Direction and polarization estimation for coherent sources using vector sensors

A two-dimensional direction-of-arrival （DOA） and polarization estimation algorithm for coherent sources using a linear vector-sensor array is presented. Two matrices are first constructed by the receiving data. The ranks of the two matrices are only related to the DOAs of the sources and independent of their coherency. Then the source’s elevation is resolved via the matrix pencil （MP） method, and the singular value decomposition （SVD） is used to reduce the noise effect. Finally, the source’s steering vector is estimated, and the analytics solutions of the source’s azimuth and polarization parameter can be directly computed by using a vector cross-product estimator. Moreover, the proposed algorithm can achieve the unambiguous direction estimates, even if the space between adjacent sensors is larger than a half-wavelength. Theoretical and numerical simulations show the effectiveness of the proposed algorithm.

Design of a compact polarization beam splitter based on a deformed photonic crystal directional coupler

In this paper a compact polarization beam splitter based on a deformed photonic crystal directional coupler is designed and simulated. The transverse-electric （TE） guided mode and transverse-magnetic （TM） guided mode are split due to different guiding mechanisms. The effect of the shape deformation of the air holes on the coupler is studied. It discovered that the coupling strength of the coupled waveguldes is strongly enhanced by introducing elliptical airholes, which reduce the device length to less than 18.Sttm. A finite-difference tlme-domain simulation is performed to evaluate the performance of the device, and the extinction ratios for both TE and TM polarized light are higher than 20 dB.

A Low Profile Four-Way Directional Antenna with Dual Polarization

This paper presents a low profile dual polarized directional antenna composed of loop and dipole arrays mounted on a ground plane with each loops and dipoles being fed independently. Each loop antenna is paired with a reflector while each dipole antenna is paired with a director and a reflector. The proposed antenna is intended for an indoor base station (BS) with resonance frequency of 2.4 GHz and capable of producing four orthogonal directional pattern with downward elevation angle equals to 30°;and half power bandwidth (HPBW) less than 80°;in both vertical and horizontal polarization. The reflection characteristics of the loop and dipole arrays are less than -10 dB and the mutual coupling between the vertical and horizontal polarization elements is nearly less than -20 dB. In later progress, the dipole antenna was substituted with printed dipole antenna to achieve a better performance. Both the calculated and measured results demonstrated that the desired radiation patterns were achieved, and the measured results agreed well with the calculated ones. Consequently, a low profile antenna with a thickness of 0.16 λ (20 mm) having the expected radiation pattern is successfully designed.

Relationship measurement between ac-Stark shift of^40Ca^+clock transition and laser polarization direction

Ac-Stark shift of atom levels is caused by an ac-electromagnetic field. As an electromagnetic wave, laser light does induce ac-Stark shift. It is proved experimentally that if the light is linearly polarized, the dynamic polarizability changes with polarization direction. The polarization direction of the linearly-polarized laser is tuned by 720°, and the ac-Stark shifts of the 4S1/2,m=±1/2→3D5/2,m=±1/2 clock transitions in ^40Ca^＋ are measured in steps of 10°. The frequency shifts change with laser polarization in a periodical manner and have values opposite to each other.

Quantum secure direct communication protocol with blind polarization bases and particles＇ transmitting order

This paper presents a modified secure direct communication protocol by using the blind polarization bases and particles＇ random transmitting order. In our protocol, a sender （Alice） encodes secret messages by rotating a random polarization angle of particle and then the receiver （Bob） sends back these particles as a random sequence. This ensures the security of communication.

Numerical modeling of anisotropy paradoxes in direct current resistivity and time-domain induced polarization methods

Based on an analytical solution for the current point source in an anisotropic half-space,we study the apparent resistivity and apparent chargeability of a transversely isotropic medium with vertical and horizontal axes symmetry,respectively.We then provide a simple derivation of the anisotropy paradoxes in direct current resistivity and time-domain induced polarization methods.Analogous to the mean resistivity,we propose a formulation for deriving the mean polarizability.We also present a three-dimensional finite element algorithm for modeling the direct current resistivity and time-domain induced polarization using an unstructured tetrahedral grid.Finally,we provide the apparent resistivity and apparent chargeability curves of a tilted,transversely isotropic medium with diff erent angles,respectively.The subsequent results illustrate the anisotropy paradoxes of direct current resistivity and time-domain induced polarization.

Detection of thiopurine s-methyltransferase mutations by template directed determinator in incorporation with fluorescence polarization (TDI-FP)

Objective: To develop a new method for the detection of TPMT gene mutations and determine the frequencies of four TPMT alleles, TPMT *1, *3A , *3B and *3C in a healthy Chinese population. Methods: A TDI-FP assay system was set up in out lab. To evaluate this system, 220 healthy individuals were analyzed for the polymorphic sites at positions 460(G→A)and 719(A→G)of the TPMP gene using our new TDI–FP method. Results: Three TPMP*3C(G 460→G 719) heterozygotes were identified, TPMP *3A and TPMP *3B were not found. All mutations were confirmed by conventional DNA sequencing analysis. Conclusion: TDI-FP method has proven to be very efficient as a rapid and accurate approach for TPMP genotyping. TPMP *3C was the only polymorphism identified in this clinical samples we have registered.

Phase and direction dependence of photorefraction in a low-frequency strong circular-polarized plane wave

Contrary to the superposition principle, it is well known that photorefraction exists in the vacuum with the presence of a strong static field, a laser field, or a rotational magnetic field. Different from the classical optical crystals, the refractive index also depends on the phase of the strong electromagnetic field. We obtain the phase and direction dependence of the refractive index of a probe wave incident in the strong field of a circular-polarized plane wave by solving the Maxwell equations corrected by the effective Lagrangian. It may provide a valuable theoretical basis to calculate the polarization evolution of waves in the strong electromagnetic circumstances of pulsar or neutron stars.

Analysis of a Verifying Method of Consistency Between CT/ PT Polar-ity and Directional Protective Relaying

The coordination correctness of Nuclear power plant current transformer (CT)/ voltage transformer (PT) polarity and relay protection is often verified through the dynamic test on the unit no load / load operating conditions. This paper proposes a test method to prevent and circumvent the failure of the dynamic test abnormality caused by the static power test before the plant power is applied and the whole group is started. Reduce the dynamic test workload and test difficulty, to ensure that the dynamic test safety risk control and control in the state.

基于Directionlets变换的偏振图像融合

论文提出一种有效的基于Directionlets变换的偏振图像融合算法。首先采用多方向多尺度的Directionlets变换对多个偏振图像进行分解,对于分解后的低频系数采用加权平均融合算法;根据高频子图边缘分布差异,对于方向高频系数采用2维Teager能量的边缘检测算法以及区域方向对比度算法实现偏振图像的融合处理。实验结果表明,与传统算法相比,提出的算法在保留原始图像边缘和纹理信息的同时,可以有效地取得较好的融合视觉效果。

The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction

The relation between corresponding trigonometric functions in two rotating coordinate systems is presented. The transformation formula for a vector in the two rotating spherical coordinate systems is obtained. The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction are derived. These fields in a particular case retrogress to those available in the literature. The obtained results have great potential in practical applications.

Joint estimation of DOA, frequency, and polarization based on cumulants and UCA

A joint estimation algorithm of direction of arrival （DOA）, frequency, and polarization, based on fourth-order cumulants and uniform circular array （UCA） of trimmed vector sensors is presented for narrowband non-Gaussian signals. The proposed approach, which is suitable for applications in arbitrary Gaussian noise environments, gives a closed-form representation of the estimated parameters, without spectral peak searching. An efficient method is also provided for elimination of cyclic phase ambiguities. Simulations are presented to show the performance of the algorithm.

Estimating DOA and polarization with spatially spread loop and dipole pair array

The nonuniform L-shaped spatially spread loop and dipole（SSLD） array whose inter-element spacing is greater than half a wavelength is studied. A joint parameter estimation algorithm of direction of arrival（DOA）, frequency and polarization is presented for plane-wave signals. The direct sampling and the corresponding delayed sampling data are used to construct the data correlation matrix. On the basis of the subspace theory and the least square method, the frequency and the steering vector of the whole array are obtained. According to the relationship of the array manifold vector between electric dipoles and magnetic loops,the polarization parameters are given. The unambiguous phase estimates are acquired by applying virtual baseline array transformation to the spatial steering vectors, and they are used as coarse references to disambiguate the cyclic phase ambiguities in phase differences between two adjacent array elements on the array,then the high accuracy DOA estimates are obtained. Closed-form solutions for each parameter are obtained. This method has advantages of lower calculation complexity and no parameter matching. The experiment results verify the effectiveness and feasibility of the presented algorithm.

Quaternion based joint DOA and polarization parameters estimation with stretched three-component electromagnetic vector sensor array

The three-component electromagnetic vector sensor (EMVS) consisting of co-centered orthogonally oriented x-dipole, z-dipole and z-loop is considered. In order to make full use of the spatial aperture of each component, the original uniform linear three-component EMVS array (ULTEA) is stretched into one half-wavelength spaced uniform linear loop subarray (ULLSA) along the z axis, and one sparse uniform linear co-centered orthogonally oriented dual-dipole (CODD) subarray (SULCSA) along the x axis. Then, a generalized rotation invariance based quaternion multiple signal classification (GRIQ-MUSIC) algorithm is presented for direction of arrival (DOA) and polarization parameters estimation. According to the proposed algorithm, the elevation angles are firstly estimated based on the half-wavelength spaced ULLSA. Then the polarization phase differences and azimuth angles are obtained based on the coupling relationship between the angle domain and polarization domain, but the azimuth angles are in coarse-resolution since the array aperture is not utilized. Next, the SULCSA is used to re-estimate the azimuth angles in fine-resolution, and the ambiguity problem can be resolved by the least square method. Finally, based on the estimated elevation angles, azimuth angles and polarization phase differences, the corresponding auxiliary polarization angles can be estimated by N times one-dimensional parameter search, where N is the sources number, and the parameters are matched automatically. Based on the GRIQ-MUSIC algorithm, the high dimensional parameters search problem of the conventional Q-MUSIC algorithm is simplified to a one-dimensional parameter search problem, thus the proposed algorithm not only reduces the computation complexity considerably, but also avoids the performance degradation caused by the failure in parameters pairing. The simulation examples demonstrate the effectiveness and feasibility of the proposed algorithm. © 1990-2011 Beijing Institute of Aerospace Information.

Direct method of finding first integral of two-dimensional autonomous systems in polar coordinates

A direct method to find the first integral for two-dimensional autonomous system in polar coordinates is suggested. It is shown that if the equation of motion expressed by differential 1-forms for a given autonomous Hamiltonian system is multiplied by a set of multiplicative functions, then the general expression of the first integral can be obtained, An example is given to illustrate the application of the results.

Joint Estimation of 2-D DOA and Polarization by Using the Linear Array with Diverse Polarizations

A linear array of diversely polarized antennas with one pair of identical sensors is used to obtain closed-form unambiguous estimation of 2-D direction of arrival （DOA） and polarization. Spatial phase information together with weighted 3-D polarization-angular coherence structure （PACS） are first recovered with fourth-order cumulants manipulation via a new 2-D ESPRIT variant. Spatial filtering is performed to obtain the scaled PACS, from which the closed-form 2-D DOA and polarization estimates can be derived with only quadrant ambiguity involved. The undesired quadrant ambiguity can be further resolved by using the acquired estimate of spatial phase factor.

Estimation of DOA and Polarization Parameters with 2-Level Nested Vector-Sensor Array Based on Quaternion Model

The quaternion coherence problem exists in the data model of the conventional dimensional reduced quaternion estimation of signal parameters via rotational invariance techniques(DRQ-ESPRIT), and DRQ-ESPRIT would lose degrees of freedom(DOFs)when it is used to implement the spatial smooth operation. An improved DRQ-ESPRIT algorithm based on 2-level nested vector-sensor array is proposed in this paper. The quaternion coherence problem is solved by switching the multiplication sequence of spatial direction vector and electric field. Meanwhile, nested array and Khatri-Rao subspace approach are used to increase the number of DOFs, thus the proposed algorithm can estimate more incident sources than DRQ-ESPRIT, and the estimations of direction of arrival(DOA)and polarization parameters are more accurate. Simulation results demonstrate the effectiveness of the proposed algorithm.

Polarization quaternion DOA estimation based on vector MISC array

This paper examines the direction of arrival(DOA)estimation for polarized signals impinging on a sparse vector sensor array which is based on the maximum interelement spacing constraint(MISC).The vector array effectively utilizes the polarization domain information of incident signals,and the quaternion model is adopted for signals polarization characteristic maintenance and computational burden reduction.The features of MISC arrays are crucial to the mutual coupling effects reduction and higher degrees of freedom(DOFs).The quaternion data model based on vector MISC arrays is established,which extends the scalar MISC array into the vector MISC array.Based on the model,a quaternion multiple signal classification(MUSIC)algorithm based on vector MISC arrays is proposed for DOA estimation.The algorithm combines the advantages of the quaternion model and the vector MISC array to enhance the DOA estimation performance.Analytical simulations are performed to certify the capability of the algorithm.

Influences of surface and flexoelectric polarization on the effective anchoring energy in nematic liquid crystal

The physical effects on surface and flexoelectric polarization in a weak anchoring nematic liquid crystal cell are investigated systematically. We derive the analytic expressions of two effective anchoring energies for lower and upper substrates respectively as well as their effective anchoring strengths and corresponding tilt angles of effective easy direction.All of these quantities are relevant to the magnitudes of both two polarizations and the applied voltage U. Based on these expressions, the variations of effective anchoring strength and the tilt angle with the applied voltage are calculated for the fixed values of two polarizations. For an original weak anchoring hybrid aligned nematic cell, it may be equivalent to a planar cell for a small value of U and has a threshold voltage. The variation of reduced threshold voltage with reduced surface polarization strength is also calculated. The role of surface polarization is important without the adsorptive ions considered.

Directional Chiral Optical Emission by Electron-Beam-Excited Nano-Antenna

Manipulating directional chiral optical emissions on a nanometer scale is significant for material science research. The electron-beam-excited nanoantenna provides a favorable platform to tune optical emissions at the deep subwavelength scale. Here we present an L-shaped electron-beam-excited nanoantenna(LENA) with two identical orthogonal arms. By selecting different electron-beam impacting sites on the LENA, either the lefthanded circularly polarized(LCP) or the right-handed circularly polarized(RCP) emission can be excited. The LCP and RCP emissions possess different emission directionality, and the emission wavelength depends on the arm length of the LENA. Further, we show a combined nanoantenna with two LENAs of different arm lengths.Induced by the electron beam, LCP and RCP lights emit simultaneously from the nanoantenna with different wavelengths to different directions. This approach is suggested to be informative for investigating electron-photon interaction and electron-beam spectroscopy in nanophotonics.