Demo — Jammer / J/S Explorer

Demo — Jammer / J/S Explorer#

A self-protect jammer’s advantage is not constant — it depends on range, and it works against the jammer as the target closes. This demo plots the jam-to-signal ratio against range, marks the burn-through point where the radar wins, and shows how stealth shifts that point.

The ratio#

\[ \frac{J}{S} = \frac{4\pi\,P_j G_j\,R^2}{P_t G_t\,\sigma}. \]

The jammer reaches the radar one-way (\(\propto 1/R^2\)) while the skin echo is two-way (\(\propto 1/R^4\)), so \(J/S \propto R^2\) — large far out, shrinking as the target closes.

Interactive demo#

Open in full screen

Walkthrough#

  1. Read the curve. \(J/S\) in dB rises with range. The red line is the radar’s tolerable threshold; where the curve crosses it is the burn-through range \(R_\text{bt}\).

  2. Slide the range cursor. Beyond \(R_\text{bt}\) the jammer buries the return; inside it the radar has burned through and holds the track. Watch the verdict flip.

  3. Cut the RCS. Lower \(\sigma\) and the whole curve lifts — \(J/S\) improves everywhere — and \(R_\text{bt}\) moves inward. Stealth forces the radar to get closer before it can burn through.

  4. Trade jammer power. Raise \(P_j G_j\) and push \(R_\text{bt}\) further in; the geometry and the power budget both move the same marker.

Key observations#

  • \(J/S \propto R^2\): the jammer wins far out, the radar burns through close in — the same one-way/two-way asymmetry from L11, now working for the defender of the track.

  • Stealth and jamming compound. Lower RCS raises \(J/S\) and pulls burn-through inward, so LO and EA reinforce each other.

  • Burn-through is inevitable at some range for a fixed jammer — which is why deception (L18) attacks the measurement instead of the power budget.

Source#

MATLAB · code/L17_JtoSBurnThrough.m↓

The in-class script computes \(J/S\) versus range for a self-protect jammer, finds the burn-through range, and shows how lowering RCS pulls it inward.

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