Lezhu Zhou

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.

Analysis of electromagnetic scattering from objects coated with arbitrarily magnetized lossy ferrite materials

In this paper, analysis and discussion of electromagnetic scattering from objects coated with arbitrarily magnetized lossy ferrite materials are carried out by using the hybrid vector finite element method and multilevel fast multipole algorithm. For a coated cube as an example, the impact of anisotropy properties controlled by magnetized ferrite materials on the scattered field characteristics is considered. Numerical results show that the strength and direction of the biased magnetic field strongly affect the backscattered field

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.

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 scattering by combined conducting and dielectric bodies using single integral equation method and fast multipole method

In this paper, a single integral equation (SIE) method is developed to analyze the electromagnetic scattering from 3D combined conducting and dielectric objects. Compared with the conventional coupled integral equations method, the SIE method reduces the number of unknowns by a factor of two for dielectric bodies and has faster convergence for an iterative solution. Fast multipole method (FMM) is incorporated to reduce the computing complexity and memory requirement. Numerical results show that the proposed single integral equation method enhanced by fast multipole method (SIE-FMM) is accurate and efficient for analysis of scattering by composite dielectric and conducting objects.

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.

Efficient TDFEM schemes with second-order PML based on different temporal basis functions

The time domain finite element method (TDFEM) formulations have been presented using two kinds of temporal basis functions, B-spline and Lagrange interpolation polynomial, and the computational domain is truncated with second-order perfectly matched layer (PML). This is motivated by utilising good interpolation features of these temporal basis functions and better absorption performances of second-order PMLs. Numerical cases demonstrate that the proposed TDFEM schemes achieve more accurate results with about 5% to 7% increase of run time and 1.5% increase of memory usage compared with the TDFEM scheme with Sacks PML. However, the presented TDFEM schemes merely require 1/6th of the total run time for frequency domain FEM.

Radiation Analysis of Dielectric Conical Conformal Log-Spiral Antennas

Radiation properties of conical log-spiral antennas (CLSA) conformal on dielectric cones are analyzed by using the hybrid finite element and boundary integral equation method (FE-BI) in the paper. Firstly the radiation patterns of CLSA conformal on different dielectric cones and the ordinary CLSA are compared at the same geometry parameters and frequency. Then the influence of the spiral wrap angle and cone angle on the radiation of dielectric conical antennas are discussed. A design of geometry parameters of the dielectric CLSA with best radiation performance are finally obtained based on numerical simulations under the given dielectric parameters.