SIGNAL DETECTING CIRCUIT USING NOISE AGC

摘要

PURPOSE:To facilitate threshold discrimination which corresponds to variation in input level by using the correlative output of a code out of phase with an input signal as a noise level reference. CONSTITUTION:The 1st and 2nd correlators 2-1 and 2-2 are applied with the output of a variable gain amplifier 1 which inputs a periodic signal modulated by a code having excellent correlation. The 1st circuits (4-1 and 5-1) amplify and detect the output of the correlator 2-1. An integrating circuit 6 integrates the outputs of the circuits (4-1 and 5-1). An AGC amplifier 9 amplifies the output of the circuit 6 to control the gain of the amplifier 1. The 2nd circuits (4-2 and 5-2) amplify and detect the output of the correlator 2-2. An integrating and discharging circuit 7 having a time constant smaller than that of the circuit 6 integrates the outputs of the circuits (4-2 and 5-2). A threshold discriminating circuit 8 discriminates the output of the circuit 7.