L5 Pre-flight

L5 Pre-flight#

Block 1: Radar Fundamentals — Lesson 5: Doppler, MTI, and Pulse-Doppler Work this before L5. 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#

  • L4 wrap-up

  • The Jupyter Book Reading page for L5 — Doppler & MTI: the Doppler effect, ground clutter, MTI as a high-pass filter, blind speeds, and pulse-Doppler / R-D maps.

Quiz questions (5 items, ~5 minutes)#

Q1. (Multiple choice) For a monostatic radar at wavelength \(\lambda\), the Doppler shift produced by a target with radial velocity \(v_r\) is:

  • [ ] (a) \(f_d = v_r / \lambda\)

  • [ ] (b) \(f_d = 2 v_r / \lambda\)

  • [ ] (c) \(f_d = v_r \lambda\)

  • [ ] (d) \(f_d = 4 v_r / \lambda\)

Q2. (Multiple choice) A target moving at 300 m/s radially closing on an X-band (\(\lambda = 3\) cm) radar produces a Doppler shift of approximately:

  • [ ] (a) 200 Hz

  • [ ] (b) 2 kHz

  • [ ] (c) 20 kHz

  • [ ] (d) 200 kHz

Q3. (Multiple choice) A single-delay-line MTI canceller has zeros (notches) in its frequency response at:

  • [ ] (a) only \(f = 0\)

  • [ ] (b) \(f = 0\) and \(f = \) PRF only

  • [ ] (c) \(f = 0, \mathrm{PRF}, 2\mathrm{PRF}, \ldots\)

  • [ ] (d) \(f = \) PRF \(/2\) only

Q4. (Short answer) In one sentence, explain why raising the PRF helps a pulse-Doppler radar deal with the blind-speed problem.

Q5. (Multiple choice) In a range-Doppler map produced by pulse-Doppler processing, ground clutter appears primarily as:

  • [ ] (a) Scattered noise across all bins

  • [ ] (b) A horizontal stripe along one range bin

  • [ ] (c) A vertical ridge near zero Doppler

  • [ ] (d) A single bright cell

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