Phased array for millimeter wave frequencies

A phased array is presented at a frequency of 70 GHz, consisting of a corporate feed, ferrite phase shifters and dielectric rod antennas. Metal waveguides were utilized to construct the feed network, whereas a special dielectric waveguide structure was employed for the ferrite phase shifter and dielectric rod antenna. Beam scanning can be performed electronically controlled in the horizontal plane.     

物理光学法分析反射面天线辐射场

利用物理光学方法分析天线的远区辐射场具有计算速度快和内存需求少的特点,目前已被广泛应用于反射面天线的远区辐射场计算中。推导了利用斯特拉顿-朱兰成远场积分方程计算天线远区电场的表达式,计算了某一偏馈反射面天线的方向性,与文献中已有结果比较表明,方向图结果是正确的。馈源的方向图模型设置为余弦函数的q次方,利用增益公式近似推导了天线的增益,将这一计算方法应用于赋形反射面天线的远场分析中,通过对比反射面天线赋形前后波束扫描过程中不同扫描角度处的方向图,验证了赋形设计对于提高天线增益平坦度的有效性。     

Measurement of non-monotonous phase changes in temporal speckle pattern interferometry using a correlation method without a temporal carrier

Recently, a phase evaluation method was proposed to measure nanometric displacements by means of digital speckle pattern interferometry when the phase change introduced by the deformation is in the range [0,π) rad. This method is based on the evaluation of a correlation coefficient between two speckle interferograms generated by both deformation states of the object. In this paper, we present a novel technique to measure non-monotonous displacements in temporal speckle pattern interferometry using a correlation method without a temporal carrier. In this approach, the sign ambiguity is resolved automatically due to the introduction of a function that determines the correct sign of the displacement between two consecutive speckle interferograms. The rms phase errors introduced by the proposed method are determined using computer-simulated speckle interferograms. An application of the phase retrieval method to process experimental data is also presented.     

Continual deformation analysis with scanning phase method and time sequence phase method in temporal speckle pattern interferometry

If a laser beam illuminates a continual deformation object surface, it will lead to a temporal speckle pattern on the observation plane. Recording this time-dependent speckle pattern the deformation of the surface of an object can be obtained. Two methods, scanning phase method (SPM) and time sequence phase method (TSPM), have been introduced for measuring the displacement caused by the deformation in temporal speckle pattern interferometry (TSPI). Their principle is that by capturing a series of speckle interference patterns related to the object deformations, the fluctuations in the intensity of the interference patterns can be obtained. Through scanning these fluctuations and estimating both the average intensity and modulation of the temporal speckle interference patterns, the phase maps for whole-field displacements are calculated. In this way one is capable of quantitatively measuring continual displacements simply using a conventional electronic speckle pattern interferometry (ESPI) system without phase shifting or a carrier. The elaboration on the new methods is given in this paper and experiments are performed to demonstrate their performance with a conventional ESPI system.     

高功率无移相器自旋转波束扫描天线设计

设计了一种无移相器结构的平板高功率天线,通过辐射层自旋转方式改变口径场相位分布,从而实现空间波束扫描,满足轻质、低剖面集成要求,辐射增益36 dB,波束扫描范围-30°至+30°,GW级功率容量,满足Ku波段工作的系统指标与能力要求。对天线进行了实物加工与测试,测试结果说明该天线具有良好的波束扫描特性和较高的口径辐射效率。无需加载移相馈电网络便可改变波束指向,具有伺服简单,结构紧凑,平面化、低剖面、轻质等优点,可广泛应用于机载、车载、舰载等高功率微波系统的表面共形发射。     

Binary phase only filters for rotation and scale invariant pattern recognition with the joint transform correlator

The joint transform correlator (JTC) is one of the two main optical image processing architecture which provides a highly effective way of comparing images in a wide range of applications. Traditionally, an optical correlator is used to compare an unknown input scene with a pre-captured reference image library, to detect if the reference occurs within the input. Strength of the correlation signal decreases rapidly as the input object rotates or varies in scale relative to the reference object. The aim of this paper is to overcome the intolerance of the JTC to rotation and scale changes in the target image. Many JTC systems are constructed with the use of ferroelectric liquid crystal (FLC) spatial light modulators (SLMs) as they provide fast two-dimensional binary modulation of coherent light. Due to the binary nature of the FLC SLMs used in the JTC systems, any image addressed to the device need to have some form of thresholding. Carefully thresholding the grey scale input plane and the joint power spectrum (JPS) has significant effect on the quality of correlation peaks and zero order (DC) noise. A new thresholding technique to binarise the JPS has been developed and implemented optically. This algorithm selectively enhances the desirable fringes in the JPS which provide correlation peaks of higher intensity. Zero order noise is further reduced when compared to existing thresholding techniques.Keeping in mind the architecture of the JTC and limitations of FLC SLMs, a new technique to design rotation and scale invariant binary phase only filters for the JTC architecture is presented. Filers design with this technique have limited dynamic range, higher discriminability among target and non-target objects, and convenience for implementation on FLC SLMs. Simulation and experiments shows excellent results of various rotation and scale invariant filters designed with this technique. A rotation invariant filter is needed for various machine vision applications of the JTC. By fixing the distance between camera and input object, the scale sensitivity of the correlator can be avoided. In contrast to the industrial machine vision applications, scale factor is very important factor for the applications of the JTC systems in defence and security. A security system using a scale invariant JTC will be able to detect a target object well in advance and will provide more time to take a decision.     

Use of photoelectron laser phase determination method for attosecond measurements with quantum-mechanical calculations

This paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measurements of the pulse natural properties of x-ray intensity and the instantaneous frequency profiles. As a direct procedure without any previous pulse profile assumptions and time-resolved measurements as well as data fitting analysis, this method can be used to improve the time resolutions of attosecond timing and measurements with metrological precision. The measurement range is half of a laser optical cycle.     

晶体相场法研究预变形对熔点附近六角相/正方相相变的影响

应用双模晶体相场模型计算二维相图,并模拟了在熔点附近预变形和保温温度对六角相晶界演化以及六角相/正方相相变的影响.研究发现:在相变初期,当预变形为零、保温温度离熔点很近时在晶界发生缺陷诱发预熔;增大预变形,变形与缺陷的交互作用在熔点附近诱发预熔;随着预变形的进一步增大,变形在畸变处同时诱发液相和正方相,且预变形越大、保温温度越接近熔点,液相生长越明显,反之正方相生长明显.持续保温使得畸变能释放,晶粒最终完全转变为平衡正方相.模拟结果表明:预变形六角相在熔点附近保温时,由于晶界固有缺陷和预变形双重作用使得原子无序度增加,从而在晶界或其他缺陷处产生液相,待能量释放后晶粒再转变成平衡正方相,进而延缓了六角相/正方相相变时间.     

Plasticity-induced characteristic changes of pattern dynamics and the related phase transitions in small-world neuronal networks

Phase transitions widely exist in nature and occur when some control parameters are changed. In neural systems, their macroscopic states are represented by the activity states of neuron populations, and phase transitions between different activity states are closely related to corresponding functions in the brain. In particular, phase transitions to some rhythmic synchronous firing states play significant roles on diverse brain functions and disfunctions, such as encoding rhythmical external stimuli, epileptic seizure, etc. However, in previous studies, phase transitions in neuronal networks are almost driven by network parameters （e.g., external stimuli）, and there has been no investigation about the transitions between typical activity states of neuronal networks in a self-organized way by applying plastic connection weights. In this paper, we discuss phase transitions in electrically coupled and lattice-based small-world neuronal networks （LBSW networks） under spike-timing-dependent plasticity （STDP）. By applying STDP on all electrical synapses, various known and novel phase transitions could emerge in LBSW networks, particularly, the phenomenon of self-organized phase transitions （SOPTs）： repeated transitions between synchronous and asynchronous firing states. We further explore the mechanics generating SOPTs on the basis of synaptic weight dynamics.     

等离子体的三频点微波透射衰减诊断方法

 依据微波在等离子体中的传播特性,并利用微波透射非磁化等离子体时在三个相邻频率点的透射能量衰减值,可同时诊断等离子体中的电子密度和电子碰撞频率。使用该方法对100～700 Pa范围内氦气辉光放电等离子体进行了诊断,选择6.2,6.8和7.4 GHz三个频率点,并与使用双探针诊断的诊断结果进行比较。结果表明：两种诊断方法所得碰撞频率基本一致;微波透射衰减法诊断出的电子密度值与探针法的诊断结果在同一数量级(1016 m^-3),但前者约是后者的1.67倍。最后对造成这一差异的原因进行了分析。三频点微波透射衰减诊断方法可用于较高气压及其它静电探针使用受限的环境下,并且可以采用能量较小的微波,不会对等离子体本身造成显著影响,适用于等离子体的初步诊断。     

等离子体双频点微波透射衰减诊断法

介绍了利用非磁化等离子体中微波在两个相邻波长处的透射衰减值来反推该等离子体频率(从而得到电子密度)和电子碰撞频率的方法───双频点微波透射衰减诊断方法。陈述了利用扫频信号源、标量网络分析仪和宽带喇叭天线等构成的系统对微波衰减测量的过程,对该方法的诊断误差进行了讨论。双频点微波透射衰减诊断法适用于大气压等离子体的初步诊断。     

等离子体的三频点微波透射衰减诊断方法

依据微波在等离子体中的传播特性,并利用微波透射非磁化等离子体时在三个相邻频率点的透射能量衰减值,可同时诊断等离子体中的电子密度和电子碰撞频率。使用该方法对100～700 Pa范围内氦气辉光放电等离子体进行了诊断,选择6.2,6.8和7.4 GHz三个频率点,并与使用双探针诊断的诊断结果进行比较。结果表明：两种诊断方法所得碰撞频率基本一致;微波透射衰减法诊断出的电子密度值与探针法的诊断结果在同一数量级(1016 m-3),但前者约是后者的1.67倍。最后对造成这一差异的原因进行了分析。三频点微波透射衰减诊断方法可用于较高气压及其它静电探针使用受限的环境下,并且可以采用能量较小的微波,不会对等离子体本身造成显著影响,适用于等离子体的初步诊断。     

Implementation of a nonlocal N-qubit conditional phase gate using the nitrogen–vacancy center and microtoroidal resonator coupled systems

Implementation of a nonlocal multi-qubit conditional phase gate is an essential requirement in some quantum infor- mation processing （QIP） tasks. Recently, a novel solid-state cavity quantum electrodynamics （QED） system, in which the nitrogen-vacancy （NV） center in diamond is coupled to a microtoroidal resonator （MTR）, has been proposed as a poten- tial system for hybrid quantum information and computing. By virtue of such systems, we present a scheme to realize a nonlocal N-qubit conditional phase gate directly. Our scheme employs a cavity input-output process and single-photon interference, without the use of any auxiliary entanglement pair or classical communication. Considering the currently available technologies, our scheme might be quite useful among different nodes in quantum networks for large-scaled QIP.     

On the use of stimulated Brillouin scattering as a calibration method for group delay and differential group delay measurements

We propose a novel group delay and differential group delay calibration method for polarization-dependent optical spectral characterization measurements. The calibration method is based on the dispersive nature of stimulated Brillouin scattering and its polarization dependent spectral response. The main advantage of the calibration method is its tunability in wavelength, bandwidth and magnitude, what makes it suitable for different measurement setups.     

Analysis of the characteristics of NRD waveguides loaded with periodic metallic strips by using the method of lines for millimeter wave filter and antenna application

In this paper, the propagation characteristics of NRD waveguide loaded with periodic metallic strips are analyzed in terms of the method of lines. Numerical results show that such structures are most suitable for millimeter wave bandstop filter and NRD waveguide beam scanning leaky wave antenna application.     

Identification of the pressure-induced phase transition of ZnSe with the positron annihilation method

This paper studies the pressure-induced phase transition between zincblende (B3) and NaCl (B1) structure ZnSe by using the hydrostatic pressure first-principles pseudopotential plane wave method. The energy-volume and enthalpy-pressure curves are employed to estimate the transition pressure. It is found that ZnSe undergoes a first-order phase transition from the B3 structure to the B1 structure at approximately 15 GPa derived from the energy-volume relation and 14 GPa based on deduction from enthalpy-pressure data. The pressure-related positron bulk lifetimes of the two ZnSe structures are calculated with the atomic superposition approximation method. In comparison with the 13.4% reduction in volume of ZnSe at the transition pressure, the positron bulk lifetime decreases more significantly and the relative value declines up to 22.3%. The results show that positron annihilation is an effective technique to identify and characterize the first-order phase transition and can give valuable information about changes in micro-scale, such as volume shrinkage and compressibility.     

饱和功率密度下线性啁啾对交叉偏振波输出特性的影响

交叉偏振波(XPW)技术是一种基于具有各向异性特征的三阶非线性晶体的非线性滤波技术,由于结构简单,稳定可靠,是超强超快激光领域提高时域对比度、压缩脉宽的有效手段之一.在实验中发现,XPW的输出特性受驱动脉冲特性的直接影响,通过理论计算得到了XPW的脉宽和光谱宽度与驱动脉冲的啁啾特性关系,同时利用声光可编程色散滤波器设计实验对理论计算进行了验证.结果表明:实验结果很好地反映了理论计算得出的结论,同时在饱和功率密度条件下,还表现出了一些理论计算没有反映出的新现象,即XPW的光谱展宽突破了驱动脉冲宽度√3倍的限制,最终脉宽也能够压缩至小于入射脉宽的1/√3;此外对于相反线性啁啾的驱动脉冲所产生的XPW信号,其在光谱形状上有明显的偏移差异,同时输出效率也有所不同.最后对这些新现象进行了进一步的分析和理论解释.     

Optical simulation of in-plane-switching blue phase liquid crystal display using the finite-difference time-domain method

The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display.Compared with the matrix optic methods and the refractive method,the finite-difference timedomain method,which is used to directly solve Maxwell's equations,can consider the lateral variation of the refractive index and obtain an accurate convergence effect.The simulation results show that e-rays and o-rays bend in different directions when the in-plane switching blue phase liquid crystal display is driven by the operating voltage.The finitedifference time-domain method should be used when the distribution of the liquid crystal in the liquid crystal display has a large lateral change.     

Simulation of Lamb wave reflections at plate edges using the semi-analytical finite element method

In typical Lamb wave simulation practices, effects of plate edge reflections are often not considered in order to simplify the wave signal interpretations. Methods that are based on infinite plates such as the semi-analytical finite element method is effective in simulating Lamb waves as it excludes the effect of plate edges. However, the inclusion of plate edges in a finite plate could render this method inapplicable, especially for transient response simulations. Here, by applying the ratio of Lamb mode reflections at plate edges, and representing the reflection at plate edges using infinite plate solutions, the semi-analytical finite element method can be applied for transient response simulation, even when the plate is no longer infinite.     

Encryption and decryption using a sandwich phase diffuser made by using two speckle patterns and placed in the Fourier plane: Simulation results

In the present paper, we describe the encryption and decryption of two-dimensional images. The encryption is done by employing a sandwich phase diffuser made by using two elongated speckle patterns, and placed in the Fourier plane of a double random phase encoding system. After encryption, the two constituent phase diffusers of such a sandwich diffuser are separated. During decryption, if the conjugate of either of the two elongated phase speckle patterns is used, the image cannot be retrieved. Correct decryption is also not possible if a sandwich diffuser with any of the phase speckle patterns is shifted in position with respect to the other. For decryption, the encrypted image is Fourier transformed and multiplied by the conjugate of the sandwich diffuser, and then the product is further Fourier transformed. It is possible to generate the image only if both the elongated phase speckle patterns are matched point-to-point and then the proper conjugate is made. The use of elongated speckle patterns in constituting a sandwich phase diffuser makes the system less complicated as compared to the use of a sandwich diffuser made with normal speckle patterns, enabling an easy alignment of the random phase diffuser at the time of rejoining the constituent diffusers for making the right key. The ease of alignment is due to the reduction of the requirement of 360° scanning at the time of rejoining these diffusers with little reduction in the security of the system. Simulation results are presented in support of the proposed idea. For optical implementation, the decrypted image may be obtained by generating a phase conjugate wave by the phase conjugation technique, and passing through the same sandwich phase diffuser. To evaluate the reliability of the technique, mean square error (MSE) between the decrypted and original image has been calculated.