How to simulate (Complex) quadrature signals in Cadence

[Megh]

Designing a complex (polyphase) filter. How can I simulate say ac analysis using complex signals in cadence virtuoso 6.1.4.

Thanks
Megh

 

[LvW]

I don' think that simulation of such a device will be specific to a certain simulation program. Why do you expect problems?
Therefore, use two separate ac sources with 90 deg phase shift and let the program compute the combined output signal.

 

[Megh]

For simulation part we can consider to apply 2 ac sources with 90 phase shift. But how would I plot the output with image frequency. How will I see how much Image rejection I am getting.?

 

[LvW]

For simulation part we can consider to apply 2 ac sources with 90 phase shift. But how would I plot the output with image frequency. How will I see how much Image rejection I am getting.?

It's quite simple: Take the inverse phase shift (-90 deg instead of +90 deg) and calculate the ratio of both outputs.

 

[laoud]

To get the image (negative frequencies), you just have to inverse the Q input. This is originated from the fact that since the I signal is cosine, then it maintaines the sign. Though the Q signal which is sine, it gives a minus at negative frequencies. So to sum up, for the Q signal instead of 0degrees you have to put 180degrees.

 

[Megh]

@ laoud and LvW
Filter is giving out I and Q signals. Since I am doing AC simulation, I and Q itself (each)are complex. Now we are interested in frequency response of I+jQ as a whole from -ve freq to + freq. This will in general create assymmetric frequency response across 0 freq.
How do we do this frequency response analysis.
Thanks!

 

[hung_wai_ming@hotmail.com]

Dear ALL

How to apply two separate ac source in Hspice with 90 degree difference for simulation?

 

[prcken]

Dear ALL

How to apply two separate ac source in Hspice with 90 degree difference for simulation?

try this for example:
vi node1 node2 1V ac 200m 90
vq node3 node4 1v ac 200m

 

[geozog86]

helpful, thx