阅读说明：本技术 一种天文观测系统中可扩展动态范围的增益自适应变换电路及方法 (Gain self-adaptive conversion circuit and method capable of expanding dynamic range in astronomical observation system ) 是由 张健 许哲 赵燕 李爱玲 于 2020-05-19 设计创作，主要内容包括：本发明提供了一种天文观测系统中可扩展动态范围的增益自适应变换电路及方法。该电路包括可变增益运算放大电路、迟滞比较电路、AD转换器和FPGA,其中,原始输入信号同时接入可变增益运算放大电路和迟滞比较电路；所述迟滞比较电路将原始输入信号与设定的阈值电压比较,根据比较结果输出高电平/低电平；所述可变增益运算放大电路根据迟滞比较电路的输出选择对应的增益档对原始输入信号进行调理,并输出至AD变换器；所述FPGA同时接收被AD转换器量化的数字式信号和迟滞比较电路的输出,合成数字化的目标信号。本发明使用一路放大电路、AD转换器及一路迟滞比较电路就实现了电路动态范围的扩展,成本较低,电路结构简明,通用性强。(The invention provides a gain self-adaptive conversion circuit and a method capable of expanding a dynamic range in an astronomical observation system. The circuit comprises a variable gain operational amplifier circuit, a hysteresis comparison circuit, an AD converter and an FPGA, wherein an original input signal is simultaneously accessed into the variable gain operational amplifier circuit and the hysteresis comparison circuit; the hysteresis comparison circuit compares an original input signal with a set threshold voltage and outputs a high level/a low level according to a comparison result; the variable gain operational amplification circuit selects a corresponding gain gear according to the output of the hysteresis comparison circuit to condition the original input signal and outputs the conditioned gain gear to the AD converter; the FPGA receives the digital signal quantized by the AD converter and the output of the hysteresis comparison circuit at the same time, and synthesizes a digitized target signal. The invention uses an amplifying circuit, an AD converter and a hysteresis comparison circuit to realize the expansion of the dynamic range of the circuit, and has the advantages of low cost, simple circuit structure and strong universality.)

1. A gain self-adaptive transformation method capable of expanding dynamic range in an astronomical observation system is characterized by comprising the following steps: the method comprises the following steps:

1) conditioning the amplified signal: for the signal output by the observation system sensor, an operational amplifier circuit is used for conditioning the signal, so that the dynamic range of the signal is adapted to the input dynamic range of the AD converter at the next stage;

2) determining input signal amplitude range: comparing the signal output by the sensor of the observation system with a set threshold value, and correspondingly outputting a high level/a low level according to the comparison result;

3) adjusting the gain of the operational amplifier circuit: configuring corresponding high gain/low gain coefficients for the operational amplification circuit according to the high level/low level;

4) quantizing the input signal: digitizing the signal output by the operational amplifier circuit through the AD converter;

5) data processing: receiving the digitized signal output by the AD converter in the step 4), and correcting the signal by referring to the high level/low level output in the step 2) to obtain a digitized target signal.

2. The method of adaptive gain transformation for extended dynamic range in an astronomical observation system of claim 1, wherein: a hysteresis comparison circuit is adopted in the step 2), different signal levels are output according to the signal amplitude output by the sensor of the observation system, and the signal amplitude is recorded as V_signalThe high and low threshold levels of the hysteresis comparator are respectively V_high、V_lowIf V is_signal>V_highIf yes, the output of the hysteresis comparison circuit is at a low level; if V_signal<V_lowIf yes, the output of the hysteresis comparison circuit is at a high level; if V_low<V_signal<V_highThe hysteresis comparison circuit remains in the previous state.

3. The method of adaptive gain transformation for extended dynamic range in an astronomical observation system of claim 1, wherein: in the step 3), different negative end input resistors are selected by triggering the change-over switch, so that different gain coefficients are configured for the operational amplification circuit.

4. The method for adaptive gain conversion with extended dynamic range in an astronomical observation system according to claim 2, wherein the signal is modified in step 5) with reference to the high/low level output in step 2), specifically: if the high level output in the step 2) corresponds to the high gain of the operational amplifier circuit, the digital signal output by the AD converter is increased by one highest bit of '0'; if the output of step 2) is low level, corresponding to low gain of the operational amplifier circuit, an offset value is added to the digitized signal output by the AD converter.

5. The adaptive gain transform method for scalable dynamic range in astronomical observation system of claim 4, wherein the offset value isWherein

6. A gain adaptive conversion circuit capable of adjusting dynamic range in an astronomical observation system is characterized in that: the device comprises a variable gain operational amplification circuit, a hysteresis comparison circuit, an AD converter and an FPGA, wherein an original input signal is simultaneously accessed into the variable gain operational amplification circuit and the hysteresis comparison circuit; the hysteresis comparison circuit compares an original input signal with a set threshold voltage and outputs a high level/a low level according to a comparison result; the variable gain operational amplification circuit selects a corresponding gain gear according to the output of the hysteresis comparison circuit to condition the original input signal and outputs the conditioned gain gear to the AD converter; the FPGA receives the digital signal quantized by the AD converter and the output of the hysteresis comparison circuit at the same time, and synthesizes a digitized target signal.

7. The adaptive gain transform circuit for adjusting dynamic range in an astronomical observation system according to claim 6, wherein: the hysteresis comparison circuit comprises a voltage comparator, a resistor R1 and a resistor R2; the variable gain amplifying circuit comprises an operational amplifier, a multi-way selection switch, a resistor R3, a resistor R4 and a resistor R5; the original input signal is simultaneously connected to the positive input end of the operational amplifier and the negative input end of the voltage comparator; one end of the resistor R1 is connected with a reference level V_refThe other end of the comparator is connected with the positive input end of the comparator; two ends of the resistor R2 are respectively connected with the positive input end and the output end of the voltage comparator; the output end of the hysteresis comparison circuit is respectively connected to the control end of the multi-path selection switch and the first input end of the FPGA; two ends of the resistor R3 are respectively connected to the inverting input end and the output end of the operational amplifier; the single port of the multi-path selection switch is connected to the reverse output end of the operational amplifier, the multi-port is respectively connected with one ends of the resistor R4 and the resistor R5, and the other ends of the resistor R4 and the resistor R5 are grounded; the signal input end of the AD converter is connected with the output end of the operational amplifier, the control end of the AD converter receives a control signal sent by the FPGA, and the data output end of the AD converter is connected with the second input end of the FPGA.

8. The adaptive gain transform circuit for adjusting dynamic range in an astronomical observation system according to claim 7, wherein: the high and low threshold levels set by the hysteresis comparison circuit are respectively V_high、V_lowThe high and low levels of the output are respectively V_OH0, then reference level

Technical Field

The invention relates to a gain conversion circuit and a method capable of expanding a dynamic range in an astronomical observation system.

Background

In current scientific research of astronomical observation, some stars with very weak brightness (for example, 16 stars and the like) are often observed, and a large number of stars with relatively strong brightness (for example, 5 stars and the like) exist in an observation field, which means that an observation system needs to have a very high dynamic range to ensure that the low-brightness stars which can be observed, and the high-brightness stars which are acquired at the same time cannot be saturated. In this case, on the one hand, sensors with high dynamic range are required to convert the light signals emitted by the stars with different brightness levels into corresponding electrical signals, and on the other hand, back-end processing circuits are required to process these signals with very large dynamic range and perform quantization processing.

In highly dynamic astronomical observation systems, the dynamic range is essentially determined by the sensors selected by the system: the read-out noise of the sensor determines the lower limit of the detection capability to a certain extent (for example, 16 stars and the like), and because the read-out frequency of the sensor has large correlation with the read-out noise, the read-out frequency of the system is set to be relatively low; the full well of the sensor determines the upper limit of detection capability (e.g., 5 equi-stars). According to the star-and-wait calculation method (each star-and-wait difference represents a brightness difference of 2.512 times), the dynamic range of a detection system capable of simultaneously detecting 16 stars and 5 stars is 25131-88 dB. In order to achieve a sufficient performance of the high dynamic sensor, the back-end processing circuit has a corresponding dynamic range, in particular an AD converter. In general, the dynamic range of an AD converter is determined by the number of quantization bits thereof (6.02N dB, N being the number of quantization bits). It can be calculated that for the above detection system the required number of AD quantization bits is at least 15-bit.

With the development of scientific technology, a lot of AD converters with high quantization bits exist at present, but in combination with the requirements of a detection system, there may not be too many choices, and in consideration of factors such as cost, a circuit with high and low gains matched with simultaneous quantization is developed at present, as shown in fig. 1, a1 and a2 respectively represent two conditioning amplifiers, so that AD conversion with high quantization bits can be realized by using 2 AD converters with low quantization bits, and two paths of quantized data are finally fused at an FPGA, so as to finally improve the dynamic range of a processing circuit.

The method can better adapt the dynamic range of the circuit to the dynamic range of the sensor in design, but has certain defects that two paths of AD devices are needed to realize the dynamic range (the dynamic range is expensive), and meanwhile, the two paths of circuits have certain difference from a conditioning amplifier to the AD and bring certain deviation inevitably in image fusion.

Disclosure of Invention

The invention provides a gain self-adaptive transformation method and a gain self-adaptive transformation circuit capable of expanding a dynamic range in an astronomical observation system, which realize the function of improving the dynamic range, have lower cost and reduce the fixed deviation caused by hard circuit difference.

In order to achieve the above purpose, the invention provides the following technical scheme:

a gain self-adaptive transformation method capable of expanding dynamic range in an astronomical observation system is characterized in that: the method comprises the following steps:

1) conditioning the amplified signal: for the signal output by the observation system sensor, an operational amplifier circuit is used for conditioning the signal, so that the dynamic range of the signal is adapted to the input dynamic range of the AD converter at the next stage;

2) determining input signal amplitude range: comparing the signal output by the sensor of the observation system with a set threshold value, and correspondingly outputting a high level/a low level according to the comparison result;

3) adjusting the gain of the operational amplifier circuit: configuring corresponding high gain/low gain coefficients for the operational amplification circuit according to the high level/low level;

4) quantizing the input signal: digitizing the signal output by the operational amplifier circuit through the AD converter;

5) data processing: receiving the digitized signal output by the AD converter in the step 4), and correcting the signal by referring to the high level/low level output in the step 2) to obtain a digitized target signal.

Further, a hysteresis comparison circuit is adopted in the step 2), different signal levels are output according to the signal amplitude output by the sensor of the observation system, and the signal amplitude is recorded as V_signalThe high and low threshold levels of the hysteresis comparator are respectively V_high、V_lowIf V is_signal>V_highIf yes, the output of the hysteresis comparison circuit is at a low level; if V_signal<V_lowIf yes, the output of the hysteresis comparison circuit is at a high level; if V_low<V_signal<V_highThe hysteresis comparison circuit remains in the previous state.

Further, in step 3), different negative terminal input resistors are selected by triggering the switch, so as to configure different gain coefficients for the operational amplifier circuit.

Further, in step 5), the signal is corrected with reference to the high level/low level output in step 2), specifically: if the high level output in the step 2) corresponds to the high gain of the operational amplifier circuit, the digital signal output by the AD converter is increased by one highest bit of '0'; if the output of step 2) is low level, corresponding to low gain of the operational amplifier circuit, an offset value is added to the digitized signal output by the AD converter.

Further, the offset value isWhereinRatio of gain factor, V, of high gain to low gain_highThe high threshold level of the hysteresis comparison circuit.

The invention also provides a gain self-adaptive conversion circuit capable of adjusting the dynamic range in the astronomical observation system, which is characterized in that: the system comprises a variable gain operational amplifier circuit, a hysteresis comparison circuit, an AD converter and an FPGA, wherein an original input signal (a signal output by an observation system sensor) is simultaneously accessed into the variable gain operational amplifier circuit and the hysteresis comparison circuit; the hysteresis comparison circuit compares an original input signal with a set threshold voltage and outputs a high level/a low level according to a comparison result; the variable gain operational amplification circuit selects a corresponding gain gear according to the output of the hysteresis comparison circuit to condition the original input signal and outputs the conditioned gain gear to the AD converter; the FPGA receives the digital signal quantized by the AD converter and the output of the hysteresis comparison circuit at the same time, and synthesizes a digitized target signal.

Further, the hysteresis comparison circuit comprises a voltage comparator, a resistor R1 and a resistor R2; the variable gain amplifying circuit comprises an operational amplifier, a multi-way selection switch, a resistor R3, a resistor R4 and a resistor R5; the original input signal is simultaneously connected to the positive input end of the operational amplifier and the negative input end of the voltage comparator; one end of the resistor R1 is connected with a reference level V_refThe other end of the comparator is connected with the positive input end of the comparator; two ends of the resistor R2 are respectively connected with the positive input end and the output end of the voltage comparator; the output end of the hysteresis comparison circuit is respectively connected to the control end of the multi-path selection switch and the first input end of the FPGA; two ends of the resistor R3 are respectively connected to the inverting input end and the output end of the operational amplifier; the single port of the multi-path selection switch is connected to the reverse output end of the operational amplifier, the multi-port is respectively connected with one ends of the resistor R4 and the resistor R5, and the other ends of the resistor R4 and the resistor R5 are grounded; the signal input end of the AD converter is connected with the output end of the operational amplifier, the control end of the AD converter receives a control signal sent by the FPGA, and the data output end of the AD converter is connected with the second input end of the FPGA.

Furthermore, the hysteresis comparison circuit is set to have high and low threshold levels V respectively_high、V_lowThe high and low levels of the output are respectively V_OH0, then reference level

The invention has the advantages that:

1. the invention uses one path of amplifying circuit, AD converter and one path of hysteresis comparison circuit to realize the expansion of the dynamic range of the circuit, compared with two paths of parallel processing circuits, the cost is lower, and simultaneously the circuit structure is simple and clear, and the universality is strong.

2. The invention uses one signal conditioning circuit to process signals, and compared with two parallel processing circuits, the invention has no deviation caused by difference between the circuits.

3. The hysteresis comparator pre-value level can be set according to actual conditions, and the hysteresis comparator pre-value level setting method has high flexibility.

Drawings

Fig. 1 shows a conventional two-path high-low gain low-bit quantization AD conversion synthesis high-bit quantization principle.

Fig. 2 is a schematic circuit diagram of the present invention.

Fig. 3 is a schematic diagram of a dual gain of a variable gain amplifier circuit.

FIG. 4 is a timing diagram of the signal processing input signal and the AD conversion driving clock of the hysteresis comparator and the operational amplifier.

Fig. 5 shows the gain curve of the circuit system after data synthesis.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

In order to be able to acquire optical signals emitted by extremely weak stars and the like, the current astronomical observation system usually needs longer exposure time, and simultaneously reduces pixel reading frequency to reduce noise of a reading circuit of a sensor. In the process of one-time imaging, high-brightness stars and low-brightness stars enter a field of view at the same time, which means that signals output by the sensor are in extremely weak and extremely strong states at the same time. For the output signal of the sensor corresponding to the star with extremely weak brightness, in order to obtain higher signal strength, the signal is usually amplified before the AD conversion, so that the AD converter can fully quantize the signal, and the final quantization result can really reflect the star information. For a high-brightness star, the amplitude of the corresponding signal output by the sensor is larger, and at the moment, the amplitude of the signal is adjusted to be matched with the input range of the AD converter.

Based on the above, the method for gain adaptive transformation with expandable dynamic range in an astronomical observation system provided by the present invention comprises the following steps:

(1) signal conditioning using operational amplifier circuitry: the signal output by the sensor of the observation system is conditioned by the operational amplifier circuit with variable gain based on the operational amplifier, so that the dynamic range of the signal is adapted to the input dynamic range of the AD converter. The variable gain operational amplifier circuit consists of an operational amplifier, a multi-path selection switch and a resistance network. The multi-path selection switch selects different paths, and the operational amplifier circuit is in a high gain state or a low gain state.

(2) Determining input signal amplitude range: signal V output by sensor of observation system_signalInputting a hysteresis comparator (the high and low threshold levels of the hysteresis comparator are respectively V)_high、V_low) If V is_signal>V_highIf so, the output of the hysteresis comparator is low level (0); if V_signal<V_lowIf so, the output of the hysteresis comparator is at a high level (1); if V_low<V_signal<V_highThe hysteresis comparator holds the previous state.

(3) Adjusting the gain of the operational amplifier circuit: (2) the output of the hysteresis comparator is connected to the control port of the multiplexer in (1), and if the output of the hysteresis comparator is '1', the operational amplification circuit in (1) has high gain; if the hysteresis comparator output is "0", the operational amplification circuit in (1) exhibits a low gain.

(4) Quantizing the input signal: the back end of the operational amplification circuit in (1) is an AD conversion chip, and the signal output by the operational amplification circuit is digitized. Since the multiplexer needs a certain time for switching and the operational amplifier needs a certain time for gain conversion to be stable, the position of the AD conversion driving clock should be adjusted to make the switching point of each signal unit located in the section where the signal is stable.

(5) Data processing: an FPGA chip receives the output high and low levels of the hysteresis comparator in the step (2) and the AD output digitized signal in the step (4), and if the output of the hysteresis comparator is '1', which means that the operational amplifier circuit in the step (1) is in a high-gain state, the AD output digital signal is increased by one highest bit of '0'; if the hysteresis comparator outputs "0", meaning that the operational amplifier circuit in (1) is in a low gain state, the AD output digital signal is increased by an offset value.

The invention also provides a gain self-adaptive conversion circuit capable of expanding the dynamic range in an astronomical observation system, which comprises a variable gain operational amplification circuit, a hysteresis voltage comparison circuit, an AD converter and an FPGA which are sequentially connected, wherein an original input signal is simultaneously input to the variable gain operational amplification circuit and the hysteresis comparison circuit; the hysteresis comparison circuit compares an input signal with a preset voltage and outputs high and low levels according to the comparison condition; the variable gain operational amplification circuit selects a corresponding gain gear according to the output condition of the hysteresis comparison circuit to condition the original input signal and outputs the signal to the AD converter; the FPGA receives the signal quantized by the AD converter and the output of the hysteresis comparator at the same time, and increases the quantized original input value by one highest bit of 0 or adds an offset value, which is determined by the output of the hysteresis comparator.

The variable gain operational amplifier circuit comprises a low noise operational amplifier, a multi-way selection switch, a resistor R3, a resistor R4 and a resistor R5. The positive input end of the operational amplifier is connected with the output of the signal sensor, and two ends of the resistor R3 are respectively connected to the negative input end and the output end of the operational amplifier; the single port of the multi-path selection switch is connected to the inverted output end of the operational amplifier, the multi-port is respectively connected with one end of the resistor R4 and one end of the resistor R5, the other ends of the resistor R4 and the resistor R5 are grounded, and the output of the operational amplifier is connected with the input end of the AD converter. When the multiplexer gates connection R4, the circuit gain is a1 ═ 1+ R4/R3; when the multiplexer gates connection R5, the circuit gain is a2 ═ 1+ R5/R3. It is assumed here that R4< R5, i.e. a1 is low gain and a2 is high gain.

The hysteresis comparator is composed of a general voltage comparator, a resistor R1 and a resistor 2. The reverse input end of the comparator is connected with the output end of the sensor, and one end of the resistor R1 is connected with the reference level V_refThe other end of the resistor R2 is connected with the positive input end of the comparator, the two ends of the resistor R2 are respectively connected with the positive input end and the output end of the comparator, and the output end of the comparator is connected with the control end of the multiplexer in the variable gain operational amplification circuit and the FPGA.

If the output high and low potentials of the hysteresis comparator are V respectively_OH0, the comparator input reference voltage is V_refThe upper threshold voltage can be obtainedIs composed of

Lower threshold voltage of

Reasonable resistors R1 and R2 are arranged to enable the return difference voltage of the hysteresis comparatorThe noise is slightly larger than the circuit noise, and the jump of the circuit gain caused by the noise in the process of one-time AD conversion is prevented.

The following takes the case where the output signal of the sensor is lower than the lower threshold level of the hysteresis comparator, higher than the upper threshold level of the hysteresis comparator, and between the upper and lower threshold levels of the hysteresis comparator as an example, and the flow of processing the signal in the present invention is specifically described.

Suppose the sensor output signal is at most V_{O_max}The input range of the AD converter is 0-V_{AD_full}In order to fully utilize the full range of AD, the output of two gain loops of the variable gain amplifying circuit can reach 0-V_{AD_full}As shown in fig. 3.

Suppose the hysteresis comparator output is V_OHWhen the gain of the variable gain amplifying circuit is selected to be high gain A2; when the hysteresis comparator output is 0, the gain of the variable gain amplifier circuit is selected to be a low gain a 1. If all sensor output signals are to be effectively quantized by the AD converter, the gain conversion point of the variable gain amplifier circuit should reach V at the high gain loop output_{AD_full}Before (as shown in fig. 5), in the hysteresis comparator, V should be reflected in consideration of the loop gain_high≤V_{AD_full}/A₂. After the gain conversion point is defined, the reference voltage of the hysteresis comparison circuit can be determined

When the input signal is lower than the lower threshold level V of the hysteresis comparator circuit_lowThe output of the hysteresis comparator is V_OHThe signal controls the variableA multiplexer in the gain amplifying circuit, which makes the circuit select a high-gain A2 path; when the input signal is higher than the threshold level V on the hysteresis comparison circuit_highWhen the output of the hysteresis comparator is 0, the signal controls a multiplexer in the variable gain amplifying circuit to enable the circuit to select a low gain A1 path; when the input signal is near the gain transition point and between the upper and lower threshold levels of the hysteresis comparator circuit, the hysteresis comparator circuit characteristic will ensure that its output maintains the previous state, and then the gain of the variable gain amplifier circuit will also maintain the previous state, and the return voltage Δ V ═ V_high-V_LowIt is possible to prevent an error from occurring due to a change in the circuit gain caused by noise fluctuation at the time of AD conversion. Since the circuit noise is very low, V_high≈V_lowAnd errors caused by the back difference voltage delta V can be ignored in the later data processing process.

Since a certain time is required for each gain conversion of the variable gain amplifier circuit to be stable, the sampling clock of the AD converter should be placed in the second half of each signal, as shown in fig. 4. Considering that the signal rate of an astronomical observation system is low, the AD sampling point can always fall in a stable interval of the signal.

After the input signal is converted by the AD converter, the digitized signal is output to the FPGA, and meanwhile, the FPGA receives a signal sent by the hysteresis comparator. If the signal of the hysteresis comparator is received as "1" (high level), which indicates that the signal is amplified by high gain, the quantized data is supplemented with one most significant bit of "0"; if the signal received from the hysteresis comparator is "0" (low), indicating that the signal is low gain amplified, the quantized data is increased by an offset

Converted to a quantized value as shown in fig. 5. After the processing, the signal corresponding to the dark star is amplified by high gain, the signal is enhanced, and the signal-to-noise ratio is improved; the signal corresponding to the bright star is amplified by low gain, the signal can be effectively displayed, and the strong signal is only increased at most by considering the influence of photon noise (the photon noise is the square root of the optical signal)1 bit quantization, but still effectively embodies the target information.