Data processing circuit for four-quadrant detector
By adding multiple signal acquisition and adaptive Kalman filtering algorithm processing in the hardware of the four-quadrant detector, the problems of signal inaccuracy and noise interference are solved, and the positioning accuracy and stability of laser communication are improved.
Patent Information
- Application Number
- CN202323435519.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-15
- Publication Date
- 2024-12-20
- Estimated Expiration
- 2033-12-15
AI Technical Summary
In laser communication, four-quadrant detectors have signal inaccuracy problems caused by electrical noise, optical noise, processing technology, material deviation and temperature. Especially under the high-precision positioning requirements of the 1550nm band, traditional circuits cannot effectively solve the static Error and noise interference.
Add temperature signals, ground signals, floating signals and reference voltage signals to the hardware, and use adaptive Kalman filtering algorithm to perform signal processing in the software, reducing static errors and noise interference through differential compensation and filtering techniques.
It effectively reduces the static error caused by the unevenness of the four channels, improves the accuracy and stability of the signal, enhances the compensation ability for environmental and temperature changes, and improves the positioning accuracy and anti-interference ability of the system.
Smart Images
Figure CN222215738U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of photoelectric communication circuits, in particular to a data processing circuit for a four-quadrant detector. Background Art
[0002] With the development of space technology, the demand and application of satellite laser communication technology are growing. The basic principle of satellite laser communication is to use laser as a carrier, through free space and the atmosphere as a carrier, to achieve efficient and fast data transmission. Satellite laser communication system has a series of advantages such as wide bandwidth, high transmission speed, high safety performance, small equipment size, light weight, low system power consumption, etc., and has gradually become an emerging development industry.
[0003] The focus of satellite laser communication research is the pointing, acquisition, and tracking (PAT: Pointing Acquisition Tracking) technology, which is one of the main technologies in satellite laser communication technology. Basically, all satellite laser communication system terminals use PAT technology to capture and track the light spot. In the implementation of capture and tracking, it is necessary to rely on position detection components combined with the light spot positioning algorithm to solve the light spot position. Commonly used position detection components include position sensitive detectors (PSD: Position Sensitive Device), charge coupled detectors (CCD: Charge-Coupled Device), quadrant detectors (QD), etc.
[0004] With the development of optical fiber technology, the 800nm band used in traditional satellite laser communication systems has developed towards the 1550nm band laser light source, which has stronger penetration and is less affected by atmospheric turbulence. Traditional PSD devices have low spot detection accuracy, extremely poor linearity at the edges, and low spatial resolution, which has gradually failed to meet the high positioning accuracy requirements of long-distance space laser communications. The charge-coupled detector (CCD) detector has poor photoelectric conversion capabilities in the 1550nm band, and high-frame-rate CCD cameras are expensive, and their processing circuits are complex and the output signals are discontinuous.
[0005] Compared with traditional PSD and CCD detectors, the four-quadrant detector has higher responsiveness, detection sensitivity and spatial resolution, and its processing circuit is relatively simple. The four-quadrant detector has gradually become an important precision tracking detector in PAT technology.
[0006] As a photoelectric conversion device, the four-quadrant detector has a photoelectric conversion module, a cross-group amplifier circuit, an operational amplifier circuit, an analog / digital conversion circuit, and an SPI communication module. In actual use, it is inevitable that electrical noise, optical noise, processing technology, material deviation, temperature, etc. will cause inaccurate signal collection. Utility Model Content
[0007] The purpose of this utility model is to solve the interference problem existing in laser communication data processing. Through circuit optimization, four additional acquisition signals are added to the hardware, and these four signals are fully applied to perform additional signal processing in the software, and then the adaptive Kalman filter algorithm is used for state estimation. To achieve the above purpose, the utility model adopts the following technical solutions:
[0008] A data processing circuit for a four-quadrant detector comprises a four-quadrant detector, and also comprises an amplifying circuit, a low-pass filter, an analog / digital converter, and a main control core connected to the four-quadrant detector in sequence. The current output analog signals of the four quadrants of the four-quadrant detector after photoelectric conversion are transmitted to the amplifying circuit, the low-pass filter, and the analog / digital converter in sequence. The analog / digital converter is respectively provided with a temperature signal acquisition circuit, a ground signal acquisition circuit, a floating signal acquisition circuit, and a reference voltage signal acquisition circuit. The temperature signal acquisition circuit, the ground signal acquisition circuit, the floating signal acquisition circuit, and the reference voltage signal acquisition circuit respectively transmit corresponding analog signals to the analog / digital converter, and the analog / digital converter converts each channel of analog signal information into a digital signal and transmits it to the main control core for data processing.
[0009] Furthermore, the amplifier circuit and the low-pass filter are connected to form a signal amplification and filtering circuit, and the four current output analog signals of the four quadrants of the four-quadrant detector after photoelectric conversion are respectively transmitted to the analog / digital converter through the four-channel signal amplification and filtering circuit, and the internal circuit structure of the four-channel signal amplification and filtering circuit is consistent.
[0010] Further, the signal amplification and filtering circuit includes a first resistor R1, a first capacitor C1, and a second resistor R2. The first output end of the four-quadrant detector is connected in series with the first resistor R1, the first capacitor C1, and the second resistor R2 in sequence and then connected to the ground end. The two ends of the first capacitor C1 are respectively connected in parallel with the analog signal access pin AIN-0P and the ground pin AIN-0GND of the analog / digital converter;
[0011] By analogy, the second output end of the four-quadrant detector is connected in series with the third resistor R3, the second capacitor C2, and the fourth resistor R4 in sequence, and then connected to the ground end, and the two ends of the second capacitor C2 are respectively connected in parallel with the analog signal access pin AIN-1P of the analog / digital converter and the ground pin AIN-1GND;
[0012] The third output terminal of the four-quadrant detector is connected in series with the fifth resistor R5, the third capacitor C3, and the sixth resistor R6 in sequence, and then connected to the ground terminal, and the two ends of the third capacitor C3 are respectively connected in parallel with the analog signal access pin AIN-2P of the analog / digital converter and the ground pin AIN-2GND;
[0013] The fourth output end of the four-quadrant detector is connected in series with the seventh resistor R7, the fourth capacitor C4, and the eighth resistor R8 in sequence and then connected to the ground end. The two ends of the fourth capacitor C4 are respectively connected in parallel with the analog signal access pin AIN-3P of the analog / digital converter and the ground pin AIN-3GND.
[0014] Furthermore, the temperature signal acquisition circuit includes a temperature sensor TMP and a signal amplification and filtering circuit, and the temperature signal acquired by the temperature sensor TMP is transmitted to the analog / digital converter through the signal amplification and filtering circuit.
[0015] Furthermore, the ground signal acquisition circuit is a ground terminal, the ground terminal of the ground signal acquisition circuit is connected to the analog signal access pin AIN-5P of the analog / digital converter, the ground pin AIN-5GND of the analog / digital converter is grounded, and the analog / digital converter collects the ground signal through the analog signal access pin AIN-5P.
[0016] Furthermore, the reference voltage signal acquisition circuit includes a reference voltage input terminal and a signal amplification and filtering circuit, and the reference voltage input terminal acquired by the reference voltage input terminal is transmitted to the analog / digital converter through the signal amplification and filtering circuit.
[0017] Furthermore, the floating signal acquisition circuit is a circuit in which the analog signal access pin AIN-7P of the analog / digital converter is suspended, and the analog / digital converter acquires the floating signal through the analog signal access pin AIN-7P.
[0018] Furthermore, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 of the signal amplification and filtering circuit are all 49.9R resistors; the capacity of the first capacitor C1, the second capacitor C2, the third capacitor C3, and the fourth capacitor C4 is 0.22uf.
[0019] The positive progress of the utility model is that the solution adds four additional acquisition signals in hardware, fully applies these four signals in software for additional signal processing, and develops a matching adaptive Kalman filter algorithm. Compared with the traditional four-quadrant detector that only collects four optical signals, this solution not only uses the traditional low-pass filter in hardware design, but also adds four additional signals, namely temperature signal, ground signal, floating signal and reference voltage signal. By introducing the temperature signal, ground signal, floating signal and reference voltage signal, the difference compensation of the data is increased to solve the static error problem caused by the unevenness of the four channels. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 The utility model is a circuit concept diagram of a data processing circuit for a four-quadrant detector.
[0021] Figure 2 The utility model is a circuit diagram of a data processing circuit for a four-quadrant detector.
[0022] Figure 3 The utility model is a circuit application flow chart of a data processing circuit for a four-quadrant detector. DETAILED DESCRIPTION
[0023] The present invention will be described more clearly and completely below by way of embodiments in conjunction with the accompanying drawings, but the present invention is not limited to the scope of the embodiments.
[0024] like Figure 1-3 As shown, the present scheme is a data processing circuit for a four-quadrant detector, including a four-quadrant detector, and also including an amplifier circuit, a low-pass filter, an analog / digital converter, and a main control core connected to the four-quadrant detector in sequence. The current output analog signals of the four quadrants of the four-quadrant detector after photoelectric conversion are transmitted to the amplifier circuit, the low-pass filter, and the analog / digital converter in sequence. The analog / digital converter is respectively provided with a temperature signal acquisition circuit, a ground signal acquisition circuit, a floating signal acquisition circuit, and a reference voltage signal acquisition circuit. The temperature signal acquisition circuit, the ground signal acquisition circuit, the floating signal acquisition circuit, and the reference voltage signal acquisition circuit respectively transmit the corresponding analog signals to the analog / digital converter, and the analog / digital converter converts the analog signal information of each channel into a digital signal and transmits it to the main control core for data processing.
[0025] Furthermore, the amplifier circuit and the low-pass filter are connected to form a signal amplification and filtering circuit, and the four current output analog signals of the four quadrants of the four-quadrant detector after photoelectric conversion are respectively transmitted to the analog / digital converter through the four-channel signal amplification and filtering circuit, and the internal circuit structure of the four-channel signal amplification and filtering circuit is consistent.
[0026] Further, the signal amplification and filtering circuit includes a first resistor R1, a first capacitor C1, and a second resistor R2. The first output end of the four-quadrant detector is connected in series with the first resistor R1, the first capacitor C1, and the second resistor R2 in sequence and then connected to the ground end. The two ends of the first capacitor C1 are respectively connected in parallel with the analog signal access pin AIN-0P and the ground pin AIN-0GND of the analog / digital converter;
[0027] By analogy, the second output end of the four-quadrant detector is connected in series with the third resistor R3, the second capacitor C2, and the fourth resistor R4 in sequence, and then connected to the ground end, and the two ends of the second capacitor C2 are respectively connected in parallel with the analog signal access pin AIN-1P of the analog / digital converter and the ground pin AIN-1GND;
[0028] The third output terminal of the four-quadrant detector is connected in series with the fifth resistor R5, the third capacitor C3, and the sixth resistor R6 in sequence, and then connected to the ground terminal, and the two ends of the third capacitor C3 are respectively connected in parallel with the analog signal access pin AIN-2P of the analog / digital converter and the ground pin AIN-2GND;
[0029] The fourth output end of the four-quadrant detector is connected in series with the seventh resistor R7, the fourth capacitor C4, and the eighth resistor R8 in sequence and then connected to the ground end. The two ends of the fourth capacitor C4 are respectively connected in parallel with the analog signal access pin AIN-3P of the analog / digital converter and the ground pin AIN-3GND.
[0030] Furthermore, the temperature signal acquisition circuit includes a temperature sensor TMP and a signal amplification and filtering circuit, and the temperature signal acquired by the temperature sensor TMP is transmitted to the analog / digital converter through the signal amplification and filtering circuit.
[0031] Furthermore, the ground signal acquisition circuit is a ground terminal, the ground terminal of the ground signal acquisition circuit is connected to the analog signal access pin AIN-5P of the analog / digital converter, the ground pin AIN-5GND of the analog / digital converter is grounded, and the analog / digital converter collects the ground signal through the analog signal access pin AIN-5P.
[0032] Furthermore, the reference voltage signal acquisition circuit includes a reference voltage input terminal and a signal amplification and filtering circuit, and the reference voltage input terminal acquired by the reference voltage input terminal is transmitted to the analog / digital converter through the signal amplification and filtering circuit.
[0033] Furthermore, the floating signal acquisition circuit is a circuit in which the analog signal access pin AIN-7P of the analog / digital converter is suspended, and the analog / digital converter acquires the floating signal through the analog signal access pin AIN-7P.
[0034] Furthermore, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 of the signal amplification and filtering circuit are all 49.9R resistors; the capacity of the first capacitor C1, the second capacitor C2, the third capacitor C3, and the fourth capacitor C4 is 0.22uf.
[0035] Basic working principle of the circuit:
[0036] This solution is to add four additional acquisition signals in hardware, make full use of these four signals in software for additional signal processing, and develop a matching adaptive Kalman filter algorithm.
[0037] Compared with the traditional four-quadrant detector that only collects four optical signals, the hardware design of the utility model not only uses the traditional low-pass filter, but also adds four additional signals, namely temperature signal, ground signal, floating signal and reference voltage signal.
[0038] like Figure 1 As shown, access pins AIN_0P, AIN_1P, AIN_2P, and AIN_3P are connected to four effective optical / electrical signals, access pin AIN_4P is connected to a temperature signal, access pin AIN_5P is connected to a ground signal, access pin AIN_6P is connected to a reference voltage signal, and access pin AIN_7P is connected to a floating signal.
[0039] In software processing:
[0040] In order to solve the static error problem caused by the unevenness of the four channels, the static error is manifested as the channel values of the four quadrants are not equal to each other due to differences in the devices, wiring, dark current, etc. of the four-way amplifier circuit when there is no effective light entering the four-quadrant detector. The solution is that after each power-on and before receiving the effective signal, the software will use the averaging method to eliminate the static error through multiple sampling.
[0041] Selectively compensate for laboratory ambient light. Although the four-quadrant detector made of InGaAs material has the best photoelectric conversion efficiency in the 1550nm band, it cannot completely shield light in other bands, such as fluorescent lamps in the laboratory. Therefore, the utility model adds an option for users to choose to compensate for additional ambient light. The solution is to collect the ambient light signal after power-on and before the effective signal light is turned on, and calculate the difference with the reference collection value when there is no light, and compensate for the difference. This step needs to be repeated when the ambient light changes. The comparison before and after compensation is shown in the figure, which is the comparison of the initial sampling values of the four quadrants and the comparison of the sampling values after static error compensation.
[0042] Ground signal compensation. In the absence of interference, since the ground signal is collected by the access pin AIN_5P, its theoretical value should always remain at 0. When interference occurs, the ground signal will have a certain small amplitude jump, and the sampling signal based on this ground signal will also have the same amplitude jump. Each collected signal value will be calculated with the ground signal connected to the pin AIN_5P for difference.
[0043] Temperature reminder. Changes in ambient temperature will not only affect the values of electronic components such as resistors and capacitors, but also the conversion coefficient of the four-quadrant detector photoelectric conversion device. For example, the conversion coefficient is 0.95A / W at room temperature of 25°, which is a variable affected by temperature changes. In actual applications, there are strict requirements for temperature control. The access pin AIN_4P will collect temperature in real time through the on-chip temperature sensor TMP. The layout position of the temperature sensor TMP should be close to the photoelectric conversion module.
[0044] Whether used in a ground laboratory or a satellite terminal, when the temperature acquisition signal exceeds the required range, an alarm prompt is required, and parameters such as the photoelectric conversion coefficient must be corrected and compensated in real time according to the current temperature. The correction value and compensation value can be calculated based on actual tests.
[0045] Power supply fluctuation prompt. When there is a power supply system circuit failure or the voltage source is unstable, the four-quadrant detector should be able to detect the fluctuation or jump of the voltage source in real time, report the working fault in time, and confirm whether it is necessary to enter the standby state to avoid damage caused by power supply fluctuations.
[0046] The solution is to access pin AIN_6P to sample the reference voltage 1.25V processed by the hardware voltage stabilization circuit in real time. When undervoltage or overvoltage occurs at the power supply end, the reference voltage value will jump to confirm the stability of the power supply system.
[0047] Adaptive Kalman filter. Compared with modern filters such as FIR or IIR, the classic Kalman filter is more suitable for processing signals with high bandwidth requirements and variable frequencies. The operation of the Kalman filter is more like a recursive operator. Its characteristics are that it requires a more accurate mathematical model and has two parameters, process excitation noise covariance (Q) and measurement noise covariance (R), to assist the recursive operation. In the classic Kalman filter, Q and R are two fixed parameter values. Its operation logic is that the optimal estimate at the current moment is calculated by the optimal estimate at the previous moment and the sampled value at this moment, and Q and R jointly calculate the optimal estimated parameter value. Simply put, by changing the size of Q and R values, the Kalman filter model can be more inclined to trust the estimated value or the sampled value. When in static sampling mode, since the optical signal power and light angle remain unchanged, the size of the four-quadrant detector sampling value should also remain fixed. The fluctuations are mainly due to noise and electromagnetic interference. At this time, the use of classic Kalman filtering can play a good filtering role on the signal, but it cannot cover the dynamic state well. As shown in the static sampling and dynamic jump figure, the fluctuation range of the Kalman prediction value is only half of the actual sampling value, which plays a good filtering role. However, when the optical power undergoes a small mutation, the Kalman prediction value needs some time to follow the change of the up-sampling value.
[0048] However, in actual application, sampling must be in dynamic mode, and the optical power and angle change in an unpredictable state, and the sampling value of the four-quadrant detector changes accordingly. In this state, the four-quadrant detector needs to be able to determine whether the change in the sampling value is caused by the optical power, the deflection of the optical angle, or external interference, so an adaptive Kalman filter is proposed here to take into account both static and dynamic sampling modes. At this time, the access pin AIN_7P of the four-quadrant detector is suspended to collect floating signals, which will participate in auxiliary judgment. Since the access pin AIN_7P is suspended, it is not affected by the optical power and the deflection angle. When the sampling value of the access pin 7 jumps, it is mainly due to external electromagnetic interference or wire conduction. The interference causes the signal to jump and fluctuate. At this time, the sampling values of the photoelectric conversion circuits of the access pins AIN_0P, AIN_1P, AIN_2P, and AIN_3P will also jump in the same way. When the interference fluctuation is sensed, the four-quadrant detector will modify Q and R in real time according to the fluctuation size, so that the filtering strategy is more confident in the predicted value and avoids serious noise interference.
[0049] When the sampling value of the access pin AIN_7P is stable, the photoelectric signals of the access pins AIN_0P, AIN_1P, AIN_2P, and AIN_3P change. If the access pins AIN_0P, AIN_1P, AIN_2P, and AIN_3P show the same increasing or decreasing trend, it can be judged that the optical power has changed. If two of the access pins AIN_0P, AIN_1P, AIN_2P, and AIN_3P increase while the other two decrease, it is judged that the light angle has deflected. In the above two cases, the Kalman filter needs to have a stronger tracking capability. At this time, modify the parameters Q and R to make the filtering strategy more trustful of the sampling value to ensure good dynamic response capability.
[0050] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that this is only for illustration and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.
Claims
1. A data processing circuit for a four-quadrant detector, comprising a four-quadrant detector, characterized in that: It also includes an amplifier circuit, a low-pass filter, an analog / digital converter, and a main control core that are sequentially connected to the four-quadrant detector. The current output analog signals of the four quadrants of the four-quadrant detector after photoelectric conversion are sequentially transmitted to the amplifier circuit, the low-pass filter, and the analog / digital converter. The analog / digital converter is respectively provided with a temperature signal acquisition circuit, a ground signal acquisition circuit, a floating signal acquisition circuit, and a reference voltage signal acquisition circuit. The temperature signal acquisition circuit, the ground signal acquisition circuit, the floating signal acquisition circuit, and the reference voltage signal acquisition circuit respectively transmit the corresponding analog signals to the analog / digital converter, and the analog / digital converter converts the analog signal information of each channel into digital signals and transmits them to the main control core for data processing.
2. A data processing circuit for a four-quadrant detector as claimed in claim 1, characterized in that: The amplifier circuit and the low-pass filter are connected to form a signal amplification and filtering circuit. The four current output analog signals of the four quadrants of the four-quadrant detector after photoelectric conversion are respectively transmitted to the analog / digital converter through the four-channel signal amplification and filtering circuit. The internal circuit structure of the four-channel signal amplification and filtering circuit is consistent.
3. A data processing circuit for a four-quadrant detector as claimed in claim 2, characterized in that: The signal amplification and filtering circuit comprises a first resistor R1, a first capacitor C1, and a second resistor R2. The first output end of the four-quadrant detector is connected in series with the first resistor R1, the first capacitor C1, and the second resistor R2 in sequence and then connected to the ground end. The two ends of the first capacitor C1 are respectively connected in parallel with the analog signal access pin AIN-0P and the ground pin AIN-0GND of the analog / digital converter; By analogy, the second output end of the four-quadrant detector is connected in series with the third resistor R3, the second capacitor C2, and the fourth resistor R4 in sequence, and then connected to the ground end, and the two ends of the second capacitor C2 are respectively connected in parallel with the analog signal access pin AIN-1P of the analog / digital converter and the ground pin AIN-1GND; The third output terminal of the four-quadrant detector is connected in series with the fifth resistor R5, the third capacitor C3, and the sixth resistor R6 in sequence, and then connected to the ground terminal, and the two ends of the third capacitor C3 are respectively connected in parallel with the analog signal access pin AIN-2P of the analog / digital converter and the ground pin AIN-2GND; The fourth output end of the four-quadrant detector is connected in series with the seventh resistor R7, the fourth capacitor C4, and the eighth resistor R8 in sequence and then connected to the ground end. The two ends of the fourth capacitor C4 are respectively connected in parallel with the analog signal access pin AIN-3P of the analog / digital converter and the ground pin AIN-3GND.
4. A data processing circuit for a four-quadrant detector as claimed in claim 3, characterized in that: The temperature signal acquisition circuit comprises a temperature sensor TMP and a signal amplifying and filtering circuit. The temperature signal acquired by the temperature sensor TMP is transmitted to an analog / digital converter through the signal amplifying and filtering circuit.
5. A data processing circuit for a four-quadrant detector as claimed in claim 3, characterized in that: The ground signal acquisition circuit is a ground terminal, the ground terminal of the ground signal acquisition circuit is connected to the analog signal access pin AIN-5P of the analog / digital converter, the ground pin AIN-5GND of the analog / digital converter is grounded, and the analog / digital converter collects the ground signal through the analog signal access pin AIN-5P.
6. A data processing circuit for a four-quadrant detector as claimed in claim 3, characterized in that: The reference voltage signal acquisition circuit comprises a reference voltage input terminal and a signal amplification and filtering circuit. The reference voltage signal acquired by the reference voltage input terminal is transmitted to the analog / digital converter through the signal amplification and filtering circuit.
7. A data processing circuit for a four-quadrant detector as claimed in claim 3, characterized in that: The floating signal acquisition circuit is a circuit in which the analog signal access pin AIN-7P of the analog / digital converter is suspended, and the analog / digital converter acquires the floating signal through the analog signal access pin AIN-7P.
8. A data processing circuit for a four-quadrant detector as claimed in claim 3, characterized in that: The first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7 and the eighth resistor R8 of the signal amplification and filtering circuit are all 49.9R resistors; the capacity of the first capacitor C1, the second capacitor C2, the third capacitor C3 and the fourth capacitor C4 is 0.22uf.