Cover Pulse (Radar)
Noise Cover Pulse is a method of generating “gated noise” with a “noise like” spectral content.
The goal of this technique is to covering the target’s skin echo with jamming pulses synchronized with the PRF of the victim radar.
The jamming pulses return to the victim system so that the skin is covered by the noise; the width of the disturbing pulse is greater than the width of the radar pulse in order to ensure the total coverage of the skin echo.
The transmission of jamming pulses is programmed with time anticipation and duration with respect the predicted time of arrival of threat pulses.
The spectral content of Noise Cover Pulse can be either Spot Noise jamming or Barrage Noise jamming (Figure 1).
This technique has significant advantages with the respect of continuous noise waveform:
• It can elude the “track-on-jammer” capability, normally used against CW noise (in the pulsed radar receiver the gate to sense the presence of the jamming is positioned at the end of the radar time sweep/time scale, it can find and lock onto the jamming signal only if it is continuous)
• It is a multi-threat technique working in time-sharing
It is a more complex technique as it requires:
• Threat detection, necessary to measure the TOA (Time Of Arrival) of threat pulses
• A circuit to forecast the TOA of the next pulses (TOA predictor), which must be synchronized to the radar PRI, whether fixed or jittered.
The pulse position prediction is programmed against the next pulse with respect to the detected pulse.
This technique is utilised against pulse threats with a predictable PRI.
Jamming carrier can be generated in one of the following ways:
• Through detection and memorization of the threat radar signal (sort of “coherent noise”)
• Through digital synthesis of a carrier at the agility centre frequency of the countered radar track
• Through synthesis of multi band/multi lines spectrum.
Spot Noise is generated through repetition of stored radar signal (the jamming waveform is obtained through the repetition of a stored of the received signalcoherent noise) (Figure 2).
Barrage Noise may use all the different waveform generation modes.
Cover Pulse Noise is generated to mask a range interval around own platform position, and in case of the application on jittered emitters requires Transmitted (TX) duration increase to cover the indeterminacy in the TOA prediction.