5G microstrip patch antenna and microwave dielectric properties of 4 mol%LiF-MgO-xwt%MTiO_3 (M = Ca, Sr) composite ceramics

摘要

The combination of low dielectric constant (ε_r) and a high-quality factor (Q × f) in MgO ceramics makes them attractive for 5G applications. However, the large negative temperature coefficient of resonance frequency (τ_f) impedes these applications. In this paper, the composite ceramics of MgO-xMTiO_3 (M = Ca, Sr;x = 0, 2.5, 5, 7.5, 10 wt%) with the addition of 4 mol% LiF as a sintering aid were fabricated by the traditional solid-state reaction method. The coexistence both MgO and MT phases can be observed in XRD and SEM in the 4 mol% LiF-MgO-wt%MTiO_3 systems under the high-temperature sintering process. With the addition of MT, the grain size of MgO decreased, the ε_r value improved with τ_f value gradually increasing from negative to positive value. Optimized microwave dielectric properties were achieved for 4 mol%LiF-MgO-10wt%SrTiO_3 ceramics sintered at 1300 °C for 6 h, yielding ε_r = 11.2, Q × f = 46, 815 GHz, and τ_f = + 3.51 ppm/°C. Based on it, a prototype of microstrip patch antenna was designed and fabricated with a center frequency at 5.64 GHz for 5G-Sub6GHz communication applications.