MPRF waveform for ground based radars to suppress returns from windmills and rain clutter

Renewable energy sources such as wind parks are more and more shaping our environment. In the vicinity of radars, however, they often pose a serious problem, due to degradation of radar performance. This paper deals with a new MPRF waveform capable of suppressing returns from wind parks and strong rain clutter and thus mitigating this performance degradation. Most ground based radars use low PRF (LPRF) waveforms with pulse repetition frequencies (PRF) below ~1000Hz, allowing unambiguous range measurements out to more than 150km. The advantage of this waveform for ground based radars is that, assuming a duty ratio of approx. 10%, the near-in ground clutter less than 15km from the radar falls into the eclipsed transmit blind zones. A further advantage is the large unambiguous range measurement interval and the possibility of using Sensitivity-Time Control (STC) to suppress low radar cross section returns. A disadvantage of LPRF is the small unambiguous Doppler velocity interval which, e.g., for S-band radars, is less than ~50m/s. In the case of windmill farms, it is possible that, due to the maximum velocity of the rotor tips of ~50m/s the whole Doppler velocity region for the affected range intervals is occupied by rotor blade returns. Also, in the case of heavy rain, the whole Doppler region over a range interval of several miles could be occupied by rain clutter. This paper presents a MPRF waveform which can mitigate the effects of windmills and rain clutter on the detectability of true targets.