L15 Pre-flight

L15 Pre-flight#

Block 2: RF Electronic Warfare — Lesson 15: Electromagnetic Protect Work this before L15. Pre-flights are never collected — in class, anyone may be cold-called to present any question at the board, and that recitation is the participation grade.

Assumed pre-class reading#

  • L14 wrap-up

  • The Jupyter Book Reading page for L15 — EP vs ES/EA, LPI (EMCON, power management, spread/pulse compression), frequency and polarization agility, and side-lobe suppression.

Quiz questions (5 items, ~5 minutes)#

Q1. (Multiple choice) Electromagnetic Protect (EP) is best described as:

  • [ ] (a) Denying the enemy’s use of the spectrum by jamming or deceiving his receivers

  • [ ] (b) Protecting our own use of the spectrum against jamming and interference

  • [ ] (c) Listening to hostile emitters to sort, identify, and locate them

  • [ ] (d) Reducing an aircraft’s infrared signature so seekers lose lock

Q2. (Multiple choice) A low-probability-of-intercept radar spreads its energy over a wide bandwidth (e.g., a long coded pulse). Why does this help the radar more than the eavesdropper?

  • [ ] (a) Spreading the pulse raises the radar’s total radiated power, so the echo grows faster than the intercepted signal

  • [ ] (b) The radar’s matched filter re-concentrates the spread energy, and the eavesdropper has no code to do the same

  • [ ] (c) A wide bandwidth lowers the radar’s own receiver noise floor, so the echo clears the threshold either way

  • [ ] (d) Intercept receivers are narrowband by design and cannot watch the whole spread bandwidth at once

Q3. (Multiple choice) Frequency agility (hopping the carrier pulse-to-pulse) most directly defeats:

  • [ ] (a) Barrage jamming

  • [ ] (b) Chaff and other passive decoys

  • [ ] (c) Spot jamming

  • [ ] (d) Infrared-guided missile seekers

Q4. (Multiple choice) Most jamming and intercept energy reaches a radar through its:

  • [ ] (a) Main beam, where the antenna’s gain is highest

  • [ ] (b) Power supply and wiring, as conducted interference

  • [ ] (c) Side-lobes, the off-axis gain around the main beam

  • [ ] (d) Receiver protector, a limiter guarding the front end

Q5. (Short answer) An agile radar hops across N = 20 channels. A power-limited jammer must choose between concentrating on a few channels (spot) or spreading across all 20 (barrage). Explain the dilemma and roughly how much the barrage choice costs in per-channel J/S.

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