Inductive magnetic sensor pre-amplification module based on differential transimpedance form

Abstract

The invention provides an inductive magnetic sensor pre-amplification module based on a differential transimpedance form. The inductive magnetic sensor pre-amplification module comprises a twisted-pair shielded wire and a pre-amplification circuit, the preamplifier comprises a differential transimpedance amplification circuit and a differential-to-single-ended circuit; the twisted-pair shielded wire transmits signals to the differential transimpedance amplification circuit through elements such as a resistor and a capacitor. Two output terminals of the twisted-pair shielded wire are connected to inverted input ends of two operational amplifiers of the differential transimpedance amplification circuit respectively, and in-phase input ends of the operational amplifiers are grounded. A feedback network is matched between the inverted input end and the output end of the operational amplifier; the feedback network is formed by connecting a feedback resistor and a feedback capacitor in parallel; the differential-to-single-ended circuit converts the differential signal into a single-ended signal through an operational amplifier and a plurality of resistors and outputs the single-ended signal from an output end. The method has the advantages that the detection sensitivity of weak signals is improved; the interference of external common-mode noise is reduced, and the signal-to-noise ratio is improved; and the stability and the reliability of the circuit are improved.

Description

Technical Field

[0001] The present application belongs to the field of magnetic field detection, and specifically relates to an inductive magnetic sensor preamplifier module based on a differential transimpedance form. Background Art

[0002] Detecting magnetic fields in space has long been a primary method for conducting space science research. The inductive magnetometer (SCM), also known as a search coil magnetometer, is the optimal method for measuring AC magnetic fields. It is a magnetic field sensor that measures AC magnetic fields based on Faraday's law of electromagnetic induction. This sensor consists of a probe and a signal processing circuit. The probe measures magnetic field fluctuations in space, while the magnetic field signal processing circuit converts the AC differential voltage signal sensed by the inductive magnetic sensor into a voltage signal reflecting the strength of the AC magnetic field. This sensor is widely used in space science and geophysical research.

[0003] In space applications, signal processing circuits and inductive magnetic sensor probes are typically deployed separately due to the harsh space environment and electromagnetic interference from satellite platforms and other electronic equipment. In planetary exploration, the distance between the two may be even greater if deployment on a planetary surface is required.

[0004] In space exploration and planetary missions, long-distance transmission may be required depending on the mission characteristics. However, weak signals are easily interfered with by the external environment during long cable transmission, resulting in errors in the detection results. Summary of the Invention

[0005] The purpose of the present application is to overcome the defect that the detection signal of the inductive magnetic sensor is easily interfered with in the case of long cables.

[0006] In order to achieve the above-mentioned purpose, the present application proposes an inductive magnetic sensor preamplifier module based on a differential transimpedance form, comprising a twisted shielded pair and a preamplifier circuit; wherein,

[0007] The input ends of the two signal transmission lines of the twisted shielded pair are respectively connected to an output end of the induction coil; the two signal transmission lines of the twisted shielded pair have a resistor with a resistance of R0, and one signal transmission line is connected to the output end of the induction coil through a capacitor C 11 Connect the shield layer, and the other signal transmission line passes through the capacitor C 22 Connect the shield layer; capacitor C is passed between the two signal transmission lines 12 connect;

[0008] The preamplifier circuit includes a differential transimpedance amplifier circuit and a differential to single-ended circuit; wherein,

[0009] The differential transimpedance amplifier circuit includes two first operational amplifiers; the inverting input terminals of the two first operational amplifiers are respectively connected to the output terminals of the signal transmission line; the non-inverting input terminals of the two first operational amplifiers are grounded; a feedback network is connected between the inverting input terminals and the output terminals of the two first operational amplifiers; the feedback network consists of a feedback resistor R f and a feedback capacitor C f Parallel structure;

[0010] The differential to single-ended circuit includes a second operational amplifier; the inverting input terminal and the non-inverting input terminal of the second operational amplifier are connected to the resistor R 11 The resistor is connected to the output terminals of the two first operational amplifiers; the inverting input terminal and the output terminal of the second operational amplifier are connected via a resistor R 11 The non-inverting input of the second operational amplifier is connected to the resistor R 11 resistor to ground.

[0011] As an improvement to the above module, the transfer function T(jw) between the output voltage and magnetic flux density of the differential transimpedance amplifier circuit is expressed as:

[0012]

[0013] Among them, R f is the feedback resistor; C f is the feedback capacitor; R is the resistance of the induction coil; w is the frequency; N is the number of turns of the induction coil; S is the cross-sectional area of ​​the induction coil core; μ app is the apparent magnetic permeability; L is the inductance of the induction coil; j is the imaginary unit.

[0014] As an improvement to the above module, the noise power spectrum density of the differential transimpedance amplifier circuit is:

[0015]

[0016] Among them, e pA 2 is the operational amplifier input voltage noise; i pA 2 is the operational amplifier input current noise; R0 is the resistance per unit length of the cable; K is the Boltzmann constant, T is the temperature; C 11 and C 22 are the capacitances between the two signal transmission lines and the shielding layer of the twisted pair shielded cable; C 12 is the capacitance between the two signal transmission lines of the twisted shielded pair cable; C is the capacitance of the induction coil; ω=2πf is the angular frequency, and f is the frequency.

[0017] Compared with the prior art, the advantages of this application are:

[0018] 1. Compared with the prior art, the circuit module of this application improves the detection sensitivity of weak signals;

[0019] 2. Reduce the interference of external common mode noise and improve the signal-to-noise ratio;

[0020] 3. Improved circuit stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure shows a preamplifier circuit diagram of an inductive magnetic sensor based on a differential transimpedance form;

[0022] Figure 2 Shown is the circuit signal transmission flow chart and a schematic diagram of the noise introduction path. DETAILED DESCRIPTION

[0023] The technical solution of this application is described in detail below with reference to the accompanying drawings.

[0024] This application proposes a preamplifier circuit module for an inductive magnetic sensor based on a differential transimpedance structure. The module primarily comprises a symmetrical operational amplifier, feedback resistors, and feedback capacitors. A cable impedance model is also introduced to account for its impact on the performance of the inductive magnetic sensor. This circuit leverages the high anti-interference performance of the differential structure, significantly improving the system's anti-interference capabilities. The circuit's sensitivity is doubled compared to conventional technologies, effectively enhancing the accuracy and reliability of signal detection.

[0025] In space applications, signal transmission between the induction coil and the electronic chassis is mainly achieved through a shielded cable. The induction coil is mainly composed of the DC resistance of the wire, the inductance of the wire and the capacitance between the wire layers, which can be equivalent to an RLC model in which the resistance and inductance are connected in series and the capacitance is connected in parallel; the cable can also be equivalent to a distributed RLC model, but the present invention simplifies its equivalent model, only retaining the wire resistance of the cable, the capacitance between the wires, and the capacitance between the wires and the shielding layer; the preamplifier circuit is composed of a differential transimpedance amplifier circuit and a differential to single-ended circuit. The above-mentioned equivalent models together constitute the "induction coil-cable-differential transimpedance circuit" model. The induction coil is mainly used to sense the magnetic field fluctuation signal in space. The cable uses a twisted pair shielded wire mainly for long-distance transmission of the weak signal sensed by the former. The preamplifier circuit is mainly used to convert the AC differential signal sensed by the coil into a voltage signal that can reflect the strength of the AC magnetic field for subsequent acquisition and processing.

[0026] The induction coil converts the magnetic field fluctuation signal into a differential voltage signal. Its output current can be calculated from its own characteristics. It is connected to the cable part. The cable passes through R0 and C 11、C 12 The signal is transmitted to the differential transimpedance circuit by components such as CMOS and CMOS. The two output terminals are connected to the inverting input terminals of the two operational amplifiers respectively, and the non-inverting input terminal of the operational amplifier is grounded. A feedback network is provided between the inverting input terminal and the output terminal of the operational amplifier. The feedback network consists of a feedback resistor R f and feedback capacitor C f The parallel connection forms a negative feedback loop to stabilize the gain of the operational amplifier and achieve phase compensation. Finally, the differential to single-ended circuit is connected through the operational amplifier and R 11 The resistors convert the differential signal into a single-ended signal, which is then output from the Vout port. The resistors and capacitors must be dynamically adjusted based on actual needs. Because the transmitted AC signal is very weak, the operational amplifier must have low-noise performance, such as the OP27, OP270, and ADA4625.

[0027] The transfer function (sensitivity) between the output voltage of the differential transimpedance structure and the magnetic flux density can be expressed as:

[0028]

[0029] Among them, R f is the feedback resistor, C f is the feedback capacitor, R is the resistance of the induction coil, w is the frequency, N is the number of turns of the induction coil, S is the cross-sectional area of ​​the induction coil core, μ app is the apparent magnetic permeability, L is the inductance of the induction coil, and j is the imaginary unit. The effect of the cable on the performance of the inductive magnetic sensor is ignored here.

[0030] The noise power spectral density can be expressed as:

[0031]

[0032] Among them, e pA 2 is the operational amplifier input voltage noise, i pA 2 is the operational amplifier input current noise. R is the induction coil resistance, L is the induction coil inductance, C is the induction coil capacitance, R0 is the resistance per unit length of the cable, C 11 and C 22 is the capacitance between the cable and the shield, C 12 is the capacitance between the cables, R f and C f are the feedback resistor and feedback capacitor, w is the frequency, K is the Boltzmann constant, T is the temperature, ω=2πf is the angular frequency, and f is the frequency.

[0033] The specific value of this noise depends on the choice of op amp and circuit design.

[0034] Compared with traditional preamplifier circuits, the cable technology provided by this application has twice the sensitivity and greatly reduced the noise level.

[0035] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of this application and are not intended to limit the scope of the present invention. Although this application has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of this application do not depart from the spirit and scope of the technical solutions of this application and should be encompassed by the claims of this application.

Claims

1. An inductive magnetic sensor preamplifier module based on differential transimpedance form, characterized in that: It includes twisted shielded pair cables and preamplifier circuit; wherein, The input ends of the two signal transmission lines of the twisted shielded pair are respectively connected to an output end of the induction coil; the two signal transmission lines of the twisted shielded pair have a resistor with a resistance of R0, and one signal transmission line is connected to the output end of the induction coil through a capacitor C 11 Connect the shield layer, and the other signal transmission line passes through the capacitor C 22 Connect the shield layer; capacitor C is passed between the two signal transmission lines 12 connect; The preamplifier circuit includes a differential transimpedance amplifier circuit and a differential to single-ended circuit; wherein, The differential transimpedance amplifier circuit includes two first operational amplifiers; the inverting input terminals of the two first operational amplifiers are respectively connected to the output terminals of the signal transmission line; the non-inverting input terminals of the two first operational amplifiers are grounded; a feedback network is connected between the inverting input terminals and the output terminals of the two first operational amplifiers; the feedback network consists of a feedback resistor R f and a feedback capacitor C f Parallel structure; The differential to single-ended circuit includes a second operational amplifier; the inverting input terminal and the non-inverting input terminal of the second operational amplifier are connected to the resistor R 11 The resistor is connected to the output terminals of the two first operational amplifiers; the inverting input terminal and the output terminal of the second operational amplifier are connected via a resistor R 11 The non-inverting input of the second operational amplifier is connected to the resistor R 11 resistor to ground.

2. The inductive magnetic sensor preamplifier module based on differential transimpedance according to claim 1, characterized in that: The transfer function T(jw) between the output voltage and magnetic flux density of the differential transimpedance amplifier circuit is expressed as: Among them, R f is the feedback resistor; C f is the feedback capacitor; R is the resistance of the induction coil; w is the frequency; N is the number of turns of the induction coil; S is the cross-sectional area of ​​the induction coil core; μ app is the apparent magnetic permeability; L is the inductance of the induction coil; j is the imaginary unit.

3. The inductive magnetic sensor preamplifier module based on differential transimpedance according to claim 2, characterized in that: The noise power spectral density of the differential transimpedance amplifier circuit is: Among them, e pA 2 is the operational amplifier input voltage noise; i pA 2 is the operational amplifier input current noise; R0 is the resistance per unit length of the twisted shielded pair; K is the Boltzmann constant, T is the temperature; C 11 and C 22 are the capacitances between the two signal transmission lines and the shielding layer of the twisted pair shielded cable; C 12 is the capacitance between the two signal transmission lines of the twisted shielded pair cable; C is the capacitance of the induction coil; ω=2πf is the angular frequency, and f is the frequency.

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