RLS for system identification: problem in creating a signal + noise input.

i have successfully implemented the RLS algorithm in labview, but i am having alot of trouble generating an input. at first i used a ptbypt sine input and wired it to my FIR Filter (win coeff ptbypt) and to my data queue (ptbypt) to generate U(n). When i plot the adjusted weights they give a perfect Sinc Function.
So, after this i add in a gaussian White noise VI (ptbypt) and add it's output with the output of the sine wave VI (ptbypt) and like before wire the output of the summation to the FIR Filter and the data queue point by point. The problem that is occurring is that my tap weights after becoming constant do not change. they are the same for when i enter the sine wave alone and when i enter the sine wave with the gaussina white noise, tap weights are same. they only change when i change the low cutoff of the FIR FIlter.
its would be very much appreciated if someone may help me solve this problem i am having. I made the RLS (for system identification) as Final Year Engineering Project.

the input is a sine wave , the sine wave passes through a system which incorporates a noise in it (we say the noise incorporated by the system is the Gaussian white noise) the corrupted input enters the system , the filter weights are adjusted by the algo, and a sine waveform is extracted filtering the noise.
what kind of LTI system. Can you please elaborate? and i cant switch to LMS my project is RLS.

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Attachments:
Test1_RT.vi ‏186 KB

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RLS for system identifica​tion: problem in creating a signal + noise input.

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RLS for system identification: problem in creating a signal + noise input.