An effective development of a dual composite right/left-handed (D-CRLH) leaky-wave (LW) structure for dual-polarized antenna application is presented. The dual-polarized antenna consists of a two-section 3 -dB rat-race hybrid and two symmetrical substrate integrated waveguide lines. Each of the waveguide lines is periodically loaded with 15 transverse slots and 15 longitudinal slots. The dual-polarization capability and D-CRLH LW property of the antenna are analyzed and discussed. The S-parameters and gain patterns are presented for the antenna. Measured results are consistent with the simulated ones. The proposed LW antenna shows some desirable merits, such as the simplicity in design, low-cost fabrication, multi-band operation, flexible radiation directions and dual-polarization capability.
Our work investigates the well-known Lorentz formula (in its original form) for the EM force. It allows the prediction of one effect of the action of the EM force on a moving charge. We use this effect to explain Tesla's mechanism of wireless power transfer between resonant coils.
A new shape of ultra-wideband antenna with a measured bandwidth of 122.67% is presented in this paper. The proposed antenna has fabricated on Duriod 22 × 41 mm2 substrate and tested. The simulated and measured return loss results which have been presented in this paper indicate the antenna operates between 2.9 to 12.1 GHz frequency bands. In order to increase the bandwidth of aforementioned antenna, a unique shape of the ground plane has been proposed. This shape of ground plane has a very important role not only on increasing the bandwidth but also for removing some unwanted ripples from the return loss results.
A novel triple-band microstrip-fed planar monopole antenna with defected ground structure (DGS) is proposed for WLAN and WiMAX applications. The proposed microstrip-fed antenna consists of a rectangular patch, dual inverted L-shaped strips and a defected ground. The designed antenna can generate three separate resonances to cover both the 2.4/5.2 GHz WLAN bands and the 3.5 GHz WiMAX bands while maintaining a small overall size of 20 mm × 27 mm. A prototype is experimentally tested, and experimental results show that the antenna gives good radiation patterns and enough antenna gains over the operating bands.
We present a simple approach to measure the dielectric constant of solid materials. In this approach, the powder for the solid under investigation is mixed with the oil at a specific volume fraction. By measuring the oil and the mixture, the permittivity of the inclusion, i.e. the solid, can be accurately derived from the Maxwell-Garnett effective medium theory. With this method, the strict requirements for the solid shape and surface flatness in the conventional measuring configurations can be waved off, and meanwhile the broadband permittivity can be obtained. This method also enables the permittivity measurement on a level of single particle, in an average sense, for materials in natural powder form. The demonstrations on alumina, glucose, and pearl show this approach is valid and robust.
In this paper, we introduce a highly electric-field-coupled (ELC) metamaterial planar absorber in microwave frequency range. The structure is a one layer dual linear polarization insensitive absorber, which is designed by utilizing properly arranged resonant structure with orthogonal polarization sensitivity. In addition, this metamaterial absorber operates over a wide angular range, from 0° to 65° with more than 95% absorption peak. Absorption peak occurs at the frequency of 10.05 GHz with 98% magnitude with FWHM about 5%. In addition to simulation, the theoretically results are verified by measurement, and test results generally agree with simulation ones. The dielectric spacer loss tangent for higher absorption peak and broader bandwidth has been investigated too, and the optimum value for the best absorber structure performance has been obtained.
A bandstop filter with reconfigurable two-state center frequency and bandwidth is presented. The prototype of the proposed reconfigurable bandstop filter consists of one section of anti-coupled line short-circuited by an open low-impedance line. By introducing PIN diodes, this bandstop filter exhibits a lower stopband response centered at a lower frequency in the ON state, and a wider stopband response centered at a higher frequency in the OFF state. Filter using the proposed structure is designed, simulated and measured. The results confirm the designing method by showing a narrow stopband with the center frequency of 1 GHz and a wide stopband of 2.9 GHz bandwidth centered at 2.5 GHz respectively.
The use of carbon-fiber tissue as a replacement for metal radiating element has been investigated to fabricate microwave antennas embedded in composite material panels. A single ply of a dry carbon-fiber tissue with a 0.15 Ω/sq sheet resistance value and a square shape (50 mm × 50 mm) acts as the radiating element. It has been embedded inside the glass-fiber and polyester resin composite laminate by using the infusion technique. The measured radiofrequency characteristics of the pure composite antenna are presented, discussed and compared to those of a reference counterpart, made from a plain metal sheet. The pure composite antenna exhibits a measured gain strictly alike to that of the reference antenna up to 2.1 GHz.
A compact wide-band bandpass filter (BPF) with high frequency selectivity using stepped impedance resonators (SIRs) is presented in this paper. The proposed BPF consists of four SIRs, which share a common grounded via-hole. To improve the frequency selectivity, multiple transmission zeros (TZs) are employed in the stopband by mixed electric/magnetic (EM) coupling. The novel filter with 32.2% fractional bandwidth (FBW) has been designed and fabricated to verify the validity of the proposed method. Measured results are in good agreement with the electromagnetic simulation. The measured results show three finite transmission zeros in the stopband, located at 2.47 GHz, 5.26 GHz, 9.39 GHz, respectively. The circuit size of proposed BPF only occupies 3.10 x 13.30 mm2.
In this paper, a microstrip combline bandpass filter (BPF) with a broad upper stopband performance is presented. The proposed filter is based on the design of a bandpass filter cascaded with a defected microstrip structure (DMS) bandstop filter. The bandstop characteristic is realized using T-shaped DMS at the external input and output coupling transformers. The measured and simulated electrical performances are in good agreement and demonstrate broad upper stopband bandwidth. The proposed filter is also compared with the characteristic of a conventionally designed filter to highlight the advantages of the proposed approach.
Step-by-step procedures for designing a third order bandpass filter and a sixth order bandpass filter using a triple-mode resonator are described in this paper. The triple-mode resonator is a square open-loop resonator with an open circuited stepped-impedance stub and a grounding via located at the symmetrical plane of the resonator. The equations for approximating the resonant frequencies of the resonator are obtained from odd- and even-mode analysis. To design a filter, first, the theoretical resonant frequencies for the filter are calculated. Then the basic dimensions of the resonator are approximated using the equations. The filter layouts are fine-tuned by simulation and verified by experiment to conclude the paper. The first spurious response occurs at about 3 times the center frequency of the first passband in both filters. The simulated and measured results are in good agreement.
A novel 3-pole bandpass filter (BPF) based on microstrip loaded ring resonators (LRRs) is proposed. Each resonator is composed by a closed-loop transmission line and a short-circuited stub. By properly adjusting the impedance and the electrical length of each resonator, the proposed circuit may be made compact (over 93.7% smaller than a conventional ring resonator) and its stopband may be extended simultaneously. Each resonator exhibits an area of 0.0727 λg x 0.079 λg where λg is the guided wave length. A BPF at the center frequency of f0=1.9 GHz with stopband extended up to 7.8 GHz (=4f0) is developed showing good agreement between simulation and experimental results.
In this paper, a semicircle ended stub resonator, cascaded to a modified radial patch to design a compact lowpass filter with sharp roll-off and wide stopband is proposed. This filter has 3 dB cutoff frequency at 1.54 GHz. The transition band is only 0.26 GHz from 1.54 GHz to 1.8 GHz with corresponding attenuation levels of -3 dB and -20 dB respectively. Maximum insertion loss is 0.1 dB in the passband, and the stopband bandwidth with the attenuation level better than -20 dB is extended from 1.8 GHz up to 13.93 GHz. So, a wide stopband is achieved. The proposed filter is designed, fabricated and measured, where there is a good agreement between the simulation and measurement results. The results show that a roll-off rate of 65.4 dB/GHz together with a relative stopband bandwidth of 154% with the suppression level of -20 dB is obtained while achieving a high figure of merit (FOM) of 23509.
A new high isolation lumped-element 180º hybrid, using electronically adjustable filters with varactor diodes, are proposed. This design is very simple and is based on only two configurable low order (N = 2) filters. Due to the limited tuning frequency range of varactor diodes, maximum near-octave frequency coverage of 2.5-5 GHz was planned in the high isolation hybrid. An impressive simulated typical isolation in the range of >60dB was achieved. One of the typical applications of developed hybrids could be the conversion of 70MHz IF to microwave frequencies, with broadband mixers in single-conversion converters, and with very high LO rejection (>60 dB).
We present an application of the Akaike Information Criterion (AIC) for an automatic and accurate determination of the acoustic and electromagnetic emission (AE and EME) onset times. The onset time information is used to derive the time delays between correlated AE and EME events from rock specimens during laboratory fracture experiments. The observed correlation in time between AE and EME events is consistent with EME release during microcrack growth. Relevant load drops are accompanied by AE bursts, expected to be generated during macrocracks propagation.
A defective Photonic Band Gap device based on dilute nitrides is proposed as a high performance active wavelength filter for wavelength division multiplexing applications. The analyzed structure is made of GaInNAs-GaInAs multi quantum well ridge waveguides in which a geometrical defect in the periodic lattice induces selective transmission spectral regions centered at different wavelengths inside the photonic band gap. The multichannel filter performances are evaluated as a function of both the defect length and the injected current value. The analysis is performed by using proprietary codes, based on the Bidirectional Beam Propagation Method with the Method of Lines introducing the rate equations. Highly selective 11-channel active filter with minimum value of the bandwidth at half-height Δλ = 0.105 nm with gain G = 16.51 dB has been assessed.
A circularly polarized (CP) elliptical-ring slot antenna is proposed. A tapered slot is excited by an L-shaped coupling strip. A good impedance match is obtained, and an excellent CP characteristic is achieved. The antenna has been investigated numerically, and prototype of the presented antenna is fabricated and tested. The measured results show that the antenna has a bandwidth of 37.5% (3.9 GHz-5.7 GHz) for return loss less than -10 dB and 34.7% (3.8 GHz-5.4 GHz) for average axial ratio (AR) less than 3 dB. The proposed antenna provides good CP performance.
A new method to find the Geometrical Optics/Uniform Theory of Diffraction reflection points over Non Uniform Rational B-Splines surfaces is presented. The approach is based on the Particle Swarm Optimization (PSO) technique, and the cost function used to find the reflection points is based on Snell's law. The technique can be used as an alternative to classic minimization techniques in cases where convergence problems arise.
A new framework for target detection in synthetic aperture radar (SAR) images is proposed. We focus on the task of locating reflective small regions using scattering centers model and clustering algorithm. Unlike most of the approaches in target detection, we address an algorithm that incorporates total variation filtering and mean shift clustering instead of parameter estimation. Our approach is validated by a series of tests on real SAR images and compared with other target detection algorithms, demonstrating that it configures a novel and efficient method for target-detection purpose.
We study the Doppler features of electromagnetic scattering from a wind turbine with rotating blades in the presence of ground. Image theory in conjunction with a shooting-and-bouncing ray code, Ahilo, is used to carry out the dynamic signature simulation. The observed features in the simulation are corroborated with laboratory measurements. In addition, the Doppler features from a wind turbine in the presence of a moving ground is simulated and analyzed.