiating elements significantly reduces array calibration time and provides more flexibility to other multifunction radar functions. The availability of multiple receivers and non-overlapping RF beam forming networks in the radar system limits the improvement factor in array calibration time mentioned in this paper.
This study aims to develop and evaluate the multibeam one-third Radial Line Slot Array (RLSA) antennas. The various techniques used include: a) slot implementation on the background surface for the design of multibeam, b) cutting the full circle of RLSAs for the simplification of the antenna size, and c) slot deletion for the formation of bandwidth. Approximately 40 multibeam one-third RLSA models were designed and simulated, with the best being fabricated and measured to verify the simulation. The results showed that the antenna had symmetrical beams regarding the gain, direction, and beamwidth at 9 dBi, 20 and 160°, as well as 38°, respectively. The antenna also had a low reflection of -22 dB at the centre frequency of 5.8 GHz, with a broad bandwidth of approximately 1.2 GHz, which was highly sufficient for Wi-Fi application. The gain of 9 dBi was 3 dB lower than that of a simulated single-beam antenna, which was suitable for the theory of splitting. Based on these findings, the agreement between measurement and simulation verified the design of the antenna.
This paper presents the design, co-simulation, and measurement of a two-stage broadband-cascaded low noise amplifier (LNA) using resistive terminated architecture. This architecture extends the bandwidth of a low-noise amplifier while maintaining a low NF and high flat gain S21. The LNA is designed with planar technology and mounted on an FR4 substrate. The used InGaAs HEMT MGF4918D transistor from Mitsubishi technology has very low noise and operates up to 18 GHz. The reflection coefficient results of the studied LNA are lower than -10 dB. The stability is unconditional over the entire operating band. The measured gain is 14 dB ± 0.75 dB with a minimum NF noise figure of 2.9 ± 0.4 dB. The group delay is 0.605±0.145 ns. The 1 dB compression point is 10.16 dBm, and the third order input intercept point IIP3 is 14.25 dBm. Two-stage cascaded LNA has a total power consumption of 164 mW and occupies an area of 7x1.3 cm2.
This paper presents the design and practical implementation of a wideband spring textile (WST) antenna for wearable communications. The antenna is designed on a felt substrate having a compact dimension of 32 × 42 × 3 mm3 (0.38λg × 0.5λg × 0.036λg). This antenna operates in the 3.14 to 5.45 GHz frequency range, has a bandwidth (BW) of around 2306 MHz, and has a peak realized gain of 6 dBi at 3.5 GHz. Due to a broad frequency coverage, this antenna can be used in a wide range of wireless applications, including 5G and IoT. The proposed design is analyzed in terms of reflection coefficient, radiation pattern, efficiency, gain, and surface current. Using the same electromagnetic simulation software, both characteristic mode analysis (CMA) and the method of moments (MoM) are applied in the design process. The simulated results on a human chest phantom demonstrate the -10-dB impedance bandwidths of 1461 MHz. The antenna prototype is fabricated for verification, and the simulated and measured results demonstrate that the proposed antenna is suitable for wideband on-body applications given its low-profile implementation and mechanical flexibility.
This article presents the design of the dipole antenna structure in combination with a square electromagnetic band gap (EBG), to detect child trapped in carsuse the 750 MHz frequency range, which responds to the most human movement detection. The antenna structure has been designed on a copper plate with a thickness of 0.297 mm and polyester mylar film. The baseplate has a thickness of 0.3 mm, dielectric value 3.2. By design, the dipole antenna is the size as 201.56x12.5 mm2 and a 18x5 units square Electromagnetic Band Gap (EBG) is the size as 254.64x71.86 mm2. The results of the measurement showed that the bandwidth impedance in the operating frequency range was 4.78% (735-771 MHz) with a gain of 6.33 dBi, and has an omnidirectional signal. The dipole antenna has the best distance between the EBG plates 30 mm. When being examined at a distance of 500-1,600 mm, it is the most effective at an average signal strength of approximately 0.032 mW in every time there is movement of the human in the car.
In this paper, a new fast and accurate method, the Flux Integral Path (FIP) method, is proposed for switched reluctance motor (SRM) to analyze the iron loss. The magnetic flux generated by the stator poles is integrated over a period of time, then, the eddy current loss and the hysteresis loss of the whole SRM can be directly calculated by analyzing the path distribution of the flux closed loop without dividing the motor into four blocks (stator pole, stator yoke, rotor pole and rotor yoke). The concept of flux flow is introduced to calculate the eddy current loss, and the piecewise linear fitting of flux density curve in the period is used to approximate the differential and simplify the hysteresis loss calculation. The FIP method can be well applied to non-sinusoidal and nonlinear magnetic density of SRM because of the combination of Finite Element Analysis (FEA) simulation. Furthermore, the loss separation model and the Fast Fourier Transform (FFT) method were compared with the FIP method of the iron loss calculation, and the 2D FEA simulation results were used to verify the method proposed in this paper.
Caves are a vital environment with an understudied propagation characteristic to date. In this paper, we investigate the propagation environments of three tourist caves in Malaysia at 900 MHz, 2.4 and 5.8 GHz. Path loss exponents are derived from measurement data for line-of-sight (LoS) and non-line-of-sight (NLoS) sections for vertical-vertical (VV) and horizontal-horizontal (HH) polarizations. Channel fading effects are subsequently analyzed. Beyond the conventional method of computing the path loss exponent values, machine learning is also incorporated into the processing of data for yielding optimum results. The findings of this work lay a good foundation towards a greater understanding of the propagation scenarios in natural tourist caves, and they help towards establishing reliable wireless communications inside such environments.
In this paper, a novel compact high-gain multi-layer dielectric resonator antenna for ultra-wideband applications is designed and fabricated. The proposed antenna employs a new technique to make a notch-band for the frequencies within UWB. This technique helps avoid any interference for bands like WLAN and X-band for satellite applications. In this design, several notch bands can get at different frequencies by changing the length of slots. The operating bandwidth of this antenna is between 4.8 GHz and 11.31 GHz with -10 dB return-loss and maximum gain of 6 dBi. Finally, the proposed antenna is fabricated and measured to validate the simulation results. The simulation results are obtained by two different simulators; CST Studio suite TM 2020 and HFSS 15 to ensure the validity of the design results before fabrication. The fabricated antenna is measuredusing Agilent R&S Z67 VNA. There is a good agreement between the simulation and experimental results.
A high-precision and high-efficiency reduced-dimension direction of arrival (DOA) estimation algorithm based on an L-shaped array for the problems of large computation and high cost of achieving two-dimensional (2D) DOA estimation by 2D multiple signal classification (MUSIC) algorithm under various complex arrays. The algorithm makes full use of the structural characteristics of the L-shaped array to decompose the uniform L-shaped array into two uniform linear arrays. These two arrays are respectively searched in one-dimension (1D) to estimate the angles between the source and the x-axis and y-axis, and then the 2D DOA estimation is obtained according to the geometric relationship, which greatly reduces the amount of computation. Furthermore, the algorithm increases the utilization of noise subspace information, which not only realizes the automatic pairing of direction angle and elevation angle, but also improves the estimation accuracy. In order to further reduce the complexity and improve the estimation performance, this paper also puts forward the root finding method instead of 1D search, and uses a fast angle matching method to accurately match angles. Simulation results show the feasibility of the proposed algorithm.
In this work, the design of a high sensitivity hydrostatic pressure sensor based on one-dimensional photonic crystal (1DPC) containing polymeric materials has been proposed and investigated, theoretically. The proposed structure consists of alternate layers of polystyrene (PS) and polymethyl metahacrylate (PMMA) with a defect of layer of PS, PMMA and air, respectively, in the middle of the PC structure. The sensing principle is based on the shift in the peak of transmitted wavelength when the hydrostatic pressure is applied on 1DPC. In order to obtain the transmission spectrum of 1DPC structure transfer matrix method (TMM) has been used. From the analysis it is found that with the increase in hydrostatic pressure transmission (or resonance) peak shifts towards the lower wavelength side with respect to the center wavelength. The average sensitivity (Δλ/ΔP) of the proposed sensor is found about 0.948 (nm/MPa) with polymer defect and 0.92 (nm/MPa) with air defect in the mid-IR frequency region, and the applied pressure range is 0 to 200 MPa.
The study of the thermal effect caused by exposure to electromagnetic fields is a focus of this research. To quantify the induced current and temperature distribution in the human body an assessment tool for the frequency range of 50 Hz to 110 MHz has been developed. The major contribution consists of providing a quantitatively accurate and relatively simple model. The formulation of the problem is based on a simplified cylindrical representation defined by the anatomical parameters of the human body. The bio-thermal modeling is carried out in two stages. Firstly, the electromagnetic analysis is based on the transmission lines (TL) theory. Secondly, a thermal modeling based on the thermal networks model (nodal method) is approached. This allows us to quantify the corresponding thermal gradients in the human body.
In this paper, a compact and highly sensitive refractive index plasmonic sensor, based on a metal-insulator-metal (MIM) waveguide coupled to double hexagonal ring-shaped resonators in the mid-infrared range, is proposed and analyzed using the finite-difference time-domain (FDTD) method embedded in the commercial simulator R-soft, where it has been found that the transmission peaks and dipspositions can be easily manipulated, by simply adjusting the structural parameters of the proposed design, such as the inner side length and the distance between the centers of the two hexagonal ring resonators. So, these parameters have a key role in the sensor's performances, and it is clearly noticed from the results, where a linear link between the refractive index of the material under testing and its wavelength resonances was established. Furthermore, the maximum achievable linear sensitivity was S = 4074 nm/RIU, with a matching sensing resolution of 2.45 x 10-6 RIU; the temperature sensitivity is around 1.55 nm/°C; and the highest linear sensitivity is S = 3910 nm/RIU in 0-200 g/L glucose concentration, making this proposed sensor an attractive one, to be implemented in high-performance nano and bio-sensing devices.
Doppler Ultrasound as the gold standard for noninvasive arterial pulsation monitoring has limitations such as dependency on the operator and absence of acoustic window in some patients. Recently, mm-wave has been propounded as an alternative modality for biomedical diagnostics. However, heartbeat monitoring using mm-wave modality has been experimentally investigated only for external carotid artery, and its usage for deeper arteries has not been proved, yet. This study investigates the feasibility of mm-waves in the monitoring of non-superficial arteries. A continuous-wave (CW) reflectometer sensor is used for sensing pulsations exploiting the Doppler effect. The artery mimicking tube passes through an artificial agar-oil skin phantom. A peristaltic pump circulates the liquid through a tube. An antenna is placed in direct contact with the phantom without any coupling liquid. First, we investigate the optimum frequency of the given antenna in its impedance bandwidth [16 GHz-20 GHz]. Using the optimum frequency, the pulsation of an ar-tery with a 1.6 mm diameter, placed in the depth of 16 mm, and has less than 0.02 mm radial oscillation amplitude was easily detectable.
A study is presented of several types of nondiffracting and slowly diffracting spatiotemporally localized waves supported by a simple dielectric medium moving uniformly with speed smaller or larger than the phase speed of light in the rest frame of the medium. The Minkowski material relations are not independent in the case that the speed of motion equals the phase speed of the medium; hence, the electric displacement and magnetic induction vectors cannot be uniquely determined from them. Following, however, a waveguide-theoretic approach, separate equations can be written for the longitudinal and transverse (with respect to the direction of motion) electromagnetic field intensities. The fundamental solutions associated with these equations provide a uniform transition between the cases of ordinary and Čerenkov-Vavilov radiation. The equation satisfied by the longitudinal field components in the absence of sources is examined in detail. In the temporal frequency domain one has an exact parabolic equation which supports accelerating beam solutions. The space-time equation supports several types of nondiffracting and slowly diffracting spatiotemporally localized waves. Comparisons are also made with the acoustic pressure equation in the presence of a uniform flow.
In this paper, the optimized results of multi-beam forming for an active phased array antenna are presented. In the case of a horn radiator, to implement equal main beamwidths and a low side-lobe level in the principal planes, a circularly polarized dual-mode horn antennawith the gain over 14.5 dBi is designed and fabricated at the Ka-band, which is composed of a conical horn, polarizer, and transducer. In the case of multi-beam forming, when several main beams are simultaneously generated within a limited scanning range, large side-lobes can be observed among the main beams. To overcome this phenomenon, an evolutionary technique, such as a genetic algorithm is applied to the optimization of a multi-beam pattern. It is shown that the proposed method can significantly reduce the outer side-lobe level as well as the inner side-lobe level of the simultaneous multi-beam pattern.
Compared to crystalline silicon solar cells, thin-film solar cells are inexpensive, but a weak absorption of sunlight at a longer wavelength is a significant issue. In this perspective, an efficient light trapping mechanism is needed to facilitate the light-guiding in enhancing light absorption. This paper presents a theoretical investigation of ultrathin amorphous silicon (a-Si) solar cells using the rigorous coupled-wave analysis (RCWA) method. We noticed broadband light absorption of the designed solar cell due to an efficient light trapping geometry. Our proposed design is composed of anti-reflection coating (ITO), an absorbing layer (a-Si), a back reflector (Ag-substrate), top-indium tin oxide (ITO), and bottom-silver (Ag) nanogratings. Using an Ag-back reflector with diffraction gratings demonstrated the improved diffraction and scattering of light, which enhanced light absorption within a 50 nm thick absorbing layer. Compared to the reference solar cell, the proposed ultrathin solar cell endorsed the enhanced photovoltaic conversion, i.e., 19% and 23%, corresponding to the transverse electric (TE) and magnetic (TM) polarization conditions. Furthermore, we explore the investigations of light absorption, current density, field distributions, reflection, transmission, and parasitic losses for the optimal design of ultrathin film (a-Si) solar cells.
Generalized Lorentz-Mie Theory (GLMT) provides analytical far-field solutions to electromagnetic (EM) scattering of an aggregate of spheres in a fixed orientation. One of the computational codes that implements the GLMT calculation is that provided by Xu, dubbed GMM which returns EM responses such as the extinction cross section, σext, given the information of incident wavelength, particle arrangement, the common radius, and reflective indices of the aggregate. We have attempted to represent the GMM code in the form a neural network dubbed NNGMM. The NNGMM obtained was stress tested and systematically quantified for its accuracy by comparing the σext predicted against that produced by the original GMM code. The σext produced by the NNGMM for arbitrary aggregates at random wavelength yielded a good fidelity with respect to that calculated by the GMM calculator up to an R-squared value of above 99% level and mean squared error of ≈5.0. The realization of NNGMM proves the feasibility of representing the GMM code by a neural network. The optimally-performing NNGMM obtained in this work can serve as an alternative computational tool for calculating σext in place of the original GMM code at a much cheaper cost, albeit with a slight penalty in terms of absolute accuracy.
The variation in flight attitude, line-of-sight, and speed of unmanned aerial vehicles (UAVs) affect their polarization-dependent coupling cross-section and resultant compatibility to pulsed electromagnetic energy. Here, we present the out-of-band electromagnetic compatibility (EMC) effects of UAV frame material and shape on the UAV subcomponents. Characteristic mode analysis (CMA) is employed to study the fundamental modes supported by UAVs which facilitate the interpretation of its electromagnetic response and the prediction of its effect on the nearby components. Using CMA, we develop a framework that optimizes the placement of wires and traces of printed circuit boards (PCBs) on the frame mitigating interference from undesired electromagnetic sources. A 3-D scanner is used to provide four versions of a quadrotor UAV to study the frame shape effect on the coupling. Materials of differing permittivity are assigned to these frame versions to assist in understanding the material effect on the EM coupling to the UAV.