Enlarged Range and Filter-Tuned Reception in Photonic Time-Stretched Microwave Radar

Abstract

We have previously demonstrated a photonic time-stretched coherent radar (PTS-CR) with central-frequency programmable and bandwidth-tailorable agility. The sampling bandwidth in the reception was essentially compressed by the photonic time-stretched process. However, in the PTS-CR, the reception aperture suffering dead zone was hardly tuned by the fiber delay line and the measurement range was restricted by the pulse repetition rate (PRR) of the mode-locked laser. Here, we report a novel scheme to overcome the restrictions. The reception aperture can be simply tuned by adjusting the center wavelength of an optical filter and the PRR is reduced for enlargement of the measurement range by use of a photonic switch in the transmitter. In the experiment, a tenfold enlargement of measurement range is demonstrated to identify two neighboring targets separated by ~4 cm.