The S-parameters for the HMC637ALP5E, do they include the drain Bias Tee? ,( see page 9 in the datasheet)
In other words, does the S-parameters refer to the pins 5 and 21 on the chip, hence the Bias Tee has been de-embedde.
What is the dimension of the via, below the chip on the eval board? (see gerber file)