Series-Feed Centre-Feed Shared Aperture Antenna Array to Improve Isolation for X/Ku-Band Airborne Synthetic Aperture Radar Applications

Abstract

Advanced Antennas that can operate in several bands and with multiple polarizations are required for the development of modern synthetic aperture radar (SAR) systems. SAR systems already have their working modes expanded by using dual-band dual-polarized (DBDP) antennas. The shared-aperture design has been used in many configurations to reduce the size of these antennas. This work presents an innovative Dual-band Dual-Polarized Aperture Antenna (DBDP), which operates on a single layer circuit board at X- and Ku-bands. The operating frequency of X band is 9.3 GHz and operating frequency of Ku band is 13.265 GHz. To utilize the common aperture, 5-elements (4-groups) planar array with square microstrip patches are utilized for both Xband and for Ku-band 5-elements (1-group) microstrip patch antenna is used. The proposed design is to enhance the gain and isolation by using series-fed center-fed network. The interelement spacing between two patches is considered <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.7\lambda$</tex> for the ±25° scan range requirements. The impedance matching bandwidth is 147/266 MHz (X/Ku), Return loss is −19/− 22.24 dB (X/Ku) and high isolation is 66.9 dB. The size of the antenna is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$160\ \text{mm}\times 160\ \text{mm} \times 0.8\ \text{mm}$</tex> using RT/Duriod 5880 substrate with permittivity 2.2 and the height is 0.8 mm (31 mil). The Simulations has been done in CST Microwave Studio. This research shows that using a dual-frequency dual-polarization SAR antenna in a single aperture to suit user needs in future SAR aircraft is a viable option.