Development Of Low Dielectric Low Loss LTCC Material And Design Of Array Antenna Based On This Material

Intensive development of wireless communication systems has resulted in an increasing demand for microwave dielectric materials. As more and more devices are applied in high-frequency, low dielectric constant and low loss materials are in urgent need. It is possible to integrate the passive components to a function module by low temperature co-?red ceramic(LTCC) technology. Materials with low sintering temperature(< 950 °C), high quality factor(Q×f) value and low dielectric constant(εr) are necessary for LTCC applications. As one kind of important low εr materials, ZnO-SiO2 ceramic systems with high quality factors have been studied widely in recent years for possible applications in LTCC field.Low melting glass-doping is the main methods to decrease the sintering temperature of LTCC ceramics. However, high content of glass-doping is always necessary for some ceramics with a high sintering temperature, such as Zn2SiO4. This fact certainly leads to a poor microwave dielectric properties and also causes cracks during the soldering process due to the different thermal expansion coefficients between glasses and ceramics, especially when the amount of glass-doping is over 5 wt%。In this work, the mothod of Co-substitution combined with glass-doping was used to decrease the sintering temperature of Zn2SiO4 ceramics to around 900 °C. Firstly, fixed amount of Li2O-B2O3-SiO2-CaO-Al2O3(LBSCA) glass was added to(Zn1-xCox)2SiO4 powders to decrease the sintering temperature around 900 °C. the sample with 0.05 Co substitution presented a compact microstructure with uniform grains and high microwave dielectric propertie. Secondly, the influence of LBSCA addition content on the microstructure and microwave dielectric properties of(Zn0.95Co0.05)2SiO4 were investigated. A dense microstructure with uniform grain size could be obtained with 2 wt% LBSCA and sintered at 900 °C. The specimen also presented high microwave dielectric properties: εr = 6.5, Q×f = 57,000 GHz and τf =-55 ppm/°C. Finally, different amounts of CaTi O3 were doped in the creamic of(Zn0.95Co0.05)2SiO4 + 2 wt% LBSCA in order to adjust the temperature coefficient to around zero. The temperature coefficient was-1.3 ppm/°C with a doping of 5.5 wt% CaTiO3, which met the requirement of LTCC apply.In the end, a 2×2 of circular polarization antenna array was designed based on the creamic of(Zn0.95Co0.05)2SiO4 + 2 wt% LBSCA + 5.5 wt% CaTiO3. Firstly, the technology of “double patch + aperture coupled feeding” were adopted to attain a bandwidth of 2.36 GHz; Secondly, the technology of “the array 90° rotation arrangement + the feed network 90° phase delay” were adopted to attain a 1.33 GHz bandwidth of circular polarization. At last, The antenna printed with silk screen processing on the ceramic dielectric substrate. The testing performance parameters and the simulation curve were similar. So we can determine the research in the materials and antenna design is successful.