## Bode plot analysis Started by 6 years ago1 replylatest reply 6 years ago168 views

I want to plot the phase vs frequency plot using the sweep signal.

My sweep signal looks like this: every cycle is of 1sec which is made up of 1msec sine burst + remaining zero volts. So, in 1st second, I am sending 1ms of 1KHz burst + 0.999sec of zero volts. In 2nd second, I am sending 1ms of 2KHz burst + 0.999sec of zero volts............in 100th second, 1ms of 100KHz burst + 0.999sec of zero volts.

I am sweeping from 1Khz to 100KHz with sampling frequency = 500K S/s.

I made phase vs freq plot using cross correlation function between RC filtered signal and original signal.  You can see the image attached. I am using cross - correlation to find the phase difference between the received signal (from the RC circuit) and original signal. I am getting accurate results for lower frequencies but bad results for higher frequencies.

Also, I made amplitude vs frequency graph using fft and got good result. But this is not the exact result. You can see the image attached.

My questions are:

1) Is bad results for phase estimation is due to the less sampling frequency? I mean, for 50KHz, the sampling freq 500K S/s is enough but for 100KHz may be it is not enough.

2) Which is better method to estimate phase difference between original and RC filtered signal? FFT or corss-correlation?

3) Can I estimate the amplitude Vs freq plot using cross-correlation? How can I estimate the amplitude of the signal from the cross-correlation data?

3 Phase_VNA_6356_Theoritical.jpg

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