Vertical Polarized 1 × 3 Series-Fed Linear Array with Gain and Front-to-Back Ratio Enhancement for Airborne SAR-X Applications

Abstract

In this paper, a gain and front-to-back ratio (FTBR) enhanced vertically polarized 1 × 3 series-fed linear array for Airborne Synthetic Aperture Radar-X-band applications has been presented. The proposed antenna prototype is designed at 9.65 GHz (X-band). The design consists of a square radiating patch, substrate, quarter wave transformer, 50 Ω matched transformer, and series feed line (SFL). The simulated antenna prototype is fabricated and successfully measured. The final antenna prototype has a dimension 3.256 × 2.035 × 0.0645λg (Guided wavelength) at 9.65 GHz. The results indicate that the proposed antenna prototype yields an impedance bandwidth > 140 MHz (from 9.591 to 9.712 GHz) defined by S11 < −10 dB. The low profile/cost antenna prototype has a fully directional radiation pattern with measured gain up to 12.2 dBi and estimated radiation efficiency of 89%, respectively. A brass plate with 0.8 mm thickness has been fabricated to attach to the antenna ground plane for improving FTBR of more than 30 dB. All these features make the proposed antenna array have good potential applications in X-band system, especially in 9.65 GHz Airborne SAR systems. The aperture of the antenna is 80mm × 50 mm, which equals 31 wavelengths at 9.65 GHz.