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Detection Range vs. Detectability Range

detectability range
detection range

Figure 1: Detection range versus detectability range

detectability range
detection range

Figure 1: Detection range versus detectability range

Detection Range vs. Detectability Range

The range at which a radar can detect a target is called the radar's detection range. The range at which a radar's signal can be received and detected by a radar warning or ELINT reconnaissance receiver is called its detectability range. Both of these range values depend on the situation.

The maximum range of a radar is described by the radar range equation. The detection range of a radar depends on its parameters as well as the target's radar cross-section. Sufficient transmission energy is required to overcome free-space path loss on outward and return paths.

However, only the simple One-Way propagation of electromagnetic waves and the Inverse-square law is relevant for the radar warning receiver. This also results in a radar range equation but only for the one outward path:

(1)

  • R1-way = the range from the radar to the EW-receiver
  • Pt = the radar’s transmitter power
  • Pr = the EW-receiver’s minimum detectable power
  • Gt = the radar’s antenna gain
  • Gr = the EW-receiver’s antenna gain
  • λ = the radar transmitter’s wavelength

Since a radar warning receiver is located on the target, it can detect the radar antenna main beam. It may use low-gain antennas and low-sensitivity receivers. An ELINT receiver is typically required to detect radars with all their antenna sidelobes. In this case, the average side lobe gain must be used instead of the maximum antenna gain of the main lobe of the transmitting antenna.

Figure 1 may suggest that the detectability range is twice as large as the radar detection range, but this is not the case. This is because the radar receiver's bandwidth and noise figure is typically adjusted to an optimal level using matched filters. On the other hand, an ELINT receiver must handle wider bandwidths and therefore cannot be as sensitively tuned as a radar receiver.