Wei-Jiang Zhao

An Effective and Efficient Approach for Radiated Emission Prediction Based on Amplitude-Only Near-Field Measurements

A new approach is proposed for modeling electromagnetic emissions of a printed circuit board (PCB) based on amplitude-only near-field measurement data. Magnetic dipoles placed over the top layer of the PCB are introduced as the equivalent of actual radiated sources. A restarted optimization procedure based on a differential evolution algorithm is developed to determine the parameters of the dipoles (number, position, and moment components) via minimizing the difference between the measured magnetic near field and that radiated by the dipoles. These equivalent dipoles can be used to predict the radiated emissions of the PCB once being determined. The proposed approach does not need the phase of the measured near fields, and its computational complexity is very low. Numerical results are presented to demonstrate the validity and efficiency of the proposed approach.

Analysis of Radiation Characteristics of Conformal Microstrip Arrays Using Adaptive Integral Method

A new surface integral equation formulation is presented for characterizing electromagnetic radiation by conformal microstrip arrays on finite curved bodies of arbitrary shapes. The surface equivalence principle is used to reduce the original problem to two equivalent problems, one for the external medium and another for the internal medium. Electric field integral equations are applied to the conducting surfaces, and weighted sums of the field integral equations corresponding to the external and internal dielectric regions with appropriate weighted coefficients are applied to the dielectric interface. The integral equations are solved via the method of moments (MoM) procedure, to which the memory requirement and computational complexity pertinent is reduced by employing the adaptive integral method (AIM). Numerical results are presented to demonstrate the validity and accuracy of the method.

Installed Radiation Pattern of Patch Antennas: Prediction based on a novel equivalent model.

A simple but efficient equivalent model of patch antennas is proposed for predicting the radiation pattern of patch antennas on large platforms. The equivalent model is constructed based on the radiation mechanism of a patch antenna. Only three design parameters need to be optimized, making the model more computationally efficient than those equivalent dipole models for general problems. After the equivalent model is optimized with a differential evolution (DE) algorithm, it is further installed on a platform to compute installed radiation patterns. Simulation results show that the installed radiation patterns of both a single element and an array can be accurately predicted using the equivalent model, where the root-mean-square errors (RMSEs) are less than 0.94%. The proposed equivalent model method does not require detailed geometry information of the patch antennas. Furthermore, it avoids direct modeling of antenna structures, leading to a drastic reduction in computation and storage costs.

AN EFFICIENT HYBRID TECHNIQUE FOR ANALYSIS OF THE ELECTROMAGNETIC FIELD DISTRIBUTION INSIDE A CLOSED ENVIRONMENT

This paper presents an e-cient hybrid simulation technique for analysis of the electromagnetic fleld interactions between multi-transmitters and receivers located within a closed environment. The Method of Moments/circuit method is flrst used for modeling of the transceivers and their nearby surrounding to obtain the equivalent sources/receivers. Then, an approach that combines the asymptotic method and the ray tracing technique is deployed to calculate the long-distance coupling between a pair of transmitter and receiver. The acceleration algorithms for ray tracing have been developed to deal with more complex scenarios. The seamless combination between the circuit, numerical, and asymptotic approaches is the key to get accurate simulation results. Several numerical examples and experimental results are presented to demonstrate the e-ciency of the proposed technique.

Estimating Interference to Airborne Patch Antenna With Limited Information

In practice, the detailed geometry information of an off-the-shelf antenna is unavailable. To achieve the estimation of radio frequency interference to an airborne patch antenna with available information, this paper proposes to utilize an equivalent model of the patch antenna. The equivalent model is derived based on the patch antennas radiation pattern. It shows the same radiating and scattering performances as the original patch antenna. Since, no effective port or phase information is provided by the equivalent model, the reaction theorem was employed to calculate the interference without such information. Simulation and measurement results show that the proposed method can effectively estimate the interference to patch antennas with limited information. Furthermore, it avoids direct modeling of the complex structure of patch antennas and reuses the radiating fields of equivalent models which significantly reduces the computation time and memory cost.

A linear model of transmission coefficients for placement of monopole antennas on electrically large cylindrical surfaces

Based on the ray analysis of monopole excitation, this work proposes a linear model of transmission coefficients against the logarithm of the distance between monopole antennas on electrically large cylindrical surfaces. The linear model is determined by using two sample data, and it is then used to predict the transmission coefficient between two monopole antennas. Given the desired level of transmission coefficient, the distance between monopole antennas can be calculated using the linear spatial model, which is useful for the placement of monopole antennas on electrically large cylindrical surfaces. Simulation results are presented to illustrate the effectiveness of the proposed linear model.

Far-field prediction from amplitude-only near-field measurements using equivalent electric currents

A general and flexible approach is presented for predicting far-field radiated emissions from a device using phaseless magnetic near-field scan data, which is based on the replacement of the actual radiating sources by an equivalent set of electric currents over a planar surface near the device. These equivalent currents used to predict the far-field radiated emissions are determined from near-field scan data by solving two independent nonlinear inverse problems with a global optimization algorithm. Numerical examples are presented to demonstrate the validity and capability of the presented approach.

Modeling of transmission characterisation in aircraft cabins with a hybrid technique

A hybrid technique which combines the integral equation (IE) method and the multiple image theory (MIT) is presented for modeling the electromagnetic wave propagation in a closed environment like aircraft cabins. The IE method with a method of moments (MoM) procedure is employed for analyzing the transmitting antenna. The obtained current on each basis function is acting as a source, and all its multiple images with reference to the wall planes for multiple reflections up to a given order are found out. The multiple images are then used to track the multiple reflected ray paths and further used for the calculation of reflected fields. Since no unknowns are used on the cabin walls, the hybrid technique is well suited for electrically large cabin problems. Numerical examples are presented to demonstrate the accuracy and capability of the presented technique.

Surrogate-model based isolation analysis of slotted waveguide antennas

This paper addresses the issue of isolation analysis of slotted waveguide antennas (SWAs) when their detailed structures are unavailable. A surrogate model, built from information about radiation patterns, was usually employed for this purpose. It reproduced far/near fields of the original antenna, but failed to provide port and phase information which was essential to the isolation calculation. This work fills the above gap by exploiting the reaction theorem with certain approximations. The proposed method enables the isolation analysis in the absence of detailed information of SWA, which is useful especially for antennas bought off-the-shelf. Moreover, it obviates the need for modeling the complex structure of SWA, so as to reduce the computational time and memory usage. Numerical validation illustrates the effectiveness of the proposed method.

Analysis of High-Frequency Electromagnetic Scattering by Complex Targets Using Dual Flat Facet Representation

It is usually difficult to cater for multiple scattering and shadowing in the application of high-frequency asymptotic methods for electromagnetic (EM) scattering since this involves complicated geometrical computation. Efficient techniques with the use of dual flat representation of the target geometry are proposed to overcome this drawback. The dual facet representation is formed by a set of small triangular facets and an additional set of relatively large triangular facets. The set of smaller facets is used for the EM analysis so that approximation can be adopted to avoid the complicated geometrical computation associated with multiple scattering and shadowing, and the set of larger facets is applied for the computation of line/facet interaction and geometrical reflection to achieve computational efficiency. Numerical results are presented to demonstrate the validity and efficiency of the present technique, and the effect of the facet size on the solution accuracy is discussed.