PMI Model No. TD-30T-SHS-218-AMP-OPT4G4D5G-40DBM is an ultra-high speed, high sensitivity threshold detector optimized for the 4.0 to 4.5 GHz frequency range.  This unit has a fixed threshold level of -40 dBm.  It is a miniature unit with TTL output logic. 

Package size 2.5"(L) x 2.0"(W) x 0.5"(H) with SMA (F) connectors.

http://www.pmi-rf.com/Products/detectors/TD-30T-SHS-218-AMP-OPT4G4D5G-40DBM.htm