Filtering a RF Signal in Labview

[jstarustka]

Hello Sastry,

I specify 100kHz for the IQ rate and that is what the actual returns to me.  You are correct in assuming that the I and Q data sets are arrays of real numbers that I changed into complex values and merged into a single array to feed the filter vi.  I did not get the picture you spoke of in your last posting.

Thanks

Joe

[jstarustka]

I specify 100kHz and that is what the actual turns out to be also.  Yes the I and Q data are arrays of real values which I change to complex arrays and combine into a single array for the filter vi.  I did not receive the picture you spoke in your last posting.

Thanks

Joe

[Sastry]

Oops. I thought it got attached. I am sorry not attaching. Here it is... Look at the picture while referencing to my post.

[jstarustka]

Thanks, I am now seeing the correct signal on the spectrum analyzer but I am still not seeing that the filter is having any effect on the signal.  The sidebands remain present.  Any suggestions?

Thanks

Joe

[Sastry]

Hi Joe,

The sidebands might be happening within the filter passband.

• Try reducing the alpha (that you have currently set to (0.4)
  
• Which spectrum analyzer are you using? IF NI RFSA, then assuming that you might be modulation toolkit example, have you set the filter correctly? If you are non-NI spectrum analyzer, check that you have set the reference filter etc. correctly.
  
• If no receive filter, then try Raised Cosine on transmit side.
  

That was kind of hand wave suggestions. Let me know how it goes.

[jstarustka]

I changed some of the values on the filter and everything is working great. The sidebands are gone!!!

Thanks for all of your help, I appreciate it.

Joe

[Sastry]

Fabulous. All the best with your application.

If you get a chance, please do let us know about your application. I would love to know.