prbs generstion
TRANSCRIPT
PRBS GENERSTION
Group 3.
Group Members:
1. Ashok Kumar Bharti 2010EE50546 2. Jitendra Meena 2009EE50483 3. Sidharth Ranjan 2010EE505
Experiment done at: 16 January, 2013 Wednesday.
ACHIEVMENTS: Introduction to the pseudo random binary sequence (PRBS) generator; time domain viewing ; snap shot and eye patterns; two generator synchronization and alignment with the sliding window correlator.
MDULES USED: Two sequence Generator, Error counting utilities.
OSERVATIION AND RESULTS:
1. The ‘snapshot’ display
The above picture shows clock (2 kHz) vs TTL output f sequence generator without using SYNC signal of Sequence Generator.
The above picture shows clock (2 kHz) vs TTL output f sequence generator using SYNC signal of Sequence Generator.
The above picture shows clock (2 kHz) vs TTL output f sequence generator with using SYNC signal of Sequence Generator. But here in this case sequence is lengthier than earlier case.
2. Band limiting
The above picture shows clock (2kHz) vs TTL output f sequence generator using SYNC signal of Sequence Generator.
The above picture shows input (below) vs output (above) to the Tunable LPF (task 10) Notice here that output of the LPF has some disturbance at corners.
Bandwidth of LPF is at maximum position of the module given.
The above to consecutive pictures are showing input vs output to LPF at different bandwidth (Task 11). Bandwidth in the lower picture is lesser than the above one.
Here we noted down corner frequency of output at various decreasing bandwidths:
a. 4917.1214 Hz b. 4197.2695 Hz c. 2278.4785 Hz
3. Two generator alignment:
The above two pictures are showing output of two generators which are not synchronized by sync (task 14). The both the generators have only same bit clock. Here we can see that output of the both generator are synchronized in time but not aligned in data because of simple reason that they share same clock but not synchronized by any of the SYNC.
In the above picture outputs of two sequence generators are shown (task 15). Here both the outputs are identical because generators are synchronized by SYNC and same bit clock.
The above picture is taken after the alignment of two generators but the synchronization link is broken thereafter.
Here we concluded that even after breaking of this link, generators are synchronized because of sharing of the same bit clock.
4. Two Sequence Alignment:
The above two consecutive figures are showing output of two sequence generators which are not aligned (task 19). The two generators have a gap of a channel in between therefore we can do alignment by connecting SYNC of one to Reset of other.
In the above figure the above line regarding to channel 1 is output of ERROR COUNTING UTILITY (XOR gate) (task 20). Here inputs to the XOR gate are the two outputs of sequence generators.
After joining the output of XOR gate to the Reset of the second generator, we saw that output of the XOR gate is a straight line (task 22). This happens because at each step of XOR gate generator 2 reset itself and does so until it aligned with first generator.
And finally the above picture is showing the alignment of the sequence generators (both are producing short length sequence N=2).
Alignment of the two generators by XOR gate with lengthy sequence N=5.
Conclusion:
a. In band limiting with decrease in band limit corner frequency also decrease, Delay time increases and identification of individual bit becomes more difficult.
b. It is very difficult to align the two generators manually by pressing RESET button repeatedly. c. Once the two generators are aligned, they will remain aligned even after the alignment link
between them is broken. The bit clock will keep them in step. d. When two generators are aligned by the XOR gate method, output of the XOR gate becomes
straight line which is very obvious. If we rest any of the generators now onwards the straight line disappears only for very short time.