Photonic generation of microwave signals with tunable frequency

We propose a novel simple photonic approach to generate microwave signals with tunable frequency. The approach is based on beating between two highly chirped pulse-trains with relative time-delay at the photodetector (PD). We derive mathematical expressions to describe the approach and present simulation results to show that, depending on the amount of dispersion introduced in the system, the generated microwave signals can have single or multiple frequencies. Proper management of both dispersion and time-delay in the system also enables us to shift the frequency of the microwave signals to any harmonic order of the pulse laser´s repetition rate which is within the bandwidth of the photodetector used. In addition, the generated microwave signals can either be in the form of a pulse train or quasi-continuous in time.