Deck 4: Antenna Arrays, Power Amplifiers, and Gunn Diodes

Question 1

The electrical size of antenna is increased by antenna array to avoid size lobes compared to single antenna.

Answer 1

True

Question 2

Total resultant field obtained by the antenna array is given by which of following?

A)vector superposition of individual field from the element
B)maximum field from individual sources in the array
C)minimum field from individual sources in the array
D)field from the individual source

Answer 2

vector superposition of individual field from the element

Question 3

If the progressive shift in antenna array is equal to zero then it is called __________

A)broad side
B)end-fire
C)yagi-uda
D)fishbone antenna

Answer 3

broad side

Question 4

What is the progressive phase shift of the end-fire array?

A)0
B)90
C)180
D)60

Question 5

Which of the following statement about antenna array is false?

A)field pattern is the product of individual elements in array
B)field pattern is the sum of individual elements in array
C)resultant field is the vector superposition of the fields from individual elements in array
D)high directivity can be achieved for long distance communications

Question 6

__________are used in the final stages of radar and radio transmitters to increase the radiated power level.

A)power amplifiers
B)oscillators
C)transistors
D)attenuators

Question 7

Important factors to be considered for power amplifier design are:

A)efficiency
B)gain
C)thermal effect
D)all of the mentioned

Question 8

Gain of power amplifiers __________  with increase in operating frequency.

A)increases
B)decreases
C)increases exponentially
D)decreases exponentially

Question 9

__________ amplifiers are linear circuits, where the transistor is biased to conduct over the entire range of the input signal cycle.

A)class a amplifiers
B)class b amplifiers
C)class c amplifiers
D)none of the mentioned

Question 10

A class B amplifier consists of __________   transistors in order to conduct the input signal over the entire cycle.

A)1
B)2
C)4
D)6

Question 11

Power amplifiers in the increasing order of efficiency is:

A)class a, b, c
B)class c, a, b
C)class b, a, c
D)efficiency of all the 3 amplifiers is the same

Question 12

Behavior of a transistor in power amplifiers is unpredictable at all input signal levels.

Question 13

If the output power of an amplifier is 10 V, and the input power supplied to the amplifier is 0.229 V given that the DC voltage used is

A)25%
B)50%
C)75%
D)35%

Question 14

If a power amplifier has an output power of 10 W, and an amplifier gain of 16.4 dB, then the input drive power is:

A)400 mw
B)225 mw
C)229 mw
D)240 mw

Question 15

GaAs is used in the fabrication of GUNN diodes because:

A)gaas is cost effective
B)it less temperature sensitive
C)it has low conduction band electrons
D)less forbidden energy gap

Question 16

In a GaAs n-type specimen, the current generated is constant irrespective of the electric filed applied to the specimen.

Question 17

When the electric field applied to GaAs specimen is less than the threshold electric field, the current in the material:

A)increases linearly
B)decreases linearly
C)increases exponentially
D)decreases exponentially

Question 18

GaAs is used in fabricating Gunn diode. Gunn diode is:

A)bulk device
B)sliced device
C)made of different type of semiconductor layers
D)none of the mentioned

Question 19

The electrodes of a Gunn diode are made of:

A)molybdenum
B)gaas
C)gold
D)copper

Question 20

When either a voltage or current is applied to the terminals of bulk solid state compound GaAs, a differential __________is developed in that bulk device.

A)negative resistance
B)positive resistance
C)negative voltage
D)none of the mentioned

Question 21

The number of modes of operation for n type GaAs is:

A)two
B)three
C)four
D)five

Question 22

The free electron concentration in N-type GaAs is controlled by:

A)effective doping
B)bias voltage
C)drive current
D)none of the mentioned

Question 23

The modes of operation of a Gunn diode are illustrated in a plot of voltage applied to the Gunn diode v/s frequency of operation of Gunn diode.

Question 24

The mode of operation in which the Gunn diode is not stable is:

A)gunn oscillation mode
B)limited space charge accumulation mode
C)stable amplification mode
D)bias circuit oscillation mode