| 摘要 |
A method for interferometric radar measurements that provides prearranging, at a target observed by the radar, of a transponder that is adapted to perform a frequency shift fd of a radar signal received by the target, and to retransmit a response signal towards the radar. The frequency-shift is such that the signal (21), as received by the radar, can be separated from clutter (19) coming from the radar scenario, by a demodulation step (A), in particular a coherent demodulation step, and a phase extraction step (B), which may comprise a further demodulation step by a phasor that has a frequency equal to fd. If these steps are carried out subsequently, it is possible to calculate the phase difference with respect to signals 22 and then measuring the displacement that target (2) carries out between such instants. In case of a plurality of targets in a same radar scenario, the use of a corresponding plurality of transponders with specific frequency-shifts allows separately demodulating the signals coming from each transponder. In case of variable frequency radar signals, in particular if the frequency is increased according to a predetermined pitch, i.e. a frequency step, the phase extracting step may provide sampling sequences of values of the response signal coming from respective resolution cells of the radar scenario, and applying the inverse discrete Fourier transform to such sequences, in order to display the target in a resolution cell that is located between a maximum distance available by the radar and the limit of range unambiguous. The method allows overcoming well-known prior art interferometric radar systems drawbacks, since it eliminates clutter, and allows resolving more target in a same radar scenario, or in a same resolution cell.
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