Reconfigurable broadband linear frequency-modulated (LFM) signals are essential for modern radar systems to achieve high-resolution target detection and reliable operation in complex electromagnetic environments. Existing photonic approaches encounter significant limitations: conventional electronic methods (high-speed AWGs, ≥256 GSa/s) face difficulties balancing >10 GHz bandwidth with real-time parameter tuning, while photonic techniques such as spectral stitching or photon-assisted frequency multiplication necessitate hardware reconfiguration, restricting software-defined adaptability. Current solutions typically depend on expensive ultra-high-speed electronics or complex optical components, impeding practical implementation. Modern applications—including cognitive radar for dynamic spectrum sharing, adaptive electronic warfare for anti-jamming, and joint spectrum sensing—require agile waveform control across bandwidth, center frequency, and time-frequency patterns, which current methods cannot adequately provide. This study introduces a novel optical LFM generation scheme utilizing fiber nonlinearity and low-speed AWGs (≤10 GSa/s). Through self-phase modulation (SPM) in highly nonlinear fibers (HNLFs), broadband signal processing transitions to the optical domain, enabling software-defined dynamic adjustment of key parameters—bandwidth (4?8 GHz), center frequency (20?30 GHz), and waveform duration—through basic electrical signal modifications. This research presents a cost-effective, simplified hardware solution bridging photonic processing and electronic stability. It enables next-generation radar systems with real-time reconfigurability, suitable for civilian-military integrated applications including 5G/6G beamforming, autonomous vehicle perception, and intelligent electronic countermeasures.

The proposed system comprises two optical paths (Fig. 1). In the upper path, a low-speed AWG generates electrical shaping signals to intensity-modulate an optical carrier via a dual-drive Mach-Zehnder modulator (DD-MZM). The modulated optical signal is amplified and fed into a highly nonlinear fiber (HNLF) for spectral broadening via SPM. The lower path employs a dual-parallel MZM (DP-MZM) to generate a frequency-shifted optical carrier. The spectrally broadened signal and the shifted carrier are then heterodyned at a photodetector to produce the LFM waveform. Key parameters—bandwidth, center frequency, and duration—are controlled by adjusting the AWG’s driving signal, peak optical power, and frequency shift. Simulations in MATLAB and OptiSystem validate the scheme’s performance under varying conditions (Table 2).

Simulations demonstrate that a 10 GSa/s AWG produces an 8 GHz bandwidth LFM signal centered at 30 GHz with high linearity [Fig. 4(f)]. Lower sampling rates (1 GSa/s) reduce frequency linearity [Fig. 4(c)], while higher rates (20 GSa/s) provide no substantial improvement [Fig. 4(i)]. Modifying the peak optical power (1?2 W) or AWG signal period (5?10 ns) enables bandwidth tuning from 4 GHz to 8 GHz [Figs. 5(c)?(f)]. Adjusting the frequency shift modifies the center frequency [20 GHz to 30 GHz, Fig. 5(a)]. Through specialized electrical driving signals, the system generates LFM waveforms with time-frequency diagrams representing arabic numerals 1?5 [Fig. 6(d)]. This illustrates the system’s capability for arbitrary waveform design, essential for adaptive radar and electronic warfare applications.

This study presents a highly reconfigurable LFM signal generation scheme based on optical nonlinear effects. By exploiting SPM in HNLF and low-speed AWGs, the method achieves continuous control over bandwidth (4?8 GHz), center frequency (20?30 GHz), and waveform envelope without hardware reconfiguration. Key advantages include reduced reliance on high-speed electronics, software-defined flexibility, and compatibility with mainstream radar frequency bands. The scheme offers a cost-effective solution for software-defined radar systems, cognitive electronic warfare, and adaptive spectrum sensing, bridging the gap between photonic processing and electronic stability. Future work will focus on experimental validation and extending the bandwidth beyond 10 GHz.