Application Of Flux Sensor Based On Superconducting Quantum Interferometer

As we all know,the detection and search of enemy submarines that sneak into certain sea areas is the focus of national defense.At present,the exploration technology mainly includes sonar,infrared and magnetic anomaly detection.The former two are highly susceptible to interference under complex hydrogeological conditions.Magnetic anomaly detection has strong anti-interference ability under these conditions.The use of a superconducting quantum interference device(SQUID)as a magnetic detection sensor is currently the most sensitive magnetic measurement device,and has a prominent application in underwater magnetic anomaly detection.This paper first introduces the basic concepts,research background and development trends of SQUID;then explains the theoretical basis and circuit working principle of SQUID;then gives the overall scheme of magnetic flux sensor based on SQUID,magnetic The design and implementation of the sensor circuit are described in detail,including the RF part of the flux sensor,the analog modulation board circuit and the digital control part.Finally,the whole flux sensor system is tested and analyzed.The RF part of the flux sensor mainly introduces some key module designs,including low noise preamplifier circuit,band pass filter circuit,multiplier circuit,local oscillator circuit,low pass filter circuit,low frequency amplifier circuit and attenuator circuit,etc.In order to simulate the resonant loop output modulated signal,and the flux sensor circuit is adjusted to verify whether the sensor circuit is functioning properly,an analog modulation board circuit is specially designed.It includes circuits such as modulation signal generators,multipliers,bandpass filters,and attenuators.The digital control part mainly includes two parts: a phase locked loop and an attenuator.The experimental results show that the noise figure of the system is between 1 and 2 dB,the sweep power of the local oscillator is between-0.59 and 0.1 dBm in the range of 350 MHz to 600 MHz,in which the phase noise at 450 MHz is-126.11 dBc/Hz@100 kHz and the spurious suppression is greater than 64 dBc,the gain of the preamplifier is up to 60 dB,the multiplier demodulates normally,and the low pass filter band is 802.55 kH.Below z;low-frequency amplifiers and so on are working normally.The triangular wave results are measured by connecting the probe with the resonant loop in the dark chamber liquid nitrogen environment.By changing the magnetic flux of the probe,the value of feedback resistance and the power of bias signal,the influence of the probe on the system performance is verified to be consistent with the theoretical prediction.