Very low RF-DC conversion efficiency in ADS (SMS7630 & HSMS-282E)

[Cynthia001]

Simulating RF rectifier in ADS (2.45 GHz, 5 dBm). Using HSMS-282E gives 11% PCE, SMS7630 gives 21% PCE. Matching is correct (good S11). Using SPICE models from datasheets. Load = 2 kΩ. Using HB with proper Pin/Pdc equations. Why is PCE so low? What am I doing wrong, or are these values realistic? How to improve PCE in simulation?

If anyone has done similar rectifier simulations with these diodes or could give any corrections or guidance, I would appreciate. Thanks.