USAFA DFEC

ECE 495 — Electromagnetic Warfare and Survivability

Block 4: Aircraft Survivability and Mission Planning
Lesson 36: SEAD, Maneuvers, and Standoff Jamming
Juan Jurado, Col, USAF, Ph.D.
Permanent Professor and Head
Electrical and Computer Engineering
Fall 2026
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Block 4 · Lesson 36 · Where We Left Off

Where We Left Off

L35 found the pop-up threat. Block 2 already handed you the jammer: L17's J/S, and the range where the radar burns through.

L17's jammer rode on the target it protected. The Final Project's jammer never enters a ring — the bomber flies in without it.

Today, the support package: silence the radar, slip its Doppler filter, or jam it from outside the ring.

Block 4 · Lesson 36 · Objectives

Lesson Objectives

By the end of this lesson, you will be able to:

  • Distinguish SEAD suppression from destruction, and read a timing window
  • Explain the beam/notch maneuver through L5's Doppler notch
  • Compute standoff J/S and burn-through, mainlobe and sidelobe
  • Place an SOJ and a strike route for deconfliction
A standoff jammer protects a corridor, not a sky — fly in its shadow.

Block 4 · Lesson 36 · SEAD

SEAD: Destroy the Site, or Suppress It

Suppression of enemy air defenses: neutralize, destroy, or temporarily degrade them.

Destruction · lethal
  • Anti-radiation missiles (HARM) home on the emission of the radar they kill
  • Weapons on a site L14-style geolocation has found
  • The site is gone for the rest of the mission
Suppression · temporary
  • Non-lethal EA: noise jamming degrades the radar — L17's, and today's standoff jammer
  • A HARM in the air makes operators shut down — the site is silent, not destroyed
  • It lasts only while it is applied
Ball's threat suppression (L31): a radar that cannot radiate cannot run the chain — every link at once.

Block 4 · Lesson 36 · SEAD

Suppression Is a Window, Not a Switch

  • The window opens when the suppressor arrives and closes when it leaves
  • The package must cross the site's lethal zone while the window is open
  • A longer path through the zone needs a longer window: timing couples SEAD to the route
Final Project: one site may be suppressed — its hazard $\lambda$ scaled by a stated factor.

Block 4 · Lesson 36 · Maneuvers

Beam the Radar: Hide in the Doppler Notch

Doppler, from L5
$$f_d = \frac{2 v_r}{\lambda}, \qquad v_r = v \cos\alpha$$
  • Fly perpendicular to the line of sight: $v_r \to 0$, so $f_d \to 0$
  • The echo lands in the MTI notch with the ground clutter — and is canceled with it
  • The notch is narrow: hold the beam heading, or reappear

What does beam aspect cost you on the B-21's X-band pattern from Project 3?

Block 4 · Lesson 36 · Maneuvers

Turn Cold, Drag — and the Endgame

  • Turn cold: put your tail on the site; the missile must chase, and its flight time runs out
  • It works only outside the LEZ (L32) — inside it, the missile catches a target running away
  • Drag: hold the cold heading to spend the missile's energy, then come back hot
  • The endgame belongs to expendables: chaff against RF seekers (L18), flares against IR (L24)
Every maneuver pays in something — exposure time, aspect, or distance off the planned route.

Block 4 · Lesson 36 · Part Two

Jamming From Outside the Ring

L17's jammer shared the target's range. A standoff jammer keeps its own range, and reaches the radar through whatever gain the radar points at it — so geometry, not only power, decides what it protects.

Block 4 · Lesson 36 · Standoff Geometry

Self-Protect to Standoff: Two Ranges, Two Gains

  • SPJ (L17): one shared range $R$, so $J/S \propto R^2$
  • SOJ: its $R_j$ stays fixed while the target's $R_t$ closes
  • The radar hears the jammer through $G_r'$ — the gain it points at the jammer, not at the target
  • Mainlobe only when the SOJ sits on the target's azimuth; otherwise a sidelobe

Block 4 · Lesson 36 · Standoff J/S

Standoff J/S: L17's Scorecard, Two Ranges Apart

Standoff jam-to-signal ratio
$$\frac{J}{S} = \frac{4\pi\,P_j G_j\,R_t^{4}}{P_t G_t\,\sigma\,R_j^{2}}\cdot\frac{G_r'}{G_r}\cdot\frac{B_r}{B_j}$$
  • $R_t^4$ is the echo's two-way loss; $R_j^2$ is the jammer's one-way loss
  • $G_r'/G_r = 1$ (0 dB) in the mainlobe; the sidelobe level, −25 to −35 dB, elsewhere
  • Two different beams: the radar's receive lobes ($G_r'/G_r$) set where the strobe falls; the jammer's transmit beam ($G_j$) sets which radar is jammed at all
  • Set $R_j = R_t$ and $G_r' = G_r$: it is L17's self-protect equation
A −30 dB sidelobe takes 30 dB off the jammer — a thousandfold power penalty, set by geometry alone.

Block 4 · Lesson 36 · Burn-Through

Standoff Burn-Through

Where J/S falls to the radar's tolerance
$$R_{bt} = \left[\frac{10\,P_t G_t\,\sigma\,R_j^{2}\,B_j}{4\pi\,P_j G_j\,(G_r'/G_r)\,B_r}\right]^{1/4}$$
  • Threshold $J/S = 10$ (+10 dB): the pulse-Doppler tolerance from L17
  • Solve for $R_t$: a fourth root, because only the echo is two-way
  • Inside $R_{bt}$ the radar sees the target through the noise

One radar, one SOJ — two burn-through ranges. Which azimuth gets which?

Block 4 · Lesson 36 · Quick Exercise

Quick Exercise / Type-along: Mainlobe Versus Sidelobes

Type this with me — one radar, one SOJ, five ways in.

% L36 -- SOJ burn-through: mainlobe versus sidelobes
PtGt  = 10^(87/10);      % radar ERP: 87 dBW
PjGj  = 10^(45/10);      % SOJ ERP toward the radar: 45 dBW
sigma = 0.5;             % target RCS, m^2
Rj    = 120e3;           % SOJ range to the radar, m
BrBj  = 0.2;             % radar BW over jammer BW
SLL   = [0 -20 -25 -30 -35];   % G_r'/G_r in dB (0 = mainlobe)
g     = 10.^(SLL/10);
Rbt   = (10*PtGt*sigma*Rj^2 ./ (4*pi*PjGj*g*BrBj)).^(1/4);
fprintf('G_r''/G_r(dB)   R_bt(km)\n');
fprintf('%12.0f %10.1f\n', [SLL; Rbt/1e3]);
fprintf('sidelobe/mainlobe at -30 dB: x%.2f\n', Rbt(4)/Rbt(1));

Every 5 dB of sidelobe moves $R_{bt}$ by the same factor. What factor — and why a fourth root?

Then: the SOJ backs off from 120 to 480 km. What happens to every row?

Block 4 · Lesson 36 · Quick Problem

Quick Problem: Sidelobe or Strobe

An SOJ covers a strike package against a SAM acquisition radar. The package is off the jammer's azimuth.

  • Radar ERP $P_t G_t = 76$ dBW
  • SOJ ERP $P_j G_j = 40$ dBW, spot ($B_j = B_r$)
  • Target $\sigma = 1$ m², at $R_t = 40$ km
  • SOJ range $R_j = 80$ km
  • The jam enters through a −32 dB sidelobe
  • Radar holds track up to $J/S = +10$ dB
  1. (a) $J/S$ in dB at 40 km.
  2. (b) The sidelobe burn-through range.
  3. (c) The package turns onto the radar–jammer line, into the strobe: the new burn-through range.
(a) $J/S = +29.0$ dB  ·  (b) $R_{bt} = 13.4$ km  ·  (c) $R_{bt} = 2.1$ km

Block 4 · Lesson 36 · The Jammed Contour

One Radar, Two Burn-Through Ranges

Today's demo radar and SOJ, 150 km out. Off the jammer's azimuth: a −30 dB sidelobe.

J/S (dB)
target range (km)
sidelobe · 48.8 km

Now fly the SOJ's azimuth: the jam comes in through the mainlobe. Where does the dot go?

Block 4 · Lesson 36 · The Jammed Contour

One Radar, Two Burn-Through Ranges

On the jammer's azimuth the jam enters through the mainlobe — 30 dB more J/S at every range:

J/S (dB)
target range (km)
mainlobe · 8.7 km

Same jammer, same power: 30 dB of geometry moves burn-through by $10^{30/40} = 5.6\times$ — from 48.8 to 8.7 km.

Block 4 · Lesson 36 · The Jammed Contour

The Jammed Contour: a Strobe, Not a Sky

Jammed detection contour
$$R(\phi) = \min\big(R_{det},\ R_{bt}(\phi)\big)$$
  • Within $\theta_B/2$ of the jammer's azimuth: the strobe, a deep, narrow notch
  • Elsewhere: a shrunken sidelobe contour
  • The protected corridor is the strobe between the two $R_{bt}$ — about $R\,\theta_B$ wide

To scale: the demo's defaults, 5° beamwidth. On the radar's scope the same wedge is the jamming strobe — a bright line pointing at the jammer.

Block 4 · Lesson 36 · The Jammed Contour

Two Scalings Every SOJ Planner Uses

Standoff range
$$R_{bt} \propto R_j^{1/2}$$
Four times the standoff only doubles burn-through: backing off is cheap.
Sidelobe level
$$R_{bt} \propto \left(G_r'/G_r\right)^{-1/4}$$
Every 10 dB of sidelobe is a factor of 1.78 in range; 30 dB is 5.6.
EP strikes back (L15): cancelers and blankers attack the sidelobe path. The mainlobe is the one door they cannot close — which is why the mainlobe position is prized.

Today's Interactive Demo: Standoff Jamming

Companion script: L36_StandoffJamming.m
Live demo

Standoff Jamming

usafa-ece.github.io/ece-495-ew

Block 4 · Lesson 36 · Deconfliction

Deconfliction: Four Rules for One Jammer

1
The SOJ orbits outside every MEZ, plus a margin — it radiates, so it is a target
$d_{\text{SOJ, site}} \ge R_{\text{MEZ}} + \Delta$
2
One jammer beam, one victim: its transmit mainlobe holds one radar; the others are unjammed
$P_jG_j \rightarrow$ the victim only
3
The route rides the victim's strobe — a lane that points at the jammer from the victim's position
$\left|\phi_{\text{route}} - \phi_j\right| \le \theta_B/2$
4
The other sites' zones: cross them inside the SEAD window, or route around them entirely
$t_{\text{in}},\ t_{\text{out}} \in \left[t_{\text{open}},\ t_{\text{close}}\right]$

Rule 2 is the Final Project's stated simplification. In the demo's Two radars preset, move the jammer's beam and watch the cover move with it.

Block 4 · Lesson 36 · Final Project

Final Project T5: Your Support Package

  • Place one SOJ outside every MEZ, plus the handout's margin, and choose its victim radar
  • The victim's contour becomes $\min(R_{det}, R_{bt}(\phi))$ — its lethal zone shrinks, and so does your $\ell_i$
  • Nominate one site for SEAD: its hazard $\lambda_i$ scales by the stated factor
  • Re-plan, report $\Delta P_S$, and test its sensitivity to one parameter you choose
The support package adds no link to the chain: it changes how many kilometers each site gets to shoot.

Block 4 · Lesson 36 · Wrap-Up

Wrap-Up

Key ideas
  • SEAD: destruction removes a site; suppression holds only while applied — a window
  • Beam/notch: $v_r \to 0$ puts your echo in the MTI notch (L5)
  • Standoff J/S $\propto R_t^4 / R_j^2$ — the radar's gain toward the jammer decides mainlobe or sidelobe
  • An SOJ protects a corridor — its strobe — not the whole sky
Next lesson
  • L37: Modern Trends in EW — cognitive EW, ML emitter ID, GPS denial, space EW
  • Work the L37 pre-flight before class
  • Final Project: add T5, the support package