PSU MCQs on Microwave Engineering

1. A reflex Klystron fuctions as
a) Microwave oscillator
b) Microwave amplifier
c) Both as Microwave amplifier and oscillator
d) A high gain cavity

Ans: Option a)

2. The modes in a reflex Klystron
a) give the same frequency but different transit times
b) result from excessive transit time across the resonator gap
c) are caused by spurious frequency modulation
d) are just for theoretical considerations

Ans: Option a)


3. Klystron operates on the principle of
a) Amplitude Modulation
b) Frequency Modulation
c) Pulse Modulation
d) Velocity Modulation

And: Option d)

4. In Microwave we take the elements as
a) Lumped circuit elements
b) Distributed circuit elements
c) Both a) and b)
d) None of the above

Ans: Option b)

5. Short term fading in microwave communication links can be overcome by
a) Increasing the transmitted power
b) Changing the antenna
c) Changing the modulation scheme
d) Diversity reception and transmission

Ans: Option d)

6. For handling large microwave power, the best medium is
a) Coaxial line
b) Rectangular waveguide
c) Stripline
d) Circular waveguide

Ans: Option b)

7. A Microwave tube amplifier uses an axial magnetic field and radial electric field. This is the
a) Reflex Klystron
b) Coaxial Magnetron
c) Travelling wave magnetron
d) CFA-Crossed Field Amplifier

Ans: Option d)

8. A disadvantage of microstrips with respect to stripline circuit is that the former:
a) Do not let themselves to be printed-circuits
b) Are more likely to radiate
c) Are bulkier
d) Are more expensive and complex to manufacture

Ans: Option d)

9. Most of the power measuring microwave devices measure
a) Average power
b) Peak power
c) Instantaneous power
d) None of these

Ans: Option a)

10. HEMT used in microwave circuit is a
a) Source
b) High power amplifier
c) Detector
d) Low noise Amplifier

Ans: Option d)

11. Ionospheric preparation is not possible for microwaves because
a) Microwaves will be fully absorbed by the ionospheric layers
b) There will be an abrupt scattering in all directions
c) Microwave will penetrate through the ionospheric layers
d) There will be dispersion of microwave energy

Ans: Option c)

12. A waveguide section in a microwave circuit will act as a
a) Low-pass filter
b) Band-pass filter
c) High-pass filter
d) Band-reject filter

Ans: Option c)

13. The biggest advantage of the TRAPATT diode over the IMPATT diode is its
a) Low noise
b) Higher efficiency
c) Ability to operate at higher frequencies
d) Lesser sensitivity to harmonics

Ans: Option b)

14. A varactor diode may not be useful at microwave frequencies
a) For electronic tuning
b) for frequency multiplication
c) as an oscillator
d) As a parametric amplifier

Ans: Option c)

15. The negative resistance in a tunnel diode
a) is maximum at the peak point of the characteristic
b) is available between the peak and valley points
c) is maximum at valley point
d) may be improved by the use of reverse bias

Ans: Option b)

16. Which one of the following is a transferred electron device?
a) BARITT diode
b) IMPATT diode
c) Gunn diode
d) Step recovery diode

Ans: Option c)

17. A PIN diode is suitable for use as a
a) Microwave switch
b) Microwave mixed diode
c) Microwave detector
d) None of these

Ans: Option a)

18. The semiconductor diode which can be used in switching circuits at microwave range is
a) PIN diode
b) Tunnel diode
c) Varactor diode
d) Gunn diode

Ans:  Option a)

19. Microwave antenna aperture efficiency depends on
a) Feed Pattern
b) Antenna Aperture
c) Surface losses
d) Low side lobe level

Ans: Option b)

20. The noise produced in a microwave tube due to random nature of emission and electron flow is called
a) Partition noise
b) Shot noise
c) Johnson noise
d) Shannon noise

Ans: Option b)

21. A duplexer is used
a) To couple two different antennas to a transmitter without mutual interference
b) To allow one antenna to be used for reception or transmission without mutual interference
c) To prevent interference between two antennas when they are connected to a receiver
d) To increase the speed of the pulses in pulsed radar

Ans: Option b)

22. One of the reasons why vacuum tubes eventually fail at microwave frequencies is that their
a) Noise figure increases
b) Transit time becomes too short
c) Shunt capacitive reactances become too large
d) Series inductive reactances become too small

Ans: Option a)

23.A magic-Tee is nothing but
a) A modification of E-plane tee
b) A modification of H-plane tee
c) A combination of E-Plane and H-Plane
d) Two E-plane tees connected in parallel

Ans: Option c)

24. Which of the following can be used for amplification of microwave energy?
a) Travelling wave tube
b) Magnetron
c) Reflex Klystron
d) Gunn diode

Ans: Option a)

25. In microwave power measurements using bolometer, the principle of working is the variation of
a) Inductance with absorption of power
b) Resistance with absorption of power
c) Capacitance with absorption of power
d) Cavity dimensions with heat generated by the power

Ans: Option b)

26. In π mode operation of magnetron, the spokes due to phase focusing effect rotate at an angular velocity corresponding to
a) One pole/cycle
b) Two poles/cycle
c) Four poles/cycle
d) Six poles/cycle

Ans: Option b)

27. For Gunn diodes, gallium arsenide is preferred to silicon because the former
a) Has a suitable empty energy band, which silicon does not have
b) Has a higher ion mobility
c) Has a lower noise at the highest frequencies
d) Is capable of handling higher power densities

Ans: Option a)

28. For best low-level noise performance in the X-band an amplifier should use
a) A bipolar transistor
b) A Gunn diode
c) A step recovery diode
d) An IMPATT diode

Ans: Option c)

29. Travelling wave parametric amplifiers are used to
a) provide a greater gain
b) reduce the number of varactor diodes required
c) avoid the need for cooling
d) provide a greater bandwidth

Ans: Option d)

30. The major advantage of TWT over Klystron
a) higher gain
b) higher frequency
c) higher output
d) higher bandwidth

Ans: Option d)

31. Microwave frequency range extends from
a) 3 MHz to 30 MHz
b) 30 MHz to 300 MHz
c) 300 MHz to 3000 MHz
d) 500 MHz to 30000 MHz

Ans: Option d)

32. Due to curvature of earth, microwave repeaters are placed at a distance of about
a) 10 Km
b) 50 Km
c) 150 Km
d) 250 Km

Ans: Option b)

33. At microwave frequencies the size of the antenna becomes
a) Very large
b) Large
c) Small
d) Very Small

Ans: Option d)

34. Which of the following noise becomes important at microwave frequencies
a) Shot noise
b) Flicker noise
c) Thermal noise
d) Transit time noise

Ans: Option d)

35. The phenomenon of microwave signals following the curvature of earth is known as
a) Faraday effect
b) Ducting
c) Wave tilt
d) Troposcatter

Ans: Option b)

36. The front end of an amplifier chain in manufacture of a communication system is kept immersed in liquid nitrogen to
a) Dissipate heat generated by amplifier
b) Expand the frequency response
c) Improve its noise figure
d) reduce the distortion by the amplifier

Ans: Option c)

37. In microwave communication links, the rain drop attenuation experienced is mainly due to
a) Absorption of microwave energy by water vapour
b) resonance absorption of atomic vibration in water molecules
c) scattering of microwaves by collection of water drops
d) refraction of microwaves through liquid-drop lenses formed by rain

Ans: Option a)

PSU MCQs on Microprocessors

1. A memory system has a total of 8 memory chips, each with 12 address lines and 4 data lines. The total size of the memory system is
a) 16 Kbytes
b) 48 Kbytes
c) 32 Kbytes
d) 64 Kbytes

Ans: Option a)
Each chip has 2¹² = 4096 x 4 bits
Capacity of 8 chips = 4096 x 4 x 8 = 16 Kbytes

2. What will be the size of memory address space for a 16 bit data and 20 bit address bus?
a) 1 MB
b) 64 KB
c) 2 MB
d) None of these

Ans: Option a)

Size of memory address space depends on the address bus size.
2²⁰ = 1048576 = 1 MB

3. The memory address of last location of an 8 KB memory chip is FFFF H. Find the starting address.
a) F000  H
b) E001 H
c) E000 H
d) F001 H
Ans: Option c)

4. A microprocessor is capable of addressing 64 K bytes of memory. Its address bus width is
a) 8
b) 16
c) 12
d) 20

Ans: Option b)
64 K = 2ⁿ

64 x 1024 = 2ⁿ

 2⁶ x 2¹⁰  = 2¹⁶

5. How many address lines are necessary to address 2 MB of memory?

a) 21

b) 20

c) 22

d) 10

Ans: Option a)

6. How many memory cells are there in a 128 x 4 memory chip?
a) 128
b) 512
c) 4
d) 1024

Ans: Option b)

7. An 8-bit microprocessor signifies that it has
a) An 8-bit address bus
b) An 8 bit controller
c) 8-bit interrupt lines
d) An 8 bit data bus

Ans: Option d)

8.  In a microprocessor based system, the stack is always in
a) Microprocessor
b) ROM
c) RAM
d) EPROM

Ans: Option c)

9. Which of the following statements is false?
a) A microprocessor has bi-directional address bus
b) A microprocessor has a unidirectional address bus
c) A microprocessor has bidirectional data bus
d) A microprocessor has an ALU

Ans: Option b)

10. A stack is
a) An 8 bit register in the microprocessor
b) An 16 bit register in the microprocessor
c) A set of memory locations in R/W memory reserved for storing information
d) An 16 bit memory address stored in the PC

Ans: Option c)

11. When a sub routine is called, the address of instruction following the CALL instruction is stored in/on the
a) Stack Pointer
b) Accumulator
c) Program Counter
d) Stack

Ans: Option c)

12. The stack operates as
a) FIFO
b) LILO
c) LIFO
d) None of these

Ans: Option c)

13. The data bus of any microprocessor is always
a) Unidirectional
b) bi-directional
c) Either unidirectional or bi-directional
d) None of these

Ans: Option b)

14. Which one of the following is not a vectored interrupt?
a) TRAP
b) RST 7.5
c) INTR
d) RST3

Ans: Option a)

15. Identify the non-maskable interrupt from the following
a) RST 7.5
b) RST 5.5
c) RST 6.5
d) RST 4.5

Ans: Option d)
Except TRAP( RST 4.5), all other interrupts are maskable

16. The number of hardware interrupts present in 8085 microprocessor are
a) 5
b) 10
c) 8
d) 16

Ans: Option a)

TRAP
RST 7.5
RST 6.5
RST 5.5
INTR

17. An instruction which contains the data in it uses
a) Register Addressing
b) Immediate Addressing
c) Register Indirect Addressing
d) Relative addressing

Ans: Option b)

18. The clock frequency of 8085 microprocessor is
a) 2 MHz
b) 3 MHz
c) 4 MHz
d) 6 MHz

Ans: Option b)

19. The crystal frequency of 8085 microprocessor is
a) 2 MHz
b) 3 MHz
c) 4 MHz
d) 6 MHz

Ans: Option d)

20. The addressing mode used in the instruction PUSH B is
a) direct
b) register
c) register indirect
d) Immediate

Ans: Option c)

21. When any arithmetic instruction such as ADD or SUB is executed the condition flags
a) are always set
b) are always reset
c) are not affected
d) are affected indicating specific conditions

Ans: Option d)

22. When any data transfer instruction, for transfer of data between memory and microprocessor, is executed the condition flags are
a) not affected
b) always set
c) always reset
d) affected indicating specific conditions

Ans: Option a)

23. Which of the following flag condition are not available in 8085 microprocessor?
a) Zero Flag
b) Parity Flag
c) Overflow Flag
d) Auxillary Flag

Ans: Option c)

24. Which of the following instruction will never affect the zero flag?
a) DCR reg.
b) ORA reg.
c) DCX reg.
d) XRA reg.

Ans: Option c)

25. In a flag register of 8085, where does the sign flag and parity flag set?
a) D₇ and D₆

b) D₆ and D₄

c) D₇ and D₂

d) D₇ and D₄

Ans: Option c)

26. Specify the number of times the given loop will count

LOOP:  MVI B, 64 H
             DCR B
             JNZ LOOP
a) 101
b) 100
c) 65
d) infinite

Ans: Option d)

27. If the result has an odd number of 1s, what will happen to the parity flag
a) Set
b) Reset
c) Data insufficient
d) None of these

Ans: Option b)

28. The instruction RST 7 is a
a) Restart instruction that begins the execution of a program
b) One-byte call to the memory address 0038 H
c) One-byte call to the memory address 0007 H
d) Hardware interrupt

Ans: Option b)

29. Which of the following instruction can be set to clear CY flag?
a) XRA A
b) CLR
c) AND A
d) ADD A

Ans: Option a)

30. The number of status flags present in 8085 microprocessor are
a) 8
b) 5
c) 16
d) 10

Ans: Option b)

31. Let the contents of register C be 00000000 before DCR C is executed. The contents of the register after the execution of this instruction will be
a) 00000000
b) 00000001
c) 11111111
d) None

Ans: Option c)

32. PUSH B instruction in 8085 microprocessor causes
a) the contents of register B only to be copied in the stack
b) the contents of register B and C to be copied in the stack
c) the contents of register B and C to be transferred in the stack and the registers get cleared
d) Registers B and C to be cleared

Ans: Option b)

33. How many times the following loop will be executed?

                LXI          B, 0007 H

LOOP:   DCX        B

                MOV     A, B

                ORA       C

                JNZ         LOOP

a) 7 times 

b) Cant say

c) 8 times

d) infinitely

Ans: Option a)

34. The multiplexing of address bus and data buses is used in microprocessors

a) To reduce the hardware complexity

b) To increase the number of pins

c) To reduce the number of pins on IC

d) To improve the operation

Ans: Option c)

35. In a 8085 microprocessor based system, the contents of SP are 1000 H. PUSH B instruction will transfer the contents of registers B and C respectively for memory locations

a) OFFF H and OFFE H

b) 1000 H and 0FFF H

c) OFFE H and OFFFH

d) 1000 H and 1001 H

Ans: Option a)

36. Intel 8085 is an
a) 8 bit NMOS processor
b) 8 bit CMOS processor
c) 8 bit PMOS processor
d) 8 bit HMOS processor

Ans: Option a)

37. Which of the following is a 3 byte instruction?
a) LDA 2050 H
b) MVI A, 32 H
c) MOV C, A
d) ADD B

Ans: Option a)

38. Which of the following devices is commonly used to interface O/P devices?
a) Latch
b) Tristate buffer
c) Both a) and b)
d) None of these

Ans: Option a)

39. Which of the following devices is commonly used to interface I/P devices?
a) Latch
b) Tristate buffer
c) Both a) and b)
d) None of these

Ans: Option b)

40. Specify the flag status (CY, S, Z) after the execution of instruction DRA.

                MVI       A, A9  H

                MVI       B, 57 H

                ADD       B

                ORA       A

a) 1,1,1

b) 0,1,0

c) 1,0,1

d) 1,1,0

Ans: Option a)

41. Wait states are used
a) to give slow devices additional time to put out valid data
b) to insert deliberate delay
c) during I/O operation
d) none of the above

Ans: Option a)

42. READY signal in 8085 is useful when the CPU communicates with
a) a slow peripheral device
b) a fast peripheral device
c) a DMA controller chi
d) A PPI chip

Ans: Option a)

43. Direct-Memory-Access Channel (DMA) facilitates data to move into and out of system
a) on first-come-first-serve basis
b) with equal time delay
c) with sub-routine
d) without program intervention

Ans: Option d)

44. Return from subroutine is affected by
a) a jump instruction
b) an RST instruction
c) a RET instruction
d) a hardware interrupt signal

Ans: Option c)

45. In a generic microprocessor instruction cycle time is
a) shorter than machine cycle time
b) larger than machine cycle time
c) exactly double the machine cycle time
d) exactly the same as the machine cycle time

Ans: Option d)

46. The highest priority interrupt in 8085 microprocessor system is
a) RST 7.5
b) RST 6.5
c) INTR
d) TRAP

Ans: Option d)

47. Which of the following statements is not applicable to serial transmission of data?
a) one bit at a time
b) faster method of transmission
c) LSB transferred first
d) only one wire used

Ans: Option b)

48. The three buses associated with three-bus system are I/O bus, memory bus and
a) address bus
b) unibus
c) direct memory access bus
d) data bus

Ans: Option c)

49. The bus which is used to transfer data from main memory to peripheral device is
a) data bus
b) input bus
c) DMA bus
d) output bus

Ans: Option c)

50. SHIFT LEFT instruction causes all bits shifted from one position to the left with rightmost bit set to zero. The effect is to
a) multiply by 2
b) divide by 2
c) SET the most significant bit
d) none of the above

Ans: Option a)

51. Which of the following signal is used when a peripheral device request the microprocessor to have a DMA operation?

a) IO/M
b) READY
c) HOLD and HLDA
d) RD and WR

Ans: Option c)

52. The output data lines of microprocessors and memories are usually tri-stated, because
a) More than one device can transmit information over the data bus by enabling only one device
b) More than one device can transmit information over the data bus at the same time
c) The data lines can be multiplexed for both input and output
d) It increases the speed of data transfers over the data bus

Ans: Option a)

53. Which of the following instruction copies a byte of data into the accumulator from the memory address given in the instruction?
a) LDA address
b) LDAX B
c) LHLD address
d) STA address

Ans: Option a)

ISRO EC 2006 SET B

Sol: Option c)

Taking the characteristic equation

Another Method:

Sol: option C)

Sol: Option a)

Sol: Option b)
At resonance

Sol: Option d)
In a series RLC circuit:
Below resonance frequency, circuit has capacitive impedance
At resonance, circuit impedance is totally resistive
Above resonance, circuit has inductive impedance

Sol: Option d)

Sol: Option a)
In Sigma delta ADC, high bit accuracy is achieved by Over Sampling and noise shaping.

Sol: Option a)

Sol: Option b) or d)

Sol: option a)

Sol: Option a)

Sol: Option a)

Sol: Option a)




Sol: Option c)

Sol: Option a)

Sol: Option c)

Sol: Option c)

Sol: Option d) with small correction in last but first term. It should be (Xn-2)(Xn-1) '+' sign should be  removed in between .

Sol: Option a)

Sol: Option b)

Sol: Option a)

Sol: Option b)

Sol: Option d)

Sol: Option c)

Sol: Option b)

Sol: Option b)

Sol: Option d)

Sol: Option c)

Sol: Option c)

Sol: Option d)

Sol: Option a)

Sol: Option b)

Sol: Option c)
No possible grouping. 

Sol: None of the options. It is actually gray to binary converter.

Sol: Option a)

Sol: Option a)

Sol: Option d)

Sol: Option b)

Sol: Option d)

 Sol: Option d)

Sol: Option d)

Sol: Option a)

Sol: Option d)

Sol: Option c)






Sol: Option b)

Sol: Option b)

 Sol: Option d)

Sol: Option b)

Sol: Option a)

Sol: Option a)

Sol: Option c)

Sol: Option c)

Sol: Option c)

Sol: Option c)

Sol: Option d)

Sol: Option c)

Sol: Option b)

Sol: option b)

Sol: Option d)

Sol: Option a)

Sol: Option b)

Sol: Option c)

Sol: Option d)

Sol: Option c)
Hysteresis loss and Eddy current loss depends on frequency.

Sol: Option c)

Sol: Option a)

Sol: Option d)
A Capacitor blocks dc voltage. Therefore its zero steady state current.

Sol: Option b)

Sol: Option d)

Sol: Option a)

Sol: option d)







Sol: Option d)