Digital Communications Multiple Choice Questions on “Link budget analysis”.
1. Link budget consists of calculation of
A. Useful signal power
B. Interfering noise power
C. Useful signal & Interfering noise power
D. None of the mentioned
Answer: C
Clarification: The link analysis and its output, the link budget consists of calculations and tabulations of useful signal power and interfering noise power at the receiver.
2. Link budget can help in predicting
A. Equipment weight and size
B. Technical risk
C. Prime power requirements
D. All of the mentioned
Answer: D
Clarification: Link budget can help to predict equipment weight, size, prime power requirements, technical risk and cost. Link budget is one of the system manager’s useful document.
3. Which is the primary cost for degradation of error performance?
A. Loss in signal to noise ratio
B. Signal distortion
C. Signal distortion & Loss in signal to noise ratio
D. None of the mentioned
Answer: C
Clarification: There are two primary causes for the degradation of error performance. They are loss in signal to noise ratio and the second is signal distortion caused by intersymbol interference.
4. Which factor adds phase noise to the signal?
A. Jitter
B. Phase fluctuations
C. Jitter & Phase fluctuations
D. None of the mentioned
Answer: C
Clarification: When a local oscillator is used in signal mixing, phase fluctuations and jitter adds phase noise to the signal.
5. Antennas are used
A. As transducer
B. To focus
C. As transducer & To focus
D. None of the mentioned
Answer: C
Clarification: Antennas are used as transducer that converts electronic signals to electromagnetic fields and vice versa. They are also used to focus the electromagnetic energy in the desired direction.
6. Mechanism contributing to a reduction in efficiency is called as
A. Amplitude tapering
B. Blockage
C. Edge diffraction
D. All of the mentioned
Answer: D
Clarification: Mechanism contributing to a reduction in efficiency is called as amplitude tapering, spillover, edge diffraction, blockage, scattering, re-radiation and dissipative loss.
7. Space loss occurs due to a decrease in
A. Electric field strength
B. Efficiency
C. Phase
D. Signal power
Answer: A
Clarification: Due to the decrease in electric field strength there will be a decrease in signal strength as a function of distance. This is called as space loss.
8. Antenna’s efficiency is given by the ratio of
A. Effective aperture to physical aperture
B. Physical aperture to effective aperture
C. Signal power to noise power
D. Losses
Answer: A
Clarification: The larger the antenna aperture the larger is the resulting signal power density in the desired direction. The ratio of effective aperture to physical aperture is the antenna’s efficiency.
9. Effective radiated power of an isotropic radiator can be given as a product of
A. Radiated power and received power
B. Effective area and physical area
C. Transmitted power and transmitting gain
D. Receiving power and receiving gain
Answer: C
Clarification: An effective radiated power with respect to an isotropic radiator EIRP can be defined as the product of transmitted power and the gain of the transmitting antenna.
10. According to reciprocity theorem, _____ and _____ are identical.
A. Transmitting power and receiving power
B. Transmitting gain and receiving gain
C. Effective area and physical area
D. None of the mentioned
Answer: B
Clarification: The reciprocity theorem states that for a given antenna and carrier wavelength the transmitting and receiving gain are identical.