A new signal processing technique for ISAR ranging: The Vernier ranging method

A new technique for inversed synthetic aperture radar (ISAR) ranging, which resembles the principle of the Vernier measuring system, is presented in t his paper In this technique, the transmitted ISAR pulse comprises a train o f chirp subpulses with uniformly stepped up center frequencies. The return ISAR echo is first processed, using hardware, to determine a coarse estimat e of the target range. Further refinements of the range estimate are achiev ed through software processing, consisting of two stages of discrete Fourie r transform operation. The ranging accuracy can be increased without the ne ed for increased bandwidth, but at the expense of a slight increase in comp utational complexity. Numerical evaluation shows that a noiseless system is capable of achieving high-ranging accuracy, of the order of millimeters, e ven in the presence of dispersion and target motion. From computer simulati ons, the proposed system is also found to be robust against additive system noise and frequency jitter under practical conditions.