কমিউনিকেশন ইঞ্জিনিয়ারিং MCQ
1–10: Signals & Systems
-
Continuous signal কোনটি?
A) ডিসক্রিট টাইম সিগন্যাল
B) ধারাবাহিক টাইম সিগন্যাল
C) ডিজিটাল সিগন্যাল
D) র্যান্ডম সিগন্যাল -
Unit step function এর মান t<0 এ কত?
A) 1
B) -1
C) 0
D) অসীম -
Impulse function কে বলা হয়—
A) u(t)
B) δ(t)
C) r(t)
D) sin(t) -
Linear system এর প্রধান বৈশিষ্ট্য—
A) Non-additivity
B) Superposition
C) Non-linearity
D) Randomness -
Time invariant system মানে—
A) সময়ের উপর নির্ভরশীল
B) সময় পরিবর্তনে output পরিবর্তিত হয়
C) সময় পরিবর্তনে system পরিবর্তিত হয় না
D) সব সময় পরিবর্তিত -
Fourier transform ব্যবহৃত হয়—
A) Time domain analysis
B) Frequency domain analysis
C) Power calculation
D) Noise removal -
Convolution ব্যবহৃত হয়—
A) Multiplication
B) System response
C) Addition
D) Differentiation -
Stability condition হলো—
A) BIBO stable
B) Unstable always
C) Random output
D) Infinite input -
Energy signal এর শক্তি—
A) অসীম
B) শূন্য
C) সীমিত
D) নেতিবাচক -
Power signal এর শক্তি—
A) অসীম energy
B) শূন্য
C) সীমিত energy
D) কোনো শক্তি নেই
11–20: Sampling Theorem
-
Nyquist rate হলো—
A) fs/2
B) 2fm
C) fm/2
D) 4fm -
Aliasing ঘটে যখন—
A) fs > 2fm
B) fs < 2fm
C) fs = 2fm
D) fs = fm -
Sampling theorem প্রযোজ্য—
A) Non-linear signal
B) Band-limited signal
C) Random signal
D) Noise signal -
Anti-aliasing filter ব্যবহৃত হয়—
A) Amplification
B) Noise increase
C) High frequency removal
D) Modulation -
Sampling frequency কম হলে—
A) Better signal
B) Aliasing
C) No change
D) Gain increase -
Reconstruction filter হলো—
A) LPF
B) HPF
C) BPF
D) Notch -
Nyquist interval—
A) 1/fm
B) 1/2fm
C) 2fm
D) fm -
Sample and hold circuit ব্যবহৃত হয়—
A) Modulation
B) Sampling
C) Filtering
D) Amplifying -
Ideal sampling is—
A) Impulse sampling
B) Continuous sampling
C) Random sampling
D) Delayed sampling -
PCM এর ভিত্তি হলো—
A) Filtering
B) Sampling
C) Multiplication
D) Integration
21–40: AM (Amplitude Modulation)
-
AM এর পূর্ণরূপ—
A) Angle Modulation
B) Amplitude Modulation
C) Automatic Modulation
D) Analog Modulation -
AM এ carrier পরিবর্তিত হয়—
A) Frequency
B) Amplitude
C) Phase
D) Power -
Modulation index এর মান—
A) >1
B) <0
C) 0–1
D) অসীম -
Over modulation হলে—
A) Signal clear
B) Distortion
C) No effect
D) Gain increase -
AM bandwidth—
A) fm
B) 2fm
C) 4fm
D) fm/2 -
AM signal formula—
A) Ac + Am
B) Ac(1 + m cos ωt)
C) Am sin t
D) Ac - Am -
Carrier frequency সাধারণত—
A) Low
B) Zero
C) High
D) Negative -
DSB-SC মানে—
A) Double sideband suppressed carrier
B) Direct signal
C) Digital signal
D) Dual carrier -
SSB এ থাকে—
A) One sideband
B) Two sidebands
C) No sideband
D) Infinite band -
Envelope detector ব্যবহৃত হয়—
A) FM
B) AM
C) PCM
D) ASK -
AM এ noise sensitivity—
A) কম
B) বেশি
C) শূন্য
D) নেই -
Power efficiency AM এ—
A) 100%
B) 33%
C) 50%
D) 10% -
Carrier power বেশি হলে—
A) Efficiency কমে
B) Noise বাড়ে
C) Signal vanish
D) Frequency increases -
AM ব্যবহৃত হয়—
A) TV only
B) Radio broadcasting
C) Mobile
D) WiFi -
Sideband contains—
A) Information
B) Noise only
C) Carrier only
D) Power only -
Bandwidth of SSB—
A) 2fm
B) fm
C) 4fm
D) 0 -
Modulation depth =
A) m
B) f
C) A
D) P -
AM detection method—
A) Envelope
B) PLL
C) ADC
D) DAC -
Distortion free AM requires—
A) m>1
B) m≤1
C) m=2
D) m=0 -
Carrier in AM carries—
A) No info
B) Full info
C) Partial info
D) Noise
41–60: FM (Frequency Modulation)
-
FM এর পূর্ণরূপ—
A) Fast Modulation
B) Frequency Modulation
C) Fixed Modulation
D) Forward Modulation -
FM এ পরিবর্তিত হয়—
A) Amplitude
B) Frequency
C) Power
D) Voltage -
FM noise immunity—
A) Low
B) High
C) Zero
D) Negative -
FM bandwidth নির্ধারণ করে—
A) Carson’s rule
B) Ohm’s law
C) Kirchhoff
D) Fourier law -
FM wave is—
A) Constant amplitude
B) Variable amplitude
C) Zero amplitude
D) Random amplitude -
FM modulation index—
A) β
B) α
C) γ
D) δ -
Narrowband FM bandwidth—
A) 2fm
B) fm
C) 4fm
D) 0 -
FM is used in—
A) Radio
B) AM radio
C) DC systems
D) Optical fiber only -
Pre-emphasis used for—
A) Noise reduction
B) Power increase
C) Frequency decrease
D) Amplification only -
De-emphasis is used in—
A) Receiver
B) Transmitter
C) Channel
D) Antenna -
FM is better than AM because—
A) Less noise
B) More noise
C) No signal
D) Low power -
FM carrier amplitude—
A) Varies
B) Constant
C) Zero
D) Infinite -
FM demodulation uses—
A) Detector
B) Integrator
C) Differentiator
D) PLL -
Wideband FM has—
A) Low β
B) High β
C) Zero β
D) Negative β -
FM frequency deviation depends on—
A) Message signal
B) Carrier only
C) Noise
D) Power -
FM transmission is—
A) Band efficient
B) Power efficient
C) Noise resistant
D) All -
FM is used in TV sound because—
A) Noise immunity
B) Cheap
C) Simple
D) Low bandwidth -
FM spectrum is—
A) Infinite
B) Discrete
C) Continuous
D) DC only -
FM uses more bandwidth than—
A) AM
B) PCM
C) ASK
D) FSK -
FM signal quality depends on—
A) SNR
B) Voltage only
C) Current only
D) Resistance
61–80: Filtering & Communication
-
Low pass filter allows—
A) High freq
B) Low freq
C) All freq
D) No freq -
High pass filter blocks—
A) High freq
B) Low freq
C) Noise only
D) Signal -
Band pass filter allows—
A) One band
B) All bands
C) No band
D) DC only -
Notch filter removes—
A) Band
B) Specific frequency
C) All freq
D) Noise only -
Filter is used for—
A) Amplification
B) Noise removal
C) Modulation
D) Sampling -
Ideal filter is—
A) Impossible
B) Real
C) Cheap
D) No loss -
FIR stands for—
A) Fast impulse response
B) Finite impulse response
C) Free impulse response
D) Fixed impulse response -
IIR stands for—
A) Infinite impulse response
B) Instant impulse response
C) Internal impulse response
D) Ideal impulse response -
FIR is always—
A) Unstable
B) Stable
C) Random
D) Noisy -
IIR is—
A) Always stable
B) May be unstable
C) No effect
D) Digital only -
Filter order increases—
A) Sharpness
B) Noise
C) Delay
D) Frequency -
LPF cutoff frequency defines—
A) Pass/stop boundary
B) Power
C) Amplitude
D) Phase -
Digital filter works on—
A) Analog signal
B) Discrete signal
C) Optical signal
D) RF only -
Analog filter uses—
A) Software
B) Hardware
C) Code
D) AI -
Butterworth filter is—
A) Sharp
B) Flat response
C) No response
D) Random -
Chebyshev filter has—
A) Ripple
B) Flat response
C) No gain
D) DC only -
Filter attenuates—
A) Signal
B) Noise
C) Power
D) Frequency only -
Ideal LPF response is—
A) Sharp cutoff
B) Smooth
C) Random
D) No response -
Sampling theorem relates to—
A) Filtering
B) Modulation
C) Time-frequency
D) All -
Reconstruction uses—
A) LPF
B) HPF
C) BPF
D) Noise
81–100: Mixed Concepts
-
Carrier signal is—
A) Information
B) Medium
C) Noise
D) Filter -
Modulation is used to—
A) Increase frequency
B) Transmit signal
C) Remove noise
D) Decode -
Demodulation is—
A) Encoding
B) Recovery of signal
C) Noise addition
D) Amplification -
Signal to noise ratio—
A) SNR
B) INR
C) PNR
D) FNR -
Higher SNR means—
A) Better quality
B) Poor signal
C) No signal
D) Noise only -
Bandwidth means—
A) Power
B) Frequency range
C) Time
D) Amplitude -
Analog signal is—
A) Continuous
B) Discrete
C) Binary
D) Random -
Digital signal is—
A) Continuous
B) Discrete
C) Analog
D) Noise -
Communication system needs—
A) Transmitter
B) Receiver
C) Channel
D) All -
Noise is—
A) Useful signal
B) Undesired signal
C) Carrier
D) Filter -
Channel is—
A) Medium
B) Device
C) Signal
D) Filter -
Attenuation means—
A) Increase
B) Decrease
C) Amplify
D) Modulate -
Distortion is—
A) Signal change
B) Noise removal
C) Amplification
D) Filtering -
Multiplexing is—
A) One signal
B) Multiple signals
C) Noise only
D) Filter -
TDM stands for—
A) Time division multiplexing
B) Total data modulation
C) Time delay mode
D) Transfer data mode -
FDM stands for—
A) Frequency division multiplexing
B) Fast data mode
C) Fixed data modulation
D) Free data method -
ASK is—
A) Amplitude shift keying
B) Analog signal keying
C) Audio signal keying
D) Automatic keying -
FSK is—
A) Frequency shift keying
B) Fast signal keying
C) Free signal keying
D) Fixed signal keying -
PSK is—
A) Phase shift keying
B) Power signal keying
C) Pulse signal keying
D) Partial signal keying -
Digital communication is—
A) Reliable
B) Noisy always
C) Analog only
D) Random
101–110: Signals & System (Advanced)
-
Laplace transform ব্যবহৃত হয়—
A) Time domain
B) Frequency domain
C) s-domain analysis
D) Noise analysis -
ROC মানে—
A) Region of convergence
B) Rate of change
C) Range of channel
D) Response of circuit -
Causal system হলো—
A) Future dependent
B) Past dependent
C) No input
D) Random output -
Anti-causal system depends on—
A) Future input
B) Past input
C) No input
D) Noise -
DTFT প্রযোজ্য—
A) Continuous signal
B) Discrete signal
C) Analog only
D) Random only -
Z-transform ব্যবহার হয়—
A) Continuous system
B) Discrete system
C) Noise only
D) Filter only -
Pole-zero plot ব্যবহৃত হয়—
A) Stability analysis
B) Power analysis
C) Noise reduction
D) Amplification -
System is stable if poles are—
A) Outside unit circle
B) On unit circle
C) Inside unit circle
D) Infinite -
Impulse response h(t) define করে—
A) Input
B) System behavior
C) Noise
D) Power -
Step response is output for—
A) δ(t)
B) u(t)
C) sin(t)
D) cos(t)
111–120: Sampling Theory
-
Sampling converts—
A) Analog to digital
B) Digital to analog
C) Noise to signal
D) Filter to signal -
Quantization is—
A) Sampling
B) Discretization of amplitude
C) Filtering
D) Modulation -
Aliasing can be removed by—
A) LPF
B) HPF
C) BPF
D) Amplifier -
Oversampling means—
A) fs < Nyquist
B) fs = Nyquist
C) fs > Nyquist
D) fs = 0 -
Sampling frequency unit is—
A) Hz
B) Watt
C) Ampere
D) Volt -
PCM stands for—
A) Pulse Code Modulation
B) Phase Code Modulation
C) Power Code Modulation
D) Pulse Channel Modulation -
Delta modulation is—
A) Analog
B) Digital
C) Optical
D) Noise -
Quantization error is—
A) Signal
B) Noise
C) Carrier
D) Filter -
Uniform quantization uses—
A) Equal step size
B) Random step
C) Variable step
D) No step -
Non-uniform quantization reduces—
A) Bandwidth
B) Noise
C) Quantization error
D) Power
121–140: AM (Advanced)
-
AM wave envelope is traced by—
A) Carrier
B) Message signal
C) Noise
D) Filter -
Modulation index >1 causes—
A) No distortion
B) Over modulation
C) Under modulation
D) No signal -
DSB-FC means—
A) Full carrier
B) Suppressed carrier
C) No carrier
D) Random carrier -
AM transmission efficiency depends on—
A) Carrier power
B) Frequency
C) Noise
D) Phase -
Sideband power contains—
A) Information
B) Carrier only
C) Noise only
D) DC -
AM demodulation requires—
A) Mixer
B) Detector
C) Filter
D) Oscillator -
Envelope detector uses—
A) Diode
B) Transistor
C) Op-amp
D) ADC -
AM is most affected by—
A) Phase noise
B) Amplitude noise
C) Frequency stability
D) DC bias -
Balanced modulator is used in—
A) DSB-SC
B) FM
C) PCM
D) ASK -
AM spectrum consists of—
A) One frequency
B) Carrier + sidebands
C) Noise only
D) DC only -
Carrier suppression improves—
A) Efficiency
B) Noise
C) Bandwidth
D) Power loss -
SSB requires—
A) LPF only
B) Filter method
C) ADC
D) DAC -
Vestigial sideband is used in—
A) TV transmission
B) Radio
C) WiFi
D) Bluetooth -
AM is simple but—
A) Efficient
B) Less efficient
C) Digital
D) Noise free -
Modulation depth is another name of—
A) Frequency
B) Modulation index
C) Power
D) Gain -
AM wave contains—
A) DC only
B) AC only
C) Both AC and DC
D) Noise only -
Lower sideband frequency is—
A) fc + fm
B) fc - fm
C) fc × fm
D) fc / fm -
Upper sideband frequency is—
A) fc - fm
B) fc + fm
C) fc / fm
D) fc × fm -
AM detection is also called—
A) Mixing
B) Demodulation
C) Filtering
D) Sampling -
AM bandwidth depends on—
A) Carrier
B) Message signal
C) Power
D) Phase
141–160: FM (Advanced)
-
FM signal bandwidth is approximated by—
A) Nyquist rule
B) Carson’s rule
C) Fourier rule
D) Ohm’s law -
Frequency deviation is proportional to—
A) Carrier
B) Message amplitude
C) Noise
D) Filter -
FM has better—
A) Power efficiency
B) Noise immunity
C) Bandwidth efficiency
D) DC stability -
Narrowband FM has small—
A) Carrier
B) Modulation index
C) Frequency
D) Power -
Wideband FM has large—
A) β
B) Noise
C) Power loss
D) Distortion -
FM detection is done using—
A) PLL
B) ADC
C) LPF
D) DAC -
FM signal amplitude is—
A) Variable
B) Constant
C) Zero
D) Random -
FM is used in mobile communication because—
A) Cheap
B) Noise resistant
C) Low power
D) Simple -
Pre-emphasis boosts—
A) Low frequency
B) High frequency
C) DC
D) Noise -
De-emphasis reduces—
A) Noise
B) Signal
C) Power
D) Frequency -
FM capture effect means—
A) Weak signal dominates
B) Strong signal dominates
C) Noise dominates
D) Carrier disappears -
FM modulation index β =—
A) Δf/fm
B) fm/Δf
C) fc/fm
D) fm/fc -
FM spectrum has—
A) Infinite sidebands
B) No sidebands
C) One frequency
D) DC only -
FM is more complex than—
A) PCM
B) AM
C) ASK
D) PSK -
FM receiver uses—
A) Mixer
B) Discriminator
C) Filter
D) ADC -
FM is less affected by—
A) Phase noise
B) Amplitude noise
C) Power noise
D) DC noise -
Frequency modulation is—
A) Linear
B) Non-linear
C) Digital
D) Random -
FM requires more bandwidth than—
A) AM
B) PCM
C) PSK
D) FSK -
FM noise improvement is called—
A) SNR improvement
B) Power gain
C) Frequency gain
D) Phase gain -
FM signal depends on—
A) Amplitude variation
B) Frequency variation
C) Power only
D) DC only
161–180: Filters & Communication
-
Ideal LPF has transition band—
A) Wide
B) Zero
C) Infinite
D) Random -
FIR filter depends on—
A) Feedback
B) Past inputs only
C) Future inputs
D) Noise -
IIR filter uses—
A) No feedback
B) Feedback
C) Sampling only
D) Modulation -
Stability of FIR is—
A) Unstable
B) Always stable
C) Random
D) Conditional -
Digital filter implementation uses—
A) Hardware only
B) Software
C) Mechanical
D) Optical -
Filter cutoff frequency is defined at—
A) 0 dB
B) -3 dB
C) +3 dB
D) 1 dB -
Band reject filter is also called—
A) Notch filter
B) LPF
C) HPF
D) BPF -
Filter order affects—
A) Gain
B) Sharpness
C) Noise
D) Power -
Butterworth filter has—
A) Ripple
B) Flat response
C) Zero output
D) Noise -
Chebyshev filter has—
A) Ripple
B) Flat response
C) No bandwidth
D) DC only -
Elliptic filter is—
A) Most selective
B) Least selective
C) Flat
D) Random -
Analog filter uses—
A) ADC
B) RC components
C) Software
D) DSP -
Digital filter uses—
A) Capacitors only
B) Algorithms
C) Inductors
D) Diodes -
Filter removes—
A) Signal
B) Noise
C) Carrier
D) Phase -
LPF passes—
A) High frequency
B) Low frequency
C) Noise only
D) DC only -
HPF passes—
A) Low frequency
B) High frequency
C) Noise only
D) DC only -
BPF passes—
A) All frequency
B) One band
C) No frequency
D) Noise -
Notch filter rejects—
A) All frequency
B) Specific frequency
C) DC only
D) Noise only -
FIR filter is always—
A) Causal
B) Stable
C) Unstable
D) Analog -
IIR filter is computationally—
A) Heavy
B) Light
C) Zero cost
D) Random
181–200: Digital Communication & Misc
-
ASK stands for—
A) Amplitude Shift Keying
B) Analog Signal Keying
C) Automatic Signal Keying
D) Audio Signal Keying -
FSK stands for—
A) Frequency Shift Keying
B) Fast Signal Keying
C) Free Signal Keying
D) Fixed Signal Keying -
PSK stands for—
A) Phase Shift Keying
B) Power Signal Keying
C) Pulse Signal Keying
D) Partial Signal Keying -
QPSK uses—
A) 1 bit
B) 2 bits
C) 3 bits
D) 4 bits -
Bit rate is measured in—
A) Hz
B) bps
C) Watt
D) Volt -
Baud rate is—
A) Bits per second
B) Symbols per second
C) Frequency
D) Power -
Channel capacity depends on—
A) Noise only
B) Bandwidth & SNR
C) Power only
D) Frequency only -
Shannon theorem relates to—
A) Noise
B) Channel capacity
C) Filtering
D) Sampling -
Error detection uses—
A) Filter
B) Parity bit
C) Modulation
D) Carrier -
Error correction uses—
A) Coding
B) Filtering
C) Amplifier
D) Oscillator -
Line coding is used in—
A) Analog system
B) Digital system
C) FM
D) AM -
NRZ stands for—
A) Non Return to Zero
B) Noise Reduction Zone
C) No Return Zone
D) Normal Return Zero -
RZ stands for—
A) Return to Zero
B) Random Zone
C) Rate Zero
D) Response Zero -
Multiplexing combines—
A) One signal
B) Multiple signals
C) Noise
D) Carrier -
TDM uses—
A) Time slots
B) Frequency bands
C) Power levels
D) Noise levels -
FDM uses—
A) Time
B) Frequency
C) Power
D) Phase -
Communication channel can be—
A) Wired
B) Wireless
C) Optical
D) All -
Noise in channel is—
A) Helpful
B) Undesired
C) Carrier
D) Signal -
Attenuation reduces—
A) Signal strength
B) Noise
C) Bandwidth
D) Frequency -
Communication system goal is—
A) Noise increase
B) Signal transmission
C) Filtering only
D) Power loss
✅ Answer Key (001–200)
1-B, 2-C, 3-B, 4-B, 5-C, 6-B, 7-B, 8-A, 9-C, 10-A
11-B, 12-B, 13-B, 14-C, 15-B, 16-A, 17-B, 18-B, 19-A, 20-B
21-B, 22-B, 23-C, 24-B, 25-B, 26-B, 27-C, 28-A, 29-A, 30-B
31-B, 32-B, 33-A, 34-B, 35-A, 36-B, 37-A, 38-A, 39-B, 40-A
41-B, 42-B, 43-B, 44-A, 45-A, 46-A, 47-B, 48-A, 49-A, 50-A
51-A, 52-B, 53-D, 54-B, 55-A, 56-D, 57-A, 58-C, 59-A, 60-A
61-B, 62-B, 63-A, 64-B, 65-B, 66-A, 67-B, 68-A, 69-B, 70-B
71-A, 72-A, 73-B, 74-B, 75-B, 76-A, 77-B, 78-A, 79-D, 80-A
81-B, 82-B, 83-B, 84-A, 85-A, 86-B, 87-A, 88-B, 89-D, 90-B
91-A, 92-B, 93-A,
94-B, 95-A, 96-A, 97-A, 98-A,
99-A, 100-A
101-C, 102-A, 103-B, 104-A, 105-B, 106-B, 107-A, 108-C, 109-B, 110-B
111-A, 112-B, 113-A, 114-C, 115-A, 116-A, 117-B, 118-B, 119-A, 120-C
121-B, 122-B, 123-A, 124-A, 125-A, 126-B, 127-A, 128-B, 129-A, 130-B
131-A, 132-B, 133-A, 134-B, 135-B, 136-C, 137-B, 138-B, 139-B, 140-B
141-B, 142-B, 143-B, 144-B, 145-A, 146-A, 147-B, 148-B, 149-B, 150-A
151-B, 152-A, 153-A, 154-B, 155-B, 156-B, 157-B, 158-A, 159-A, 160-B
161-B, 162-B, 163-B, 164-B, 165-B, 166-B, 167-A, 168-B, 169-B, 170-A
171-A, 172-B, 173-B, 174-B, 175-B, 176-B, 177-B, 178-B, 179-B, 180-A
181-A, 182-A, 183-A, 184-B, 185-B, 186-B, 187-B, 188-B, 189-B, 190-A
191-B, 192-A, 193-A, 194-B,
195-A, 196-B, 197-D,
198-B, 199-A, 200-B
