SAR Antenna Pattern Measurement by Internal Calibration Method for GF-3 Satellite

Abstract

GF-3 is the first C-band multipolarization synthetic aperture radar (SAR) satellite in China. The SAR system is equipped with an active phased array antenna to electronically generate various antenna beams. The accuracy of SAR antenna patterns is of main importance for precise SAR image processing. The traditional method for antenna pattern measurement is the near-field method but it is unable to satisfy the demand for fast measuring in-orbit. In order to measure the SAR antenna pattern quickly with high accuracy, we propose the internal calibration method. The internal calibration uses calibration signals which are routed along the nominal signal path in SAR systems, thus monitoring the gain and phase variations for each T/R channel is possible. This paper will focus on this method, including its principle, operation steps, and results, compared to the near-field method. The internal calibration method provides a valuable solution for SAR antenna pattern measurement.

Practical Noise Model of an Active Electronically Scanning Array

“…To illustrate the applicability of the noise fgure calculation method, consider for example the design of an SAR antenna for a GF-3 satellite. GF-3 is the frst C-band multipolarization SAR satellite in China and successfully launched in 2016 and 2021 [14][15][16][17]. For each polarization, the antenna is made of 768 slot waveguide antennas (24 in azimuth direction and 32 in elevation direction), 192 4channel T/R modules, 96 time delay modules, and combiner networks.…”

Design of non-delayed full link high precision internal calibration scheme for radar system

“…The performance of each device will change with long period of working time, the fluctuation of environment temperature and other factors, which results in changes of the amplitude-frequency and phase-frequency characteristics of the transmitting and receiving links and deterioration of the system performance [1][2] [3]. Therefore, the internal link of the radar system needs to be calibrated periodically to extract the true amplitude and phase parameters [4] [5].…”