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Remote Imaging Radar with Ultra-Wideband Chaotic Signals Over Fiber Links

We experimentally demonstrate radar remote imaging using a radio technique based on ultra-wideband chaotic signals over fiber links. The radar system includes three parts, i.e. a central station, some optical fiber links and a base station. At the central station, an ultra-wideband chaotic signal is generated from an improved Colpitts oscillator and then is up-converted as a probe signal. The probe signal is then converted to be in optical domain by the external modulation technique on laser diode for transmitting over a fiber link to a remote base station. At the base station, the probe signal is converted to be in electrical domain and then launched by a microwave antenna. After being received by another antenna, the echo signal from a target is converted to be in optical domain and then transmitted over a fiber link back to the central station. By optical-to-electrical conversion and down conversion, the echo chaotic signal is recovered. Utilizing the correlation method and back projection algorithm, an image of the target in the two-dimensional space can be realized at the central station. Our experiments successfully performed remote imaging for both planar and spherical reflectors with a distance over 10 km. The down-range resolution of 6-cm and 8-cm cross-range resolution were obtained, respectively. We will show that the power spectrum of the probe signal is adjustable in the spectral mask according to the Federal Communications Commission standards, therefore can avoid interference to the existing narrowband radio signals.