Experiment No.
6
Roll No. : 22 Date :
Aim : To generate eye diagram without channel noise and without a band limiting filter.
Apparatus : MATLAB software
Theory: In telecommunication, an eye pattern, also known as an eye diagram, is
an oscilloscope display in which a digital data signal from a receiver is repetitively sampled
and applied to the vertical input, while the data rate is used to trigger the horizontal sweep. It
is so called because, for several types of coding, the pattern looks like a series of eyes between
a pair of rails. It is an experimental tool for the evaluation of the combined effects of channel
noise and intersymbol interference on the performance of a baseband pulse-transmission
system. It is the synchronized superposition of all possible realizations of the signal of interest
viewed within a particular signalling interval.
Several system performance measures can be derived by analyzing the display. If the signals
are too long, too short, poorly synchronized with the system clock, too high, too low,
too noisy, or too slow to change, or have too much undershoot or overshoot, this can be
observed from the eye diagram. An open eye pattern corresponds to minimal signal distortion.
Distortion of the signal waveform due to intersymbol interference and noise appears as closure
of the eye pattern.
Graphical eye pattern showing an example of two power levels in an OOK modulation
scheme. Constant binary 1 and 0 levels are shown, as well as transitions from 0 to 1,
1 to 0, 0 to 1 to 0, and 1 to 0 to 1
An eye diagram is a useful tool for understanding signal impairments in the physical layer of
high-speed digital data systems, verifying transmitter output compliance, and revealing the
amplitude and time distortion elements that degrade the BER for diagnostic purposes. By
Department of Electronics and telecommunication Engineering, YCCE, Nagpur
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taking high-bandwidth instantaneous samples of a high-speed digital signal, an eye diagram is
the sum of samples from
superimposing the 1’s, 0’s, and corresponding transition measurements. What results is an
image that reveals the “eye” of the eye diagram, as shown in Figure
For easy viewing, the time axis in Figure 2is normalized for 2bits, with the 1 bit “eye opening”
in the center of the display and 1/2bit to the left and right of the center eye for capturing
rise/fall-time transitions. Note that any data bits in the rise/fall transitions of the digital signal
that infringe on the center of the eye opening may cause data errors and will be discussed later
in the application note.
Although the eye pattern in Figure depicts some noise and jitter, other forthcoming examples
will show data system waveforms with considerably more noise and a center eye that closes
more significantly. Generally speaking, the more open the eye is (indicated by the arrows in
the diagram), the lower the likelihood that the receiver in the transmission system will mistake
a logical 1 bit for a logical 0 bit, or vice versa. These logic decisions require a certain margin
of signal differential between the 0 and the 1 level. Noise, both amplitude and time jitter,
reduces that margin and is logically depicted in Figure as some closure of the eye opening.
The ratio of bits that have errors, compared to the overall bits, is called BER.
Figure : a ‘good’ eye pattern
Result / Eye pattern is generated without channel noise and band limiting filter.
Conclusion :
Roll No. : 22 Marks out
st of 10 Signature :
Sem/Br : 1 sem/comm. engg
Department of Electronics and telecommunication Engineering, YCCE, Nagpur
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Name of Lecturer :D.B.Bhoyar
Department of Electronics and telecommunication Engineering, YCCE, Nagpur
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