CN117192226A - Weak electromagnetic wave signal detection system - Google Patents
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Abstract
The invention discloses a weak electromagnetic wave signal detection system, which comprises an ultralow noise pre-amplification module, a high-pass filtering module, a high-multiple instrument amplification module and a low-pass filtering module which are connected in sequence, wherein the ultralow noise pre-amplification module is used for amplifying weak electric signals output by an antenna in a low-multiple way to obtain a first output signal; the high-pass filtering module is used for filtering out-of-band low-frequency interference signals in the first output signals to obtain second output signals; the high-multiple instrument amplification module is constructed based on the integrated instrument amplifier, and performs high-precision, high-stability and high-multiple amplification on the second output signal by adopting a pseudo-differential input and in-phase amplification mode, and obtains a third output signal; the low-pass filtering module is used for filtering out-of-band high-frequency interference signals in the third output signals so as to realize weak electromagnetic wave signal detection. The invention can effectively improve the gain and the sensitivity of the weak ultra-low frequency and ultra-low frequency electromagnetic wave signal detection system.
Description
Technical Field
The invention relates to the technical field of weak electromagnetic wave signal detection, in particular to a weak electromagnetic wave signal detection system.
Background
Very low frequency (Extremely Low Frequency, ELF) and ultra low frequency (Super Low Frequency, SLF) waves refer to electromagnetic waves in the frequency ranges of 3-30 Hz and 30-300 Hz, respectively, and the main sources of the electromagnetic waves comprise natural phenomenon radiation such as lightning and artificial station radiation. The ELF/SLF wave has the characteristics of small propagation loss, long propagation distance in the earth-ionosphere waveguide, high skin depth and the like, and has very important scientific and application significance in the aspects of submarine communication, navigation, geological exploration, space weather monitoring and the like. In fact, whether natural radiation or artificial station radiation, the radiation source is generally far away from the receiving station, the target ELF/SLF signal reaches the receiver very weak after long-distance transmission, and there are often high atmospheric noise and electromagnetic interference in the frequency band, so how to accurately detect and receive such weak target signal becomes a problem to be solved.
When the detection system works, the sensitivity of the system at each frequency point determines the minimum intensity of signals which can be received by the system, and the reliability of weak signal detection can be ensured only if the sensitivity of the system is high enough. The conventional detection circuit constructed based on the operational amplifier has the problem of low sensitivity in an ELF/SLF frequency band, and can not effectively detect a weak target signal, so that a system for improving the detection sensitivity of the weak electromagnetic wave signal is needed.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, an object of the present invention is to provide a weak electromagnetic wave signal detection system capable of effectively improving the gain and sensitivity of a weak very low frequency and ultra low frequency electromagnetic wave signal detection system.
In order to achieve the above purpose, the invention is realized by the following technical scheme:
a weak electromagnetic wave signal detection system, comprising:
the ultra-low noise pre-amplification module is used for receiving the weak electric signal output by the antenna, and carrying out low-multiple amplification on the weak electric signal to obtain a first output signal, wherein the weak electric signal is an electric signal obtained by converting the received weak electromagnetic wave signal by the antenna;
the high-pass filtering module is connected with the ultra-low noise pre-amplification module and is used for filtering out the out-of-band low-frequency interference signals in the first output signals to obtain second output signals;
the high-multiple instrument amplification module is connected with the high-pass filtering module, is constructed based on an integrated instrument amplifier, and adopts a pseudo-differential input and in-phase amplification mode to amplify the second output signal with high precision, high stability and high multiple and obtain a third output signal;
the low-pass filtering module is connected with the high-multiple instrument amplifying module and is used for filtering out-of-band high-frequency interference signals in the third output signals so as to realize weak electromagnetic wave signal detection.
Preferably, the ultra-low noise pre-amplification module comprises a JFET differential amplification unit and a single operational amplification unit, and the ultra-low noise pre-amplification module performs two-stage low-multiple amplification on the weak electric signal through the JFET differential amplification unit and the single operational amplification unit.
Preferably, the JFET differential amplifying unit has two input ends, the JFET differential amplifying unit includes a first field effect tube, a second field effect tube, a first resistor to a sixth resistor, and a first capacitor to a third capacitor, the first ends of the first resistor are connected to a power supply, the first ends of the second resistor and the third resistor are connected to the second ends of the first resistor, the second ends of the second resistor and the third resistor are connected to the drains of the first field effect tube and the second field effect tube, the gates of the first field effect tube are connected to the first input end and the second input end of the differential amplifying unit through the first capacitor and the fourth resistor, the sources of the first field effect tube and the second field effect tube are connected to the second end of the JFET differential amplifying unit through the fifth resistor and the second capacitor, the gates of the second field effect tube are connected to the first end of the differential amplifying unit through the third capacitor and the sixth resistor, the gates of the first field effect tube are connected to the first end of the differential amplifying unit, and the second end of the differential amplifying unit is connected to the ground.
Preferably, the single operational amplifier unit includes a first operational amplifier, a seventh resistor, a ninth resistor, and a fourth capacitor, where a first end of the fourth capacitor is connected to an output end of the JFET differential amplifier unit, a second end of the fourth capacitor is grounded through the seventh resistor, a second end of the fourth capacitor is further connected to an inverting input end of the first operational amplifier through an eighth resistor, an inverting input end of the first operational amplifier is further connected to an output end of the first operational amplifier through the ninth resistor, and a non-inverting input end of the first operational amplifier is grounded.
Preferably, the high-pass filtering module includes a second operational amplifier to a fourth operational amplifier, a tenth resistor to a fourteenth resistor, and a fifth capacitor to a ninth capacitor, wherein a first end of the fifth capacitor is connected to an output end of the ultra-low noise pre-amplifying module, a second end of the fifth capacitor is connected to a non-inverting input end of the second operational amplifier through a sixth capacitor, a second end of the fifth capacitor is also connected to an inverting input end and an output end of the second operational amplifier through a tenth resistor, and a non-inverting input end of the second operational amplifier is also grounded through an eleventh resistor; the output end of the second operational amplifier is connected with the first end of a seventh capacitor, the second end of the seventh capacitor is connected with the non-inverting input end of a third operational amplifier through an eighth capacitor, the second end of the seventh capacitor is also connected with the inverting input end and the output end of the third operational amplifier through a twelfth resistor, and the non-inverting input end of the third operational amplifier is also grounded through a thirteenth resistor; the output end of the third operational amplifier is connected with the non-inverting input end of the fourth operational amplifier through a ninth capacitor, the inverting input end of the fourth operational amplifier is connected with the output end of the fourth operational amplifier, and the non-inverting input end of the fourth operational amplifier is grounded through a fourteenth resistor.
Preferably, the high-multiple instrument amplification module comprises a fifth operational amplifier and a fifteenth resistor, the non-inverting input end of the fifth operational amplifier is connected with the output end of the high-pass filtering module, the inverting input end of the fifth operational amplifier is grounded, and the fifteenth resistor is connected with the gain resistor external pin of the fifth operational amplifier.
Preferably, the low-pass filtering module includes sixth to eighth operational amplifiers, sixteenth to twentieth resistors, and tenth to fourteenth capacitors, a first end of the sixteenth resistor is connected to the output end of the high-multiple meter amplifying module, a second end of the sixteenth resistor is connected to the non-inverting input end of the sixth operational amplifier through the seventeenth resistor, a second end of the sixteenth resistor is further connected to the inverting input end and the output end of the sixth operational amplifier through the tenth capacitor, and the non-inverting input end of the sixth operational amplifier is further grounded through an eleventh capacitor; the output end of the sixth operational amplifier is connected with the first end of an eighteenth resistor, the second end of the eighteenth resistor is connected with the non-inverting input end of a seventh operational amplifier through a nineteenth resistor, the second end of the eighteenth resistor is also connected with the inverting input end and the output end of the seventh operational amplifier through a twelfth capacitor, and the non-inverting input end of the seventh operational amplifier is also grounded through a thirteenth capacitor; the output end of the seventh operational amplifier is connected with the non-inverting input end of the eighth operational amplifier through a twenty-first resistor, the inverting input end of the eighth operational amplifier is connected with the self output end, and the non-inverting input end of the eighth operational amplifier is grounded through a fourteenth capacitor.
Preferably, the high-pass filtering module and the low-pass filtering module are five-order butterworth filters.
The invention has at least the following technical effects:
the invention carries out two-stage low-multiple amplification on an electric signal converted by a weak electromagnetic wave signal received by an antenna through an ultralow-noise pre-amplification module comprising a JFET (field effect transistor) differential amplification unit and a single operational amplification unit to obtain a first output signal, then carries out-of-band low-frequency interference signal filtering on the first output signal subjected to two-stage low-multiple amplification through a five-stage Butt Wo Sigao pass filter module to obtain a second output signal, carries out high-precision, high-stability and high-multiple amplification on the second output signal through a high-multiple instrument amplification module constructed based on an integrated instrument amplifier to obtain a third output signal, and finally filters out-of-band high-frequency interference signal in the third output signal through the five-stage Butt low-pass filter module to realize weak electromagnetic wave signal detection.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
Fig. 1 is a block diagram of a weak electromagnetic wave signal detection system according to an embodiment of the present invention.
Fig. 2 is a schematic circuit diagram of an ultralow noise pre-amplifying module according to an embodiment of the present invention.
Fig. 3 is a schematic circuit diagram of a high-pass filter module according to an embodiment of the invention.
Fig. 4 is a schematic circuit diagram of a high-multiple instrument amplification module according to an embodiment of the invention.
Fig. 5 is a schematic circuit diagram of a low-pass filter module according to an embodiment of the invention.
Fig. 6 is a schematic diagram of a sensitivity curve of a weak electromagnetic wave signal detection system according to an embodiment of the invention.
Detailed Description
The present embodiment is described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
A weak electromagnetic wave signal detection system of the present embodiment is described below with reference to the drawings.
Fig. 1 is a block diagram of a weak electromagnetic wave signal detection system according to an embodiment of the present invention. As shown in fig. 1, the weak electromagnetic wave signal detection system comprises an ultralow noise pre-amplification module, a high pass filtering module, a high multiple instrument amplification module and a low pass filtering module which are sequentially connected, wherein the ultralow noise pre-amplification module is used for receiving a weak electric signal output by an antenna and amplifying the weak electric signal in a low multiple way to obtain a first output signal, and the weak electric signal is an electric signal obtained by converting the received weak electromagnetic wave signal by the antenna; the high-pass filtering module is used for filtering out-of-band low-frequency interference signals in the first output signals to obtain second output signals; the high-multiple instrument amplification module is constructed based on the integrated instrument amplifier, and performs high-precision, high-stability and high-multiple amplification on the second output signal by adopting a pseudo-differential input and in-phase amplification mode, and obtains a third output signal; the low-pass filtering module is used for filtering out-of-band high-frequency interference signals in the third output signals so as to realize detection of extremely low frequency and extremely low frequency weak electromagnetic wave signals.
The ultra-low noise pre-amplification module comprises a JFET differential amplification unit and a single operational amplification unit, and the ultra-low noise pre-amplification module can amplify weak electric signals in two stages by the JFET differential amplification unit and the single operational amplification unit.
Specifically, the JFET differential amplification unit performs primary low-noise, high-sensitivity receiving and low-multiple amplification on the ELF/SLF weak electric signal output from the antenna; the single operational amplification unit performs second-level low noise and low multiple amplification on the electric signal from the first-level low multiple amplification output.
In this embodiment, the ultra-low noise pre-amplification module is connected to a pair of orthogonal magnetic loop antennas, where the orthogonal magnetic loop antennas are used to receive electromagnetic waves in the ELF/SLF frequency band and convert the electromagnetic waves into electrical signals, and the ultra-low noise pre-amplification module receives the electrical signals transmitted by the antennas and performs two-stage low-multiple amplification through the JFET differential amplification unit and the single operational amplification unit. And then, a high-pass filter module with a five-order Butterworth filter structure is adopted to filter out-of-band low-frequency interference signals with serious interference in the signals after small-multiple amplification, and then high-precision, high-stability and high-multiple amplification are carried out through a high-multiple instrument amplification module. Finally, a low-pass filter module with a five-order Butterworth filter structure is adopted to filter out-of-band high-frequency interference signals in the signals amplified by high multiples, so that the sensitivity and the signal quality of the system in an ELF/SLF frequency band can be remarkably improved, and weak electromagnetic wave signal detection is realized.
Fig. 2 is a schematic circuit diagram of an ultralow noise pre-amplifying module according to an embodiment of the present invention. As shown in FIG. 2, the JFET differential amplification unit in the ultra-low noise pre-amplification module has two input ends and comprises a first JFET1, a second JFET2, and first to sixth resistors R D 、R DL 、R DR 、R GL 、R S And R is GR And first to third capacitors C GL 、C S And C GR First resistor R D Is connected with the power supply V CC Connected with a second resistor R DL And a third resistor R DR Is connected with the first end of the first resistor R D A second resistor R connected to the second end of DL And R of a third resistance DR The second end is respectively connected with the drains of the first field effect tube JFET1 and the second field effect tube JFET2, and the grid electrode of the first field effect tube JFET1 is respectively connected with the drain electrode of the second field effect tube JFET2 through a first capacitor C GL And a fourth resistor R GL The first input end and the second input end of the JFET differential amplifying unit are connected, and the sources of the first field effect tube JFET1 and the second field effect tube JFET2 are respectively connected through a fifth resistor R S And a second capacitor C S Connected to the second end of the JFET differential amplifying unitThe grid electrode of the second field effect tube JFET2 passes through a third capacitor C GR And a sixth resistor R GR A second end of the JFET differential amplification unit is connected with the antenna output end, and a second end of the JFET differential amplification unit is grounded and is provided with a first resistor R D The second end of the (D) is the output end of the JFET differential amplifying unit.
With continued reference to fig. 2, the single operational amplifier unit in the ultra-low noise pre-amplification module includes a first operational amplifier U 1 Seventh to ninth resistors, R 1 、R 2 、R 3 And a fourth capacitor C 1 Fourth capacitor C 1 A fourth capacitor C connected with the output end of the JFET differential amplifying unit 1 Through a seventh resistor R 1 Grounded, fourth capacitor C 1 And also pass through an eighth resistor R 2 And a first operational amplifier U 1 Is connected with the inverting input terminal of the first operational amplifier U 1 The inverting input terminal of (2) also passes through a ninth resistor R 3 With self-output end, namely Out 1 Connected to a first operational amplifier U 1 Is grounded.
Specifically, an ultra-low noise pre-amplification module may be designed according to fig. 2. Wherein, the JFET differential amplifying unit part is designed, JFET1 and JFET2 can be selected from IF3602 field effect transistors with ultra-low noise and high gain, and are connected into a common source amplifying circuit structure, wherein, a first capacitor C GL And a fourth resistor R GL Third capacitor C GR And a sixth resistor R GR The resistor can filter unnecessary direct current signals in the circuit, and can also play a role of pull-down, so that the voltage of the grid electrode is kept at the ground level, and the first field effect tube JFET1 and the second field effect tube JFET2 can work in a constant current area. Wherein the fifth resistor R S And a second capacitor C S Is connected with the source stages of the first field effect tube JFET1 and the second field effect tube JFET2, so that the voltage difference between the gate voltage and the source voltage is always less than 0, namely U GS <And 0, thereby eliminating abnormal fluctuation in the circuit to prevent the circuit from not working normally when fluctuation occurs.Wherein the second resistor R DL And a third resistor R DR One end of the first and second field effect tube JFET1 and 2 are connected with the drain electrodes of the first and second field effect tube JFET1 and 2 respectively, which mainly plays a role in balancing and ensures the complete symmetry of the differential structure. Wherein the first resistor R D One end of (2) is connected with a power supply V CC The other end is connected with a second resistor R DL And a third resistor R DR Is connected to one end of a first resistor R D Mainly plays a role of voltage division through drain-source voltage U DS And source voltage U S The value of the resistor is calculated and set to ensure the operating voltage requirements of the first and second field effect transistor JFETs 1 and 2.
Design single operational amplifier unit part, first operational amplifier U 1 Optionally, a low noise op-amp LT1128, a seventh resistor R 1 And a fourth capacitor C 1 A filter circuit is formed to filter unnecessary DC components, wherein the fourth capacitor C 1 And the output end of the JFET differential amplifying unit is connected. Eighth resistor R 2 One end is connected with a fourth capacitor C 1 The other end is connected with a first operational amplifier U 1 Is connected to the inverting input terminal of the ninth resistor R 3 One end and a first operational amplifier U 1 Is connected to the inverting input terminal of the first operational amplifier U 1 Is connected with the output end of the capacitor by setting an eighth resistor R 2 And a ninth resistor R 3 The value of (2) may determine the gain of the circuit, wherein an eighth resistor R is determined 2 After the value of (2), the actual gain A of the circuit can be calculated by the following formula v ：
In this embodiment, the JFET differential amplification unit is a primary amplification circuit based on an ultra-low noise JFET, specifically, ultra-low noise field effect transistors JFET1 and JFET2, and resistor R D 、R DL 、R DR 、R GL 、R GR And R is S Capacitance C S 、C GL And C GR High-sensitivity differential amplifying circuit for converting and outputting ELF/SLF frequency band to magnetic ring antennaThe weak electric signals in the circuit are received and amplified by one-stage low-multiple amplification. It is noted that the noise level and sensitivity of the primary amplifying circuit largely determine the noise performance of the entire detection system, so that controlling the noise level of the primary amplifying circuit is important to improve the sensitivity of the system. In this embodiment, the JFET differential amplifying unit structure can effectively reduce the noise coefficient of the system and improve the detection sensitivity of the system.
In this embodiment, the single operational amplifier unit is a two-stage amplifying circuit based on a low noise operational amplifier, which is composed of a first operational amplifier U 1 Resistance R 1 、R 2 And R is 3 Capacitance C 1 The structure is that the signal amplified by the primary amplifying circuit is amplified by a secondary low-multiple, wherein R 1 And C 1 Forms a filter circuit, mainly filters DC component in the output signal of the primary amplifying circuit, R 2 And R is 3 The amplification factor of the secondary amplification circuit is determined, and the amplification circuit has the main function of amplifying the output signal of the primary amplification circuit by a further small multiple so as to ensure that the subsequent filtering processing is normally performed without losing useful signals.
Fig. 3 is a schematic circuit diagram of a high-pass filter module according to an embodiment of the invention. As shown in fig. 3, the high-pass filter module includes second to fourth operational amplifiers, i.e., U 2 、U 3 And U 4 Tenth to fourteenth resistors, i.e. R 4 -R 8 And fifth to ninth capacitances, i.e. C in the figure 4 -C 8 Fifth capacitor C 4 A fifth capacitor C connected with the output end of the ultra-low noise pre-amplification module at the first end (In 2 end) 4 Through a sixth capacitor C 5 And a second operational amplifier U 2 A fifth capacitor C connected to the non-inverting input terminal 4 And also through a tenth resistor R 4 And a second operational amplifier U 2 Is connected with the output end, and a second operational amplifier U 2 The non-inverting input terminal of (2) also passes through an eleventh resistor R 5 Grounding; second operational amplifier U 2 Output terminal of (C) and seventh capacitor C 6 Is connected with the first end of the seventhCapacitor C 6 Through an eighth capacitor C 7 And a third operational amplifier U 3 Is connected with the non-inverting input terminal of the seventh capacitor C 6 And also pass through a twelfth resistor R 6 And a third operational amplifier U 3 An inverting input terminal and an output terminal of the third operational amplifier U 3 The non-inverting input terminal of (2) also passes through a thirteenth resistor R 7 Grounding; third operational amplifier U 3 Through a ninth capacitor C 8 And a fourth operational amplifier U 4 Is connected with the non-inverting input terminal of the fourth operational amplifier U 4 An inverting input terminal of (a) is connected with an output terminal of (a) Out2 terminal, and a fourth operational amplifier U 4 The non-inverting input terminal of (2) also passes through a fourteenth resistor R 8 And (5) grounding.
Specifically, the second to fourth operational amplifiers, i.e., U 2 -U 4 The operational amplifier AD8620 with ultra-low current noise can be selected and built into a Salley-Key (a filter topological structure) filtering framework. First, a second-order filtering node and a capacitor C can be built 4 One end of the capacitor C is connected with the output end of the ultra-low noise pre-amplification module 4 And C at the other end of (2) 5 Series-connected and second operational amplifier U 2 Is connected to the non-inverting input terminal of resistor R 4 One end and a capacitor C 4 And C 5 The other end is connected with a second operational amplifier U 2 Is connected to the output terminal, resistor R 5 One end and a capacitor C 5 And a second operational amplifier U 2 The same phase input end of the power supply is connected with the ground, and the other end of the power supply is connected with the ground. Similarly, a third operational amplifier U 3 And a second operational amplifier U 2 The connection method is the same, so that the construction and connection of two second-order filtering nodes can be completed. The last filtering section has only one order, the capacitor C 8 One end of the filter is connected with the output end of the previous filter node, and the other end is connected with a resistor R 8 And a fourth operational amplifier U 4 Is connected to the non-inverting input terminal of the fourth operational amplifier U 4 The inverting input of which is connected to the output.
In this embodiment, the high-pass filter module adopts a five-order Butterworth Salley-key structure, so that the number of components can be further reducedThe number of parts used reduces the noise level of the module. The high-pass filter module in this embodiment passes through three low-current noise operational amplifiers U 2 -U 4 And tenth to fourteenth resistors, R 4 -R 8 And fifth to ninth capacitances, C 4 -C 8 The low-frequency noise in the pre-amplified output signal can be filtered, the cut-off frequency of the output signal is 300Hz, the signal attenuation is 99.8dB/dec, and meanwhile, the signal fluctuation is not more than 1dB as flat as possible in the passband.
Fig. 4 is a schematic circuit diagram of a high-multiple instrument amplification module according to an embodiment of the invention. As shown in fig. 4, the high-multiple meter amplification module includes a fifth operational amplifier U 5 And a fifteenth resistor R G Fifth operational amplifier U 5 The non-inverting input end of (a) In3 end is connected with the output end of the high-pass filter module, and a fifth operational amplifier U 5 The inverting input terminal of (B) is grounded, the fifteenth resistor R G And a fifth operational amplifier U 5 The gain resistor external pins of the gain resistor are connected with the 2 nd pin and the 3 rd pin.
Specifically, the fifth operational amplifier U 5 The instrument amplifier AD8429 with high precision, high stability and low noise performance can be selected, and in the embodiment, the fifth operational amplifier U can be used 5 Is constructed into a pseudo-differential structure, i.e. the non-inverting input terminal is connected with the output of the high-pass filter module, the inverting input terminal is grounded, and the fifteenth resistor R is connected with the output of the high-pass filter module G And a fifth operational amplifier U 5 Is connected to pins 2 and 3 of (a) and then by varying the fifteenth resistor R G The required magnification can be obtained by the following formula G Value:
wherein G is the amplification factor, i.e., gain.
In this embodiment, the high-multiple instrument amplification module is built based on an integrated instrument amplifier with high precision and high stability, because it has smaller volume, lower noise level, and better symmetry and common mode rejection ratio than a mode of building with three single operational amplifiers. The high-multiple instrument amplification module adopts a pseudo-differential input and in-phase amplification mode, can better match a single-ended output signal mode of the high-pass filtering module, can provide larger amplification factor for signals on the basis of reducing circuit noise and unnecessary fluctuation, and amplifies the signals after high-pass filtering to a certain degree so as to meet the subsequent processing requirements, wherein the transfer function of the high-multiple instrument amplification module is as follows:
V out ＝G×(V IN+ -V IN- )+V REF (3)
wherein V is out The output value of the high-multiple instrument amplifying module is V IN+ And V IN- Differential input value of high multiple instrument amplifying module, V REF Is the reference voltage value. Wherein the gain G setting mainly depends on the gain resistance, namely the fifteenth resistance R G So long as R is changed according to gain requirements G The value of (3) can be used to achieve the object conveniently. Notably, the gain resistance R is changed G Meanwhile, the change of the bandwidth is considered, and the expected target can be obtained only on the basis of ensuring that the gain and the bandwidth meet the requirements.
Fig. 5 is a schematic circuit diagram of a low-pass filter module according to an embodiment of the invention. As shown in fig. 5, the low-pass filter module includes sixth to eighth operational amplifiers U 6 -U 8 Sixteenth to twentieth resistors, i.e. R 9 -R 13 And tenth to fourteenth capacitors C 9 -C 13 Sixteenth resistor R 9 A first end of the resistor R is connected with the output end of the high-multiple instrument amplification module 9 Through a seventeenth resistor R 10 And a sixth operational amplifier U 6 Is connected with the non-inverting input terminal of the sixteenth resistor R 9 And also pass through a tenth capacitor C 9 And a sixth operational amplifier U 6 Is connected with the output end, and a sixth operational amplifier U 6 The non-inverting input terminal of (2) is also connected with the eleventh capacitor C 10 Grounding; sixth operational amplifier U 6 Output terminal of (2)Eighteenth resistor R 11 Is connected with the first end of the eighteenth resistor R 11 Through a nineteenth resistor R 12 And seventh operational amplifier U 7 Is connected with the non-inverting input terminal of the eighteenth resistor R 11 And also pass through a twelfth capacitor C 11 And seventh operational amplifier U 7 Is connected with the output end, and a seventh operational amplifier U 7 The non-inverting input terminal of (2) also passes through thirteenth capacitor C 12 Grounding; seventh operational amplifier U 7 Through the twentieth resistor R 13 And eighth operational amplifier U 8 Is connected with the non-inverting input terminal of the eighth operational amplifier U 8 An eighth operational amplifier U with its inverting input connected to its own output, namely, the Out4 end 8 The non-inverting input terminal of (C) is also connected with the fourteenth capacitor C 13 And (5) grounding.
Specifically, the sixth to eighth operational amplifiers U 6 -U 8 An ultra-low current noise operational amplifier AD8620 can be selected. Firstly, a second-order filter node of a Salley-Key filter framework and a resistor R can be built 9 One end of the resistor R, namely the In4 end, is connected with the output end of the high-multiple instrument amplification module 9 And R is at the other end of 10 Series-connected and sixth operational amplifier U 6 Is connected to the non-inverting input terminal of capacitor C 9 One end and resistor R 9 And R is 10 The other end is connected with a sixth operational amplifier U 6 Is connected to the output terminal, capacitor C 10 One end and resistor R 10 And a sixth operational amplifier U 6 The same phase input end of the power supply is connected with the ground, and the other end of the power supply is connected with the ground. Similarly, a seventh operational amplifier U 7 Connection method of (c) and sixth operational amplifier U 6 The same can be achieved by constructing and connecting two second-order filter nodes. The last filtering section has only one order, the resistor R 13 One end of the capacitor C is connected with the output end of the previous filtering node 13 And an eighth operational amplifier U 8 Is connected to the non-inverting input terminal of the eighth operational amplifier U 8 Is connected to the output terminal.
In this embodiment, the low-pass filter module also adopts five-order ButterworthThe Salley-key structure, which is formed by U 6 ～U 8 Three low current noise op-amp, R 9 ～R 13 Five resistors and C 9 ～C 13 The five capacitors can filter high-frequency noise in the output signal of the high-multiple instrument amplification module, the cut-off frequency of the output signal is 100kHz, the signal attenuation is 99.3dB/dec, and meanwhile, the signal fluctuation in a pass frequency band is not more than 1dB.
In this embodiment, the resistor and the capacitor each use a device having a low temperature drift characteristic, wherein the accuracy of the resistor device is 1% and the accuracy of the capacitor device is 10%.
The sensitivity of the high-sensitivity weak electromagnetic wave signal detection system constructed by the example based on the ultra-low noise JFET in the ELF/SLF frequency band is analyzed below. Fig. 6 is a schematic diagram of a sensitivity curve of a weak electromagnetic wave signal detection system according to an embodiment of the invention. As shown in FIG. 6, the abscissa is frequency, the ordinate is sensitivity, the dotted line represents the system sensitivity under the existing equipment architecture, the solid line represents the sensitivity of the detection system constructed by this example, and by contrast analysis, it can be found that the sensitivity in the frequency band of 3-300 Hz is significantly higher than that of the existing equipment, and the sensitivity at the frequency point of 3Hz is 0.57 respectivelyAnd 1.15->The sensitivity at 300Hz frequency point is 5.81->And 11.52The sensitivity improvement ratio on the two frequency points can reach 50.43% and 49.57%, respectively, and the sensitivity improvement ratio in the whole frequency band of 3-300 Hz is about 50%. In addition, compared with some current main-stream on-board devices such as DEMETER, MMO, van Allen Probes, ERG and the like, the sensitivity at the frequency point of 10Hz is all at-3 ∈ ->In this example, the sensitivity of the detection circuit is-0.17 +.>Therefore, the sensitivity of the high-sensitivity weak electromagnetic wave signal detection system based on the ultra-low noise JFET in the embodiment in the ELF/SLF frequency range is remarkably improved.
In summary, the ultra-low noise pre-amplification module including the JFET differential amplification unit and the single operational amplifier unit is used for performing two-stage low-multiple amplification on the electric signal converted from the weak electromagnetic wave signal received by the antenna to obtain a first output signal, then the five-stage buttery Wo Sigao pass filter module is used for filtering out the out-of-band low-frequency interference signal on the first output signal after the two-stage low-multiple amplification to obtain a second output signal, the high-multiple instrument amplifier module constructed based on the integrated instrument amplifier is used for performing high-precision, high-stability and high-multiple amplification on the second output signal to obtain a third output signal, and finally the five-stage buttery low-pass filter module is used for filtering out-of-band high-frequency interference signal in the third output signal to realize weak electromagnetic wave signal detection.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
While the present invention has been described in detail through the foregoing description of the preferred embodiment, it should be understood that the foregoing description is not to be considered as limiting the invention. Many modifications and substitutions of the present invention will become apparent to those of ordinary skill in the art upon reading the foregoing. Accordingly, the scope of the invention should be limited only by the attached claims.
Claims (8)
1. A weak electromagnetic wave signal detection system, comprising:
the ultra-low noise pre-amplification module is used for receiving the weak electric signal output by the antenna, and carrying out low-multiple amplification on the weak electric signal to obtain a first output signal, wherein the weak electric signal is an electric signal obtained by converting the received weak electromagnetic wave signal by the antenna;
the high-pass filtering module is connected with the ultra-low noise pre-amplification module and is used for filtering out the out-of-band low-frequency interference signals in the first output signals to obtain second output signals;
the high-multiple instrument amplification module is connected with the high-pass filtering module, is constructed based on an integrated instrument amplifier, and adopts a pseudo-differential input and in-phase amplification mode to amplify the second output signal with high precision, high stability and high multiple and obtain a third output signal;
the low-pass filtering module is connected with the high-multiple instrument amplifying module and is used for filtering out-of-band high-frequency interference signals in the third output signals so as to realize weak electromagnetic wave signal detection.
2. The weak electromagnetic wave signal detection system of claim 1, wherein the ultra-low noise pre-amplification module comprises a JFET differential amplification unit and a single operational amplification unit, and the ultra-low noise pre-amplification module performs two-stage low-magnification amplification on the weak electric signal through the JFET differential amplification unit and the single operational amplification unit.
3. The weak electromagnetic wave signal detection system of claim 2, wherein the JFET differential amplification unit has two input ends, the JFET differential amplification unit includes a first field effect transistor, a second field effect transistor, a first resistor to a sixth resistor, and a first capacitor to a third capacitor, the first end of the first resistor is connected to a power supply, the first ends of the second resistor and the third resistor are connected to the second end of the first resistor, the second ends of the second resistor and the third resistor are connected to the drains of the first field effect transistor and the second field effect transistor, the gates of the first field effect transistor are connected to the first input end and the second input end of the JFET differential amplification unit through the first capacitor and the fourth resistor, the sources of the first field effect transistor and the second field effect transistor are connected to the second end of the differential amplification unit through the fifth resistor and the second capacitor, the gates of the second field effect transistor are connected to the second end of the differential amplification unit through the third resistor and the third resistor, the gates of the second field effect transistor are connected to the second end of the differential amplification unit, and the output end of the differential amplification unit is connected to the ground.
4. The weak electromagnetic wave signal detection system of claim 3, wherein the single operational amplifier unit comprises a first operational amplifier, a seventh resistor to a ninth resistor, and a fourth capacitor, a first end of the fourth capacitor is connected to the output end of the JFET differential amplifier unit, a second end of the fourth capacitor is grounded through the seventh resistor, a second end of the fourth capacitor is further connected to the inverting input end of the first operational amplifier through an eighth resistor, the inverting input end of the first operational amplifier is further connected to the self output end through the ninth resistor, and the non-inverting input end of the first operational amplifier is grounded.
5. The weak electromagnetic wave signal detection system of claim 1, wherein the high pass filter module comprises a second operational amplifier to a fourth operational amplifier, a tenth resistor to a fourteenth resistor, and a fifth capacitor to a ninth capacitor, a first end of the fifth capacitor is connected to the output end of the ultra-low noise pre-amplification module, a second end of the fifth capacitor is connected to the non-inverting input end of the second operational amplifier through a sixth capacitor, the second end of the fifth capacitor is further connected to the inverting input end and the output end of the second operational amplifier through a tenth resistor, and the non-inverting input end of the second operational amplifier is further grounded through an eleventh resistor; the output end of the second operational amplifier is connected with the first end of a seventh capacitor, the second end of the seventh capacitor is connected with the non-inverting input end of a third operational amplifier through an eighth capacitor, the second end of the seventh capacitor is also connected with the inverting input end and the output end of the third operational amplifier through a twelfth resistor, and the non-inverting input end of the third operational amplifier is also grounded through a thirteenth resistor; the output end of the third operational amplifier is connected with the non-inverting input end of the fourth operational amplifier through a ninth capacitor, the inverting input end of the fourth operational amplifier is connected with the output end of the fourth operational amplifier, and the non-inverting input end of the fourth operational amplifier is grounded through a fourteenth resistor.
6. The weak electromagnetic wave signal detection system of claim 1, wherein the high-multiple instrument amplification module comprises a fifth operational amplifier and a fifteenth resistor, wherein a non-inverting input end of the fifth operational amplifier is connected with an output end of the high-pass filter module, an inverting input end of the fifth operational amplifier is grounded, and the fifteenth resistor is connected with a gain resistor external pin of the fifth operational amplifier.
7. The weak electromagnetic wave signal detection system of claim 1, wherein the low pass filter module comprises a sixth operational amplifier to eighth operational amplifier, a sixteenth resistor to twentieth resistor, and a tenth capacitor to fourteenth capacitor, a first end of the sixteenth resistor is connected to the output terminal of the high-multiple meter amplification module, a second end of the sixteenth resistor is connected to the non-inverting input terminal of the sixth operational amplifier through a seventeenth resistor, the second end of the sixteenth resistor is further connected to the inverting input terminal and the output terminal of the sixth operational amplifier through a tenth capacitor, and the non-inverting input terminal of the sixth operational amplifier is further grounded through an eleventh capacitor; the output end of the sixth operational amplifier is connected with the first end of an eighteenth resistor, the second end of the eighteenth resistor is connected with the non-inverting input end of a seventh operational amplifier through a nineteenth resistor, the second end of the eighteenth resistor is also connected with the inverting input end and the output end of the seventh operational amplifier through a twelfth capacitor, and the non-inverting input end of the seventh operational amplifier is also grounded through a thirteenth capacitor; the output end of the seventh operational amplifier is connected with the non-inverting input end of the eighth operational amplifier through a twenty-first resistor, the inverting input end of the eighth operational amplifier is connected with the self output end, and the non-inverting input end of the eighth operational amplifier is grounded through a fourteenth capacitor.
8. The weak electromagnetic wave signal detection system of any one of claims 1-7, wherein the high pass filter module and the low pass filter module are each fifth order butterworth filters.
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