Spectral Sculpting of Chaotic-UWB Signals Using a Dual-Loop Optoelectronic Oscillator

A dual-loop nonlinear optoelectronic oscillator with an inbuilt ultra-wideband (UWB) band pass filter is proposed to generate chaotic-UWB signals for the first time. To avoid the spectrum-overlay-induced interference between UWB signals and the other existing narrow band signals, a microwave photonics filter is built up in the loops to filter out the corresponding frequency components. In the experiment, the chaotic-UWB signals with a frequency notch response located at 7.5 GHz, 5 GHz, or simultaneous 7.5 and 5 GHz are generated as the time delay difference between the two loops is set at 133, 200, or 400 ps, respectively. The peak sidelobe levels of the autocorrelation traces are as low as -33.7 dB at least, which implies that the generated UWB signals could be applied in random UWB radar directly.