Characterization of a fiber-optic direct modulation analog link with chirp radar signals

This paper describes the experimental investigations carried out to evaluate the behaviour of a fiber-optic direct modulation analog link as a substitute of traditional transmission means, like coaxial cables or waveguides, for X-band chirp modulated radar signals. First of all, the link has been completely characterized, and the spurious frequency modulation has been measured in presence of pulsed signals. Afterwards, the link has been inserted in the receiver and transmitter chain of the Selex-Galileo LPI radar SPN-730 in order to perform a characterization of the performance degradation in terms of minimum detectable signal (MDS). The measurements have shown that for compression ratios and pulse widths typically used in a navigation/surveillance radar like SPN-730 the added frequency modulation does not affect significantly the performance of the system.