共查询到19条相似文献,搜索用时 119 毫秒
1.
为了开展大口径天线短脉冲微波辐射特性研究,建立了一套大口径天线微波短脉冲特性测试系统。该系统可产生快上升沿、脉冲可调(脉宽最短可到0.5 ns)的微波激励脉冲、接收动态范围大于52 dB。利用该测试系统进行实验,获得了不同微波激励脉冲宽度条件下,天线方向图和辐射场波形脉冲宽度变化曲线。测试结果表明:在天线远场距离处,改变微波激励脉冲宽度,对天线主轴辐射场波形基本无影响;而在偏离主轴处,辐射场波形会出现不同程度的脉冲展宽及幅值减小等波形畸变现象,偏离主轴角度越大,微波激励脉冲宽度越小,畸变越明显。 相似文献
2.
为分析口径天线辐射场方向性,在计算等效面磁流的同时,引入等效面电流的作用,对辐射远场方向性进行了修正,解析公式更适合描述自由空间中口径天线的辐射场;在时间域对冲激脉冲口径辐射场方向性进行分析,得到以下结论:馈入脉冲宽度变宽、口径尺寸减小、口径场幅度锥削分布,以及球面波前均会降低辐射场方向性;辐射场存在时域波形延拓现象,即存在空间色散问题;球面波使口径辐射场方向性迅速恶化,在远区得到一个主轴附近峰值场强相对平坦,而在一定角度峰值场强迅速下降的场。 相似文献
3.
4.
5.
6.
在频域和时域研究了TEM喇叭天线的辐射机理。在频域,高频信号激励的TEM喇叭表现为口径天线的辐射特性,具有良好的方向性;低频信号激励的TEM喇叭可视作偶极子天线,具有全向辐射特性;在时域,脉冲激励的TEM喇叭天线辐射场由四个子波叠加构成,在不同方向上,各个子波的波形和相对时序不同,导致不同方向上辐射场波形也不相同。根据辐射机理研究结果,提出了一种TEM喇叭天线末端加载设计并给出了其优化设计方法,有效地改善了天线主轴辐射性能,提高了辐射因子和天线效率。 相似文献
7.
采用大口径是一种实现天线高增益十分有效的技术手段,由美国空军Pbilp实验室C.E.Baum博士提出的辐射高功率超宽带短脉冲的反射面冲击脉冲辐射天线(IRA)是一种新型的超宽带天线系统。根据本单位超宽带天线研究的经验和国外资料,通过优化设计,完成了φ4.5m的抛物面型冲击脉冲天线系统的制作。 相似文献
8.
9.
10.
11.
Transient radiated field from aperture antennas is derived by using the field equivalence principle. For Gaussian pulse excited uniform and tapered planar apertures, transient radiation parameters, such as radiation energy pattern, the half-energy beamwidth and directivity, are calculated. The simulation formulations for calculating the half-energy beamwidth and directivity are presented 相似文献
12.
The spectral characteristics of a time-dependent Gaussian pulse from a circular mask with a circular apertures array in the far field are theoretically investigated and presented with numerical results. A rigorous treatment, with the Fresnel diffraction integral, to the spectral changes of a time-dependent Gaussian-shaped pulse passing through a circular mask with a linear circular apertures array is given and some properties of the spectral intensity under different situations are provided. Also an accurate and concrete criteria judging the condition for the red shift, blue shift of spectral intensity distributions is obtained as well. 相似文献
13.
The diffraction spectral intensity characteristics of a time-dependent Gaussian pulse from an apodized circular aperture in the far field are studied both theoretically and numerically. It is shown that the apodization of the diffracted Gaussian pulse spectrum can be found. Also the red or blue shift of the spectral intensity maximum of the incident pulse is presented. 相似文献
14.
孔径光阑限制下高斯光束的传输 总被引:8,自引:3,他引:5
对高斯光束在硬边孔径限制下的衍射进行了详细的理论研究,就不同口径的圆孔限制下高斯光束在菲涅耳衍射区和夫琅禾费衍射区的分布进行了理论分析,从而得到了孔径受限高斯光束的横向以及轴向的衍射公式,进而对高斯光束在不同衍射区域内衍射光场分布形状随孔径尺寸变化时的演化规律进行了数值计算,并对小口径光阑受限的高斯光束的衍射与平行光经同尺寸光阑的衍射进行了比较。结果表明在较小口径下,两者的分布基本一致。得到的孔径光阑限制下高斯光束的传输规律为高斯光束在自由空间光通信和光学超分辨中的应用提供了理论基础。 相似文献
15.
Starting from the Rayleigh-Sommerfeld diffraction integral and without invoking the paraxial approximation, analytical expressions for the field distribution, far-field power spectrum and temporal far-field distribution of chirped Gaussian pulses diffracted at a circular aperture are derived, which enables us to study the spectral anomalous behavior of diffracted chirped Gaussian pulses in the far field. The potential applications of spectral anomalies of ultrashort pulses are discussed. It is found that at the critical angle the spectral switch appears. The frequency difference between the two equal heights of spectral switches increases and the corresponding critical diffraction angle slightly increases as the chirp parameter increases and pulse duration decreases. In a certain region of the truncation parameter, the critical angle decreases with increasing truncation parameter. By suitably varying the pulse duration, chirp parameter and truncation parameter, information encoding and transmission are achievable in the use of chirped Gaussian pulses. 相似文献
16.
The spectrum change of a Gaussian pulse in the far field is studied with the Fresnel diffraction integral when it is incident on an aperture with Gaussian form transmittance. It is found that the side-lobes of the diffracted spectral intensity, which exist in a normal circular aperture with unit transmittance, can be eliminated completely under such a condition. Also, the red shift and blue shift of the spectral intensity maximum of the incident pulse are presented. 相似文献
17.
Based on the expansion of the hard aperture function into a finite sum of complex Gaussian functions, using Collins formula, the approximate analytical expression of Gaussian beams through 2 × 2 square matrix circular apertures is derived. Finally, some numerical examples are given to illustrate the analytical results by Matlab. It is shown that the propagation characteristics is related with the propagation distance z, the radius of circular aperture a and the distance d. The results can be directly used in other beams and square matrix apertures, and be applied to control beams and optical system designing. 相似文献
18.
H.-E. Hwang 《Optical and Quantum Electronics》2003,35(15):1335-1350
The diffraction characteristics of a broad-band light source from a rectangular mask with a circular aperture array in the far field are theoretically investigated with a rapid and precise mathematical derivation. We provide a rigorous treatment of a time dependent Gaussian-shaped pulsed beam passing through a rectangular mask with a circular aperture array and give more accurate and concrete criteria judging the timing for the spectral red shift, blue shift, and splitting of light distributions as well. In addition, the distortion of the space-time diffraction intensity distribution is also presented in detail. This study shows the mathematically analytic form for a pulsed beam incident on an array of small apertures, when the usage of lenses is not practical. Also, the energy distribution of the pulse in the frequency domain is presented to benefit the understanding of its applications in optics information systems. 相似文献