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Correct choice is (c) At & above the Nyquist RATE

To ELABORATE: The signal can be RECONSTRUCTED from the sampled version at or above Nyquist rate USING simple LOW pass filtering.

The correct choice is (a) Low pass filtering

Best explanation: Original SIGNAL can be obtained from its SAMPLED version by USING low pass filtering.

Correct choice is (b) Down sampling

Best explanation: DECREASING the data rate is CALLED as down sampling and INCREASING the data rate is called as up sampling.

The correct choice is (C) Up-sampling & Down-sampling

The explanation is: Up-sampling REQUIRES low PASS filter after increasing the DATA rate and down-sampling requires low pass filter before decimation.

The CORRECT choice is (B) Gives sharp output

Explanation: ARMA filter gives sharp output but sampling cannot be done in REAL TIME.

The CORRECT answer is (c) Linear phase & Delayed symmetric filter

The best explanation: Linear phase filter or delayed symmetric filter does not have sharp output but sampling can be DONE in real time.

The CORRECT answer is (b) DIGITAL signal

To explain I would say: Mixing of digital signals are EASIER than that of mixing analog signals.

The CORRECT choice is (b) LARGER the number of DISCRETE amplitudes

For EXPLANATION I would say: Larger the number of discrete amplitudes, finer will be the quantization.

Correct CHOICE is (d) All of the mentioned

Easy explanation: The three CASES of sampling are IDEAL impulse sampling, sampling with rectangular pulses and FLAT topped sampling.

The correct OPTION is (c) Redundancy & AVERAGE bit rate

To explain: Source CODING reduces both average bit rate and reduces redundancy.

The CORRECT option is (c) Transistors & Valves

Easy explanation: Shot NOISE OCCURS in both valves and transistors.

The correct CHOICE is (d) All of the mentioned

Explanation: Source encoding includes a SAMPLING of continuous TIME signals, quantization of continuous valued signals and compression of those SOURCES.

The CORRECT ANSWER is (b) DETERMINISTIC signal

Easiest EXPLANATION: Deterministic SIGNALS are function of time.

Correct option is (c) REDISTRIBUTION of spectral DENSITY & to FAVOR LOW frequencies

Best explanation: Each bit can be independently DETECTED in-spite of strong correlation and this provides redistribution of spectral density and also favors low frequencies.

Right ANSWER is (d) j-2

To elaborate: In polybinary SIGNALLING method the present BINARY digit of the sequence is formed from the modulo-2 ADDITION of the j-2 preceding DIGITS of the sequence and the present digit.

Correct CHOICE is (b) Polybinary signalling

Best EXPLANATION: If more than THREE levels are introduced in duobinary signalling technique the bandwidth efficiency INCREASES This METHOD is called as polybinary signalling.

Correct OPTION is (C) EXOR-ed

For explanation I would say: To avoid error propogation precoding method is used. In this each bit is ENCODED individually WITHOUT having any effect due to its PRIOR bit or decisions.

Right choice is (a) Amplitude

To explain I would SAY: In PPM waveform DELAYING or advancing of PULSE is done. In PDM the pulse WIDTH is varied. Thus in both the cases amplitude is maintained constant.

Correct option is (a) NRZ

Best EXPLANATION: NRZ WAVEFORMS has better ERROR performance than RZ signal waveforms.

Right option is (c) NUMBER of quantization levels

For explanation: Each analog sample is transformed into PCM WORD made up of a group of bits. The PCM word SIZE can be described by number of quantization levels ALLOWED for each sample.

The correct option is (b) Multilevel signalling

To explain I would say: The TRANSMISSION BANDWIDTH REQUIRED for binary DIGITAL waveforms is large. To reduce the bandwidth, multilevel signalling method can be USED.

Correct choice is (d) All of the mentioned

For explanation I would SAY: When we pulse modulate NON BINARY signals we get M-ary waveform. Some of the examples of M-ary waveforms are PAM, PPM, PDM.

Right answer is (a) Bi-p-L

For EXPLANATION I would SAY: In bi-phase-level one is represented by HALF BIT WIDE pulse positioned during the first half and zero is represented by half bit wide pulse positioned in the second half.

Correct option is (d) DUOBINARY

Explanation: Duobinary SCHEME does error detection WITHOUT introducing any additional error bits into the DATA sequence.

The correct answer is (a) MANCHESTER coding

Easiest EXPLANATION: In manchester coding transition occurs in the middle of every BIT interval. THUS it has a feature of clocking.

Correct option is (d) All of the mentioned

The EXPLANATION is: Some of the FIELDS where PHASE encoded waveforms is being used are optical communication, magnetic tape recording, SATELLITE telemetry etc.

Right choice is (C) RZ-AMI

Best explanation: In RZ-AMI LOGIC 1 is represented by equal amplitude alternating PULSES and logic 0 is represented by the absence of a pulse.

Correct choice is (a) Unipolar RZ

To EXPLAIN I would say: In unipolar RZ WAVEFORM, LOGIC 1 is represented by half bit wide pulse and logic 0 is represented by the absence of a pulse.

The CORRECT choice is (b) NRZ-M

To explain: NRZ-S is a complement of NRZ-M. LOGIC 0 is represented by a CHANGE in voltage LEVEL and logic 1 is represented as no change in voltage level.