Photonic Generation of Highly-Linear Ultra-Wideband Stepped-Frequency Microwave Signals With Up to 6·106 Time-Bandwidth Product

A photonic-based technique for the generation of highly-linear ultra-wideband stepped-frequency microwave signals with large time-bandwidth product is proposed and experimentally demonstrated. The double-gated recirculating frequency-shifting optical fiber loop enables the frequency of the generated microwave signal to hop step-wisely at exact increment. The generation of signals with up to 20 GHz bandwidth and ∼300 μs temporal duration, corresponding to a time-bandwidth product of 6·10
⁶
, is achieved by the proof-of-concept system with electronics of only up to 80 MHz bandwidth. Nonlinearity of less than 10−
⁷
and high intra- and inter-period coherence are also experimentally validated. This work provides applications such as high resolution radar with a promising low-cost solution for generating large time-bandwidth product waveforms with frequency scalability and extreme linearity.