No I'm not forgetting the source impedance but when comparing this Port to the Port in Cadence, in Cadence, the port generates twice the input voltage level so that at matching condition, the load receives the specified input power. for example, if the input power is 1mW, then that means Vpeak is equal to 316mV at matching conditions, so the port will generate 632 input voltage so that the load receives the full 1mW input power