In this paper, a compact and simple microstrip-fed slot antenna is proposed for ultra-wideband (UWB) applications, which consists of a circular patch and an open T-slot to realize the microstrip-line to slot transition well over a widened frequency range. The simulations and measurements show that this simple structure with the novel design generates a broadband impedance bandwidth of 10dB return loss from 2.5 to 12.5 GHz (BW=133.3%) adjustable by variation of its parameters. Details of the antenna design and experimental results of the constructed prototype are presented. In addition, a geometric parameters study of the proposed antenna is able to provide more useful information for antenna design.
A uniform asymptotic solution is presented for evaluating the field diffracted by the edge of a lossy double-negative metamaterial layer illuminated by a plane wave at skew incidence. It is given in terms of the Geometrical Optics response of the structure and the transition function of the Uniform Geometrical Theory of Diffraction, and results easy to handle. Its accuracy is well-assessed by numerical tests and comparisons with a commercial solver based on the Finite Element Method.
A novel broadband Van Atta array operating in a broadband with frequency offset characteristic is proposed. A single sideband mixer is introduced to achieve sideband choice without utilizing filters which make this array have excellent performance and wider applications than the conventional Van Atta array. The simulated results of the amplitude and phase of the array show that this antenna array can achieve retrodirectivity with frequency offset and good isolation in a broadband. The experimental performance of the array is observed within the frequency range from 2.8 GHz to 3.4 GHz.
Existence of backward electromagnetic surface waves at an interface separating a semi-infinite uniform left-handed metamaterial and a 1D photonic crystal composed of alternating layers of two kinds of single-negative (ε-negative and μ-negative) metamaterial is theoretically investigated. Dispersion characteristics of surface states are analyzed for two different cases of ENG-MNG and MNG-ENG layered periodic structures. It was demonstrated that in the presence of metamaterial, surface waves are sensitive to light polarization and there exist only backward TM-polarized (or TE-polarized) surface Tamm states depending on the ratio of the thicknesses of two periodic stacking layers.
Compact dual-band bandpass filter (BPF) with wide and narrow bands simultaneously is presented. By using the stepped impedance resonators (SIRs) in multilayered structure, the dual-band responses with wide and narrow bands simultaneously can be obtained. The filter has 3-dB fractional bandwidths (FBWs) of 45% and 10% for 2.4 GHz and 5.2 GHz, respectively. The circuit size is compact due to the multilayered structure. Moreover, multi-path propagation inside the multilayered structure generates transmission zeros at each skirt of the passbands for improving the passband selectivity. Measured results of the filter are in good agreement with the full-wave electromagnetic (EM) simulation.
A new miniaturized bandpass fractal frequency selective surface (FSS) with excellent angular stability performa nce is proposed. The minia turization has been achieved by scheming out a symmetric fractal pattern of continuous slots from the surface of a square-shaped patch, in which each periodic cell consists of incurved slot resonator for reducing the cell size. Reduction in FSS size of up to 74% with respect to the conventional square loop aperture FSS operating at the same frequency of 3.3 GHz is obtained. Furthermore, results show excellent angular stability for both vertica land horizontal polarization at different incidence angles because of its fractal configuration. A prototype is fabricated and the FSS measurement, and simulation results are presented and discussed.
To predict the three-dimensional radar cross section (RCS) pattern of an arbitrary shaped perfectly electric conductor objects in both a broad frequency band and angular domains simultaneously, the method of moments (MoM) combined with the Chebyshev polynomial approximation is presented. The induced current is expanded by a bivariate Chebyshev series. Using this function, the induced current can be obtained at any frequency and angle within the desired frequency band and angular domains. Numerical results show that the proposed method is found to be superior in terms of the CPU time to obtain the three-dimensional RCS pattern compared with the direct solution by MoM repeating the calculations at each frequency and angle. Good agreement between the presented method and the direct MoM is observed.
The frequency responses of two widely used active inductor topologies are analyzed and compared using a generalized circuit model for the active devices in the circuits. A very wideband active inductor in CMOS was subsequently fabricated and tested and the inductor exhibits a measured self-resonant frequency of 9.7 GHz.
This work investigates the variation of the real part of the complex magnetic permeability of a Ni-Zn ferrite for application to temperature sensors. Ferrite samples were fabricated by means of the conventional ceramic method. Zinc, nickel and iron oxides were used as raw materials. The samples were sintered at 1200, 1300, and 1400oC. The complex magnetic permeability of the samples was measured at temperatures ranging from -40oC to +50oC. The complex magnetic permeability of the samples was analyzed in the 100 kHz--100 MHz frequency range, and the temperature sensitivity of the magnetic permeability (μr'/T) was analyzed at 100 kHz. The magnetic permeability variation of the ferrite permits to use it as a temperature transducer with a maximum temperature sensitivity of about -119oC-1. The highest magnitudes of temperature sensitivity occurred between +30oC and +50oC. Therefore, the ferrite could be sensitive enough to allow temperature measurements at the human body temperature level. The results indicate that the temperature range of maximum temperature sensitivity of the ferrite may be adjusted by means of appropriate selection of the fabrication parameters.
In this article, a novel wideband planar monopole antenna for applications in 2.4 GHz WLAN and UWB bands is presented and investigated. The proposed antenna is composed of a gourd-like radiation element fed by a 50 Ohm microstrip line and a step-shaped ground plane. A pair of slot lines is etched symmetrically on the ground plane to obtain the 5 GHz band-notched characteristic, and the notched band can be tuned. The proposed antenna is successfully simulated, designed, and measured. The measured results agree reasonably with the simulated ones. According to the measured results, the proposed antenna yields a wide bandwidth ranging from 2.2 to 11 GHz for VSWR less than 2, except the notched band of 5.1-6.2 GHz for 5 GHz WLAN. Moreover, it exhibits nearly omnidirectional radiation patterns, stable gain, and small group delay variation across the operation band, which meets the requirements of 2.4 GHz WLAN and UWB applications.
Stealth characteristic of two dimensional cylinder plasma envelopes is studied. Three cases about plasma refraction effect, reflection characteristic and attenuation by absorbing electromagnetic wave (EMW) are concerned synthetically. As for plasma refraction stealth, EMW traces equation in cylinder plasma is deduced; a novel concept of plasma refraction deviation angle is presented; the relation between refraction deviation angle and incidence angle of EMW is yielded; the relation between refraction deviation angle and plasma density distribution is made out. As for reflection stealth and attenuation stealth, reflection calculation of multi-layer plasma is presented first, and plasma collision frequency as well as corresponding collision absorption is taken into account simultaneously, then EMW reflectivity with double-path attenuation is obtained. It is shown that cylinder plasma envelopes considering the three cases above could make distinct stealth.
In this paper, a novel dual-band rectangular slot antenna for wireless local area network (WLAN) applications in IEEE 802.11b/g/a systems is presented. The proposed antenna, fed by a 50Ω microstrip line, has size of 32 mm×28 mm×1.6 mm. By introducing a pair of U-shaped strips, the proposed antenna can generate two separate impedance bandwidths. The prototype of the proposed antenna has been successfully constructed and tested. The low-band resonant frequency is located at about 2.4 GHz, with -10 dB impedance bandwidth from about 2.3 to 2.5 GHz. The high-band resonant frequency is located at about 5.7 GHz, with -10 dB impedance bandwidth from about 4.9 to 6.0 GHz. In addition, the measured results show good radiation characteristics at the two operating bands, proving the dualband operation of the proposed antenna.
A multiresonance double cross element is used to design a dual-band reflectarray with dual linear polarization. The proposed element has a single conductive layer structure which makes it easy to manufacture. The results presented in this paper show that the mutual effect between the elements of the two bands is negligible. Hence, it is easy to achieve the phase compensation for each band separately. The simulated and measured results for an element designed to cover the X- and K-bands have confirmed the suitability of the proposed element to build a dual-band reflectarray.
This paper shows that L-shaped monopole antenna on PPS manufactured by inkjet printing of nano silver ink is able to produce very competitive overall antenna performance against Rogers copper foil structures if the thickness of the printed conductor layer is about the skin depth at the operating frequency multiplied by four.
This work proposes the use of Non-Bianisotropic Split Ring Resonators (NB-SRRs) as building blocks for dual-band response filters. Design parameters will be evaluated in order to characterize coupling mechanisms for both the particle and filter structure. A ready-to-use dual-band filter for a multiconstellation Galileo/GPS global positioning receiver is manufactured in order to validate and test the proposed design. The device transmission response measurement agrees with both circuital and electromagnetic simulations, as well as with theoretical insertion losses, which are 2.4 dB and 3.5 dB at center passbands for L5 and L1 bands respectively.
A novel circularly polarized microstrip rectenna operating on C-band with low profile is proposed. The input and output match networks of the rectifying circuit are realized by λ/4 microstrip lines and open stubs with the harmonics being inhibited. The circularly polarized receiving antenna is a truncated-corner square patch fed by microstrip line with DGS (Defect Ground Structure) for suppressing high order harmonics further. The voltage of 4.34V on the load of 298 Ω is measured and the overall RF-DC conversion efficiency of 68.4% is obtained. This kind of rectenna can be extended to large arrays for wireless power transmission applications.
A novel design of multiband microstrip antenna array with dumbbell shape defected ground structure (DGS) is presented. The DGS is inserted into the ground plane between the two elements of the antenna array in order to suppress mutual coupling. Both simulation and measurement results verified that the DGS had improved the radiation properties of the antenna array. Measurement results of the DGS antenna showed mutual coupling reduction of maximum 5 dB and gain enhancement to 3 dB.
The thermal noise of the resistive vee dipole (RVD) has been analyzed using a numerical model based on the method of moments. The RVD analyzed in this paper has curved arms and is loaded with surface-mount chip resistors, which approximate a modified Wu-King profile. The total noise power delivered to a 200 Ω feed line and the contribution of individual resistors to the total noise power are presented. The results show that the noise temperature of the RVD is very high and the resistors close to the drive point contribute more to the total noise power than do the resistors close to the open ends of the antenna arms.
This paper addresses the problem of direction of arrival and time delay estimation, and derives multi-invariance MUSIC (MI-MUSIC) algorithm therein. The proposed MI-MUSIC, which only requires one-dimension searching, can avoid the high computational cost within two-dimension MUSIC (2D-MUSIC) algorithm. It means that MI-MUSIC algorithm has better performance than that of ESPRIT and MUSIC, and also can be viewed as a generalization of MUSIC. Simulation results verify the usefulness of our algorithm.
The thermostability and density of water-salt solutions of DNA, irradiated by non thermal coherent millimeter electromagnetic waves with frequency 64.5 GHz have been investigated using the methods of spectrophotometry and densitometry. It is shown that the thermostability of DNA and density of its solutions are increased, depending on time of irradiation. It is expected that under the influence of millimeter electromagnetic radiation the hydration of DNA and ions of Na+ that are present in solution decrease. As a result, the physicochemical characteristics of DNA are changed.