1. The mechanism behind electromagnetic wave propagation cannot be attributed to ___________
a) Reflection
b) Diffraction
c) Scattering
d) Sectoring
Explanation: The mechanisms behind electromagnetic wave propagation are diverse. They can be greatly attributed to reflection, diffraction and scattering. Due to multiple reflections from various objects, the electromagnetic waves travel along different paths of varying lengths.
2.The propagation model that estimates radio coverage of a transmitter is called ___________
a) Large scale propagation model
b) Small scale propagation model
c) Fading model
d) Okumura model
Explanation: Large scale propagation model are useful in estimating the radio coverage area of a transmitter. They can predict the mean signal strength for an arbitrary transmitter-receiver (T-R) separation distance. They characterize signal strength over large T-R separation distances
3. Propagation model that characterize rapid fluctuation is called _________
a) Hata model
b) Fading model
c) Large scale propagation model
d) Okumura model
Explanation: Fading models characterize the rapid fluctuations of the received signal strength over very short travel distance (a few wavelengths) or shot time durations (on the order of seconds).
4. Small scale propagation model is also known as _________
a) Fading model
b) Micro scale propagation model
c) Okumura model
d) Hata model
Explanation: Small scale propagation model is also called fading model. Fading model characterize the rapid fluctuations of the received signal strength over very short distance of a few wavelengths or short time duration. The propagation models are used to estimate the performance of wireless channels
5. Free space propagation model is to predict ______
a) Received signal strength
b) Transmitted power
c) Gain of transmitter
d) Gain of receiver
Explanation: Free space propagation model predicts the received signal strength when there is an unobstructed line of sight path between transmitter and receiver. It assumes the ideal propagation condition that the environment is empty between the transmitter and receiver
6. Which of the following do not undergo free space propagation?
a) Satellite communication system
b) Microwave line of sight radio links
c) Wireless line of sight radio links
d) Wired telephone systems
Explanation: EM signals when traveling through wireless channels experience fading effects due to various effects. But in some cases the transmission is with no obstruction and direct line of sight such as in satellite communication, microwave and wireless line of sight radio links
7. The free space model predicts that received signal decays as a function of _________
a) Gain of transmitter antenna
b) T-R separation
c) Power of transmitter antenna
d) Effective aperture of the antenna
Explanation: As with most large scale radio wave propagation models, the free space model predicts that received signal decays as a function of the T-R separation distance raised to some power. Often it is given as a function of negative square root of the distance.
8. Relation between gain and effective aperture is given by ______
a) G=(4πAe)/λ2
b) G=(4π λ2)/Ae
c) G=4πAe
d) G=Ae/λ2
Explanation: The gain of the antenna is proportional to effective aperture area. Therefore, antennas with large effective apertures are high gain antennas and have small angular beam widths. Most of their power is radiated in a narrow beam in one direction, and little in other directions
9. Relation between wavelength and carrier frequency is _________
a) λ=c/f
b) λ=c*f
c) λ=f/c
d) λ=1/f
Explanation: Wavelength is inversely proportional to carrier frequency. For electromagnetic radiation in free space, wavelength is a ratio of speed of light (c) and carrier frequency (f). Speed of light is 3*108 m/s. The unit for wavelength is meters.
10. Which of the following antenna radiates power with unit gain uniformly in all directions?
a) Directional antenna
b) Dipole antenna
c) Isotropic antenna
d) Loop antenna
Explanation: Isotropic antenna radiates the power with unit gain uniformly in all directions. It is an ideal antenna. From practical point of view, there is no actual isotropic antenna. But, an isotropic antenna is often used as a reference antenna for the antenna gain.