Current Issue : April - June Volume : 2014 Issue Number : 2 Articles : 8 Articles
This paper proposes a 2D pattern synthesis algorithm for cylindrical array. According to the geometric characteristic of cylinder,\r\nwe can regard a cylindrical array as an equivalent linear array whose elements are identical circular subarrays. Therefore, the beam\r\npattern can be obtained by the product of the array factor of linear array and beam pattern of circular subarray. Then, the 2D\r\nbeamforming can be realized by two 1D beamforming processes.We can prove that the complex excitation vector of a cylindrical\r\narray is the Kronecker product of linear array�s weight vector and circular array�s weight vector. By this algorithmof decomposition\r\nand reconstruction, the computational complexity of 2D beamforming could be significantly reduced. Finally, simulation results\r\nfurther illustrate the validity of the proposed method....
Directional ultrawideband (UWB) antennas are popular in wireless signal-tracking and body-area networks. This paper presents a\r\nstacked microstrip antenna with an ultrawide impedance bandwidth of 114%, implemented by introducing defects on the radiating\r\npatches and the ground plane. The compact (20 Ã?â?? 34mm) antenna exhibits a directive radiation patterns for all frequencies of\r\nthe 3ââ?¬â??10.6GHz band. The optimized reflection response and the radiation pattern are experimentally verified.The designed UWB\r\nantenna is used to maximize the received power of a software-defined radio (SDR) platform. For an ultrawideband impulse radio\r\nsystem, this class of antennas is essential to improve the performance of the communication channels....
A novel stealth design method for X-band Vivaldi antenna arrays is proposed in this paper by ladder arrangement along radiation\r\ndirection. Two-element array, eight-element array, and 3 Ã?â?? 7-element array are investigated in this paper. S parameters, RCSs,\r\nand radiation patterns are studied, respectively. According to the ladder arrangement of Vivaldi antennas presented, 16.3 dBsm\r\nmaximal RCS reduction is achieved with satisfied radiation performance. As simulated and measured, results demonstrate that the\r\neffectiveness of the presented low RCS design method is validated....
Ship surveillance using space-borne synthetic aperture radar (SAR), taking advantages of high resolution over wide swaths and\r\nall-weather working capability, has attracted worldwide attention. Recent activity in this field has concentratedmainly on the study\r\nof ship detection, but the classification is largely still open. In this paper, we propose a novel ship classification scheme based on\r\nanalytic hierarchy process (AHP) in order to achieve better performance.The main idea is to apply AHP on both feature selection\r\nand classification decision. On one hand, the AHP based feature selection constructs a selection decision problem based on several\r\nfeature evaluation measures (e.g., discriminability, stability, and information measure) and provides objective criteria to make\r\ncomprehensive decisions for their combinations quantitatively. On the other hand, we take the selected feature sets as the input\r\nof KNN classifiers and fuse the multiple classification results based on AHP, in which the feature sets� confidence is taken into\r\naccount when the AHP based classification decision is made. We analyze the proposed classification scheme and demonstrate its\r\nresults on a ship dataset that comes from TerraSAR-X SAR images....
A simple and exact closed-form equation to determine a penetrated ray path in a ray tracing is proposed for an accurate channel\r\nprediction in indoor environments.Whereas the penetrated ray path in a conventional ray tracing is treated as a straight line without\r\nrefraction, the proposed method is able to consider refraction through the wall in the penetrated ray path. Hence, it improves the\r\naccuracy in ray tracing simulation. To verify the validation of the proposed method, the simulated results of conventional method,\r\napproximate method, and proposed method are compared with the measured results. The comparison shows that the proposed\r\nmethod is in better agreement with the measured results than the conventional method and approximate method, especially in\r\nhigh frequency bands....
A novel direction-of-arrival (DOA) estimation method is proposed based on the sparse cumulants fitting without redundancy.\r\nFirstly, we derive that some fourth order cumulants of the array output are redundant and therefore are removed to reduce\r\ncomputational complexity. Then, the left cumulants are sparsely represented on an overcomplete basis and the DOAs are resolved\r\nby using a software package. Despite introducing a high variance, the proposed method shows several advantages including the\r\nability to detect more sources than sensors, high resolution, and robustness to all kinds of Gaussian noise. Besides, our method\r\ndoes not have to know, a priori, the number of sources. Simulation results are presented to illustrate the effectiveness and efficiency\r\nof the proposed method...
The performance of the multiantenna systems can be deeply affected by the antenna layout, that is, the placement of the antenna\r\nelements in a given area. This paper focuses on the optimal antenna layout which can maximize the ergodic capacity of a multiinput\r\nsingle-output (MISO) beamforming system. Since the optimization problem cannot be solved analytically, we use simulated\r\nannealing (SA) algorithm to search for the optimal antenna layout.The results show that the optimal antenna layout depends highly\r\non the power azimuth spectrum(PAS) distribution and power elevation spectrum(PES) distribution. In the three-dimensional (3D)\r\nspace uniformly scattering environment, the optimal antenna layout will locate the antenna elements on the surface of a sphere.\r\nWhen the scattering is concentrated in a two-dimensional (2D) plane, the circular layout is the optimal and finally, when there is\r\nno scattering (single plane wave), the optimal layout is the nonuniform linear array....
This paper investigates annular or circular ring microstrip patch antennas and the fundamental terms related to design aspects and study of antenna. Like many variations of microstrip patches, circular ring has received considerable attention due to its broadband nature and smaller circular counterparts. In this paper mathematical analysis of annular ring patch antenna with design is presented and studied. The demand of circularly polarized annular ring patch antennas (ARMSAs) has increased drastically in multi-band systems, satellite communication, and mobile communication applications and also in medical applications. Here the researches on this antenna are summarized and analyzed from literature....
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