We propose and demonstrate a scheme for improving ranging performance of Frequency-Modulated Continuous-Wave (FMCW) radar, in which the transmitting signal is generated by a Semiconductor Laser (SL) under intensity-modulated optical injection. Previous investigations have demonstrated that, through introducing optical injection, SLs can be driven into period-one (P1) oscillation under suitable injection parameters, and the oscillation frequency depends on the injection strength. As a result, through modulating the intensity of injection light, FMCW can be obtained. In this work, we adopt a triangular Frequency-Modulated (FM) signal with a frequency of 11.579 MHz (period of 86.362 ns) to modulate the injection strength, an original FWCM signal with bandwidth of 2.59 GHz (from 13.59 GHz to 16.18 GHz) is generated. Taking such a signal as the transmitting signal of radar, the relative error is within the range of (17.74 % to 26.36 %) for ranging the targets within 2.600 m. The large relative error is due to poor repeatability of the transmitting signal, which can be characterized by the frequency comb contrast of FMCW signal. In order to generate the promoted FMCW signal with higher repeatability, optical feedback with delayed time of 86.362 ns is further introduced into the SL under intensity-modulated optical injection. Under optimized feedback strength, the comb contrast of promoted FMCW signal can arrive at 32.35 dB. Taking the promoted FMCW signal as the transmitting signal of radar, the relative error for ranging the targets within 2.600 m is decreased into the range of (0.42 % to 4.61 %).
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