Monolithic semiconductor mixer apparatus with positive feedback

Claim 1

MIXER APPARATUS COMPRISING, IN COMBINATION, A FIRST TRANSISTOR HAVING A VOLTAGE CURRENT CHARACTERISTIC CURVE WHICH IS NON-LINEAR OVER AT LEAST A PORTION OF THE CURVE, A SECOND TRANSISTOR CONNECTED TO AND RECEIVING THE OUTPUT OF THE FIRST TRANSISTOR, THE SECOND TRANSISTOR BEING CONNECTED AS AN EMITTER FOLLOWER, FREQUENCY SENSITIVE PHASE SHIFTING MEANS CONNECTED TO THE EMITTER FOLLOWER TRANSISTOR, CIRCUIT MEANS CONNECTING THE OUTPUT OF THE PHASE SHIFTING MEANS TO THE FIRST TRANSISTOR TO PROVIDE A POSITIVE FEEDBACK PATH, MEANS FOR SIMULTANEAOUSLY APPLYING AN INPUT SIGNAL AND A LOCAL OSCILLATOR SIGNAL TO THE FIRST TRANSISTOR, SAID LOCAL OSCILLATOR SIGNAL BEING OF AN AMPLITUDE SUFFICIENT TO DRIVE THE FIRST TRANSISTOR INTO SAID NONLINEAR PORTION OF ITS CHARACTERISTIC CURVE, SAID PHASE SHIFTING MEANS PROVIDING A PREDETERMINED PHASE SHIFT AT A BEAT FREQUENCY SELECTED FROM THE SUM AND DIFFERENCE FREQUENCIES OF THE LOCAL OSCILLATOR SIGNAL AND THE INPUT SIGNAL WHEREBY THE TOTAL PHASE SHIFTING IN THE FIRST AND SECOND TRANSISTORS AND PHASE SHIFTING MEANS IS SUBSTANTIALLY 360 DEGREES, AND OUTPUT MEANS CONNECTED TO THE CIRCUIT MEANS FOR DELIVERING A BEAT FREQUENCY OUTPUT SIGNAL COMPONENT.