Yunhua Tan

Reduced-order H∞ filtering for navigation with carrier phase

A reduced-order H∞ filtering algorithm for navigation with carrier phase is presented. By taking advantage of decoupling between filtering states in a navigation solution, this algorithm reduces computational cost and is robust in colored noise. Furthermore, the estimation precision is also improved by taking ambiguities as nuisance states when the filtering process converges. Applications to kinetic simulations under different noise are presented to demonstrate robustness and efficiency of the algorithm.

Improved innovation-based adaptive Kalman filter for dual-frequency navigation using carrier phase

A new adaptive Kalman filtering algorithm for dual-frequency navigation using carrier phase is presented. This algorithm gives consideration to both robustness and sensitivity by combining the two main approaches of adaptive Kalman filtering based on innovation-based adaptive estimation (IAE) and fading filtering. Applicable to the navigation using carrier phase measurements typically, this algorithm can balance the weights of observations and predicted states preferably. Applications to both practical static data and kinetic simulations are presented to demonstrate the validity and efficiency of the algorithm.

A Novel Approximate Solution for Electromagnetic Scattering by Dielectric Disks

This paper presents a novel approximate solution for electromagnetic scattering by planar homogeneous dielectric objects with arbitrary shape. This solution is derived by introducing a semi-empirical formula of the electrical field inside objects under consideration and by exploring the volumetric integral equation along with spectral representation of dyadic Greens function. Afterward, a closed-form approximate solution has also been established by utilizing the so-called stationary phase method (SPM). It is demonstrated that our solution is uniformly valid for planar objects with moderate electrical thickness illuminated from low to high frequencies at all incidence angles. Comparisons with a full-wave computation obtained by the method of moments (MoM) have been examined, which demonstrates that the proposed formulation can provide very accurate results and can perform much better than other existing approximate techniques.

A hybrid FE-BI method using in antenna radiation analysis

A hybrid method which combines the finite element and boundary integral methods (FE-BI) for simulating electromagnetic radiation of antennas is presented. The method not only can correctly model the boundary conditions, but also can deal with complex geometry and material structure. The matrixes formed from FEM are sparse, and the boundary integral method is applied to reduce the simulation complexities and memory needs. The accuracy and efficiency of the method are verified by Bow-tie Antennas.

Scattering characteristics of dielectric periodic structures based on Floquet mode analysis and hybrid finite element methods

The scattering characteristics of dielectric periodic structures are discusses based on Floquet modes analysis and hybrid finite element methods in the paper. Propagating and evanescent Floquet modes are analyzed theoretically. The hybrid finite element method is developed. Then the effects of structure parameters, dielectric material, incident angle and frequency on propagation directions and power of Floquet modes are studied through numerical simulations and analysis. Meaning conclusions are drawn. Thus, this paper is of both theoretical and practical interest for the design and analysis of DPSs.

Volume scattering of 3-D discrete scatterers by using UV multilevel partitioning method

A fast method-UV multilevel partitioning method (UV-MLP) is developed to solve volume scattering by 3-D random-distributed scatterers. In the method Foldy-lax equations with higher order spherical partial wave expansions are used for spherical scatterers. Then the fast method UV-MLP is presented to accelerate the solution, where three key points: multilevel partitioning, rank pre-determination and UV decomposition are introduced. Finally we demonstrate the technique to the electromagnetic scattering problem by a large number of random-distributed particles.

Analysis of a probe-fed bow-tie antenna scattering by using the hybrid FE-BI method

The hybrid finite element and boundary integral method (FE-BI) for analyzing scattering from an active antenna is presented in this paper. First, the principle and formulas of FE-BI method are detailedly demonstrated, in which the contributions from the antenna feed and incident EM fields are simultaneously considered. Then as an example, the radar cross section (RCS) of a probe-fed plane bow-tie antenna is calculated by using this method. The numerical results show that the RCS of the antenna with the feed is obviously different from the same structure but without the feed.

Analysis of frequency-controlled beam scanning based on holographic metasurface

The behavior of frequency-controlled beam scanning based on holographic metasurface, for instance, the scanning accuracy and sensitivity of frequency, has been substantially investigated. An immediate consequence of this work is that we provide a more general guideline of designing holographic metasurface with more flexible features, such as, multi-beam scanning, etc. A selected number of simulation results, calculated by performing the commercial software package of CST Microwave Studio, are presented to verify the proposed theory.

Generalized MED blind deconvolution of GPR data and its sparsity-promoted solution

Over the past decades, numerous efforts have been attempted to enhance the resolution and accuracy of surface ground-penetrating radar (GPR) data by employing blind deconvolution techniques. The fact that most GPR source wavelets utilized in practice are non-minimum phase presents some challenges for blind deconvolution of GPR data. This letter formulates blind deconvolution of GPR data as a sparsity promoted optimization problem, which extends classical minimum entropy deconvolution (MED) strategy and provides a general-purpose framework of blind deconvolution of GPR data. And then an alternating iterative method is explored to solve the derived non-convex optimization problem. Experimental results demonstrate that the proposed methodology is very effective, efficient and flexible.

Reduced-order adaptive Kalman filtering for dual-frequency navigation with carrier phase

A new adaptive Kalman filtering algorithm for dual-frequency navigation with carrier phase is presented. By reducing the filtering order after full-order initialization, this algorithm saves the extra computational cost brought by carrier phase observations. The improved adaptation of state covariance matrix in reduced-order processing also improves filtering precision and robustness. Finally applications on both static data and kinetic simulations demonstrate the validity and efficiency of the algorithm.