Learning Forum

[as33dhil]

Hi,

I have a 2 port CPW line, I am designing a phase shifter using it in HFSS. I simulated a quarter wavelength CPW line but the phase at the 2nd port given by HFSS is -90 degrees. I expect it to be 90 degrees.

Can anyone please help me understand why HFSS gives a negative phase?

Regards,

Amarveer

[DMARATHE]

Hi Amarveer,

Thanks for posting your query on learning forum.

I assume, that you are assigning 2-ports to your CPW line and verifying the phase angle of S12 or S21. For lambda/4 length of line, phase (S21) should be -90 degree and HFSS is giving you correct value. Probably, you should refer some standard literature or book to understand about negative phase value.

 

 

[as33dhil]

Hi Dmarathe,

Thank you for your response. Yes, I am assigning 2-ports to the CPW line and verifying the phase angle of S21.

I understood the negative phase. I have one more concern. To explain it, I have prepared figures (attached) and also explained it below:

1. I parametrically varied the length of the CPW line on a Si Substrate (permittivity = 12) from 1478.6 um to 11828.8 um at a step size of 1478.6 um to obtain S21 phase of -45 degrees, -90 degrees, -135 degrees, and so on. However, HFSS shifts the S21 phase for some phases by +-180. I have explained the concern in detail in the attached figures. Please look in serial order as fig1, fig2, fig3 and fig4.

It would be beneficial if you could assist in understanding this adjustment in phase in HFSS. I have done the same simulation in Sonnet and got the perfect response. Sonnet results are also attached (fig4).

Regards,

Amarveer

[DMARATHE]

Hi Amarveer,

Thanks for your findings. However, regarding HFSS results, it is difficult for me to commnt without looking at model. Because of open nature of the forum, I am not suppose to ask you the model. If you have request to Ansys Technical Support, please raise a service request and our support engineer will get in touch with you.

Thanks. 

[as33dhil]

Hi Dmarathe,

Thank you for your response. Appreciate your response and help.

I am a PhD student at the University of Waterloo. I am unsure if Ansys Technical Support is available to students. I tried to contact the support via phone but got no response. Do you know if students have access to the support you referred to? If so, can you please provide me with a web link?

Regards,

Amarveer