Total independent side-band signal test and response analysis system

Claim 1

A CIRCUIT ARRANGEMENT FOR THE MEASUREMENT OF INTERMODULATION DISTORTION OF AN INDEPENDENT SIDEBAND TRANSMITTER HAVING: A PAIR OF VARIABLE GAIN MODULATING CHANNELS, A LINEAR COMBINER CONNECTED TO RECEIVE THE OUTPUTS OF SAID CHANNELS AND A COMMON IF-RF TRANSMITTER OUTPUT STAGE CONNECTED TO THE OUTPUT OF SAID COMBINER, WHICH COMPRISES MEANS FOR GENERATING A PAIR OF SWEEPING SIGNALS F1 AN F2 WHEREIN F2 IS SWEPT AT TWICE THE RATE OF F1 AND F2 IS AUDIO SHIFTED WITH RESPECT TO F1 BY AN AMOUNT N WHEREIN N IS AN ODD ORDER OF INTERMODULATION DISTORTION FIMN TO BE MEASURED, AND HAVING AN OUTPUT CONNECTED SIMULTANEOUSLY TO THE INPUTS OF SAID CHANNELS, A STABLE FREQUENCY TRANSLATOR CONNECTED TO THE OUTPUT OF SAID COMMON STAGE AND TRANSLATING THE INPUT THERETO TO A FIXED INTERMEDIATE FREQUENCY, AN ACTIVE SELECTIVE FILTER MEANS FOR PASSING ONLY THAT BAND OF FREQUENCIES BETWEEN THE NTH ORDER INTERMODULATION TERMS (FIMN) AND INCLUDING SAID TERMS AND HAVING A PAIR OF OUTPUTS, ONE OF SAID OUTPUTS BEING THE UPPER SIDEBAND OF FIMN TERMS AND THE OTHER THE LOWER SIDEBAND FIMN TERM, INDICATING MEANS CONNECTED TO RECEIVE BOTH OF SAID OUTPUTS OF SAID FILTER AND SIMULTANEOUSLY INDICATING THE AMPLITUDES THEREOF AS A FUNCTION OF FREQUENCY OF SAID SIGNALS.