Photodetector circuit for the detection of weak radiant signals in the presence of a large signal background

Claim 1

A PHOTODETECTOR CIRCUIT FOR IMPROVING THE DETECTION OF WEAK RADIANT SIGNALS IN THE PRESENCE OF LARGE SIGNAL BACKGROUND, COMPRISING: (A) A PHOTOETECTOR, (B) A PHOTODETECTOR LOAD IMPEDANCE CONSISTING OF A TRANSISTOR CIRCUIT HAVING HIGH COLLECTOR A.C. IMPEDANCE AND RELATIVELY LOW D.C. IMPEDANCE CONNECTED IN SERIES WITH SAID PHOTODETECTOR. (C) A SOURCE OF D.C. BIAS SUPPLY VOLTAGE CONNECTED TO SAID PHOTODETECTOR AND SAID TRANSISTOR AND IN SERIES THEREWITH, (D) A POSITIVE FEADBACK NETWORK INCLUDING IN SAID TRANSISTOR CIRCUIT FOR INCREASING THE IMPEDANCE THEREOF OVER A NARROW BAND OF FREQUENCIES WITH IMPROVEMENT IN SIGNAL TO NOISE RATIO, (E) SAID PHOTODETECTOR BEING OPERABLE TO DETECT RADIANT ENERGY SIGNALS WHICH IMPINGE THEREON AND GENERATE AN OUTPUT IN RESPONSE TO SAID REDIANT ENERGY SIGNALS, (F) ANY SHORT CIRCUIT WEAK SIGNAL CURRENT OF SAID PHOTODECTOR NOT BEING SIGNIFICANTLY AFFECTED BY THE PRESENCE OF A LARGE STEAD STATE RADIANT SIGNAL BACKGROUND AND DEGRADATION OF SAID WEAK SIGNAL TO WHERE THE SAID WEAK BECOMES LESS DETECTABLE AND FINALLY DEGRADES TO VIRTUALLY ZERO BEING LACKING.