Design and Fabrication of a Patch Antenna for 5G Wireless Communications from a Low-Permittivity LiAlSi₂O₆-Based Ceramic

A microwave dielectric ceramic based on lithium aluminum silicate (LiAlSi₂O₆) with ultralow permittivity was synthesized using the traditional solid-state reaction technique, and its dielectric characteristics at microwave frequencies are presented. The nominal LiAlSi₂O₆ ceramic exhibited a relative permittivity of 3.95. To enhance the material properties, LiAlSi₂O₆-<i>x</i> wt % B₂O₃ microwave dielectric ceramics were fabricated by incorporating a low-melting-point sintering aid (B₂O₃), achieving a relative density exceeding 94%. The resultant ceramics exhibited a relative permittivity (ε_r) ranging from 3.95 to 4.42, a microwave quality factor (<i>Q</i> × <i>f</i>) between 24,720 and 28,990 GHz, and a resonant frequency temperature coefficient (τ_f) varying from -45.9 to -20.6 ppm/°C. Additionally, the introduction of B₂O₃ broadened the sintering temperature window and effectively lowered the optimal sintering temperature from 1400 to 1200 °C. Furthermore, LiAlSi₂O₆ ceramics demonstrated a near-zero coefficient of thermal expansion (CTE) of 1.44 ppm/°C, which is advantageous for applications requiring high thermal stability. Based on LiAlSi₂O₆-2.0 wt % B₂O₃ ceramics with ε_r = 4.42, <i>Q</i> × <i>f</i> = 28,990 GHz, and τ_f = -20.6 ppm/°C, a microstrip patch antenna was designed and fabricated. Testing of the antenna revealed exceptional performance, including a center frequency of 4.98 GHz, a bandwidth of 280 MHz (-10 dB), and a total efficiency reaching up to 93.7%. These findings underscore the promising potential of this material in advanced microwave and wireless communication applications.