A novel and compact triple-band Y-shaped monopole antenna with dual-polarization characteristics is proposed. The antenna is composed of a partial ground and a microstrip-fed radiating patch that consists of two unequal monopole arms and a circle monopole. The antenna is able to generate three separate impedance bandwidths of 230 MHz (2.30-2.53 GHz), 170 MHz (3.38-3.55 GHz), and 4170 MHz (4.35-8.52 GHz), which can cover both of the WLAN bands (2.4 and 5.8 GHz) and WiMAX band (3.5 GHz). By utilizing different lengths of monopoles, two circularly polarized bands at 2.4 GHz and 5.8 GHz are realized. Moreover, the antenna exhibits monopole-like radiation patterns and stable antenna gains across the operating bands. The effect of the antenna's key structural parameters on its performance was also analyzed.
In this paper, a miniaturized Vivaldi antenna for C- to X-bands is proposed and fabricated. An H-Shaped Resonator (HSR) and transverse slot structures are employed in this design, which improve the gain through the entire band, especially at the higher frequency band. These simulated results show that the modified Vivaldi antenna has a maximum gain increment of 4 dBi and maximum gain of 9.9 dBi. Furthermore, the modified Vivaldi antenna has narrower half-power beam width (HPBW), higher front-to-back ratio (FBR) and better radiation characteristics. The proposed antenna is fabricated and measured to validate the design. The measured results are in good agreement with the simulated ones.
This paper presents a compact size crossover device based on the cascade of branch-line sections. With the aim of reducing its size, some of the transmission lines of the structure have been replaced by its equivalent artificial transmission line (ATL). The obtained size reduction is above 30%, and the electrical performance of the proposed structure presents an isolation better than 20 dB in a FBW=34.5% and a crossover bandwidth better than 2 dB of FBW=51.5%. Also the good magnitude and phase balance performance must be highlighted.
In this paper, we design an optical filter by using one-dimensional (1D) ternary metallo-dielectric photonic crystal (PC). We use a dielectric defect layer between ternary asymmetric cells with this structure (ABC)NDM(ABC)N and also increase the number of dielectric defect layers. Then, we plot transmission spectra in terms of wavelength and different angles of incidence in transverse electric (TE) and transverse magnetic (TM) polarizations. We show defect modes and photonic band gap (PBG) on the plane of wavelength and incident angles in both TE and TM polarizations. We also plot transmission in the lossless structure and compared loss and lossless structures. Furthermore, we compare dielectric defect layer with metallic defect layer in both TE and TM polarizations. Moreover, we plot symmetric structure (ABC)NDM(CBA)N in TE and TM waves. The theoretical analysis shows that there is one defect mode which moves to the shorter wavelength by increasing angles of incidence in asymmetric structure. There are also two defect modes in symmetric structure, and by tuning angle of incidence this structure can be used as single channel filter in asymmetric structure and multichannel filter in symmetric structure.
A dual-broadband circularly polarized (CP) antenna with compact structure 97 × 97 × 0.8 mm3 is proposed. The measured -10 dB return loss bandwidth is 0.38 GHz (0.75-1.13 GHz) for UHF band and 0.81 GHz (2.32-3.13 GHz) for ISM 2.4 GHz band. The measured 3 dB axial ratio bandwidth is about 0.235 GHz (0.83-1.065 GHz) for UHF band and 0.34 GHz (2.36-2.7 GHz) for ISM band. The antenna consists of a feedline, patch, Stepped slot-1 and -2, a pair of orthogonal rectangular slots (H/V slot), and L-slot. There are two advantages for the proposed antenna: broadband and independent adjusting for UHF and ISM 2.4 GHz bands. The proposed antenna is a good candidate for worldwide RFID reader antenna.
The effects of highly out-of-band electromagnetic interference (EMI) on an RF front-end are experimentally evaluated. Irradiation at 60 GHz with a moderate power is produced in the near-field owing to an open-ended WR15 waveguide fed by a Gunn diode. Surprisingly, we easily obtain the remote extinction of either the transmitter or the receiver of the front-end subject to EMI. The paper proposes a detailed analysis of both CW and chopped EMI by varying almost all experimental conditions, namely the polarization, target distance, and chopping mode. The latter shows most efficiency and evidences some long time scale dynamics in the induced perturbation.
A novel low-index metamaterial lens (LIML) used for wideband circular polarization antenna is proposed. By introducing gradual spaces between metamaterial elements, one can achieve a much wider bandwidth than the equally spaced situation can do. Starting with a planar equiangular spiral antenna with reflector, we demonstrate the design idea of this LIML. By using the specially designed LIML, the ultimate antenna can achieve an obvious gain improvement of 2 dBi and a wide axial ratio bandwidth of 44% (from 6.9 GHz to 10.8 GHz). A prototype is fabricated, and the measured results agree well with the simulated ones.
This article proposes a novel ship detection method for high-resolution SAR images. Our goal is to look at this question from a information geometry point of view. The method consists of two steps: construction of revised metric and Riemann structure, and extraction of targets. For the first step of the process, a revised metric is introduced on Gamma 2-manifold. We construct a special Riemannian structure by using the proposed metric. For the second step, the regions of interest (ROIs) are extracted out based on the Riemann structure. Experimental results of the detection method on SAR images show that the algorithm presented is effective.
In this paper, a compact reconfigurable monopole antenna is proposed working at three different frequencies depending upon the condition of the optical switch. The proposed reconfigurable antenna in the state of ON switchhas resonant frequencies of 2.45 GHz and 5.4 GHz covering the band of 1.8-2.7 GHz (Wi-Fi) and 5.26-5.99 GHz (WLAN) respectively. The same antenna during OFF state of switch operates only at 3 GHz covering the band of 2.49-3.84 GHz. The proposed multiband reconfigurable antenna is designed and fabricated on an FR-4 substrate having relative permittivity of 4.4, loss tangent of 0.02 and thickness of 1.6 mm. The antenna is fabricated and tested in the laboratory to validate the simulated results. A good agreement between the simulated and measured results is obtained in term of radiation pattern and return loss. The performance of the reconfigurable antenna under both states of switch is examined on the basis of the antenna parameters such as return loss, radiation pattern and gain.
A portable spectra detection system has been developed to enable reflection measurement. This system is mainly composed of spectrometer, LED source and five optical elements. The size of the optical system is about 126 mm × 72 mm × 30 mm. The system covers a range of 340 nm-820 nm, and the spectral resolution is 6.0 nm. Based on the detection system, two example applications for ripeness detection and real-finger identification are carried out to demonstrate the system performance. The detection time is less than 1 second, and a satisfactory agreement was observed between detection results and realistic situation.
In this paper, a novel M-shaped UWB Vivaldi array antenna is presented. First of all, a simple M-shaped UWB Vivaldi antenna is designed, and its properties of return loss, radiation pattern, VSWR, gain, etc. are analyzed. An array of M-shaped UWB antenna is simulated and designed after the successful implementation of the simple UWB Vivaldi antenna. The designed antenna has operating frequency from 3.25 GHz to 8.85 GHz covering 5.6 GHz bandwidth. The antenna has flat gain over entire frequency range. The proposed antenna is fabricated on a commercially available FR-4 substrate having relative permittivity of 4.4 and height of 1 mm. The proposed antenna has wide band and good flat gain over entire frequency range. The proposed antenna can be used in next generation wireless communication because of its efficiency, gain and wide bandwidth.
The paper presents the application of a hybrid neuro-fuzzy model for the analysis and synthesis of a square multiband Sierpinski carpet fractal antenna. For the analysis model, the antenna geometrical parameters were taken as the input, and the resonant frequencies were obtained as the output while for the synthesis model, the resonant frequencies were taken as the input, and geometrical parameters were obtained as the output. Also, a model was trained to obtain the return loss characteristics for the given set of geometrical parameters. The developed model was validated by comparing the resonant frequencies and radiation patterns of the simulated and fabricated antennas.
Based on the complex analysis of the Lossy Transmission Line Theory, which involves the result of a Generalized Smith Chart, a new version of the last one arises when trying to characterize the wave impedance along the Transmission Line by means of analytical complex functions. Among these functions, the complex logarithm of the reflection coefficient leads to the logarithmic-reflexion coefficient-plane and its parameterized version, the Logarithmic Generalized Smith Chart. This plane is specially useful for characterizing the Transmission Line along its extension. To validate these results, some examples will be presented providing physical interpretations to the behaviour of a lossy TL and pointing out some practical applications.
In this paper a method for a fast synthesis of planar, maximally thinned and steerable arrays is proposed and tested on several benchmarks available in literature. The method optimizes simultaneously the weight coefficients and sensor positions of a planar array without using global optimization schemes, properly exploiting convex optimization based algorithms. The resulting arrays are able to radiate a steerable beam pattern, satisfying a prescribed power mask and avoid to constraint the fitting of any a priori assigned reference field pattern. Although such a method takes into account the general case of sparse arrays, this letter is focused on the case of thinned arrays as a special case of sparse ones, since the initial grid to thin on has only half-wavelength distances. Such a feature allows a faster synthesis than in the general case of sparse arrays.
In this article, a pair of T-shaped stepped-impedance-stubs plays a key role in the structure of a Wilkinson power divider. In the first step, to find a general relation between electrical lengths and characteristic impedances of the mentioned stubs and consequently how the operating frequency can be chosen, an equation based on a mathematical analysis is obtained. Then, by using this equation several miniaturized Wilkinson power dividers with the same configurations at different operating frequencies and capable of suppressing spurious frequencies are designed. Moreover, in each of these circuits 2nd to 16th unwanted frequencies are suppressed. The simulation results of the designed dividers are in good agreement with the expected responses predicted by the obtained equation. To validate the proposed method, a Wilkinson power divider at 0.85 GHz as a sample is fabricated, and 77.83% size reduction is obtained. Furthermore, the fabricated divider suppresses 3rd to 21st harmonics better than -20 dB.
In order to improve the performance of antenna array beamforming, a semi-virtual antenna array beamforming method is proposed based on covariance matrix expansion. The sample covariance matrix is expanded, and virtual array elements are formed. The performance of the semi-virtual antenna array beamforming method is as good as the virtual antenna array beamforming methods, which are better than the conventional adaptive beamforming methods. In addition, the computational complexity of the semi-virtual antenna array beamforming method, which is greatly reduced compared with the virtual antenna array beamforming methods, is equal to that of the conventional adaptive beamforming methods. The fast calculation method of the optimal weight vector of the semi-virtual antenna array beamforming method is given in this paper. The validity and applicability of the proposed method is verified by simulation results.
This paper presents the design of a wideband blade shaped monopole antenna with a horizontally mounted aluminium tube on top of the blade covering 135-175 MHz frequency band using Electromagnetic Simulation software (CST Microwave StudioTM) along with a matching network whose characteristics have been evaluated by the Optimal Matching Network Identifier (OMNI) algorithm. OMNI algorithm is a search technique used in computing, to find out the optimum solution. The conventional quarter wavelength monopole antenna is a narrow band antenna with bandwidth of the order of 5% to 10% at its centre frequency. In order to increase the bandwidth of the antenna, a proper matching network has been incorporated along with it. Toroidal inductor based matching networks have been designed, and their characteristics are evaluated using Optimal Matching Network Identifier (OMNI) program in MATLAB software. By consolidating MATLAB and CST simulated results, the antenna prototype along with the optimal matching network has been practically implemented, and corresponding results have been verified. The details of simulated and measured results are also included. The proposed antenna finds numerous applications in various wideband communication systems.
A tri-band two-way filtering power divider structure is proposed based on HMSIW. Dual-band filtering power divider is realized by etching semicircular slots on HMSIW. The third passband is achieved by loading open-stub without affecting two other passbands. The return loss is less than -20 dB in each passband with 3 dB fractional bandwidths of 3.75%, 9.3% and 0.61%. The measured results are in agreement with the simulated ones in this paper. The filtering power divider has the advantages of simple structure, easy integration, etc. It has a good application prospect.
This paper considers the localization of an emitter where the transmitted signal is unknown for receivers. To improve the localization accuracy, we propose an efficient method to estimate the emitter position by reconstructing the transmitted signal jointly. Simulation results show that the localization performance of the proposed method is much better than the existing algorithms.
By introducing the Wilkinson divider and dual L-shaped strips as a feeding network, broadband design of planar circularly polarized (CP) annual-ring antenna for ultra-high frequency (UHF) RFID system is proposed and experimentally studied. The proposed broadband CP antenna can provide the impedance bandwidth (RL≥10 dB) of about 246 MHz (25.0% @ 985 MHz) and the 3 dB axial-ratio (AR) bandwidth of about 180 MHz (19.5% @ 925 MHz) to meet the worldwide UHF RFID band (860~960 MHz). Meanwhile, with unidirectional pattern in the XZ- and YZ-planes, the measured peak gain and radiation efficiency are about 7.7 dBic and 70% across the operating band, respectively.