ECE 495 — Electromagnetic Warfare and Survivability

Block 1: Radar Fundamentals
Lesson 7: IADS Threat Radar Taxonomy

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

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Block 1 · Lesson 7 · Where We Left Off

Where We Left Off

L6 gave us antennas as patterns. L3–L5 gave us the equations.

Threats use different radars for different jobs. Knowing which is which is half of EW.

Today

The cast of characters inside an IADS — EW, ACQ, HF, GCI, TTR, AI, TIR, seekers, and fuses.

Block 1 · Lesson 7 · Objectives

Lesson Objectives

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

Name the radar classes in a layered IADS
Match each class to its band, PRF regime, and beam type
Map each class to the kill-chain link it advances
Predict how LO changes the IADS's effective coverage at each layer

Seven radars, one engagement, and every one of them attacked differently.

Block 1 · Lesson 7 · Part One

The Cast of Characters

Every class trades range for precision, and every class hands its track to the next. Band, PRF, and beam are how you tell them apart from the cockpit.

Block 1 · Lesson 7 · Layered System

The IADS as a Layered System

→

ACQ / HF

→

GCI

→

TTR

→

AI / TIR

→

Seeker

→

Fuse

Each class trades range for precision; together they cover the engagement
Information is handed off from class to class — breaking handoff degrades the chain
EW and ES sensors fight at every layer

The IADS isn't one radar — it's a cast of cooperating ones.

Block 1 · Lesson 7 · Detection Layer

Detection Layer: Early Warning Radars

EW radar — the long-range eyes of the IADS.

Band: UHF or L — propagation, large antenna, low atmospheric loss
Range: hundreds of km
PRF: low — big $R_u$ at the cost of $v_u$
Beam: wide fan, slow rotation, 2D track only
Job: detect inbound air activity, alert higher echelons

Why it matters

A 2D track only — range and azimuth, no height. It cannot shoot you. It tells everyone else where to look.

EW radars are where stealth pays its highest dividend in absolute kilometers.

Block 1 · Lesson 7 · Tracking Layer

Acquisition and Height Finding

ACQ provides 3D tracks for engagement. Paired HF can add elevation to a 2D ACQ.

Band: S typical
Range: long (hundreds of km), but shorter than EW
PRF: low / medium
Beam: fan beam ACQ + pencil-beam HF, or modern 3D ACQ
Job: produce 3D tracks suitable for handoff to engagement radars

The handoff

A fire-control radar cannot search the whole sky. ACQ narrows it to a cue the TTR can slew onto.

GCI sits at the C2 layer — vectors interceptor aircraft using the 3D picture.

Block 1 · Lesson 7 · Engagement Layer

Engagement Layer: TTR and TIR

TTR — target tracking radar, the SAM site's fire-control sensor. TIR — target illuminating radar for semi-active missiles.

Band: X typical
Range: medium (tens to a low hundred km)
PRF: medium / high; often pulse-Doppler
Beam: pencil, narrow HPBW, slewable
Job: TTR holds the target; TIR floods it for the missile seeker

Tell them apart

A pulse radar that holds you is a TTR. A continuous-wave emitter beside it is a TIR, and the missile is already flying.

If you break the TTR-to-missile lock, the engagement is over.

Block 1 · Lesson 7 · Terminal Layer

Airborne and Terminal Sensors

AI — Airborne Interceptor radar (fighter fire control)
- X-band, AESA, multi-mode (search, track, scan-while-track)
Active seeker on the missile itself
- Ka or mmW for compact aperture; very high PRF; final 5–20 km
Proximity fuse
- Very short range, CW or high-PRF; triggers warhead at burst radius

EW radars find you; trackers kill you.

Block 1 · Lesson 7 · Kill Chain

Mapping to the Kill Chain

Kill-chain link	Radar class	Primary band
Detect	EW	UHF / L
Track	ACQ + HF, GCI	S
Identify	ACQ multi-mode, ESM	S
Engage (cue)	TTR, AI	X
Engage (illuminate)	TIR	X
Engage (terminal)	Active seeker	Ka
Kill	Proximity fuse	mmW

Break one row $\Rightarrow$ break the chain
EW investments tend to attack the early rows (cheaper, higher payoff)

Block 1 · Lesson 7 · Part Two

What LO Buys

Every ring shrinks. They do not shrink together — and the disagreement is where the ingress corridors are.

Block 1 · Lesson 7 · Coverage

Layered Coverage Against a Legacy Fighter

One site, three classes, drawn to scale. A 1 m$^{2}$ target gives every radar the same $\sigma$, so the rings are just the range equation.

scale: 600 px = 700 km

Class	$R_{\max}$	% cut
EW	700 km	0%
ACQ	470 km	0%
TTR	150 km	0%

EW sees farthest, TTR sees least — long wavelength and a sensitive receiver buy the outer ring, and the TTR trades that range away for the angular precision a firing solution needs.

Block 1 · Lesson 7 · Coverage

Now Fly the B-21 Through It

Same site, same radars. Broadband LO suppresses hardest at high frequency, so each class sees the bomber's RCS in its own band.

scale: 600 px = 700 km

Class	$\sigma$ seen	$R_{\max}$	% cut
EW	−17.9 dBsm	250 km	64%
ACQ	−25.5 dBsm	108 km	77%
TTR	−32.0 dBsm	24 km	84%

Nose-on RCS in each threat band. One $\sigma$ for everybody would have cut all three by the same percent — the bands disagree, and that disagreement is the story.

LO is standoff, not invisibility. The inner rings are still there.

Today's Interactive Demo: IADS Coverage Explorer

Companion script: L7_IADSRadarSurvey.m
In L8 we add the missing piece: how detection actually happens ($P_d$, $P_{fa}$, SNR)

Live demo

IADS Coverage Explorer

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

Demo hand-off; drive it from here. Three coverage rings, EW, ACQ and TTR, drawn to scale around one site. Slide the radar cross section and watch every ring collapse together. The readout table gives maximum range, the change against the legacy value, and the percent cut for each class. Step through the presets: legacy, fourth generation low observable, B-twenty-one and next generation. Then press the band-dependent preset, which is the one this lesson is built on: each radar is given the bomber's cross section in its own band, the rings stop collapsing together and the percent column stops agreeing with itself. Compare that against the flat preset and ask which picture a mission planner should route against. Add the airborne interceptor ring to see the terminal layer close in even on a stealthy target, and drag any radar off the site to see where the layers overlap when the emitters are not co-located. Companion script runs on their own.

Block 1 · Lesson 7 · Type-along

Your Turn

Laptops open, MATLAB up. Three threat classes as vectors, one range equation, and an ordering nobody told the code about.

Block 1 · Lesson 7 · Quick Exercise

Quick Exercise / Type-along: Build the Three Rings

Type this with me. Three IADS classes, one range equation, $\sigma = 1$ m$^2$.

c = 3e8;  names = {'EW','ACQ','TTR'};
Pt   = [2e6   1e6   100e3];   % W
G    = [25    30    35   ];   % dBi, Gt = Gr
f    = [0.5e9 3e9   10e9 ];   % Hz
Smin = [-158  -160  -150 ];   % dBW
lam = c ./ f;  Gl = 10.^(G/10);  Sw = 10.^(Smin/10);
R = ((Pt .* Gl.^2 .* lam.^2) ./ ((4*pi)^3 * Sw)).^(1/4);
for k = 1:3
    fprintf('%-4s  R_max = %6.1f km\n', names{k}, R(k)/1e3);
end
fprintf('Detected %.1fx farther out than tracked.\n', R(1)/R(3));

Nobody told the code which radar is "early warning." So which of $P_t$, $G$, $\lambda$, $S_{\min}$ separated the EW ring from the TTR ring?

And which one is working against the radar that sees farthest?

Block 1 · Lesson 7 · Wrap-Up

Wrap-Up

Key ideas

IADS is a cascade of radar classes, each doing one job
Band $+$ PRF $+$ beam tell you the class and the kill-chain link
LO buys absolute km at the EW / ACQ layers; engagement layers still close in

Next lesson

L8: Detection theory — SNR, $P_d$, $P_{fa}$, integration gain
Work the L8 pre-flight before class — you could be the one up front