Angle Estimation for MIMO Radar in the Presence of Gain-Phase Errors with One Instrumental Tx/Rx Sensor: A Theoretical and Numerical Study

Ideal transmitting and receiving (Tx/Rx) array response is always desirable in multiple-input multiple-output (MIMO) radar. In practice, nevertheless, Tx/Rx arrays may be susceptible to unknown gain-phase errors (GPE) and yield seriously decreased positioning accuracy. This paper focuses on the direction-of-departure (DOD) and direction-of-arrival (DOA) problem in bistatic MIMO radar with unknown gain-phase errors (GPE). A novel parallel factor (PARAFAC) estimator is proposed. The factor matrices containing DOD and DOA are firstly obtained via PARAFAC decomposition. One DOD-DOA pair estimation is then accomplished from the spectrum searching. Thereafter, the remainder DOD and DOA are achieved by the least squares technique with the previous estimated angle pair. The proposed estimator is analyzed in detail. It only requires one instrumental Tx/Rx sensor, and it outperforms the state-of-the-art algorithms. Numerical simulations verify the theoretical advantages.

Two-Stage Fast DOA Estimation Based on Directional Antennas in Conformal Uniform Circular Array

In conformal array radar, due to the directivity of antennas, the responses of the echo signals between different antennas are distinct, and some antennas cannot even receive the target echo signal. These phenomena significantly affect the accuracy of direction-of-arrival (DOA) estimation. To implement accurate DOA estimation in a conformal uniform circular array (UCA) composed of directional antennas, the two-stage fast DOA estimation algorithm is proposed. In the pre-processing stage, multi-target decoupling and target detection are mainly used to obtain the targets’ range bin indexes set; in the rough-precise DOA estimation stage, the amplitude and phase information of each antenna are used for rough DOA estimation and precise DOA estimation, respectively. Based on simulation and actual anechoic chamber radar experiments, and through quantitative analyses of the accuracy, validity and elapsed time of the two-stage fast DOA estimation algorithm compared with the directional antenna MUSIC (DA-MUSIC), sub-array MUSIC (S-MUSIC) and Capon-like algorithms, results indicate that the two-stage fast DOA estimation algorithm can rapidly and accurately estimate DOAs in a multi-target scenario without the range-angle pair-matching procedure. Lower computational complexity and superior estimation accuracy provide the two-stage fast DOA estimation algorithm a broader application prospect in the practical engineering field.

Description of Changes in Crystal Orientations by the Elements of Logarithm of a Rotation Matrix

The logarithmln⁡Rof rotation matrixRis a skew symmetric tensor consisting of three independent elements of real numbers. In addition to the Euler angles and the axis/angle pair, the elements ofln⁡Rcalled the log angles are also the set of three parameters ofR. In this paper, we will show that the concept of the log angles is also useful to discuss changes in crystal orientations. The changes inRas a function of the position are given by the changes in the log angles. As an example, orientation changes caused by arrays of dislocations in a plastically deformed Cu single crystal are discussed.

Effect of the Metallurgical State of Austenite on the Microtexture Properties of the Bainitic Transformation in a Low Alloy Steel

The effect of the metallurgical state of austenite (undeformed vs. deformed vs. deformed + recrystallised) on the properties of the austenite to bainite transformation were investigated thanks to thermal (Gleeble simulations) and thermomechanical (hot torsion) treatments. No obvious influence of the state of austenite was found, using electron backscatter diffraction, on the resulting microtexture. Advantages and drawbacks of using misorientation angle histograms vs. axis-angle pair distribution are discussed regarding investigations of local variant selection. For an austenite grain size higher than about 50 µm, a strong effect of the transformation temperature was evidenced, bainite formed at lower temperature (530°C) exhibiting a microtexture close to that of lath martensite in the same steel.

Light scattering size estimation of nearly monodisperse spherical particles in the multivalued region: A reminiscence

For the size estimation of large, nearly monodisperse spherical particles, the forward angle dissymmetry technique (FAD) has been used and the results compared with data obtained by the transmission electron microscopy (TEM) and integral turbidity ratio (ITR) methods. Starting with a certain relative particle size which depends on the chosen angle pair, the FAD functions go through several extremes and become multivalued. The possibility of the particle size estimation under such conditions and, also, without the knowledge of actual particle concentration (but knowing the relative refractive index), is discussed in this paper.

Computer-aided orientation relationship determination in non-cubic systems

Classical electron diffraction techniques for determining the orientations of grains within a polycrystalline material are time consuming. However, many of the steps involved in the process of indexing a convergent beam diffraction (CBED) pattern, eliminating the 180° ambiguity and establishing an axis-angle pair orientation relationship are ideally suited to microcomputer assistance, especially when working with non-cubic systems. The procedure described is an off-line technique applied to a study of alpha alumina, for which extensive electron diffraction data has recently been compiled.