Digital multi-channel nonlinear online correction circuit and method

Abstract

The invention discloses a digital multi-channel nonlinear online correction circuit and method. The digital multi-channel nonlinear online correction circuit comprises a signal bias conditioning module, a high-speed AD conversion module and a digital signal processing module. The correction method comprises the steps of obtaining an energy spectrum accumulation result of an input pulse signal and performing normalization processing, then obtaining a channel address imax where pemax with the maximum incident particle energy distribution probability is located through an energy spectrum peak searching algorithm, and setting the DAC conversion circuit by taking a pulse signal amplitude corresponding to the channel address as a digital quantity for direct current bias adjustment. Correspondingly adding imax to the energy spectrum acquisition threshold value, and repeating the steps until the amplitude corresponding to the energy spectrum peak value of the input pulse signal exceeds the full scale amplitude of the sampling ADC; and then each sampling channel address of the ADC is corrected, and a result is output. According to the invention, by adjusting the DC bias voltage of the pulse signal, the nonlinear correction parameter of each sampling channel address of the ADC is obtained through online calculation, and the precision of digital multi-channel sampling measurement is improved.

Description

Technical Field

[0001] The invention relates to the field of nuclear measurement, and in particular to a digital multi-channel nonlinear online correction circuit and method. Background Art

[0002] Digital multichannel is one of the most commonly used measuring devices in nuclear detection, and the nonlinear performance of the multichannel is a key factor affecting the measurement accuracy. Usually, a device such as a sliding pulse signal source can be used as the input signal of the digital multichannel to obtain the nonlinear correction parameters of the multichannel. However, in many applications, such as the PGNAA online measurement and analysis device, the digital multichannel is a measuring component integrated in the device, and it is impossible to use an external pulse signal source to provide a suitable input signal for the multichannel to obtain the nonlinear correction parameters. Therefore, it is necessary to improve the existing digital multichannel and establish a method that can correct the nonlinearity online. Summary of the invention

[0003] The purpose of the present invention is to provide a digital multi-channel nonlinear online correction circuit and method. In an environment where an external pulse signal source cannot provide a suitable input signal for multiple channels, the nonlinear correction parameters of each sampling channel address of ADC are obtained by online calculation by adjusting the DC bias voltage of the actual measured pulse signal, thereby improving the accuracy of digital multi-channel sampling measurement.

[0004] In order to achieve the above object, the technical solution of the present invention is:

[0005] A digital multi-channel nonlinear online correction circuit, comprising:

[0006] A signal bias conditioning module adjusts the DC bias voltage of the input pulse signal;

[0007] The high-speed AD conversion module is connected to the signal bias conditioning module, and continuously digitally samples the pulse signal adjusted by the signal bias conditioning module and outputs it after digital sampling;

[0008] The digital signal processing module is connected to the high-speed AD conversion module to process the digital signal output by the high-speed AD conversion module according to a preset program; and is connected to the signal bias conditioning module to output the DC bias adjustment digital quantity and the reference voltage selection digital quantity to the signal bias conditioning module.

[0009] As an improvement to the above technical solution, the signal bias conditioning module includes:

[0010] The DAC conversion circuit converts the DC bias adjustment digital quantity output by the digital signal processing module into a corresponding analog voltage value, and outputs it to the selection end of the reference voltage selection circuit;

[0011] A reference voltage selection circuit, wherein the selection end includes an input end 1 and an input end 2, wherein the input end 1 is connected to the output end of the DAC conversion circuit, and the input end 2 is connected to the ADC sampling reference level output end of the high-speed AD conversion module; the analog voltage value output by the DAC conversion circuit and the level VCM output by the ADC sampling reference level output end are selected, and the selected reference bias voltage is transmitted to the single-ended to differential amplifier circuit;

[0012] A single-ended to differential amplifier circuit converts the DC bias adjustment digital quantity output by the digital signal processing module into a corresponding analog voltage value, and outputs it to the selection end of the reference voltage selection circuit;

[0013] The DAC conversion circuit, the reference voltage selection circuit, and the single-ended to differential amplifier circuit are cascaded.

[0014] As an improvement to the above technical solution, the single-ended to differential amplifier circuit includes an operational amplifier, a load resistor R1, an isolation resistor R2, feedback resistors R3 and R5, and a balancing resistor R4; the input pulse signal is connected to the in-phase input terminal of the operational amplifier after passing through the isolation resistor R2, the feedback resistor R3 is connected in parallel between the in-phase input terminal and the reverse output terminal of the operational amplifier, the balancing resistor R4 is connected between the inverting input terminal and the ground of the operational amplifier, and the feedback resistor R5 is connected in parallel between the inverting input terminal and the in-phase output terminal of the operational amplifier; the output common-mode voltage setting terminal of the operational amplifier is connected to the output terminal of the reference voltage selection circuit; the signal amplification factor is adjusted by synchronously adjusting the ratio of the feedback resistor R3 and the isolation resistor R2, and the feedback resistor R5 and the balancing resistor R4, so as to convert the single-ended input pulse signal into a differential signal and output it to the high-speed AD conversion module.

[0015] As an improvement to the above technical solution, the high-speed AD conversion module includes an ADC sampling reference level VCM output terminal, which is connected to the input terminal 2 of the reference voltage selection circuit, and the ADC sampling reference level VCM is input to the reference voltage selection circuit from the input terminal 2 of the reference voltage selection circuit.

[0016] As an improvement to the above technical solution, the digital signal processing module includes a DC bias adjustment digital output terminal and a reference voltage selection digital output terminal, which are respectively connected to the input terminal of the DAC conversion circuit and the input terminal 2 of the reference voltage selection circuit.

[0017] As an improvement to the above technical solution, the present invention provides an online correction method based on the above digital multi-channel nonlinear online correction circuit, the steps of the method are:

[0018] Step S1: setting the reference voltage selection digital quantity to the input terminal 1 voltage output, and setting the DC bias adjustment digital quantity output by the digital signal processing module to 0.

[0019] Step S2: Obtain the energy spectrum accumulation result of the input pulse signal, and normalize the accumulated energy spectrum according to the total value. The normalized counting result of each channel c i It is expressed as:

[0020] c i =tw i *pe j ,∑tw i =1,∑pe j =1

[0021] Where i is the channel address corresponding to the ADC conversion, tw i is the actual track width value corresponding to each transformed track address after normalization, pe j is the distribution probability of the incident particle energy corresponding to the corresponding pulse amplitude;

[0022] Step S3: obtaining the channel address imax where the incident particle energy distribution probability pemax is the largest through the energy spectrum peak search algorithm, and using the pulse signal amplitude corresponding to the channel address as the digital value for DC bias adjustment to set the DAC conversion circuit, that is, synchronously increasing the sampling value after AD conversion by imax;

[0023] Step S4: increasing the threshold of energy spectrum acquisition by imax accordingly, and repeating steps S2 and S3 until the amplitude corresponding to the peak value of the energy spectrum of the input pulse signal exceeds the full-scale amplitude of the sampling ADC;

[0024] Step S5: In the normalized counting result cik obtained by measurement, the track width tw i It is only related to the ADC sampling channel address i, and the amplitude distribution probability pe of the pulse signal energy spectrum j It is related to the DC bias adjustment digital quantity, from which the channel width tw corresponding to the ADC sampling channel address i can be calculated i The distribution value of ADC sampling channel correction coefficient is:

[0025]

[0026] Step S6: Set the reference voltage selection digital quantity output by the digital signal processing module as the voltage output of input terminal 2; when the energy spectrum accumulation is completed, the accumulated result of each sampling channel address is multiplied by the correction coefficient of the corresponding channel address to obtain the corrected output result.

[0027] The working principle of the present invention is:

[0028] The high-speed AD conversion module is used to digitally sample the pulse signal output by the digital signal processing module, output the sampled digital quantity to the digital signal processing module, and output the ADC sampling reference level VCM to the signal bias conditioning module.

[0029] The steps of the online correction method of the circuit are: step S1: setting the reference voltage selection digital quantity to the input terminal 1 voltage output, and setting the DC bias adjustment digital quantity output by the digital signal processing module to 0; step S2: obtaining the energy spectrum accumulation result of the input pulse signal, and normalizing the accumulated energy spectrum according to the total value, and the normalized counting result of each channel c i Expressed as: c i =tw i *pe j ,∑tw i =1,∑pe j =1, where i is the channel address corresponding to the ADC conversion, tw i is the actual track width value corresponding to each transformed track address after normalization, pe j is the distribution probability of the incident particle energy corresponding to the corresponding pulse amplitude; step S3: obtain the channel address imax1 where the incident particle energy distribution probability pemax is the largest through the energy spectrum peak search algorithm, and use the channel address amplitude as the digital quantity for DC bias adjustment to set the DAC conversion circuit, that is, the sampling value after AD conversion is synchronously increased by imax1; step S4: increase the threshold of energy spectrum acquisition by imax1 accordingly, and repeat steps S2 and S3 until the input pulse signal energy spectrum traverses the full-scale amplitude of the sampling ADC; step S5: step S5: in the measured normalized counting result cik, the channel width tw i It is only related to the ADC sampling channel address i, and the amplitude distribution probability pe of the pulse signal energy spectrum j It is related to the DC bias adjustment digital quantity, from which the channel width tw corresponding to the ADC sampling channel address i can be calculated i The distribution value of ADC sampling channel correction coefficient is: Step S6: Set the reference voltage selection digital quantity output by the digital signal processing module as the voltage output of input terminal 2; when the energy spectrum accumulation is completed, the accumulated result of each sampling channel address is multiplied by the correction coefficient of the corresponding channel address to obtain the corrected output result.

[0030] Compared with the prior art, the present invention has the following advantages and positive effects:

[0031] The present invention obtains the nonlinear correction parameters of each sampling channel of ADC by online calculation by adjusting the DC bias voltage of the pulse signal, thereby improving the accuracy of digital multi-channel sampling measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 A schematic diagram of a circuit of the present invention;

[0034] Figure 2 is a schematic diagram of a signal bias conditioning module of the present invention;

[0035] Figure 3 A schematic diagram of a high-speed AD conversion circuit of the present invention;

[0036] Figure 4 A schematic diagram of the process of adjusting the DC bias of the present invention;

[0037] Figure 5 It is a flow chart of the nonlinear online correction method of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work, any modifications, equivalent substitutions, improvements, etc., should be included in the protection scope of the present invention.

[0039] like Figure 1 The figure shows a schematic diagram of a digital multi-channel nonlinear online correction circuit of the present invention. The digital multi-channel nonlinear online correction circuit of the present invention mainly comprises: a signal bias conditioning module, a high-speed AD conversion module, and a digital signal processing module.

[0040] like Figure 2The figure shows a schematic diagram of a signal bias conditioning module. The signal bias conditioning module is composed of a cascaded DAC conversion circuit, a reference voltage selection circuit, and a single-ended to differential amplifier circuit. The pulse signal of the single-ended input passes through the resistor R2 and then enters the non-inverting input terminal of the operational amplifier, and together with the resistor R3 connected between the non-inverting input terminal and the inverting output terminal of the operational amplifier, the resistor R5 connected between the inverting input terminal and the non-inverting output terminal of the operational amplifier, and the resistor R4 connected between the inverting input terminal and the ground of the operational amplifier, they constitute a single-ended to differential amplifier circuit to convert the input single-ended signal into a differential signal output; the load resistor R1 is connected between the input pulse signal and the ground as a matching resistor to prevent the input pulse signal from being transmitted; the DC bias adjustment digital output of the digital signal processing module The quantity is directly connected to the input of a 14-bit high-precision DA converter, and the analog voltage output of the high-precision DA converter is connected to input terminal 1 of the reference voltage selection circuit; the VCM signal output by the AD conversion module is connected to input terminal 2 of the reference voltage selection circuit; the reference voltage selection digital quantity output by the digital signal processing module controls the output selection of the reference voltage level selection circuit; the output terminal of the reference voltage selection circuit is connected to the common-mode level output setting terminal of the single-ended to differential operational amplifier; the amplification factor of the circuit is adjusted by synchronously adjusting the ratio of R3 to R2, and R5 to R4.

[0041] like Figure 3 As shown, it is a schematic diagram of a high-speed AD conversion module. The high-speed AD conversion module is composed of a 12-bit parallel high-speed AD converter. The differential pulse signal output by the signal bias conditioning module is connected to the AD converter via a filter circuit. In the filter circuit, resistor R6 is connected between the in-phase output terminal of the digital signal processing module and the positive input terminal of the AD converter, resistor R7 is connected between the inverting output terminal of the digital signal processing module and the negative input terminal of the AD converter, and capacitor C1 is connected between the positive and negative input terminals of the AD converter. The full-scale amplitude of the high-speed AD converter input pulse signal is ±1V, the sampling rate is 500M per second, and 12-bit parallel differential data output. The signal output terminal of the high-speed AD converter is connected to the digital signal processing module, and the data is sent to the digital signal processing module for digital processing.

[0042] like Figure 4 and 5 As shown, an embodiment of the present invention further provides an online correction method based on the above-mentioned digital multi-channel nonlinear online correction circuit. The above-mentioned digital multi-channel nonlinear online correction circuit implements the online correction method of the present invention.

[0043] The online correction method comprises the following steps:

[0044] Step S1: setting the reference voltage selection digital quantity to the input terminal 1 voltage output, and setting the DC bias adjustment digital quantity output by the digital signal processing module to 0.

[0045] Step S2: Obtain the energy spectrum accumulation result of the input pulse signal, and normalize the accumulated energy spectrum according to the total value. The normalized counting result of each channel c i It is expressed as:

[0046] c i =tw i *pe j ,∑tw i =1,∑pe j =1

[0047] Where i is the channel address corresponding to the ADC conversion, tw i is the actual track width value corresponding to each transformed track address after normalization, pe j is the distribution probability of the incident particle energy corresponding to the corresponding pulse amplitude;

[0048] Step S3: obtaining the channel address imax where the incident particle energy distribution probability pemax is the largest through the energy spectrum peak search algorithm, and using the pulse signal amplitude corresponding to the channel address as the digital value for DC bias adjustment to set the DAC conversion circuit, that is, synchronously increasing the sampling value after AD conversion by imax;

[0049] Step S4: Increase the threshold of energy spectrum acquisition by imax accordingly, and repeat steps S2 and S3 until the amplitude corresponding to the peak value of the energy spectrum of the input pulse signal exceeds the full-scale amplitude of the sampling ADC.

[0050] In order to more clearly explain the principle of DC bias adjustment, the following is only a simple example. The other adjustment situations are similar and will not be repeated here. When the DC bias is adjusted to 0, the peak channel address of the normalized distribution of the input pulse signal energy spectrum measured is 834, and the corresponding pulse signal amplitude is 204mV. Then, the DC bias adjustment digital quantity is set to 204, 408, 612, and 816, respectively, that is, when the DAC output voltage is 204mV, 408mV, 612mV, and 816mV, respectively, the input pulse signal energy spectrum is measured; when the DC bias voltage is set to 816mV, the pulse signal amplitude corresponding to the peak of the energy spectrum is measured to be 1.02V, which exceeds the full-scale range of ADC conversion of 1V, and the steps are repeated to terminate; the five groups of energy spectrum accumulation results are calculated to obtain the normalized counting results ci1, ci2, ci3, ci4, and ci5 corresponding to each channel address.

[0051] Step S5: In the normalized counting result cik obtained by measurement, the track width tw i It is only related to the ADC sampling channel address i, and the amplitude distribution probability pe of the pulse signal energy spectrum j It is related to the DC bias adjustment digital quantity, from which the channel width tw corresponding to the ADC sampling channel address i can be calculatedi The distribution value of ADC sampling channel correction coefficient is:

[0052]

[0053] Step S6: Set the reference voltage selection digital quantity output by the digital signal processing module as the voltage output of input terminal 2; when the energy spectrum accumulation is completed, the accumulated result of each sampling channel address is multiplied by the correction coefficient of the corresponding channel address to obtain the corrected output result.

[0054] In summary, the embodiments of the present invention provide a digital multi-channel nonlinear online correction circuit and method. Compared with the prior art, the method can adjust the DC bias voltage of the actual measured pulse signal in an environment where an external pulse signal source cannot provide a suitable input signal for multiple channels, and online calculate the nonlinear correction parameters of each sampling channel address of the ADC, thereby improving the accuracy of digital multi-channel sampling measurement.

[0055] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the circuit can be divided into different functional modules to complete all or part of the functions described above.

Claims

1. A digital multi-channel nonlinear online correction circuit, characterized in that: include: A signal bias conditioning module adjusts the DC bias voltage of the input pulse signal; The high-speed AD conversion module is connected to the signal bias conditioning module, and continuously digitally samples the pulse signal adjusted by the signal bias conditioning module and outputs it after digital sampling; The digital signal processing module is connected to the high-speed AD conversion module to process the digital signal output by the high-speed AD conversion module according to a preset program; and is connected to the signal bias conditioning module to output the DC bias adjustment digital quantity and the reference voltage selection digital quantity to the signal bias conditioning module.

2. The digital multi-channel nonlinear online correction circuit according to claim 1, characterized in that: The signal bias conditioning module comprises: The DAC conversion circuit converts the DC bias adjustment digital quantity output by the digital signal processing module into a corresponding analog voltage value, and outputs it to the selection end of the reference voltage selection circuit; A reference voltage selection circuit, wherein the selection end includes an input end 1 and an input end 2, wherein the input end 1 is connected to the output end of the DAC conversion circuit, and the input end 2 is connected to the ADC sampling reference level output end of the high-speed AD conversion module; the analog voltage value output by the DAC conversion circuit and the level VCM output by the ADC sampling reference level output end are selected, and the selected reference bias voltage is transmitted to the single-ended to differential amplifier circuit; The single-ended to differential amplifier circuit converts the DC bias adjustment digital quantity output by the digital signal processing module into a corresponding analog voltage value, and outputs it to the selection end of the reference voltage selection circuit; The DAC conversion circuit, the reference voltage selection circuit, and the single-ended to differential amplifier circuit are cascaded.

3. The digital multi-channel nonlinear online correction circuit as claimed in claim 2, characterized in that: The single-ended to differential amplifier circuit includes an operational amplifier, a load resistor R1, an isolation resistor R2, feedback resistors R3 and R5, and a balancing resistor R4; the input pulse signal is connected to the in-phase input terminal of the operational amplifier after passing through the isolation resistor R2, the feedback resistor R3 is connected in parallel between the in-phase input terminal and the reverse output terminal of the operational amplifier, the balancing resistor R4 is connected between the reverse input terminal and the ground of the operational amplifier, and the feedback resistor R5 is connected in parallel between the reverse input terminal and the in-phase output terminal of the operational amplifier; the output common-mode voltage setting terminal of the operational amplifier is connected to the output terminal of the reference voltage selection circuit; the signal amplification factor is adjusted by synchronously adjusting the ratio of the feedback resistor R3 and the isolation resistor R2, and the feedback resistor R5 and the balancing resistor R4, and the pulse signal input at the single end is converted into a differential signal and output to the high-speed AD conversion module.

4. The digital multi-channel nonlinear online correction circuit as claimed in claim 2, characterized in that: The high-speed AD conversion module includes an ADC sampling reference level VCM output terminal connected to the input terminal 2 of the reference voltage selection circuit, and the ADC sampling reference level VCM is input to the reference voltage selection circuit from the input terminal 2 of the reference voltage selection circuit.

5. The digital multi-channel nonlinear online correction circuit as claimed in claim 2, characterized in that: The digital signal processing module comprises a DC bias adjustment digital quantity output terminal and a reference voltage selection digital quantity output terminal, which are respectively connected to the input terminal of the DAC conversion circuit and the input terminal 2 of the reference voltage selection circuit.

6. An on-line correction method for a digital multi-channel nonlinear on-line correction circuit according to any one of claims 2 to 5, characterized in that: The steps of this method are: S1: Set the reference voltage selection digital quantity to the input terminal 1 voltage output, and set the DC bias adjustment digital quantity output by the digital signal processing module to 0. S2: Obtain the accumulated energy spectrum of the input pulse signal, and normalize the accumulated energy spectrum according to the total value. The normalized counting result of each channel c i It is expressed as: c i =tw i *pe j ,∑tw i =1,∑pe j =1 Where i is the channel address corresponding to the ADC conversion, tw i is the actual track width value corresponding to each transformed track address after normalization, pe j is the distribution probability of the incident particle energy corresponding to the corresponding pulse amplitude; S3: Obtain the channel address imax where the incident particle energy distribution probability pemax is the largest through the energy spectrum peak search algorithm, and use the pulse signal amplitude corresponding to the channel address as the digital value for DC bias adjustment to set the DAC conversion circuit, that is, to synchronously increase the sampling value after AD conversion by imax; S4: Increase the threshold of energy spectrum acquisition by imax accordingly, and repeat steps S2 and S3 until the amplitude corresponding to the peak value of the energy spectrum of the input pulse signal exceeds the full-scale amplitude of the sampling ADC; S5: After each change of the DC bias adjustment digital quantity to set the DAC conversion circuit, the normalized count result ci is measured, and the track width tw i It is only related to the ADC sampling channel address i, and the amplitude distribution probability pe of the pulse signal energy spectrum j It is related to the DC bias adjustment digital quantity, from which the channel width tw corresponding to the ADC sampling channel address i can be calculated i The distribution value of ADC sampling channel correction coefficient is: Step S6: Set the reference voltage selection digital quantity output by the digital signal processing module as the voltage output of input terminal 2; when the energy spectrum accumulation is completed, the accumulated result of each sampling channel address is multiplied by the correction coefficient of the corresponding channel address to obtain the corrected output result.

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