PN sequence Generation

[schizo2]

How to generate a PN sequence in LABVIEW. PN pseudorandom sequence generates a sequence of pseudorandom binary numbers. A pseudonoise sequence can be used in a pseudorandom scrambler and descrambler. It can also be used in  spread-spectrum system.

[LV_Pro]

Is there a reason that you can't use LabVIEW's built in random number generator? It is by definition (I researched this about 12 years ago, am fuzzy about the details) a PRN generator. Now if what you are looking for is something that generates a predictible, repeatable PN, well don't think it would work in that case.

[rpursley8]

The NI Modulation Toolkit has that feature.

[stevem181]

PRNGs (aka PRBS) are usually based on Linear Feedback Shift Registers (LFSRs) so a search on LFSRs is a good idea to see the theory behind them.

One difference with LFSRs and the LabVIEW "dice" (which does output pseudorandom numbers) is that LFSRs can't output an all zero state. A seed value is used to start the sequence (and this can't be all zeros either).

Here is an 8 bit LSFR:

Note that the rotate array function is only there for aesthetic purposes.

The same output will always be returned for a given seed value and iteration count of the For loop.

steve

[Mink]

Respected sir,

how 511 pn sequence can be truncated to 500 ?

With regards

[stevem181]

Hi,

I'm not sure what you are asking here:

> how 511 pn sequence can be truncated to 500 ?

So you have a PN sequence of 511 items and you want to reduce this to 500 items?

How is your sequence generated (attach code if possible)?

Assuming your sequence comes in an array, couldn't you just use Reshape Array to remove the extra items?

steve

[Mink]

Respected sir,

After generating a pn sequence of n=9 ,length=2^n - 1=511 , i need to reduce this length to 500, by truncating the last 11 MSB's of this sequence. What is the possible solution for this ?

thnx,

with regards

[LV_Pro]

Your data is an array of length 511, run it through a "Delete from Array" function, deleting either the last 11, or last 500, depending on which end of the array is the 500 elements you desire. In the first instance the resulting "main" array output will be the first 500 elements, in the second the "deleted" output will have the last 500 elements.

[Mink]

I am obliged for this solution, sir.

Thank you.

Regards

[Bagus77]

sorry sir , may i ask the components in your PN sequence . I didnt fint a component  right from  Reverse 1D Array . What the name component this?