SYNTHETIC APERTURE RADAR PAYLOADS: MIGRATION TOWARDS PHOTONIC APPROACH

The application of Photonic Integrated Circuits (PICs) to Telecommunications payloads has already demonstrated several benefits, such as an increase in SNR performance, a significant reduction in power consumption, a GHz-precision RF signal processing capability, fast and large bandwidth for data transfer. Hence, during the last years, it has also tried to spread the photonic approach to the Synthetic Aperture Radar (SAR) subsystems, mainly providing wider bandwidth and larger tunability with respect to microelectronic technologies. This migration could interest several basic SAR building blocks, such as the transmission section, the beamforming networks, the data processing, and the analog-to-digital converters. Here, the design of an innovative photonic SAR payload, with sub-meter spatial resolution (< 90 cm) in stripmap mode and operating in Ka-band (35.75 GHz), is proposed. The breakthroughs pertain to a high-performance linearly chirped waveform generator (with a time-bandwidth product > 103 and a phase noise at 10 kHz from the carrier < -110 dBc/Hz), a Fast-Fourier-Transform (FFT) data processor (operating in real-time (≈ ns), 8-bit resolution, and 300 MHz sampling spacing of the upconverted signal), and an innovative beamforming network configuration (featuring squint-free wide bandwidth of 500 MHz, steering angle of ± 15°, and overall power consumption of ≈ 1 kW).