| 摘要 |
A radar system 2 contains a radar carrier frequency oscillator 4 for generating a radar carrier signal, a receiver having a mixer 12 for generating Doppler signals, a Doppler filter bank 18 and an alarm circuit 21 comprising a number of Doppler compartments with an alarm threshold level. The radar system 2 is provided with a frequency modulator 30 for modulating the radar carrier signal and each interference signal received by the receiver, as a result of which the bandwidth of the frequency-modulated interference signal exceeds the bandwidth of a number of Doppler filters in the Doppler filter bank 18. The alarm circuit 21 can have two threshold levels and can be controlled in dependence on a predetermined pattern of threshold level crossings. <IMAGE>
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