B.Tech ECE · All 6 Units · 62 GATE Questions

Signals & Systems —
Complete Unit-Wise Notes

All 6 units covered in depth — classification, Fourier series, transforms, LTI systems, sampling — with GATE PYQs and solutions for every topic.

📊 GATE Weightage: 8–12 marks every year — one of the highest-scoring subjects
📈 GATE ECE — Signals & Systems Average Marks per Unit
1–2
Unit 1 · Intro & Classification
1–2
Unit 2 · Fourier Series
2–4
Unit 3 · Fourier Transform ⭐
2–3
Unit 4 · Laplace Transform ⭐
1–2
Unit 5 · Z-Transform
1–2
Unit 6 · Sampling
All Units
Signals & Systems — 6 Units
UNIT 1
Introduction to Signals and Systems
CT/DT signals, periodic/aperiodic, energy/power, even/odd, time shifting/scaling/reversal, elementary signals (impulse, step, ramp), classification of systems (linear, TI, causal, BIBO stable)
Signal ClassificationSignal OperationsImpulse & StepLTI PropertiesCausalityBIBO Stability
10 GATE Qs
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UNIT 2
Fourier Series
Dirichlet conditions, trigonometric Fourier series, exponential Fourier series, Fourier coefficients, line spectra (amplitude & phase), power spectrum, Parseval's theorem for FS, properties, symmetry conditions
Fourier CoefficientsExponential FSDirichlet ConditionsLine SpectrumParseval's
10 GATE Qs
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UNIT 3
Fourier Transform
FT definition & inverse FT, FT pairs table, properties (linearity, time shift, frequency shift, scaling, duality, convolution, modulation), ESD, Parseval's theorem, ideal filters, LTI frequency response H(jω)
FT PairsFT PropertiesConvolution TheoremDualityESDParseval's
12 GATE Qs
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UNIT 4
Laplace Transform
LT definition, ROC, bilateral vs unilateral LT, LT pairs, properties, inverse LT (partial fractions), transfer function H(s), poles and zeros, BIBO stability from ROC, initial/final value theorems
ROCLT PropertiesPartial FractionsPoles & ZerosStabilityIVT/FVT
12 GATE Qs
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UNIT 5
Discrete-Time Signals & Z-Transform
DT signals (δ[n], u[n], aⁿu[n]), DTFT, Z-transform definition, ROC in z-plane, Z-transform pairs, properties, inverse Z-transform, DT-LTI systems, H(z), stability from unit circle, convolution sum
DTFTZ-TransformROC (z-plane)Unit CircleH(z)DT Stability
10 GATE Qs
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UNIT 6
Sampling Theory
Nyquist-Shannon theorem, Nyquist rate and interval, aliasing mechanism, alias frequency formula, anti-aliasing filter, ideal reconstruction (sinc interpolation), ZOH, natural sampling, flat-top sampling, real-world sampling rates
Nyquist TheoremAliasingAnti-aliasing LPFZOHReconstruction
8 GATE Qs
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