Equalization and Non Coherent Detection

Question 1
Marks : +2 | -2
Pass Ratio : 100%
The disadvantage of preset equalizer is that
It doesnot requires initial training pulse
Time varying channel degrades the performance of the system
All of the mentioned
None of the mentioned
Explanation:
The disadvantage of preset equalization is that it requires an initial training period that must be invoked at the start of any new transmission. Also time varying channel can degrade system performance due to ISI, since the tap weights are fixed.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
Pseudo noise signal has _______ and _______ SNR for the same peak transmitted power.
Larger, smaller
Smaller, larger
Larger, larger
Smaller, smaller
Explanation:
A training pulse is applied to the equalizer and corresponding impulse response is observed. Pseudo noise is preferred as the training pulse as it has larger SNR value and larger average power value.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
The range of amplitude difference gives the value of
Width
Distortion
Timing jitter
Noise margin
Explanation:
In the eye pattern, the amplitude difference gives the value of distortion caused by ISI.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
The over-determined set of equations can be solved using
Zero forcing
Minimum mean square error
Zero forcing & Minimum mean square error
None of the mentioned
Explanation:
The matrix x in transversal equalizer if non square with dimensions 4N+1 and 2N+1. Such equations are called as over-determined set. This can be solved by two methods called as zero forcing method and minimum mean square error method.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
If the filter’s tap weight remains fixed during transmission of data, then the equalization is called as
Preset equalization
Adaptive equalization
Fixed equalization
None of the mentioned
Explanation:
If the weight remains fixed during transmission of data then the equalization is called as preset equalization. It is a simple method which consists of setting the tap weight according to some average knowledge of the channel.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
For AWGN, the noise variance is
N0
N0/2
2N0
N0/4
Explanation:
The noise variance out of the correlator for AWGN is N0/2.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Equalization method which is done by tracking a slowly time varying channel response is
Preset equalization
Adaptive equalization
Variable equalization
None of the mentioned
Explanation:
This method is implemented to perform tap weight adjustment periodically or continually. Equalization is done by tracking a slowly varying channel response.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
The index value n, in transversal filter can be used as.
Time offset
Filter coefficient identifier
Time offset & Filter coefficient identifier
None of the mentioned
Explanation:
The index n can be used as both time offset and the filter coefficient identifier, which is the address in the filter.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
As the eye opens, ISI _______
Increases
Decreases
Remains the same
None of the mentioned
Explanation:
As the eye closes, ISI increases and as the eye opens ISI decreases.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
Preamble is used for
Detect start of transmission
To set automatic gain control
To align internal clocks
All of the mentioned
Explanation:
The receiver uses preamble for detecting the start of transmission, to set automatic gain control, and to align internal clocks and local oscillator with the received signal.