Research And Application Of Magnetic Material In Antenna

Commonly diverse magnetic materials are used in the microwave devices such as phase shifter, isolator, radiator of antenna and RCS reducing. In this paper the gyromagnetic ferrite material is mainly discussed. Gyromagnetic ferrite materials in static magnetic field and frequency varying electromagnetic field exhibit anisotropic characteristics. And its permeability will be a tensor. Using the special properties of the gyromagnetic materials, the pattern reconfigurable antenna and the working frequency are studied in this paper. The main contents are as follows:First of all, theoretical analysis is made on the ferrite non-radiation wave guide. Dielectric strip non-radiative in dielectric waveguide(NRD) is replaced by ferrite material. The ferrite non-radiative waveguide is analysed and designed. The propagation model and field characteristics between ferrite and the conventional NRD waveguide are compared. The propagation characteristic of transverse and longitudinal biased waveguide is discussed. It’s the foundation of later research of pattern reconfigurable antenna.Then for the reconfigurable pattern, theoretical analysis is made on the ferrite waveguide leakage wave antenna. Two kinds of pattern reconfigurable waveguide leaky wave antenna are designed based on different magnetic direction. On one side of the parallel metal walls the waveguide leaks wave from rectangular opening apertures. By tuning longitudinal bias magnet field, changing waveguide propagation constant realizes the scanning of antenna pattern. And another leaky wave antenna with transverse bias ferrite is designed with the metal grating microwave periodic structure. Scanning the leaky wave antenna pattern by tunable space harmonic, a more reliable way realizes the pattern reconfiguration function. The experimental results show that the antenna has the pattern reconfigurable function.Finally, based on the theoretical analysis of the planar symmetric dipole antenna, the frequency reconfigurable antenna is studied. The ferrite is used to cover the planer dipole, and the equivalent electrical length of the dipole is tuning by the applied magnetic bias. The influence of 1/4 wavelength slot-line and the metal boundary of the magnet on the resonant frequency and the pattern is discussed. And the experimental results show that the antenna has the function of working frequency tuning by changing the magnetic field.