The RATAN-600 radio telescope as a two-mirror aplantatic system

We present the results of calculations for the characteristics of a RATAN-600 radio telescope in the radio-Schmidt telescope mode. The plane reflector and the principal antenna mirror were calculated as a two-mirror aplanatic system with a planoidal mirror for Schmidt correction of the wave front of the wave incident at an arbitrary angle to the horizon. Formulas were derived and codes were developed to calculate the configuration of the antenna-system mirrors and optimize the basic parameters of the system. It is shown that a long-term (up to one-hour) tracking of cosmic sources is possible in this operation mode at wavelengths greater than 2 and 4 cm for horizontal apertures of 100 and 150 m, respectively. Special Astrophysical Observatory of the Russian Academy of Sciences, Nizhny Arkhyz, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 3, pp. 185–196, March, 2000     

ALMA Band 10 tertiary optics

The ALMA Band 10 (787–950 GHz) receiver is a dual-polarization heterodyne system based on NbTiN superconducting technology. The coupling of energy from the secondary mirror of the ALMA Cassegrain antenna to the Superconductor–Insulator–Superconductor (SIS) mixers used for down-conversion is achieved by a frequency-independent optical system composed of two elliptical mirrors to focus and redirect the incoming radiation, a wire-grid to separate orthogonal linear polarizations and two corrugated horns, one for each polarization and SIS mixer. In this paper, we present the ALMA Band 10 tertiary optics design and evaluate its performance by quasi-optical techniques, Physical Optics simulations and measurements. Detailed results of secondary aperture efficiency and beam-squint are provided. The characterization procedure described in this paper can be used for any optical system at around 1 THz.     

Validation of Design Techniques on a Quasi-Optics Test Bench

A two channel Quasi-Optics Network (QON) with a Frequency Selective Surface (FSS) to act as filter has been designed, constructed and tested in order to examine several aspects of the design, including the accuracy of the design software, the effectiveness of the FSS and the effect of moving components along the ray path in a QON. The QON was designed to feed an offset reflector system which required an input beamwidth of 20 degrees at −8.68 dB. The two channels were the atmospheric sounding channels at 54 GHz (5 GHz bandwidth) and 89 GHz (3 GHz bandwidth). Gaussian beam techniques were used to design the QON with the final optimisation carried out using Physical Optics and Physical Theory of Diffraction. The measurements were carried using the facilities at National Physical Laboratory, London and Queen Mary, University of London. Agreement between predicted and measured performance was good, thus validating the design method, the equipment manufacture and the assumptions.     

Plasmonic Photoconductive Antennas for Terahertz Pulsed Spectroscopy and Imaging Systems

Optics and Spectroscopy - We propose a terahertz (THz) plasmonic photoconductive antenna (PCA) with a record height of its metal electrodes of h = 100 nm and a high aspect ratio of h/p = 0.5 (p is...     

Experimental validation of Fourier-transform wave-front reconstruction at the Palomar Observatory

Wave-front reconstruction with use of the Fourier transform has been validated through theory and simulation. This method provides a dramatic reduction in computational costs for large adaptive (AO) systems. Because such a reconstructor can be expressed as a matrix, it can be used as an alternative in a matrix-based AO control system. This was done with the Palomar Observatory AO system on the 200-in. Hale telescope. Results of these tests indicate that Fourier-transform wave-front reconstruction works in a real system. For both bright and dim stars, a Hudgin-geometry Fourier-transform method produced performance comparable to that of the Palomar Adaptive Optics least squares. The Fried-geometry method had a noticeable Strehl ratio performance degradation of 0.043 in the K band (165-nm rms wave-front error added in quadrature) on a dim star.     

Analysis of the multiple inversion of the circular polarization of sunspot-associated microwave sources

Solar observations with a new panoramic spectrum analyzer (PSA) of RATAN-600 showed the multiple inversion of the sense of circular polarization in microwave local sources (LSs). The polarization spectra of LSs are analyzed in terms of the theory of linear coupling of ordinary and extraordinary modes in the quasitransverse (QT) region. We consider the RATAN-600 radio observations of June 2, 1977, January 10, 1992, and May 9 and 10, 1992 for the LS, which demonstrated the inversion of polarization sense in the range 2.0–6.5 cm. The theory of QT propagation imposes a constraint on the degree of polarization of microwaves at wavelengths close to the inversion wavelength. The dependence of the multiple inversion on the wavelength due to multiple crossing of QT regions is verified. The LS polarization spectra are correlated with the spectra calculated for a varied multiplicity to determine more accurately the multiplicity of the inversion. We propose that the multiple inversion is due to the fine structure of the coronal magnetic field. The analysis of this phenomenon allows the coronal magnetic field in the active region to be determined simultaneously at several heights. Ventspils International Radioastronomy Center, Riga, Latvia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 3, pp. 259–269, March, 1998.     

基于FDTD的时域混合方法及其在天线前门耦合数值模拟中的应用

强电磁脉冲环境下的平台-机载天线一体化耦合计算属于典型多尺度时域电磁计算问题,采用传统的FDTD方法数值模拟时,由于精细结构的存在导致网格量巨大,计算效率低下。介绍了一种将非均匀FDTD方法与细导线FDTD方法以及多网格集总元件FDTD方法相结合的时域混合方法,能够有效降低计算开销,结合并行计算技术,快速计算得到天线端口上耦合产生的瞬态电压和电流响应,并将该方法成功应用于无人机平台-天线一体化前门耦合数值模拟中。     

On Photostability of Acrylate and Polymethylmetacrylate Planar-Fiber Structures with Coumarin 7, 47, and 120, POPOP,and NOL8 Luminophores for UV Information Systems

Optics and Spectroscopy - We studied the photostability of planar-fiber structures in the form of films with a thickness of 600–800 µm under long-term ultraviolet irradiation. The films...     

基于双波前传感器自适应光学技术的太阳光栅光谱仪

为了研究不同太阳大气高度的热力学特性,具有良好成像质量的成像型光栅光谱仪是实现这个目标的重要仪器。然而作为地基式太阳望远镜重要的终端仪器之一,光栅光谱仪的光谱成像性能不可避免的会受到动态波前像差和系统静态像差的影响。动态波前像差常通过在太阳望远镜系统中集成自适应光学系统进行补偿。针对光学系统中的由装调和光学元件加工等引起的静态波前像差,提出了一种基于自适应光学技术校正光栅光谱仪中静态波前像差的方法,并进行了数值模拟仿真和实验验证。实验结果表明,校正后系统的残余波前像差RMS≈0.025λ,此时波前像差对光谱分辨率和能量利用率的影响可忽略,提高了光栅光谱仪的光谱成像质量,证明了所提出的方法的有效性。此外它具有降低光学系统装调精度和光学元件加工精度要求的优点。     

基于等离子体的定向天线阵理论与实验研究

当前国内学者对等离子体天线的研究主要集中于柱状天线和反射面天线, 而在国外已有学者以等离子体阵列结构设计了功能多样的智能天线系统. 为了较系统地了解这一新的设计思路, 基于等离子体散射理论对中心单元激励的圆形定向天线阵进行了理论和实验研究. 设计了一个16元等离子体无源振子的圆形天线阵, 实现了天线电磁波单波束和多波束的定向辐射. 通过理论计算和分析, 阐述了天线电磁波单波束和多波束辐射的原理. 通过建立实验系统, 测试了圆形天线阵的定向辐射特性. 实验结果和理论值接近, 说明该等离子体圆形天线阵可以实现天线电磁波的定向辐射和多波束辐射. 另外, 该天线阵还具有快速切换辐射方向、参数快速重构、雷达隐身性良好的优点. 关键词： 等离子体 定向天线阵 单波束 多波束     

A New Dielectric Grating Antenna with Large Leakage Constant for Millimeter-Wave Applications

The leakage properties of a new dielectric grating leaky wave antenna are carefully examined by an approach of combining the multimode network theory with the mode-matching method. A systematic comparison is given for the leaky characteristics of the n = −1 space harmonic of TM mode polarization between the present antenna and the traditional one. It has been found that the former is not only of lower conductor loss, but also of larger leakage constant than the latter. As a result, the dimension of the antenna could be largely reduced, which is of practical significance for some applications. Extensive numerical results of the radiation characteristics are given to establish useful guidelines for the design of the new grating antenna. Furthermore, special features such as cancellation or resonance effects are high-lighted and discussed. Physical insights for the mathematical findings are also presented.     

Multi-Azimuth Regime of Observations at the RATAN-600 Southern Sector with Periscope Reflector

This paper is devoted to the development of capabilities of the RATAN-600 radio telescope by putting the regime of multi-azimuth observations at the southern sector with periscope reflector into regular operation. This method makes it possible to study the dynamics of variable radio sources on temporal scales down to a few minutes and increase by one order of magnitude the number of variable sources observed during sky surveys. To date, over ten series of observations of the Sun were performed in the new regime using the multi-wavelength receiver complex, and new astrophysical results were obtained. The software for multi-wavelength mapping of the Sun and wavelet analysis of time series is developed. The following characteristics of the regime are achieved: a temporal resolution of 4 min during a time interval of up to 4.5 h for observations at azimuth angles in the interval from 30° to -30°.     

PO-TDIE混合方法在天线电磁兼容问题中的应用

应用物理光学-时域积分方程(PO-TDIE)混合方法对电大尺寸平台天线电磁兼容问题进行分析.详细推导PO-TDIE混合方法的一般表达式,并给出计算复杂度.数值算例表明,方法提高了传统时间递推方法(MOT)的计算效率,能够有效应用于电磁兼容分析中.     

Microstrip patch array antenna on photonic crystal substrate at terahertz frequency

Recent advancement in the fabrication and packaging technology has led to the micrometer and nanometer-scale device modeling. This technological development and subsequent reduction in the dimension of devices like modulators, detectors and antennas has brought a thought of increasing the operating frequency of the system to the extent of sub-millimeter wavelength. In the view of the technical breakthrough in the area of fabrication and packaging, we have explored a printed antenna array on the photonic crystal in the terahertz spectrum in this paper. An equivalent circuit model of the antenna has been proposed and a methodology to investigate various electrical parameters is discussed. Tunable parameters of the structure have been explored to optimize the electrical performance of the proposed antenna. The analysis is also compared by using two simulators: (a) CST Microwave Studio based on finite integral technique and (b) Ansoft HFSS based on finite element method. The effect of the photonic crystal as substrate to enhance the gain of this kind of the antenna has also been demonstrated. The gain, directivity, front-to-back ratio (F/B ratio), and the radiation efficiency of the proposed antenna at 600 GHz is 16.88 dBi, 17.19 dBi, 14.77 dB and 89.72%, respectively. Finally, the performance of the antenna has been compared with the reported literature.     

Investigation of laser energy conversion into plasma x-rays in the system Iskra-4

We present results of experimental and computational investigation of laser plasma emission in the soft x-ray spectrum. Plasma has been produced by irradiating a gold target with subnanosecond pulses at the first and second harmonics of an iodine laser. It has been shown that approximately half of the absorbed laser energy is converted into soft plasma x-rays.Presented at bilateral international seminar of High Temperature Laser Plasma and High Gain Iodine Lasers held on 4 July 1991 in the Inst. of Physics, Czechosl. Acad. Sci., in Prague (organized by Division of Optics of the Inst. of Physics, Czechosl. Acad. Sci., and Physical Section — Plasma Division of the Union of Czech Mathematicians and Physicists).     

Correlation radioheliograph based on the RATAN-600 radio telescope

We present methods for the practical use of variable-aperture antennas to form 2D images by correlation techniques for out-of-phase irradiation using the RATAN-600 radio telescope as an example.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 5, pp. 527–537, May, 1996.This work was partially supported by the International Science Foundation (No. NVH000) and by a joint grant of the Russian Government and the International Science Foundation (No NVH300).     

Image correlation techniques for variable-aperture radio telescopes

A new possibility of two-dimensional image creation for variable-aperture antennas is considered. An image correlation technique is proposed to recover two-dimensional images in a single passage of the source through the two-dimensional radiation pattern of the RATAN-600 radio telescope in the incoherent irradiation mode. High sensitivity of instantaneous mapping can be reached in spectrographic observations by both integration in the frequency band and long-term object tracking. Special Astrophysical Observatory of the Russian Academy of Sciences, Karachaevo-Cherkessiya, Nizhny Arkhyz, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 7, pp. 801–816, July, 1997.     

天线振子作为初值问题求解

根据计算实践和物理考虑,指出电磁场基本方程作为一阶双曲型偏微分方程组的初值问题,可以成为有效的天线振子数值计算方法。对于隐式差分格式,建议了一种交替方向追赶和外边界插值相结合的办法。讨论了圆柱对称振子的数值结果。     

Real Time Object-Locating Method Using Convolution Image

A simple method using a convolution image to locate an object in a scene is described. The image is processed by an optical system using a spatial light modulator in real time. Experimental results are presented with discussion on the improvement in the system performance.Presented at the International Commission for Optics Topical Meeting, Kyoto, 1994.     

基于坐标变换的动态光学成像性质研究

利用齐次线性坐标变换，将光学系统的高斯物像共轭理论用齐次坐标变换的方法来描述，并与动态光学理论中的作用矩阵相比较，阐述坐标变换方法与动态光学理论的关系。利用坐标变换方法推导一些重要的动态光学系统的成像性质，验证动态光学的一系列结论。通过本文的研究，证明坐标变换方法与动态光学理论的一致性，也明确在动态光学系统内坐标变换方法的应用。