Pulse detectors

Claim 1

A detector for detecting radio frequency input signals with varying signal levels and slowly varying carriers, comprising: positive voltage supply line; zero voltage supply line; an amplifying circuit including a first transistor for receiving and amplifying the radio frequency input signals; a first capacitor coupled to the base electrode of said first transistor for applying the radio frequency input signals to said first transistor; biasing means for providing a DC bias to put said first transistor into quiescent conducting state, said biasing means including a first voltage divider being connected to the base electrode of the first transistor and between said positive and zero voltage lines; resistive-capacitive means coupled between the emitter electrode of said first transistor and zero voltage supply line; a second voltage divider coupled between the collector electrode of said first transistor and positive supply voltage line; a second capacitor coupled between the ground and collector electrode of said first transistor; a second transistor, the base electrode of which is coupled to said second voltage divider and the emitter electrode of which is coupled to said positive voltage supply line; and a third voltage divider connected between the emitter electrode of said first transistor and the collector electrode of the second transistor, wherein said second transistor and said third voltage divider form a feedback loop, and wherein said feedback loop coupled to said amplifying circuit adjusts the level of the DC bias applied to the amplifying circuit by said biasing means to compensate for the variation in the input signal level, whereby noise signals applied at the input of said amplifying circuit are maintained below the threshold at which said first transistor conducts and thereby renders the detector immune to false triggering due to noise and makes the detector independent of the level of slowly varying carriers of the radio frequency input signals.