phase VS frequency block !!!

Hello,

I’m looking for a block that it can show me the phase of a signal (rad) versus the frequency (Hz), for example a block similar at the spectrum scope but the y axis is the phase (rad) and not the gain (dB). Thanks a lot, Be good.

Answer 1

[Rick Rosson]

FFT and Phase/Magnitude Blocks

You can use the "FFT" block to convert the signal from the time-domain to the frequency domain, followed by the "Complex to Magnitude-Angle" block to compute the phase in radians. If you know the sampling rate, you can compute the corresponding frequency doemain, and then plot the phase versus frequency using the "XY Graph" scope block.

[al-comm]

Thanks Rick, i was using the block to convert from complex to phase and magnitude, but the phase values were not good, then i write a Matlab code and using “ to workspace” block I can plot the fft of the phase, but even this method didn’t give the good amplitude of the phase.

See this graph: http://img713.imageshack.us/img713/9451/ffti.png

N.B: the XY graph block is not very useful in this case I think, because I want to see the amplitude of the phase of each frequency.

Thanks again,

Bye

[Rick Rosson]

I am confused. Do you want to see _Amplitude_ versus Frequency, or do you want to see _Phase_ versus Frequency? I do not know what you mean by "amplitude of the phase"...

[al-comm]

Hello,

Ok, what i want to see is:

X axis: frequencies (Hz)

Y axis: phase (rad)

But i want to see a graph similar at the graph added in my comment upstairs and not the XY graph because it’s not showing the different frequencies.

In my graph, at 1 GHz (1*10^9) I’m supposing find this value 1.57 rad ( 900 ) and not 0.94.

So I’m asking why this value is not correct if I’m using only the “complex to phase “ block and “ to work space “ to be plotted in Matlab?! And if there’s a method or block to see this type of graphs without using a Matlab code !?

Thanks again.

[al-comm]

correction: 1.57 rad or ( 90 degrees) not (900)

Answer 2

[Rick Rosson]

MATLAB Function Block

Another possibility would be to use the MATLAB Function Block (R2011a or later) or the Embedded MATLAB Function Block (R2010b or earlier) to compute the FFT and to plot the phase versus the frequency. Again, you will need to know the sampling rate to be able to compute the frequency domain.