Principles of Electronic Communication
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Principles of Electronic Communication
English 49 leveled MCQs Free
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5 marks Long answer
Draw at least 8 flat top PAM, PWM and PPM samples using one cycle of a sine wave as the modulating signal.
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Draw samples showing modulation types with sine wave.
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5 marks Long answer
Explain the sampling theorem and how it is used in communications.
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The sampling theorem states that a signal can be perfectly reconstructed if sampled at twice its maximum frequency.
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5 marks Long answer
From 4 (a). above, redraw the PAM signals as: (i). Impulses (ii). Natural samples
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Redraw PAM signals as impulse and natural samples.
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5 marks Long answer
What causes aliasing? Draw the appropriate domain diagrams to illustrate aliasing and over-sampling.
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Aliasing occurs when a signal is sampled below its Nyquist rate.
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5 marks Long answer
What is interpolation? The positive and negative halves of a sine are represented by 4 PAM samples each. Perform interpolation such that there are five times more samples transmitted.
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Interpolation increases sample density by estimating intermediate values.
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5 marks Long answer
A sine wave has peak values at ±5V. divide the space into (i). 10 uniform (ii). More than 10 non-uniform quantization levels.
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10 uniform levels yield equal spacing; non-uniform levels vary spacing.
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5 marks Long answer
Draw a block diagram showing a basic PCM system.
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Diagram showing PCM components: sampler, quantizer, encoder.
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5 marks Long answer
Explain the basic working principles of Pulse Code Modulation.
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PCM converts analog signals to digital by sampling, quantizing, and encoding.
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5 marks Long answer
PAM analog sample values are 1, 6, 3.4, 5.2 and 8.8 volts respectively. Uniform quantization levels are set at integral values. Calculate QEs for all samples and express them in percentages. Which sample has the worst QE%?
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Calculate QEs and identify the sample with the highest error.
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5 marks Long answer
Encode 100011110011 into the three different categories of NRZ and RZ formats.
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Provide NRZ and RZ encoding representations for the binary sequence.
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5 marks Long answer
Briefly explain the basic concepts of delta modulation.
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Delta modulation encodes the difference between successive samples.
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5 marks Long answer
How does slope overload and granular noise occur in delta modulation? Draw diagrams to illustrate.
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Slope overload occurs when the signal changes faster than the modulator can track.
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5 marks Long answer
What is ISI? Transmitted voltages are +5, -5, -5 and +5 volts respectively. Draw diagrams to illustrate the impact of ISI.
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ISI occurs when symbols interfere, causing misinterpretation.
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5 marks Long answer
What are the different means used to control ISI?
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Techniques include equalization, pulse shaping, and coding.
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5 marks Long answer
Write a brief introduction to DSSS. What are the benefits of DSSS?
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DSSS spreads the signal over a wide bandwidth, providing resistance to interference.
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5 marks Long answer
The message is 10001111. Generate your own PN sequence to explain the working of DSS at the transmitter and receiver.
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Demonstrate DSSS encoding and decoding using a PN sequence.
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5 marks Long answer
The message is 10001111. Plot the BPSK waveform.
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Plot the BPSK waveform corresponding to the binary message.
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5 marks Long answer
Explain the implementation of DSSS with coherent BPSK.
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DSSS with coherent BPSK uses a PN sequence to modulate the message signal.
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5 marks Long answer
Use the message in (b). along with a PN sequence of your choice to illustrate DSSS with coherent BPSK.
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Illustrate the DSSS process with BPSK modulation using the given message.
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5 marks Long answer
With the help of appropriate diagrams, explain the working of the FHSS system.
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FHSS rapidly changes frequencies to avoid interference and enhance security.
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4 marks Medium answer
Fc = 500 KHz, Fm1 = 8KHz and Fm2 = 15KHz. Calculate USB, LSB, bandwidth and draw the AM spectrum showing all components.
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USB = 508 KHz, LSB = 492 KHz, Bandwidth = 30 KHz.
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4 marks Medium answer
Explain the working of any one: (i). AM diode modulator (ii). AM diode demodulator
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An AM diode modulator combines the carrier and message signals to produce an AM signal.
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4 marks Medium answer
Explain the working of the diode lattice balanced modulator.
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It uses a diode lattice to modulate the carrier signal with the message signal.
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4 marks Medium answer
Explain the working of anyone of these SSB systems: (i). Filter (ii). Phase-Shift
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Filter SSB removes one sideband using a bandpass filter.
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4 marks Medium answer
Pc = 1KW and m = 0.8. Calculate PT for DSBFC, DSBSC, SSBFC and SSBSC.
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PT for DSBFC = 1.44 KW, DSBSC = 1.0 KW, SSBFC = 0.64 KW, SSBSC = 0.8 KW.
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4 marks Medium answer
List four advantages and four disadvantages of FHSS.
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Advantages: robustness, security; Disadvantages: complexity, limited bandwidth.
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3 marks Medium answer
List two advantages of translation and modulation of signals.
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Increased range and reduced noise interference.
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3 marks Medium answer
Translate Fm = 10KHz to 1000KHz using the cosine function.
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Use $A \cos(2 \pi F_c t) \cos(2 \pi F_m t)$.
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3 marks Medium answer
What is achieved by suppressing the carrier in AM?
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It reduces power consumption and increases efficiency.
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3 marks Medium answer
What must be the minimum number of samples taken per second if a signal has a maximum frequency of 3.5 KHz?
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At least 7,000 samples per second.
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3 marks Medium answer
List three applications of DSSS.
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Applications include GPS, CDMA, and wireless LANs.
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2 marks Short answer
In an AM process, m = 0.65 and Vm = 13V. Find Vc.
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Vc = Vm * m = 8.45V
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2 marks Short answer
Calculate the frequency of a signal if it has a time period of 10 milli-seconds.
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Frequency = 100 Hz
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2 marks Short answer
How many samples per second must be transmitted if the source signal is a sine wave of 2.5 KHz?
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5,000 samples per second
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2 marks Short answer
The spacing between any 2 successive quantization levels is Δ. The minimum voltage is -5V, maximum is +5V. How many quantization levels are there if only integral values are used?
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11 quantization levels
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2 marks Short answer
How is a NRZ binary 1 different from a RZ binary 1?
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NRZ maintains a constant level for the entire bit duration, while RZ returns to zero before the next bit.
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2 marks Short answer
What is a base band signal?
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A base band signal is a signal that has not been modulated and occupies the frequency range from 0 Hz to a certain maximum frequency.
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2 marks Short answer
What is a modulated signal?
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A modulated signal is one that has been altered in amplitude, frequency, or phase to encode information.
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2 marks Short answer
List any one advantage of line coding.
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Line coding helps in synchronization of the transmitter and receiver.
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2 marks Short answer
What is Nyquist criterion for distortion free baseband transmission?
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The Nyquist criterion states that the sampling rate must be at least twice the maximum frequency.
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2 marks Short answer
What is processing gain?
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Processing gain is the improvement in signal-to-noise ratio achieved by spreading the signal.
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2 marks Short answer
List two applications of FHSS.
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Applications include Bluetooth and military communications.
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1 marks Short answer
A signal must be translated to a (lower/ higher) frequency in electronic communications. (Tick the correct option)
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higher
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1 marks Short answer
In FM generation, (only a single pair/ multiple pairs) of sidebands will be produced. (Tick the correct option)
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multiple pairs
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1 marks Short answer
A balanced modulator is used to remove the carrier signal. (T/F)
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True
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1 marks Short answer
Suppressing one of the SBs in Am will save (power consumption/ bandwidth). (Tick the correct option)
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bandwidth
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1 marks Short answer
A pulse train can produce only one of these signals: (AM/FM/ PCM). (Tick the correct option)
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PCM
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1 marks Short answer
Insufficient number of samples are transmitted. The resulting error is called (aliasing/ interpolation). (Tick the correct option)
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aliasing
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1 marks Short answer
ISI may cause a binary 1 to look like a binary (0/1). (Tick the correct option)
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