Automatic clutter-canceler for microwave life-detection systems

A microprocessor-controlled automatic clutter-cancellation subsystem, consisting of a programmable microwave attenuator and a programmable microwave phase-shifter controlled by a microprocessor-based control unit, has been developed for a microwave life-detection system (L-band 2 GHz or X-band 10 GHz). This system can remotely sense breathing and heartbeat movements of living subjects. This automatic clutter-cancellation subsystem improves manual clutter-cancellation in microwave systems. A series of experiments have been conducted to demonstrate the applicability of this microwave life-detection system for rescue purposes. The 2-GHz system performs well for remotely detecting human breathing and heartbeat signals through a pile of rubble of up to about three feet thick     

Microwave interferometry: application to precision measurements and noise reduction techniques

A concept of interferometric measurements has been applied to the development of ultra-sensitive microwave noise measurement systems. These systems are capable of reaching a noise performance limited only by the thermal fluctuations in their lossy components. The noise floor of a real time microwave measurement system has been measured to be equal to -193 dBc/Hz at Fourier frequencies above 1 kHz. This performance is 40 dB better than that of conventional systems and has allowed the first experimental evidence of the intrinsic phase fluctuations in microwave isolators and circulators. Microwave frequency discriminators with interferometric signal processing have proved to be extremely effective for measuring and cancelling the phase noise in oscillators. This technique has allowed the design of X-band microwave oscillators with a phase noise spectral density of order -150 dBc/Hz at 1 kHz Fourier frequency, without the use of cryogenics. Another possible application of the interferometric noise measurements systems include “flicker noise-free” microwave amplifiers and advanced two oscillator noise measurement systems     

A novel method of determining the permittivity of liquids

A novel method to measure the permittivity of liquids is used in a microwave gauging system, developed for the detection of liquid levels in tanks. The system is described as a frequency stepped continuous wave (FSCW) radar for precision liquid level detection. Usually a radar system is only employed to find the surface of the liquid. With the microwave measurement system described here, one can detect a second level that may be the tank bottom or an impurity level, for example. To monitor the permittivity of the liquid with the same measurement system, a novel algorithm is derived. Measured uncertainties of ±0.2 mm have been achieved for the multilevel range detection performed in the frequency range from 2 to 3 GHz. From these measured data, the error of the calculated permittivity was about 2%. By using this technique to determine the permittivity of the liquid, it is possible to reduce the complexity of the measurement system     

微波辐射下均聚和共聚反应机理

研究了微波辐射下单体均聚和共聚反应机理。利用溶剂N，N—二甲基甲酰胺(DMF)或乙醇中的自由基捕捉剂1，1—二苯基—2—三硝基苯肼(DPPH)捕捉自由基，验证反应是否为自由基历程。研究了一些单体体系如烯丙基硫脲(AT)和马来酸二丁基锡(DBTM)或单体与载体(A12O3或SiO2)混合存在下的体系。同样，共聚反应如DBTM—AT和DBTM—硬脂酸乙烯酯(SAVE)也进行了相似的聚合实验。结果表明微波辐射可以引发共聚反应，且符合自由基机理。载体可以促进自由基的生成。     

An investigation into the parameters affecting mass flow rate of ore material through a microwave continuous feed system

An investigation into the characteristics of a gravity-driven conveyor system for passing crushed ore through a microwave cavity has been undertaken using laboratory experiments and numerical modeling. The conveyor system consisted of a vertical hopper, a column passing through the microwave cavity and a tilting vibrating tray. For the efficacy of the microwave treatment of the ore, the residence time of the ore material in the cavity must be known so that the optimum microwave power and exposure time can be calculated, and so that the microwave field can be tuned effectively. The investigation was undertaken using a crushed copper ore from the Palabora mine, South Africa. Four different size fractions and two blends of ore were tested, and the affect of tilt angle and distance between the base of the column and the collector tray were examined. Equivalent numerical models were constructed using discrete element modeling. It was found that the numerical models can be calibrated against the experimental data, and thus can be used to predict flow characteristics, mass flow rates and microwave exposure times which are required in the design of such a conveyor system for microwave pre-treatment.     

基于微波感知的挠性结构动态响应监测

以大跨度桥梁、高架道路为代表的挠性结构在服役过程中的健康监测备受关注和重视,结构动态响应的测量是实现结构健康监测的重要途径。基于微波感知的新型非接触式振动测量(简称"微波测振")技术与方法,开展挠性结构动态特性监测的应用研究。阐述了微波测振系统的组成及基于单频连续波和调频连续波微波雷达的振动测量基本理论与方法。针对工程实际中挠性结构动态响应监测需求与特点,提出微波测振系统的工作模式选择与参数设置准则。基于搭建的微波测振系统开展了轻轨高架箱梁结构在列车运行激励下的振动响应监测实验研究,分析了不同工况下结构的动态响应特性。结果显示,微波测振技术与方法能够准确测量挠性结构的形变与动态响应,为军民领域挠性结构的健康监测提供了一种新的非接触式振动测量技术与方法。     

Überwachung von Niederdruck‐Plasmaanlagen

Monitoring of low pressure plasma systems The optical emission spectroscopy (OES) is a very flexible and easy to use method to monitor industrial plasma processes. By directly monitoring the plasma itself many additional factors influencing low pressure plasma processes can be observed. First of all factors that can not be controlled directly play an important role in this context. Examples are contaminations and leaks in the plasma system. These can negatively influence the reproducibility of production processes. In this paper the effect of a leak on the coating and the plasma process is being shown. Additionally the detection of contaminations and sealing problems in a microwave plasma source is being demonstrated. By using the correlations being presented the OES can be used to continually monitor low pressure plasma systems and thus enhance reproducibility of industrial low pressure plasma processes.     

Design data for quick development of folded H plane tee at high average power level

At high average power level, waveguide-based structures are indispensable in microwave systems due to their higher power handling capacity. These structures are often used to perform power division and combination operation. Folded H plane tee is one of the many components that can be used for the power division application. Its advantage is that the output arms and input arms are in a single plane along a single axis, thus taking less space in the overall system. However, their proper thermal management is indispensable for its use, as high surface temperature of the waveguide reduces its power handling capacity at high power level. This paper presents quick, easy design steps and methodology for obtaining the structure of a folded H plane tee at any given frequency of operation. Further, a scheme for the thermal management for high input power level (500 kW continuous wave) is presented. The proposed methodology is tested at various frequencies in COMSOL Multiphysics, CST Microwave Studio and HFSS with excellent results. A prototype structure was fabricated for use at 3.7 GHz, which exhibited good agreement with the simulation results.     

Microwave studies of chaotic billiards and disordered systems

Many of the concepts developed for the quantum mechanics of classically chaotic or disordered systems are notes genuinely quantum mechanical in origin but can be applied to classical waves as well. This opens up the opportunity of an experimental approach to questions which before were accessible by theory only. As an illustration, microwave results on spectral level dynamics, on field distributions in three-dimensional resonators and on linewidths in open billiards are presented.     

Process monitoring of a thermosetting resin using optical-fiber sensors in a microwave environment

Conventional means of curing thermosetting resins used in advanced fiber-reinforced composites involves heating the sample in an oven or autoclave where heat is transferred to the sample through conduction and convection. In general, the cure schedules that are used can be time consuming and expensive. Hence, significant attempts are being made to improve the processing efficiency and productivity of this class of material. Microwave-based processing has been claimed to offer the advantage of a significantly faster processing time. In this study, two remote (noncontact) sensor systems were designed and developed to facilitate spectral-based quantitative process monitoring inside a custom-modified commercial microwave oven. The two fiber-optic sensor systems were 1) a noncontact optical-fiber reflectance probe and 2) a reusable transmission probe assembly. Spectroscopic data were obtained using the fiber-optic probes at specified microwave power levels. Since conventional metal-based temperature monitoring devices cannot be used in the microwave oven, a low-cost disposable fiber-optic probe was developed. This design was based on an optical fiber-based extrinsic Fabry-Perot interferometer (FPI). The extrinsic FPI temperature sensor demonstrated an accuracy of /spl plusmn/0.5/spl deg/C over the range from ambient to 300/spl deg/C. The temperature of the resin system was also measured simultaneously, along with the spectral data, to monitor the progress of the chemical reaction (curing).     

重质碳酸钙粉体表面微波辅助改性的研究

通过与传统的加热搅拌改性方法的比较,微波辅助改性方法在浊度、浸润度、接触角等方面都优于传统改性方法。实验结果表明,该方法不仅能取代传统的改性加热方式,实现对粉料的表面改性,而且可激发物质内部分子进行超高频振动、摩擦,可实现分子水平上的“搅拌”,这种“激发效应”已开始在高分子合成和固化反应中应用。本文介绍了粉体表面微波辅助改性方法(发明专利申请号:031282598),提出了一套微波辅助改性装置,并以此对重质碳酸钙粉体表面进行异丙基三异硬脂酸基钛酸酯(TTS)改性,实验表明其效果优于传统的加热搅拌改性。     

Fast preparation of entangled states of two qutrits in cavity or circuit QED

We present a scheme for generating entangled states of two qutrits, by using a 4-level system and a 3-level system coupled to a single cavity. Because of only employing resonant interactions, the entangled state can be fast created. This scheme is easy to implement in experiments since only a single cavity is needed and none of measurement, auxiliary system and identical system-cavity coupling constant is required. Furthermore, two-qutrit partially or maximally entangled states can be created by using this scheme. The proposal is quite general, which can be used to prepare entangled states of two qutrits in various physical systems, such as two natural or artificial atoms of the Λ-type or Δ-type three lowest levels, coupled to an optical or microwave cavity.     

基于里德堡原子的微波全信息测量

介绍了里德堡原子微波电场传感器的工作原理,阐述了基于里德堡原子测量微波电场强度、相位、极化、频率等信息的技术特点,分析了基于里德堡原子的微波全信息测量的研究现状,探讨了当前绝对自校准测量和连续宽带高灵敏测量面临的困难,指出可以通过外场调控实现测量灵敏度提升和宽带连续频率测量;并可通过各种调制及解调手段简化相位、极化的测量和读取。分析了在热原子系统中利用多光子激发消除多普勒展宽以及采用冷原子消除多普勒展宽对于提升微波测量灵敏度的潜在优势,提出未来可利用里德堡原子的高轨道角动量态、强关联等特性进一步提升里德堡原子微波电场传感器性能。     

Why Study Noise Due to Two Level Systems: A Suggestion for Experimentalists

Noise is often considered to be a nuisance. Here we argue that it can be a useful probe of fluctuating two level systems in glasses. It can be used to: (1) shed light on whether the fluctuations are correlated or independent events; (2) determine if there is a low temperature glass or phase transition among interacting two level systems, and if the hierarchical or droplet model can be used to describe the glassy phase; and (3) find the lower bound of the two level system relaxation rate without going to ultralow temperatures. Finally we point out that understanding noise due to two level systems is important for technological applications such as quantum qubits that use Josephson junctions. PACS numbers: 16.43.Fs,72.70.+m,75.10.Nr,85.25.Cp     

Generation of chaotic microwave pulses with the help of passive synchronization of spin wave self-modulation frequencies in self-oscillatory ring systems

Passive synchronization (PS) of spin wave self-modulation frequencies of a chaotic microwave signal has been observed for the first time in a self-oscillatory ring system involving a nonlinear passive element with saturable absorption. The development of PS led to the generation of a periodic train of chaotic microwave pulses with an off/duty ratio exceeding 20. It is established that the repetition period of chaotic microwave pulses can be controlled by changing gain in the ring system.     

Non-thermal bioeffects induced by low-intensity microwaveirradiation of living systems

Attention is drawn to a multitude of frequency-specific, nonthermal bioeffects-induced in living systems by ultra-low-intensity microwave radiation-the existence of which is not currently taken into account in the formulation of the safety limits to which microwave devices must conform. An attractive possibility of accounting for these effects is in terms of Frohlich's coherent excitations involving strongly excited macroscopic electric polarisation waves, which, on quite general grounds, he predicted living systems to support-provided they are sufficiently active metabolically-in consequence of the prevalence therein of electric dipoles of various kinds. The therapeutic exploitation of low-intensity microwave irradiation in Russia and the Ukraine is noted, and attention drawn to some recent theoretical work which suggests that water (a dipolar system in its own right) might itself support mesoscopic coherent domains     

微波介质陶瓷介电性影响因素的研究

讨论了微波介质陶瓷中介电性的影响因素.其中本征因素是微波介质陶瓷的完美晶体中能获得的微波介电特性,其损耗是最低的,可由微波电场与晶体振动的非简谐性相互作用计算得出;非本征因素则包括有序-无序度、杂质、晶格缺陷、微结构及晶粒大小等诸多因素.研究了目前微波介质陶瓷的国内外现状,对其今后发展趋势做了讨论.     

Spectral characteristics of a relativistic magnetron with coupled cavities

The spectral characteristics of a relativistic microwave magnetron with cavities coupled via an external waveguide channel have been experimentally studied. It is shown that the output microwave radiation with a stable narrow spectrum and improved energy characteristics can be obtained with properly adjusted coupling in the system.     

Recent developments in lightwave network analysis

The widespread use of photonic systems having microwave modulation bandwidths, coupled with the inclusion of photonic components in microwave and millimetre-wave systems, is creating a demand for efficient characterization techniques. In particular, new tools will be required for the measurement of fundamental quantities such as the microwave frequency response, bandwidth, gain and return loss of microwave photonic components. However, existing lightwave measurement techniques are primitive when compared with conventional RF and microwave network analysis. This paper provides a review of the theory and techniques used for the small-signal characterization of microwave photonic components. State-of-the-art architectures for lightwave network analysers and the two-port calibration techniques are described     

Influence of the amplitude and phase nonlinearity of a spin-wave delay line on the wideband chaotic microwave generation

Regimes of wideband chaotic microwave generation have been studied in a self-oscillating ring system with a nonlinear delay line, in which magnetostatic backward volume waves (MSBVWs) are excited. It is established that a change in length of the delay line influences on its amplitude and phase nonlineartity, thus making it possible to control the characteristics of the chaotic microwave signal generated in the ring. It is demonstrated for the first time that a wideband chaotic microwave signal with a continuous spectrum and a nearly Gaussian probability density distribution can be generated by exciting MSBVWs in a self-oscillating ring system with a nonlinear delay line based on single ferromagnetic film.