Photonic generation of frequency agile LFM signals for ISAC systems

A compact photonic method to generate frequency agile linearly frequency modulated (LFM) signals is proposed demonstrated by experiment and simulation. A Mach–Zehnder modulator driven by an LFM waveform train and an electrical controlled optical tunable delay line driven by a coding sequence is employed. According to time–frequency linear relationship of LFM signals, the initial frequency of the generated signals can be shifted by adjusting the introduced time delay. Experiments are carried out to verify the feasibility of the proposed generator. Frequency agile LFM signals under 2FSK and 4FSK modulation with symbol rate of 4 and 8 Msps are successfully obtained. 0.15 m range resolution and 4 Mbps communication data rate are achieved with a 1–1.5 GHz driving LFM signal. This scheme features compact structure and excellent tunability, which are promising to find applications in anti-jamming ISAC systems.