Low-temperature Co-fired Zn₂SiO₄ Low-loss Microwave Materials And Antenna Array Design Research

In recent years,electronic information technologies are rapidly developing towards high speed,large capacity,and intelligence aspects,especially the development of new products related to stations and mobile phones that require 5G communication,have accelerated the integration of microwave devices to large-scale integration,high speed,ultra-low loss,and multi-functionalization.Antenna,as the main component of 5G stations and mobile phones,plays a very important role in it.The research of high-quality antenna materials（substrate dielectric ceramics）has provided choices for the ultra-low loss microwave dielectric materials,putting forward the development of low temperature co-fired ceramic technology（LTCC）.This thesis develops a new type of microwave material based on Zn₂SiO₄ dielectric ceramics to meet the technical requirements of the LTCC process and 5G devices.In this thesis,we first studied the development of(Zn_1-x-x Mg_x)₂SiO₄ dielectric ceramics.The results showed the Mg²⁺substitution x was 0.4,and the optimal sintering temperature was set to 1250℃in order to obtain the best microscopic growth appearance and dielectric properties.The measured?_r is 6.097,and the Q×f value is 129991 GHz.Next,we studied the properties of the composite microwave dielectric ceramics influenced by doping Co²⁺.The results showed the dielectric properties of the composites were further optimized when the substitution of Co²⁺was 0.05 and the sintering temperature was 1250℃.The measured?_r is 6.125 and the Q×f value is 131056 GHz.We further studied the adjustment of the temperature coefficient of composite microwave dielectric ceramics by adding CaTiO₃ with the opposite sign temperature coefficient comparing to the raw ceramics.The test showed when the molar ratio of the added CaTiO₃was 0.12,the temperature coefficient of the material was closest to 0 ppm/℃,which basically met the design requirements.Finally,we added LiF and V₂O₅ composite sintering aids with a mass fraction of 2.5wt%to reduce the sintering temperature,resulting in the results that the composite dielectric ceramics can be sintered at 950℃and excellent microwave dielectric properties were obtained:?_r=7.236,the Q×f value is29845 GHz,and the temperature coefficientτ_f=1.13 ppm/℃.In order to compare the differences in dielectric properties between different types of silicates,an additional set of experiments is carried out in this thesis to develop Li₂Zn_1-xMg_xSiO₄+2.5wt%BBSZ ceramics.The tested Mg²⁺substitution x is 0.15,and when CaTiO₃ is not added,the Q×f value is only 10354 GHz.Compared with[(Zn_0.6Mg_0.4)_0.95Co_0.05]₂SiO₄,the latter is selected as the base material of the antenna studied in this thesis.Using the 0.88[(Zn_0.6Mg_0.4)_0.95Co_0.05]₂SiO₄+0.12CaTiO₃+2.5wt%（LiF+V₂O₅）developed above as a low dielectric and low loss material,a circle polarized 2×2microstrip array antenna with a center frequency of 10GHz was designed and optimized.The influence of rectangular patch cut corners,feed point position,and different dielectric material parameters on antenna performance were studied.We used a double-layer adjustable dielectric constant dielectric layer material to extend the bandwidth,and the antenna unit was improved by adding lower-layer patches and bottom feed.The simulation showed the parameters are better than the target metrics.Finally,the array of2×2 antenna elements is prepared for the designed antenna.After debugging,except for the center frequency shifting to the right and the return loss being too large,the remaining parameters basically meet the antenna design requirements,that is,the center frequency is 10 GHz±0.2 GHz,the in-band gain reaches 10 dBm-15 dBm.