Anisotropic ferrite microstrip antenna simulation and analysis
Introduction
Recent years, it is more and more concentrated on the research of magnetized ferrite. The so called magnetized ferrite is a kind of dispersive dielectric material which shows anisotropy when there is outside magnetic field. The electric-magnetic properties of magnetized ferrite varies with the strength and direction of the outside filed. These properties make it widely applied in microwave integrated circuit and antenna designing. Research shows that by adjusting outside bias magnetic field, the variety of the resonant frequency of microstrip made by anisotropic ferrite base can get to 40% [1]. The radar target covered by anisotropic ferrite can reduce its radar cross section (RCS) in a further way and make it easier to stealth [2]. The research of anisotropic ferrite is widely concentrated. Because of the anisotropy, many research methods are difficult. Lee and his partner take spectral domain moment method to research the RCS of anisotropic ferrite [3]. Yang and her partner use recursive convolution finite-difference time-domain (RC-FDTD) and Z-transform finite-difference time-domain (Z-FDTD) to research the scattering properties [4], [5]. In recent years, Pereda and other teams calculate the electromagnetic wave propagation in dispersive media using shift operator (SO) and other method [6], [7], [8], [9], in 2003, Ge uses shift operator finite-difference time-domain (SO-FDTD) to calculate scattering of anisotropic magnetized plasma[10]. This article analyses ferrite microstrip antenna's impedance and radiation characteristics using SO-FDTD method [11], [12], [13], [18], [19].
Section snippets
Microstrip antenna simulation
The microstrip antenna is of low profile, small size and light weight; it is widely applied in integrated circuit and high-speed vehicle information receiving system [14]. FDTD is a strong tool in simulation method of microstrip antenna. Many wide band properties we can attain by simulating once and it is widely used to analyze the microwave circuit. Takes FDTD method and simulates the ordinary microstrip antenna in [14], the model is shown in Fig. 1. We can get the important parameters like
SO-FDTD method of magnetized anisotropic materials
Substitute the media board of the metal microstrip antenna into magnetized anisotropic ferrite material and it becomes anisotropic ferrite microstrip antenna. Because of the anisotropy of the anisotropic ferrite, we need to derive the formula of electromagnetic field in the ferrite iterative. The Maxwell equations in the magnetized anisotropic medium are written as [11]:
Suppose the outside magnetic field is according to z's positive direction, the relative
Anisotropic ferrite microstrip antenna simulation
Make a programme about magnetized ferrite using SO-FDTD method according to the method above and confirm the correctness of the programme using the example below.
Suppose the polarized plane wave from x direction and transmits according to z direction and incidents into an infinite ferrite plates whose thickness d = 3 cm, the outside magnetic field is according to the z direction. The parameters of the ferrite are α = 0.1, ω0 = 2π × 20 × 109 rad/s, ωm = 2π × 109 rad/s. Fig. 6 shows the reflection coefficient
Conclusions
This paper takes SO-FDTD method to research magnetized ferrite microstrip antenna, derives the iterative relationship of electromagnetic field in the ferrite and applied it into the ferrite microstrip antenna simulations. Research shows that when the outside magnetic field exists and the antenna shows different angles, it will show different electromagnetic properties. Its operating frequency and radiation characteristics will be affected by the magnetic field. When the radiation patch is
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