Multiband LFM waveform generation and band-selection using stimulated Brillouin scattering

Abstract

Modern radar systems are designed to simultaneously serve multiple applications such as ranging, surveillance, imaging, or warfare, which necessitates operation at multiple carrier frequencies. Linear frequency modulated (LFM) signals are inherently capable of pulse compression leading to enhanced range resolution and good signal-to-noise ratios; therefore, they are widely employed in various radar applications. In this paper, a photonic-based generation scheme for carrier frequency multiplication of LFM waveforms up to a factor of four through a single dual-drive Mach–Zehnder modulator is proposed and experimentally demonstrated. The technique is employed to produce multiband LFM having wide-bandwidth chirps (500 MHz, 1 GHz) as well as narrow bandwidth chirps (10, 20 MHz) that are compatible with the intrinsic linewidth of stimulated Brillouin scattering (SBS). The frequency bands of the narrow bandwidth chirps are further selected through a frequency-agile Brillouin RF filter. The generated tupled chirped waveforms are at continuous multiples of the RF carrier frequency at 2, 4, 6, and 8 GHz, respectively, with the first three multiples having 10 MHz and the fourth multiple having 20 MHz chirp bandwidth. This scheme is also experimentally verified for generating different tupled products and respective filtering through SBS at multiples of 4 GHz up to 16 GHz, thereby verifying the system’s agility and flexibility.