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Down conversion -- Simulink !! Help Me !!

Down conversion -- Simulink !! Help Me !!

Down conversion -- Simulink !! Help Me !!

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.??

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