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高阻抗表面的设计与测量

更新时间：2019-12-17 19:56:16 大小：704K 上传用户：18139413306查看TA发布的资源 标签：高阻抗 下载积分：1分 评价赚积分 （如何评价?） 打赏 收藏 评论(0) 举报

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The design process of High Impedance Surface (HIS) is a challenge in realizing low-profile antenna. To carry out properly this process, a 3D-electromagnetic simulator is required. This paper shows an overview of the different numerical techniques which can be applied to simulate the behaviour of an HIS

using CST Microwave Studio (CST MWS). The considered HIS is composed of a metallic square patches array printed on the top of a metal backed substrate. To demonstrate the validity of the different solvers used, some measurements of the dedicated structure have been performed in a waveguide simulator.


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Design and Measurement of High Impedance  
Surface  
F. Linot∗†, R. Cousin‡, X. Begaud∗, M. Soiron†  
Institut Telecom - Telecom ParisTech - LTCI - CNRS - UMR 5141  
∗
46 Rue Barrault, 75634 Paris, France  
,  
‡
CST AG  
Bad Nauheimer Str. 19, D - 64289 Darmstadt, Germany  
†
THALES Airborne Systems  
78852 Elancourt Cedex France  
Abstract—The design process of High Impedance Surface  
(HIS) is a challenge in realizing low-profile antenna. To carry out  
properly this process, a 3D-electromagnetic simulator is required.  
This paper shows an overview of the different numerical tech-  
niques which can be applied to simulate the behaviour of an HIS  
R
using CST Microwave Studio ꢀ (CST MWS). The considered  
HIS is composed of a metallic square patches array printed on  
the top of a metal backed substrate. To demonstrate the validity  
of the different solvers used, some measurements of the dedicated  
structure have been performed in a waveguide simulator.  
I. INTRODUCTION  
(a)  
This research is in the framework of collaboration between  
Telecom ParisTech and Thales Airborne Systems to design  
low-profile antenna considering high impedance surface (HIS).  
To develop tools to simulate HIS, a partnership with CST  
R
AG ꢀ has been done. These surfaces can exhibit surface  
wave band gaps where the propagation of electromagnetic  
waves is prohibited [1]. High impedance surfaces can exhibit  
frequency band where the propogation of electromagnetic  
wave is prohibited. Moreover these structures can imitate  
the interesting phase behaviour of a hypothetically perfect  
magnetic conductor (PMC) at resonance: the high-impedance  
surface reflects all of the power just like a perfect electric  
conductor (PEC), but it reflects in-phase, rather than out-of-  
phase, allowing the radiating element to be directly adjacent  
to the surface. High impedance surface consists on a periodic  
(b)  
Fig. 1. (a) Part view of the infinite HIS analyzed, (b) View of the lattice  
considered  
metallic arrangement printed on a metal-backed substrate. To this paper the Finite Integration Technique (FIT) is used as  
design HIS easily and quickly, several analytical models based a generalization of the FDTD approach. The FIT approach  
on an equivalent transmission line model have been proposed which has been developed at CST is using the Perfect Bound-  
[2]. However all the geometry’s dimensions must be smaller ary Approximation (PBA) as a better geometry discretization  
than the wavelength in order to consider a quasi-static model without increasing the memory consumption. As the previous  
[3], and a Computational Electromagnetic (CEM) simulation methods mentioned, the accuracy of the results depends on the  
is required to demonstrate the validity of designing complex volume mesh computed. To demonstrate the validity of this  
3D-HIS structures. Several ”full-wave” methods namely the computational code in the high impedance surfaces domain,  
Finite Difference Time Domain method (FDTD) [4], and a HIS consisting of a metallic square patches array printed  
the Finite Element Method (FEM) [5], are widely used to on the top of a metal backed substrate is studied. The goal  
plot the reflection coefficient of the artificial structure. These of this paper is to describe several approaches to validate  
numerical methods consist on a volume discretization to solve the reflection coefficient of an HIS using CST MICROWAVE  
R
the Maxwell’s equations using different mesh techniques. In STUDIO ꢀ (CST MWS) in order to predict the behaviour of  
such devices. In this paper, only the phase relection property hexahedral mesh discretization. This technique reveals to be a  
is considered but all these approaches can be used to predict highly efficient method as it combines easy-to-use cartesian  
the absorption coefficient [6]. All the results are compared and grids without any approximation of the structure geometry  
validated to measurement done in a waveguide simulator [7]. [8]. The PBA can improve the geometry description without  
increasing the memory. As illustrated in Fig. 2, the hexahedral  
mesh grid is applied to the structure with a denser mesh near  
II. OVERVIEW OF THE DIFFERENT APPROACHES  
The reflection property of high impedance surfaces is gen-  
erally described by the reflection coefficient which is the ratio  
of the reflected field on the incident field at the top of the  
structure.  
the edges of the PEC sheet for a better ElectroMagnetic (EM)  
field discretization. In CST MWS, several methods can be used  
to simulate the reflection phase in normal incidence. Firstly  
the analytical expression (1) can be computed in a Visual  
Basic language for Application (VBA) which requires three  
simulations in that case: one for extracting the incident field  
components without any parasitic reflection in the calculation  
domain, the second one to take into account the modified E-  
field components reflected at an equivalent PEC reference and  
the last one to deduce the phase shift created by the real case.  
An Electric Probe is required to record the time signals for all  
the three simulations. This method can be used to simulate  
the reflection phase diagram of finite structure. However,  
this method requires few minutes to simulate the reflection  
coefficient of the real structure [9]. Another method is used,  
consisting in defining the appropriate boundary conditions to  
introduce a crossed-E and H-field such that a TEM wave is  
applied similar to a plane wave considering one single element  
as infinitely periodic in the x and y directions. The reflection  
phase diagram is then computed for normal incidence of the  
ElectroMagnetic (EM) field propagation. The phase reference  
Zs − Z0  
Γ =  
(1)  
Zs + Z0  
Where Zs and Z0 are respectively the surface impedance  
of the structure and the free space impedance. For a perfect  
electric ground plane, the reflected E-field and the incident E-  
field have opposite signs, resulting in a coefficient reflection  
equal to -1. In the case of a hypothetically PMC surface,  
the reflection phase is null corresponding to a coefficient  
reflection equal to +1. However, HIS reveals that they can  
realize the PMC condition in a certain frequency band. At very  
low frequency, the HIS behaves like a PEC. At the resonant  
frequency, the impedance of the structure tends to infinity,  
resulting in a zero reflection phase. To calculate the reflection  
phase of an high impedance surface, a plane wave illuminating  
the structure where a PEC surface is set as a reference leads  
to a normalization of the reflected phase of the HIS (ΦHIS  
from the PEC surface (ΦP EC):  
)
Φ = ΦHIS − ΦP EC + π  
(2)  
A surface impedance is comprised of metallic square  
patches printed on the top of a metal backed dielectric sub-  
strate without vias (see Fig.1a). According to Fig. 1a, the  
parameters of the high impedance surface analyzed are: P =  
4mm, g = 0.4mm, h = 1mm and ꢀr = 10.2. Where P is the  
periodicity of the patch array, g is the gap between adjacent  
patches, h the height of the dielectric substrate and ꢀr the  
relative permittivity of the host medium. As the HIS is a  
periodic structure, only one lattice is needed to discribe the  
behaviour of the whole structure. With the periodic boundary  
conditions used, the structure can be modelled as an infinite  
surface (see Fig. 1b).  
(a)  
A. The Time Domain  
All time domain ”Full-Wave” methods such as FIT, FDTD  
and TLM techniques use a conformal cartesian grid. Whereas  
the FDTD approach uses the hexahedral mesh grid, this dis-  
cretization has some limitations when complex 3D-structures  
have to be simulated at higher frequency range for which the  
level of accuracy has to be enhanced. For a better geometry  
discretization, mainly thin structures, rounded solids and shell  
objects, the PBA was implemented in connection with the FIT  
to reduce the global number of mesh cells of an equivalent  
FDTD simulation for a considerable enhanced level of ac-  
curacy. For instance, that means that a mesh cell can take  
(b)  
Fig. 2. Hexahedral discretization of the lattice: (a) Front view, (b) Perspective  
into account two different material properties in the global view  

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