Signals and Systems MCQs 2026

Zero-order hold in digital control introduces

1. A infinite bandwidth without distortion ✓
2. B elimination of all phase delay ✓
3. C frequency response sinc-like droop and phase lag ✓
4. D only improves Nyquist margin unconditionally ✓

Effective bits of ADC measure

1. A only DC offset error without noise ✓
2. B only full-scale voltage without noise ✓
3. C only clock jitter without amplitude error ✓
4. D resolution equivalent to ideal ADC achieving same SNR ✓

Sampling period T equals

1. A fs ✓
2. B 2πfs ✓
3. C fs squared ✓
4. D 1/fs ✓

Nyquist rate for signal bandlimited to B Hz is

1. A 2B samples per second ✓
2. B B/2 samples per second ✓
3. C 4B always without exception ✓
4. D 1/B samples per second ✓

Reconstruction of bandlimited signal from samples uses

1. A differentiator only ✓
2. B full-wave rectifier only ✓
3. C JK flip-flop toggle only ✓
4. D ideal low-pass filter (sinc interpolation) ✓

Signal-to-quantization-noise ratio improves approximately by

1. A 0 dB per bit always ✓
2. B 20 dB per bit always ✓
3. C decreases with more bits ✓
4. D 6 dB per bit of ADC resolution ✓

Quantization noise in uniform quantizer is approximately

1. A always zero without error ✓
2. B sinusoidal without relation to LSB ✓
3. C uniformly distributed over one LSB ✓
4. D Gaussian with infinite variance always ✓

Sample-and-hold circuit maintains

1. A digital count indefinitely without drift ✓
2. B analog value at sampling instant for ADC conversion ✓
3. C high-frequency amplification only ✓
4. D rectified DC without sampling ✓

Anti-aliasing filter before ADC is

1. A high-pass filter only ✓
2. B low-pass filter limiting bandwidth below Nyquist limit ✓
3. C band-stop at DC only ✓
4. D logic gate with hysteresis ✓

Aliasing occurs when

1. A sampling rate is infinitely high always ✓
2. B anti-alias filter is perfect without limit ✓
3. C signal contains frequencies above fs/2 and appears as lower frequency ✓
4. D only DC signals are sampled ✓

Nyquist sampling theorem requires sampling frequency at least

1. A equal to lowest frequency only ✓
2. B half the highest frequency ✓
3. C twice the highest frequency component in the signal ✓
4. D ten times any harmonic without bound ✓

Convolution integral limits for causal f and g starting at zero extend

1. A from −∞ to ∞ always without limit change ✓
2. B from 0 to t ✓
3. C from t to ∞ only ✓
4. D only single point τ = t ✓

System stability from impulse response requires for BIBO

1. A absolutely integrable h(t) for continuous LTI ✓
2. B h(t) unbounded always for stability ✓
3. C only pole at origin without decay ✓
4. D only digital systems without integration ✓

Circular convolution differs from linear convolution when

1. A DFT length causes time-domain aliasing of tails ✓
2. B signals are aperiodic without wrap ✓
3. C only continuous-time applies ✓
4. D inputs are impulses only ✓

Overlap-add method is used for

1. A K-map minimization only ✓
2. B CT saturation testing only ✓
3. C only analog differentiation ✓
4. D efficient block convolution of long sequences ✓

Discrete-time convolution sum is

1. A product x[n]h[n] only ✓
2. B Fourier series of continuous signal ✓
3. C y[n] = Σ x[k] h[n − k] ✓
4. D only logic OR of bits ✓

Causal system impulse response is

1. A zero for t < 0 ✓
2. B nonzero for all negative time always ✓
3. C undefined without Laplace ✓
4. D equal to step input always ✓

Convolution with unit impulse δ(t) returns

1. A the original signal f(t) ✓
2. B zero always ✓
3. C derivative of f(t) only ✓
4. D integral of f(t) only ✓

Graphical convolution involves

1. A only multiplying magnitudes at t=0 ✓
2. B flipping, shifting and integrating product of overlapping signals ✓
3. C only Laplace partial fractions without time view ✓
4. D only flip-flop clock edges ✓

Convolution is commutative meaning

1. A f * g = −g * f always ✓
2. B f * g = g * f ✓
3. C convolution never commutes ✓
4. D only for digital signals not analog ✓

Output of LTI system is convolution of input with

1. A step response only without convolution ✓
2. B only DC gain scalar ✓
3. C impulse response h(t) ✓
4. D only noise spectrum ✓

Convolution in time domain corresponds to multiplication in

1. A K-map domain only ✓
2. B logic truth table domain ✓
3. C Laplace domain (and Fourier domain with convergence) ✓
4. D only time-domain subtraction ✓

Convolution of two signals f(t) and g(t) is defined as

1. A integral of f(τ) g(t − τ) dτ ✓
2. B product f(t)g(t) only without integration ✓
3. C sum of Fourier coefficients only ✓
4. D XOR of digital bit sequences ✓

Laplace domain multiplication corresponds to

1. A time-domain convolution ✓
2. B time-domain addition only ✓
3. C Fourier series division ✓
4. D logic AND in gate network ✓

Second-order underdamped system poles are

1. A real and equal always ✓
2. B complex conjugate pair σ ± jωd ✓
3. C purely imaginary without real part always ✓
4. D on positive real axis for stability ✓

Unit impulse δ(t) has Laplace transform

1. A 0 ✓
2. B 1/s ✓
3. C 1 ✓
4. D s ✓

Partial fraction expansion aids

1. A K-map grouping of minterms ✓
2. B BJT beta measurement only ✓
3. C energy meter creep adjustment only ✓
4. D inverse Laplace transform of rational F(s) ✓

Laplace transform of derivative df/dt is

1. A F(s)/s only without initial condition ✓
2. B sF(s) − f(0−) ✓
3. C f(0−) only without sF(s) ✓
4. D 1/(s + jω) only ✓

Region of convergence (ROC) of Laplace transform specifies

1. A values of s for which the defining integral converges ✓
2. B only time-domain period T ✓
3. C only logic gate fan-out ✓
4. D only diode forward voltage ✓

Pole of H(s) at s = −a corresponds to

1. A sinusoid without decay always ✓
2. B constant DC without dynamics ✓
3. C exponential mode e^(−at) in impulse response ✓
4. D digital counter state only ✓

Transfer function H(s) of LTI system is ratio of

1. A time-domain convolution only without transform ✓
2. B Fourier series coefficients only ✓
3. C K-map product terms only ✓
4. D Laplace transform of output to input with zero initial conditions ✓

Final value theorem gives steady-state f(∞) from F(s) as

1. A limit of sF(s) as s approaches infinity ✓
2. B limit of sF(s) as s approaches 0 ✓
3. C pole at origin count only ✓
4. D inverse transform without limits ✓

Initial value theorem gives f(0+) from F(s) as

1. A limit of F(s) as s approaches 0 only ✓
2. B limit of sF(s) as s approaches infinity ✓
3. C derivative of F(s) at s=0 only ✓
4. D integral of F(s) without limit ✓

Laplace transform of e^(−at) u(t) is

1. A 1/(s − a) without sign ✓
2. B s/(s + a) ✓
3. C 1/(s + a) ✓
4. D a/s only ✓

Laplace transform of unit step u(t) is

1. A 1/s ✓
2. B s ✓
3. C 1/s² only ✓
4. D e^(−s) without 1/s ✓

Laplace transform converts time-domain function to

1. A only discrete frequency bins without s ✓
2. B complex frequency domain s = σ + jω ✓
3. C digital logic states only ✓
4. D spatial domain only ✓

Distortion analysis of amplifiers often uses

1. A only K-map minimization ✓
2. B only CT knee-point voltage ✓
3. C harmonic amplitudes from Fourier decomposition of output ✓
4. D only Johnson counter sequence ✓

RMS value of periodic signal can be found from Fourier coefficients using

1. A sum of squares of harmonic amplitudes (Parseval) ✓
2. B only peak value divided by π ✓
3. C only fundamental amplitude without harmonics ✓
4. D only DC term squared always without AC terms ✓

Frequency shifting property of Fourier transform multiplies time signal by e^(jω0t) to

1. A scale time axis only ✓
2. B invert spectrum about origin only ✓
3. C eliminate all negative frequencies without analytic signal ✓
4. D shift spectrum by ω0 ✓

Fourier transform of aperiodic signal yields

1. A continuous frequency spectrum ✓
2. B discrete harmonics only like periodic case ✓
3. C single coefficient without frequency spread ✓
4. D Laplace transform identical without jω ✓

Gibbs phenomenon refers to

1. A overshoot near discontinuities in truncated Fourier series reconstruction ✓
2. B DC drift in integrator op-amp ✓
3. C aliasing during undersampling ✓
4. D metastability in flip-flop ✓

Duty cycle change in rectangular pulse train affects

1. A only DC without harmonics ✓
2. B magnitudes of harmonic components in the spectrum ✓
3. C only fundamental without any harmonics change ✓
4. D Laplace region of convergence only ✓

Complex exponential Fourier coefficient Cn equals

1. A maximum peak of f(t) only ✓
2. B derivative of f(t) at t=0 only ✓
3. C Laplace transform at s=0 only ✓
4. D average value of f(t) e^(−jnω0t) over one period ✓

Line spectrum of periodic signal shows

1. A continuous spectrum only without lines ✓
2. B discrete frequencies at harmonics with corresponding amplitudes ✓
3. C only DC without harmonics always ✓
4. D phase margin on Bode plot ✓

Parseval theorem relates

1. A Laplace poles to zeros only ✓
2. B average power in time domain to sum of squared Fourier coefficients ✓
3. C convolution to sampling only ✓
4. D diode PIV to ripple factor ✓

Trigonometric Fourier series of odd function contains

1. A only cosine terms ✓
2. B only DC component ✓
3. C only sine terms ✓
4. D only even harmonics of cosine ✓

Trigonometric Fourier series of even function contains

1. A only sine terms ✓
2. B only odd harmonics without DC ever ✓
3. C exponentials with negative real parts only ✓
4. D only cosine terms (and possibly DC) ✓

Fundamental frequency of Fourier series is

1. A twice the highest harmonic always ✓
2. B always 50 Hz without exception ✓
3. C zero for all non-sinusoidal waves ✓
4. D reciprocal of the period of the waveform ✓

Fourier series represents a periodic signal as

1. A sum of sinusoids at harmonics of fundamental frequency ✓
2. B single exponential decay only ✓
3. C DC step without harmonics always ✓
4. D random noise without structure ✓

Undersampling of bandpass signal can still avoid aliasing if

1. A no filter is used ever ✓
2. B signal is not bandlimited ✓
3. C only DC is present ✓
4. D signal occupies a band within an integer slot of fs ✓