The problem of electromagnetic (EM) wave scattering on small particles is reduced to solving the Fredholm integral equation of the second kind. Integral representation of solution to the scattering problem leads to necessity to determine some unknown function contained in integrand of this equation. The respective linear algebraic system (LAS) for the components of this unknown vector function is derived and solved by the successive approximation method. The region of convergence of the proposed method is substantiated. The numerical results show rapid convergence of the method in the wide region of the physical and geometrical parameters of problem. Comparison of the obtained results with Mie type and asymptotic solutions demonstrates high degree of accuracy of the proposed method. The numerical results of scattering on particles of several forms and sizes are presented.
The aim of this paper is to present a compact coplanar waveguide (CPW) fed switchable UWB antenna as an antenna filter with adjustable notched frequency bands. Novel miniaturized tunable resonators are also presented to achieve notched bands. The antenna is made tunable in notched frequency bands without any modification in the basic structure. These stopbands are made tunable just by varying values of the capacitors according to our desired applications. The antenna structure is very compact having overall dimensions of 24×30.5 mm2 with partial ground plane.The proposed small size, variable, low cost and low weight antenna with good propagation characteristics will pave the way for UWB wireless communication applications.
Ultrablack materials play an essential role in astronomical observation and many thermal applications. Many material systems such as vertically aligned carbon nanotubes have produced extraordinarily high absorption, but require complicated fabrication. Here we report a single step self-masked etching process performed on compressed-coal graphite plates on a silicon substrate, which produces an ultrablack material with 0.7% hemispherical reflectance in the visible region and specular reflectance below 0.7% between 850 nm and 10 μm. Nanoscopic pieces of silicon are ripped off the substrate and deposit on the graphite resulting in carbon nanoneedle structures, which grow linearly with etching time reaching a height of 5.7 μm after 60 minutes.
An LED array with 2N-1 lines and N rows is designed, which consists of red, blue, and far-red LEDs. The red and blue LEDs with N lines and N rows are uniformly and intervally arranged. The central distance between adjacent red and blue LEDs is d. The far-red LEDs are filled in-between every two lines of red and blue LEDs, which results in an array of far-red LEDs with N-1 lines and N rows. The central distance of adjacent far-red LEDs is also d. By using the imperfect Lambertian model, the irradiance distribution of the LED array with N being even and odd is derived in the reference plane, respectively. Also, solving equation of the optimal distance d is presented. Numerical results show that irradiance distributions of the three mixed-color, red, blue, and far-red lights of the LED array are uniform in the reference plane. Ratios of R/B and R/Fr are both relatively uniform in the reference plane. The ratio of R/B in the case of N being even is more uniform than that in the case of N being odd. However, the ratio of R/Fr is opposite.
In this paper, a compact metamaterial quad-band antenna is presented. The antenna is designed from a unit cell of asymmetric extended-composite right/left handed transmission line (E-CRLH TL) as the main resonator part and a 50 Ω coplanar waveguide (CPW) as the feeding part. The design concept and resonant frequencies are analyzed and discussed. The results show that the proposed antenna exhibits four frequency bands covering GSM810, WLAN 2.45/5.5 GHz and WiMAX 3.5 GHz bands. The overall size of the fabricated antenna is only 57.2 mm×31.2 mm×1.6 mm and is very small compared with other proposed quad-band antennas. In addition, a good agreement can be seen among the estimated resonant frequencies, HFSS simulated and measured results.
A dual-frequency InSAR imaging technique is proposed to estimate the position and motion parameters of a moving target, including velocity and cross-track acceleration. By applying a dual-frequency technique, phase ambiguity is effectively removed to obtain accurate estimation of motion parameters.
A Frequency Selective Surface (FSS) reflector with wideband response for 4G/X-band/Ku-band is proposed. The wideband FSS reflector consists of cascaded dual-layer patch FSS which is etched on separate layers of FR4 substrate. The targeted frequency range is 5-16 GHz. A wide stopband of 10.4 GHz (100% percent bandwidth) is obtained with two layers in cascade. The Equivalent Circuit (EC) method is used to approximate the simulated results. An extensive parametric study is also carried out to understand the effect of various combinations of FSS layers and their disposition. A panel of final FSS is fabricated where measured and simulated results agree well.
In this paper linear and nonlinear properties of graphene at millimeter wave frequency band are investigated. The nonlinear properties of the graphene are utilized to design frequency multiplier and mixer for millimeter wave applications. A patch of graphene is deposited on the dielectric image guide that will generate higher order harmonics. The amplitude of harmonics is optimized based on the dimensions of the graphene patch on top of the dielectric image guide. A frequency multiplier and mixer are designed, which utilize the second harmonics generated through graphene. The nonlinear behavior of the proposed designs has been simulated in the 50-75 GHz input signal frequency range. A conversion efficiency of -23 dB is obtained for the second harmonic for the frequency doubler. The frequency mixer is designed to mix two frequencies in V-band using dielectric image guide as the waveguide. A -28 dB conversion efficiency is simulated on a dielectric image-guide platform.
In this paper, sequential parametric detection problem is addressed for non-Gaussian correlated clutter. It is well known that the assumption of normally distributed clutter leads, mostly, to analytical expressions of the threshold as well the distribution of detection statistic. Nevertheless, due to the resolution improvement of recent sensing instruments such as high resolution radar, the Gaussian assumption is unrealistic since the clutter is nonhomogeneous. As a consequence, using non-Gaussian assumption of the clutter prevents, mostly, of obtaining analytical expressions of the threshold and the distribution of detection statistics. In this work, we overcome this issue by use of the so called bootstrap techniques for dependent data. Numerical simulations reveal that our proposed method outperforms the classical and sequential non-bootstrap based detection schemes in terms of probability of detection and selects the optimum sample size needed to achieve the required detection performances.
A Compact Non-Bianisotropic Complementary Split Ring Resonator (NB-CSRR) based microstrip triple band antenna is presented in this paper. The antenna has a simple structure compared to other antennas for triple band operation. The antenna consists of a microstrip-fed NBCSRR loaded radiating element and partial ground plane. The designed antenna has a compact size of 29.4 mm x 26 mm x 1.6 mm. Two NBCSRR slots are etched on the radiating patch. Bottom NB-CSRR is used to generate new resonance, and top NB-CSRR is used to improve the return loss. The measured data show that the antenna covers the frequency ranges of 2.5 GHz-3.61 GHz, 4.06 GHz-4.69 GHz, 4.80 GHz-6.07 GHz with impedance bandwidth of (<-10 dB) of 1.11 GHz, 0.63 GHz and 1.27 GHz. The results show that the antenna can cover WLAN and C band applications.
The paper presents an advanced quasi-FEA technique on the iron losses prediction using Bertotti's iron loss separation models, in which a curve fitting is taken into account for coefficients calculation of each model. Moreover, the skin effect and saturation consideration are applied in order to check the accuracy through the relative error distribution in the frequency domain of each model from low up to high frequencies 50 to 700 (Hz). Additionally, this comparative study presents a torque-speed-flux density computation that is discussed and presented. The iron loss characteristics of a radial flux permanent magnet synchronous machine (PMSM) with closed-slots and outer rotor topology are also discussed. The quasi-finite-element (FE) analysis was performed using a 2-D and 3-D FEA, where the employed quasi-2-D FEA is proposed and compared with 3-D FEA, and along with experimental verifications. Finally, all the iron-loss models under realistic and non-ideal magnetization conditions are verified experimentally on a surface-mounted PMSG for wind generation application.
This paper presents a circularly polarized tag on a 3×3 AMC structure to obtain longer read range for UHF RFID on-body applications. A modified T-matching transformer is employed to achieve conjugate matching with the Monza 4 microchip. To overcome the influence of lossy human body, a cross-dipole tag antenna is directly implemented on the phase-dependent AMC structure to achieve high gain and isolate the influence of the human body. Then, the tag is pasted on a lossy human model to investigate its performance. The study finds that the AMC can increase the antenna gain by 3.34 dB and help generate circularly polarized (CP) wave. The measured fractional bandwidth of impedance is 3.2% which can cover the UHF RFID bands of North America and Taiwan. The measured read range of the tag pasted on a human body reaches 15.7 meters when the reader has 4 W EIRP, and the sensitivity of the microchip is -16.7 dBm.
In this paper, a low-profile wide bandwidth circularly polarized microstrip antenna is proposed as element for a C-band airborne circularly polarized synthetic aperture radar sensor. Several bandwidth improvement techniques were proposed and implemented. In order to increase impedance bandwidth, the antenna is constructed using double-stacked substrate with low dielectric constant, modified radiating shape for multi-resonant frequency, and a circle-slotted parasitic patch. Generation of the circularly polarized wave employs a simple square patch with curve corner-truncation as radiating element. The asymmetric position of the feeding is attempted to improve the axial-ratio bandwidth. To avoid a complicated feed network, the antenna is fed by single-feed proximity-coupled microstrip line. The effect of copper-covering on the upper layer for decrease undesired radiation wave emitted by the feeding is also studied and presented. Measurement results show that the impedance bandwidth and axial ratio bandwidth are 20.9% (1,100 MHz) and 4.7% (250 MHz), respectively. Meanwhile the measured gain is 7 dBic at the frequency of 5.3 GHz.
A high return loss (-30 dB), small size (100 mm2) and broad bandwidth (1.5 GHz) microwave bandpass filter has been designed using finite element modelling and developed using the superconducting YBa2Cu3O7-δ (YBCO) thin films deposited on a (10 × 10 mm2) LaAlO3 substrate by spin coating. The thin films have been prepared by electrospinning and solid-state techniques. The microwave properties of filter circuits were experimentally determined using the vector network analyser (VNA) at room temperature (300 K) and in the presence of liquid nitrogen (77 K). The solid-state filter showed high return loss (i.e. -22 dB) at operating frequency of 9.7 GHz and broad bandwidth of 1.5 GHz, which is consistent with the simulation results. The insertion losses for YBCO filters are ~-2, ~-1.5 and ~-3 dB for the normal, nanoparticle and nanorod respectively. However, the electrospun filters exhibited lower performance due to the nano-structural properties of YBCO samples at nanoscale which make these sample have a large band gap compared to solid-state sample. The results indicate that the filter design and simulation result are reliable. Hence, HTS YBCO could be a potential microwave bandpass filter in industry.
This paper proposes a novel planar direction-of-arrival (DOA) estimation antenna. The estimation capability of phase monopulse DOA estimation antennas is enhanced by integrating an RF multiplier that detects the phase relation between the sum and difference of the two received signals. So the proposed antenna provides a wide range of estimation whereas the conventional monopulse DOA estimation antennas determine the angles of half space. A prototype antenna has been fabricated, and the proposed concept was successfully confirmed.
In this paper, the analysis and design of a compact Multiple Split Ring Resonator (MSRR) inspired microstrip rectangular patch antenna is presented. The MSRR is used with four rings. The size of the antenna is 25 × 31 × 1.6 mm3 realized on a low cost FR4 substrate. The proposed rectangular microstrip patch antenna operates at the resonant frequency of 5.88 GHz prior to MSRR inclusion. The antenna characteristics are studied before and after inclusion of metamaterial. After including MSRRs at appropriate places, the proposed MSRR antenna induces a new resonant frequency of 2.78 GHz. In addition to rectangular patch's fundamental resonance, the additional resonance is obtained at 2.78 GHz, thus, exhibits dual bands. Hence, MSRR loading antenna attains a bandwidth of 197 MHz at 2.78 GHz and 703 MHz at 5.88 GHz. The prototype of the proposed antenna is fabricated and measured. Simulated results are verified with the measured ones. This proposed antenna can be effectively utilized for WLAN and RF-ID applications. Parametric studies are illustrated to yield the desired frequency bands. Equivalent circuit model analysis of the MSRR loading is determined. Band characteristics of split ring structure are used to determine the negative permeability characteristics.
The frequency response characteristics of a basic microstrip lowpass filter improved using H-shaped defected ground structures are presented. The proposed defected ground structures behave as a resonant element at high frequency and thus eliminate the stopband frequencies to achieve wide stopband rejection. The 3 dB cutoff frequency of the filter is 1.935 GHz. Due to the defects etched in the ground plane of the basic structure, the harmonic rejection is improved from 5th to 10th order along with low insertion loss and voltage standing wave ratio together with good selectivity. The compact filter has a size of 0.0338λg2, with λg = 85.18 mm being the guided wavelength at cutoff frequency. The characteristics of the lowpass filter are verified through simulation and measurement. Consistent and stable results are obtained.
In this paper a miniaturized dual wideband bandpass filter is designed by the modified extended composite right/left-handed transmission line (ECRLH-TL) under balanced conditions in each right/left-hand passbands. A novel equivalent circuit is proposed to provide the design and an implementation of ECRLH unit-cell by means of the complementary, split ring resonator (CSRR) on the ground plane. Since CSRR is utilized as an alternative to implementing one of the resonators of ECRLH unit-cell, the size and complexity of the structure can be consequently reduced. An example of a dual band pass filter with 3 dB frequency bands from 3.2 to 4.8 GHz and from 6 to 7 GHz is investigated. There is a good agreement among circuit, electromagnetic simulations and measured results in both passbands. The measured insertion loss is better than 0.5 and 1 dB in first and second bands central frequency, respectively. The group delay which is an important factor in wideband communications is about 0.62 ns and 0.71 ns, respectively, in the first and second band central frequencies. The final dimensions of the miniaturized filter are reduced to 8.88 mm X 8.18 mm.
In this paper, a CPW-fed compact metamaterial-inspired monopole antenna is proposed for Industrial, Scientific and Medical radio band (ISM, 2.4-2.483 GHz). The proposed antenna consists of a T-shaped patch and a set of split ring resonators (SRRs). The miniaturization is attained after loading SRRs in proximity to the T-shaped radiator, which makes the antenna structure electrically small. The measured fractional bandwidth of the antenna is 4% (2.42-2.52 GHz), and its size is 0.22λo× 0.098λo×0.013λo. In addition, the electrically equivalent circuit of the proposed antenna is modeled, and the resonant frequency is calculated by using an analytical approach. Also, the permeability plot of SRRs is extracted using Nicolson Ross weir method. The measured peak gain and radiation efficiency of the antenna are obtained as 1.76 dBi and 78.5%. The simulated results and measured results are found in a good agreement.
A simple broadband circularly polarized (CP) aperture antenna is proposed in this letter. The antenna is composed of an L-shaped feed line and a circular aperture. With the newly introduced perturbation slots, a new resonant mode TE31 is generated, which can widen the CP bandwidth without increasing the antenna size. Measured results of the fabricated antenna shows 93.5% (2.9-8 GHz) impedance bandwidth (|S11|<-10 dB) and 66.6% (3-6 GHz) 3 dB axial-ratio bandwidth. The overlapped CP working band covers the entire WiMAX, WLAN and lower frequency 5G bands. Its peak gain is 4.9 dBic at 3.5 GHz, and its gain variation is less than 1 dBic within 3-5.8 GHz band. Design considerations, empirical formulas and surface current analysis are also presented and discussed.