i have noticed that your questions are basic and conceptual,may i suggest that you reinforce your theoritical background about analog design,microwave enginnering and RF circuits,you can start with G. gonzales 'microwave transistor amplifier design' for RF circuits,David pozar's 'microwave engineering' for basic microwave concepts(also a good book is Kraus/fleisisch ELECTROMAGNETICS has some good illustrations),it's a common practice to represent N port networks by their equivelent s,z,y parameters check R E collins for a good insight concerning that issue.then using @ds if u simply double click on the item of interest and press the help button it will give you a good explanation of the chosen item or at least some guiddelines to help you search for an explanation.that's how it works you learn ,read search try then ask questions ,that's what it takes to be a good designer .i have included a picture from the @ds help giving an explanation of the substarte parmeters and their physical relevance,just try harder first and good luck.
i hope this will be of some help
h0op
Parameters
H = substrate thickness, in specified units
Er = relative dielectric constant
Mur = relative permeability
Cond = conductor conductivity, in Siemens/meter
Hu = cover height
T = conductor thickness, in specified units
TanD = dielectric loss tangent
Rough = conductor surface roughness, in specified units; RMS value; refer to note 7
Cond1 = (ADS Layout option) layer on which the microstrip metallization will be drawn in layout
Cond2 = (ADS Layout option) layer on which the air bridges will be drawn in layout
Diel1 = (ADS Layout option) layer on which the dielectric capacitive areas will be drawn in layout
Diel2 = (ADS Layout option) layer on which the via between Cond and Cond2 masks will be drawn in layout
Hole = (ADS Layout option) layer on which the via layer used for grounding will be drawn in layout
Res = (ADS Layout option) layer on which the resistive mask will be drawn in layout
Netlist Format
Substrate model statements for the ADS circuit simulator may be stored in an external file.
model substratename MSUB [parm=value]*
The model statement starts with the required keyword model. It is followed by the substratename that will be used by microstrip components to refer to the model. The third parameter indicates the type of model; for this model it is MSUB. The rest of the model contains pairs of substrate model parameters and values, separated by an equal sign. The name of the model parameter must appear exactly as shown in the parameters table-these names are case sensitive. Model parameters may appear in any order in the model statement. For more information about the ADS circuit simulator netlist format, including scale factors, subcircuits, variables and equations, refer to "ADS Simulator Input Syntax" in the Circuit Simulation manual.
Example:
model Msub1 MSUB H=10 mil Er=9.6 Mur=1 Cond=1.0E50 \
Hu=3.9e+34 mil T=0 mil Tand=0 Rough=0 mil