Doped Hexagonal Ferrite Microstrip Dielectric Antenna

In this paper based on hexagonal ferrites with high resonance frequency, the electromagnetic properties of the impure hexaferrites in the range of 1 MHz to 1GHz have been carried put. Based on the results of material research, we made an primary investigation on the applications of the hexaferrites to magnetic microtrip antennas. With the intention of increasing the permeability and decreasing the loss, we have systemicly studied the effects of the technics and composites on the electromagnetic properties of the hexaferrites, especially the effect of CaCO3 and BST additives on the electromagnetic properties of Z-type and M-type hexaferrites. Some good results were obtained.1. The effect of the substitution of Co-Ti for Fe3+ on the M-type hexaferrite was studied. It was proved that of BaTixCoxFe12-2XO19 firstly increased then decreased with the increasing of x. when x=1.2, the magnetic anisotropism change to the basal plane from the c-axis, at the same time ,. is the max and the frequency is the least.2. The effect of CaCO3 additive on the Z-type ferrite was studied. With the increasing of CaCO3 content,of Z-type ferrite and the loss decreased. Choosing a proper amount of CaCO3 additive can reduce the electromagnetic loss.3. Having known the basic theory of the ferrites, we doped BST in Z-type hexaferrite (Ba3(Coo.4Zn0.6)2Fe23.4O41). It was found that the effect of BST additive on microstructure and crystal growth of Z- type hexaferrite was different from that of M-type hexaferrite. There were some new phenomena in BST/ Ba3(Zno.6Coo.4)2Fe24O41 (Z- type hexaferrite). As the amount of BST increases, the major phase changes to Z-phase, simultaneously M-phase and perovskite phase appear, and the grain size increases; but in BST/ BaTi1.4Co1.4Fe9.2O19 (M-type hexaferrite), BST additive restrained the crystal growth, which made the size of crystal small.4. After the electromagnetic parameters were measured, it was discovered that with the increasing of BST, the density, the relative complex permittivity and permeability of Z-type hexaferrite increased, at the same time resonance peaks shift to low frequency region. When BST=2.0wt% and the frequency is lMHz,37, which is much higher than that of the pure Z-phase hexagonal ferrite; with the increasing of BST, the density, the relative complex permittivity and the electronic loss increased, and the relative complex permeability decreased.5. According to the experimental results of material and emulational results of HFSS, the rule that if the material with high permeability and low loss can reduce the size of microstrip antenna and broaden the bandwidth. An microstrip antenna 10mm in length andl2mm in width was designed and manufactured, which used Co2Z with 4.5,12,tg0.048, tg0.537 as the substrate of microstrip antenna. The measured results show that the magnetic material can reduce the size of the microstrip antenna. But the measured resonance frequency was about 2.6GHz, which was different from the emulational results.6. The feasibility of the microstrip antenna with hexaferrite substrate used as adaptive antenna has been observed. With the increasing of permanent magnetic field, the resonance frequency of microstrip antenna with Co2Z substrate moved to higher frequency, which was coincident with N.P.Mahalik[48] conclusion.