As I mentioned earlier, you can work out the resistive equivalent of the resistive matching network and the diode when it is in the hot state. Just put the 15R (hot diode resistance) in parallel with the 22R? and then put this in series with 34R. You end up with about 43 ohms resistance.
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I suppose this ought to be 50 ohms but maybe it is a compromise because the ESR of the blocking cap and the connection path will rise with frequency (could be several ohms by 18GHz) and also you have to factor in the impact of the open stub matching section (not shown) up at higher frequencies. The open stub shouldn't affect the simulation below 20MHz so I didn't include the 30 ohm resistor or the stub. Only the original designers at HP will know for certain why these values for the matching resistors were chosen.?
