Weak ocean electric field measuring system with high Q quartz crystal oscillator frequency conversion resonance matching

Abstract

The application provides a weak ocean electric field measurement system with high Q quartz crystal oscillator frequency conversion resonance matching, which realizes high sensitivity and super high signal-to-noise ratio of seawater electric field measurement with small volume / interval. The application uses switch to alternately turn on and off metal mesh and shield cover, improves seawater electric field modulation frequency, realizes high Q resonance matching by parallel connection of multiple quartz crystal oscillators with the same characteristics, obtains passive amplification, greatly improves high-frequency modulation electric field amplitude and signal-to-noise ratio, so that the small volume / interval sensor can also obtain large electric field response. The electric field measurement method has the characteristics of small volume, high sensitivity and high signal-to-noise ratio, and can not only be flexibly arranged in various very weak electric field detection, but also can constitute a phased array electric field sensor to measure long-distance seawater electric field distribution, greatly expanding the field of ocean electric field measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ocean electric field measurement, in particular to a weak ocean electric field measurement system with high Q quartz crystal resonator frequency conversion resonance matching. BACKGROUND

[0002] In the existing ocean electric field measurement method, the natural potential method is mainly used to measure the ultra-low frequency and direct current electric field of the ocean. The principle is to measure the electric field intensity by measuring the potential difference of the seawater at a distance through two sensors at a distance. The farther the distance between the two measuring electrodes, the higher the electric field sensitivity, and the farther the measured electric field distance. However, this measurement is realized by sacrificing the size of the measuring sensor, and usually two sensors are placed underwater by towing, usually 1-2 kilometers apart. When the ship moves, the movement of the towing cable will cause a large positional error, and in order to discover the electric field distribution at a long distance, more sensors are placed, which is also a relatively complex measurement process, and complex inversion is required to analyze the electric field distribution. This not only takes time and has low precision, but also is difficult to meet the real-time, rapid and high-precision measurement.

[0003] In order to reduce the volume, a mechanical modulation, field grinding and other modulation type electric field sensor can be added in front of the traditional electric field measurement electrode to improve the measurement electrode frequency, so as to reduce the size of the low-frequency ocean electric field sensor and improve the measurement sensitivity. Since this type of sensor can suppress drift through mechanical modulation, the mechanical modulation frequency is low, and it will stir up water splashes and cause interference. At the same time, too low frequency is also very difficult to match the electric field transducer. When the volume is small, the measurement sensitivity is also not high. Therefore, it is also difficult to improve the measurement speed and resolution at a small measurement interval through this method. It can be seen that the traditional representative electric field sensing principle and instrument cannot meet the demand of small volume, high sensitivity, rapid and long-distance ocean weak electric field distribution detection.

[0004] Like an antenna that needs to be matched, in order to realize the matching of the small volume electric field sensor, the low frequency / direct current ocean electric field signal must be modulated through the seawater electric field to become a high frequency signal. The higher the modulation frequency, the greater the signal attenuation. Obviously, there is a contradiction between volume reduction and sensitivity improvement. Therefore, a new method of high frequency modulation and high Q matching is needed, which not only greatly increases the modulation frequency, reduces the sensor volume and electrode interval, but also obtains higher response amplitude by introducing high Q multiple quartz crystal resonators in parallel resonance matching.

[0005] This special small volume modulation and high Q quartz crystal resonator matching electric field sensor can be easily formed into a high sensitivity array sensor and instrument to realize the measurement of long-distance and weak vector electric field and distribution electric field in the ocean, which has great significance for ocean resource investigation, oil and gas deposit discovery, marine biology and underwater ship tracking. SUMMARY

[0006] In view of the defects in the prior art, the purpose of the present application is to provide a weak ocean electric field measurement system with high Q-value quartz crystal oscillator frequency conversion resonance matching.

[0007] According to the present application, a weak ocean electric field measurement system with high Q-value quartz crystal oscillator frequency conversion resonance matching is provided, comprising: an ocean electric field modulation circuit 107, a high Q-value resonance matching circuit 111, an electric field signal demodulation circuit 114, an A / D conversion 115, and a computer 116.

[0008] The ocean electric field modulation circuit 107 comprises: a shield 102, a metal mesh 103, a measurement electrode 104, a reference electrode 105, and an electronic switch 106.

[0009] The metal mesh 103, the measurement electrode 104, and the reference electrode 105 are sequentially arranged in parallel in the shield 103, and the metal mesh 103 is close to the opening surface of the shield 102 and parallel to the opening surface of the shield; the metal mesh 103 is connected to the shield 102 through the electronic switch 106; the measurement electrode 104, the reference circuit 105, and the high Q-value resonance matching circuit 111 are connected.

[0010] The high Q-value resonance matching circuit 111, the electric field signal demodulation circuit 114, the A / D conversion 115, and the computer 116 are sequentially connected.

[0011] Preferably, the high Q-value resonance matching circuit 111 comprises: a transformer 109, a quartz crystal oscillator 110, and an output capacitor.

[0012] The measurement electrode 104 is connected to one electrode of the input end of the transformer 109; the reference electrode 105 is connected to the other electrode of the input end of the transformer 109.

[0013] A plurality of quartz crystal oscillators 110 with the same characteristics are connected in parallel or a single quartz crystal oscillator 110 is used, one end of the parallel-connected quartz crystal oscillators 110 or the single quartz crystal oscillator 110 is connected to one electrode of the output end of the transformer 109, and the other end is connected to the output capacitor and the basic amplification circuit 112, respectively; the other electrode of the output end of the transformer 109 and the other end of the output capacitor are grounded.

[0014] Preferably, the high Q-value resonance matching circuit 111 comprises: a transformer 109, an FBAR resonator, and an output capacitor.

[0015] The measurement electrode 104 is connected to one electrode of the input end of the transformer 109; the reference electrode 105 is connected to the other electrode of the input end of the transformer 109.

[0016] A plurality of FBAR resonators are connected in parallel or a single FBAR resonator is used, one end of the FBAR resonator connected in parallel or the single FBAR resonator is connected to one electrode of the output end of the transformer 109, and the other end is connected to an output capacitor and the basic amplification circuit 112, respectively; the other electrode of the output end of the transformer 109 and the other end of the output capacitor are grounded.

[0017] Preferably, the high-Q resonant matching circuit 111 does not contain a transformer, and the gain and narrowband characteristics are achieved by connecting a plurality of quartz crystal oscillators 110 with the same characteristics in parallel or a single quartz crystal oscillator 110.

[0018] Preferably, the computer 116 generates a modulation control to turn on or turn off the electronic switch 106; when the electronic switch 106 is turned on, the metal mesh 103 is short-circuited with the shield cover 102, the opening of the shield cover 102 is filled with the metal mesh 103, and the electric field of seawater is blocked, so that the electric field cannot reach the measurement electrode 104 and the reference electrode 105; when the electronic switch 106 is turned off, the electric field of seawater can reach the measurement electrode 104 and the reference electrode 105 through the opening of the shield cover 102 and the metal mesh 103.

[0019] Preferably, when the electronic switch 106 is turned off and the electric field of seawater can reach the measurement electrode 104 and the reference electrode 105 through the opening of the shield cover 102 and the metal mesh 103, the potential difference between the measurement electrode 104 and the reference electrode 105 is taken as an output signal and transmitted to the high-Q resonant matching circuit 111.

[0020] Preferably, the measurement electrode 104 and the reference electrode 105 use silver chloride electrodes; the shield cover 102 uses a corrosion-resistant conductive material; and the metal mesh 103 uses a titanium alloy material resistant to seawater corrosion.

[0021] Preferably, the electric field signal demodulation circuit 114 includes a basic amplification circuit 112 and a demodulation circuit 113.

[0022] The high-Q resonant matching circuit 111 amplifies the amplitude of the input signal, and then inputs the basic amplification circuit 112 and the demodulation circuit 113 in sequence to obtain a demodulated electric field signal; the A / D conversion 115 converts the demodulated electric field signal into a digital signal; and then inputs the digital signal into the computer 116 for signal processing to obtain a final measurement result.

[0023] Preferably, the basic amplification circuit 112 uses a non-inverting high-speed operational amplifier.

[0024] The demodulation circuit 113 is a switch demodulation circuit, and the switch is controlled by the computer 116 to convert the modulated high-frequency signal into a difference frequency signal with the demodulation control frequency.

[0025] Preferably, the system further comprises: a plurality of the marine electric field modulation circuits 107 combined to form an array sensor, the output of the measuring electrode 104 and the reference electrode 105 is combined into a signal through a multi-channel transmission by controlling the generation of the modulation signal through an electronic switch array, to form a time division multiplexing signal; and the time division multiplexing signal is sequentially passed through the high-Q resonance matching circuit 111, the electric field signal demodulation circuit 114, the A / D conversion 115, and the computer 116 to obtain the corresponding measurement results.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1. The present application uses electronic switch control metal mesh to modulate seawater, and measures the electric field through high-Q quartz resonance matching, has the characteristics of small size, high sensitivity, and high signal-to-noise ratio, and does not need to arrange measuring electrodes and reference electrodes in a large range and at a long distance, so that the sensor can be placed very flexibly to measure different seawater environment electric fields.

[0028] 2. The present application uses high-Q quartz resonance matching mode to obtain passive gain and very narrow frequency band, which is beneficial to improve the signal-to-noise ratio, especially when a plurality of same quartz crystal oscillators are connected in parallel, further improving the passive gain, the seawater modulation electric field output, and the signal-to-noise ratio, and can be used for weaker electric field detection.

[0029] 3. The present application uses a plurality of high-Q quartz resonance matching, so that a small sensor spacing can also obtain the effect of a large-size sensor, providing technical support for phased array electric field sensor design, and the electric field measuring instrument can quickly and real-time scan the seawater electric field distribution. BRIEF DESCRIPTION OF DRAWINGS

[0030] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0031] Figure 1 It is a general block diagram of the weak marine electric field measurement system with high-Q quartz crystal oscillator frequency conversion resonance matching.

[0032] Figure 2 It is an equivalent circuit diagram of a plurality of quartz crystal oscillators with the same characteristics connected in parallel.

[0033] Figure 3 It is a schematic diagram of seawater electric field frequency conversion modulation structure.

[0034] Figure 4 It is an equivalent circuit diagram of a plurality of quartz crystal oscillators with the same characteristics connected in parallel.

[0035] Figure 5 The schematic diagram of the in-phase amplification circuit and the switch demodulation circuit.

[0036] Figure 6 The schematic diagram of the array electric field sensor.

[0037] Wherein, 100-weak ocean electric field; 101-seawater; 102-shield; 103-metal mesh; 104-measuring electrode; 105-reference electrode; 106-electronic switch; 107-ocean electric field modulation circuit; 108-modulation control; 109-transformer; 110-quartz crystal oscillator; 111-high Q value resonance matching circuit; 112-basic amplification circuit; 113-demodulation circuit; 114-electric field signal demodulation circuit; 115-A / D conversion; 116-computer; 117-display; 118-computer and control module; 119-demodulation control. DETAILED DESCRIPTION

[0038] The application will be described in detail below with specific embodiments. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be noted that for those skilled in the art, without departing from the concept of the application, a number of changes and improvements can be made. These are within the scope of the application.

[0039] Example 1

[0040] According to the weak ocean electric field measurement system provided by the application, the high Q value quartz crystal oscillator frequency conversion resonance matching circuit comprises:

[0041] Ocean electric field modulation circuit 107, high Q value resonance matching circuit 111, electric field signal demodulation circuit 114, A / D conversion 115 and computer 116;

[0042] The ocean electric field modulation circuit 107 comprises: shield 102, metal mesh 103, measuring electrode 104, reference electrode 105, electronic switch 106;

[0043] The metal mesh 103, the measuring electrode 104 and the reference electrode 105 are sequentially and parallelly arranged in the shield 103, and the metal mesh 103 is close to the opening surface of the shield 102 and parallel to the opening surface of the shield; the metal mesh 103 is connected with the shield 102 through the electronic switch 106; the measuring electrode 104, the reference circuit 105 and the high Q value resonance matching circuit 111 are connected;

[0044] The measuring electrode 104 and the reference electrode 105 adopt silver chloride electrodes; the shield 102 adopts a corrosion-resistant conductive material; and the metal mesh 103 adopts a seawater corrosion-resistant titanium alloy material.

[0045] The high-Q resonant matching circuit 111 comprises a transformer 109, a quartz crystal oscillator 110, and an output capacitor.

[0046] The measuring electrode 104 is connected to one electrode of the input end of the transformer 109, and the reference electrode 105 is connected to another electrode of the input end of the transformer 109.

[0047] A plurality of quartz crystal oscillators 110 with the same characteristics are connected in parallel, or a single quartz crystal oscillator 110 is used, one end of the parallel-connected quartz crystal oscillators 110 or the single quartz crystal oscillator 110 is connected to one electrode of the output end of the transformer 109, and the other end is respectively connected to an output capacitor and the basic amplification circuit 112; the other electrode of the output end of the transformer 109 and the other end of the output capacitor are grounded.

[0048] The transformer 109 performs impedance transformation, and the plurality of quartz crystal oscillators 110 with the same characteristics are connected in parallel, which not only obtains a high Q value, but also can further reduce the dynamic resistance in the quartz, and the resonant matching circuit can obtain a higher passive gain. Since the quartz matching circuit has a very narrow frequency band, the signal-to-noise ratio of the measurement system is greatly improved, and this resonant matching makes the small-size / interval measuring electrode 104 and the reference electrode 105 also obtain a high electric field sensitivity.

[0049] The basic amplification circuit 112 adopts a same-phase high-speed operational amplifier.

[0050] The electric field signal demodulation circuit 114 comprises the basic amplification circuit 112 and the demodulation circuit 113, which amplifies and demodulates the modulated signal, can take out the high-frequency modulation frequency, and obtains the amplitude of the electric field signal.

[0051] The high-Q resonant matching circuit 111 enhances the amplitude of the input signal, and then sequentially inputs the basic amplification circuit 112 and the demodulation circuit 113 to obtain the demodulated electric field signal; the A / D conversion 115 converts the demodulated electric field signal into a digital signal; and then the digital signal is input into the computer 116 for signal processing to obtain the final measurement result.

[0052] The computer 116 controls the electronic switch 106 to modulate the seawater electric field signal according to the measurement requirement, and also controls the demodulation circuit 113.

[0053] The computer 116 generates a modulation control to turn on or turn off the electronic switch 106; when the electronic switch 106 is turned on, the metal mesh 103 is short-circuited with the shield 102, the opening of the shield 102 is filled by the metal mesh 103, the seawater electric field is blocked, so that the electric field cannot reach the measuring electrode 104 and the reference electrode 105; when the electronic switch 106 is turned off, the seawater electric field can reach the measuring electrode 104 and the reference electrode 105 through the opening of the shield 102 and the metal mesh 103.

[0054] When the electronic switch 106 is turned off, the seawater electric field can reach the measuring electrode 104 and the reference electrode 105 through the opening of the shield 102 and the metal mesh 103, the potential difference between the measuring electrode 104 and the reference electrode 105 is taken as an output signal and transmitted to the high-Q resonance matching circuit 111.

[0055] The demodulation circuit 113 is a switching demodulation circuit, and the switching is controlled by the computer 116 to convert the modulated high-frequency signal into a difference frequency signal with the demodulation control frequency.

[0056] The present application has the characteristics of small volume, high resolution and high signal-to-noise ratio, and provides a feasible idea for arrayed seawater electric field measurement.

[0057] Embodiment 2

[0058] Embodiment 2 is a preferred example of embodiment 1

[0059] According to the present application, a weak ocean electric field measurement method with high-Q quartz crystal oscillator frequency conversion resonance matching can realize high-sensitivity weak ocean electric field 100 measurement with small volume / pitch. In order to realize efficient reception of weak ocean electric field 100 signals with small volume / pitch, the present application controls the metal mesh 103 to realize ocean electric field modulation for the measuring electrode 104 and the reference electrode 105 through the electronic switch 106; high-Q resonance matching is realized by using the transformer 109 and the parallel connection 110 of multiple quartz crystal oscillators with the same characteristics, so that even if the seawater 101 electric field frequency is changed to a very high frequency, the measuring electrode 104 and the reference electrode 105 with small volume / pitch can also ensure to obtain a large electric field response; the modulated electric field signal is demodulated through the basic amplification circuit 112 and the demodulation circuit 113; the electric field signal size is obtained through A / D conversion 115 and computer 116, and is sent to the display 117 output, at the same time, the computer 116 controls the electronic switch 106 to realize electric field signal modulation, such as Figure 1The metal net 103 is placed in front of the measuring electrode 104 and the reference electrode 105, and is connected to the shield 102 through the electronic switch 106. When the electronic switch 106 is open, the electric field in the seawater 101 can pass through the metal net 103 to the measuring electrode 104 and the reference electrode 105 without any obstruction; when the electronic switch 106 is closed, the metal net 103 is connected to the shield 102, and the electric field in the seawater 101 is blocked by the metal net 103. The electric field between the measuring electrode 104 and the reference electrode 105 is modulated by the on-off switching of the electronic switch, so that the low-frequency electric field signal is converted to a high-frequency signal, which facilitates the efficient matching of the small-size / pitch measuring electrode 104 and the reference electrode 105. In order to realize the efficient matching of the high-frequency modulated signal, the present application provides a plurality of quartz crystal oscillators with the same characteristics connected in parallel to a matching circuit, and the equivalent circuit is as shown in Figure 2 Since each quartz crystal oscillator in the matching circuit has a very high Q value, and the gain of resonance is greatly improved after being connected in parallel, the matching circuit has a passive amplification effect, which compensates for the large loss caused by the nonlinearity of the up-conversion, and also greatly improves the signal-to-noise ratio of the matching circuit. Here, the transformer 109 realizes the impedance matching effect. Obviously, the circuit makes it possible to realize high-frequency modulation and super-efficient matching, so that very good measurement sensitivity can be obtained even in the case of small-size / pitch measuring / reference electrodes. After being amplified by the amplification circuit 112 and demodulated by the demodulation circuit 113, the low-frequency electric field signal can be obtained and sent to the computer 116 for electric field measurement through A / D conversion 115. The modulation control 108 and the demodulation control 119 of the electronic switch 106 are generated by the computer 116. This seawater electric field measurement method can greatly reduce the size of the sensor and the electrode pitch, and make it possible to realize a small array sensor, because the modulation frequency can be very high, the amplitude of the matched output can be passively amplified, and the signal-to-noise ratio can be greatly improved by using parallel quartz crystal oscillators for frequency conversion matching. The seawater electric field measurement system constructed by this method not only can measure the vector electric field, but also can constitute an electric field sensor phased array system to measure the distribution of seawater electric field at a long distance, greatly expanding the application field of the method in ocean electric field measurement.

[0060] Example 3

[0061] Example 3 is a preferred example of Example 1 and / or Example 2

[0062] A metal net is placed at the opening of the front end of the shield, an electronic switch is connected to the metal net and the shield, the on-off of the electronic switch is controlled by a computer, and the measuring electrode and the reference electrode are placed behind the metal net in turn. The potential difference between the measuring electrode and the reference electrode is the output signal sent to a matching circuit, as shown in Figure 3The measuring electrode and the reference electrode adopt silver chloride electrodes, the shield adopts corrosion-resistant conductive material, and the metal mesh adopts seawater corrosion-resistant titanium alloy material. The switch is alternately turned on and off, so that the electric field reaching the measuring electrode and the reference electrode is alternately blocked, the low-frequency electric field is modulated to a high-frequency signal, which facilitates the suppression of electric field drift and the reduction of the size and spacing of the measuring / reference electrode. In order to reduce the volume and the spacing between the electrodes, the modulation frequency of the up-conversion is usually relatively high, but the modulation process also causes nonlinear loss, and too high up-conversion will cause loss of the signal, and the traditional LC matching circuit is difficult to compensate for the loss caused by too high conversion, and the Q value of the LC matching circuit is too low, which is not conducive to the suppression of noise signals. Therefore, the application proposes to use the parallel method of the same characteristic quartz to realize high-gain matching, here, three quartz crystal oscillators with the same frequency characteristic of 32.768 kHz are connected in parallel, and the equivalent circuit is as shown in Figure 4 . Figure 1 The impedance change in the transformer and the measuring / reference electrode in the seawater has been equivalent to the internal impedance Z i . Since the three quartz crystal oscillators have the same characteristics, at this time, the dynamic resistance and inductance of the equivalent quartz crystal oscillator circuit are 1 / 3 (r Y =1 / 3r Y1 , L Y =1 / 3L Y1 ) of a single quartz crystal, and the internal capacitance and distributed capacitance of the equivalent quartz crystal oscillator circuit are 3 times (C Y =3C Y1 , C0=1 / 3C 01 ) of a single quartz. Since the dynamic resistance is reduced, the parallel quartz crystal oscillator can obtain larger passive gain than a single quartz, and the matching circuit formed thereby not only compensates for the loss caused by frequency conversion, but also enhances the output amplitude, thereby greatly improving the signal-to-noise ratio.

[0063] Due to the ultra-high Q value of the quartz crystal oscillator, the input impedance of the amplifier must be very high, and here a same-phase high-speed operational amplifier is used to amplify the 32.768 kHz signal, and the demodulation circuit is a switching demodulation circuit, which converts the modulated high-frequency signal into a difference frequency signal with the demodulation control frequency through switching, and then filters out the high-frequency component through a low-pass filter to obtain an output only related to the amplitude of the ocean electric field signal, as shown in Figure 5 .

[0064] A / D conversion converts the demodulated electric field signal into a digital signal, which is sent to a computer, and the computer obtains the final measurement result after signal processing and outputs and displays. The computer controls the electronic switch to modulate the seawater electric field signal, and at the same time, the computer controls the demodulation circuit to convert the high-frequency signal into a low-frequency signal.

[0065] Since the sensor uses multiple high-Q quartz crystal resonators for resonance matching, the modulation frequency can be made higher, thus greatly reducing the volume, and therefore, multiple sensor units containing measurement electrodes and reference electrodes are combined to form an array sensor, as shown in Figure 6 The modulation signal is generated by an electronic switch array, and the outputs of the measurement electrodes and reference electrodes are combined into one signal by multi-channel transmission synthesis, forming a time-division multiplexing signal. Multiple quartz crystal resonators provide high gain and signal-to-noise ratio, and after being amplified and filtered by a conditioning circuit, the signal is demodulated by a demodulation circuit to obtain a low-frequency electric field signal. The analog signal is converted to a digital signal by an A / D converter and sent to a computer for analysis and calculation. The computer controls the modulation switch scanning, multi-channel transmission synthesis, and demodulation circuit to realize phased array seawater electric field distribution measurement.

[0066] Example 4

[0067] Example 4 is a preferred example of Example 1

[0068] In Example 1, the multiple quartz crystal resonators in parallel are replaced by multiple FBAR resonators. Although the quality factor decreases slightly, FBAR resonators have similar Q values, and good sensitivity and signal-to-noise ratio can be achieved in a small volume / pitch. Since quartz crystal resonators usually have only tens of MHz, while FBAR resonators can reach several GHz, FBAR resonators can operate at higher frequencies than quartz crystal resonators. Therefore, using the same principle, FBAR resonators are expected to form a more miniature electric field sensor, providing a design method for small electric field sensor arrays.

[0069] Example 5

[0070] Example 5 is a preferred example of Example 1

[0071] In Example 1, the multiple quartz crystal resonators in parallel are replaced by a single quartz crystal resonator. Although the amplification gain decreases, the narrowband characteristic is still retained, and good sensitivity and signal-to-noise ratio can be achieved in a small volume / pitch.

[0072] Example 6

[0073] Example 6 is a preferred example of Example 1

[0074] In Example 1, the transformer is directly removed. Although there is no impedance transformation, the matching performance is slightly reduced, but multiple quartz crystal resonators in parallel can still achieve high gain and good narrowband characteristics, and good sensitivity and signal-to-noise ratio can be achieved in a small volume / pitch.

[0075] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be combined with each other at will without conflict.

Claims

1. A weak ocean electric field measuring system of high Q quartz crystal oscillator frequency conversion resonance matching, characterized in that, The utility model relates to a kind of ocean electric field modulation circuit (107), high Q resonance matching circuit (111), electric field signal demodulation circuit (114), A / D conversion (115) and computer (116);The ocean electric field modulation circuit (107) includes: shield (102), metal net (103), measuring electrode (104), reference electrode (105), electronic switch (106);The metal net (103), the measuring electrode (104) and the reference electrode (105) are sequentially arranged in the shield (102), and the metal net (103) is close to the opening surface of the shield (102), and is parallel with the opening surface of the shield;The metal net (103) is connected with the shield (102) by the electronic switch (106);The measuring electrode (104), the reference electrode (105) are connected with the high Q resonance matching circuit (111);The high Q resonance matching circuit (111), the electric field signal demodulation circuit (114), the A / D conversion (115) and the computer (116) are sequentially connected;The high Q resonance matching circuit (111) includes: transformer (109), quartz crystal oscillator (110) and output capacitor;The measuring electrode (104) is connected with one electrode of the input end of the transformer (109);The reference electrode (105) is connected with another electrode of the input end of the transformer (109);A plurality of the quartz crystal oscillator (110) of same characteristic is connected in parallel or a single quartz crystal oscillator (110) is used, and one end of the quartz crystal oscillator (110) connected in parallel or the single quartz crystal oscillator (110) is connected with one electrode of the output end of the transformer (109), and the other end is connected with output capacitor and basic amplification circuit (112) respectively;The other electrode of the output end of the transformer (109) and the other end of the output capacitor are grounded. The high Q resonance matching circuit (111) does not contain transformer, and only through a plurality of the quartz crystal oscillator (110) of same characteristic connected in parallel or a single quartz crystal oscillator (110) to realize gain and narrowband characteristics. The computer (116) generates modulation control and turns on or turns off the electronic switch (106);When the electronic switch (106) is turned on, the metal net (103) is short-circuited with the shield (102), the opening of the shield (102) is filled with the metal net (103), and the electric field of seawater is blocked by the metal net (103), so that electric field cannot reach the measuring electrode (104) and the reference electrode (105);When the electronic switch (106) is turned off, the electric field of seawater can reach the measuring electrode (104) and the reference electrode (105) through the opening of the shield (102) and the metal net (103);The electronic switch (106) is alternately turned on and turned off, and the electric field between the measuring electrode (104) and the reference electrode (105) is modulated, so as to change low-frequency electric field signal into high-frequency. ​ ​ ​ ​ ​ 2. The weak ocean electric field measuring system of claim 1, wherein, ​ 3. The weak ocean electric field measuring system of claim 1, wherein the high Q quartz crystal oscillator is a crystal oscillator with a Q value of 10,000 or more. ​ 4. The weak ocean electric field measuring system of claim 3, wherein the high Q quartz crystal oscillator is a crystal oscillator of 32,768 Hz. When the electronic switch (106) is off, the seawater electric field can reach the measuring electrode (104) and the reference electrode (105) through the opening of the shield cover (102) and the metal mesh (103), and the potential difference between the measuring electrode (104) and the reference electrode (105) is transmitted to the high-Q resonance matching circuit (111) as an output signal.

5. The weak ocean electric field measuring system of claim 1, wherein, The measuring electrode (104) and the reference electrode (105) adopt silver chloride electrodes; the shield cover (102) adopts a corrosion-resistant conductive material; and the metal mesh (103) adopts a seawater corrosion-resistant titanium alloy material.

6. The weak ocean electric field measuring system of claim 3, wherein the high Q quartz crystal oscillator is a crystal oscillator with a Q value of 10,000 or more. The electric field signal demodulation circuit (114) comprises a basic amplification circuit (112) and a demodulation circuit (113); The high-Q resonance matching circuit (111) enhances the amplitude of the input signal, and then inputs the basic amplification circuit (112) and the demodulation circuit (113) in sequence to obtain the demodulated electric field signal; the A / D conversion (115) converts the demodulated electric field signal into a digital signal; and then the digital signal is input into the computer (116) for signal processing to obtain the final measurement result.

7. The weak ocean electric field measuring system of claim 6, wherein the high Q quartz crystal oscillator is a 32 kHz crystal oscillator. The basic amplification circuit (112) adopts a non-inverting high-speed operational amplifier; The demodulation circuit (113) is a switch demodulation circuit, and the switch is controlled by the computer (116) to convert the modulated high-frequency signal into a difference frequency signal with the demodulation control frequency.

8. The weak ocean electric field measuring system of claim 1, wherein, The system further comprises: a plurality of the marine electric field modulation circuits (107) combined to form an array sensor, and a plurality of electronic switch arrays are used to control the generation of modulation signals; the output of the measuring electrode (104) and the reference electrode (105) is transmitted through multiple channels and merged into a signal to form a time division multiplexing signal; and the time division multiplexing signal is sequentially input into the high-Q resonance matching circuit (111), the electric field signal demodulation circuit (114), the A / D conversion (115), and the computer (116) to obtain the corresponding measurement results.

9. A weak ocean electric field measuring system using high Q quartz crystal oscillator frequency conversion resonance matching, characterized in that, It comprises: a marine electric field modulation circuit (107), a high-Q resonance matching circuit (111), an electric field signal demodulation circuit (114), an A / D conversion (115), and a computer (116); The marine electric field modulation circuit (107) comprises a shield cover (102), a metal mesh (103), a measuring electrode (104), a reference electrode (105), and an electronic switch (106); The metal mesh (103), the measuring electrode (104), and the reference electrode (105) are sequentially and parallelly arranged in the shield cover (102), and the metal mesh (103) is close to and parallel with the opening surface of the shield cover (102); the metal mesh (103) is connected with the shield cover (102) through the electronic switch (106); and the measuring electrode (104), the reference electrode (105), and the high-Q resonance matching circuit (111) are connected; The high-Q resonance matching circuit (111), the electric field signal demodulation circuit (114), the A / D conversion (115), and the computer (116) are sequentially connected; The high Q-value resonance matching circuit (111) comprises a transformer (109), an FBAR resonator and an output capacitor; The measuring electrode (104) is connected with one electrode of the input end of the transformer (109), and the reference electrode (105) is connected with another electrode of the input end of the transformer (109); A plurality of the FBAR resonators are connected in parallel or a single FBAR resonator is adopted, one end of the FBAR resonators connected in parallel or the single FBAR resonator is connected with one electrode of the output end of the transformer (109), and the other end is respectively connected with the output capacitor and a basic amplification circuit (112); the other electrode of the output end of the transformer (109) and the other end of the output capacitor are grounded.

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