Microwave dielectric properties of Mg4Ta2O9 ceramics with TiO2 additions for dielectric resonator oscillator

The microwave dielectric properties of the Mg4Ta2O9 electro-ceramics with TiO2 addition were investigated and the dielectric resonator oscillator (DRO) was simulated and manufactured. All specimens were prepared by solid-state reaction method and sintered at 1450 °C. From the XRD patterns, the Mg4Ta2O9 phase was observed in (1 − x)Mg4Ta2O9–xTiO2 ceramics as a main phase. Meanwhile, the MgTi2O5 phase appeared by increasing the amount of TiO2. It was found that MgTi2O5 and TiO2 phases have influence on the microwave dielectric properties of the (1 − x)Mg4Ta2O9–xTiO2 ceramics. The temperature coefficient of resonant frequency (τf) was significantly improved by adding the TiO2 with x = 0.5. However, the Q × fr value decreased from 116,800 GHz of the pure Mg4Ta2O9 ceramics to 102,100 GHz of the TiO2 added one with x = 0.5. The dielectric constant, Q × fr value and τf of (1 − x)Mg4Ta2O9–xTiO2 ceramics sintered at 1450 °C for 10 h were 11.56–22.5, 24,980–186,410 GHz and −49.82 to +19.72 ppm/°C, respectively, depending on the value of x. Advanced Design System (ADS) as an electro-magnetic simulation tool was used for simulation and design for DR and DRO. The estimated EM characteristics of DR with 0.5Mg4Ta2O9–0.5TiO2 ceramics showed the operating frequency of 11.97 GHz and S21 of −35.034 dB. The size of manufactured DRO was 56 mm × 48 mm × 34 mm and the operation frequency was 11.93 GHz. The power output and secondary harmonic of the manufactured DRO were +13.61 dBm and −23.81 dBc at 23.85 GHz, respectively.