Siemens Aktiengesellschaft

Alfred Nist

Georg Sebald

A 1 bit/1 bit digital correlator includes a digital multiplier stage and an analog integrator stage, the analog integrator stage having a feedback loop for automatically adjusting a reference voltage for the integrator. The digital multiplier may be an exclusive OR gate which combines two incoming digital sequences and generates a digital output sequence which is divided into two paths in the integrator stage, one path being utilized for obtaining the reference voltage for the integrator and the other path forming a signal path for the integrator. The reference voltage path includes a switch operated by a refresh signal for selectively completing an RC network which is connected to the non-inverting input of an operational amplifier. The signal path includes a low-pass filter connected through a resistor to the inverting input of the operational amplifier, the operational amplifier having a capacitor connected across its output and its inverting input. A feedback loop for resetting the integrator stage is also connected between the output of the first operational amplifier and its inverting input and includes a second operational amplifier having an output selectively connectable through a further switch to the inverting input of the first operational amplifier, and having an inverting input to which a reference starting voltage is supplied and a non-inverting input connected to the output of the first operational amplifier.

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Grafrath, Germany

Alfred Nist