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22-Elec-A3 Signals and Communications: May 2015

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

  1. Question 1 Periodic Ramp Train — Fourier Series, Power Spectral Density and Ideal Filtering
  2. Question 2 Second-Order Discrete-Time System — Transfer Function, Impulse Response and Canonical Realisation
  3. Question 3 Conventional AM — Power Budget, Spectrum, Envelope and Detection
  4. Question 4 PCM of a Speech Signal — Sampling, Quantization and Bit Rate
  5. Question 5 Square-Law Frequency Downconverter — Choice of IF and Filter Bandwidth
  6. Question 6 FM Signal Processing — Multiplication, Frequency Translation, Demodulation and Squaring
  7. Question 7 Speech Scrambler — Spectral Inversion and its Inverse

Start with Question 1 →

Paper format. 07-Elec-A3 Signals and Communications, May 2015 — 3 hours, closed book, non-programmable calculator permitted. Seven questions, all of equal value (20 marks each); any five constitute a complete paper and only the first five in the answer book are marked. All seven are solved here, since the set is a study resource.

Reference texts. B. P. Lathi & Z. Ding, Modern Digital and Analog Communication Systems, 5th ed.; B. P. Lathi, Linear Systems and Signals, 2nd ed.; A. V. Oppenheim & A. S. Willsky, Signals and Systems, 2nd ed.; J. G. Proakis & D. G. Manolakis, Digital Signal Processing, 4th ed.; S. Haykin & M. Moher, Communication Systems, 5th ed.

Check: pulse definition. The pulse is p(t) = t/a — a ramp, not a constant — and every part of Question 1 is solved against that reading. A constant-height pulse would make parts (a)–(c) trivial and would not produce the odd-harmonic structure the question is clearly aiming at.