Chien-Min Cheng

Microwave dielectric characteristics of ZnTa1.7Nb0.3O6 ceramics

ZnTa2O6 ceramic sintered at 1300°C exhibits the microwave dielectric characteristics of dielectric constant er=36.1, quality value Q× f=60180 GHz, temperature coefficient of resonant frequency τf=9.31 ppm/°C, and density d=8.184 g/cm3, and 1200°C-sintered ZnNb2O6 ceramic shows the microwave dielectric characteristics of er=23.9, Q× f=77270 GHz, τf=-58.2 ppm/°C, and d=5.436 g/cm3. An empirical model is used to predict that τf=0 ppm/°C in ZnTa1.72Nb0.28O6. Therefore, ZnTa1.7Nb0.3O6 is adopted as the main composition for developing dielectric resonators with τf values close to 0 ppm/°C, and its sintering and microwave dielectric characteristics are investigated in this study. As the sintering temperature increases, the er, Q× f, and τf values of ZnTa1.7Nb0.3O6 ceramics increase and they saturate in 1300°C-sintered ceramics.

Develop dual-band CPW asymmetric monopole antennas on the Aluminum Oxide substrates

A novel asymmetric unilateral monopole CPW dual-band antenna is screen-printed on the high dielectric Aluminum Oxide ceramic substrate by the screen-printing technique in this letter. Owing to the high dielectric constant ceramic substrate and asymmetric unilateral structure are used, the size of the antenna can be minimized to only 20×10.8 mm2. The proposed antennas reveal near omni-directional radiation patterns, and the optimum measured bandwidth are 11% (at 2.455 GHz) and 11.6% (at 5.425 GHz), the optimum measured return loss are −21.4 dB (at 2.455 GHz) and −19.1 dB (at 5.425 GHz), respectively.