If you are a microwave hardware engineer, you most likely have had a few sobering experiences when testing your new design the first time. This is particularly true for wideband high frequency modules — they almost never look like the model.
Many of the bigger issues come down to physics. Broadband modules (2 to 18 GHz) virtually always have gain roll-off at the high end of the band. This is due to a combination of factors: transistor and package parasitic inductors (L) and capacitors (C) give rise to gain roll-off and VSWR mismatch losses, and interconnect transmission lines have increasing loss with frequency.