300+ REAL TIME Microwave Engineering Objective Questions & Answers 2023

250+ TOP MCQs on Broadband Transistor Amplifier Design and Answers

Microwave Engineering Multiple Choice Questions on “Broadband Transistor Amplifier Design”.

1. High gain is not achievable at microwave frequencies using BJT amplifiers because:
A. device construction
B. complex architecture
C. ports are not matched at high frequencies
D. none of the mentioned
Answer: C
Clarification: At higher frequencies, if higher bandwidth is desired, a compromise on maximum achievable gain is made. But at these higher frequencies, the ports of the amplifier are not matched to 50 Ω.

2. To flatten the gain response of a transistor:
A. biasing current has to be increased
B. input signal level has to increased
C. increase the operational bandwidth
D. give negative feedback to the amplifier
Answer: D
Clarification: Negative feedback can be used to increase the gain response of the transistor, improve the input and output match, and increase the stability of the device.

3. In conventional amplifiers, a flat gain response is achieved at the cost of reduced gain. But this drawback can be overcome by using:
A. balanced amplifiers
B. distributed amplifiers
C. differential amplifiers
D. none of the mentioned
Answer: A
Clarification: In conventional amplifiers, a flat gain response is achieved at the cost of reduced gain. But this drawback can be overcome by using balanced amplifiers. This is overcome by using two 900 couplers to cancel input and output reflections from two identical amplifiers.

4. Bandwidth of balanced amplifier can be an octave or more, but is limited by the bandwidth of the coupler.
A. true
B. false
Answer: A
Clarification: In order to achieve flat gain response, balanced amplifiers use couplers to minimize reflections. But this in turn reduces the bandwidth of the amplifier to the coupler bandwidth.

5. Coupler that is mostly used in balanced amplifiers to achieve the required performance is:
A. branch line coupler
B. wilkinson coupler
C. lange coupler
D. waveguide coupler
Answer: C
Clarification: Lange couplers are broadband couplers and are compact in size. Since the bandwidth of a balanced amplifiers depends on the bandwidth of the coupler used. Lange coupler is thus preferred over couplers.

6. Distributed amplifiers offer very high _________
A. gain
B. bandwidth
C. attenuation
D. none of the mentioned
Answer: B
Clarification: Distributed amplifiers offer very high bandwidth of about 10 decade. But higher gain cannot be achieved using distributed amplifiers and matching at the ports is very important to achieve higher bandwidth.

7. In distributed amplifiers, all the FET stages in the amplifier are connected in series to one another.
A. true
B. false
Answer: B
Clarification: In distributed amplifiers, cascade of N identical FETs have their gates connected to a transmission line having a characteristic impedance of Z_g with a spacing of l_g while the drains are connected to a transmission line of characteristic impedance Z_d, with a spacing l_d.

8. ____________ uses balanced input and output, meaning that there are 2 signal lines, with opposite polarity at each port.
A. differential amplifier
B. distributed amplifier
C. balanced amplifier
D. none of the mentioned
Answer: A
Clarification: Differential amplifier uses balanced input and outputs, meaning that there are 2 signal lines, with opposite polarity at each port. It has two input ports and one output port. The difference of the 2 input signals is amplified.

9. A major advantage of differential amplifiers is:
A. high gain
B. low input impedance
C. higher output voltage swing
D. none of the mentioned
Answer: C
Clarification: Differential amplifiers can provide higher voltage swings that are approximately double that obtained with single ended amplifier.

10. Along with a differential amplifier, 180⁰ hybrid is used both at the input and output.
A. true
B. false
Answer: A
Clarification: A differential amplifier can be constructed using two single-ended amplifiers and 180⁰ hybrids at the input and output to split and then recombine the signals.

250+ TOP MCQs on Antenna Basics and Answers

Microwave Engineering Multiple Choice Questions on “Antenna Basics”.

1. The basic requirements of transmitting antennas are:
A. High efficiency
B. Low side lobes
C. Large signal to noise ratio
D. Lone of the mentioned
Answer: A
Clarification: The basic requirements of a transmitting antenna are high gain and efficiency while requirements of receiving antennas are low side lobes and large signal to noise to ratio.

2. _________ is a device that converts electrons to photons or vice-versa.
A. Antenna
B. Electron gun
C. Photon amplifier
D. Microwave tube
Answer: A
Clarification: Antenna is a device that converts electrons into photons or vice versa. A transmitting antenna converts electrons into photons while a receiving antenna converts photons into electrons.

3. The basic equation of radiation that is applied to any antenna irrespective of the type of the antenna is:
A. iL= Qv
B. iQ = Lv
C. i/L=Q/v
D. None of the mentioned
Answer: A
Clarification: Basic equation of radiation is given by iL=Qv. i is the time change in current, l is the length of the current element, q is the charge v is the acceleration of the charge.

4. When the separation between two lines that carry the TEM wave approaches λ the wave tends to be radiated.
A. True
B. False
Answer: A
Clarification: When the separation between two lines that chary the TEM wave approaches λ the wave tends to be radiated so that the opened – out line act as an antenna which lunches a free space wave.

5. The number of patterns radiation pattern required to specify the characteristic are :
A. Three
B. Four
C. Two
D. Five
Answer: A
Clarification: The three patterns required are, θ component of the electric field as the function of the angles as θ and φ, the φ component of the electric field as the function of the angles θ and φ, the phase of these fields as a functions of the angle φ and θ .

6. The beam width of the antenna pattern measured at half power points is called:
A. Half power beam width
B. Full null beam width
C. Beam width
D. None of the mentioned
Answer: A
Clarification: The beam width of an antenna measure at half of the maximum power received by an antenna or the 3 dB beam width of the antenna is termed as half null beam width.

7. An antenna has a field pattern of E (θ) = cos2 θ, θ varies between 0 and 900. Half power beam width of the antenna is:
A. 33⁰
B. 66⁰
C. 1200⁰
D. None of the mentioned
Answer: B
Clarification: Half power beam width of the antenna is obtained by equating the field pattern of the antenna to 0.707 (half power point) and finding θ. 2θ gives the value of beam width. Solving the given problem in the same flow, half power beam width of the antenna is 66⁰.

8. An antenna has a field pattern E (θ) =cos θ. cos 2θ. The first null beam width of the antenna is:
A. 45⁰
B. 90⁰
C. 180⁰
D. 120⁰
Answer: B
Clarification: Half power beam width of the antenna is obtained by equating the field pattern of the antenna to 0.707 (half power point) and finding θ. 2θ gives the value of beam width. Twice the half power beam width gives the first null beam width. With the same steps applied, the half power beam width of the antenna is 450. First null beam width is 90⁰.

9. The solid area through which all the power radiated by the antenna is:
A. Beam area
B. Effective area
C. Aperture area
D. Beam efficiency
Answer: A
Clarification: The beam area is the solid angle through which all of the power radiated by the antenna would stream if P (θ, φ) maintained its maximum value over beam area and zero elsewhere. This value is approximately equal to the angles subtended by the half power points of the main lobe in the two principal planes.

10. Power radiated from an antenna per unit solid angle is called radiation intensity.
A. True
B. False
Answer: A
Clarification: Power radiated from an antenna per unit solid angle is called radiation intensity. Unit of radiation intensity is watts per steridian or per square degree.