| Nowadays, as the microwave telecommunication technology is undergoing a rapid development, the portability, light weigh, reliability and low cost of microwave communication devices have become the standard of the new generation communication equipment. It is inevitable that the microwave dielectric ceramics became the most important microwave dielectric materials because of its excellent properties. The microwave dielectric ceramics have a tremendous prospects for development, it could be applied in numerous fields and have been taken much attention by science researchers around the world.As a microwave dielectric ceramics with a relatively low sintering temperature, a low dielectric loss, an adjustable permittivity and relatively low temperature coefficient of resonance frequency, Li2O-Nb2O5-TiO2(LNT) system microwave dielectric ceramics have inevitably become the focus of attention of numerous scholars. LNT system microwave dielectric ceramics could be used in many fields just because it could obtain different permittivities by changing the chemical formulation of LNT ceramics.The article mainly studies on the preparation of two kinds of permittivities of LNT ceramics and its use on the design of the microstrip antenna, the experiment section of the article could be divided into the following three parts:(1). Technology exploration, the optimizing experiment of choosing different ballmilling time would be carried out at the beginning of the experiment, we choose 3, 5, 7, 9 hours as the ball-milling time and decide to choose 1:1:5 as the ratio of the raw materials, deionized water and zirconia balls, the best ball-milling time of five hours of LNT system microwave dielectric ceramic has been obtained by the results of experiment.(2). Ceramics preparation, the different contents of Li in low permittivity LNT ceramic would be carried out at the beginning of the experiment, and then the work on the preparation and the decrease of sintering temperature of the middle permittivity LNT ceramic are carried out in the experiment, though numerous experiment, the excellent microwave dielectric properties have been obtained. To low permittivity LNT ceramic, a dense microstructure with an excellent microwave dielectric properties of = 21.67,tgδ= 9.72×10-5,Q × f = 67576 GHz(f= 6.567 GHz) and τ=-20.833 ppm/℃ could be obtained when cutting down 4 wt. % Li and sintering at 1125℃ for 2 hours. An excellent microwave dielectric properties of =47.49,Q × f = 9606 GHz(f = 4.67GHz) and τ= 49.8 ppm/℃ of middle permittivity LNT ceramic could be obtained when doping 0.5wt.% LBS glass and sintering at 900℃ for 1 hour.(3). Antenna preparation, the article use low permittivity LNT ceramic, which prepared in the early experiment, as the microwave dielectric materials of antenna, and have prepared a microstrip patch antenna with an excellent properties. Double feeding point is used in the antenna to realize the right-handed circular polarization, the center frequency of antenna is 1.2685 GHz, and the antenna mainly use to transmit-receive BeiDou signal, the bandwidth of antenna no less than 20 MHz. Though the simulation results, it could be obtained that the absolute value of the return loss(|S11|) in the bandwidth is greater than 10 d B, the voltage standing wave ratio in the bandwidth is not greater than 1.7623, the axial ratio of antenna is 1.196 dB, the gain in maximum radiation direction is 5.45 dB, so an antenna with excellent microwave properties was obtained. The entity antenna was made according to the results of the antenna simulation, and then an expected properties were obtained by the test results, the gain in maximum radiation direction is 4.688 dB, the center frequency of the entity antenna is 1.2685 GHz, the bandwidth is 23.6 MHz and meet the requirement of the design, the axial ration is 1.235 dB, the voltage standing wave ratio in the bandwidth is not greater than 1.2809, the polarization mode is right-handed circular polarization. |
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