Chip atomic clock internal ADC sampling window automatic adjusting circuit and method

Abstract

The invention belongs to the technical field of quantum measurement and control, particularly relates to a circuit and a method for automatically adjusting an ADC sampling window in a chip atomic clock, and aims to solve the problems of precise control of the temperature of the chip atomic clock and precise control of each modulation-demodulation servo loop signal. The circuit comprises a DAC output level control sub-circuit, an input signal end, a precision instrument amplifier, a digital potentiometer and an ADC sampling sub-circuit. The DAC output level control sub-circuit is connected with an inverted input end of the precision instrument amplifier, and an input signal end is connected with a normal phase input end of the precision instrument amplifier; the digital potentiometer is connected with the gain control end of the precision instrument amplifier, and the output end of the precision instrument amplifier is connected with the ADC sampling sub-circuit. According to the invention, the temperature acquisition ADC window of the chip atomic clock and the ADC acquisition window of the demodulation signal can be automatically adjusted, and the temperature control capability of the chip atomic clock laser and the atomic air chamber and the servo control capability of the laser current and the voltage-controlled crystal oscillator current are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of quantum measurement and control, and specifically relates to a circuit and method for automatically adjusting an ADC sampling window inside a chip atomic clock. Background Art

[0002] The atomic clock is currently the most accurate time and frequency standard device. The chip atomic clock is an atomic clock that is comparable in size and weight to a chip. Because it can guarantee high-precision time and frequency output while being small in size, light in weight and low in power consumption, the chip atomic clock has broad application prospects in scenarios that have strict requirements on size and power consumption and require higher frequency stability.

[0003] The basic principle of the chip atomic clock is coherent population trapping (CPT). The chip atomic clock obtains coherent two-color light through microwave modulation laser and acts on atoms in the atomic gas chamber to achieve CPT resonance, obtains the stable microwave frequency of the specific energy level radiation transition of the atom required by the atomic clock as the spectral line signal, and converts the microwave frequency into a standard frequency output that is convenient for use in practical applications through electronic devices. The chip atomic clock consists of a physical system and a control system. The physical system is the core of the entire chip atomic clock, and the laser and the atomic gas chamber are key components in the physical system. The laser used in the chip atomic clock is a vertical cavity surface emitting laser. The change in the operating temperature of the laser will directly cause the output frequency of the laser to change, thereby affecting the stability of the chip atomic clock. Similarly, the temperature stability of the atomic gas chamber will directly affect the stability of the chip atomic clock. Since the control current of the laser directly affects the intensity of the Doppler absorption peak of the chip atomic clock, the control voltage of the voltage-controlled crystal oscillator directly affects the output frequency of the chip clock. The servo control of the current also has an important influence on the stability of the chip atomic clock.

[0004] Therefore, how to achieve precise control of the temperature of the chip atomic clock and precise control of each modulation and demodulation servo loop signal is a crucial direction in the current research field. Summary of the invention

[0005] In order to solve the above problems in the prior art, namely the instability of the chip atomic clock temperature and the instability of the modulation and demodulation servo loop, the present invention provides an automatic adjustment circuit for the ADC sampling window inside the chip atomic clock, including a DAC output level control subcircuit, an input signal terminal, a precision instrument amplifier, a digital potentiometer, an ADC sampling subcircuit and a single-chip microcomputer:

[0006] The single chip microcomputer writes the binary code corresponding to the target voltage value to the DAC chip in the DAC output level control subcircuit through the SPI interface;

[0007] The SPI interface is used to enable the single-chip microcomputer to communicate with peripheral devices in a serial manner;

[0008] The DAC output level control subcircuit is used to convert the digital quantity of the single-chip microcomputer into an analog quantity, wherein the digital quantity is written by the single-chip microcomputer through the SPI interface; the DAC output level control subcircuit includes a DAC chip;

[0009] The precision instrument amplifier is used to perform amplification processing based on the input signal;

[0010] The connection methods include wire connection and PCB circuit board welding; the precision instrument amplifier amplifies the input voltage signal and outputs it to the ADC sampling subcircuit, the signal collected by the ADC sampling subcircuit is sent to the single-chip microcomputer for processing, and the single-chip microcomputer adjusts the resistance value of the digital potentiometer and the output voltage of the DAC;

[0011] The ADC sampling subcircuit is used to collect the output voltage signal of the precision instrument amplifier and feed the collected voltage signal back to the single chip microcomputer.

[0013] Furthermore, the connection method of the automatic adjustment circuit of the ADC sampling window inside the chip atomic clock specifically includes:

[0014] The DAC output level control subcircuit is connected to the inverting input terminal of the precision instrument amplifier, and the input signal terminal is connected to the non-inverting input terminal of the precision instrument amplifier; the digital potentiometer is connected to the gain control terminal RG of the precision instrument amplifier, and the output terminal of the precision instrument amplifier is connected to the ADC sampling subcircuit.

[0015] Furthermore, the circuit parameters of the DAC output level control subcircuit specifically include:

[0016] DAC chip output voltage

[0017] Among them, V2 represents the reference voltage of the DAC chip. The DAC chip is an a-bit voltage output chip, and the output voltage value has 2^a kinds. The microcontroller writes the binary number x1 corresponding to the output voltage value of the DAC chip into the DAC chip through the SPI interface.

[0018] Furthermore, the working principle of the digital potentiometer specifically includes:

[0019] Used to control the gain of precision instrument amplifier by changing the resistance value in the digital potentiometer;

[0020] When you reduce the resistance value in the digital potentiometer, the gain of the precision instrumentation amplifier increases;

[0021] As you increase the resistance value in the digital potentiometer, the gain of the precision instrumentation amplifier decreases.

[0022] Digital potentiometer is also called digital programmable resistor. It uses digital control to adjust the resistance value. It has the advantages of flexible use, high adjustment accuracy, no contact, low noise, not easy to be contaminated, anti-vibration, anti-interference, small size and long life.

[0023] Furthermore, the control of the gain of the precision instrument amplifier by changing the resistance value in the digital potentiometer specifically includes:

[0024] Magnification

[0025] Among them, R represents the resistance value of the digital potentiometer, and 100KΩ is the fixed resistance value of the internal circuit of the precision instrumentation amplifier itself.

[0026] Furthermore, the ADC sampling subcircuit adopts an ADC sampling chip with a precision of 12 bits, and its circuit parameters specifically include:

[0027] The digital value of the voltage sampling value of the 12-bit ADC sampling subcircuit is 4096 is 2 to the 12th power;

[0028] The voltage value of the input signal is

[0029] Among them, V3 is the sampling reference voltage of the 12-bit ADC sampling chip.

[0030] Furthermore, the automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock can also collect temperature, specifically including:

[0031] The voltage value V3 sampled by the ADC is converted into the temperature T of the component according to the relationship between the temperature T of the component and the voltage value V of the input signal;

[0032] The relationship between the temperature T of the component and the input signal voltage value V is V=K×T;

[0033] Where K is the conversion coefficient between the component temperature T and the input signal voltage V.

[0034] Furthermore, the single chip microcomputer specifically includes an MSP430 single chip microcomputer.

[0035] The MSP430 series microcontroller is a 16-bit ultra-low power mixed signal processor with a reduced instruction set.

[0036] Another aspect of the present invention provides a method for automatically adjusting the sampling window of an ADC in a chip atomic clock, the method comprising:

[0037] Step S10, searching for input signals by adjusting the sampling window of the ADC sampling subcircuit to full scale;

[0038] Step S20, when the input signal is not within the sampling window of the ADC sampling subcircuit, move the ADC sampling window position until the ADC sampling window can capture the input signal; proceed to step S30;

[0039] Step S30, dynamically adjusting the position of the sampling window of the ADC sampling subcircuit through the PID algorithm, keeping continuous tracking of the input signal, and maintaining the input signal within the ADC sampling window;

[0040] Step S40, after the input signal voltage meets the set fluctuation range, the amplification factor of the precision instrument amplifier is reduced by increasing the resistance value of the digital potentiometer, and the DAC output level is controlled by the DAC output level control subcircuit, so that the sampling window of the ADC sampling subcircuit is narrowed and the ADC sampling window can completely receive the input signal;

[0041] The sampling window of the ADC sampling subcircuit is narrowed, and the sampling range of the ADC sampling subcircuit is reduced;

[0042] Step S50, recording the maximum and minimum values ​​of the input signal, adjusting the DAC output level and the resistance in the digital potentiometer until the input signal band range is distributed within the preset range of the sampling window.

[0043] Furthermore, the set fluctuation range specifically includes:

[0044] When the difference between the maximum and minimum values ​​of a certain number of consecutive input signal voltages is within a set empirical value range, the fluctuation range meets the requirements.

[0045] Beneficial effects of the present invention:

[0046] (1) The present invention realizes the tracking and accurate acquisition of level signals by automatically adjusting the position and size of the ADC sampling window;

[0047] (2) The present invention achieves improved temperature stability of the chip atomic clock physical system and improved stability of the modulation and demodulation signal servo loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0049] Figure 1 It is a schematic diagram of an automatic adjustment circuit for the sampling window of an ADC inside a chip atomic clock of the present invention;

[0050] Figure 2 The present invention is a flow chart of a method for automatically adjusting an ADC sampling window inside a chip atomic clock. DETAILED DESCRIPTION

[0051] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0052] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0053] The present invention provides an automatic adjustment circuit for ADC sampling window inside a chip atomic clock, including a DAC output level control subcircuit, an input signal terminal, a precision instrument amplifier, a digital potentiometer, an ADC sampling subcircuit and a single-chip microcomputer;

[0054] The single chip microcomputer writes the binary code corresponding to the target voltage value to the DAC chip in the DAC output level control subcircuit through the SPI interface;

[0055] The SPI interface is used to enable the single-chip microcomputer to communicate with peripheral devices in a serial manner;

[0056] The DAC output level control subcircuit is used to convert the digital quantity of the single-chip microcomputer into an analog quantity, wherein the digital quantity is written by the single-chip microcomputer through the SPI interface; the DAC output level control subcircuit includes a DAC chip;

[0057] The precision instrument amplifier is used to perform amplification processing based on the input signal;

[0058] The connection methods include wire connection and PCB circuit board welding. The precision instrument amplifier amplifies the input voltage signal and outputs it to the ADC sampling subcircuit. The signal collected by the ADC sampling subcircuit is sent to the single-chip microcomputer for processing. The single-chip microcomputer adjusts the resistance value of the digital potentiometer and the output voltage of the DAC.

[0059] The ADC sampling subcircuit is used to collect the output voltage signal of the precision instrument amplifier and feed the collected voltage signal back to the single chip microcomputer.

[0060] In this embodiment, the connection method of the automatic adjustment circuit of the ADC sampling window inside the chip atomic clock specifically includes:

[0061] The DAC output level control subcircuit is connected to the inverting input terminal of the precision instrument amplifier, and the input signal terminal is connected to the non-inverting input terminal of the precision instrument amplifier; the digital potentiometer is connected to the gain control terminal RG of the precision instrument amplifier, and the output terminal of the precision instrument amplifier is connected to the ADC sampling subcircuit.

[0062] In this embodiment, the circuit parameters of the DAC output level control subcircuit specifically include:

[0063] DAC chip output voltage

[0064] Among them, V2 represents the reference voltage of the DAC chip. The DAC chip is an a-bit voltage output chip, and the output voltage value has 2^a kinds. The microcontroller writes the binary number x1 corresponding to the output voltage value of the DAC chip into the DAC chip through the SPI interface.

[0065] In this embodiment, the precision instrumentation amplifier uses the INA333 precision instrumentation amplifier, which can provide good accuracy at low power consumption and is suitable for various portable applications due to its small size and low power consumption.

[0066] In this embodiment, the working principle of the digital potentiometer specifically includes:

[0067] Used to control the gain of precision instrument amplifier by changing the resistance value of digital potentiometer;

[0068] When you reduce the resistance value in the digital potentiometer, the gain of the precision instrumentation amplifier increases;

[0069] As you increase the resistance value in the digital potentiometer, the gain of the precision instrumentation amplifier decreases.

[0070] In this embodiment, the control of the gain of the precision instrument amplifier by changing the resistance value of the digital potentiometer specifically includes:

[0071] Magnification

[0072] Where R represents the resistance value of the digital potentiometer.

[0073] In this embodiment, the circuit parameters of the ADC sampling subcircuit specifically include:

[0074] The digital value of the voltage sampling value of the 12-bit ADC sampling subcircuit is 4096 is 2 to the 12th power;

[0075] The voltage value of the input signal is

[0076] Among them, V3 is the sampling reference voltage of the 12-bit ADC sampling chip;

[0077] Assuming that the voltage sampling range of the ADC chip is [0, V3], the output signal range of the precision instrumentation amplifier is [0, V3];

[0078] Since the output signal of the precision instrumentation amplifier is (V-V1)×G, the range of the input signal V1 is

[0079] Substitute G into the ADC dynamic sampling window range:

[0080] It can be seen that changing V1 can adjust the starting point of the sampling window (the smaller V1 is, the lower the starting point of the input signal that can be sampled can be), and changing R can adjust the width of the sampling window (the larger R is, the larger the fluctuation range of the input signal that can be sampled can be);

[0081] The center point voltage of the sampling window is In the process of tracking the input signal, the PID algorithm is used to keep the center point of the sampling window overlapping with the fluctuation range of the input signal;

[0082] The distance between the input signal V and the center point voltage is The new sampling window center point position P is calculated through the incremental PID algorithm to obtain the new V1 value Get V 1新 Back-pushing DAC control amount The control quantity x1 is the value written into the DAC chip by the microcontroller through the SPI interface.

[0083] In this embodiment, the automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock can also collect temperature, specifically including:

[0084] The voltage value V3 sampled by the ADC is converted into the temperature T of the component according to the relationship between the temperature T of the component and the voltage value V of the input signal (mostly linear);

[0085] The relationship between the temperature T of the component and the input signal voltage value V is V=K×T;

[0086] Where K is the conversion coefficient between the component temperature T and the input signal voltage V.

[0087] On the other hand, the present invention provides a method for automatically adjusting the sampling window of an ADC inside a chip atomic clock, comprising:

[0088] In order to more clearly explain the automatic adjustment method of the ADC sampling window in a chip atomic clock of the present invention, the following is combined with Figure 2 The embodiments of the present invention are described in detail.

[0089] A second embodiment of the present invention provides a method for automatically adjusting the sampling window of an ADC in a chip atomic clock, including the following steps:

[0090] Step S10, searching for input signals by adjusting the sampling window of the ADC sampling subcircuit to full scale;

[0091] Step S20, when the input signal is not within the sampling window of the ADC sampling subcircuit, move the ADC sampling window position until the ADC sampling window can capture the input signal; proceed to step S30;

[0092] Step S30, dynamically adjusting the position of the sampling window of the ADC sampling subcircuit through the PID algorithm, keeping continuous tracking of the input signal, and maintaining the input signal within the ADC sampling window;

[0093] Step S40, after the input signal voltage meets the set fluctuation range, the amplification factor of the precision instrument amplifier is reduced by increasing the resistance value of the digital potentiometer, and the DAC output level is controlled by the DAC output level control subcircuit, so that the sampling window of the ADC sampling subcircuit is narrowed and the ADC sampling window can completely receive the input signal;

[0094] The sampling window of the ADC sampling subcircuit is narrowed, and the sampling range of the ADC sampling subcircuit is reduced;

[0095] Step S50, record the maximum and minimum values ​​of the input signal, adjust the DAC output level and the resistance in the digital potentiometer until the input signal band range is distributed within the preset range of the sampling window. In this embodiment, the set fluctuation range specifically includes:

[0096] At a certain moment, when the difference between the maximum and minimum values ​​of a certain number of consecutive input signal voltages is within a set empirical value range, the fluctuation range meets the requirements.

[0097] In this embodiment, taking the 12-bit ADC sampling module as an example, if the ADC sampling value of the input signal exceeds the sampling range of the ADC sampling window (that is, there are values ​​of 1 and 4095), then the digital potentiometer resistance is increased to reduce the amplification factor of the precision instrumentation amplifier, thereby expanding the ADC sampling window, and adjusting the output of the DAC until the ADC sampling window can just cover the input signal.

[0098] In this embodiment, if the fluctuation range of the input signal is too small relative to the sampling window, the maximum and minimum values ​​of the input signal are recorded, and the DAC output level and the digital potentiometer resistance value are adjusted to make the fluctuation range of the input signal just within the ADC sampling window range.

[0099] Although the various steps in the above embodiment are described in the above-mentioned order, those skilled in the art can understand that in order to achieve the effect of this embodiment, different steps do not have to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple changes are within the scope of protection of the present invention.

[0100] The terms "first", "second", etc. are used to distinguish similar objects rather than to describe or indicate a particular order or sequence.

[0101] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or also includes elements inherent to such process, method, article, or apparatus / device.

[0102] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A chip atomic clock internal ADC sampling window automatic adjustment circuit, characterized in that: It includes a DAC output level control subcircuit, an input signal terminal, a precision instrument amplifier, a digital potentiometer, an ADC sampling subcircuit and a single-chip microcomputer; The single chip microcomputer writes the binary code corresponding to the target voltage value to the DAC chip in the DAC output level control subcircuit through the SPI interface; The SPI interface is used to enable the single-chip microcomputer to communicate with peripheral devices in a serial manner; The DAC output level control subcircuit is used to convert the digital quantity of the single-chip microcomputer into an analog quantity, wherein the digital quantity is written by the single-chip microcomputer through the SPI interface; the DAC output level control subcircuit includes a DAC chip; The precision instrument amplifier is used to perform amplification processing based on the input signal; The connection methods include wire connection and PCB circuit board welding. The precision instrument amplifier amplifies the input voltage signal and outputs it to the ADC sampling subcircuit. The signal collected by the ADC sampling subcircuit is sent to the single-chip microcomputer for processing. The single-chip microcomputer adjusts the resistance value of the digital potentiometer and the output voltage of the DAC. The ADC sampling subcircuit is used to collect the output voltage signal of the precision instrument amplifier and feed the collected voltage signal back to the single chip microcomputer.

2. The automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock according to claim 1, characterized in that: The connection method of the automatic adjustment circuit of the ADC sampling window inside the chip atomic clock specifically includes: The DAC output level control subcircuit is connected to the inverting input terminal of the precision instrument amplifier, and the input signal terminal is connected to the non-inverting input terminal of the precision instrument amplifier; the digital potentiometer is connected to the gain control terminal RG of the precision instrument amplifier, and the output terminal of the precision instrument amplifier is connected to the ADC sampling subcircuit.

3. The automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock according to claim 1, characterized in that: The DAC output level control subcircuit specifically includes: DAC chip output voltage Among them, V2 represents the reference voltage of the DAC chip, a represents the number of bits of the DAC chip voltage output chip, 2 a The number represents the output voltage value. The microcontroller writes the binary number x1 corresponding to the output voltage value of the DAC chip into the DAC chip through the SPI interface.

4. The automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock according to claim 2, characterized in that: The working principle of the digital potentiometer specifically includes: The gain of the precision instrumentation amplifier is controlled by changing the resistance value in the digital potentiometer; When you reduce the resistance value in the digital potentiometer, the gain of the precision instrumentation amplifier increases; As you increase the resistance value in the digital potentiometer, the gain of the precision instrumentation amplifier decreases.

5. The automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock according to claim 3, characterized in that: The method of controlling the gain of the precision instrument amplifier by changing the resistance value of the digital potentiometer specifically includes: The magnification G is Among them, R represents the resistance value of the digital potentiometer, and 100KΩ is the fixed resistance value of the internal circuit of the precision instrumentation amplifier itself.

6. The automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock according to claim 3, characterized in that: The ADC sampling subcircuit adopts an ADC sampling chip with a precision of 12 bits, and its circuit parameters specifically include: The digital value OUT of the voltage sampling value of the ADC sampling subcircuit using the ADC sampling chip with a precision of 12 bits is 4096 is 2 to the 12th power; Then the voltage value V of the input signal is Among them, V3 is the sampling reference voltage of the 12-bit ADC sampling chip.

7. The automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock according to claim 3, characterized in that: The automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock can also collect temperature, specifically including: The voltage value V3 sampled by the ADC is converted into the temperature T of the component according to the relationship between the temperature T of the component and the voltage value V of the input signal; The relationship between the temperature T of the component and the input signal voltage value V is V=K×T; Where K is the conversion coefficient between the component temperature T and the input signal voltage V.

8. The automatic adjustment circuit of the ADC sampling circuit inside a chip atomic clock according to claim 1, characterized in that: The single chip microcomputer specifically includes an MSP430 single chip microcomputer.

9. A method for automatically adjusting the sampling window of an ADC inside a chip atomic clock, based on the circuit for automatically adjusting the sampling window of an ADC inside a chip atomic clock according to any one of claims 1 to 7, characterized in that: The method comprises: Step S10, searching for input signals by adjusting the sampling window of the ADC sampling subcircuit to full scale; Step S20, when the input signal is not within the sampling window of the ADC sampling subcircuit, move the ADC sampling window position until the ADC sampling window can capture the input signal; proceed to step S30; Step S30, dynamically adjusting the position of the sampling window of the ADC sampling subcircuit through the PID algorithm, keeping continuous tracking of the input signal, and maintaining the input signal within the ADC sampling window; Step S40, after the input signal voltage meets the set fluctuation range, by increasing the resistance value of the digital potentiometer, reducing the amplification factor of the precision instrument amplifier, and controlling the DAC output level through the DAC output level control subcircuit, so that the sampling window of the ADC sampling subcircuit is narrowed and the ADC sampling window can completely receive the input signal; The sampling window of the ADC sampling subcircuit is narrowed, and the sampling range of the ADC sampling subcircuit is reduced; Step S50, recording the maximum and minimum values ​​of the input signal, adjusting the DAC output level and the resistance in the digital potentiometer until the input signal band range is distributed within the preset range of the sampling window.

10. The automatic adjustment circuit of the ADC sampling circuit inside the chip atomic clock according to claim 7, characterized in that: The set fluctuation range specifically includes: When the difference between the maximum and minimum values ​​of a certain number of consecutive input signal voltages is within a set empirical value range, the fluctuation range meets the requirements.

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