Yuliang Chang

Estimation of Precession Parameters and Generation of ISAR Images of Ballistic Missile Targets

The micro-motion properties of the rotational symmetry ballistic targets (BTs) are analyzed in the work presented here. A method for the estimation of precession frequency and the precession angle is proposed based on the polarization properties of the rotational symmetry ballistic targets (BTs). Compared with the traditional precession frequency estimation method, the estimated spectra of the harmonic frequencies are considerably smaller. In addition, an inverse synthetic aperture radar (ISAR) imaging technique based upon the micro-motion of BTs is proposed. The theoretical conclusions are confirmed by the application of the experimental data.

The signal selection and processing method for polarization measurement radar

Based on the ambiguity function, a novel signal processing method for the polarization measurement radar is developed. One advantage of this method is that the two orthogonal polarized signals do not have to be perpendicular to each other, which is required by traditional methods. The error due to the correlation of the two transmitting signals in the traditional method, can be reduced by this new approach. A concept called ambiguity function matrix (AFM) is introduced based on this method. AFM is a promising tool for the signal selection and design in the polarization scattering matrix measurement. The waveforms of the polarimetric radar are categorized and analyzed based on AFM in this paper. The signal processing flow of this method is explained. And the polarization scattering matrix measurement performance is testified by simulation. Furthermore, this signal processing method can be used in the inter-pulse interval measurement technique as well as in the instantaneous measurement technique.

Radiation Characteristics Analysis of Tri-Polarized Dipole Antenna

Dual-polarized antenna involves polarization purity degradation and power gain loss when scanning at wide angles. Aiming at mitigating the above limitations, we exploit a tri-polarized antenna for better radiation characteristics in this letter. We formulate the beampattern synthesis problem of a single tri-polarized dipole antenna in a convex form, and solve it with the Lagrange multiplier method. When circular polarization is synthesized, we show that degree-of-freedom increase improves the polarization purity and power gain of the multipolarized antenna, especially at wide scan angles. We further find that, using the infinite current sheet model, the radiation pattern synthesized by tri-polarized antenna is the same with the optimally oriented dual-polarized antenna - the dual-polarized antenna is mechanically rotated to be oriented normally to the scanning direction. We discuss the situation when linear polarization is synthesized. We show that the power gain is increased corresponding to scan angle, while the polarization purity is not improved obviously.

Target scattering estimation in clutter with polarization optimization

In this paper, we propose an adaptive waveform polarization method for the estimation of target scattering matrix in the presence of clutter. The proposed sequential algorithm, based on the concept of sequential minimum mean square error (MSE) estimation, to determine the coefficients of the scattering matrix, guarantees the convergence and the resulting computational complexity is linear with the number of iterations. The effectiveness of the proposed method is validated through numerical results, underlining the performance improvement given by joint transmission and reception (Tx/Rx) polarization optimization for the scalar system. Also, the results show that the vector system with transmission polarization optimization provides a comparative performance as the scalar measurement system employing joint Tx/Rx polarization optimization. Less computation burden highlights the advantage of the former mode.

Advanced polarization estimation method using the spatial polarimetric characteristic of antenna

The polarization of radar antenna vary with scan direction. This phenomenon is called Spatial Polarization Characteristic (SPC) of antenna. Based on the SPC of single polarized antenna, a novel polarization estimation method is established. Comparing with the traditional estimation method, this one has the following advantages: (i) It does not need dual-polarization channels to estimate the signal polarization; (ii) The polarization and angle of arriving (AOA) of a periodic signal can be estimated simultaneously; (iii) The fullpolarization pattern of the antenna can be matched automatically during the estimation. The feasibility of this method is proved by simulation.