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  • Articles  (1,845)
  • 2015-2019  (1,845)
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  • Articles  (1,845)
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  • 1
    Publication Date: 2019-12-28
    Description: A 2 × 2 MIMO antenna for metal-housing mobile handset application is proposed in this article. The polarization diversity is used to arrange the two antennas’ setup. The asymmetric U-shaped nonuniform slot antenna provides two different resonant bands are designed to be operated in long term evolution (LTE) covers lower band (698 MHz to 960 MHz) and upper band (1710 MHz to 2700 MHz). The modified type III balun is used for upper-operating band, and the open stub is used for lower-operating band, good impedance bandwidth, and radiated pattern and efficiency are shown. The isolation (S21) between the antennas is more than 20 dB, and the envelope correlation coefficient (ECC) is less than 0.02. A prototype of the proposed antenna chiselling in the metal-housing mobile handset (with 160 mm in length, 10 mm in height, and 70 mm in width) is fabricated and experimentally studied.
    Print ISSN: 1687-5869
    Electronic ISSN: 1687-5877
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 2
    Publication Date: 2019-12-27
    Description: This paper addresses the issues of low bandwidth, gain, and efficiency of miniaturized microwave antennas by proposing a novel wideband dual-frequency coplanar waveguide antenna design based on a simplified composite right/left-handed (SCRLH) transmission line structure with Hilbert curve loading. The multifrequency characteristics of the SCRLH transmission line structure are evaluated theoretically, and the antenna parameters promoting bandwidth broadening under zeroth-order resonance (ZOR) and first-order resonance (FOR) mode operation are evaluated. The bandwidth broadening in the ZOR and FOR modes is accordingly revealed to be independent of the antenna length, and the structure therefore facilitates wideband operation under miniaturization. Finally, the dual-frequency ZOR and FOR mode antenna design with center frequencies of f0 = 1.865 GHz and f1 = 2.835 GHz is validated via simulation, and the performance of a compact prototype antenna is evaluated experimentally. The −10 dB return loss bandwidths at f0 and f1 are 187 MHz (from 1.773 GHz to 1.96 GHz) and 368 MHz (from 3.002 GHz to 3.37 GHz), and the corresponding relative bandwidths are 10.1% and 11.5%, respectively. The experimentally measured peak gains and radiation efficiencies at f0 are 1.54 dB and 81.3%, respectively, and those at f1 are 1.71 dB and 74.2%, respectively.
    Print ISSN: 1687-5869
    Electronic ISSN: 1687-5877
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 3
    Publication Date: 2019-12-27
    Description: In this paper, the Gaussian mixture model (GMM) is introduced to the channel multipath clustering. In the GMM field, the expectation-maximization (EM) algorithm is usually utilized to estimate the model parameters. However, the EM widely converges into local optimization. To address this issue, a hybrid differential evolution (DE) and EM (DE-EM) algorithms are proposed in this paper. To be specific, the DE is employed to initialize the GMM parameters. Then, the parameters are estimated with the EM algorithm. Thanks to the global searching ability of DE, the proposed hybrid DE-EM algorithm is more likely to obtain the global optimization. Simulations demonstrate that our proposed DE-EM clustering algorithm can significantly improve the clustering performance.
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    Electronic ISSN: 1687-5877
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 4
    Publication Date: 2019-12-24
    Description: Due to the difficulties in actual measurement of sea clutter and uncertainties of experimental data, the electromagnetic (EM) scattering model becomes a better alternative means to acquire the sea clutter. However, the EM scattering model still faces the problems of huge memory consumption and low-computational efficiency when dealing with the large size of sea surface or the long time case. Thus, this paper presents a statistical model to simulate the temporal-spatial correlated three-dimensional (3D) sea clutter, which is based on the statistical properties obtained from the EM scattering model, such as probability density function and correlation function. The comparisons show that the texture feature, autocorrelation function, and PDF of the sea clutter simulated by the statistical model have a good agreement with the results given by the EM model. Furthermore, the statistical model is with high efficiency and can be used to simulate the large scene or long time temporal-spatial correlated 3D sea clutter.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 5
    Publication Date: 2019-12-24
    Description: We address the two-dimensional direction-of-arrival (2-D DOA) estimation problem for L-shaped uniform linear array (ULA) using two kinds of approaches represented by the subspace-like method and the sparse reconstruction method. Particular interest emphasizes on exploiting the generalized conjugate symmetry property of L-shaped ULA to maximize the virtual array aperture for two kinds of approaches. The subspace-like method develops the rotational invariance property of the full virtual received data model by introducing two azimuths and two elevation selection matrices. As a consequence, the problem to estimate azimuths represented by an eigenvalue matrix can be first solved by applying the eigenvalue decomposition (EVD) to a known nonsingular matrix, and the angles pairing is automatically implemented via the associate eigenvector. For the sparse reconstruction method, first, we give a lemma to verify that the received data model is equivalent to its dictionary-based sparse representation under certain mild conditions, and the uniqueness of solutions is guaranteed by assuming azimuth and elevation indices to lie on different rows and columns of sparse signal cross-correlation matrix; we then derive two kinds of data models to reconstruct sparse 2-D DOA via M-FOCUSS with and without compressive sensing (CS) involvements; finally, the numerical simulations validate the proposed approaches outperform the existing methods at a low or moderate complexity cost.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 6
    Publication Date: 2019-12-23
    Description: This paper presents the design of nose-cone conformal substrate-integrated waveguide (SIW) slot array antenna for modern radar applications. Firstly, the wave propagation characteristics have been investigated in doubly curved SIW, and it has been observed that they are non-uniform along the longitudinal direction of nose-cone conformal SIW. To ensure the constant wave propagation along the length of conformal SIW, the conventional design of SIW is reformulated for nose-cone conformal SIW and circuit model modification has been demonstrated. Secondly, the procedure for designing a SIW-based array on curved surfaces has been developed. In the proposed design, rectangular waveguide (RWG) to SIW feeding structure has been used to avoid spurious radiations. Finally, 1 × 6 element-based nose-cone conformal slotted array has been designed and compared with planar and cylindrical conformal arrays. It has been observed from the results that the nose-cone conformal slot array offers low sidelobe levels (SLLs) and high gain. For the validation of the proposed design, the conformal slotted array has been fabricated and measured, which exhibited a reasonable agreement between the measured and the simulated data.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 7
    Publication Date: 2019-12-21
    Description: In this paper, fitness-associated differential evolution (FITDE) algorithm is proposed and applied to the synthesis of sparse concentric ring arrays under constraint conditions, whose goal is to reduce peak sidelobe level. In unmodified differential evolution (DE) algorithm, crossover probability is constant and remains unchanged during the whole optimization process, resulting in the negative effect on the population diversity and convergence speed. Therefore, FITDE is proposed where crossover probability can change according to certain information. Firstly, the population fitness variance is introduced to the traditional differential evolution algorithm to adjust the constant crossover probability dynamically. The fitness variance in the earlier iterations is relatively large. Under this circumstance, the corresponding crossover probability shall be small to speed up the exploration process. As the iteration progresses, the fitness variance becomes small on the whole and the crossover probability should be set large to enrich population diversity. Thereby, we construct three variation strategies of crossover probability according to the above changing trend. Secondly, FITDE is tested on benchmark functions, and the best one of the three strategies is determined according to the test results. Finally, sparse concentric ring arrays are optimized using FITDE, of which the results are compared with reference algorithms. The optimization results manifest the advantageous effectiveness of FITDE.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 8
    Publication Date: 2019-12-21
    Description: In this paper, a novel design of compact microstrip antenna (MA) using an embedded λ/4 resonator is presented. By utilizing the strong coupling between the λ/4 resonator and the radiation patch of MA, the resonant frequency of MA can be decreased. Besides, the λ/4 resonator is embedded in the patch, which does not enlarge the whole size of MA. Therefore, a compact antenna can be realized. In this paper, after the principle is stated, a sample antenna has been manufactured and measured to prove the predicted characteristics of our proposed antenna. The measurement agrees well with the simulation. Hence, the proposed method in this paper is quite suitable for the design of a compact antenna.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 9
    Publication Date: 2019-12-20
    Description: A design of 38 GHz planar phased patch array with sidelobe suppression for data-rate enhancement is proposed in the paper. The proposed array is formed of three 24-element subarrays of patches. Each patch has its own transmit/receive modules (TRM) consisting of a digitally controlled attenuator and phase shifter. In order to achieve high data-rate communications, the noise, especially due to the undesired signals received from the sidelobes, should be reduced with high sidelobe suppression of subarray. The sidelobe suppression of the proposed subarray is first improved to 17.92 dB with a diamond-shaped aperture and then better than 35 dB with a tapered radiation power distribution. The excellent sidelobe suppression of the antenna array is essential for the beam-division multiplexing applications when the signal sources are close to each other. The proposed design is validated experimentally, including the data-rate measurements showing that the 7 Gbps data transmission can be achieved with sufficient sidelobe suppression of the proposed design.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 10
    Publication Date: 2019-12-20
    Description: This paper presents a novel dual-band circularly polarized patch antenna for precise satellite navigation. The radiation elements are composed of the inner cross-shaped patch and the outer annular patch which are printed on the same surface of one substrate. Two patches work in different bands, respectively, and emit dual-band circularly polarized radiation. In order to obtain a more compact antenna to meet the application of precise satellite navigation, we vertically place four metal cylinders under the ends of the cross-shaped patch to form four capacitive loadings to lower the resonant frequency of the inner cross-shaped patch. A capacitive coupling feed structure is used to match the input impedance of a patch antenna and make the antenna compact enough. The simulated and measured results show that the proposed antenna can produce appropriate dual-band circularly polarized radiation patterns for precise satellite navigation. The measured results of the antenna illustrate that maximum RHCP gain of the antenna is 4.72 dBi in the low band and 3.98 dBi in the high band, the 3 dB gain bandwidth is 70 MHz in the low band and 65 MHz in the high band.
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    Topics: Electrical Engineering, Measurement and Control Technology
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