Generic selectors
Exact matches only
Search in title
Search in content
Search in posts
Search in pages
Filter by Categories
nmims post
Objective Type Set
Online MCQ Assignment
Question Solution
Solved Question
Uncategorized

Multiple choice question for engineering

Set 1

1. What does UART stand for?
a) universal asynchronous receiver transmitter
b) unique asynchronous receiver transmitter
c) universal address receiver transmitter
d) unique address receiver transmitter

View Answer

Answer: a [Reason:] The UART or universal asynchronous receiver transmitter is used for the data transmission at a predefined speed or baud rate.

2. How is data detected in a UART?
a) counter
b) timer
c) clock
d) first bit

View Answer

Answer: c [Reason:] The data can be detected by the local clock reference which is generated from the baud rate generator.

3. Which of the signal is set to one, if no data is transmitted?
a) READY
b) START
c) STOP
d) TXD

View Answer

Answer: d [Reason:] The TXD signal goes to logic one, when no data is transmitted. When data transmits, it sets to logic zero.

4. What rate can define the timing in the UART?
a) bit rate
b) baud rate
c) speed rate
d) voltage rate

View Answer

Answer: b [Reason:] The timing is defined by the baud rate in which both the transmitter and receiver are used. The baud rate is supplied by the counter or an external timer called baud rate generator which generate a clock signal.

5. How is baud rate supplied?
a) baud rate voltage
b) external timer
c) peripheral
d) internal timer

View Answer

Answer: b [Reason:] The baud rate is supplied by the counter or an external timer called baud rate generator which generate a clock signal.

6. Which is the most commonly used UART?
a) 8253
b) 8254
c) 8259
d) 8250

View Answer

Answer: d [Reason:] The Intel 8253, 8254 and 8259 are timers whereas Intel 8250 is a UART which is commonly used.

7. Which company developed 16450?
a) Philips
b) Intel
c) National semiconductor
d) IBM

View Answer

Answer: c [Reason:] The Intel 8250 is replaced by the 16450 and 16550 which are developed by the National Semiconductors. 16450 is a chip which can combines all the PC’s input output devices into a single piece of silicon.

8. What does ADS indicate in 8250 UART?
a) address signal
b) address terminal signal
c) address strobe signal
d) address generating signal

View Answer

Answer: b [Reason:] The ADS is address strobe signal and is working as active low in 8250 UART. The ADS signal is used to latch the address and chip select signals while a processor access.

9. Which of the following signals are active low in the 8250 UART?
a) BAUDOUT
b) DDIS
c) INTR
d) MR

View Answer

Answer: a [Reason:] The BAUDOUT signal is active low whereas DDIS, INTR and MR are active high in the 8250 UART. BAUDOUT is the clock signal from the transmitter part of the UART. DDIS signal goes low when the CPU is reading data from the UART. INTR is the interrupt pin. MR is the master reset pin.

10. Which of the signal can control bus arbitration logic in 8250?
a) MR
b) DDIS
c) INTR
d) RCLK

View Answer

Answer: b [Reason:] DDIS signal goes low when the CPU is reading data from the UART and it also controls the bus arbitration logic.

Set 2

1. Slotted line is a transmission line configuration that allows the sampling of:
a) electric field amplitude of a standing wave on a terminated line
b) magnetic field amplitude of a standing wave on a terminated line
c) voltage used for excitation
d) current that is generated by the source

View Answer

Answer: a [Reason:] Slotted line allows the sampling of the electric field amplitude of a standing wave on a terminated line. With this device, SWR and the distance of the first voltage minimum from the load can be measured, from this data, load impedance can be found.

2. A slotted line can be used to measure _____ and the distance of _____________ from the load.
a) SWR, first voltage minimum
b) SWR, first voltage maximum
c) characteristic impedance, first voltage minimum
d) characteristic impedance, first voltage maximum

View Answer

Answer: a [Reason:] With a slotted line, SWR and the distance of the first voltage minimum from the load can be measured, from this data, load impedance can be found.

3. A modern device that replaces a slotted line is:
a) Digital CRO
b) generators
c) network analyzers
d) computers

View Answer

Answer: c [Reason:] Although slotted lines used to be the principal way of measuring unknown impedance at microwave frequencies, they have largely been superseded by the modern network analyzer in terms of accuracy, versatility and convenience.

4. If the standing wave ratio for a transmission line is 1.4, then the reflection coefficient for the line is:
a) 0.16667
b) 1.6667
c) 0.01667
d) 0.96

View Answer

Answer: a [Reason:] ┌= (SWR-1)/ (SWR+1). Substituting for SWR in the above equation for reflection co-efficient, given SWR is 1.4, reflection co-efficient is 0.16667.

5. If the reflection coefficient of a transmission line is 0.4, then the standing wave ratio is:
a) 1.3333
b) 2.3333
c) 0.4
d) 0.6

View Answer

Answer: b [Reason:] SWR= (1+┌)/ (1-┌). Where ┌ is the reflection co-efficient. Substituting for the reflection co-efficient in the equation, SWR is 2.3333.

6. Expression for ϴ means phase angle of the reflection co efficient r=|r|-e^jθ, the phase of the reflection co-efficient is:
a) θ=2π+2βLmin
b) θ=π+2βLmin
c) θ=π/2+2βLmin
d) θ=π+βLmin

View Answer

Answer: b [Reason:] here, θ is the phase of the reflection co-efficient. Lmin is the distance from the load to the first minimum. Since voltage minima repeat every λ/2, any multiple of λ/2 can be added to Lmin .

7. In the expression for phase of the reflection coefficient, Lmin stands for :
a) distance between load and first voltage minimum
b) distance between load and first voltage maximum
c) distance between consecutive minimas
d) distance between a minima and immediate maxima

View Answer

Answer: a [Reason:] Lmin is defined as the distance between the terminating load of a transmission line and the first voltage minimum that occurs in the transmission line due to reflection of waves from the load end due to mismatched termination.

8. If SWR=1.5 with a wavelength of 4 cm and the distance between load and first minima is 1.48cm, then the reflection coefficient is:
a) 0.0126+j0.1996
b) 0.0128
c) 0.26+j0.16
d) none of the mentioned

View Answer

Answer: a [Reason:] ┌= (SWR-1)/ (SWR+1). Substituting for SWR in the above equation for reflection co-efficient, magnitude of the reflection co-efficient is 0.2. To find θ, θ=π+2βLmin, substituting Lmin as 1.48cm, θ=86.4⁰. Hence converting the polar form of the reflection co-efficient into rectangular co-ordinates, reflection co-efficient is 0.0126+j0.1996.

9. If the characteristic impedance of a transmission line 50 Ω and reflection coefficient is 0.0126+j0.1996, then load impedance is:
a) 47.3+j19.7Ω
b) 4.7+j1.97Ω
c) 0.26+j0.16
d) data insufficient

View Answer

Answer: a [Reason:] ZL=Z0 (1+┌)/ (1-┌). Substituting the given values of reflection co-efficient and characteristic impedance, ZL is 47.3+j19.7Ω .

10. If the normalized load impedance of a transmission line is 2, then the reflection co-efficient is:
a) 0.33334
b) 1.33334
c) 0
d) 1

View Answer

Answer: a [Reason:] ZL=Z0 (1+┌)/ (1-┌), this is the expression for load impedance. Normalized load impedance is the ratio of load impedance to the characteristic impedance, taking ZLL/Z0 as 2, the reflection co-efficient is equal to 0.33334.

Set 3

1. If the third order input intercept point of a mixer is 13 dBm and if the mixer has a conversion loss of 6 dBm, then the third order intercept point at the output is:
a) 3 dBm
b) 7 dBm
c) 4 dBm
d) 2 dBm

View Answer

Answer: b [Reason:] Third order output intercept point is given by the relation OIP3=IIP3 (G). G is the conversion loss in the device. In dBm scale they have to be subtracted. Subtracting the given values, the output third order intercept point is 7 dBm.

2. In a coherent cascade network, if the third order intercept point of an amplifier is 158 mW and the third order intercept point of a mixer is 5 mW, with an insertion loss of 6 dB, then the third order intercept point of the coherent cascade is:
a) 2 mW
b) 4 mW
c) 4.4 mW
d) 5 mW

View Answer

Answer: c [Reason:] The third order intercept point of the cascade is given by the expression ((G2 (OIP3’)-1+ (OIP3’’)-1)-1. Substituting the values in the above expression for respective terms, the third order intercept point of the cascade is 4.4 mW.

3. In a non coherent cascade network, if the third order intercept point of an amplifier is 158 mW and the third order intercept point of a mixer is 5 mW, with an insertion loss of 6 dB, then the third order intercept point of the coherent cascade is:
a) 3 mW
b) 4.9 mW
c) 5.2 mW
d) 2 mW

View Answer

Answer: b [Reason:] The third order intercept point for a non coherent cascade network is given by ((G22 (OIP3’)-2+ (OIP3’’)-2)-2. Substituting the values in the above expression for respective terms, the third order intercept point of the cascade is 4.9 mW.

4. Inter modulation distortion occurs only in active non linear devices and they are the only source of inter modulation distortion.
a) True
b) False

View Answer

Answer: b [Reason:] It is also possible for inter modulation products to be generated by passive non linear effects in connectors, cables and antennas or almost every element where there is metal to metal contact. This effect is called passive inter modulation.

5. ________ is defined as the operating range for which a component or system has desirable characteristics.
a) Static range
b) Dynamic range
c) Characteristic gain
d) None of the mentioned

View Answer

Answer: b [Reason:] Dynamic range is defined as the operating range for which a component or system has desirable characteristics. For a power amplifier, this may be the power range that is limited at the low end by noise and at the high end by the compression point.

6. The expression for linear dynamic range is given by:
a) OP1 dB- No
b) OP1 dB/ No
c) OP1 dB+No
d) None of the mentioned

View Answer

Answer: a [Reason:] Linear dynamic range is defined as the ratio of 1 dB compression point to the noise level of the component. In dB scale, it is the difference of 1 dB compression point and the noise level of the component.

7. Passive intermodulation is significant only when:
a) The input signal levels are low
b) Input signal levels are high
c) Input signal is sinusoidal
d) Input signal is exponential

View Answer

Answer: b [Reason:] Because of the dependence of the third order intermodulation products with input power, passive intermodulation is usually only significant when input signal powers are relatively large.

8. A receiver has a noise figure of 7 dB, gain of 40 dB, noise temperature is 290 K. then the noise power at the receiver is:
a) 47. 4 dBm
b) -47.4 dBm
c) 23 dBm
d) -23 dBm

View Answer

Answer: b [Reason:] Noise power at the receiver is given by the expression GkB [TA + (F-1) T0]. G is the gain of the amplifier, TA is the noise temperature. F is the noise figure. Substituting the given values in the above equation, the power output at the receiver in dBm scale is -47.4 dBm.

9. For a receiver, 1 dB compression point is 25 dBm and the noise power at the receiver output is -47.4 dBm, the linear dynamic range is:
a) 70 dB
b) 72.4 dB
c) 68 dB
d) 85 dB

View Answer

Answer: b [Reason:] Linear dynamic range of the system is the difference of 1 dB compression point and the noise in the system. Substituting in the given equation, the linear dynamic range is 72.4 dB.

10. If the third order intercept point of a receiver is 35 dBm and the total noise in the receiver is -47.4 dBm signals to noise ratio is 10, then the spurious free dynamic range is:
a) 50.9 dB
b) 44.9 dB
c) 34.9 dB
d) 67 dB

View Answer

Answer: b [Reason:] The spurious free dynamic range of a receiver is given by the relation 0.6667 (OIP3_ No)-SNR. Substituting in the above equation, the spurious free dynamic range is 44.9 dB.

Set 4

1. The hybrid-π model of a BJT is useful for analysis at all frequency ranges and variation of other transistor parameters.
a) true
b) false

View Answer

Answer: a [Reason:] The element values of the hybrid-π model are fairly constant over a wide range of operating points, bias conditions, load conditions and frequency. Otherwise, the element values become frequency, bias or load dependent in which case the hybrid –π model becomes less useful.

2. If the S11 and S22 parameters of a common emitter operated BJT is high:
a) then the output and input ports are matched well
b) there is mismatch in the ports
c) the gain of the amplifier is high
d) none of the mentioned

View Answer

Answer: b [Reason:] S11 and S22 parameters of a two port network signify the amount of signal to the same port that is excited by the source, a high value of these values imply that these ports are not impedance matched properly.

3. If a common emitter configuration BJT is treated as a two port network, the gain of the amplifier is roughly given by the S parameter:
a) S11
b) S12
c) S21
d) S22

View Answer

Answer: c [Reason:] When a BJT is represented as a two port network, where the base is port 1 and collector is port 2. Gain of the amplifier is given by the parameter S21. This parameter drops quickly with an increase in the operating frequency.

4. Short circuit current gain of BJT is given by the expression:
a) gm/ωC
b) ωC/ gm
c) gm/C
d) none of the mentioned

View Answer

Answer: a [Reason:] Short circuit current gain of BJT is defined as the ratio of output collector current to the input base current assuming the base resistance to be zero. The frequency at which the short circuit current gain of the amplifier is unity is called upper frequency limit.

5. The output collector to emitter current of a BJT amplifier is independent of the input base current of the amplifier.
a) true
b) false

View Answer

Answer: b [Reason:] BJT is a current controlled device. Output collector current is controlled by the input base current. If the input base current is increased, the collector current also increases.

6. The current gain of a BJT ________ with frequency.
a) increases
b) decreases
c) remains constant
d) none of the mentioned

View Answer

Answer: a [Reason:] The short circuit current gain of a BJT amplifier is given by the expression gm/ωC. From the equation, it is seen that gain is inversely proportional to frequency. As the frequency of operation of BJT increases, current gain of the transistor reduces.

7. If a transistor has a short circuit current gain of 25 and the capacitance measured in the hybrid-π model of the transistor was 60 pF. Then the threshold frequency of operation of the transistor is:
a) 60 MHz
b) 45.6 GHz
c) 66.3 GHz
d) 34.8 GHz

View Answer

Answer: c [Reason:] The threshold frequency for a BJT is given by gm/2πC. substituting the given values; the threshold operating frequency of the transistor is 66.3 GHz.

8. Hetero junction bipolar transistors have the same working principle and operation as that of a BJT.
a) true
b) false

View Answer

Answer: b [Reason:] The operation of hetero junction BJT is same as that of BJT, but an HBT has a base emitter junction made from a compound semiconductor material such as GaAs in junction with thin layers of other materials.

9. Advantage of HJT over BJT is that it has:
a) higher gain
b) high frequency of operation
c) sophisticated construction
d) none of the mentioned

View Answer

Answer: b [Reason:] The gain of BJT reduces with the increase in the operating frequency. This problem is overcome in HJT which gives sustained gain even at frequencies of about 100 GHz. They are also suitable for application in low power circuits.

10. The S21 parameter of a HJT increases with increase in the operating frequency of the transistor.
a) true
b) false

View Answer

Answer: b [Reason:] S21 parameter of a transistor signifies the gain of the transistor. With the increase in the operating frequency of the transistor, the gain of the transistor reduces, but it is to be noted that the fall in gain of a HJT is not as rapid as fall in gain in a BJT.

Set 5

1. A __________ is a device that converts a guided electromagnetic wave on a transmission line into a plane wave propagating in free space.
a) Transmitting antenna
b) Receiving antenna
c) Radar
d) Mixer

View Answer

Answer: a [Reason:] A transmitting antenna is a device that converts a guided electromagnetic wave on a transmission line into a plane wave propagating in free space. It appears as an electrical circuit on one side, provides an interface with a propagating plane wave.

2. Antennas are bidirectional devices.
a) True
b) False

View Answer

Answer: a [Reason:] Antennas can be used both as transmitters and receivers. As transmitters they radiate energy to free space and as receivers they receive signal from free space. Hence, they are called bidirectional devices as they are used at both transmitting end and receiving end.

3. Dipole antennas are an example for:
a) Wire antennas
b) Aperture antennas
c) Array antennas
d) None of the mentioned

View Answer

Answer: a [Reason:] Dipoles, monopoles, oops, Yagi-Uda arrays are all examples for wire antennas. These antennas have low gains, and are mostly used at lower frequencies.

4. _________ antennas consist of a regular arrangement of antenna elements with a feed network
a) Aperture antennas
b) Array antennas
c) Printed antennas
d) Wire antennas

View Answer

Answer: b [Reason:] Array antennas consist of a regular arrangement of antenna elements with a feed network. Pattern characteristics such as beam pointing angle and side lobe levels can be controlled by adjusting the amplitude and phase excitation of array elements.

5. A parabolic reflector used for reception with the direct broadcast system is 18 inches in diameter and operates at 12.4 GHz. The far-field distance for this antenna is:
a) 18 m
b) 13 m
c) 16.4 m
d) 17.3 m

View Answer

Answer: d [Reason:] Far field distance for a reflector antenna is given by 2D2/λ. D is the diameter and λ is the operating signal wavelength. Substituting in the above expression, far field distance is 17.3 m.

6._________ of an antenna is a plot of the magnitude of the far field strength versus position around the antenna.
a) Radiation pattern
b) Directivity
c) Beam width
d) None of the mentioned

View Answer

Answer: a [Reason:] Radiation pattern of an antenna is a plot of the magnitude of the far field strength versus position around the antenna. This plot gives the detail regarding the region where most of the energy of antenna is radiated, side lobes and beam width of an antenna.

7. Antennas having a constant pattern in the azimuthal plane are called _____________
a) High gain antenna
b) Omni directional antenna
c) Unidirectional antenna
d) Low gain antenna

View Answer

Answer: b [Reason:] Omni directional antennas radiate EM waves in all direction. If the radiation pattern for this type of antenna is plotted, the pattern is a constant signifying that the radiated power is constant measured at any point around the antenna.

8. Beamwidth and directivity are both measures of the focusing ability of an antenna.
a) True
b) False

View Answer

Answer: a [Reason:] Beamwidth and directivity are both measures of the focusing ability of an antenna. An antenna with a narrow main beam will have high directivity, while a pattern with low beam will have low directivity.

9. If the beam width of an antenna in two orthogonal planes are 300 and 600. Then the directivity of the antenna is:
a) 24
b) 18
c) 36
d) 12

View Answer

Answer: b [Reason:] Given the beam width of the antenna in 2 planes, the directivity is given by 32400/θ*∅, where θ,∅ are the beam widths in the two orthogonal planes. Substituting in the equation, directivity of the antenna is 18.

10. If the power input to an antenna is 100 mW and if the radiated power is measured to be 90 mW, then the efficiency of the antenna is:
a) 75 %
b) 80 %
c) 90 %
d) Insufficient data

View Answer

Answer: c [Reason:] Antenna efficiency is defined as the ratio of radiated power to the input power to the antenna. Substituting the given data in the efficiency equation, the efficiency of the antenna is 90%.