Three-state digital mixer-driver circuit

摘要

A mixer-driver circuit in a code correlator of a spread-spectrum communications system simultaneously multiplies an input RF signal with two phase-offset digitally encoded bit streams. A double-balanced mixer is driven with the difference of the digital signals; the mixer is either inverting, noninverting, or off. Matched ECL bistables which reclock the phase-offset bit streams, and a load current steering circuit coupled to the bistables together provide a balanced, differential drive current to the mixer which switches state faster than the bistables alone. In another embodiment, a single bistable receiving an encoded bit stream differentially drives the mixer in a biphase circuit.