McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Computer Science Engineering (CSE) .
| 101. |
In which waveform logic 1 is represented by equal amplitude alternating pulses? |
| A. | unipolar rz |
| B. | bipolar rz |
| C. | rz-ami |
| D. | manchester coding |
| Answer» C. rz-ami | |
| Explanation: in rz-ami logic 1 is represented by equal amplitude alternating pulses and logic 0 is represented by the absence of a pulse. | |
| 102. |
The signals which are obtained by encoding each quantized signal into a digital word is called as |
| A. | pam signal |
| B. | pcm signal |
| C. | fm signal |
| D. | sampling and quantization |
| Answer» B. pcm signal | |
| Explanation: pulse code modulation is the name for the class of signals which are obtained by encoding the quantized signals into a digital word. | |
| 103. |
The length of the code-word obtained by encoding quantized sample is equal to |
| A. | l=log(to the base 2)l |
| B. | l=log(to the base 10)l |
| C. | l=2log(to the base 2)l |
| D. | l=log(to the base 2)l/2 |
| Answer» A. l=log(to the base 2)l | |
| Explanation: the quantized sample which are digitally encoded into l bit value code- word. the length l can be calculated as l=log(to the base 2)l. | |
| 104. |
In PCM encoding, quantization level varies as a function of |
| A. | frequency |
| B. | amplitude |
| C. | square of frequency |
| D. | square of amplitude |
| Answer» B. amplitude | |
| Explanation: in linear pcm the quantization levels are uniform. but in normal pcm encoding the quantization level vary according to the amplitude, based of a-law of myu-law. | |
| 105. |
What is bit depth? |
| A. | number of quantization level |
| B. | interval between two quantization levels |
| C. | number of possible digital values to represent each sample |
| D. | none of the mentioned |
| Answer» C. number of possible digital values to represent each sample | |
| Explanation: one of the properties of pcm signal which determines its stream fidelity is bit depth which is the number of possible digital values that can be used to represent each sample. | |
| 106. |
Choosing a discrete value that is near but not exactly at the analog signal level leads to |
| A. | pcm error |
| B. | quantization error |
| C. | pam error |
| D. | sampling error |
| Answer» B. quantization error | |
| Explanation: one of the limitations of pcm is quantization error which occurs when we choose a discrete value at some near by value and not at the analog signal level. | |
| 107. |
In PCM the samples are dependent on |
| A. | time |
| B. | frequency |
| C. | quanization leavel |
| D. | interval between quantization level |
| Answer» A. time | |
| Explanation: the samples depend on time,an accurate clock is required for accurate reproduction. | |
| 108. |
DPCM encodes the PCM values based on |
| A. | quantization level |
| B. | difference between the current and predicted value |
| C. | interval between levels |
| D. | none of the mentioned |
| Answer» B. difference between the current and predicted value | |
| Explanation: differential pcm encodes the pcm value based on the difference between the previous sample and the present sample value. | |
| 109. |
Delta modulation uses bits per sample. |
| A. | one |
| B. | two |
| C. | four |
| D. | eight |
| Answer» A. one | |
| Explanation: delta modulation is used for analog to digital conversion and vice versa. it is a simple form of dpcm. its uses 1 bit per sample. it also depends on the difference between the current and previous sample values. | |
| 110. |
Sample resolution for LPCM bits per sample. |
| A. | 8 |
| B. | 16 |
| C. | 24 |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: common sampling resolution for lpcm are 8, 16, 20, 24 bits per sample. | |
| 111. |
Adaptive DPCM is used to |
| A. | increase bandwidth |
| B. | decrease bandwidth |
| C. | increase snr |
| D. | none of the mentioned |
| Answer» B. decrease bandwidth | |
| Explanation: adaptive dpcm is used to decrease required bandwidth for the given snr. | |
| 112. |
Vocoders analyse the speech signals at |
| A. | transmitter |
| B. | receiver |
| C. | channel |
| D. | if filter |
| Answer» A. transmitter | |
| Explanation: vocoders are a class of speech coding systems. they analyse the speech signal at the transmitter. and then transmit the parameters derived from the analysis. | |
| 113. |
Vocoders the voice at the receiver. |
| A. | analyse |
| B. | synthesize |
| C. | modulate |
| D. | evaluate |
| Answer» B. synthesize | |
| Explanation: vocoders synthesize the voice at the receiver. all vocoder systems attempt to model the speech generation process as a dynamic system and try to quantify certain physical constraints of the system. | |
| 114. |
6 CHANNEL VOCODER |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: vocoders are much more complex than the waveform coders. they can achieve very high economy in transmission bit rate but are less robust. | |
| 115. |
Which of the following is not a vocoding system? |
| A. | linear predictive coder |
| B. | channel vocoder |
| C. | waveform coder |
| D. | formant vocoder |
| Answer» C. waveform coder | |
| Explanation: waveform coder is not a vocoding system. lpc (linear predictive coding) is the most popular vocoding system. other vocoding systems are channel vocoder, formant vocoder, cepstrum vocoder etc. | |
| 116. |
Which of the following pronunciations lead to voiced sound? |
| A. | ‘f’ |
| B. | ‘s’ |
| C. | ‘sh’ |
| D. | ‘m’ |
| Answer» D. ‘m’ | |
| Explanation: voiced sounds are ‘m’, ‘n’ and ‘v’ pronounciations. they are a result of quasiperiodic vibrations of the vocal chord. | |
| 117. |
Channel vocoders are the time domain vocoders. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: channel vocoders are frequency domain vocoders. they determine the envelope of the speech signal for a number of frequency bands and then sample, encode and multiplex these samples with the encoded outputs of the other filters. | |
| 118. |
is often called the formant of the speech signal. |
| A. | pitch frequency |
| B. | voice pitch |
| C. | pole frequency |
| D. | central frequency |
| Answer» C. pole frequency | |
| Explanation: the pole frequencies correspond to the resonant frequencies of the vocal tract. they are often called the formants of the speech signal. for adult speakers, the formants are centered around 500 hz, 1500 hz, 2500 hz and 3500 hz. | |
| 119. |
Formant vocoders use large number of control signals. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: formant vocoders use fewer control signals. therefore, formant vocoders can operate at lower bit rates than the channel vocoder. instead of transmitting the power spectrum envelope, formant vocoders attempt to transmit the position of peaks of spectral envelope. | |
| 120. |
Cepstrum vocoder uses |
| A. | wavelet transform |
| B. | inverse wavelet transform |
| C. | cosine transform |
| D. | inverse fourier transform |
| Answer» D. inverse fourier transform | |
| Explanation: cepstrum vocoders use inverse fourier transform. it separates the excitation and vocal tract spectrum by fourier transforming spectrum to produce the cepstrum of the signal. | |
| 121. |
The real part of an antenna’s input impedance is due to |
| A. | swr |
| B. | radiated signal |
| C. | reflected signal |
| D. | refracted signal |
| Answer» B. radiated signal | |
| Explanation: in antenna impedance, impedance related the voltage and current at the input of the antenna. the real part of antenna impedance represents power that is either radiated away or absorbed within the antenna and the imaginary part of antenna impedance represents power that is stored in the near field of antenna. | |
| 122. |
What is the other name for half-wave dipole antenna? |
| A. | helical antenna |
| B. | isotropic antenna |
| C. | hertz antenna |
| D. | maxwell antenna |
| Answer» C. hertz antenna | |
| Explanation: the hertz antenna is also known as half wave dipole antenna. it consists of two straight collinear conductors of equal length separated by a small feeding gap. | |
| 123. |
Measured on the ground, the field strength of a horizontally polarized half wave dipole antenna is strongest |
| A. | in one direction |
| B. | in two directions |
| C. | depends on the number of elements |
| D. | depends on the shape of antenna |
| Answer» B. in two directions | |
| Explanation: as the name suggests, half wave dipole is half wavelength long. this antenna has the shortest resonant length that can be used for a resonant dipole. the field strength of a horizontally polarized half wave dipole antenna is strongest in two directions. | |
| 124. |
When an antenna radiates more energy in one direction than in other directions, it is called |
| A. | selectivity |
| B. | directivity |
| C. | active antenna |
| D. | resonance |
| Answer» B. directivity | |
| Explanation: when an antenna radiates more energy in one direction than in other directions is called directivity. an antenna that radiates equally in all directions has effectively zero directionality, and the directivity of this type of antenna should be 1 (or 0db). | |
| 125. |
What is the full form of ERP? |
| A. | effective radiated power |
| B. | effective reflected power |
| C. | equivalent radiated power |
| D. | equivalent reflected power |
| Answer» A. effective radiated power | |
| Explanation: erp stands for effective radiated power. effective radiated power (erp) is always given with respect to a certain direction. | |
| 126. |
The polarization of plane waves received from satellite is changed by |
| A. | faraday rotation |
| B. | gamma rays |
| C. | helical rotation |
| D. | distance travelled |
| Answer» A. faraday rotation | |
| Explanation: generally for satellite communication circular polarization is required. the polarization received by waves from satellite is changed by faraday rotation. | |
| 127. |
What is the input impedance to a lossless antenna, at resonance? |
| A. | infinite |
| B. | 0 |
| C. | resistive |
| D. | capacitive |
| Answer» C. resistive | |
| Explanation: in antenna impedance, impedance related the voltage and current at the input of the antenna. the real part of antenna impedance represents power that is either radiated away or absorbed within the antenna and the imaginary part of antenna impedance represents power that is stored in the near field of antenna. the input impedance of a lossless antenna is purely resistive. | |
| 128. |
TDMA stands for |
| A. | time division multiple access |
| B. | time domain multiple access |
| C. | time division mutual access |
| D. | time domain mutual access |
| Answer» A. time division multiple access | |
| Explanation: tdma stands for time division multiple access. it can be seen as a channel access method for shared-medium networks. | |
| 129. |
Which term is used when signals move from one line to another? |
| A. | path switching |
| B. | space switching |
| C. | line switching |
| D. | cross-point switching |
| Answer» B. space switching | |
| Explanation: space switching is the used term for signals moving from one line to another. | |
| 130. |
PSK stands for Pulse Shift Keying. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: psk stands for phase shift keying. it is a modulation scheme that conveys information by changing the phase of carrier. | |
| 131. |
Which term is used for moving PCM samples from one time slot to another? |
| A. | time switching |
| B. | space switching |
| C. | phase switching |
| D. | frequency switching |
| Answer» A. time switching | |
| Explanation: time switching is the used term for moving pcm samples moving from one time slot to another. | |
| 132. |
Power can be coupled into or out of a waveguide with a magnetic field probe. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: a waveguide is a line through which electromagnetic waves are passed for | |
| 133. |
What is the full form of LOS? |
| A. | level of signal |
| B. | line of sight |
| C. | loss of signal |
| D. | level of sight |
| Answer» B. line of sight | |
| Explanation: line of sight is a line between two points. it is a straight path between a transmitting antenna and a receiving antenna. | |
| 134. |
How we can define the satisfactory performance of an analog microwave system? |
| A. | carrier to noise ratio that exceeds a given value |
| B. | carrier to noise ratio that is below a given value |
| C. | an erp value that exceeds a given value |
| D. | an erp value that is below a given value |
| Answer» A. carrier to noise ratio that exceeds a given value | |
| Explanation: we can measure performance of an analog microwave system by calculating the carrier to noise ratio that exceeds a given value. it gives the signal to noise ratio. | |
| 135. |
RGB stands for |
| A. | red green brown |
| B. | red green black |
| C. | red gold blue |
| D. | red green blue |
| Answer» D. red green blue | |
| Explanation: rgb stands for red green blue. it is an additive color model in which red, green and blue light intensity and different shades are added together in various ways to reproduce a broad variety of colors. | |
| 136. |
How many lines are there in an NTSC signal? |
| A. | 1024 |
| B. | 1856 |
| C. | 625 |
| D. | 525 |
| Answer» D. 525 | |
| Explanation: ntsc stands for national television system committee. in ntsc, it is standardized fixed that it has total 525 lines. | |
| 137. |
Luminance refers to |
| A. | contrast |
| B. | diffusion |
| C. | brightness |
| D. | aperture |
| Answer» C. brightness | |
| Explanation: luminance refers to brightness. it is a photometric measure of luminous intensity per unit area of light travelling in a given direction. | |
| 138. |
Linear modulation techniques are not bandwidth efficient. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: linear modulation techniques are bandwidth efficient. they are used in wireless communication systems when there is an increasing demand to accommodate more and more users within a limited spectrum. | |
| 139. |
Which of the following is not a linear modulation technique? |
| A. | oqpsk |
| B. | π/4 qpsk |
| C. | fsk |
| D. | bpsk |
| Answer» C. fsk | |
| Explanation: oqpsk, π/4 qpsk and bpsk are the most popular linear modulation techniques. they have very good spectral efficiency. however, fsk is an non-linear modulation technique. | |
| 140. |
In BPSK, the of constant amplitude carrier signal is switched between two values according to the two possible values. |
| A. | amplitude |
| B. | phase |
| C. | frequency |
| D. | angle |
| Answer» B. phase | |
| Explanation: in binary phase shift keying (bpsk), the phase of a constant amplitude carrier signal is switched between two possible values m1 and m2. these two values corresponds to binary 1 and 0 respectively. | |
| 141. |
BPSK uses non-coherent demodulator. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: bpsk uses coherent or synchronous demodulation. it requires the information about the phase and frequency of the carrier be available at the receiver. | |
| 142. |
DPSK uses coherent form of PSK. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: differential phase shift keying uses noncoherent form of phase shift keying. noncoherent form avoids the need for a coherent reference signal at the receiver. | |
| 143. |
In DPSK system, input signal is differentially encoded and then modulated using a modulator. |
| A. | amplitude |
| B. | frequency |
| C. | bpsk |
| D. | qpsk |
| Answer» C. bpsk | |
| Explanation: in dpsk system, input binary sequence is first differentially encoded and then modulated using a bpsk modulator. the differentially encoded sequence is generated | |
| 144. |
QPSK has the bandwidth efficiency of BPSK. |
| A. | twice |
| B. | same |
| C. | half |
| D. | four times |
| Answer» A. twice | |
| Explanation: quadrature phase shift keying (qpsk) has twice the bandwidth of bpsk. it is because two bits are transmitted in a single modulation symbol. the phase of the carrier takes on one of the four equally spaced values, where each value of phase corresponds to a unique pair of message bit. | |
| 145. |
QPSK provides twice the bandwidth efficiency and energy efficiency as compared to BPSK. |
| A. | twice |
| B. | half |
| C. | same |
| D. | four times |
| Answer» C. same | |
| Explanation: the bit error probability of qpsk is identical to bpsk but twice as much data can be sent in the same bandwidth. thus, when compared to bpsk, qpsk provides twice the spectral efficiency with exactly the same efficiency. | |
| 146. |
What is the full form of OQPSK? |
| A. | optical quadrature phase shift keying |
| B. | orthogonal quadrature pulse shift keying |
| C. | orthogonal quadrature phase shift keying |
| D. | offset quadrature phase shift keying |
| Answer» D. offset quadrature phase shift keying | |
| Explanation: oqpsk stands for offset quadrature phase shift keying. it is a modified form of qpsk which is less susceptible to deleterious effects and supports more efficient amplification. oqpsk is sometimes also called staggered qpsk. | |
| 147. |
The bandwidth of OQPSK is to QPSK. |
| A. | identical |
| B. | twice |
| C. | half |
| D. | four times |
| Answer» A. identical | |
| Explanation: the spectrum of an oqpsk signal is identical to that of qpsk signal. hence, both signals occupy the same bandwidth. the staggered alignment of the even and odd bit streams in oqpsk signal does not change the nature of spectrum. | |
| 148. |
QPSK signals perform better than OQPSK in the presence of phase jitter. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: oqpsk signal perform better than qpsk in the presence of phase jitter. it is due to the presence of noisy reference signal at the receiver. | |
| 149. |
Which of the following is not a detection technique used for detection of π/4 QPSK signals? |
| A. | baseband differential detection |
| B. | if differential detection |
| C. | fm discriminator detection |
| D. | envelope detection |
| Answer» D. envelope detection | |
| Explanation: there are various types of detection techniques used for the detection of π/4 qpsk signals. they include baseband differential detection, if differential detection and fm discriminator detection. | |
| 150. |
Which of the following is a combined linear and constant envelope technique? |
| A. | mpsk |
| B. | psk |
| C. | bpsk |
| D. | qpsk |
| Answer» A. mpsk | |
| Explanation: m-ary phase shift keying (mpsk) is a combined linear and constant envelope technique. it is a part of m-ary modulation techniques. these modern modulation techniques exploit the fact that digital baseband data may be sent by varying both the envelope and phase of an rf carrier. | |
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