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phase -180 -> +180 suddenly, why?

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asicpark

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Hi all,

Running the AC simulation to check the stability. I have a question.

The phase line is changed abruptly from -180 to +180 at certain frequency.

Is that real situation or just calculation bug?

I don't know how to avoid it.

Thanks in advance.
 

i am not really sure but 180 is the same as -180
 

asicpark said:
Hi all,

Running the AC simulation to check the stability. I have a question.

The phase line is changed abruptly from -180 to +180 at certain frequency.

Is that real situation or just calculation bug?

I don't know how to avoid it.

Thanks in advance.

Not a bug, is more or less common methode to handle angle in many simulators and math programs.

I think your programs using complex numbers inside, and from this is impossible to make angle outside -180 -> 180 degree (or 0-380, 0- -380 degree).

Retangular notation cannot store 'turns' ( ex 900 degree for 2-1/2 turn) same way as magnitude and angle in polar notation. Most math and simulator program using modulo 360 on angle part in convert moment from polar notation to retangular notation.
 

Is there any option command in Hspice to avoid the change phase?
 

actually i think it happened to me with spectre once
 

asicpark said:
Is there any option command in Hspice to avoid the change phase?
Yes.
Code:
.option unwrap
You will get a continuous phase plot.
 

i also encountered this problem, but im using spectre. how and where can I use the command?

thanks
 

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