Square wave symmetry control circuit for use in magnetometer readout circuits

Abstract

Abstract THE READOUT CIRCUIT COMPRISES IN SEQUENCE A LIMITER, A SQUARE WAVE SYMMETRY CONTROL CIRCUIT, A FREQUENCY DISCRIMINATOR AND A TRANSIENT SUPPRESSOR. THE FREQUENCY AND AMPLITUDE MODULATED SINUSOIDAL MAGNETOMETER SIGNAL IS TRANSLATED INTO SQUARE WAVES BY THE LIMITER. SINCE THE AMPLITADE MODULATION WOULD CAUSE THE SQUARE WAVES TO BE ASYMMETRICAL AND DEGRADE THE PERFORMANCE OF THE CIRCUIT, THE SQUARE WAVE SYMMETRY CONTROL CIRCUIT GENERATES AN ERROR SIGNAL WHICH IS USED TO ELIMINATE THE EFFECTS OF AMPLITUDE MODULATION. THE FREQUENCY DISCRIMINATOR PRODUCES AN OUTPUT SIGNAL WHICH VARIES IN ACCORDANCE WITH THE INPUT FREQUENCY FROM THE MAGNETOMETER. THIS OUTPUT SIGNAL WHEN PLOTTED AGAINST INPUT FREQUENCY COMPRISES A RAMP OR SAWTOOTH, WITH A PERIOD OF 1000 HZ., SUCH THAT THE SAWTOOTH REPEATS FOR EACH 1000 HZ INCREMENT OF INPUT FREQUENCY. A SECOND PHASE DETECTOR PRODUCES AN IDENTICAL SAWTOOTH OUTPUT SHIFTED IN FREQUENCY BY 500 HZ. WITH RESPECT TO THE FIRST. A LOGIC SWITCH SENSITIVE TO THE AMPLITUDE OF EACH OF THE SAWTOOTH WAVES SWITCHES THE FOLLOWING CIRCUITS BETWEEN THE FREQUENCY DISCRIMINATOR OUTPUTS TO AVOID SIGNAL DISTORTIONS WHICH DEVELOP AT THE TRANSITION POINTS OF THE SAWTOOTH WAVES. A TRANSIENT SUPPRESSOR PREVENTS TRANSIENTS FROM SATURATING THE FOLLOWING FILTER CIRCUITS WHEN DIFFERENT DC LEVELS EXIST ON THE DISCRIMINATOR OUTPUTS AT THE TIME OF SWITCHING. BY FEEDING BACK THE SIGNAL BEING MONITORED TO THE OUTPUT OF THE UNUSED CHANNEL OF THE FREQUENCY DISTRIMINATOR, THE SAME SIGNAL IS FORCED TO BE PRESENT ON BOTH CHANNELS WHEN SWITCHING TAKES PLACE.

Inventors

• 👤 Richard A Mcbride
• 👤 Reginald S Herbert
• 👤 Warren S Weintraub

Bibliographic Details