Looking for some resources about RF power detectors

Now I design a detector frequence from 2GHz to 18GHz.I need detect the RF power below -50dBm directly.I use tunnel diode.But now it only can detect -30dBm signals.Please give me some advise or papers about the detector.

Thanks a lot.

check avagotech website they have alot of appnotes about RF power detectors usign schotky diode

khouly