Standard source comparison system for high-frequency voltage ratio meter including alternately connectable load terminations

Claim 1

IN AN INSERTION LOSS TEST SYSTEM COMPRISING A HIGHFREQUENCY SIGNAL GENERATOR, A STANDARD SOURCE OF I.F.; A LOCAL OSCILLATOR; A MIXER FOR BEATING THE OUTPUT OF SAID GENERATOR WITH THE OUTPUT OF THE LOCAL OSCILLATOR TO PROVIDE A BEAT FREQUENCY OUTPUT OF THE SAME FREQUENCY AS THE STANDARD I.F. SOURCE; AN I.F. AMPLIFIER; AND MEANS FOR ALTERNATELY SUPPLYING THE OUTPUT FROM SAID STANDARD SOURCE AND FROM SAID MIXER IN COUNTERPHASE TO SAID I.F. AMPLIFIER FOR COMPARISON DURING CONTINUOUS-WAVE OPERATION OF BOTH THE MIXER AND THE STANDARD SOURCE, COMPRISING TRANSFER MEANS FOR ALTERNATELY SUPPLYING EACH OF SAID OUTPUTS TO THE I.F. AMPLIFIER IN TURN, AND MEANS FOR SUPPLYING THE OTHER OF SAID OUTPUTS TO A RESPECTIVE LOAD TERMINATION FOR EACH DEVICE, DURING THE ALTERNATE PERIODS WHEN THE OUTPUT OF EACH DEVICE IS NOT SUPPLIED TO THE I.F. AMPLIFIER, EACH SAID LOAD TERMINATION BEING OF THE SAME VALUE AS THE LOAD SEEN BY THE DEVICE DURING THE INTERVAL WHEN ITS OUTPUT IS SUPPLIED TO THE I.F. AMPLIFIER, WHEREBY THE MIXER AND THE STANDARD SOURCE ARE RESPECTIVELY UNDER CONSTANT LOAD DURING THE COMPARISON.