I can't understand meaning of your question.

tempora123 wrote on Feb 24^th, 2009, 9:51am:
What do you mean by forward power ?

If you mean decomposition of power to incident and reflected power, incident power is equivalent to available power of Signal Generator(=port in EDA Tool).

By using actual instruments such as Signal Generator, Directional Coupler, Power meter, etc., show maesurement diagram you want to emulate in EDA Tool.

http://www.designers-guide.org/Forum/YaBB.pl?num=1235554986/0#0
It seems that you don't understand incident(forward), reflected(reverse) powers and power dissipated in load and very basic RF common sense.

Pdis=Pinc-Pref=Pinc*(1-abs(Gamma)**2)

Here
  Pinc=incident(forward)Power=Available Power,
  Pref=reflected(reverse) Power,
  Pdis=power dissipated in load or terminal power(power delivered to load),
  Gamma=Voltage Wave Refelection Coefficient.

Power setting value of actual Signal Generator or Port in EDA Tool is incident power, that is, available power. It is not Pdis.

How do you define Pdis in transient analysis ?
Even though you use single tone sinusoidal drive, voltages and currents at terminal of load are never single tone.
So it is fairly difficult to keep constant value of Pdis for any frequency and any load.
But it is possible. At least you can do it by Cadence Spectre if you have correct and wide RF knowledge.