Microstrip simulation in ADS Momentum

Hi all!

I want to simulate a microstrip line using ADS Momentum layout.
ADS momentum simulates a device inside a box. If i am correct this box is assumed to have infinite conductivity. the structure that i want to simulate is a microstrip line on an FR4 substrate. From the substrate definition in momentum i can define a FR4 layer and a conductor layer on the top on which the microstrip is drawn. For practical purposes, I want to define the ground layer as a copper layer with finite conductivity. so in effect the layers look like


air
conductor1
FR4
conductor2
air

this is placed inside the momentum box for simulation

however the stack up expected is

conductor1
FR4
cond2

can somebody help me as to how the layers should be defined. if i do not define a cond2 layer then momentum assumes an infinite ground plane but then the simulations deviate from fabrication.

thanx in advance.

You can view the 3D preview.Wha you said is lack the air layer?

The stackup that i need is

freespace
copper
fr4
copper

for taking copper as my ground plane i need to add one more dieletric layer. so i am forced to use
freespace
copper
fr4
copper
freespace

when i view this stackup in 3D an additional dielectric is added in the box and it looks like a stripline structure

can u help me in defining the ground plane as copper without the addition of additional dielectric layer.

No. Box refers to FFT-MoM based simulators like Sonnet, which have metal side walls that limit the analysis area.

Momentum is Method of Moment with open boundaries. There are no conducting side walls.
For the top and/or bottom, you can choose "free space" which is an absorbing boundary.
You can also define a finite conductivity for the /// GND /// layer.

Actually for microstrip line using infinite ground of momentum gives pretty accurate results. For comparison in mom.pdf document (which is in the installation folder of ADS) results of finite and infinite ground are compared with measured and infinite ground one is more accurate.

You can do following for getting accurate results:

1) increase your mesh frequency, use thick conductors.
2) If your actual microstrip line is inside a box, then add a box to your simulation. (most probably this is your case)
3) Conduct a de-embedding for your measurement.