A compact-size circularly polarized antenna using low-loss alumina substrates

A compact-size circularly polarized antenna is investigated by employing high-permittivity and low-loss substrate (i.e., high Q × f value) for 2.5-GHz application. The antenna was individually fabricated on nano-Al ₂O₃ (ε_r = 9.7, Q × f value of 500,000 GHz) and Al₂O₃ (ε_r = 9.7, Q × f value of 200,000 GHz) substrates. The high-permittivity and low-loss ceramic substrate (nano-Al₂O₃ substrate) was used to reduce the microstrip antenna dimension on patch size. In addi tion, the ceramic substrate was studied for broadening the 3-dB axial ratio bandwidth [circular polarization (CP) bandwidth]. The obtained CP bandwidth is about 80 MHz (∼3.2%) at 2.5 GHz. The proposed antenna occupies a size of 23.4 × 23.4 × 4 mm³0 and obtains the operation bandwidth of about 90.96 MHz. Good antenna gain and CP radiation patterns have also been observed.