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1.
A diversity antenna comprising a short whip antenna top loaded with a small cylinder and a new built-in antenna has been developed for very small portable telephones in the 800-MHz band. Wire-grid analyses and whip antenna experiments yielded good radiation characteristic results when the equivalent electrical length of the whip antenna equalled a half wavelength. The built-in antenna features extreme compactness, its size being one-third that of a conventional planar inverted-F antenna. The characteristics were investigated experimentally, and an antenna of 3.5 cc volume with a gain of -1 dBd and a bandwidth of 30 MHz was designed at 879 MHz. Finally, the diversity characteristics were subjected to field measurements and a diversity correlation of 0.26 was obtained 相似文献
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This paper proposes a dual-polarized omnidirectional antenna for base-station antennas that are mounted on the rooftops of buildings. The antenna suppresses the degradation in the received-signal level due to the inclination of mobile antennas in the personal handy-phone system (PHS). The proposed polarization-diversity antenna is comprised of a dielectric-loaded slotted-cylinder antenna for horizontally polarized waves and a conventional collinear array antenna for vertically polarized waves in a height-diversity configuration. The structure of the proposed antenna and its fundamental characteristics, such as the input impedance and radiation pattern, are shown. The change in the radio zone length (RZL) due to the inclination angle of the mobile antenna is measured to estimate the improvement offered by the proposed antenna in an urban area. It is shown that the RZLs of the collinear antennas in line-of-sight (LOS) environments are decreased by 73% when the mobile antenna is inclined at 90 , whereas the proposed polarization-diversity antenna restrains the degradation to approximately 20%, regardless of the inclination angle without downtilt and from 20% to 40% for a 15 downtilt. The RZLs of the collinear tilt antennas in non-LOS (NLOS) environments are below approximately 20%, compared to those of the collinear tilt antennas for the LOS route. We show that the RZLs in the NLOS environments are short compared to those for the LOS environments in microcell systems such as PHS with a high-elevation base station, even when the polarization-diversity technique is applied to the base station. 相似文献
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《Vehicular Technology, IEEE Transactions on》1973,22(4):110-113
Field measurements of mobile radio signals have shown that signal arrival is concentrated in elevation angles lower than 16°. This suggests use of an omnidirectional antenna with vertical directivity, instead of the usual whip antenna, to increase average signal strength as a further improvement in the advantages of diversity reception. 相似文献
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For pt.I see ibid., vol.50, no.3, p.830-44 (2001). In Part I of this two-part paper, we described the effective gain characteristics of the handset diversity antenna comprising a retractable whip antenna and a built-in planar inverted F antenna (PIFA). In order to achieve a high diversity effect, the correlation between the diversity branches must be small while at the same time maintaining a high effective gain, and this is contained in this paper. Further analysis includes an evaluation of the diversity gain with which the diversity effect shown by the analyses of the effective gain in Part I and the correlation in Part II is described. In addition, the mechanism for obtaining a small correlation coefficient is clarified by investigating the amplitude and phase radiation patterns when the whip length and the body inclination angle are changed. From these we obtain various numerical results that provide sufficient insight for design purposes. The validity of the analytical results is verified by an experiment in an indoor radio wave propagation environment 相似文献
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The development of a multiturn loop antenna for a police officer's personal radio set is described. The antenna is small, low profile, lightweight, with dimensions of2.7 times 2.7 times 0.7 in high (1.06 times 1.06 times 0.28 cm), and is tunable over the 150- to 170-MHz band. VSWR and radiation patterns are presented with the antenna mounted on a man's shoulder. The shoulder-mounted antenna characteristics are described with conditions where the man is in standing, stooping, and prone positions, with various head and arm movements, and with light and heavy clothing. Radiation patterns are referenced to a 6-in helical whip commonly used by police officers. Radiation patterns also indicate body absorption loss for loop and whip antennas mounted at waist level as compared with shoulder levels. The instantaneous bandwidth is 1.4 MHz for a VSWRleq 3:1 . A dual-frequency model for use in a two-frequency push-to-talk mode, is also shown to be practical. 相似文献
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短波通信在移动通信、遂行通信中多数使用鞭状天线利用地波进行通信。为评估短波地波传播特性,将短波地波传播模型与天线仿真技术相结合,采用矩量法计算陆地鞭状天线的辐射特性。计算结果表明,对应不同的通信距离,存在一个最佳频段。 相似文献
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Field measurements of mobile radio signals have shown that signal arrival is concentrated in elevation angles lower than 16°. This suggests use of an omnidirectional antenna with vertical directivity, instead of the usual whip antenna, to increase average signal strength as a further improvement in the advantages of diversity reception. 相似文献
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A top-loaded, inductively-coupled, electrically small antenna is designed for HF ground wave transmission. A genetic algorithm is used to optimise the antenna parameters. Two prototype antennas have been built and the test results match well with simulations. Both antennas have an electrical size kr of 0.2, greater than 65% efficiency and transmission performance within 1 dB of a commercial whip. 相似文献
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An inversion of artificial neural networks using a genetic algorithm is presented for a novel concept of optimisation applied to UWB planar antennas of bow-tie type with respect to specified values of antenna performance in the frequency range 3.1-10.6 GHz. This efficient concept is shown to achieve significant reduction in computing time for optimisation. The multidimensional inversion is characterised by a simple composite fitness or target function that includes antenna parameters as a function of signal frequency or/and angle dependence. Good impedance matching and gain performance is achieved over the whole frequency range by adequately modifying the radiating contour profile of the conventional triangular bow-tie antenna. 相似文献
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Yuehui Ouyang Love D.J. Chappell W.J. 《Vehicular Technology, IEEE Transactions on》2009,58(4):1752-1765
In this paper, we analyze the performance of novel wearable multiple-input-multiple-output (MIMO) systems, which consist of multiple electrotextile wearable antennas distributed at different locations on human clothing. For wearable applications, a semidirectional radiation pattern of the wearable patch antenna is preferred over an omnidirectional radiation of conventional dipole antennas to avoid unnecessary radiation exposure to the human body and radiation losses. Additionally, the spatial distribution of the antennas is not constrained as a typical handheld unit. Through theoretical modeling and simulation, the wearable MIMO system is shown to demonstrate a significantly higher channel capacity than a conventional system on a handheld platform (e.g., a compact dipole array or a single dipole), due to enhanced spatial diversity and antenna pattern diversity. The unique effects of antenna directivity and location on the MIMO system capacity are investigated in terms of antenna correlation and effective gain under different wireless channel models. The advantage of a wearable system over a conventional system was further confirmed by detailed physical modeling through the combination of full-wave electromagnetic and ray-tracing simulations. Finally, complex channel response matrices were measured to characterize the performance of a body-worn MIMO system in comparison with a reference full-size dipole antenna. The 319% improvement in 10% outage capacity for the body-worn system over the reference system made of a full-size dipole antenna is consistent with the 288% improvement projected by theoretical modeling and the average 300% improvement found in the physical simulation of two typical indoor scenarios. 相似文献
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Leonardo Bruno de Sá Maurício Henrique Costa Dias Antonio Carneiro de Mesquita Filho 《Circuits, Systems, and Signal Processing》2016,35(11):3811-3829
Whereas the present practice of designing matching networks for antennas is limited to conventional topologies, requiring a significant amount of domain knowledge, evolutionary algorithms can be used for automatically identifying unconventional designs that are more effective than would otherwise be developed. In this work, an automatic method to design lossless matching networks driven by an evolutionary algorithm (EA) that considers the sensitivities of the network parameters during the synthesis process is presented. To this end, a closed-form expression for the transducer power gain (TPG) sensitivity with respect to the component values is employed in such a way that the effects of the components tolerance on the matching network performance can easily be quantified. A 3D data structure based on the adjacency matrix is conveniently used to represent any type of network topologies. The proposed EA employs a novel set of topology variation operators, tailored for changing the circuit topology, and an association step, with the aim of reducing the number of nodes of the matching circuit. The efficiency of the proposed EA is tested in the synthesis of an impedance matching network for a VHF monopole whip antenna. This study’s results indicate a matching bandwidth improvement, a more uniformly distributed TPG along the operation frequency band and a more stable TPG regarding the components tolerance compared to the results obtained by previous approaches. 相似文献
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《Vehicular Technology, IEEE Transactions on》1975,24(2):21-29
Short whips (monopoles) are often used on vehicles when a quarter wavelength is too long. It is common knowledge that a loading coil located in series with the whip improves narrow band performance. This series inductive loading of monopole (dipole) antennas is analyzed by a piecewise sinusoidal moment method. When loaded to resonance, the current rises from the feed value to a peak slightly beyond the load point with decay to zero at the end. Radiation resistance improvement factors as large as 5 have been calculated. The resonant loading reactance is shown to vary inversely with the antenna length for most lengths. Efficiency varies slowly with load point and peaks at roughly 0.4 (of the whip length) from the feed in contrast to earlier approximate theory that predicted higher efficiency for loads farther out toward the end. The curves allow a tradeoff between slightly reduced efficiency and larger input resistance (to allow easier matching) to be made. For this case, a 2/3 loading point may be a good compromise. The length for which efficiency is 50 percent is a useful design guide. This length varies slowly with Q and h/a and is in the range 0.06 to 0.09λ. Thus shorter monopoles will have low efficiency. Extensive graphical data are presented. 相似文献
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新型宽波束圆极化天线--微带介质天线 总被引:2,自引:0,他引:2
通过在微带天线中引入介质天线原理,提出了一种以简单方式展宽微带天线波束和提高低仰角增益的新方法,从而发明了一种新型宽波束天线-微带介质天线。该天线具有极宽的波束、较高的低仰角增益和波束范围内有较好的圆极化性能等特点。文中给出了天线的原理、设计公式和实验结果。 相似文献
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等离子体天线因其具有许多独特的性质而受到广泛关注。利用金属天线的传输线等效理论,研究了等离子体电子密度和碰撞频率对等离子体鞭状天线辐射方向特性的影响,并利用高频仿真软件HFSS对计算方法进行了验证。结果表明,当等离子体电子密度较小、碰撞频率较高时,等离子体鞭状天线与相同物理尺寸的金属天线辐射方向图相差较大;而在较高电子密度和较低碰撞频率条件下,两种天线具有相似的辐射方向图,并且电子密度越大、碰撞频率越低,其与金属天线的辐射方向图越接近。 相似文献