High quality of LiMg0.9Zn0.06Ni0.04PO4-TiO2 microwave ceramic and its application for 5G dielectric waveguide bandpass filter

Abstract

A new microwave dielectric composite ceramic (1-x) wt%LiMg0.9Zn0.06Ni0.04PO4-x wt%TiO2 (0 ≤ x ≤ 18 wt%) was synthesized in the low sintering temperature range of 850 °C − 975 °C by the solid-state reaction method. The XRD diffractogram confirmed the coexistence of LiMg0.9Zn0.06Ni0.04PO4 and TiO2, and no second phase was detected. Due to their opposite τf values, the τf values of LiMg0.9Zn0.06Ni0.04PO4 solid solution ceramics were adjusted by adding different volume fractions of TiO2. The composite ceramic with x = 15 wt% sintered at 975 °C shows desirable microwave dielectric properties of εr∼10.30, Q×f ∼ 58,400 GHz (tan δ = 2.093 ×10−4), and τf ∼ + 4.04 ppm/ °C (at ∼12 GHz). Based on the 85 wt% LiMg0.9Zn0.06Ni0.04PO4-15 wt% TiO2 ceramics, a fourth order dielectric waveguide filter filled with composite ceramics is designed and packaged for the RF front-end of the China Mobile 5 G base station. The test results show that the center frequency of the filter is 4.65 GHz, the working bandwidth is 300 MHz, the filter has a good out of band rejection capability, and the insertion loss in band is 0.18 dB. Combined with the filter test data and material performance, the designed dielectric waveguide filter meets the communication requirements of the base station, and the higher Q×f microwave dielectric ceramic material can achieve low insertion loss and excellent frequency selection performance of the filter.