×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Down conversion -- Simulink !! Help Me !!

## Down conversion -- Simulink !! Help Me !!

(OP)
I am doing a simulation in simulink

I have a carrier signal of 455 KHz, sampling that signal at a rate of 450 KHz, so as to down convert my carrier signal to a intermediate frequency signal of frequency (5KHz).

Now, I am trying to collect samples of these 5KHz signal and I have collected 8192 samples of the signal, and I need a bin resolution of 1 Hz. So, I am padding 8192 samples with zeros. Now the length of the zero padded sequence is 2^(19). Here my bin frequency resolution is (455000/2^(19))=(0.85Hz < 1Hz).

Now I am performing a FFT operation on the 2^(19) sequence and trying to find the peak frequency using a peak search algorithm.

When I do this, the simulink is showing two results 4999.63 Hz (or) 5000.51 Hz, (since 5 KHz is not a bin frequency -- I dont know if this is the reason). The above procedure I am doing it several times always buffering 8192 samples each time and padding and finding the peak. I compare every 3 results, only if the 3 results match, I use the samples for the further purpose. So in the 3 results sometimes it is showing 4999.63 and sometimes 5000.51 due to this, there is mismatch in the results.

What should I do to avoid this ambiguity.??

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!