To improve HF detection of small RFID tags, a Distributed Diameter Coil (DDC) resonator is included in the reader coil. The key ideas of detection improvement are twofold: using a resonator with Magnetic Resonant Coupling (MRC) and modifying the distribution of diameter and current for each loop of the DDC resonator. These factors allow the magnetic coupling to increase between the reader and the smaller tag, especially in our case where the effective area of the tag is below 0,1% of the reader coil surface. Numerical simulations are carried out using HFSS to confirm the enhancement of the mutual coupling between the tag and the reader coil: the coupling coefficient is used in double-loop coupling (the case of the coupling of two loops), when a third loop (resonator) is inserted. The optimization of the magnetic coupling between a large reader and a small tag with resonator could be realized in changing first the sub-coil diameters, and then the sub-coil number of turns. One figure of merit to quantify the ability of surface detection is defined. A 15% improvement of detection surface in Horizontal Mode is measured at 1 cm of the reader plane in comparison with a conventional coil. Experimental detection measurements on real structures are described to validate statements.
In this paper, a novel compact hexagonal shaped ultra-wideband multiple-input multiple-output (UWB-MIMO) Koch fractal antenna is designed with penta-band rejection characteristics for portable devices. The antenna rejects the C-band downlink frequency from 3.7-4 GHz, the C-band uplink frequency from 5.75-6.05 GHz and the satellite bands from 7.45 to 8.4 GHz. The band 7.45-7.55 GHz is used by the meteorological satellite service for the geostationary satellite services. The band 7.75-7.9 GHz is used by the meteorological satellite service for non-geostationary satellite services. The band 8.025-8.4 GHz is used by the Earth exploration satellites for geostationary satellite services. The C-band and satellite bands interfere with the UWB and have been rejected using a band reject filter. A spiral shaped slot is introduced inside the fractal hexagonal monopole to introduce band reject characteristics. The band suppression and widening of the impedance bandwidth are achieved by using defected ground structures. The antenna has wideband impedance matching with S11 < -10 dB in the UWB frequency range from 3.1 to 13.6 GHz and has a low mutual coupling with S21 < -19 dB. The antenna has very low envelope correlation coefficient of less than 0.17 and low capacity loss of 0.254, which proves that the MIMO antenna shows good diversity performance.
This paper presents the applicability of cavity modeling technique to analyze field propagation inside a multiport waveguide network. For a better understanding of the subject, we have considered a five-port quadraplexer as our target network. Field propagations within the network at different passband and stopband frequencies have been presented. The analysis has been verified by comparing the overall frequency response of the network with the available data in literature. The analysis demonstrates the field division at different junctions as well as field attenuation/propagation at different points of the network, which will be helpful for designing more complex and/or advanced multiport waveguide networks. It also demonstrates the presence of higher order modes at different discontinuities of the network and their effectson the respective field distributions.
A three-section branch-line coupler is miniaturized using diamond-series stubs microstrip lines. The modified coupler is capable of operating from 1.6 GHz to 3 GHz with a return loss of less than -20 dB, phase imbalance of less than 2.5°, insertion loss and coupling of 4.5 dB and 3.02 dB, respectively. The bandwidth of the coupler has been extended up to 1.4 GHz. In addition, it achieves up to 84% size reduction as compared to a conventional three-section coupler. Furthermore, its performance and circuit size were compared with another modified coupler with normal open-stubs microstrip lines. Effects of the diamond structure and number of stubs were analyzed and discussed in detail, Furthermore, the results achieved by this study are superior to the previous studies.
A front-end module (FEM) consisting of a single-pole-double-throw (SPDT) switch and a low noise amplifier (LNA) with good performance is proposed. The SPDT switch is based on PIN diodes, which are mounted on impedance transforming lines parallelled to the main transmission lines with an asymmetric topology. This asymmetric topology is utilized to achieve low insertion loss and high transmit-to-receive isolation. The interstage matching of switch and LNA is designed to achieve low noise figure. To validate the design, the FEM is simulated, fabricated and measured. The experiment results show that, within the range of 7.8-8.1 GHz, the FEM achieves a gain of 22 dB and noise figure of 1.9 dB in receiving mode, with an insertion loss of 0.9 dB and isolation of 40 dB in transmitting mode. In addition, the FEM can handle up to 4 W transmitting power at 8 GHz with good linearity.
Aircraft collision avoidance system is an airborne system which is designed to provide the service as a last defense equipment for avoiding mid-air collisions between aircraft. End-fired antenna is suitable to be used in such airborne systems where low aerodynamic drag is urgently required. An effort to develop such an antenna using dipole elements is presented in this paper. Here a unit element planar folded dipole antenna is presented which radiates in the end-fire direction. Split ring resonators inspired artificial materials are incorporated in the design to improve the directivity performance of the proposed antenna, and those materials are loaded in the same plane of the primary dipole radiator. Here suppression of surface wave in the antenna takes place, which results in gain enhancement and also reduction of side lobes which make radiation pattern better. All these proposed antennas are designed and simulated in CST Microwave Studio (MWS) EM tool which is based on time domain solver. The performance and other antenna characteristics have been explored from the simulation results followed by the antenna fabrication and measurement. Quite good agreement is achieved between the simulated and measured results. Much better performance characteristics make this proposed antenna a good candidate for this application.
Predicting signal power loss between the transmitter and receiver with minimal error is an important issue in telecommunication network planning and optimization process. In recent years, median order statistic filters have been exploited as a preprocessing constituent for analyzing signals. This work presents a resourceful predictive model, built on multi-layer perceptron (MLP) network with vector order statistic filter based preprocessing technique for improved prediction of measured signal power loss in a microcellular LTE network environment. The predictive model is termed Vector statistic filters multilayer perceptron (VSF-MLP). In terms of some essential performance evaluation indices such as the correlation coefficient, root-mean-square error and coefficient of efficiency, results show that VSF-MLP model prediction performs considerably better than the standard MLP model prediction approach on signal power data collected from different study locations in typical urban terrain.
In this paper, two compact planar substrate integrated waveguide (SIW) cavity-backed antennas are proposed for wireless local area network (WLAN) at 5.5 GHz and wireless body area network (WBAN) at 5.8 GHz. The miniaturization is achieved with the concept of quarter-mode-topology, and the size of the cavity is reduced up to one-fourth of the circular SIW cavity. A L-shaped slot is etched on the top plane for miniaturization, and antenna-1 is realized which resonates at 5.5 GHz. A metal strip has been added in the middle section of the slot, and antenna-2 is realized, which resonates at 5.8 GHz. Both proposed antennas are tested in free space, while the performance of antenna-2 is investigated for on-body condition. In free space, the measured impedance bandwidths of the antenna are 160 MHz and 210 MHz at 5.5 GHz and 5.8 GHz, respectively. The radiation efficiency of the antenna is 89.4% in free space and 57% on phantom at 5.8 GHz. Both measured and simulated results are observed, and they are in a good agreement.
A novel dual-layer ultra-wideband lotus-wearable antenna is presented in this paper for integration on astronaut's flight jacket to monitor the vital signs of astronauts. The proposed antenna is designed and fabricated on a leather material as a substrate to operate over a frequency band (2-12 GHz). The dielectric constant εr = 1.79 and loss tangent tanδ = 0.042 of the leather material are measured by using two different methods. The proposed antenna has three-strip lines in the 2nd layer for performance enhancement. The stretching effect of the proposed antenna on its impedance characteristics is studied. Furthermore, SAR calculations are performed on-body environments to ensure that operated properly in the nearness of the human body. Finally, the proposed design is simulated by CST simulator version 2016, fabricated using folded copper and measured by Agilent8719ES VNA. The measured results agree well with the simulated ones.
Conventional multitarget tracking techniques assume that clutter density is known a priori and use it directly in the recursive processing. However, in practical surveillance systems, the spatial distribution density of measurements generated by clutter is unknown and time-variant. Therefore, in order to achieve better tracking performance as well as the ability to evaluate the surveillance environment, we propose a fully forward-backward probability hypothesis density (PHD) smoother integrated with clutter spatial density estimator in this paper. Details on the sequential Monte Carlo (SMC) implementation method are presented as well. Simulation results of tracking performance evaluation verify the effectiveness of the proposed PHD smoother.
In this paper, a novel multiband microstrip patch antenna with small frequency ratio is designed and analysed. One can design a multiband antenna at any desired frequencies through these proposed methods. The proposed antenna shows six operating frequencies with very small frequency ratio between two consecutive resonant frequency 1.1248, 1.1123, 1.0792, 1.1469 and 1.3254 and can be used for various wireless applications i.e. 2.5 GHz for UMTS and Wi-Fi, 2.812 GHz for CCTV with wireless video links, 3.128 GHz and 3.376 GHz for WiMAX, 3.872 GHz for C-band applications and 5.132 GHz for Lower WLAN. Design procedure and formation of all six bands are presented and discussed. Analysis is done by Ansoft HFSS v.15 which is based on Finite Element Method (FEM), and simulated results are verified with experimental results of fabricated prototypes which are found in close agreement.
Diverse array processing methods with higher order statistics (HOS) have been developed in the last three decades. One of the main interests in using HOS relies on the increase of effective aperture and the number of sensors of the considered array. In this work, we further exploit space-time adaptive processing (STAP) using HOS based on the phased array radar with uniform linear array (ULA). We implement STAP with respect to signal powers instead of with respect to signal amplitudes as the convention. The purpose of this paper is to provide some important insights into the STAP with respect to signal powers (SP-STAP), such as the output response, output signal-to-interference-plus-noise ratio (SINR), minimum detectable velocity (MDV) performance and effect ofinternal clutter motion (ICM). Compared with the conventional STAP under the condition of the same number of array elements and transmitting pulses, the simulation results show that SP-STAP can gain narrower target main beam, lower side-lobe levels, better MDV performance and less deleterious effect of ICM.
In this paper, a folded slot active tag antenna for 5.8 GHz radio frequency identification (RFID) applications is presented. It consists of an inverted U-shaped monopole radiator fed by a coplanar waveguide (CPW) feed line and extended ground planes. A 10 dB return loss bandwidth of 5.65-6.55 GHz is achieved. The overall volume of the presented antenna is 10.7×11×1.6 mm3. A good agreement between the simulated and measured results is observed. The antenna has an omnidirectional radiation pattern at 5.8 GHz frequency which makes it suitable for RFID applications. It has advantages of compact dimensions and wider bandwidth than previously reported structures.
Hollow nanostructures based on the Fe100-xCox alloy were synthesized in the pores of polymer template matrices based on PET using the electrochemical deposition method. Morphology, elemental composition, and structural features were characterized by scanning electron microscopy, energy dispersive analysis, and X-ray diffractometry. The study of the internal magnetic texture was carried out using Mossbauer spectroscopy. The dependence of the change in structural and magnetic properties from the atomic content of components in nanotube structure is revealed. It is established that the synthesized nanostructures are hollow Fe100-xCox nanotubes with a body-centered cubic crystal structure. The decrease in the unit cell parameter with increasing cobalt concentration is due to the difference in the radii of Fe (1.227 Å) and Co (1.191 Å) atoms. It is established that a random distribution of magnetic moments directions of Fe atoms is observed for Fe100Co0 nanotubes. And magnetic texture along the nanotube axis is observed for Fe100-xCox nanotubes, with an increase in Co atoms concentration. The average angle between the direction of the magnetic moment of iron atoms and the nanotube axis decreases from ϑ = 54.6˚ to ϑ = 24.5˚.
This paper presents a novel compact Wilkinson Power Divider (WPD) that improves harmonics suppression. The proposed WPD consists of a shunt open stub between two series similar inductors, and a microstrip line between an isolation resistor and each output port. This configuration acts as a low-pass filter with two transmission zeros. In addition, it facilitates manufacturability by using lower transmission line impedance values than conventional structures. Through Even and odd mode analysis, the general design equations have been derived in closed form. A 2 GHz microstrip WPD is designed, fabricated and measured based on the proposed technique. A great agreement has been obtained between the measured performance of fabricated WPD circuit and the simulation results. The measured results show that the second and third harmonic levels are about -47 dBc and -35 dBc, respectively. The proposed design has about 40% reduction in size better than conventional WPD. It achieves competing results compared to other published work.
Coherent Change Detection (CCD) is a powerful technique that uses Synthetic Aperture Radar (SAR) coherence to measure subtle ground changes in the imaged area. Unfortunately, the coherence estimator is biased for low coherence values, resulting in a highly degraded change detection performance. The spatial multilooking technique is typically used to improve coherence estimation but at the expense of spatial resolution. Actually, there are few SAR satellites that are able to deliver Multiple Look Complex (MLC) SAR images, which provide noticeable coherence bias reduction. In the present work, we investigate detection performance improvement that can be obtained through the use of MLC SAR images. The detection probability and false alarm are evaluated using experimental very high-resolution SAR data. After SAR image focusing and coherence estimation, the results indicate that the use of MLC SAR images with four looks allows for nearly 60% higher detection probability in the case of a low false alarm rate.
Semiconductor saturable absorber mirror (SESAM) based on InAs quantum dot (QD) material is important in designing fast mode-locked laser devices. A self-consistent time-domain travelling-wave (TDTW) model for the simulation of self-assembled QD-SESAM is developed. The 1-D TDTW model takes into consideration the time-varying QD optical susceptibility, refractive index variation resulting from the intersubband free-carrier absorption, homogeneous and inhomogeneous broadening. The carrier concentration rate equations are considered simultaneously with the travelling wave model. The model is used to analyze the characteristics of 1.3-μm p-i-n QD InAs-GaAs SESAM. The field distribution resulting from the TDTW equations, in both the SESAM absorbing region and the distributed Bragg reflectors, is obtained and used in finding the device characteristics including the modulation depth and recovery dynamics. These characteristics are studied considering the effects of QD surface density, inhomogeneous broadening, the number of QD absorbing layers, and the applied reverse voltage. The obtained results, based on the assumed device parameters, are in good agreement, qualitatively, with the experimental results.
By using parallel strip line fed printed dipole antennas as array elements, an omnidirectional antenna array and a wide angle sector coverage array operating in octave band are designed. A maximum deviation of ±1.25 dB from the omnidirectional pattern is achieved for the omnidirectional array, and the average gain of the antenna was measured as being 5 dB in the 1.35-2.7 GHz band. For the sector coverage array, a special reflector design is utilized to maintain a half power beam width of around 115° with a standard deviation of 14° in the aforementioned frequency band. The average gain of the sector coverage array was measured as 10 dB, thereby being almost three fold larger than the average gain of the omnidirectional array.
A very compact triple band-notched multiple input multiple output antenna (MIMO) for ultra-wideband (UWB) communications is fabricated on a FR4 dielectric substrate having overall size of 18 x 21 x 0.8 mm3. The proposed antenna consists of two rectangular metal monopoles which are excited by 50-Ω microstrip lines on top of substrate, and a common protrude ground is at the bottom. To achieve low mutual coupling between radiating elements, a T-shaped stub is protruded from the ground plane. By etching two C-shaped slots on the radiating patches, band-notched functions at 5.15-6 GHz and 7.8-8.4 GHz are obtained. The third notch band from 3.3-3.7 GHz is realized by adding U-shaped metal strips to the ground. The measured and simulated results demonstrate that the proposed antenna offers good impedance bandwidth of |S11| ≤ -10 dB from 2.8-12.2 GHz covering whole UWB band except at the designed notch bands, while giving less mutual coupling (|S21|) of lower than -25 dB in the whole UWB band. The measured envelope correlation coefficient (ECC < 0.013), nearly constant gain and stable radiation patterns show that the proposed MIMO antenna is an appropriate candidate for portable UWB systems.
In this paper, we report the formulation to account for dielectrics in a first principles multipole-based cable braid electromagnetic penetration model. To validate our first principles model, we consider a one-dimensional array of wires, which can be modeled analytically with a multipole-conformal mapping expansion for the wire charges; however, the first principles model can be readily applied to realistic cable geometries. We compare the elastance (i.e. the inverse of the capacitance) results from the first principles cable braid electromagnetic penetration model to those obtained using the analytical model. The results are found in good agreement up to a radius to half spacing ratio of 0.5-0.6, depending on the permittivity of the dielectric used, within the characteristics of many commercial cables. We observe that for typical relative permittivities encountered in braided cables, the transfer elastance values are essentially the same as those of free space; the self-elastance values are also approximated by the free space solution as long as the dielectric discontinuity is taken into account for the planar mode.