数字声光频谱仪性能改进

本文介绍了数字声光频谱仪通过鉴定之后所进行的一系列改进。对电系统和声光系统频率响应进行了综合补偿,改善了整机频率响应。提高了时间分辨率。软件改进增加了频谱仪数据采集功能,并使它操作更加简便。     

数字声光频谱仪时间分辨率的测定

本文报告了对新近研制的太阳米波数字声光频谱仪数据采集系统时间分辨率的测定,并讨论了该仪器以不同方式工作时可能达到的最高时间分辨率。     

用于射电天文数字频谱仪的新进展

根据在射电天文频谱观测中出现的新需求,介绍了近年来数字技术的新进展.达到GHz采样速率的多位高速模数转换器(Analog-to-Digital Converter,ADC)、海量数字处理芯片现场可编程门阵列(Field Progxammable Gate Array,FPGA)以及运行在这些芯片上的并行快速傅里叶变换知识产权(Fast Fourier,Transform Intellectual Property,FFT IP)内核,结合高性能数据总线的系统集成,为射电天文构建新型FFT频谱仪提供了可能的技术选择.与现有其他类型频谱仪相比,集成了这些新技术的数字型FFT频谱仪有更大的带宽、更高的谱分辨率、更高的动态范围和整体稳定性,此类频谱仪的出现显示了射电频谱技术已经进入了新一代数字技术应用的阶段.     

超宽带超高分辨率太阳射电频谱仪的研发

为完成对太阳射电爆发15 MHz～15 GHz频谱的监测,云南天文台研发4套太阳射电频谱仪,频率覆盖范围依次为15～80 MHz, 100～750 MHz, 600～4 200 MHz和4～15 GHz,分别称为十米波、米波、分米波和厘米波太阳射电频谱仪。十米波段太阳射电频谱仪的谱分辨率和时间分辨率分别为7.6 kHz和1 ms;米波段和分米波段太阳射电频谱仪的谱分辨率和时间分辨率分别为9.5 kHz和10 ms;厘米波段太阳射电频谱仪的谱分辨率和时间分辨率分别为76 kHz和10 ms。每套设备包括天线系统、接收机和数字频谱仪。为实现超高谱分辨率,需要的快速傅里叶变换(Fast Fourier Transform, FFT)点数最高达到262 144,在现场可编程门阵列(Field Programmable Gate Array, FPGA)上,通过一个FFT IP核(Intellectual Property Core)不能实现如此高点数的快速傅里叶变换运算。对于大点数的快速傅里叶变换,需要对数据行列分解后做并行处理,从而将其转化为两个小点数的快速傅里叶变换。通过对并行算法的研究,...     

米波太阳射电频谱仪的科学目标和技术方案

介绍了70～700MHz低频太阳射电频谱仪的科学目标和技术方案,给出了11m 网状抛物面天线、接收系统、数字频谱终端的技术指标.并对系统的整机噪声系数、灵敏度、最小可测流量密度、LNA输入端的噪声功率进行了估计.系统频谱分辨率优于0.2MHz,时间分辨率最高可达2 ms.     

太阳射电频谱仪数据采集与处理(自相关频谱仪原理与应用)

本文论述了 0 .7～ 1 .4GHz太阳射电频谱仪数据采集与处理系统是如何实现的。正在研制的此仪器采用了多通道频谱仪与自相关频谱仪结合使用的方案。首先 ,本文详细讨论了自相关频谱仪的原理 ,并介绍了北京大学研制的自相关频谱仪的结构。在此基础上着重讨论了多通道频谱仪与自相关频谱仪的同步控制的解决方案 ,以及大容量数据采集实时存盘的解决方案。最后 ,介绍了我们为数据预处理采用的一些方案。     

太阳射电频谱仪数据采集与自理自相关频谱仪原理与应用）

本文论述了０．７～１．４ＧＨz太阳射电频谱仪数据采集与处理系统是如何实现的。正在 研制的此仪器采用了多通道频谱仪与自相关频谱仪结合使用的方案。首先,本文详细讨论了自相关频谱仪的原理,并介绍了北京大学研制的自相关频谱仪的结构。在此基础上着重讨论了多通道频谱仪与自相关频谱仪的同步控制的解放方案,以及大容量数据采集实时存盘的解决方案。最后,介绍了我们为数据预处理采用的一些方案。     

基于多相滤波器的宽带射电频谱仪设计

提出了一种基于多相滤波器的新型宽带射电频谱仪的设计方案。通过多相滤波器实现宽带射电信号的滤波,对滤波后的基带信号进行数字功率检波,再通过积分控制,最终得到射电信号的频谱强度。仿真分析表明,这一设计具有很好的效果,通过多相滤波器,使信号的速率大为降低,克服了传统频谱仪以及采用FFT实现频谱变换方法的缺点,可以实现对超宽带射电信号的实时频谱分析。     

德令哈13.7m望远镜多波束接收机的运行

德令哈13.7 m望远镜是中国最重要的射电望远镜之一.望远镜自安装超导成像频谱仪以及采用飞行观测模式以来,运行近10 yr.在此期间,望远镜开展并完成大量的天文观测,累积了巨量的天文数据,取得了一系列重要的科研成果.介绍了超导成像频谱仪在天文观测中的运行状态,运行中疑难问题、故障现象及解决方案.详述了超导成像频谱仪各方面性能测试及多年来的性能分析,包含接收机噪声温度及望远镜系统噪声温度、镜像抑制比、接收机稳定性、波束性能等方面.列举了超导成像频谱仪更新发展方面的工作,包含本振功率自动化调整、边带分离型超导混频器预放大电路的更新、控制程序的优化等.总结经验和规律,承前启后,将过去的超导成像频谱仪的维护运行经验应用到之后新一代大规模接收机系统中.     

基于Roach Ⅱ的数字频谱仪开发设计

为实现宽频带电磁环境实时测量,基于Roach II开发平台,开发设计了数字频谱仪,实时带宽10 MHz～2 GHz,动态范围达到55 dB。首先,分析了数字频谱仪开发设计理念和模块参数设置,实现快速扫描模式、脉冲监测模式的测试功能。其次,通过频率响应、动态范围、线性度等关键指标测量及分析,并与商用频谱仪测量结果对比,确定该数字频谱仪具有相对准确的测试精度,可应用于射电望远镜台站宽带实时频谱监测及瞬态信号分析。     

The High Resolution Chirp Transform Spectrometer for the Sofia-Great Instrument

In this paper, we present the design of a high resolution Chirp Transform Spectrometer (CTS) which is part of the GREAT (German REceiver for Astronomy at Terahertz frequencies) instrument onboard SOFIA, the Stratospheric Observatory For Infrared Astronomy. The new spectrometer will provide unique spectral resolving power and linearity response, since the analog Fourier transform performed by the CTS spectrometer was improved through a new design, that we call “Adaptive Digital Chirp Processor (ADCP)”. The principle behind the ADCP consists on digitally generating the dispersive signal which adapts to the compressor dispersive properties, achieving maximum spectral resolution and higher dynamic range. Excellent test results have been obtained such as a white noise dynamic range of 30 dB, and a spectral resolution (FWHM) of 41.68 kHz which would mean if analyzing signals with the high frequency band receiver on the GREAT instrument (4.7 THz) a spectral resolving power (λ/Δ λ) higher than 10⁸.     

Infrared imaging and spectroscopy with arrays at the University of Montreal

The Montreal Infrared Camera (MONICA) consists of a LN₂ cryostat enclosing a NICMOS3 array, re-imaging optics and a filter wheel mechanism containing broad-band and circular variable filters. A polarimetry mode with a warm half wave plate and a cold polarizer/filter combination is also supported. At the CFHT 0.5 (FWHM) images are routinely obtained with limiting magnitudes of 22.8 at J and 21.7 at K (S/N=3 in 1hr).The Spectrometre Infrarouge de Montréal (SIMON) is a versatile grating spectrometer with spectral resolutions ranging from 300 to 5000. Presently under construction, this spectrometer will initially contain a 512×512 HgCdTe array. Use of reflective optics will allow a future upgrade to a similar format InSb array, extending the wavelength coverage to 5m. SIMON will also have an imaging mode to facilitate the centering of objects within interchangeable slits.     

The calibration of the Cassini-Huygens CAPS Electron Spectrometer

We present the two-stage method used to calibrate the electron spectrometer (ELS), part of the plasma spectrometer (CAPS) on board the Cassini spacecraft currently in orbit around Saturn. The CAPS-ELS is a top-hat electrostatic analyser designed to measure electron fluxes between 0.5 eV and 26 keV. The on-ground calibration method described here includes the production of photoelectrons, which are energised and passed into the CAPS-ELS in a purpose designed calibration facility. Knowledge of the intensity of these incident electrons and the subsequent instrument output provides an on-ground calibrated geometric factor. Comparative studies of physical quantities such as plasma density and electron differential flux calculated using on-ground calibration factor with the quantities deduced from the wave experiment and high energy electron detector provide in-flight calibration. The results of this are presented together with a comparison of the experimentally calibrated values with simulated calibration values.     

Balloon-Borne Hard X-Ray Spectrometer Using CdTe Detectors

Spectroscopic observation of solar flares in the hard X-ray energy range, particularly the 20 ∼ 100 keV region, is an invaluable tool for investigating the flare mechanism. This paper describes the design and performance of a balloon-borne hard X-ray spectrometer using CdTe detectors developed for solar flare observation. The instrument is a small balloon payload (gondola weight 70 kg) with sixteen 10×10×0.5 mm CdTe detectors, designed for a 1-day flight at 41 km altitude. It observes in an energy range of 20−120 keV and has an energy resolution of 3 keV at 60 keV. The second flight on 24 May 2002 succeeded in observing a class M1.1 flare.     

3D: The new MPE near-infrared field imaging spectrometer

3D, the next-generation near-IR spectrometer developed at the MPE, produces in a single integration, a datacube of a 8×8 field characterised by 0.5 resolution in image space and a resolving power of R=1000 over the entire K-band in wavelength space.A detailed account of this work, including results of the first test measurements, will be presented elsewhere (Weitzel et al., in preparation).     

基于ARM＋FPGA的IRIG-B码产生器的研制

本设计中采用ARM芯片作为主控芯片,FPGA芯片作为主功能芯片,使用C和Verilog语言编程。通过软件控制生成IRIG-B（DC）码信号,由分频1PPS信号和外部标准1PPS信号锁相同步保证时标信号的同步,在产生DC码后采用基于FPGA内部ROM数字查找表技术实现AC码的数字调制。整体方案设计简单,应用方便。     

Analysis of disturbances in the Planetary Fourier Spectrometer through numerical modeling

Fourier transform spectrometers are instruments with high sensitivity to many kinds of disturbances. This study started from the analysis of the disturbances related to mechanical vibrations on the PFS FTIR spectrometer to show how the measured spectra can differ from the actual ones. The complete study, more in general, accounts for the characteristics of a real instrument and its operating environment to show, which can be the effects of many sources of disturbances on realistic measurements. The analysis is especially relevant when the spectra are used for the determination of parameters through “best fitting techniques” by matching with synthetic ones because it shows how spectral features used in these studies can be modified by disturbances. A previous work addressed the theoretical treatment of vibrations borne effects on FTIR spectrometers and is the ground work for the present; however, that study, being based on an analytical approach could only show examples of single effects on simplified input signals such as emission lines. This study conversely is based on a numerical model, developed in order to include altogether the effects addressed in the theoretical work to show combined effects on complex spectra like those expected from Mars. This allows not only to evaluate the linked effects of many kinds of disturbances but also to account for the real spectrometer characteristics. The use of synthetic spectra as input allows the comparison between expected spectra and measured ones. The simulation is tailored on the Planetary Fourier Spectrometer (PFS), onboard the ESA Mars Express spacecraft, from 2003 orbiting around Mars and in particular on its short wavelength (SW) channel, where many disturbances are more evident.     

A flexible hybrid spectrometer for balloon borne and ground based (sub)millimeter wavelength astronomy

This paper describes a flexible spectrometer architecture consisting of standard units that can be configured to meet different requirements. The spectrometer is a hybrid between an analog filterbank and digital autocorrelator. Two applications are given, one for balloon borne submillimeter radio astronomy employing a compact and low power design, and one for millimeter imaging with a much more powerful and flexible system. The basic hardware and software units are described as well as the overall architecture. Thanks to the modularized approach the spectrometer can easily be modified for other application areas, such as plasma physics or molecular spectroscopy.