Question

1.Choose ALL correct answers:

The benefits of smart antenna :(Group of answer choices)

(1)Improves LPI performance (low probability of interception) for base stations

(2)Reduces multiple access interference for base stations

(3)Increases battery life for a phone

(4)Increases transmission range for a phone

2.Choose ALL correct answers:

Diversity combining versus beamforming:(Group of answer choices)

(1)In diversity, signals are highly uncorrelated to achieve good performance

(2)In beamforming, signals are correlated

(3)In diversity, signals are highly correlated to achieve good performance

(4)In beamforming, signals are uncorrelated

3.Choose ALL correct answers:

According to the spatial Nyquist sampling theorem, to avoid array ambiguity, antenna spacing (inter-element spacing) should be:(Group of answer choices)

(1)smaller than or equal to half the carrier wavelength

(2)smaller than or equal to twice the carrier wavelength

(3)large than or equal to half the carrier wavelength

(4)large than or equal to twice the carrier wavelength

4.Choose ALL correct answers:

Diversity combining techniques, :

(Group of answer choices)

(1)Selection diversity: Performs better than switched diversity

(2)Switched diversity: Requires only a single RF chain to serve all its antennas

(3)Maximal ratio combining: Performs better than equal gain combining

(4)Equal gain combining: Co-phased and weighted before combining

5.Choose ALL correct answers:

In beamforming, a beam pattern is dependent on:

(Group of answer choices)

(1)Carrier frequency

(2)Antenna weights

(3)Signal strength

(4)Signal phase

Answer 1

Answer)

1) All options are correct

1-> Smart Antenna Provides the directional beam therefore the LPI performance improve

2->Smart Antenna has higher gain it desired direction hence it reduces the chance of interference

3->Smart antenna provides larger coverage with higher gain therfore it is easy for phone not to search network everytime and hence battery life improves

4->Smart Antenna provides higher coverage with higher gain and directivity therefore transmission range of phone improves.

2) option(1) and (2) are correct

-> Diversity combinig technique is used to select the best recieved signal which arrived at reciever via different path, it means multipe copies of same signal arrive at reciever, out of which some of copies fades and some signals are strong but all are uncorrelated

-> Beamforming technique is used to increase the directivity and gain by combining the correlated signals

3)option(1) is correct, smaller than or equal to half the carrier wavelength

spatial distance by nyquist criteria is given by

antenna spacing <= lambda/2

4) All Options are correct

1) Selection diversity-- selects the best signal (Highest SNR)from recieved signals from different braches whereas in switch diversity recieved signal from only from one branch.

2) Switch diversity-- use only one reciver chain to process further

3) Maximal ratio combining (MRC)-- recieve signals from all braches are optimally combined using  weighing of each brach, magnitude scaling and cophasing . this provide maximum SNR for recieved signal. which is higher than Equal gain combining

4) Equal gain combining--signals are combined optimally using cophaing and weighing branch but with constant magnitude

5) All options are correct

In Beamforming The beam pattern depends on frequncy, phase ,weight and strenght