| 摘要 |
A method of detecting a target signal at a target signal level below the level of clutter in the return signals of a radar receiver. The receiver i.f. signals are correlated by multiplying delayed i.f. signals with undelayed i.f. signals. The correlated signals are filtered and then decomposed into their spectral component frequencies. The spectral components are compared, in turn, with individual thresholds. The individual thresholds are formed by summing the weighted values of selected ones of the spectral components, the selection being such that the spectral component being compared with a threshold is not used in forming that threshold. A target output signal is generated whenever any one of the spectral components exceeds the level of the threshold against which it is compared. In a second embodiment, in-phase and quadrature correlator signals are formed by the use of two correlators and two delay lines having different delay times that provide a 90 degree phase difference. The complex correlated signals are filtered, decomposed into spectral component frequencies and processed as in the first embodiment to generate a target output signal. In both embodiments, decomposition of the correlated signals may be carried out by means of a Discrete Fourier Transform.
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