CN111211751A - Automatic gain digital demodulation chopping amplification method and circuit - Google Patents
Automatic gain digital demodulation chopping amplification method and circuit Download PDFInfo
- Publication number
- CN111211751A CN111211751A CN202010147847.8A CN202010147847A CN111211751A CN 111211751 A CN111211751 A CN 111211751A CN 202010147847 A CN202010147847 A CN 202010147847A CN 111211751 A CN111211751 A CN 111211751A
- Authority
- CN
- China
- Prior art keywords
- signal
- gain
- module
- amplification
- circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000003321 amplification Effects 0.000 title claims abstract description 167
- 238000003199 nucleic acid amplification method Methods 0.000 title claims abstract description 167
- 238000000034 method Methods 0.000 title claims abstract description 52
- 238000005070 sampling Methods 0.000 claims abstract description 66
- 238000002955 isolation Methods 0.000 claims abstract description 29
- 238000001914 filtration Methods 0.000 claims abstract description 23
- 238000006243 chemical reaction Methods 0.000 claims abstract description 8
- 238000012216 screening Methods 0.000 claims abstract description 7
- 230000001360 synchronised effect Effects 0.000 claims description 36
- 238000000605 extraction Methods 0.000 claims description 9
- 230000002441 reversible effect Effects 0.000 claims description 4
- 238000001514 detection method Methods 0.000 abstract description 7
- 230000005684 electric field Effects 0.000 description 16
- 238000010586 diagram Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 238000005259 measurement Methods 0.000 description 4
- 238000013461 design Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3089—Control of digital or coded signals
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D1/00—Demodulation of amplitude-modulated oscillations
- H03D1/02—Details
- H03D1/04—Modifications of demodulators to reduce interference by undesired signals
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D1/00—Demodulation of amplitude-modulated oscillations
- H03D1/22—Homodyne or synchrodyne circuits
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/68—Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/001—Digital control of analog signals
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3005—Automatic control in amplifiers having semiconductor devices in amplifiers suitable for low-frequencies, e.g. audio amplifiers
- H03G3/3026—Automatic control in amplifiers having semiconductor devices in amplifiers suitable for low-frequencies, e.g. audio amplifiers the gain being discontinuously variable, e.g. controlled by switching
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3052—Automatic control in amplifiers having semiconductor devices in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver
- H03G3/3063—Automatic control in amplifiers having semiconductor devices in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver using at least one transistor as controlling device, the transistor being used as a variable impedance device
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3052—Automatic control in amplifiers having semiconductor devices in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver
- H03G3/3078—Circuits generating control signals for digitally modulated signals
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Multimedia (AREA)
- Amplifiers (AREA)
Abstract
The invention relates to an automatic gain digital demodulation chopping amplification method and a circuit, wherein the method comprises the following steps: modulating a low-frequency signal at the input end of the circuit into a high-frequency alternating current signal through chopping; carrying out isolation transformer amplification, fixed gain amplification and programmable gain amplification on the high-frequency alternating current signal; performing analog-to-digital conversion sampling on the amplified high-frequency alternating current signal in synchronization with the chopped wave modulation signal, and digitizing the high-frequency alternating current signal; screening effective signals from the digitized high-frequency alternating-current signals according to sampling points, and performing signal average filtering to complete digital demodulation; filtering the digitally demodulated signal to obtain signal amplitude information; comparing the signal amplitude information with a preset gain control threshold value, and judging whether gain adjustment is carried out or not; the gain is adjusted by controlling the programmable gain amplifying circuit. The method can be used for collecting low-frequency weak signals, effectively improves the measuring range of the low-frequency weak signals, and can be used for low-input-impedance weak signal detection, amplification and collection occasions.
Description
Technical Field
The invention belongs to the technical field of marine electromagnetic detection, and particularly relates to an automatic gain digital demodulation chopping amplification method and circuit.
Background
Marine electromagnetic prospecting methods are divided into natural field sources (Marine MT, Marine magnetotelluric method) and artificial field sources (Marine CSEM, Marine controlled source electromagnetic method). An electromagnetic data recorder carried on a submarine electromagnetic acquisition station or a towed electric field acquisition station is one of key equipment for marine electromagnetic exploration and is responsible for acquiring submarine weak electric field and magnetic field signals. Weak magnetic field signals are collected by an ultra-low noise magnetic field sensor, and the background noise density of the magnetic field sensor is lower than that of the magnetic field sensor
Electric field signal utilization' solid nonpolarized electrode + ultra-low noise amplifierLarge circuit collection, the requirement of the background noise density of the collection channel is lower than
The main key problems in the weak electric field signal detection, amplification and acquisition method based on the 'solid non-polarized electrode + ultra-low noise amplification circuit' are as follows: 1) noise of the amplifying circuit; 2) the measurement range of the electric field signal.
An electric field signal amplification and acquisition circuit of a solid-state non-polarized electrode and low-noise amplification circuit commonly used at present is a fixed-gain analog demodulation chopping amplification circuit, a chopping modulation amplification mode is adopted to avoid 1/f noise of integrated operational amplification, an integrated operational amplification circuit and a filter circuit are adopted to complete demodulation and restoration of chopping modulation signals before A/D sampling, and a certain fixed gain is adopted to offset A/D sampling noise. The fixed gain analog demodulation chopping amplification method has the main problems that: 1) by adopting an analog demodulation method based on an integrated operational amplifier and a filter circuit, circuit impact noise in the demodulation process is coupled into an effective electric field signal, so that the noise of an amplifying circuit is improved, and the acquisition of a weak electric field signal is not facilitated; 2) the gain of the amplifying circuit is fixed, so that the contradiction between the effective detection requirement of weak signals and the non-overflow requirement of large signal detection is caused, particularly in the electromagnetic exploration of an artificial field source, the dynamic range of electric field signals is large, and the fixed gain mode is difficult to meet the requirement of the measurement range of the electric field signals. Aiming at the problem of fixed gain of a fixed gain analog demodulation chopping amplification method, a double-gain amplification circuit is adopted for part of electric field signal acquisition of marine electromagnetic exploration, wherein one high-gain amplification weak signal and one low-gain amplification strong signal are adopted, and the method brings the problems of circuit size, power consumption and data volume recording.
Therefore, aiming at the problem of the fixed-gain analog demodulation chopping amplification method, the invention provides an automatic-gain digital demodulation chopping amplification method, which can be used for acquisition of marine weak electric field signals and can be popularized and applied to weak signal detection, amplification and acquisition occasions with low input impedance.
Disclosure of Invention
The invention provides an automatic gain digital demodulation chopping amplification method and a circuit aiming at the technology of the fixed gain analog demodulation chopping amplification method.
In order to achieve the above object, the present invention provides an automatic gain digital demodulation chopping amplification method, including:
modulating a low-frequency signal at the input end of the circuit into a high-frequency alternating current signal through chopping;
carrying out isolation transformer amplification, fixed gain amplification and programmable gain amplification on the high-frequency alternating current signal;
performing analog-to-digital conversion sampling on the amplified high-frequency alternating current signal in synchronization with the chopped wave modulation signal to realize digitization of the high-frequency alternating current signal;
screening effective signals from the digitized high-frequency alternating-current signals according to sampling points, and performing signal average filtering to complete digital demodulation;
filtering the digitally demodulated signal to obtain signal amplitude information;
comparing the signal amplitude information with a preset gain control threshold value, and judging whether gain adjustment is carried out or not;
the gain adjustment is realized by controlling the programmable gain amplifying circuit.
Preferably, the method for performing analog-to-digital conversion sampling on the amplified high-frequency alternating current signal in synchronization with the chopper modulation signal to realize digitization of the high-frequency alternating current signal comprises the following steps:
and after phase compensation, the chopped wave modulation signal is used as a synchronous control signal for analog-to-digital conversion sampling, so that the digitization of the high-frequency alternating current signal is realized.
Preferably, the method for filtering the digitized high-frequency alternating current signal by filtering the effective signal according to the sampling point and performing signal average filtering to complete digital demodulation comprises the following steps:
setting the same number of sampling points on each positive half cycle and each negative half cycle of the amplified high-frequency alternating current signal according to the chopped wave modulation signal;
and (3) omitting the first sampling point and the last sampling point data of each half cycle, taking the residual sampling points as effective sampling points, respectively accumulating the effective sampling points corresponding to the positive half cycle and the negative half cycle, then taking an average value, determining the average value as a sampling value, and performing digital demodulation.
Preferably, the method for comparing the signal amplitude information with a preset gain control threshold value to determine whether to perform gain adjustment includes:
dividing the gain into a plurality of gain segment levels, setting the gain control threshold value of each segment level, wherein the gain values of adjacent gain segment levels are different by one time;
and comparing the signal amplitude information with a gain control threshold value, judging the grade of a gain section where the signal amplitude information is positioned, and judging whether to perform gain adjustment according to the gain value of the grade of the gain section where the signal amplitude information is positioned.
The invention also provides an automatic gain digital demodulation chopping amplification circuit, and the automatic gain digital demodulation chopping amplification method comprises the following steps: the device comprises a preposed analog amplifying circuit, a signal acquisition circuit and a digital main control circuit;
the preposed analog amplification circuit comprises a low-noise chopping modulation module, an isolation transformer amplification module, a fixed gain amplification module and a programmable gain amplification module; an input signal is accessed to the input side of the low-noise chopping modulation module, the input side of the isolation transformer amplification module is accessed to the output end of the low-noise chopping modulation module, the fixed gain amplification module is connected to the output side of the isolation transformer amplification module in series, and the programmable gain amplification module is connected to the output end of the fixed gain amplification module in series; the low-frequency signal of the signal input end is modulated into a high-frequency alternating current signal by a low-noise chopping modulation module, the signal is amplified by a fixed gain through an isolation transformer amplification module and a fixed gain amplification module, and the signal is amplified by a programmable gain amplification module to realize automatic gain amplification;
the signal acquisition circuit is connected to the output end of the programmable gain amplification module to acquire an output signal of the programmable gain amplification module, realize the digitization of the high-frequency alternating current signal and transmit the high-frequency alternating current signal to the digital main control circuit;
the digital main control circuit is connected with the signal acquisition circuit, the low-noise chopping modulation module and the programmable gain amplification module so as to control the low-noise chopping modulation module to modulate the low-frequency signal into a high-frequency alternating-current signal and control the programmable gain amplification module to perform automatic gain amplification according to the extracted amplitude information of the signal output by the programmable gain amplification module.
Preferably, the low-noise chopping modulation module adopts a bridge type reversible chopping circuit.
Preferably, the isolation transformer amplification module adopts a small-signal audio isolation transformer and is connected to the output end of the low-noise chopping modulation module in a differential mode; the fixed gain amplification module adopts an active band-pass in-phase amplification circuit based on an ultra-low noise integrated operational amplifier, and the input end of the amplifier is connected to the output side of the isolation transformer amplification module.
Preferably, the programmable gain amplification module is connected in series to the output end of the fixed gain amplification module;
the programmable gain amplification module adopts a programmable gain inverting amplification circuit based on an ultra-low noise integrated operational amplifier, and the programmable gain is realized by controlling the resistance value of a feedback resistor by a high-precision digital-to-analog converter.
Preferably, the signal acquisition circuit adopts a multi-path synchronous analog-to-digital converter.
Preferably, the digital main control circuit comprises a chopping modulation module, a synchronous acquisition module, a digital demodulation module, a signal amplitude extraction module, an automatic gain control module and a gain control digital-to-analog driving module;
the chopping modulation module is connected with the low-noise chopping modulation module, is used for providing chopping modulation signals for the preposed analog amplification circuit, and is connected with the synchronous acquisition module, and is used for providing synchronous signals for the synchronous acquisition module;
the synchronous acquisition module is connected with the signal acquisition circuit and is used for providing a hardware logic sampling controller for the signal acquisition circuit and realizing signal synchronous sampling through the signal acquisition circuit under the synchronous control of a chopped wave modulation signal;
the digital demodulation module is connected with the synchronous acquisition module and is used for screening effective signals according to sampling points, carrying out signal average filtering and finishing digital demodulation;
the signal amplitude extraction module is used for filtering the digitally demodulated signal to obtain a signal amplitude;
the automatic gain control module is used for comparing the signal amplitude with a gain control threshold value and judging whether to carry out gain adjustment or not;
and the gain control digital-to-analog driving module is used for driving the programmable gain amplification module to amplify according to the adjusted gain.
Compared with the prior art, the invention has the advantages and positive effects that:
(1) and a two-stage amplification mode combining fixed gain amplification and programmable gain amplification is adopted, and the programmable gain amplification is automatically controlled according to the extracted amplitude information of the output signal of the second-stage amplification circuit so as to realize automatic gain control. Compared with a fixed gain method, the signal measurement range can be effectively improved; compared with a double-gain method, the method has the advantages of circuit size, power consumption and data volume recording, and the number of the preposed analog amplifying circuits is small, and the data volume recording is small.
(2) Compared with an analog demodulation method based on an analog switch circuit, the digital demodulation method can screen effective signals according to sampling points, avoids circuit peak noise introduced by a chopping modulation circuit, and simultaneously avoids circuit impact noise introduced by the analog demodulation circuit.
Drawings
FIG. 1 is a schematic block diagram of an automatic gain digital demodulation chopper amplification method of the present invention;
FIG. 2 is a schematic circuit diagram of an automatic gain digital demodulation chopper amplifier circuit of the present invention;
FIG. 3 is a schematic diagram of digital demodulation based on chopper modulation according to the present invention;
FIG. 4 is a schematic diagram of the gain section of the automatic gain control of the present invention;
FIG. 5 shows the result of the automatic gain control test of the automatic gain digital demodulation chopper amplifier circuit of the present invention;
FIG. 6 is a result of a marine environment test of the automatic gain digital demodulation chopper amplification circuit of the present invention;
fig. 7 is a result of a marine environment test of a fixed-gain analog demodulation chopper amplification circuit.
Detailed Description
Hereinafter, embodiments of the present invention will be further described with reference to the accompanying drawings.
The embodiment of the invention provides an automatic gain digital demodulation chopping amplification method, which comprises the following steps:
modulating a low-frequency signal at the input end of the circuit into a high-frequency alternating current signal through chopping;
carrying out isolation transformer amplification, fixed gain amplification and programmable gain amplification on the high-frequency alternating current signal;
and performing analog-to-digital conversion sampling on the amplified high-frequency alternating current signal in synchronization with the chopping modulation signal, setting the same number of sampling points on each positive half cycle and each negative half cycle according to the chopping modulation signal, screening effective signals according to the sampling points, and performing average filtering on the effective signals to realize digital demodulation.
Filtering the digitally demodulated signal to obtain signal amplitude information;
comparing the signal amplitude information with a preset gain control threshold value, and judging whether gain adjustment is carried out or not; dividing the gain into a plurality of gain segment levels, setting the gain control threshold value of each segment level, wherein the gain values of adjacent gain segment levels are different by one time; and comparing the signal amplitude information with a gain control threshold value, judging the grade of a gain section where the signal amplitude information is positioned, and judging whether to perform gain adjustment according to the gain value of the grade of the gain section where the signal amplitude information is positioned.
According to the automatic gain digital demodulation chopping amplification method, the invention can design a corresponding amplification circuit, the functional block diagram of which is shown in figure 1 and comprises a preposed analog amplification circuit, a signal acquisition circuit and a digital main control circuit;
the preposed analog amplifying circuit comprises a low-noise chopping modulation module, an isolation transformer amplifying module, a fixed gain amplifying module and a programmable gain amplifying module. The input side of the low-noise chopping modulation module is connected with an input signal, the input side of the isolation transformer amplification module is connected with the output end of the low-noise modulation module, the fixed gain amplification module is connected to the output side of the isolation transformer amplification module in series, and the fixed gain amplification module and the preceding stage isolation transformer amplification module form fixed gain amplification; the programmable gain amplification module is connected to the output end of the fixed gain amplification module in series. The low-frequency signal of the signal input end is modulated into a high-frequency alternating current signal through the low-noise chopping modulation module, the fixed gain signal is amplified through the isolation transformer amplification module and the fixed gain amplification module, and the automatic gain amplification is carried out through the programmable gain amplification module.
The signal acquisition circuit is connected to the output end of the programmable gain amplification module so as to acquire amplitude information of signals output by the programmable gain amplification module and transmit the amplitude information to the digital main control circuit. The digital main control circuit is connected with the signal acquisition circuit, the low-noise modulation module and the programmable gain amplification module so as to control the low-noise chopping modulation module to modulate the low-frequency signal into a high-frequency alternating-current signal and control the programmable gain amplification module to perform automatic gain amplification according to the extracted amplitude information of the signal output by the programmable gain amplification module.
Referring further to fig. 1, the digital main control circuit specifically includes a chopper modulation module, a synchronous acquisition module, a digital demodulation module, a signal amplitude extraction module, an automatic gain control module, and a gain control digital-to-analog driving module. The chopper modulation module is connected with the low-noise chopper modulation module and used for providing chopper modulation signals for the preposed analog amplification circuit, and the chopper modulation module is connected with the synchronous acquisition module and used for providing synchronous signals for the synchronous acquisition module; the synchronous acquisition module is connected with the signal acquisition circuit, provides a hardware logic sampling controller for the signal acquisition module, and realizes signal synchronous sampling through the signal acquisition circuit under the synchronous control of the chopped wave modulation signal. The digital demodulation module is connected with the synchronous acquisition module and is used for screening effective signals according to sampling points, carrying out signal average filtering and finishing digital demodulation; the signal amplitude extraction module is used for filtering the digitally demodulated signal to obtain a signal amplitude; the automatic gain control module is used for comparing the signal amplitude with a gain control threshold value and judging whether to carry out gain adjustment or not; the gain control digital-to-analog driving module is used for driving the programming gain amplification module to amplify according to the adjusted gain.
Fig. 2 shows a schematic circuit diagram of an actually designed automatic gain digital demodulation chopping amplifying circuit, and in this embodiment, a low-noise chopping modulation module adopts a bridge type reversible chopping circuit composed of four identical FET switching tubes to modulate a low-frequency signal to an amplitude of a high-frequency alternating-current signal.
The isolation transformer amplification module is responsible for electrical isolation, impedance matching and signal amplification, a small-signal audio isolation transformer is selected, a difference mode is adopted to be connected to the output end of the low-noise chopping modulation module, the high input impedance of the subsequent fixed gain amplification module is converted into low input impedance to be matched with the impedance of the sensor, the signal-to-noise ratio is improved, and meanwhile, signal amplification gain is achieved. The fixed gain amplification module adopts an active band-pass in-phase amplification circuit based on an ultra-low noise integrated operational amplifier, the input end of the amplifier is connected to the output side of an isolation transformer, the amplifier has fixed gain and is connected with a preceding stage isolation transformer in series to form fixed gain amplification, the characteristic of a band-pass filter can effectively filter power frequency interference and high frequency interference, and the ultra-low noise integrated operational amplifier adopts an ultra-low noise high input impedance integrated operational amplifier.
And for the programmable gain amplification module, the programmable gain amplification module is connected to the output end of the fixed gain amplification module in series. The programmable gain amplification module is specifically a programmable gain inverting amplification circuit based on an ultra-low noise integrated operational amplifier, provides program-controlled gain for weak signals, is connected with the fixed gain amplification module in series, the output of the fixed gain amplification module provides inverting input for the programmable gain inverting amplifier, and the programmable gain is realized by controlling the resistance value of a feedback resistor by a high-precision digital-to-analog converter.
The signal acquisition circuit adopts a multi-channel synchronous analog-to-digital converter and is responsible for synchronous, high-speed, low-noise and high-resolution acquisition of output signals of the preposed analog amplification circuits of a plurality of channels.
The digital main control circuit is responsible for chopped wave modulation, synchronous acquisition, digital demodulation and automatic gain control of a plurality of signal channels. The system architecture of MCU + FPGA is adopted, and FPGA digital logic is responsible for chopper modulation, synchronous acquisition and digital demodulation; the MCU software program is responsible for signal amplitude extraction and circuit gain automatic control algorithm. The FPGA comprises a chopping modulation module, a synchronous acquisition module, a digital demodulation module and a gain control digital-to-analog driving module; the MCU comprises a signal amplitude extraction module and an automatic gain control module.
The chopper modulation logic of the FPGA provides synchronous high-precision modulation signals for each preposed analog amplification circuit, and low-frequency weak signals are modulated into high-frequency alternating-current signals to be amplified in a chopper modulation amplification mode so as to avoid 1/f noise of low-noise integrated operational amplification. The synchronous acquisition logic of the FPGA provides a hardware logic sampling controller for each analog-digital converter chip, each hardware logic sampling controller samples each analog-digital converter chip under the control of the same high-precision clock, and the sampling point of the sampling process is strictly synchronous with the chopped wave modulation signal.
And the digital demodulation logic of the FPGA screens effective signals according to the sampling points, and performs signal average filtering to complete digital demodulation. In the embodiment, the low-noise chopping modulation module adopts a bridge type reversible chopping circuit consisting of four identical FET switching tubes, so that when a low-frequency signal is modulated to a high-frequency alternating-current signal, the switching tubes bring spike burrs in the modulation process. Therefore, the effective signals can be screened by omitting the first sampling point and the last sampling point data of each positive and negative half cycle of the amplified output signals, and taking the rest sampling points as effective sampling points. And accumulating the effective sampling points corresponding to the positive half cycle and the negative half cycle respectively, then averaging the effective sampling points to determine the effective sampling points as sampling values, and performing digital demodulation. Fig. 3 shows a schematic diagram of a digital demodulation principle based on chopper modulation, where an original signal is S1, a modulated signal is S2, a modulated signal is S3, positive and negative half cycle sampling points are indicated in the S4 signal, and S5 is a digitally demodulated signal. The right graph is a partial enlarged view of the left graph, four sampling points are arranged on each half cycle corresponding to the S2 modulation signal, and the first sampling point is designed to be separated from the rising edge of the modulation wave by 1/2 sampling periods. In the S4 signal, a burr brought by a switch tube in the modulation process is arranged at the first sampling point, the data of the first sampling point and the last sampling point of each half cycle are discarded through strict modulation clock synchronization design, the data of the middle two points in the positive half cycle and the negative half cycle of two modulation wave periods are respectively accumulated, the data in the two modulation periods are averaged to obtain a corresponding sampling mean value S5, the signal sampling mean value of each demodulation period is a filtering value of the screened effective signal, and digital demodulation is realized.
Compared with an analog demodulation method based on an analog circuit, the digital demodulation method can screen effective signals according to sampling points, avoids circuit peak noise introduced by a chopping modulation circuit, and the signal sampling value of each demodulation period is the filtering value of the screened effective signals. Meanwhile, circuit impact noise introduced by the analog demodulation circuit is avoided.
The MCU is responsible for signal amplitude extraction and automatic gain control algorithm realization, firstly, signal amplitude information is extracted according to the digitally demodulated signals of the FPGA, and the designed automatic gain control algorithm is adopted to automatically control the gain of the programmable gain amplification module on the basis of filtering the high-frequency noise interference of the amplitude information. In this embodiment, the gain is divided into seven gain segment levels, and the gain values of adjacent gain segment levels are different by one time, as shown in fig. 4, the gain control threshold of each segment level is set, the amplitude information is compared with the gain control threshold, the level of the gain segment where the amplitude information is located is determined, and whether to perform gain adjustment is determined according to the gain value of the gain segment level, so that automatic gain control can be achieved.
As shown in fig. 5, it is a test result of the automatic gain control of the automatic gain digital demodulation chopper amplifier circuit according to the present invention, and it can be seen from the test result that when the input terminal is accessed with signals of different amplitudes, the automatic gain digital demodulation chopper amplifier circuit according to the present invention automatically provides the correct gain control in real time.
As shown in fig. 6, which is a result of a marine environment electric field signal acquisition test using the automatic gain digital demodulation chopper amplification circuit of the present invention, and fig. 7 is a result of a marine environment electric field signal acquisition test using a fixed gain analog demodulation chopper amplification circuit, which is performed simultaneously.
In summary, the present invention employs two-stage amplification, the first stage employs an isolation transformer and fixed gain amplification of an active band-pass in-phase amplification circuit based on an ultra-low noise integrated operational amplifier, the second stage employs programmable gain amplification of the ultra-low noise integrated operational amplifier, and the digital main control circuit automatically controls the programmable gain amplification according to the extracted amplitude information of the output signal of the second stage amplification circuit to implement automatic gain control. The method can be used for collecting marine weak electric field signals, and can effectively improve the electric field signal measurement range compared with a fixed gain method; compared with a double-gain method, the method has the advantages of circuit size, power consumption and data volume recording, and the number of the preposed analog amplifying circuits is small, and the data volume recording is small. Compared with the analog demodulation method based on the analog circuit, the digital demodulation method is adopted, and effective electric field signals can be screened according to sampling points, so that circuit peak noise introduced by a chopper modulation circuit is avoided, and circuit impact noise introduced by the analog demodulation circuit is also avoided. The automatic gain digital demodulation chopping amplification method can be popularized and applied to weak signal detection, amplification and acquisition occasions with low input impedance.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention in other forms, and any person skilled in the art may apply the above modifications or changes to the equivalent embodiments with equivalent changes, without departing from the technical spirit of the present invention, and any simple modification, equivalent change and change made to the above embodiments according to the technical spirit of the present invention still belong to the protection scope of the technical spirit of the present invention.
Claims (10)
1. An automatic gain digital demodulation chopping amplification method, comprising:
modulating a low-frequency signal at the input end of the circuit into a high-frequency alternating current signal through chopping;
carrying out isolation transformer amplification, fixed gain amplification and programmable gain amplification on the high-frequency alternating current signal;
performing analog-to-digital conversion sampling on the amplified high-frequency alternating current signal in synchronization with the chopped wave modulation signal to realize digitization of the high-frequency alternating current signal;
screening effective signals from the digitized high-frequency alternating-current signals according to sampling points, and performing signal average filtering to complete digital demodulation;
filtering the digitally demodulated signal to obtain signal amplitude information;
comparing the signal amplitude information with a preset gain control threshold value, and judging whether gain adjustment is carried out or not;
the gain adjustment is realized by controlling the programmable gain amplifying circuit.
2. The automatic gain digital demodulation chopping amplification method according to claim 1, wherein the method for digitizing the high frequency ac signal by performing analog-to-digital conversion sampling on the amplified high frequency ac signal in synchronization with the chopper-modulated signal comprises:
and after phase compensation, the chopped wave modulation signal is used as a synchronous control signal for analog-to-digital conversion sampling, so that the digitization of the high-frequency alternating current signal is realized.
3. The automatic gain digital demodulation chopping amplification method according to claim 1 or 2, wherein the method for filtering the digitized high-frequency alternating current signal into effective signals according to sampling points and performing signal average filtering comprises the following steps:
setting the same number of sampling points on each positive half cycle and each negative half cycle of the amplified high-frequency alternating current signal according to the chopped wave modulation signal;
and (3) omitting the first sampling point and the last sampling point data of each half cycle, taking the residual sampling points as effective sampling points, respectively accumulating the effective sampling points corresponding to the positive half cycle and the negative half cycle, then taking an average value, determining the average value as a sampling value, and performing digital demodulation.
4. The automatic gain digital demodulation chopping amplification method according to claim 3, wherein the method for comparing the signal amplitude information with a preset gain control threshold value to judge whether to perform gain adjustment comprises the following steps:
dividing the gain into a plurality of gain segment levels, setting the gain control threshold value of each segment level, wherein the gain values of adjacent gain segment levels are different by one time;
and comparing the signal amplitude information with a gain control threshold value, judging the grade of a gain section where the signal amplitude information is positioned, and judging whether to perform gain adjustment according to the gain value of the grade of the gain section where the signal amplitude information is positioned.
5. An automatic gain digital demodulation chopper amplification circuit employing the automatic gain digital demodulation chopper amplification method according to any one of claims 1 to 4, comprising: the device comprises a preposed analog amplifying circuit, a signal acquisition circuit and a digital main control circuit;
the preposed analog amplification circuit comprises a low-noise chopping modulation module, an isolation transformer amplification module, a fixed gain amplification module and a programmable gain amplification module; an input signal is accessed to the input side of the low-noise chopping modulation module, the input side of the isolation transformer amplification module is accessed to the output end of the low-noise chopping modulation module, the fixed gain amplification module is connected to the output side of the isolation transformer amplification module in series, and the programmable gain amplification module is connected to the output end of the fixed gain amplification module in series; the low-frequency signal of the signal input end is modulated into a high-frequency alternating current signal by a low-noise chopping modulation module, the signal is amplified by a fixed gain through an isolation transformer amplification module and a fixed gain amplification module, and the signal is amplified by a programmable gain amplification module to realize automatic gain amplification;
the signal acquisition circuit is connected to the output end of the programmable gain amplification module to acquire an output signal of the programmable gain amplification module, realize the digitization of the high-frequency alternating current signal and transmit the high-frequency alternating current signal to the digital main control circuit;
the digital main control circuit is connected with the signal acquisition circuit, the low-noise chopping modulation module and the programmable gain amplification module so as to control the low-noise chopping modulation module to modulate the low-frequency signal into a high-frequency alternating-current signal and control the programmable gain amplification module to perform automatic gain amplification according to the extracted amplitude information of the signal output by the programmable gain amplification module.
6. The automatic gain digital demodulation chopping amplification circuit of claim 5, wherein the low noise chopping modulation module employs a bridge type reversible chopping circuit.
7. The automatic gain digital demodulation chopping amplification circuit according to claim 5, wherein the isolation transformer amplification module adopts a small signal audio isolation transformer and is connected to the output end of the low noise chopping modulation module in a differential mode; the fixed gain amplification module adopts an active band-pass in-phase amplification circuit based on an ultra-low noise integrated operational amplifier, and the input end of the amplifier is connected to the output side of the isolation transformer amplification module.
8. The automatic gain digital demodulation chopper amplification circuit of any one of claims 5 to 7, wherein the programmable gain amplification module is connected in series to the fixed gain amplification module output;
the programmable gain amplification module adopts a programmable gain inverting amplification circuit based on an ultra-low noise integrated operational amplifier, and the programmable gain is realized by controlling the resistance value of a feedback resistor by a high-precision digital-to-analog converter.
9. The automatic gain digital demodulation chopper-amplifier circuit according to any one of claims 5-7, wherein the signal acquisition circuit employs a multi-way synchronous analog-to-digital converter.
10. The automatic gain digital demodulation chopper amplification circuit of any one of claims 5-7, wherein the digital main control circuit comprises a chopper modulation module, a synchronous acquisition module, a digital demodulation module, a signal amplitude extraction module, an automatic gain control module, and a gain control digital-to-analog driving module;
the chopping modulation module is connected with the low-noise chopping modulation module, is used for providing chopping modulation signals for the preposed analog amplification circuit, and is connected with the synchronous acquisition module, and is used for providing synchronous signals for the synchronous acquisition module;
the synchronous acquisition module is connected with the signal acquisition circuit and is used for providing a hardware logic sampling controller for the signal acquisition circuit and realizing signal synchronous sampling through the signal acquisition circuit under the synchronous control of a chopped wave modulation signal;
the digital demodulation module is connected with the synchronous acquisition module and is used for screening effective signals according to sampling points, carrying out signal average filtering and finishing digital demodulation;
the signal amplitude extraction module is used for filtering the digitally demodulated signal to obtain a signal amplitude;
the automatic gain control module is used for comparing the signal amplitude with a gain control threshold value and judging whether to carry out gain adjustment or not;
and the gain control digital-to-analog driving module is used for driving the programmable gain amplification module to amplify according to the adjusted gain.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010147847.8A CN111211751A (en) | 2020-03-05 | 2020-03-05 | Automatic gain digital demodulation chopping amplification method and circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010147847.8A CN111211751A (en) | 2020-03-05 | 2020-03-05 | Automatic gain digital demodulation chopping amplification method and circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN111211751A true CN111211751A (en) | 2020-05-29 |
Family
ID=70788722
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010147847.8A Pending CN111211751A (en) | 2020-03-05 | 2020-03-05 | Automatic gain digital demodulation chopping amplification method and circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111211751A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111931344A (en) * | 2020-07-09 | 2020-11-13 | 中国海洋大学 | Ocean controllable source electromagnetic optimization wave number sequence selection method based on least square |
| CN112511191A (en) * | 2020-10-26 | 2021-03-16 | 青岛鼎信通讯股份有限公司 | Automatic gain control device for medium-voltage power line signal acquisition |
| CN113281640A (en) * | 2021-07-20 | 2021-08-20 | 常州今创电工有限公司 | Self-diagnosis system and method for direct current chopping acquisition for rail transit |
| CN113839635A (en) * | 2021-09-29 | 2021-12-24 | 四川安迪科技实业有限公司 | Anti-interference self-adaptive AGC (automatic gain control) adjusting method and device based on smooth filtering |
| CN114062192A (en) * | 2021-11-11 | 2022-02-18 | 四川泛华航空仪表电器有限公司 | Frequency-selecting gain conversion circuit and working method thereof |
| CN114094946A (en) * | 2021-11-29 | 2022-02-25 | 中国海洋大学 | Ultra-low noise signal amplification circuit for capacitive marine inert material electrode |
| CN114983424A (en) * | 2022-08-03 | 2022-09-02 | 之江实验室 | Multichannel mixed chopping method and system applied to brain-computer interface chip |
| CN117110650A (en) * | 2023-08-31 | 2023-11-24 | 中国海洋大学 | Acceleration sensor adjusting system capable of adaptively adjusting sensitivity and sensor |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014147436A1 (en) * | 2013-03-21 | 2014-09-25 | Freescale Semiconductor, Inc. | Apparatus and method for monitoring electrical current |
| CN104272590A (en) * | 2012-05-03 | 2015-01-07 | 美国亚德诺半导体公司 | Programmable gain amplifier with common mode sampling |
-
2020
- 2020-03-05 CN CN202010147847.8A patent/CN111211751A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104272590A (en) * | 2012-05-03 | 2015-01-07 | 美国亚德诺半导体公司 | Programmable gain amplifier with common mode sampling |
| WO2014147436A1 (en) * | 2013-03-21 | 2014-09-25 | Freescale Semiconductor, Inc. | Apparatus and method for monitoring electrical current |
Non-Patent Citations (1)
| Title |
|---|
| 刘贵豪: "海洋电磁信号采集关键技术研究", 《中国优秀硕士学位论文全文数据库》 * |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111931344A (en) * | 2020-07-09 | 2020-11-13 | 中国海洋大学 | Ocean controllable source electromagnetic optimization wave number sequence selection method based on least square |
| CN111931344B (en) * | 2020-07-09 | 2024-05-28 | 中国海洋大学 | Least square-based ocean controllable source electromagnetic optimization wave number sequence selection method |
| CN112511191A (en) * | 2020-10-26 | 2021-03-16 | 青岛鼎信通讯股份有限公司 | Automatic gain control device for medium-voltage power line signal acquisition |
| CN113281640A (en) * | 2021-07-20 | 2021-08-20 | 常州今创电工有限公司 | Self-diagnosis system and method for direct current chopping acquisition for rail transit |
| CN113281640B (en) * | 2021-07-20 | 2021-11-02 | 常州今创电工有限公司 | Self-diagnosis system and method for direct current chopping acquisition for rail transit |
| CN113839635B (en) * | 2021-09-29 | 2023-06-20 | 四川安迪科技实业有限公司 | Anti-interference self-adaptive AGC (automatic gain control) adjusting method and device based on smooth filtering |
| CN113839635A (en) * | 2021-09-29 | 2021-12-24 | 四川安迪科技实业有限公司 | Anti-interference self-adaptive AGC (automatic gain control) adjusting method and device based on smooth filtering |
| CN114062192A (en) * | 2021-11-11 | 2022-02-18 | 四川泛华航空仪表电器有限公司 | Frequency-selecting gain conversion circuit and working method thereof |
| CN114094946A (en) * | 2021-11-29 | 2022-02-25 | 中国海洋大学 | Ultra-low noise signal amplification circuit for capacitive marine inert material electrode |
| CN114094946B (en) * | 2021-11-29 | 2024-05-03 | 中国海洋大学 | Ultra-low noise signal amplifying circuit for capacitive marine inert material electrode |
| CN114983424A (en) * | 2022-08-03 | 2022-09-02 | 之江实验室 | Multichannel mixed chopping method and system applied to brain-computer interface chip |
| CN114983424B (en) * | 2022-08-03 | 2022-11-15 | 之江实验室 | Multichannel mixed chopping method and system applied to brain-computer interface chip |
| CN117110650A (en) * | 2023-08-31 | 2023-11-24 | 中国海洋大学 | Acceleration sensor adjusting system capable of adaptively adjusting sensitivity and sensor |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111211751A (en) | Automatic gain digital demodulation chopping amplification method and circuit | |
| CN101199418B (en) | Brain impedance detection circuitry and EEG checking device | |
| CN106877892B (en) | A kind of anti-interference reception circuit structure, method and apparatus | |
| CN104202101B (en) | A kind of shortwave/ultrashort wave instant dynamic spectrum detecting system and method | |
| CN100423693C (en) | Antijamming respiratory wave acquiring method and device | |
| CN101964633B (en) | Lock-in amplifier circuit for detecting terahertz pulse signals | |
| CN105429656B (en) | The signal processing apparatus of demodulation front end is received based on short wave bandwidth | |
| CN104167991B (en) | Variable gain low-noise amplifying circuit and its variable gain method and receiver | |
| CN206602512U (en) | A kind of frequency hopping receives channel fast gain control system | |
| CN109120289A (en) | A kind of short-wave radio frequency front end processing block and method | |
| CN103977503B (en) | A kind of PACE ripple checkout gear of low cost and method | |
| CN109257020A (en) | A kind of experimental circuit can be realized faint amplitude-modulated signal demodulation | |
| CN112649476A (en) | High-precision soil conductivity measuring device and measuring method thereof | |
| CN111856152A (en) | Pulse signal sampling method and device | |
| CN206977429U (en) | It can be seen that light wireless communication physical layer optical frequency demodulator | |
| CN214856805U (en) | Myoelectricity collection system | |
| CN106357352B (en) | Wireless radio frequency modules performance test methods and device | |
| CN215375203U (en) | High-precision soil conductivity measuring device | |
| CN114254670A (en) | Receiving preprocessing circuit of image sonar | |
| CN213846616U (en) | Measuring amplifier for audio signal measurement | |
| CN212514771U (en) | Collection voltage processing device | |
| CN211448668U (en) | Transient field through-casing resistivity logging system receiving circuit | |
| CN103278702B (en) | Extract intelligent detection unit, the method and system of PACE ripple | |
| CN209608637U (en) | Automatic gain control system of superheterodyne receiver suitable for abrupt channel | |
| CN221304580U (en) | Detection device of four-level rod mass spectrometer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20200529 |
|
| RJ01 | Rejection of invention patent application after publication |