Question 1

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

Accepted Answer

Antenna arrays are used to increase the electrical size of an antenna, which reduces the size of the side lobes compared to a single antenna.

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

Accepted Answer

The total resultant field obtained by an antenna array is given by the vector superposition of individual fields from each element in the array. This means that the fields from all the individual antennas are added together vectorially to get the overall field pattern.

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

Accepted Answer

When the progressive shift in an antenna array is equal to zero, it means that all the elements in the array are fed in phase. This configuration directs the main beam of radiation to be perpendicular to the axis of the array, which is characteristic of a broadside array.

Question 4

What is the progressive phase shift of the end-fire array?
A)0
B)90
C)180
D)60

Accepted Answer

The answer of What is the progressive phase shift of...

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

Accepted Answer

The field pattern of an antenna array is not the sum of individual elements; it is the vector superposition of the fields from individual elements, which involves both magnitude and phase.

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

Accepted Answer

Power amplifiers are used in the final stages of radar and radio transmitters to increase the power level of the signal before it is radiated by the antenna.

Question 7

Important factors to be considered for power amplifier design are:
A)efficiency
B)gain
C)thermal effect
D)all of the mentioned

Accepted Answer

All of the mentioned factors, including efficiency, gain, and thermal effects, are important considerations in the design of power amplifiers.

Question 8

Gain of power amplifiers __________  with increase in operating frequency.
A)increases
B)decreases
C)increases exponentially
D)decreases exponentially

Accepted Answer

The gain of power amplifiers decreases with an increase in operating frequency due to factors like parasitic capacitance and inductance, which become more significant at higher frequencies, leading to loss of gain.

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

Accepted Answer

Class A amplifiers are designed to conduct over the entire range of the input signal cycle, making them linear circuits. This means they are biased in a way that allows the transistor to be active throughout the whole cycle of the input signal, avoiding any part of the signal being cut off.

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

Accepted Answer

A class B amplifier uses 2 transistors to conduct the input signal over the entire cycle, with each transistor conducting for one half of the cycle.

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

Accepted Answer

Class A amplifiers have the lowest efficiency, Class B amplifiers have higher efficiency than Class A, and Class C amplifiers have the highest efficiency among the three.

Question 12

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

Accepted Answer

The behavior of a transistor in power amplifiers is generally predictable and follows known principles of semiconductor physics, although it can vary with temperature, frequency, and signal level. However, design and engineering practices allow for effective management of these variations to achieve desired performance.

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%

Accepted Answer

The efficiency of an amplifier is not directly related to the input and output voltage levels but rather to the power levels and how much of the input power is converted into output power versus how much is lost as heat or in other inefficiencies. The choices provided (25%, 50%, 75%, 35%) seem to refer to efficiency percentages, but without specific information on power (not voltage) and losses, or how these percentages were derived, it's impossible to accurately determine the efficiency based on the given voltage values alone. The question appears to be malformed or missing crucial information needed to calculate efficiency.

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

Accepted Answer

The gain in dB is given by $G_{dB} = 10 \log_{10} \left(\frac{P_{out}}{P_{in}}\right)$, where $P_{out}$ is the output power and $P_{in}$ is the input power. Rearranging for $P_{in}$, we get $P_{in} = P_{out} / 10^{(G_{dB}/10)}$. Substituting $P_{out} = 10W$ and $G_{dB} = 16.4$, we find $P_{in} = 10 / 10^{(16.4/10)} = 10 / 10^{1.64} = 10 / 43.65 \approx 0.229W$ or 229 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

Accepted Answer

The answer of GaAs is used in the fabrication of...

Question 16

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

Accepted Answer

In a GaAs n-type specimen, the current generated is not constant and varies with the electric field applied. At low electric fields, the current increases linearly with the field due to Ohm's law. At higher fields, velocity saturation occurs, leading to a sublinear increase in current.

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

Accepted Answer

When the electric field applied to a GaAs specimen is less than the threshold electric field, the current in the material increases linearly with the electric field. This behavior is typical of semiconductors under low electric fields, where Ohm's law is applicable, and the current-voltage relationship is linear.

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

Accepted Answer

Gunn diode is a bulk device because its operation depends on the properties of the semiconductor material itself (Gallium Arsenide, GaAs) rather than on a p-n junction or layered structure.

Question 19

The electrodes of a Gunn diode are made of:
A)molybdenum
B)gaas
C)gold
D)copper

Accepted Answer

Molybdenum is commonly used for the electrodes of a Gunn diode due to its good conductivity and compatibility with the semiconductor material.

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

Accepted Answer

When a voltage or current is applied to the terminals of bulk solid state compound GaAs, a differential negative resistance is developed, which is a characteristic feature of certain semiconductor devices like the Tunnel Diode, where the current decreases with an increase in voltage across certain regions of its operation.

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

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

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

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

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

Which of the following statement about antenna array is false?

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

Important factors to be considered for power amplifier design are:

Gain of power amplifiers __________ with increase in operating frequency.

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

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

Power amplifiers in the increasing order of efficiency is:

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

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

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:

GaAs is used in the fabrication of GUNN diodes because:

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

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

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

The electrodes of a Gunn diode are made of:

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.