The Designer's Guide Community
Forum
Welcome, Guest. Please Login or Register. Please follow the Forum guidelines.
Mar 28th, 2024, 9:46pm
Pages: 1
Send Topic Print
Two tone TEST to check intermodulation (Read 4654 times)
yagi
New Member
*
Offline



Posts: 6

Two tone TEST to check intermodulation
Jan 26th, 2007, 6:03am
 
Hello everyone,
     I am trying to do a intermodulation simulation for my system giving two sinusoidal frequencies at 20Mhz.   But I dont know what two input frequencies to feed into my system to get the output spectrum using DFT function in spectre calculator. I tried feeding 20 and 19Mhz signals and did a DFT with hamming window but the two tones in spectrum are spread into bins on both sides.

  Can anyone help me how to do this test and see the output spectrum with two singal tones and intermodulated tones.

 Thanks,
  Yagi
Back to top
 
 
View Profile   IP Logged
Ken Kundert
Global Moderator
*****
Offline



Posts: 2384
Silicon Valley
Re: Two tone TEST to check intermodulation
Reply #1 - Jan 26th, 2007, 7:18am
 
I believe the spreading is caused by the use of the Hamming window. With sinusoidal signals you should not need to use a windowing function.

-Ken
Back to top
 
 
View Profile WWW   IP Logged
ACWWong
Community Fellow
*****
Offline



Posts: 539
Oxford, UK
Re: Two tone TEST to check intermodulation
Reply #2 - Jan 26th, 2007, 7:55am
 
and you'll want to ensure the dft is over an interval that is a integer multiple of 1 us to get the right bin spacing for a 20MHz-19MHz = 1MHz....
Back to top
 
 
View Profile   IP Logged
Croaker
Senior Member
****
Offline



Posts: 235

Re: Two tone TEST to check intermodulation
Reply #3 - Jan 28th, 2007, 12:37pm
 
Yup, if it helps, the points are spaced by fsampling/N where N is the number of points used in the FFT.
Back to top
 
 
View Profile   IP Logged
Pages: 1
Send Topic Print
Copyright 2002-2024 Designer’s Guide Consulting, Inc. Designer’s Guide® is a registered trademark of Designer’s Guide Consulting, Inc. All rights reserved. Send comments or questions to editor@designers-guide.org. Consider submitting a paper or model.