单次瞬态过程频谱分析仪

本文叙述了一个适用于各种单次瞬态过程的频谱分析仪的工作原理和实验结果。本仪器利用实验室现有设备(通用示波器和声频频谱仪等),经过适当组装和附加少量专用电路,可以较快地建成。利用时间扩展(或压缩)技术,可以将欲测的频谱波段移到声频波段。用光电函数发生器产生待测的瞬态过程的重复波形。这样,就可以用一般的声频频谱仪(或波分析仪)来模拟测量单次瞬态过程的频谱。实验结果证明上述方案是可行的。对主要频谱成份,测量可准确到2—3％。对较弱的频谱成份,准确度要差些。     

高功率毫米波绕射辐射振荡器高频特性研究

 讨论了高功率毫米波绕射辐射振荡器的高频特性。利用线性理论和PIC模拟相结合的方法对器件的高频特性进行了比较仔细的分析。分析结果表明，合理地选择电子注的参量（电流、电压）及高频结构的尺寸（波纹深度、半径、周期等）可以获得较高的输出功率并且具有较好的频谱纯度。     

Photoluminescence enhancement in manganese-doped magnesium stannate phosphors synthesized by millimeter-wave irradiation

We have investigated photoluminescence (PL) of Mg₂SnO₄:Mn phosphors synthesized by the irradiation with millimeter-wave of 24 GHz. The PL spectrum at room temperature is dominated by a green band peaking at 500 nm, suggesting the existence of tetrahedral Mn²⁺ sites. When the phosphors are grown by the millimeter-wave heating, the 500 nm band is so much intense compared to those by the electric furnace heating. To clarify the origin of the PL enhancement, we have carried out the measurements of scanning electron microscope (SEM) and electron spin resonance (ESR). The SEM image exhibits the growth of small round particles with an average size of 1.6 μm. Such well-grown micron-sized particles were not observed under the electric furnace heating. The ESR spectra exhibit six prominent lines, the intensity of which becomes greater for the phosphors obtained by the millimeter-wave heating. From this observation, it is supposed that the PL enhancement is mainly due to the increase in the number of tetrahedral Mn²⁺ sites. Therefore, the millimeter-wave heating has an important advantage over the electric furnace heating in the synthesis of Mg₂SnO₄:Mn phosphors.     

一种测量弱光拍频的方法

提出一种基于光子相关测量技术的弱光拍频测量方法. 与传统的方法不同，该方法不依赖于频谱分析仪，不受探测器和前置放大器响应时间的限制，所测拍频能达到10GHz量级，并且可对非常弱的光进行测量. 关键词： 拍频 自相关函数 Hanbury Brown Twiss实验 弱光     

Millimeter-Wave Signal Generation and Harmonic Upconversion Through PM-IM Conversion in Chirped Fiber Gratings

A novel technique for generating millimeter-wave signals through phase-to-intensity modulation conversion in chirped fiber gratings is proposed and demonstrated. Experimental results on generating a 28 G Hz signal using harmonics orders from 7th to 10th are provided. Excellent phase-noise performance (87 dBc Hz @ 10KHz) is demonstrated. It is also demonstrated that this technique may be efficiently used for harmonically upconverting intermediate frequency signals to the millimeter-wave band. Bit-error-rate measurements for different modulation format (QPSK MQAM) signals, which were upconverted employing the PM-IM conversion technique, show very good performance (< 10 ^{- 9}) and transparency to the modulation format.     

Passive and temporally continuous optical spectral analyzer of RF signals via wavelength coding

A novel approach realizing an optical spectrum analyzer for photonic detection of an unknown RF carrier signals is presented. The described module may be part of an electronic warfare system in which detection of a narrow band RF signal is required. Moreover, The RF signal is characterized by an unknown time varying carrier frequency embedded in wide band noise. The system uses a passive, fiber based photonic configuration. It allows the spectrum mapping of an incoming electronic RF signal modulated on an optical carrier. The spectral analyzer configuration uses a finite impulse response (FIR) filter that is realized by two different optical paths of parallel fibers which generate a spectral notch filter. Hence, a wavelength coding is realized by chromatic dispersion such that each wavelength is filtered by a different FIR filter. Therefore, the energy at a WDM demux output channels is actually proportional to the spectrum of the input RF signal. This spectral mapping is obtained without lose of temporal RF information.     

Experimental study of annoyance due to low frequency environmental noise

We have carried out a study of a particular environmental noise phenomenon which appears to be a cause of real and severe disturbance to certain people. The study has been based on field measurements and on laboratory studies and questioning involving two people who have suffered from this problem for some years. The disturbance is heard by them as a ‘throbbing’ sound and is particularly prevalent indoors, rather than out-of-doors.The study has indicated that the phenomenon arises with a broad band spectrum which lies close to the hearing threshold and which is unbalanced to the extent that the major stimulus occurs in the frequency range 20–100 Hz. It is suggested that the unbalanced spectrum may arise as a result of low frequency noise generated by distant industrial sources.     

A PARALLEL COUPLED-LINE FILTER USING VLSI BACKEND INTERCONNECT WITH HIGH RESISTIVITY SUBSTRATE

This paper reports our progress in developing parallel coupled-line filters based on Si-based VLSI backend interconnects for millimeter-wave applications. The resonant frequency of this coupled-line filter increases with increasing spacing-gap and with increasing IDM thickness. By using high resistivity substrate, the parallel coupled-line band-pass filter is extremely effective in reducing substrate loss, and also provides very low insertion loss, even at the millimeter-wave regime. In addition, the parallel coupled-line filter suitable for advanced system-on-a-chips at the millimeter wave application achieves high performance characteristics, which show low insertion loss, wide band, and compatibility with standard VLSI process.     

Electron spectroscopic studies of the adsorption of methanol on zinc oxide powder

X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and Auger electron spectroscopy (AES) have been used to study the adsorption of methanol on ZnO powder. The He(II) spectrum of electron-beam-eleaned ZnO was similar to that reported by Rubloff .¹ for the ZnO (11̄ 0 0) surface. The spectrum of methanol condensed at ?150°C matched that of gas-phase methanol. At low methanol coverages, difference spectra showed no increase in the methanol O(2p) lone pair binding energy reported to be indicative of chemisorption. A residual carbon and oxygen surface component on the ZnO powder may have prevented chemisorption. XPS measurements were found to be more useful in observing this layer than was AES. A decrease in the ZnO valence band intensity near the valence band maximum indicated that a strong interaction with the substrate had occurred.In this system the valence bands of the adsorbate and substrate overlap, and the true position of the methanol O(2p) lone pair orbital is obscured by the effects of the substrate band modification. Also, for insulators or semiconductors, a change in the measured position of the valence band maximum relative to the Fermi level may occur upon adsorption. Since the Zn(3d) core level should not be affected, it was used as an energy reference for the present work. The problems of energy referencing in UPS studies of adsorption on semiconductors are discussed.     

D波段双球镜准光系统测量低耗介质

采用双球镜准光腔、频谱仪和锁相返波管组建了D波段低损耗介质测试系统,该系统通过频谱仪和外置谐波混频器得到腔体谐振测试数据,并用拟合或积分方法从谐振曲线中求解出准光腔的品质因数。测得双球镜开腔的固有品质因数大于8105,使该系统在工作波段可测量损耗角正切为10-5量级的低损耗介质。用该系统测出的石英、人造金刚石和蓝宝石的介电常数和损耗,与报道的结果一致,并测得4H-SiC在132.07 GHz的介电常数实部为9.598,损耗角正切为6.110-5。     

Q波段宽频带线性化器设计

当前我国Q/V频段的低轨卫星互联网项目正在大力开展,宽带通信正在逐步发展。而国内相关线性化技术一般局限于较窄频带,相关研究尚不成熟。因此尽快研究设计宽频带线性化器十分有必要。采用适用于空间环境的模拟预失真技术,设计出针对卫星通信所用的行波管功率放大器（TWTA）的Q波段线性化器。其利用新型微带传输结构,结合肖特基二极管,可在毫米波频段实现超宽瞬时频带的线性化。在38～43 GHz（5 GHz）的瞬时频带内对TWTA的幅度失真以及相位失真有着很好的改善。线性化器在输入功率为−17～13 dBm的范围内,频带内幅度增益约为4.8～7.2 dB,相位扩张约为70°～88°。相对其他同类型线性化器,此线性化器对应频率较高,且可在很宽的瞬时频带内对TWTA实现比较稳定的线性化。     

Improved frequency response measurement method of half-wave voltage for phase modulator

In this paper, the improvement method of the traditional optical spectrum analyzer (OSA) is demonstrated to measure the half-wave voltage of LiNbO₃ phase modulator with low RF driving. Based on calculating the measured powers ratio of the carrier and first-order side band with optical spectrum analyzer (OSA), the phase modulation index is between 0.5 and 1.43 and the voltage of driving signal is lower than 0.796 V, the accurate characterization of the phase modulator is obtained. By using this method, the half-wave voltage of a LiNbO₃ phase modulator had been measured in the frequency range of 26 GHz. And, our experimental results showed a good agreement between the measured data and those provided by the manufacturer in 9 GHz frequency range. It is an accurate and easy method to measure the half-wave voltages of a phase modulators, especially for measuring high the frequency response.     

Retrieval of vertical stratosphere temperature profile from ground-based measurements of atmospheric self-radiation spectrum in millimeter-range lines of molecular oxygen

The retrieval technique of the vertical stratosphere temperature profile from ground-based measurements of the atmospheric self-radiation spectrum in a millimeter-wave range is proposed. This technique is based on the Bayesian approach to solving an inverse problem and includes assumptions on the measurement noise, as well as some prior information about the retrieved profile. The possibility of temperature retrieval in the range of 20–55 km with 10 K accuracy is demonstrated.     

D波段双球镜准光系统测量低耗介质

采用双球镜准光腔、频谱仪和锁相返波管组建了D波段低损耗介质测试系统,该系统通过频谱仪和外置谐波混频器得到腔体谐振测试数据,并用拟合或积分方法从谐振曲线中求解出准光腔的品质因数。测得双球镜开腔的固有品质因数大于8105,使该系统在工作波段可测量损耗角正切为10-5量级的低损耗介质。用该系统测出的石英、人造金刚石和蓝宝石的介电常数和损耗,与报道的结果一致,并测得4H-SiC在132.07 GHz的介电常数实部为9.598,损耗角正切为6.110-5。     

Application of Millimeter Wave in Verification of Scale Model Measurement for Radar Cross Section

According to the physical optic approximation, a physical scale factor is suggested for scale model measurement of radar cross section (RCS). By this factor, the models of radar targets can be tested at the same frequency as prototype. This is significant for the lack of experimental equipment required or the problem of frequency dependency of radar absorbing materials on the objects. For the purpose of further verification and comparison, millimeter-wave is used to measure the model at the wavelength scaling down proportionally to the prototype. And the measurements of the models are also carried out at microwave band (same working wavelength with prototype). The computed results from models agree well with the data by prototype itself.     

Application of Millimeter Wave in Verification of Scale Model Measurement for Radar Cross Section

According to the physical optic approximation, a physical scale factor is suggested for scale model measurement of radar cross section (RCS). By this factor, the models of radar targets can be tested at the same frequency as prototype. This is significant for the lack of experimental equipment required or the problem of frequency dependency of radar absorbing materials on the objects. For the purpose of further verification and comparison, millimeter-wave is used to measure the model at the wavelength scaling down proportionally to the prototype. And the measurements of the models are also carried out at microwave band (same working wavelength with prototype). The computed results from models agree well with the data by prototype itself.     

一种基于串联谐振腔的高性能光电振荡器

提出了一种利用串联谐振腔来抑制光电振荡器边模的方案. 此方案中, 在传统光电振荡器结构中加入无源微波谐振腔结构来提高滤波器的Q值. 分析了该结构的基本原理, 并与传统光电振荡器结构进行对比, 此结构能有效提高边模抑制比. 实验中产生了10 GHz的微波信号, 所测得的边模抑制比达72 dB, 单边带相位噪声为-122 dBc/Hz@10 kHz. 同时, 利用锁相技术, 振荡频率的稳定性得到了很大的改善, 在3 h内漂移小于± 4 Hz. 该方案无需增加有源器件, 保留了传统光电振荡器低相位噪声的优势, 又有效抑制了边模, 为光电振荡器的应用提供了一种新的方法.     

The millimeter-wave spectrum of methoxyacetonitrile

This paper is the second as part of a study to elucidate cyano group chemistry in the interstellar medium, wherein we present a characterization of the millimeter-wave spectrum of methoxyacetonitrile. Its structural isomer, 2-cyanoethanol was described in paper Braakman and Blake (submitted for publication) [1]. The rotational spectrum of methoxyacetonitrile shows the characteristics of a well-behaved asymmetric rigid-rotor. We assigned nearly 7400 transitions to 2 conformers and 2 excited states. All were fit to Watson A-reduced Hamiltonians, including only the effects of centrifugal distortion. The lowest energy states are fit close to experimental accuracy, with a gradual decrease in quality for higher energy states. No repulsive interactions are apparent. The measurements and predictions from the fits reported here are being used as a basis for observational studies of this species.     

Luminescence of solid cyclic polynitramines

The solid form of the cyclic polynitramines known as RDX and HMX have a weak absorption band in the near ultraviolet which is not observed in spectra of the solvated compounds. Fluorescence measurements on solid samples of these materials show a weak emission, the excitation spectrum of which corresponds to this absorption band. Phosphorescence measurements on the solids at 77 K reveal a long-lived emission, the excitation spectrum again corresponding to the weak absorption band. The absorption and the luminescence bands are attributed to charge-transfer self-complex formation in the solid state, and estimates of the energies of the emissive singlet and triplet excited states are given.     

一种面向信息带宽的频谱感知方法研究

本文利用频带宽度先验信息,提出一种面向信息带宽的自适应调制宽带转换器结构.该结构的总采样率为信号信息带宽的四倍,远小于信号的奈奎斯特采样频率,从而更有效利用采样资源,降低采样数据量,提高处理实时性.通过对该结构中随机波形函数周期的选择,可以实现对系统采样率和系统物理实现复杂度的权衡取舍,从而适应不同场合中的应用.本文通过理论分析给出了该结构实现信号精确重构的充分条件.引入多重信号分类算法,分析了该结构适用此算法的充分条件.本文通过仿真实验对上述分析进行了有效性验证.该系统可以应用于隐形装备的吸波材料的前端特性分析、认知无线电的频谱感知.