公开(公告)号：US3716785A

公开(公告)日：1973-02-13

申请号：US3716785D

申请日：1971-06-22

Applicant: WESTINGHOUSE ELECTRIC CORP

Inventor： MASTERS H ,  PETERS J ,  NUGENT J ,  HUNT M

IPC: G01R23/00 ,  G01R27/00

CPC classification number: G01R23/00

Abstract: APPARATUS FOR MEASURING NOISE SPECUTRA, BOTH AM (AMPLITUDE MODULATION) AND FM (FREQUENCY MODULATION), OF RF SIGNALS OVER A PREDETERMINED FREQUENCY RANGE BY SWEEPING A VARIABLE FREQUENCY SQUARE WAVE OSCILLATOR BY MEANS OF AN ANALOG RAMP SIGNAL GENERATED BY A DIGITAL SWEEPING CIRCUIT WHICH PRODUCES A SEQUENCE OF SQUARE WAVE PULSES WHOSE PULSE WIDTH INCREMENTALLY INCREASES BY THE SAME AMOUNT OVER A PREDETERMINED TIME PERIOD. THE VARIABLE FREQUENCY OSCILLATOR IS DRIVEN AND AUTOMATIC FREQUENCY CONTROLLED FROM A DIGITAL CLOCK OSCILLATOR WHICH IS ALSO FED TO A MIXER. THE MIXER IS DIRECTLY COUPLED TO A FIRST MIXER WHICH HAS INPUTS COMPRISING THE NOISE SIGNAL INPUT AND THE VARIABLE FREQUENCY OSCILLATOR SIGNAL APPLIED THERETO. THE FIRST AND SECOND MIXER CONFIGURATION PROVIDES A FREQUENCY WINDOW THROUGH WHICH THE DESIRED NOISE WAVEFORM CAN BE DETECTED AND MEASURED. THE SYSTEM SWEEPS A PREDETERMINED FREQUENCY BAND AND WHEN A NOISE SIGNAL OF PREDETERMINED AMPLITUDE IS DETECTED, THE SWEEP CIRCUIT IS AUTOMATICALLY STOPPED, THEREBY LOCKING ONTO AN INPUT SIGNAL OF EXCESSIVE NOISE LEVEL.