Weak photocurrent signal high-precision phase-locked amplification method and system

Abstract

The invention discloses a weak light current signal high-precision lock-in amplification method and system, and relates to the technical field of laser gyroscope frequency stabilization control, and the method comprises the following steps: converting a weak light current generated by a light signal received by a photoelectric detector into a voltage signal, and carrying out differential amplification and blocking processing to extract an AC component; an active filter circuit is adopted to filter and amplify the alternating current signal; the high-speed analog-to-digital conversion circuit samples and converts the signals into digital signals; and then extracting a target signal with known frequency in the MCU by using a digital phase-locked amplification technology, calculating a controlled quantity output by the DAC by combining a frequency stabilization control algorithm, and driving an execution mechanism of the laser gyroscope resonant cavity after conversion by the DAC so as to accurately adjust the length of the resonant cavity and realize accurate control of the cavity length. According to the invention, through an analog-digital combination technology path, the signal-to-noise ratio and the control precision of the signal are effectively improved, the anti-interference capability of the system is obviously enhanced, the hardware structure is simplified, and a reliable solution is provided for realizing high-precision and miniaturized frequency stabilization control of the laser gyroscope.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of frequency stabilization control of laser gyroscopes and inertial navigation, and in particular to a high-precision phase-locked amplification method and system for weak photoelectric current signals. BACKGROUND

[0002] As a core component of inertial measurement assemblies, laser gyroscopes play a key role in inertial navigation systems due to their high stability and reliability. With the continuous improvement of modern military technology and equipment level, higher requirements for high-precision, miniaturization and environmental adaptability of inertial systems are put forward, thereby promoting the development of miniaturized high-precision laser strapdown inertial navigation systems.

[0003] Under the background of the continuous upgrading of weapon systems, the performance indicators of inertial assemblies are increasingly stringent, especially after the popularization and application of "three-self" inertial assemblies with the functions of "self-diagnosis, self-calibration and self-compensation", higher standards are put forward for the size, precision and reliability of laser gyroscopes. The output precision of laser gyroscopes is mainly affected by the frequency stabilization control, machine jitter control and high-voltage power supply control, among which the frequency stabilization control plays a decisive role in system precision.

[0004] Currently, the mainstream frequency stabilization control scheme usually includes the following steps: the photoelectric detector converts the received light signal into a current signal and then into a voltage signal, then filters out the noise through an active filter, then uses analog phase-locked amplification for signal extraction, and finally adjusts the length of the resonant cavity through a hardware control mechanism. However, this traditional method has the following significant defects: 1. The noise suppression capability for weak photoelectric current is limited, making it difficult to achieve pure extraction of effective signals; 2. The overall hardware circuit structure is complex and relies on a large number of analog devices, resulting in high system size and cost; 3. The analog phase-locked loop is easily affected by factors such as temperature drift and device aging, and has insufficient long-term stability and anti-interference capability, making it difficult to meet the needs of modern laser gyroscopes for high precision and reliability. SUMMARY

[0005] In view of the technical problems existing in the prior art, the present application proposes a high-precision phase-locked amplification method and system for weak photoelectric current signals, which significantly simplifies the hardware structure while improving the signal-to-noise ratio and control precision of the system, and enhances the anti-interference performance of the system.

[0006] A high-precision phase-locked amplification method for weak photoelectric current signals, comprising the following steps: S1: The photoelectric detector converts the received light signal into a weak photoelectric current signal; S2: Convert the weak photoelectric current signal into a voltage signal, and perform differential amplification and direct current isolation on the voltage signal to obtain an alternating current signal; S3: filter and amplify the alternating current signal using an active filter circuit to obtain a filtered effective signal; S4: oversample the filtered effective signal through a high-speed analog-to-digital conversion circuit to convert the analog signal into a digital signal; S5: transmit the digital signal to the MCU, and extract the useful signal of a known frequency through digital phase-locked amplification technology in the MCU; S6: based on the useful signal, calculate the required DAC output value through a frequency stabilization control algorithm; S7: convert the DAC output value into an analog control signal through a DAC circuit to drive the actuator of the laser gyroscope resonant cavity to accurately control the resonant cavity length.

[0007] In step S2, the weak photocurrent signal is converted into a voltage signal and subjected to differential amplification and DC blocking processing, which specifically includes: S21: use a differential operational amplifier to differentially amplify the voltage signal output by the photodetector to eliminate power supply noise and external interference and improve the signal-to-noise ratio; S22: remove the DC component in the voltage signal through a DC blocking circuit to retain the alternating current signal as the input of the active filter circuit.

[0008] The active filter amplification uses a band-pass filter circuit, including a low-pass filter circuit and a high-pass filter circuit, for filtering and amplifying the target signal and attenuating the non-target signal.

[0009] The high-speed analog-to-digital conversion circuit uses AD7606C or an ADC chip with equivalent functions and is configured in an oversampling mode to sample the filtered effective signal at high speed and further filter out noise.

[0010] In step S5, digital phase-locked amplification is implemented in the MCU, including: S51: according to the known frequency and phase, perform phase-locked amplification on the digital signal collected by the ADC to extract the useful signal; S52: calculate the current required DAC output value through a frequency stabilization control algorithm to improve control accuracy.

[0011] The DAC output circuit uses an MCU internal DAC or an external DAC chip to convert the digital control signal into an analog voltage signal, which drives the actuator of the laser gyroscope resonant cavity through an amplification circuit to control its deformation.

[0012] The method is applied to a laser gyroscope frequency stabilization control system, and is used in the laser gyroscope frequency stabilization control system to achieve high-precision control, miniaturization, and enhanced anti-interference capability of the laser gyroscope resonant cavity.

[0013] A system for implementing the above method, comprising: A photocurrent-voltage conversion and differential amplification circuit is used to convert the photocurrent signal into a voltage signal and perform differential amplification and DC removal processing; An active filter circuit is used to perform band-pass filter amplification on the voltage signal; A high-speed ADC sampling and conversion circuit is used to oversample the filtered signal and complete analog-digital conversion; An MCU digital phase-locked loop and frequency stabilization control circuit is used to perform phase-locked loop amplification processing on the digital signal and calculate the DAC output value required for frequency stabilization control; A DAC output conversion circuit is used to convert the digital control signal output by the MCU into an analog signal to drive the laser gyroscope resonant cavity actuator.

[0014] The present application has the following beneficial effects: The weak photocurrent signal high-precision phase-locked loop amplification method of the present application converts the photocurrent signal into a voltage signal and performs differential amplification, effectively improving the signal amplitude and suppressing common-mode interference introduced during transmission; the subsequent DC removal processing removes the DC component in the signal, so that the subsequent circuit can focus on amplifying and processing the AC effective signal required for frequency stabilization, thereby laying a foundation for high signal-to-noise ratio at the front end of the signal chain and realizing high signal-to-noise ratio extraction and conversion of the weak photocurrent signal. Active filter amplification of the AC signal can amplify the frequency control signal of the target frequency band while attenuating noise outside the frequency band, thereby achieving preliminary purification of the useful signal and creating conditions for subsequent accurate sampling. Sampling with a high-speed ADC can quickly capture the signal waveform, reduce sampling errors during signal changes, convert the analog signal into a digital signal for subsequent processing, and fundamentally avoid the common problems of temperature drift and noise accumulation in analog signal processing, thereby improving the long-term stability and anti-interference ability of the system. Digital phase-locked loop amplification in the MCU can accurately extract the weak effective signal from the noise according to the known frequency, and its precision and stability far exceed that of an analog phase-locked loop circuit. The DAC output value is calculated through a frequency stabilization control algorithm, thereby realizing the intelligentization and precision of the control process. The control signal is driven by the DAC output to directly adjust the length of the laser gyroscope resonant cavity, and this step together with the aforementioned signal detection and processing links forms a complete closed-loop control system, so that the entire method can maintain the stability of the resonant cavity in real time and accurately, thereby directly improving the output precision of the laser gyroscope. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is the principle block diagram of the weak photocurrent signal high-precision phase-locked loop amplification method embodiment of the present application.

[0016] Figure 2 is the principle block diagram of the photocurrent-voltage conversion circuit in the weak photocurrent signal high-precision phase-locked loop amplification system embodiment of the present application.

[0017] Figure 3 is the digital phase-locked amplification principle block diagram of the weak light current signal high-precision phase-locked amplification system embodiment of the present application.

[0018] Figure 4 is the active filter circuit Multisim simulation circuit of the weak light current signal high-precision phase-locked amplification system embodiment of the present application.

[0019] Figure 5 is the active band-pass filter circuit Multisim simulation result diagram used in the weak light current signal high-precision phase-locked amplification system embodiment of the present application.

[0020] Figure 6 is the MATLAB simulation diagram of the MCU digital phase-locked filter algorithm of the weak light current signal high-precision phase-locked amplification system embodiment of the present application. DETAILED DESCRIPTION

[0021] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0022] As shown in Figure 1 , an embodiment of a weak light current signal high-precision phase-locked amplification method of the present application specifically includes the following steps: S1: The photodetector converts the received light signal into a weak light current signal, and converts the light signal into a corresponding electric current through photoelectric conversion; S2: The weak light current signal is converted into a voltage signal, and the voltage signal is differentially amplified and processed to remove the direct current, so that the subsequent circuit can focus on amplifying and processing the alternating current effective signal required for frequency stabilization, thereby laying a foundation for high signal-to-noise ratio at the front end of the signal chain, and realizing high signal-to-noise ratio extraction and conversion of the weak light current signal.

[0023] S3: The alternating current signal is actively filtered and amplified to obtain the filtered effective signal; the band-pass active filter circuit (including low-pass and high-pass filter units) is used to amplify the target frequency band signal required for resonant cavity frequency stabilization in a targeted manner, and attenuate out-of-band interference noise, thereby preliminarily purifying the effective signal and creating conditions for subsequent accurate sampling.

[0024] S4: oversample the filtered effective signal using a high-speed analog-to-digital conversion circuit to convert the analog signal into a digital signal; in this embodiment, an AD7606C chip or equivalent ADC chip is used for high-speed oversampling analog-to-digital conversion. The oversampling technique can increase the effective resolution of the ADC, reduce quantization noise, and help further filter out high-frequency random noise, resulting in a purer digital signal. This also avoids the common problems of temperature drift and noise accumulation in pure analog processing, improving the long-term stability and anti-interference ability of the system.

[0025] S5: transmit the digital signal to the MCU and perform digital phase-locked amplification in the MCU to extract the useful signal of known frequency; in the MCU, according to the frequency and phase parameters of the known laser frequency stabilization control signal, the digital phase-locked amplification algorithm is used to process the collected digital signal, and the weak target signal component is accurately extracted. Digital phase-locked amplification avoids the influence of component drift and aging of analog phase-locked circuit, and can realize high-precision and repeatable signal extraction.

[0026] S6: based on the extracted useful signal, calculate the current required DAC output value through the frequency stabilization control algorithm to improve the control accuracy; the frequency stabilization control algorithm in the MCU calculates the control amount (DAC output value) for adjusting the length of the resonant cavity according to the signal amplitude and phase information extracted by the phase-locked loop, to ensure the stability of the laser gyroscope output frequency; S7: convert the DAC output value into an analog control signal through a DAC output circuit to drive the actuator of the laser gyroscope resonant cavity and control the resonant cavity length. In this embodiment, the MCU's integrated DAC or external DAC chip can be used to convert the digital control quantity into an analog voltage signal, which is amplified by the subsequent circuit to directly adjust the physical length of the resonant cavity, realizing closed-loop frequency stabilization control. Compared with the traditional scheme, the use of digital phase-locked loop and on-chip DAC significantly reduces the number of peripheral analog devices. At the same time, this step and the aforementioned signal detection and processing links together form a complete closed-loop control system, enabling the entire method to maintain the stability of the resonant cavity in real time and accurately, thereby directly improving the output accuracy of the laser gyroscope and facilitating the miniaturization and long-term reliability of the system.

[0027] In this embodiment, in step S2, the weak photocurrent signal is converted into a voltage signal and subjected to differential amplification and DC isolation processing, which specifically includes: S21: use a differential operational amplifier to differentially amplify the voltage signal output by the phototube to eliminate power supply noise and external interference and improve the signal-to-noise ratio; amplifying the signal through a differential operational amplifier can effectively suppress common-mode noise (such as power supply noise and external electromagnetic interference), thereby significantly improving the signal-to-noise ratio in the initial stage of signal processing.

[0028] S22: Remove the DC component in the voltage signal through the direct current isolation circuit, and retain the AC signal as the input of the active filter circuit. The direct current isolation processing removes the DC component in the signal, so that the subsequent circuit can focus more on amplifying and processing the AC effective signal required for frequency stabilization.

[0029] In this embodiment, the active filter amplification adopts a band-pass filter circuit, including a low-pass filter circuit and a high-pass filter circuit, for filtering and amplifying the target signal and attenuating the non-target signal. The band-pass circuit composed of the low-pass and high-pass filters can selectively allow the frequency stabilization control signal in the target frequency range to pass through and be amplified, while effectively attenuating the out-of-band noise, thereby realizing accurate screening of specific useful signals and laying a foundation for subsequent accurate sampling and control.

[0030] In this embodiment, the high-speed ADC sampling circuit uses an AD7606C chip and is configured in an oversampling mode to sample the filtered effective signal at a high speed and further filter out noise. In other embodiments, an ADC with equivalent functions as the AD7606C chip can also be used. The oversampling technology, in cooperation with subsequent digital processing, can effectively average and filter out high-frequency random noise in the signal; at the same time, the technology improves the effective number of bits of the ADC, reduces quantization noise, and suppresses signal aliasing, thereby obtaining a digital signal with higher quality and purity.

[0031] In this embodiment, in step S5, the digital phase-locked amplification is implemented in the MCU, including: S51: According to the known frequency and phase, the digital signal collected by the ADC is phase-locked amplified to extract the useful signal; by using the digital phase-locked amplification technology, the signal is extracted at the known frequency and phase through a software algorithm, completely avoiding the parameter drift problem caused by element temperature drift and aging in the analog phase-locked circuit, and having extremely high stability and repeatability.

[0032] S52: The current required DAC output value is calculated through the frequency stabilization control algorithm to improve the control accuracy. The flexibility of the MCU software enables the implementation of complex frequency stabilization control algorithms, thereby enabling more accurate calculation of the DAC value required for the control actuator.

[0033] In this embodiment, the DAC output circuit uses the MCU on-chip DAC chip to convert the digital control signal into an analog voltage signal, which drives the actuator of the laser gyroscope resonant cavity through the amplification circuit to control its deformation. By using the digital phase-locked amplification to replace the complex analog phase-locked circuit and using the MCU on-chip integrated DAC, the number of peripheral analog devices is greatly reduced. This directly leads to the reduction of the circuit board area (miniaturization), the reduction of material costs, and the improvement of the overall reliability of the system (due to the reduction of solder joints and external components). In other embodiments, an external DAC chip can also be used, and the external DAC circuit can be simplified.

[0034] The method of the embodiment can be applied to a frequency stabilization control system of a laser gyroscope to realize high-precision, small-size and anti-interference resonant cavity control of the laser gyroscope.

[0035] As shown in Figures 2 to 6 , a system embodiment of the present application for implementing the method of the above embodiment specifically comprises: A photocurrent-voltage conversion and differential amplification circuit is used to convert a photocurrent signal into a voltage signal and perform differential amplification and DC blocking processing; An active filter circuit is used to perform band-pass filtering and amplification on the alternating current signal obtained after differential amplification; A high-speed ADC sampling circuit is used to perform oversampling collection and complete analog-to-digital conversion on the filtered alternating current signal; An MCU digital phase-locked filter circuit is used to perform phase-locked amplification processing on the digital signal and calculate a DAC output value based on a frequency stabilization control algorithm; A DAC output conversion circuit is used to convert the digital control quantity output by the MCU into an analog control signal to drive a resonant cavity actuator.

[0036] In the embodiment, Figure 2 is a photocurrent-voltage conversion circuit schematic diagram of the present application. The weak photocurrent generated by the photodetector is first converted into a voltage signal by a transimpedance amplifier, then high-gain differential amplification is realized and common-mode noise is suppressed by a differential operational amplifier, and then the DC component is filtered out by a DC blocking / AC coupling network, and only the alternating current effective signal related to the frequency stabilization modulation is output, providing a high signal-to-noise ratio input for the subsequent active band-pass filtering and high-speed ADC sampling.

[0037] In the embodiment Figure 3 is a digital phase-locked amplification working principle block diagram. The filtered weak photocurrent signal is input into the MCU through high-speed ADC sampling, the MCU generates a sine / cosine reference signal consistent with the frequency stabilization modulation frequency, and after being multiplied by the sampling signal, the in-phase and quadrature components are extracted through digital low-pass filtering, and then the signal amplitude or the frequency stabilization error signal is calculated and input into the frequency stabilization control algorithm to obtain the DAC output control quantity, and the laser gyroscope resonant cavity length is adjusted through the DAC and the driving circuit to complete the closed-loop frequency stabilization control.

[0038] Based on the technical solution of the embodiment, an active filter circuit Multisim simulation circuit (as shown in Figure 4 ) is established, and an active band-pass filter circuit Multisim simulation result diagram (as shown in Figure 5 ) is obtained. Through Figure 5The curve (the red curve is the input noise signal, and the pink curve is the effective signal after the active filter circuit) shows that the active filter circuit composed of the low-pass and high-pass can filter the noise signal in the signal well, thereby realizing the hardware filtering of the circuit and laying a good foundation for subsequent phase-locked loop filtering and amplification.

[0039] Based on the technical solutions of the embodiment, Figure 6 The MATLAB simulation result diagram of the MCU digital phase-locked amplification algorithm of the application is shown from top to bottom as follows: an ideal frequency stabilization signal, a sampling signal after noise is added, a sine / cosine reference signal generated in the MCU, a product waveform after the sampling signal is multiplied by the reference signal, and in-phase and quadrature components after digital low-pass filtering, and the amplitude output obtained by synthesizing the two components at the bottom. As shown in the diagram, in the strong noise background, the amplitude curve can still stably approach the amplitude change of the ideal signal, verifying that the digital phase-locked amplification method has significant signal-to-noise ratio improvement and stable extraction capability for weak photoelectric current signals.

[0040] The application realizes the core effect of extracting the weak photoelectric current signal with high precision from the strong noise by setting the photoelectric current to voltage signal circuit, the active filter circuit, the high-speed ADC sampling circuit, the MCU digital phase-locked filter circuit and the DAC output circuit, which have a synergistic effect, and through digital phase-locked loop and closed-loop control, the overall performance of the laser gyroscope frequency stabilization control system is greatly improved, including output precision, anti-interference capability, miniaturization degree, cost and reliability.

[0041] The above is only the preferred embodiment of the application and is not used to limit the application, and for those skilled in the art, the application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A high-precision lock-in amplification method for weak photocurrent signals, characterized in that, Includes the following steps: S1: The photodetector converts the received optical signal into a weak photocurrent signal; S2: Convert the weak photocurrent signal into a voltage signal, and perform differential amplification and DC blocking on the voltage signal to obtain an AC signal; S3: Use an active filter circuit to filter and amplify the AC signal to obtain the filtered effective signal; S4: The filtered effective signal is oversampled by a high-speed analog-to-digital converter circuit to convert the analog signal into a digital signal; S5: Transmit the digital signal to the MCU, where the MCU uses digital lock-in amplification technology to extract the useful signal of known frequency; S6: Calculate the required DAC output value based on the useful signal using a frequency stabilization control algorithm; S7: The DAC output value is converted into an analog control signal through the DAC circuit to drive the actuator of the laser gyroscope resonant cavity, so as to precisely control the cavity length.

2. The method according to claim 1, characterized in that, In step S2, the weak photocurrent signal is converted into a voltage signal and subjected to differential amplification and DC blocking, specifically including: S21: A differential operational amplifier is used to differentially amplify the voltage signal output by the photodetector in order to eliminate power supply noise and external interference and improve the signal-to-noise ratio; S22: The DC component in the voltage signal is removed by the DC blocking circuit, and the AC signal is retained as the input of the active filter circuit.

3. The method according to claim 1, characterized in that, The active filtering amplification employs a bandpass filter circuit, including a low-pass filter circuit and a high-pass filter circuit, to filter and amplify the target signal and attenuate non-target signals.

4. The method according to claim 1, characterized in that, The high-speed analog-to-digital conversion circuit uses an AD7606C or an equivalent ADC chip and is configured in oversampling mode to sample the filtered effective signal at high speed and further filter out noise.

5. The method according to claim 1, characterized in that, In step S5, the digital lock-in amplification is implemented in the MCU, including: S51: Based on the known frequency and phase, the digital signal acquired by the ADC is amplified by phase lock-in to extract the useful signal; S52: Calculates the required DAC output value through a frequency stabilization control algorithm to improve control accuracy.

6. The method according to claim 1, characterized in that, The DAC output circuit uses an on-chip DAC of the MCU or an external DAC chip to convert digital control signals into analog voltage signals, which are then amplified to drive the actuator of the laser gyroscope resonant cavity and control its deformation.

7. The method according to claim 1, characterized in that, The method is applied to a laser gyroscope frequency stabilization control system to achieve high-precision control, miniaturization, and enhanced anti-interference capability of the laser gyroscope resonant cavity.

8. A system for implementing the method of any one of claims 1-7, characterized in that, include: The photocurrent-to-voltage conversion and differential amplifier circuit is used to convert the photocurrent signal into a voltage signal and perform differential amplification and DC blocking. An active filter circuit is used to perform bandpass filtering and amplification of voltage signals; A high-speed ADC sampling and conversion circuit is used to oversample the filtered signal and complete the analog-to-digital conversion. The MCU digital phase-locked loop and frequency stabilization control circuit is used to perform phase-locked amplification of digital signals and calculate the DAC output value required for frequency stabilization control; The DAC output conversion circuit is used to convert the digital control signal output by the MCU into an analog signal to drive the laser gyroscope resonant cavity actuator.

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