Gain Margin and Phase margin in Matlab

[Irfansw07]

Can anybody plz give me this answer in Matlab :

If I have poles give as 100Hz, 1 MHz and 10 MHz and loop gain as 10^4 than what is Gain Margin and phase margin ?
And can plz tell how to calculate in Matlab ?

Thanks in advance

 

[steinar96]

Use the function margin to aquire the phase and gain margin.

 

[Irfansw07]

I have use it as Margin command and tf command also with num & den command but when I compare with text book result the answer is not same as here the both GM and PM is infinite ...
I was wondering if there is something to do with value being taken ?

 

[ic98]

Your problem is solved using zpk function rather tf one.
run..
[xx,xx,xx,xx]=margin(sys)
where..
sys=zpk([],[-1e2 -1e6 -1e7],1e4)
hence gm is so great and pm is inf.

 

[Irfansw07]

I can see that the ωpc values remain same but with ur code its in rad/s but in book it is MHz.Also Gain margin is still different and phase margin is still invalid as compare to textbook result ...
I wonder can it be related to pi value insertion or r we have to assume this value as correct ?

Thanks in advance