Lesson 12 Flashcards#
Click a question to reveal the answer.
1. How do ES and ELINT differ in purpose and data depth?
ES collects just enough to answer what radar, what mode, right now, fast enough for the aircrew. ELINT collects full parametric depth on every emitter — including future threats — to build a library. ES fights the fight; ELINT studies the fight.
2. What bounds the bandwidth ES versus ELINT must cover?
ES is bounded by known threats — it only recognizes catalogued emitters. ELINT is bounded by any possible threat, since its job is to find the ones not yet catalogued. ELINT's product becomes the threat library the RWR classifies against.
3. Name the four functions of every threat-warning system and their OODA phases.
Observe (monitor the bands → Observe), Detect (recognize a threat signal → Orient), Classify (determine type and mode → Decide), Alert (warn aircrew and cue defenses → Act). Same four in any system, RF or IR.
4. Which of the four functions holds the hard engineering, and why?
Classify. Observe, Detect, and Alert are plumbing and ergonomics — wide antennas, a threshold, a display. Resolving a merged pulse stream into named emitters with current modes is where the real difficulty lives.
5. Walk the RWR block diagram from antenna to display.
Antennas (≈four, one per quadrant; small, broadband, low-gain) → Receiver (measures each pulse's parameters) → Processor (sorts, classifies, decides) → Display + cueing (aircrew scope plus chaff/jammer/decoy cues).
6. Why does an RWR use four small, low-gain antennas instead of one big one?
One per quadrant gives all-aspect coverage and a coarse bearing from the start. A warning receiver trades antenna gain for the ability to hear across the whole spectrum and all directions at once.
7. State the RWR's minimum-detectable-signal contract and the term that hurts it.
\(S_{\min} = kTB \cdot \text{NF} \cdot \text{SNR}_{\text{req}}\). Same form as a radar, but the bandwidth \(B\) now spans tens of GHz, so the noise floor is far higher.
8. The RWR's noise floor is much worse than a radar's — how does it still work?
Every decade of bandwidth costs about 10 dB of sensitivity, so a tens-of-GHz RWR is deaf-ish by comparison. But it detects transmitters, and radar main lobes arrive one-way and loud. For warning, wide-open beats narrow and sharp.
9. Name the five receiver types and their defining trait.
Crystal video (wide, fast, one signal); IFM (frequency only, ~octave); superheterodyne (selective, recovers any modulation, one at a time); channelized (many simultaneous signals); digital (wide, fast, flexible — the modern default).
10. What is a PDW, and what can you measure from one, two, and many pulses?
A pulse descriptor word — the measured record of an intercepted pulse. One pulse: frequency, PW, TOA, AoA, power, polarization, modulation. Two pulses: PRI (most diagnostic). Many pulses: staggered PRI, carrier modulation, antenna scan rate.
11. Why is scan rate measured last in the classification sequence?
The cheap, fast measurements run first and the processor stops once the ID resolves. Scan rate can't be hurried — you must wait for the threat's beam to sweep back across you to time how fast it rotates.
12. List the processor's deinterleave-to-classify sequence.
(1) Deinterleave — cluster PDWs by frequency, AoA, and PW into per-emitter buckets; (2) estimate PRI by differencing TOAs in each bucket; (3) classify against the threat library; (4) determine mode — search/track/launch, with PRF jumps betraying the handoff. Sorting comes before classifying.
13. When is the RWR blind, and what's the doctrinal lesson?
Against anything that doesn't radiate RF: LPI radars (below the detection floor), EMCON (no transmission until late), passive IR/EO seekers (no launch warning), and silent terminal phases (GPS/inertial/home-on-jam). Survivability never rides on one sensor — a quiet scope is not a safe sky (B3 covers IR).