This paper represents the analysis and study of selecting the highest power node in the wireless sensor networks as a cluster head. The study assumes that the sensors are fixed and uniformly distributed, and the position of the sink and the dimensions of the sensor are known. The paper introduced a proposed protocol to prolong the time interval before the death of the first node (stability period), which is critical for many applications. The aim of this paper is also to improve the performance of the network by increasing the overall throughput of the network. The proposed protocol selects the cluster head depending on the power level of the node which is the most important factor of the behavior of the nodes. The simulation is made by MATLAB, and the results are compared with two other protocols, LEACH and SEP. It is found that the selection of the highest power node as a cluster head increases the stability region and throughput of the network compared to other protocols.
We propose a novel absorber by integrating four different-sized pyramidal metamaterials into a unit cell, which leads to a super broadband absorption by properly selecting the geometrical parameters for each pyramid. It is found that in such a design strategy, the high-order modes may be excited and further enhanced by multi-layer overlapping between adjacent unit cells. The as-designed MA, which consists of 13 pairs of alternating metal-dielectric layers with a total thickness of 4.13 mm, shows an absorption of above 90% in the whole frequency range of 7-21.5 GHz. The full width at half maximum is 101.8%, and the ratio of operational bandwidth to thickness achieves 7. The proposed MA is 30% broader and 5.2% thinner than previously reported absorbers working in the same spectral region. Numerical result shows that the proposed absorber is independent of the polarization. The absorption decreases with fluctuations as the incident angle increases but remains quasi-constant up to relatively large angles. Such a design shows great promise for a broad range of applications at microwave frequencies, and the proposed scheme may be extended to the visible, infrared, terahertz spectral regions.
A multiple-input-multiple-output (MIMO) antenna array with eight printed coplanar waveguide (CPW)-fed monopole antennas operating at 3.5 GHz (3.4-3.6 GHz) is presented. Each antenna is an Inverted-L (IL) monopole surrounded by a parasitic IL-shorted stripe and attains compact configuration. Both the IL-monopole and parasitic IL-shorted stripe contribute their fundamental resonant modes to operate in the desired frequency band. The neutralization line (NL) and ground middle slot are used for decoupling the antenna elements in the array. The measurement results for the prototype reasonably agree with electromagnetic simulations. Measured results for the proposed MIMO antenna array demonstrate that it has impedance bandwidth more than 200 MHz with (S11 < 6 dB), and with effective antenna decoupling mechanism the mutual coupling is better than 10 dB for the required band (3.4-3.6 GHz). In addition, envelope correlation coefficient (ECC) for the proposed MIMO antenna array is less than 0.2 for any two antennas to realize independent prorogation path for a channel. The average channel capacity of the proposed MIMO antenna array is approximately 35 to 38 bps/Hz for a reference signal to noise ratio (SNR) of 20 dB.
In this paper, a new kind of capsule endoscopy with through-body radar is utilized for the first time. Finite difference time domain (FDTD) method is used to establish an electromagnetic simulation model of stomach. A technique based on the combination of improved back-projection (BP) algorithm and support vector machine (SVM) is proposed to solve the problems of rapidly recognizing tumor shapes in the stomach. In this technique, imaging data can be obtained using the improved BP algorithm and are classified by the SVM. The algorithm must consider the influence of various tissues in the human body: the attenuation of the signal strength of electromagnetic waves, the decrease in speed and the refraction due to the different permittivity between the different organs of the body. These factors will eventually lead to image offset, and even generate a virtual image. It is effective to refrain the displacement of image with modifying the time element of the imaging algorithm by iteration. Simulation results based on data from the model verify its feasibility and validity. Results further demonstrate that the resolution is extremely high. Tumor shapes, which have different sizes, positions, and quantities, can be reconstructed using this approach. When the data are contaminated by noises, the tumor shape in the stomach can still be suitably predicted, which demonstrates the robustness of the method. Finally, classification accuracy analysis for different sampling distances and sampling intervals shows that the effects of changing the distance and intervals on shape recognition are limited. The classification accuracy can also be improved by decreasing the sampling intervals or increasing the sampling distance.
In this paper, a metamaterial loaded square-shaped fractal antenna with two iterations is presented and discussed. A metamaterial loading consistsof split ring resonators (SRRs) which enhances the bandwidth of the antenna keeping the dimensions and size of the antenna same. The square-shaped fractal antenna, which is in the form of three concentric rings, was simulated and fabricated, and the results were shown and discussed. The antenna resonates at three distinct frequency bands 4.3719 GHz, 7.7437 GHz and 10.6374 GHz with the gains of 1.1974 dB, 4.2745 dB and 4.7233 dB, respectively for resonant frequencies. The bandwidths for the antenna are 185 MHz, 198 MHz and 386 MHz for distinct resonant frequencies. The antenna is fabricated using an FR-4 substrate, and the measured resonant frequencies are 4.08 GHz, 7.545 GHz and 10.24 GHz. In metamaterial loading condition, the dimension of the antenna resonates at 4.0105 GHz, 6.8474 GHz and 8.0632 GHz with bandwidths of 636 MHz, 347 MHz and 1.33 GHz at resonant frequencies. The appreciable bandwidth is achieved in such a small antenna without changing dimensions and size of the antenna. The simulated, experimental results and comparison are also presented in this paper.The results show that the proposed method can be used to design high bandwidth and compact fractal microstrip patch antennas without increasing dimensions.
This paper describes a compact triple-band monopole antenna based on metamaterial inspired Open Complementary Split Ring Resonators (OCSRRs) for Wireless Local Area Network (WLAN) and Worldwide interoperability Microwave Access (WiMAX) applications. The monopole antenna with engraved ground plane is used to cover WLAN frequencies (2.67 GHz and 5.47 GHz). The resonant frequency of WiMAX (3.43 GHz) is achieved by introducing metamaterial inspired OCSRR in the monopole antenna. To realize good impedance matching, one more OCSRR is introduced in the monopole antenna. This paper includes the pass band characteristics of OCSRRs as well as negative permittivity details. The prototype antenna is fabricated on an FR-4 substrate having dimension of 29.4 × 26 × 1.6 mm3. Simulated and measured results are shown in good equivalence. The dipole radiation pattern is obtained in the elevation plane (E-Plane), and omnidirectional radiation pattern is obtained in the azimuthal plane (H-Plane). Parametric analysis of OCSRRs is studied to attain the best results. The proposed antenna has adequate advantages, including compact size, multiband, and impedance matching.
This paper presents the comprehensive analytical design and numerical performance evaluation of novel millimetrewave (mm-wave) switched-beam networks, based on the Rotman lens (RL) array feeding concept. These passive array devices have been designed for operation in the 28-GHz frequency band, covering the whole 18-38 GHz frequency range. The primary objective of the work is to conduct a thorough feasibility study of designing wideband mm-wave beamformers based on liquid-crystal polymer (LCP) substrates, to be potentially employed as low-cost and high-performance subsystems for the advanced transceiver units and large-scale antennas. The presented RLs exhibit significant output behaviours for electronic beam steering, in terms of the scattering (S) parameters, phase characteristics, and surface current distributions, as the feeding systems' primary functionality indicators.
A mode-matching solution to plane wave scattering by a plasmonic nanohole array consisting of a silver film perforated by an infinite square array of circular holes is presented. A complete orthonormal basis set consisting of waveguide modes satisfying an impedance boundary condition on the hole wall is derived. Impedance boundary conditions are satisfied on the upper and lower horizontal surfaces of the film and on the walls of the hole. Extraordinary optical transmission (EOT) is studied over optical wavelengths. Theory predicts a peak transmission value that is in better agreement with experiment than previous modal studies. The effect of film thickness on coupling between modes bound to the upper and lower surfaces is studied. The transmission profile for thinner films evinces two peaks at different wavelengths resulting from strong coupling between surface waves bound to the upper and lower surfaces. For thicker films, the surface waves decouple and a single peak is observed. The effect of hole radius on EOT is considered. It is demonstrated that transmission peaks occur for holes of a roughly constant electrical size. A relationship between the lattice constant and the transmission-to-area efficiency is quantified.
In binned arrays, radiators are classically located according to a uniform probability distribution. By doing so, it has been shown that they have the same mean radiation pattern as totally random arrays (i.e., the ones for which the radiators' positions are continuous independent and identically distributed random variables defined over the whole array aperture) but a lower variance. In this paper, we introduce a new class of generalised binned arrays by generalising the rule for assigning the radiators' positions. These new binned arrays, while maintaining the aforesaid advantage (in terms of the variance behaviour), allow to set the mean radiation pattern according to some design requirements. The achievable performance is estimated by measuring how much the radiation pattern deviates from the desired mean radiation pattern by resorting to the up-crossing theory. In particular, the study is developed for the case of symmetric arrays, which allows for easier maths. The paper includes an extensive numerical analysis which allows to check the developed theory. In particular, it focuses on the comparison between the generalised binned array and the totally random ones. A comparison with the nonuniform arrays coming from the density tapering approach is also presented. The latter appears natural in view of the new bins selection rule, which, as will be shown, is a sort of density-tapering in which the role of the reference current is played by the radiators' position density distribution.
The primary objective of this paper is to design a high-gain, circularly polarized patch antenna suitable for Radio Frequency Identication (RFID) readers that operate in the FCC and ETSI bands (865-928 MHz). These designs will be used in a healthcare application to provide tag identification for thousands of medicines stored on shelves inside a pharmaceutical warehouse. Consequently, it is important that these antennas provide sucient electromagnetic coverage and polarization diversity in order to boost tag readability and minimize item identification errors. The proposed RFID reader antenna design begins with a single patch with truncated corners on air substrate in order to help us understand the effect of various geometrical parameters on critical antenna figures of merit. A stub is introduced in order to improve the impedance matching characteristics of the antenna. The wideband characteristic of the design, for both impedance matching and axial ratio, is achieved by a second truncated-corner patch antenna positioned on top of the first one. An optimum design is achieved by changing the heights of the main and parasitic patches, the size of the truncated corners, and the probe position. The final antenna designs are verified by comparing measurement and simulation results.
In this paper, a horizontally polarized (HP) omnidirectional antenna array with a broadband characteristic is presented. The proposed antenna consists of a circular array based on four planar arc dual-dipole structures, a wideband 1-to-4 feeding network with baluns, four reflectors and twelve directors. The arc dual-dipoles with four etched slots are introduced to obtain the broadband characteristic. By using twelve directors in front of the dipoles, the gain variation in the horizontal plane is improved. In addition, the reflector elements are able to improve the gain for the middle frequency band. With the concept, a prototype antenna with an overall size of 0.66λL × 0.66λL × 0.01λL (λL× is the free-space wavelength at the lowest frequency) is fabricated and measured. The designed antenna exhibits a relative impedance bandwidth of 98.3% (1.245-3.652 GHz) for |S11|<-10 dB. The HP omnidirectional patterns provide a gain variation less than 3.0 dB over the frequency band 1.245-3.519 GHz (95.5%). Within the impedance bandwidth, the cross-polarization level is lower than -20 dB in the horizontal plane.
In this paper a compact wideband aperture coupled microstrip patch antenna (MPA) with impedance bandwidth of 26.3% is designed. Size reduction of the radiating element and the slot in the ground plane is achieved by incorporating an interdigital capacitor (IDC) in the patch and a complementary split ring resonator (CSRR) close to the slot which offers composite right/left-hand (CRLH) antenna. An interdigital capacitor in the patch acts as series left-hand component, and the slot together with the CSRR in the ground plane acts as a left-hand parallel inductor. By this technique, the patch and slot dimensions compared with the initial designed antenna are reduced about 26.2% and 30.2%, respectively. Through cutting CSRRs with different arrangements in the ground plane, a dual frequency band antenna is designed. Finally, a compact wideband circularly-polarized (CP) MPA is proposed through imposing various perturbations in the current route in the ground plane of the antenna. The maximum gain and the impedance bandwidth of the designed CP antenna are 8.4 dBi and 25%, respectively. Two designed antennas are fabricated and tested. The measurement results confirm the simulation ones.
In this paper, a lowpass filter with -3 dB cut-off frequency of 1.69 GHz employing modified hairpin resonator with long straight slots is designed. In the first step, to design the primary resonator, the open stubs of a conventional hairpin resonator are folded inside its free area, which results in a smaller occupied area and an improved frequency response. Next, to control the scattering parameters, asymmetric coupled lines with slots are utilized instead of symmetric open-stubs of the primary resonance cell. In each step, the impact of the employed microstrip transmission lines on the scattering parameters of the designed resonator is determined by extracting the equations of the insertion loss (S21) and return loss (S11) on the basis of their equivalent LC circuit. Finally, by using two modified resonators with slots which are placed symmetrically around (Y) axis, a sharp transition band (264 dB/GHz) and wide stopband from 1.78GHz to 10GHz with a suppressing level of -20 dB are obtained. The overall circuit size is 0.140λg×0.076 λg, which indicates a small circuit size. The proposed lowpass filter has a high figure of merit equal to 72032.
Traffic alert and Collision Avoidance System (TCAS) is an airborne system which is designed to provide the service as a last defense equipment for avoiding mid-air collisions between the aircraft. In such airborne systems, where low aerodynamic drag is urgently required, the end-fire antenna is suitable to be used. An effort to develop such an antenna, using microstrip elements, is described in this paper. Here, a Multi-Feed Microstrip Antenna is presented which radiates in the end-fire direction. The proposed antenna is designed in such a way that it can radiate the whole 360° surveillance region of the aircraft. To encapsulate the antenna inside an enclosure, an aerodynamically shaped Radome is also designed and presented in this paper. For designing this antenna model and its Radome, CST Microwave Studio is used here as the EM tool. 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.
This paper presents a design and evaluation for a miniaturized ultra-wideband (UWB) printed monopole antenna. The design integrates a UWB printed bell-shaped monopole antenna with a short stub. This antenna improves the matched impedance in the lower frequency band by using the short stub structure. The proposed antenna is formed on a low-cost FR-4 dielectric substrate with the size: 28 x 20 x 1.6 mm3. The designed antenna operates with impedance bandwidth of 3.1~4.0 GHz. The omnidirectional radiation patterns are obtained over the frequency range. Calculation and measurement show that this antenna acquires broadband characteristics covering the required frequency band of UWB system. The proposed antenna is assumed for applying to UWB radar, etc.
A wideband omnidirectional circularly polarized (CP) patch antenna is proposed in this paper. The proposed antenna is composed of a disk-loaded coaxial probe and four pairs of modified Γ-shaped strips loaded with shorting pins. Each pair of modified Γ-shaped strips consists of an inner Γ-shaped strip and an outer Γ-shaped strip. The approach employed in this design to improve the impedance bandwidth is to add an inner Γ-shaped strip and make it couple to the outer one. By introducing the two coupled Γ-shaped strips, two different monopole modes can be achieved simultaneously and controlled separately by two different corresponding parts of these two Γ-shaped strips, respectively, and they can be merged to realize a wide-band impedance matching. Meanwhile, the dual minimum axial ratio (AR) points around the resonance frequency of the antenna are excited by the coupled Γ-shaped strips, and they can be reallocated closely to each other for wide AR bandwidth. In the design, the monopole mode of the patch antenna is excited by the disk-loaded coaxial probe for generating the θ-polarization and the Γ-shaped strips are utilized for achieving the φ-polarization. Omnidirectional CP radiation pattern is obtained once the two orthogonal components are equal in amplitude but in phase quadrature. is conducted to further verify the proposed design.
Wideband arrays have recently received considerable attention in 5G applications to cover larger frequency bands. This paper presents a novel design of a high gain and wideband antenna subarray from 23 GHz to 32 GHz, which covers the frequency bands proposed by the Federal Communications Commission (FCC) for 5G communications. The proposed subarray consists of four radiating elements with wideband and high gain characteristics. These elements are composed of two stacked patches, which are fed using the proximity coupling technique. A unit-cell element prototype is first fabricated and tested to validate the gain and bandwidth performances. A 1x4 subarray prototype is then fabricated and tested, while maintaining an element spacing less than half-wavelength at the center frequency, to avoid grating lobes and to keep the small size of the antenna subarray. The measurement results of the prototypes, i.e. unit cell element and subarray prototypes, show good agreements with the simulations. The subarray measurements demonstrate a high gain of 10-12 dBi, an impedance bandwidth of 33.4 %, and a 1-dB gain bandwidth of 10.5 %. The proposed antenna subarray is a good candidate for wideband and high gain antenna arrays suitable for 5G mmW applications.
A microstrip antenna system operating in the 2.4 GHz WLAN band is presented for in-band full-duplex operation. The design includes a patch antenna fed by a 180° hybrid. Two feeding methods are presented, probe and aperture. The measured bandwidths are 2.5% (60 MHz) and 2.1% (50 MHz) for the probe fed and aperture fed, respectively. The probe fed system reaches measured isolation (S21) < -50 dB and the aperture fed < -45 dB in a reflective environment. The design also has an omnidirectional radiation pattern, reasonable gain values, and a very low envelope correlation coefficient (<0.01).
A simple but efficient method is investigated for predicting electromagnetic interference between antennas on vehicles. By modeling the vehicle body with a conducting wedge, the geometrical optics and uniform theory of diffraction are used to predict the interference power. Comparisons show that the interference power can be accurately predicted with only four dominating rays taken into account. The presented method is validated by measurements in typical environments. A further investigation of various parameters considered in predictions is also presented. Based on the proposed method, the interference power can be easily predicted just in MATLAB instead of the time-consuming full-wave simulation of the entire large-scale structure.
This paper proposes a two-element LTE MIMO handset antenna with physically different main and diversity antennas. The performance of the design is studied theoretically and experimentally. The investigated design utilizes physically different main and diversity antennas to improve especially the low-band MIMO performance. A Combined Parasitic-coupled, Aperture-Matched (CPAM) antenna is used as the main antenna, and the diversity antenna is a simple Capacitive Coupling Element (CCE) design. The antenna covers the LTE bands from 698-960MHz and 1710-2690MHz with fixed matching circuits suitable for low-band (LB) Carrier Aggregation (CA). Measured total efficiency of the antennas is from -3 to -6 dB and -2 to -5 dB at the low and high bands, respectively. In the MIMO case, envelope correlation (ECC) and multiplexing efficiency are studied also from measurements.