Hello.
I am trying to use momentum to simulate a simple case of two quarter wavelnegth (fo = 1.9 GHz) microstrip lines running parallel to each other on top of a PCB substrate, with a separation distance of 9 mil between the two lines.
Main simulation parameters are as follows:
Mode: MW mode.
Frequency: 1 Hz - 10 GHz
Ports: 4 single ended edge ports
However, during simulation, momentum gives the following warning:
WARNING : S-parameter results show unphysical behavior for certain frequencies.
Cause : - inaccurate (high frequency) calibration ;
- higher order modes at the ports ;
- slot mode at coplanar ports ;
- grouped strip-slot ports ;
- too coarse of a mesh.
When I check the resulting s-parameters, I find S11 greater than unity at around 6 GHz. If I try to simulate the same case with RF mode, the warning message disappears and all reflection parameters are less than unity.
Any hints?
Regards,
/Shadi Yousef
I am trying to use momentum to simulate a simple case of two quarter wavelnegth (fo = 1.9 GHz) microstrip lines running parallel to each other on top of a PCB substrate, with a separation distance of 9 mil between the two lines.
Main simulation parameters are as follows:
Mode: MW mode.
Frequency: 1 Hz - 10 GHz
Ports: 4 single ended edge ports
However, during simulation, momentum gives the following warning:
WARNING : S-parameter results show unphysical behavior for certain frequencies.
Cause : - inaccurate (high frequency) calibration ;
- higher order modes at the ports ;
- slot mode at coplanar ports ;
- grouped strip-slot ports ;
- too coarse of a mesh.
When I check the resulting s-parameters, I find S11 greater than unity at around 6 GHz. If I try to simulate the same case with RF mode, the warning message disappears and all reflection parameters are less than unity.
Any hints?
Regards,
/Shadi Yousef
When I checked it turned out when I generated the layout automatically from my schematic, the substrate definition was missing the bottom ground plane for some reason. I ran the automatic layout generation again and the ground plane was there, and the error message was gone.
/Shadi Yousef