Microwave Engineering Multiple Choice Questions on “Wireless Communication”.
1. Most of the wireless systems today operate at a frequency of about:
A. 800 MHz
B. 100 MHz
C. 80 MHz
D. None of the mentioned
Answer: A
Clarification: With all advancement in wireless communication today, the need of the hour is higher data rates of transmission and reception. These higher data rates can be achieved only at microwave frequency range and in giga hertz frequency range.
2. Point to point communication systems use low gain antennas for communication.
A. True
B. False
Answer: B
Clarification: In point to point communication a single transmitter communicates with a single receiver. Such systems use high gain antennas to maximize received power and minimize interference with other radios.
3. In this method of wireless communication, communication happens only in one direction:
A. Simplex
B. Duplex
C. Half duplex
D. None of the mentioned
Answer: A
Clarification: In simplex systems, communication happens only in one direction that is from the transmitter to the receiver. Examples for this type of communication include radio, television and paging systems.
4. The power density radiated by an isotropic antenna is given by the relation:
A. Pt/4πR2
B. Pt/4R2
C. Pt/R2
D. None of the mentioned
Answer: A
Clarification: An isotropic antenna radiates energy equally in all the directions. Hence, the power density radiated at a distance R is given by the relation Pt/4πR2.
5. The power received by a receiving antenna given that Pt is the transmitted power is:
A. GrGtλ2pt/ (4πR)2
B. Gtλ2pt/ (4πR)2
C. Grλ2pt/ (4πR)2
D. None of the mentioned
Answer: A
Clarification: The power received by a receiving antenna given that Pt is the transmitted power is GrGtλ2pt/ (4πR)2. Here Gr is the gain of the receiving antenna; Gt is the gain of the transmitting antenna. R is the distance between the transmitting and receiving antenna.
6. If the distance between a transmitting station and receiving station is 1 Km and if the antennas are operating at a wavelength of 5 cm, then the path loss is:
A. 108 dB
B. 12 dB
C. 45 dB
D. 48 dB
Answer: A
Clarification: Path loss is given by the expression 20 log (4πR/λ) in db. Substituting the given values in the above expression, the path loss is 108 dB.
7. The amount of power by which the received power must be greater than the threshold level required to maintain a minimum quality of service is called _______
A. Line loss
B. Link budget
C. Link margin
D. None of the mentioned
Answer: C
Clarification: Link margin is the amount of power by which the received power must be greater than the threshold level required to maintain a minimum quality of service. Link margin signifies the minimum amount of power required to sustain communication maintaining a minimum quality of service.
8. Link margin that is used to account for fading effects is called fade margin.
A. True
B. False
Answer: A
Clarification: Link margin that is used to account for fading effects is called fade margin. Satellite links operating at frequencies of above 10 GHz require a fading margin of about 20dB or more to account for attenuation during heavy rain.
9. One of the most important requirements of a radio receiver is high gain.
A. True
B. False
Answer: A
Clarification: Radio receivers must have very high gain of about 100 dB in order to detect the very low power level of the received signal to a level near its original baseband value.
10. A radio receiver operating at microwave frequencies must have very high selectivity.
A. True
B. False
Answer: A
Clarification: Today, most of the applications use wireless communication at microwave frequency. Hence space is a sea of EM waves. In order to receive only the desired signal in the desired range of frequencies, the radio receiver must have high sensitivity.
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