A Novel Low Temperature Cofired-Cordierite Ceramic Substrate-Based Compact Ultra-Wideband Circularly Polarized Array Antenna for C-Band Remote Sensing Application

• Published in: IEEE Open Journal of Antennas and Propagation Vol. 6; no. 3; pp. 715 - 725
• Main Authors: Pramono, Subuh, Sumantyo, Josaphat Tetuko Sri, Ibrahim, Muhammad Hamka, Takahashi, Ayaka, Yoshimoto, Yuki, Kashihara, Hisato, Santosa, Cahya Edi, Gao, Steven, Ito, Koichi
• Format: Journal Article
• Language: English
• Published: IEEE 01.06.2025
• Subjects: Antenna arrays; Antenna measurements; Antennas; C-band; Ceramics; Cordierite ceramic substrate; CP array antenna; CP-SAR; high temperature; LTCC; Scattering; Substrates; Temperature measurement; Thermal expansion; Ultra wideband antennas; UWB
• ISSN: 2637-6431; 2637-6431
• DOI: 10.1109/OJAP.2025.3544279

This research proposes a novel antenna substrate that is realized based on low-temperature co-fired ceramic (LTCC) technology using cordierite ceramic (2MgO 2Al2O<inline-formula> <tex-math notation="LaTeX">{_{{3}}}~5 </tex-math></inline-formula>SiO2). Compared to other existing ceramics, it has an impressive low dielectric constant <inline-formula> <tex-math notation="LaTeX">\rm (\epsilon _{r}) </tex-math></inline-formula> of 4.674 and a loss tangent (tan <inline-formula> <tex-math notation="LaTeX">\delta </tex-math></inline-formula>) of 0.0723 at 5.3 GHz, which makes it ideal for creating an ultra-wideband (UWB) circularly polarized (CP) array antenna. In addition, cordierite ceramic is suitable for high-temperature environments, its coefficient of linear thermal expansion is about <inline-formula> <tex-math notation="LaTeX">1.8\times 10{^{-}6 } </tex-math></inline-formula>/K (40°C- 800°C), and it expands only 0.1% of its room temperature dimensions even in a 1000°C environment. Through a sputtering process, platinum with a melting point of 1768°C and very good oxidation resistance is used as a conductive material on the cordierite ceramic substrate. Based on the measured results, the proposed <inline-formula> <tex-math notation="LaTeX">2\times 2 </tex-math></inline-formula> CP array antennas have an ultrawide impedance bandwidth (IBW) of 1.74 GHz (32.83%), an axial ratio bandwidth (ARBW) of 1.26 GHz (23.77%), and a maximum gain of 12.2 dBic. In the experimental test, the proposed <inline-formula> <tex-math notation="LaTeX">2\times 2 </tex-math></inline-formula> CP antennas are set up as transmitters and receivers in a CP synthetic aperture radar (SAR) system with full polarimetric modes (L-L, L-R, R-L, and R-R) for remote sensing applications. The transceiver <inline-formula> <tex-math notation="LaTeX">2\times 2 </tex-math></inline-formula> CP array antennas have high isolation with an average mutual coupling level of around −65.9 dB. The back projection algorithm is applied to convert the received data into the scattering images and samples the maximum scattering intensities from the scattering images that are presented in scattering matrices. The measured scattering matrices have a similar trend to the theoretical scattering matrices. Based on the heat-exposed measurement, exposure to 500°C of heat on the <inline-formula> <tex-math notation="LaTeX">2\times 2 </tex-math></inline-formula> CP array antennas causes physical change. The antennas expand in size, which leads to a slight shift in the center frequency by 140 MHz. This proves that the proposed <inline-formula> <tex-math notation="LaTeX">2\times 2 </tex-math></inline-formula> CP array antennas perform well in high-temperature conditions.