ECE 495 — Electromagnetic Warfare and Survivability

Block 2: RF Electronic Warfare
Lesson 11: From Radar to EW

Juan Jurado, Col, USAF, Ph.D.
Permanent Professor and Head
Electrical and Computer Engineering
Fall 2026

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Block 2 · Lesson 11 · Where We Left Off

Where We Left Off

Block 1 put you in the threat's seat: you can now compute exactly how an IADS sees the B-21, aspect by aspect, band by band.

Block 2 flips the seat. Same physics, opposite agenda.

Today

What EW actually is, the three pillars in doctrine terms, the asymmetry the whole discipline rests on, and where B2 goes from here.

Block 2 · Lesson 11 · Objectives

Lesson Objectives

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

Map each term of the radar range equation to the EW lever that attacks it
State the roles of ES, EP, and EA with doctrinally correct examples
Explain the one-way vs two-way detection asymmetry and why it favors the listener
Navigate the Block 2 roadmap from ES through EA to Project 2

Block 2 · Lesson 11 · Part One

The Target List

You spent Block 1 learning to evaluate one equation. Read it again as an operator and every symbol in it turns into something one side pays to protect and the other pays to exploit.

Block 2 · Lesson 11 · The Target List

The Range Equation Is a Target List

Maximum detection range

\[ R_{\max} = \left[\frac{P_t \, G_t \, G_r \, \lambda^{2} \, \sigma}{(4\pi)^{3} \, S_{\min}}\right]^{1/4} \]

Every factor is something we can attack or defend.

Block 2 · Lesson 11 · The Target List

The Range Equation Is a Target List

Maximum detection range

\[ R_{\max} = \left[\frac{P_t \, G_t \, G_r \, \lambda^{2} \, \sigma}{(4\pi)^{3} \, S_{\min}}\right]^{1/4} \]

Term	Pillar	The EW lever
$\sigma$	EP	Shrink it by design: LO shaping and RAM
$S_{\min}$	EA	Raise their effective noise floor: jamming
$G_t, G_r$	EA	Enter through the side lobes they can't help having
$P_t$, $\lambda$, PRF	ES	Every emission leaks intent: collect it

B1 taught you the equation. B2 teaches you to fight it.

Block 2 · Lesson 11 · Part Two

The Three Pillars

You met ES, EP and EA in L1 as three words. Here each one gets its working definition, its hardware, and the term of the range equation it reaches for.

Block 2 · Lesson 11 · Electromagnetic Support

Electromagnetic Support (ES)

Situational awareness EW

Sense the spectrum to support targeting, warning, and intelligence.

On-board: radar warning receivers (RWR), EO/IR warning sensors
Off-board: SIGINT / ELINT / COMINT national assets
Exploits the threat's one unavoidable weakness: a radar must radiate to work
Feeds everything else — EA needs cueing, routes need threat locations

Legacy term: ESM. Modern Joint term: Electromagnetic Support.

Block 2 · Lesson 11 · Electromagnetic Protect

Electromagnetic Protect (EP)

Defensive EW

Protect our own use of the spectrum, against both enemy attack and friendly interference.

LPI waveforms — spread the energy so the listener's job gets hard
Agility — frequency and polarization hopping outrun the jammer's set-on
Side-lobe cancellation — close the back doors into the receiver
Hardening and LO — survive the disturbance, deny the detection

Legacy term: ECCM. Modern Joint term: Electromagnetic Protect.

Block 2 · Lesson 11 · Electromagnetic Attack

Electromagnetic Attack (EA)

Offensive EW

Deny, degrade, or deceive the enemy's use of the spectrum.

Noise jamming — self-protect and stand-off; brute-force the $S_{\min}$ term
Deception — DRFM false targets; lie to the tracker instead of shouting at it
Expendables — chaff and flares; give the seeker something better to love
NAVWAR — counter-PNT; the spectrum includes GPS

Legacy terms: ECM, and confusingly, “EW.” Modern Joint term: Electromagnetic Attack.

Block 2 · Lesson 11 · Part Three

The Listener's Advantage

One asymmetry sits under all of it, and it falls straight out of the exponents you have been carrying since L3.

Block 2 · Lesson 11 · Listener's Advantage

The Listener's Advantage

The radar needs its energy to make a round trip. The RWR only needs to hear it arrive.

Radar detection: power falls as $1/R^4$ — two-way
RWR intercept: power falls as $1/R^2$ — one-way
Same transmitter, same instant: the listener wins by orders of magnitude
In practice the RWR's limit is the horizon, not its sensitivity

The radar pays $R^4$ to see you. You pay $R^2$ to hear it.

Block 2 · Lesson 11 · The Cycle

The Endless Cycle: Measure, Counter, Counter-Counter

Action

The radar innovates: pulse-Doppler, frequency agility, LPI.

Reaction

Countermeasures answer: noise jammers, chaff, DRFM deception, LO.

Counter-reaction

ECCM closes the loop: hopping, side-lobe cancellation, adaptive processing, multistatic radar.

No move is permanent — every technique in B2 has a counter.

EW is decided as much by speed of adaptation as by hardware.

Block 2 · Lesson 11 · Roadmap

Block 2 Roadmap

ESL12–L14

→

EPL15–L16

→

EAL17–L18

→

Project 2L19–L20

ES — RWR architecture, angle of arrival, triangulation and fusion
EP — LPI radar, agility, side-lobe cancellation, spread spectrum for comms
EA — jamming taxonomy, J/S and burn-through, DRFM deception, decoys
Project 2 — B-21 standoff emitter geolocation: design the collection, fix the emitters, defend the CEP

Same rhythm as B1: HW2 and Quiz 2 land with the Project 2 presentations at L20.

Block 2 · Lesson 11 · Quick Exercise

Quick Exercise / Type-along: Who Hears First

Type this with me — the B1 threat table, plus a $-60$ dBm RWR.

c = 3e8;  names = {'EW','ACQ','TTR'};
Pt   = [2e6 1e6 100e3];                  % W
G    = 10.^([25 30 35]/10);              % Gt = Gr
lam  = c ./ [0.5e9 3e9 10e9];            % UHF, S, X
Smin = 10.^([-158 -160 -150]/10);        % radar floors, W
sig  = 10.^([-17.9 -25.5 -32.0]/10);     % B-21 nose-on
Srwr = 10^(-60/10)/1e3;                  % -60 dBm -> W, 0 dBi
R4 = ((Pt.*G.^2.*lam.^2.*sig) ./ ((4*pi)^3*Smin)).^(1/4);
R2 = sqrt((Pt.*G.*lam.^2) ./ ((4*pi)^2*Srwr));
for k = 1:3
    fprintf('%-4s  radar %6.1f km   RWR %7.0f km  %4.0fx\n', ...
            names{k}, R4(k)/1e3, R2(k)/1e3, R2(k)/R4(k));
end
fprintf('Radio horizon from 40 kft: %.0f km.\n', 4.12*sqrt(12192));

The TTR sees the B-21 at 23 km. Since when has the B-21 heard it?

Then: double every $P_t$. Which range grows faster — and why?

Today's Interactive Demo: Listener's Advantage

Companion script: L11_OneWayVsTwoWay.m
In L12 we open up the box that does the hearing: the RWR

Live demo

Listener's Advantage

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

Demo hand-off; drive it from here. Two controls: chips pick the threat class - EW at UHF, ACQ at S band, TTR at X band, the same three radars from Block 1 and Project 1 - and one slider moves the range between the B-21 and that radar. The range axis is logarithmic and runs from one kilometre to a hundred thousand, because the story spans five decades. Two curves: the echo getting back to the radar, falling as one over R to the fourth, and the same radar's signal arriving at the RWR, falling as one over R squared. Each has its own dashed sensitivity floor, and the tiles read out where each curve crosses its floor. The darker shaded band is detect-before-detected with line of sight; the fainter band beyond it is where sensitivity still says yes but the emitter is over the radio horizon. Step the three classes and let them watch the ratio tile. Then park the slider past the horizon line and ask what is actually limiting the listener. Companion script they run on their own.

Block 2 · Lesson 11 · Wrap-Up

Wrap-Up

Key ideas

The range equation is a target list — every term is an EW lever
ES senses, EP defends, EA attacks; ES feeds the other two
One-way beats two-way: the listener detects at $R^2$ while the radar pays $R^4$
Every move has a counter — B2 is a tour of the move–countermove tree

Next lesson

L12: Electromagnetic Support — the RWR, inside and out
Pre-flight quiz for L12 due before class