Generation of Frequency-Stepped Signals in Temporal-Frequency Synthetic Dimension with Digital Predistortion

A Frequency-Stepped Signal (FSS) with a large Time-Bandwidth Product (TBWP) is important to achieve long detection range and high range resolution in a radar system. In this paper, we propose a novel approach to the generation of FSS's with digital predistortion that can pre-compensate for the uneven frequency response of a radar frontend for broadband operation. The FSS's are generated by two coupled fiber loops, in which the recirculation of light signals can be controlled to achieve a target distribution within the temporal-frequency synthetic dimension. By controlling the round-trip loss of each recirculation and incorporating acoustic-optical modulators (AOMs) in the fiber loops, the generation of FSS's with predefined envelopes is demonstrated. Our study shows that FSS's with large TBWPs up to 2.82 X 10 ⁵ , tunable central frequencies from 11.6 to 15.2 GHz and predefined triangular and rectangular envelopes can be generated. The proposed waveform generation scheme may find great applications in future radar systems thanks to its high flexibility and large operation bandwidth.