High-Resolution Broadband Millimeter-Wave Astrophysical Spectrometer with Triple Product Acousto-Optical Processor

An advanced conceptual design of a high-bit-rate triple product acousto-optical processor is presented that can be applied in a number of astrophysical problems. We briefly describe the Large Millimeter Telescope as one of the potential observational infrastructures where the acousto-optical spectrometer can be successfully used. A summary on the study of molecular gas in relatively old (age > 10 Myr) disks around main sequence stars is provided. We have identified this as one of the science cases in which the proposed processor can have a big impact. Then we put forward triple product acousto-optical processor is able to realize algorithm of the space-and-time integrating, which is desirable for a wideband spectrum analysis of radio-wave signals with an improved resolution providing the resolution power of about 105 - 106. It includes 1D-acousto-optic cells as the input devices for a 2D-optical data processing. The importance of this algorithm is based on exploiting the chirp Z-transform technique providing a 2D-Fourier transform of the input signals. The system produces the folded spectrum, accumulating advantages of both space and time integrating. Its frequency bandwidth is practically equal to the bandwidth of transducers inherent in acousto-optical cells. Then, similar processor is able to provide really high frequency resolution, which is practically equal to the reciprocal of the CCD-matrix photo-detector integration time. Here, the current state of developing the triple product acousto-optical processor in frames of the astrophysical instrumentation is shortly discussed.

Transmission Performance of the Optical Millimeter-wave Up-conversion Link Using a Phase Modulator

Numerically analyzed is the transmission performance of the optical millimeter （mm）-wave generated by frequency up-conversion via a phase modulator along the dispersive fiber. 60 GHz ram-wave subcarrier（SC） signals can be obtained after fiber transmission, simultaneously, the phase-modulated signals can be converted to the intensity-modulated ones. The numerical results show that the optical ram-wave at fading loops has better performance, and the eye diagram still keeps open when optical mm-wave signal is transmitted over 98 km.

Generation of millimeter-wave sub-carrier optical pulse by using a Fabry-Perot interferometer

A novel scheme is proposed to transform a Gaussian optical pulse to a millimeter-wave （mm-wave） frequency modulation pulse by using a Fabry-Perot interferometer （FPI） for radio-over-fiber （ROF） system. It is shown that modulation frequency of mm-wave is determined by the optical path of the Fabry-Perot （F-P） cavity, and amplitude decay time and energy transfer efficiency axe related to the reflectivity of the F-P cavity mirror. The effect of pulse train extension on inter-symbol interference is also discussed.

Effective generation of optical quadruple frequency millimeter-wave based on fiber laser using injection rational harmonic mode-locked technique

A method to generate the optical quadruple frequency millimeter-wave with high power efficiency is pro- posed and demonstrated based on the combination of the injection 2nd-order rational harmonic mode- locked fiber ring laser technique and the fiber grating notch filter. In this approach, the fiber Bragg grating notch filter is inserted into the laser cavity to prevent the undesired optical carrier, so that the pump power can be converted to 2nd-order harmonic wave more efficiently. In our experiment, the power efficiency of optical quadruple frequency millimeter-wave （40 GHz） generation is ten folds of that of our previous method based only on the rational harmonic mode-locked technique.

基于相位调制器产生六倍频光毫米波的OFDM信号光传输系统研究

提出了两个并行相位调制器产生六倍频光毫米波并传输正交频分复用信号的全双工光纤无线通信系统.将2.5Gbt/s的正交频分复用信号调制到60GHz光毫米波上.从理论上分析了毫米波产生的原理,并分别模拟了毫米波信号承载OOK信号和正交频分复用信号在光纤中的传输性能.从而验证系统的可行性.仿真模拟结果表明,在光纤无线通信系统中,正交频分复用比非归零码更具有优势.

基于双平行PM调制的60GHz光毫米波RoF系统研究

提出了一种采用相位调制器产生六倍频光载毫米波的RoF系统。该系统使用一个双平行相位调制器实现六倍频的调制,通过调节相位调制器的相位偏移量,产生出抑制一阶边带的光谱,耦合相减后得到三阶边带信号,在光电检测器中拍频,产生六倍于射频信号的光载毫米波。仿真结果表明,10GHz射频信号可以产生60GHz光载毫米波信号,5Gb/s的数据信号可在单模光纤中传输10km以上。

基于调制边带法的高次倍频光毫米波产生

提出了利用外调制技术的调制边带法的六倍频和八倍频光毫米波产生方案。方案仅采用一个马赫曾德尔调制器,并利用其非线性传输特性,通过调节MZM的偏置电压和调制电压,控制边带的强度,仅保留三阶边带或四阶边带,从而实现六倍频及八倍频光毫米波的产生。采用将基带数据信号仅调制在一个三阶边带或四阶边带分量的方式,有效防止走离。数值分析结果表明,提出的方案仅需10 GHz及7.5 GHz的调制信号频率就能得到60 GHz毫米波,大大减小了调制信号频率,增加了上变频系数,传输距离可达160 km,而功率代价变化不大。与提出的其他高倍频技术相比,由于系统仅采用一个马赫曾德尔调制器,提出的方案系统结构更为简单,且此方案色散影响较小,传输距离更长。

基于光载波抑制产生6倍频毫米波的RoF系统

搭建了一种基于光载波抑制产生6倍频毫米波的RoF系统。系统采用马赫-曾德尔强度调制器(MZM)和滤波器抑制了偶次和一阶光边带,2个三阶光边带在基站端的光电检测器中进行拍频,得到了6倍频毫米波信号。仿真结果表明,采用10 GHz的微波信号,可以产生60 GHz的毫米波,2.5 GB/s的信号可以在单模光纤中传输15 km以上。

地面模拟空间电子环境束流均匀化设计

通过在地面建设装置来模拟空间高能电子环境,能够有效地对航空航天器件在地外空间遭遇电子引起的相关效应进行研究。在模拟装置中,高能电子由电子直线加速器提供,其输出束斑大小为毫米量级,而模拟试验需要大面积且非常均匀的电子辐照环境,所以需要通过一段束流输运线处理,使束流同时满足辐照面积和均匀性要求。本项目的模拟装置空间紧凑,束流输运线短,辐照面积大,利用单一的二维扩束均匀化方案无法实现,因此采用了一种扫描加扩束的方案。根据输运线入口和出口束流参数要求,设计将螺线圈、α-磁铁、扫描磁铁、四极磁铁、聚焦六极磁铁等元件组合使用。通过元件参数匹配和束流校正,使不同能量的电子束在辐照平面处满足辐照面积和均匀度的要求。利用束流跟踪软件仿真计算了0.5 MeV、2.5 MeV和5 MeV束线,束流在不同辐照面积的均匀度均优于90%,满足指标要求。

无光滤波六倍频微波信号产生的系统设计

基于两个级联偏振调制器,提出了一种高频谱纯度、稳定的六倍频微波信号产生方法。该方法通过适当调整偏振片的偏振方向、射频驱动信号电压和相位,实现无光滤波器条件下、任何波段六倍频微波信号的产生。利用Optisystem平台搭建的仿真系统,以S波段4GHz信号为例,验证了该设计系统产生的六倍频信号质量,并分析了非理想射频驱动电压和相位对六倍频信号质量的影响,结果表明:该设计系统能产生最大光边带抑制比、射频无杂散抑制比分别为21.3,15.2dB的六倍频微波信号;且非理想驱动电压和相位差的偏离应控制在理想值±5%的范围之内。

基于串联双电极马赫-曾德尔调制器的六倍频技术

提出并理论分析和实验验证了一种新的产生毫米波的六倍频技术。该方法采用两个相同串联的双电极驱动马赫-曾德尔电光调制器(MZM),调节第一个MZM的偏置电压使其工作在最小传输模式,只输出奇次光谐波分量,调节第二个MZM的偏置电压使其工作在最大传输模式,抑制所有的奇次光谐波分量。实验结果显示,采用10 GHz的射频(RF)信号驱动这两台MZM后,输出60 GHz的毫米波信号,实现了六倍频。通过测量输出的信号性能指标并与未使用带通光滤波器方案作比较得出经过50 km光纤传输后,输出信号受到色散的影响小。