共查询到20条相似文献,搜索用时 390 毫秒
1.
The truncated spherical helix is presented as a compact circularly polarised antenna with relatively high gain and moderate bandwidth. A numerical investigation into the radiation properties of this antenna is also presented. The antenna provides a directivity of >9 dB and an axial ratio of <3 dB over a 10% bandwidth. The radiation pattern has a broad main beam and better than 20 dB front-to-back ratio 相似文献
2.
The radiation properties of several electrically small, folded spherical helix antennas are presented. The primary variables considered in the design of these antennas are the number of helical turns and the number of helical arms. The principle design objectives are to achieve self resonance, a low quality factor (Q), and a practical radiation resistance for small values of ka. Designs are presented for ka less than 0.5, where the antennas are self resonant, exhibiting an efficiency in excess of 95%, a Q within 1.5 times the fundamental limit, and a radiation resistance near 50 /spl Omega/. The relationship between the number of helical turns, the number of helical arms, and achieving self resonance at low frequencies is discussed. 相似文献
3.
研究了一种用于中短距离通信的螺旋天线,分析了螺旋天线特别是轴向模螺旋天线的基本电磁辐射特性,介绍了有限元方法的基本理论和数值计算过程,并结合有限元法对螺旋天线进行了设计、优化,仿真出该天线的电参数和辐射方向图,然后将设计的天线模型进行通信实验。实验表明圆极化的轴向模螺旋天线通信质量良好,完全达到设计要求。 相似文献
4.
《Microwave Theory and Techniques》1969,17(2):66-73
The propagation characteristics of leaky waves in a helix waveguide covered with a slitted cylinder are presented by a method of transverse network representation. The main interest is in helix waveguides with small pitch angles, characterized by a hybrid mode consisting of TE/sub 01/, and a small amount of TM/sub 01/ modes. The leaky wave discussed in this paper may then be regarded as a perturbation of the TM/sub 01/ wave by the slitted cylinder outside the helix. The radiation, metal, and dielectric losses are calculated numerically at a frequency of 50 GHz. The relation between the radiation loss and aperture angle of slit is very different from that of an ordinary leaky waveguide composed of a slitted cylinder without helix, especially when the distance between the helix and shield cylinder is about a quarter of the radial wavelength. The metal and dielectric losses are the same order as radiation loss, however the dielectric loss decreases as the power factor /spl epsiv/"/ /spl epsiv/' increases. The measured total attenuation constant averages about 5 dB/km, almost twice the theoretical value. 相似文献
5.
An antenna system consisting of a driven balanced helix and two parasitic helices is compared with a continuously wound balanced helix with the same total turns. The similarity in the radiation pattern, axial ratio and directive gain are found by theoretical investigation. 相似文献
6.
7.
8.
A small helix and a ground plane are located in the same plane. The antenna characteristics are revealed for the case where a conducting rectangular parallelepiped is inserted into the helix. It is found that the parallelepiped contributes to lowering the frequencies at which the VSWR exhibits a local minimum. The current distribution and radiation pattern are also presented 相似文献
9.
Axial mode helical antennas 总被引:2,自引:0,他引:2
Nakano H. Samada Y. Yamauchi J. 《Antennas and Propagation, IEEE Transactions on》1986,34(9):1143-1148
The radiation characteristics of helical antennas operating in the axial mode are evaluated on the basis of the theoretical current distributions and are verified by experimental work. A comparison between monofilar helix and bifilar helix antennas is made, and a helical antenna with a parasitic helix (HAP) is proposed in order to enhance the power gain. It is found that the gain of the HAP in which the parasitic helix is wound from a point diametrically opposite to that of one and one-half turns of the driven helix is about 1 dB higher than that of the monofilar helix. The ratio of the frequency band in which the HAP radiates a circularly polarized wave within an axial ratio of 3 dB is calculated to be 1:1.8. 相似文献
10.
本文提出一种用双线背射螺旋作馈源的新式背射天线。这种天线具有结构简单,馈电方便,增益较高,易于产生圆极化波等优点。 相似文献
11.
I. V. Semchenko S. A. Khakhomov A. L. Samofalov 《Journal of Communications Technology and Electronics》2007,52(8):850-855
Transformation of the polarization of an electromagnetic wave by a 2D array of double-turn metal helices is investigated both theoretically and experimentally. Electric and magnetic moments induced in an isolated helix by an incident linearly polarized wave are determined. A universal relationship between the projections of the induced moments onto the axis of a helix is derived. The helix parameters that are optimal for radiation of a circularly polarized wave are calculated. A 2D array composed of double-turn helical radiators with optimum parameters is manufactured. Experimental verification of the obtained theoretical results is performed. 相似文献
12.
Nakano H. Yamauchi J. Mimaki H. 《Antennas and Propagation, IEEE Transactions on》1988,36(10):1359-1364
Numerical analysis of a helical antenna is made in the presence of a finite-grid ground plane. It is found that the transition from forward-fire radiation to backfire radiation occurs as the ground-plane diameter is reduced to the order of the helix diameter. The investigation of the backfire helix with a small ground plane shows that a circularly polarized wave is radiated over a frequency range of more than 1 to 1.3. An application of the backfire helix to primary feed for a paraboloidal reflector is also described, in which the far-field pattern is evaluated by the physical-optics approximation 相似文献
13.
根据里查德沃耳夫矢量积分理论,研究了在径向偏振光经大数值孔径聚焦下,透镜球差对瑞利粒子轴向光阱力的影响。通过数值计算得到了轴向光阱力随球差系数变化的分布。研究结果表明,球差系数的存在,不仅改变了光阱力的数值大小,也影响了对粒子束缚的有效作用区域,还导致光阱中心位置发生偏移。而且正负球差系数对光阱力的影响并不总是对称的,正球差系数使得梯度力的0点位置往z轴正向偏移,负球差系数使得梯度力的0点位置往z轴负向偏移。在不同的数值孔径、粒子半径以及孔径与光腰的比值下,球差对光阱力的影响程度也不同。 相似文献
14.
一种L波段背射模螺旋馈源 总被引:1,自引:1,他引:0
螺旋天线具有较好的宽频带圆极化特性,在L或S波段体积和增益都很适中,加工制造公差要求较低,因此在该频段螺旋天线得到了广泛的应用。由背射模螺旋构成的L波段宽带馈源具有结构简单,馈电、调试方便,口面遮挡小,频带宽(大于25%),可以承受大功率等优点,可以满足L或S波段测控系统对天线的要求。用该背射模螺旋馈源研制的前馈天线的口径效率超过了53%,第一副瓣小于-20 dB,在工程中得到了很好的应用。 相似文献
15.
Use is made of the Fourier integral to derive an expression for the radiation field of spherical reflectors which are corrected for spherical aberration with the use of a subreflector. Calculations for some cases of interest show the sidelobe radiation to be 5.6 dB higher than in a uniformly illuminated aperture. 相似文献
16.
轴向模螺旋天线的仿真研究 总被引:1,自引:0,他引:1
对轴向模螺旋天线的特性进行了理论分析,利用电磁仿真软件Ansoft HFSS12在1.615GHz对螺旋天线的特性进行了仿真,并通过改变导线接地板平面直径的尺寸,得到天线良好的背射方向图。 相似文献
17.
It is shown how the concept of phase mode excitation of circular antenna arrays may be extended to spherical arrays, and in particular that a spherical phase mode of the excitation function of a spherical array results in a far field radiation pattern with the same spherical phase mode form. A number of applications and issues concerned with the practical implementation are discussed. 相似文献
18.
根据无线局域网通信天线的要求,设计了三种工作在5GHz频段性能良好的轴向模螺旋天线,其中一种为普通螺旋天线,第二种为加绕寄生螺旋天线,第三种为锥形加绕寄生螺旋天线。通过电磁仿真软件HFSS计算及对结果分析表明,加绕寄生螺旋将改善天线的轴向辐射特性,而锥形结构将扩展天线带宽。 相似文献
19.
20.
N. Guo W. D. Hu X. S. Chen W. Lei Y. Q. Lv X. L. Zhang J. J. Si W. Lu 《Journal of Electronic Materials》2013,42(11):3181-3185
Three designs of micro-optic structures have been analyzed by two-dimensional simulation. Compared with traditional spherical microlenses, the micro-optic structures have the same ability to collect radiation and do not have the disadvantages of traditional microlenses. In our analysis the micro-optic structures are simple grooved notches above the space between two adjacent mesas. We also investigate the characteristics of InSb focal-plane arrays with both spherical microlenses and micro-optic structures under oblique incident radiation. Empirical formulas were derived to describe the response and crosstalk as a function of incident radiation angle. Our results show that the micro-optic structures can be effectively used in radiation collection for InSb infrared focal-plane arrays. 相似文献