Picosecond-level precision time measurement method and circuit
By adaptively adjusting the number of repeated measurements and measurement intervals, combining high-precision clock signal calibration and phased timing, the problem of difficulty in realizing picosecond-level accuracy time measurement in the existing technology is solved, and high-precision and low-power time interval measurement is achieved , suitable for a variety of high-precision measurement scenarios.
Patent Information
- Application Number
- CN202411931869.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-02-07
AI Technical Summary
The prior art is difficult to achieve picosecond-level accuracy in high-precision time measurement, especially in dynamic environments, and the existing equipment is complex and costly, limiting its wide application.
By setting the measurement target accuracy, adaptively adjusting the number of repeated measurements and measurement intervals, and calibrating the intermediate frequency and high-frequency clock signals with high-precision low-frequency clock signals. The low-frequency, intermediate frequency and high-frequency clock phased timing method is used to achieve picoseconds Time interval measurement of level accuracy.
It realizes time interval measurement with picosecond-level accuracy, reduces measurement time and power consumption, enhances the adaptability and flexibility of the system, and is suitable for a variety of high-precision measurement scenarios.
Smart Images
Figure CN119395968A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of fluid measurement, and in particular to a picosecond-level precision time measurement method and circuit. Background Art
[0002] In the field of high-precision time measurement technology, especially in the field of fluid metering, existing technologies face several challenges. First, traditional time measurement methods rely on a single-frequency clock signal for timing, which limits the accuracy and resolution of the measurement. Secondly, although the development of atomic clock technology has brought revolutionary progress to time measurement, the resonance frequency of atoms is used to create high-frequency and stable oscillators to achieve extremely high time measurement accuracy.
[0003] In the field of fluid metering, the measurement accuracy of time intervals is extremely high to ensure the accuracy of flow measurement. However, existing time measurement devices often cannot meet this requirement, especially in dynamic environments. How to achieve high-precision time interval measurement has become a bottleneck in technological development. In addition, existing time measurement technologies often require complex equipment and high costs when achieving picosecond-level precision measurement, which limits their application in a wider range of fields. Summary of the invention
[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method and circuit for measuring time with picosecond accuracy to solve one or more problems in the prior art.
[0005] To achieve the above object, the technical solution of the present invention is as follows: A method for measuring time with picosecond precision comprises the following steps: Step 1: Set the measurement target accuracy, set the number of repeated measurements N according to the measurement target accuracy, and set the time interval td between repeated measurements; Step 2: Using the high-precision low-frequency clock signal LCLK as a reference clock, calibrate the intermediate-frequency clock signal MCLK and the high-frequency clock signal HCLK; Step 3: When the rising edge of the start signal arrives, the low-frequency clock signal LCLK starts timing; When the second rising edge of the low-frequency clock signal LCLK arrives and the remaining measurement time is less than one low-frequency clock cycle, the intermediate-frequency clock signal MCLK starts timing and the low-frequency clock signal LCLK stops timing; When the second rising edge of the intermediate frequency clock signal MCLK arrives and the remaining measurement time is less than one intermediate frequency clock cycle, the high frequency clock signal HCLK starts timing and the intermediate frequency clock signal MCLK stops timing; After this measurement is finished, the low-frequency clock signal LCLK, the medium-frequency clock signal MCLK, and the high-frequency clock signal HCLK all stop timing; Step 4: After a time interval td of repeated measurement, repeat step 3; Step 5: When the rising edge of the end signal arrives, the measurement ends; Step six, measuring the time interval from the rising edge of the start signal to the rising edge of the end signal, dividing this time interval by the set number of repeated measurements N, and obtaining the measurement result TDC_RES.
[0006] Furthermore, step one includes: Set measurement target accuracy; The number of repeated measurements is proportional to the single measurement error and inversely proportional to the target accuracy. The number of repeated measurements is calculated based on this relationship; Set the measurement interval to ensure that the measurement interval is not less than the minimum response time of the device.
[0007] Furthermore, the calibration operation in step 2 includes the following sub-steps: Measuring the phase difference between the low frequency clock signal LCLK and the intermediate frequency clock signal MCLK; Adjust the phase of the intermediate frequency clock signal MCLK to reduce the phase difference with the low frequency clock signal LCLK; Measuring the phase difference between the intermediate frequency clock signal MCLK and the high frequency clock signal HCLK; The phase of the high frequency clock signal HCLK is adjusted to reduce the phase difference with the intermediate frequency clock signal MCLK.
[0008] Furthermore, the processing of the measurement result TDC_RES in step 6 includes the following sub-steps: Repeated measurements were averaged to reduce random errors; Apply the calibration result CAL_RES to correct the measurement result; Output the corrected measurement result TDC_RES.
[0009] In order to make the technical effect complete, the present invention prepares a second set of technical solutions to implement a picosecond-level precision time measurement method described in the first set of technical solutions. The second set of technical solutions is a picosecond-level precision time measurement circuit, including the following parts: Control logic and timing circuits to perform the following functions: Generate a start signal to trigger the start of the entire measurement sequence; Manage the clock calibration process to ensure accurate synchronization of the low-frequency clock signal LCLK, the medium-frequency clock signal MCLK and the high-frequency clock signal HCLK; Performing time-to-digital conversion (TDC) to convert analog time intervals into digital signals for further processing; Control the number of repeated measurements N, and automatically repeat the measurement process according to the set parameters to improve the measurement accuracy; Managing the measurement interval td to ensure that an appropriate time interval is maintained between consecutive measurement cycles; Process the measurement result TDC_RES, including calculating statistical data such as mean value and standard deviation to optimize the accuracy of the measurement result; Communicate with external devices to transfer measurement results and calibration data via interfaces such as SPI, UART or I2C; Also includes A low-frequency clock circuit is connected to an external high-precision reference clock to generate a low-frequency clock signal LCLK; An intermediate frequency clock circuit, connected to the control logic and the timing circuit, generates an intermediate frequency clock signal MCLK; A high-frequency clock circuit, connected to the control logic and the timing circuit, generates a high-frequency clock signal HCLK; A repetition number setting register is connected to the control logic and the timing circuit and is used to set the number of repeated measurements; A fixed delay setting register connected to the control logic and timing circuit for setting the measurement interval td; The output register is connected to the control logic and the timing circuit, and is used to store and output the measurement result TDC_RES and the clock calibration result CAL_RES.
[0010] The low-frequency clock circuit includes an external quartz crystal to ensure high accuracy and stability of the clock signal; The intermediate frequency clock circuit and the high frequency clock circuit generate clock signals through a phase-locked loop PLL or a ring oscillator OSC; The control logic and timing circuit manage the entire measurement process according to the set number of repetitions N and the measurement interval td.
[0011] The repetition setting register and the fixed delay setting register can dynamically adjust the measurement parameters through the external signals N_VAL and TD_VAL; The output registers can store multiple measurement results and output them synchronously through the control logic.
[0012] Compared with the prior art, the beneficial technical effects of the present invention are as follows (i) By adaptively adjusting the number of repeated measurements N and the measurement interval td, and combining the high-precision low-frequency clock signal LCLK as a reference clock to calibrate the intermediate-frequency clock signal MCLK and the high-frequency clock signal HCLK, the present invention achieves time interval measurement with picosecond accuracy.
[0013] (ii) By combining the technical features of phased timing of low-frequency, medium-frequency and high-frequency clocks, the present invention can ensure measurement accuracy while reducing measurement time and power consumption.
[0014] (iii) Through the dynamic adjustment capability of the repetition setting register and the fixed delay setting register, as well as the multiple result storage and synchronous output functions of the output register, this solution enhances the adaptability and flexibility of the system and facilitates its integration and application in a variety of high-precision measurement scenarios.
[0015] (IV) Because the control logic and timing circuit can dynamically manage the entire measurement process, including the generation of the start signal, clock calibration, time-to-digital conversion, and processing of the measurement results, this solution optimizes the measurement process and reduces measurement time and power consumption. This integrated management method improves the automation and efficiency of the measurement, while ensuring high accuracy of the measurement results by precisely controlling the synchronization and accuracy of each clock signal. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is a functional block diagram of a picosecond-level precision time measurement circuit in an exemplary description of the present invention.
[0017] Figure 2 It is a working timing diagram of a picosecond-level precision time measurement circuit in the exemplary description of the present invention. DETAILED DESCRIPTION
[0018] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is a further detailed description of a picosecond-level precision time measurement method and circuit proposed by the present invention in combination with the accompanying drawings and exemplary descriptions. It should be noted that the structure, proportion, size, etc. illustrated in the drawings of this specification are only used to match the content disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention.
[0019] Example In order to achieve a complete technical effect, the present invention has two sets of technical solutions, wherein the first set of technical solutions is a method for measuring time with picosecond precision, please refer to Figure 1 as well as Figure 2 , including the following: Determine the measurement target accuracy First, determine the target measurement accuracy based on the application requirements. For example, if the application requires a measurement accuracy of 1 picosecond (ps), set the target accuracy to 1ps.
[0020] The number of repeated measurements N is proportional to the single measurement error and inversely proportional to the target accuracy. The number of repeated measurements N is calculated based on this relationship.
[0021] The measurement interval td should be no less than the minimum response time of the device to ensure the independence and accuracy of each measurement. For example, if the minimum response time of the device is 100 nanoseconds (ns), td should be set to 100ns or longer.
[0022] The phase detection circuit is used to measure the phase difference between the low frequency clock signal LCLK and the intermediate frequency clock signal MCLK. For example, if the phase difference is 30 degrees, the phase of MCLK needs to be adjusted.
[0023] By adjusting the phase of the intermediate frequency clock signal MCLK, the phase difference with the low frequency clock signal LCLK is reduced. For example, if the phase difference needs to be reduced to 10 degrees, the phase of MCLK is adjusted to 10 degrees.
[0024] Similarly, a phase detection circuit is used to measure the phase difference between the intermediate frequency clock signal MCLK and the high frequency clock signal HCLK. For example, if the phase difference is 15 degrees, the phase of HCLK needs to be adjusted.
[0025] By adjusting the phase of the high frequency clock signal HCLK, the phase difference with the intermediate frequency clock signal MCLK is reduced. For example, if the phase difference needs to be reduced to 5 degrees, the phase of HCLK is adjusted to 5 degrees.
[0026] When the rising edge of the start signal arrives, the low-frequency clock LCLK starts timing first. For example, if the period of LCLK is 1 microsecond (us), timing starts from the rising edge of the start signal.
[0027] When the second rising edge of the low-frequency clock signal LCLK arrives and the remaining measurement time is less than one LCLK clock cycle, the intermediate-frequency clock signal MCLK starts timing and the low-frequency clock signal LCLK stops timing. For example, if the remaining time is 0.5us, it switches to MCLK.
[0028] When the second rising edge of the intermediate frequency clock signal MCLK arrives and the remaining measurement time is less than one MCLK clock cycle, the high frequency clock signal HCLK starts timing and the intermediate frequency clock signal MCLK stops timing. For example, if the remaining time is 0.5 nanoseconds (ns), it switches to HCLK.
[0029] When this measurement is finished, the low-frequency clock signal LCLK, the intermediate-frequency clock signal MCLK, and the high-frequency clock signal HCLK all stop timing. For example, if the rising edge of the end signal arrives, all clocks stop timing.
[0030] After a repeated measurement time interval td, the above timing process is repeated. For example, if td is set to 100ns, then after each measurement, wait 100ns before the next measurement.
[0031] Calculate the measurement result TDC_RES When the rising edge of the end signal arrives, the measurement ends. The time interval from the rising edge of the start signal to the rising edge of the end signal is measured, and this time interval is divided by the set number of repeated measurements N to obtain the measurement result TDC_RES. For example, if the total time is 500us and N is 100, then TDC_RES is 5us.
[0032] The repeated measurement results are averaged to reduce random errors. The calibration result CAL_RES is applied to correct the measurement result. The corrected measurement result TDC_RES is output.
[0033] The second technical solution is a picosecond-level precision time measurement circuit, which is used to implement the first technical solution and includes the following components: Control logic and timing circuit This circuit is the core of the entire system and is responsible for generating a start signal to trigger the start of the entire measurement sequence. It also manages the clock calibration process to ensure accurate synchronization of the low-frequency clock signal LCLK, the intermediate-frequency clock signal MCLK, and the high-frequency clock signal HCLK. In addition, it performs time-to-digital conversion TDC to convert analog time intervals into digital signals for further processing. The control logic and timing circuit also control the number of repeated measurements N and automatically repeat the measurement process according to the set parameters to improve measurement accuracy. It manages the measurement interval td to ensure that the appropriate time interval is maintained between consecutive measurement cycles, and processes the measurement results TDC_RES, including calculating statistical data such as average value and standard deviation to optimize the accuracy of the measurement results. Finally, it communicates with external devices and transmits measurement results and calibration data through interfaces such as SPI, UART, or I2C.
[0034] Low frequency clock circuit The circuit is connected to an external high-precision reference clock to generate a low-frequency clock signal LCLK. This signal serves as a reference for time measurement and is critical to ensuring overall measurement accuracy.
[0035] IF clock circuit The circuit is connected to the control logic and timing circuit to generate the intermediate frequency clock signal MCLK. This signal can be generated by an external crystal or by an internal phase-locked loop (PLL) circuit.
[0036] High frequency clock circuit The circuit is connected to the control logic and timing circuit to generate a high-frequency clock signal HCLK. This signal can be generated by an internal phase-locked loop PLL circuit or an internal ring oscillator OSC circuit.
[0037] Repeat count setting register This register is connected to the control logic and timing circuit to set the number of repeated measurements N. This register allows the measurement parameters to be dynamically adjusted through external signals to adapt to different measurement requirements.
[0038] Fixed Delay Setting Register This register is connected to the control logic and timing circuits and is used to set the measurement interval td. This register also allows dynamic adjustment of measurement parameters via external signals.
[0039] Output Register This register is connected to the control logic and timing circuit, and is used to store and output the measurement result TDC_RES and clock calibration result CAL_RES. It can store multiple measurement results and output them synchronously through the control logic.
[0040] The picosecond-level precision time measurement circuit of the present invention realizes high-precision measurement of time intervals through the coordinated work of the above-mentioned components. The circuit can dynamically adjust parameters according to the measurement target accuracy, optimize measurement time and power consumption, and is suitable for a variety of high-precision measurement scenarios, with broad application prospects. By adaptively adjusting the number of repetitions N and the fixed delay td, the present invention can realize adaptive parameter configuration according to the accuracy requirements of the measurement process, improve measurement efficiency, reduce power consumption during the measurement process, and extend the product life of battery application scenarios.
[0041] Noise suppression. For random noise, the influence of noise can be greatly reduced by multiple measurements. In engineering practice, in addition to measurement accuracy, there is often the influence of noise. Therefore, the method of the present invention reduces the influence of random noise on the measurement result by multiple measurements, thereby improving the reliability of the measurement.
[0042] Power consumption optimization. In battery application scenarios, the time interval measurement technology of the present invention can improve product life by reducing measurement time and power consumption. Through adaptive parameter configuration, the present invention can reduce measurement time and power consumption while ensuring measurement accuracy, which is particularly important for battery-powered portable devices. Example
[0043] In order to demonstrate the practical application of the present invention, an ultrasonic gas flow meter is taken as an example. In this application, the time measurement technology is used to accurately measure the time for gas to flow through the sensor, thereby calculating the gas flow rate.
[0044] Set the small flow rate to 16L / h, the medium flow rate to 1,000L / h, and the large flow rate to 10,000L / h, and the measurement accuracy requirement is ≤1%. According to the mechanical structure design, the differential flight time corresponding to the small flow rate, medium flow rate, and large flow rate is set to 8ns, 500ns, and 5,000ns, respectively. The time measurement errors corresponding to the 1% measurement accuracy requirement are 80ps, 5ns, and 50ns, respectively. Considering the influence of noise, the time measurement accuracy can be set to 8ps, 0.5ns, and 5ns, that is, N is selected to be 63, 1, and 1. By adaptively selecting the N value, the measurement accuracy requirements are met while reducing power consumption.
[0045] In practical applications, the time interval measurement technology of the present invention can significantly improve the measurement accuracy of time interval measurement. For example, if the high-frequency clock HCLK frequency is set to 2GHz, the clock period is 500ps. If 1ps accuracy is expected, the number of repetitions N should be greater than or equal to 500; if 50ps accuracy is expected, the number of repetitions N should be greater than or equal to 10; if 500ps accuracy is expected, the number of repetitions N should be greater than or equal to 1.
[0046] In summary, the time interval measurement technology of the present invention can significantly improve the measurement accuracy of time interval measurement, is applicable to a variety of high-precision measurement scenarios, and has broad application prospects. By adaptively adjusting the number of repetitions N and the fixed delay td, the present invention can realize adaptive parameter configuration according to the accuracy requirements of the measurement process, improve measurement efficiency, reduce power consumption during the measurement process, and increase the product life of battery application scenarios.
[0047] Specific working process First, determine the target measurement accuracy, and accordingly set the number of repeated measurements N and the time interval td between repeated measurements.
[0048] The low-frequency clock circuit is used to generate a high-precision low-frequency clock signal LCLK as the reference clock to calibrate the intermediate-frequency clock signal MCLK and the high-frequency clock signal HCLK to ensure the synchronization and accuracy of all clock signals. During the calibration process, the phase difference between LCLK and MCLK is measured, and the phase of MCLK is adjusted to reduce the phase difference; similarly, the phase difference between MCLK and HCLK is measured, and the phase of HCLK is adjusted to reduce the phase difference.
[0049] After the calibration is completed, the control logic and timing circuit generate a start signal to trigger the start of the entire measurement sequence, and the low-frequency clock signal LCLK starts timing first.
[0050] When the second rising edge of LCLK arrives and the remaining measurement time is less than one LCLK cycle, the intermediate frequency clock signal MCLK starts timing and LCLK stops timing; when the second rising edge of MCLK arrives and the remaining measurement time is less than one MCLK cycle, the high frequency clock signal HCLK starts timing and MCLK stops timing. After this measurement is completed, LCLK, MCLK, and HCLK all stop timing.
[0051] After a time interval td of repeated measurement, the above timing process is repeated.
[0052] When the rising edge of the end signal arrives, the measurement ends, and the time interval from the rising edge of the start signal to the rising edge of the end signal is measured. This time interval is divided by the set number of repeated measurements N to obtain the measurement result TDC_RES.
[0053] Repeated measurement results are averaged to reduce random errors, and the calibration result CAL_RES is applied to correct the measurement result. The corrected measurement result TDC_RES is stored through the output register and can communicate with external devices through control logic and timing circuits, and transmit measurement results and calibration data through interfaces such as SPI, UART or I2C.
[0054] The measurement parameters can be adjusted dynamically through the repetition setting register and the fixed delay setting register to optimize the measurement time and power consumption. The output register can store multiple measurement results and output them synchronously through the control logic to ensure the accuracy and reliability of the measurement results.
[0055] In summary, the present invention provides a high-precision time interval measurement technology, and the measurement accuracy can theoretically reach the order of 1ps. The desired measurement accuracy is obtained by adaptive parameter configuration and multiple measurements, and the adaptive parameter configuration function of repeated measurement times N is provided. The adaptive parameter configuration is performed according to the measurement accuracy requirements of the specific application. The desired measurement accuracy is obtained by multiple measurements. The larger the number of repetitions N, the smaller the measurement error.
[0056] According to the above description, many improvements and other embodiments of the present invention are obvious to those skilled in the art. Therefore, the above embodiments and descriptions only describe the principles of the present invention. Without departing from the principles and scope of the present invention, the present invention may have various changes and improvements, which are within the scope of the present invention. The scope of the present invention is defined by the attached claims and their equivalents.
Claims
1. A method for measuring time with picosecond precision, characterized in that: The following steps are involved: Step 1: Set the measurement target accuracy, set the number of repeated measurements N according to the measurement target accuracy, and set the time interval td between repeated measurements; Step 2: Using the high-precision low-frequency clock signal LCLK as a reference clock, calibrate the intermediate-frequency clock signal MCLK and the high-frequency clock signal HCLK; Step 3: When the rising edge of the start signal arrives, the low-frequency clock signal LCLK starts timing; When the second rising edge of the low-frequency clock signal LCLK arrives and the remaining measurement time is less than one low-frequency clock cycle, the intermediate-frequency clock signal MCLK starts timing and the low-frequency clock signal LCLK stops timing; When the second rising edge of the intermediate frequency clock signal MCLK arrives and the remaining measurement time is less than one intermediate frequency clock cycle, the high frequency clock signal HCLK starts timing and the intermediate frequency clock signal MCLK stops timing; After this measurement is finished, the low-frequency clock signal LCLK, the medium-frequency clock signal MCLK, and the high-frequency clock signal HCLK all stop timing; Step 4: After a time interval td of repeated measurement, repeat step 3; Step 5: When the rising edge of the end signal arrives, the measurement ends; Step six, measuring the time interval from the rising edge of the start signal to the rising edge of the end signal, dividing this time interval by the set number of repeated measurements N, and obtaining the measurement result TDC_RES.
2. A picosecond-level precision time measurement method as claimed in claim 1, characterized in that: Step one includes: Set measurement target accuracy; The number of repeated measurements is proportional to the single measurement error and inversely proportional to the target accuracy. The number of repeated measurements is calculated based on this relationship; Set the measurement interval to ensure that the measurement interval is not less than the minimum response time of the device.
3. A picosecond-level precision time measurement method as claimed in claim 1, characterized in that: The calibration operation in step 2 includes the following sub-steps: Measuring the phase difference between the low frequency clock signal LCLK and the intermediate frequency clock signal MCLK; Adjust the phase of the intermediate frequency clock signal MCLK to reduce the phase difference with the low frequency clock signal LCLK; Measuring the phase difference between the intermediate frequency clock signal MCLK and the high frequency clock signal HCLK; The phase of the high frequency clock signal HCLK is adjusted to reduce the phase difference with the intermediate frequency clock signal MCLK.
4. The method for measuring time with picosecond precision as claimed in claim 1, characterized in that: The processing of the measurement result TDC_RES in step 6 includes the following sub-steps: Repeated measurements were averaged to reduce random errors; Apply the calibration result CAL_RES to correct the measurement result; Output the corrected measurement result TDC_RES.
5. A picosecond precision time measurement circuit, based on a picosecond precision time measurement method according to any one of claims 1 to 4, characterized in that: Includes the following parts: Control logic and timing circuits to perform the following functions: Generate a start signal to trigger the start of the entire measurement sequence; Manage the clock calibration process to ensure accurate synchronization of the low-frequency clock signal LCLK, the medium-frequency clock signal MCLK and the high-frequency clock signal HCLK; Performing time-to-digital conversion (TDC) to convert analog time intervals into digital signals for further processing; Control the number of repeated measurements N, and automatically repeat the measurement process according to the set parameters to improve the measurement accuracy; Managing the measurement interval td to ensure that an appropriate time interval is maintained between consecutive measurement cycles; Process the measurement result TDC_RES, including calculating statistical data such as mean value and standard deviation to optimize the accuracy of the measurement result; Communicate with external devices to transfer measurement results and calibration data via interfaces such as SPI, UART or I2C; Also includes A low-frequency clock circuit is connected to an external high-precision reference clock to generate a low-frequency clock signal LCLK; An intermediate frequency clock circuit, connected to the control logic and the timing circuit, generates an intermediate frequency clock signal MCLK; A high-frequency clock circuit, connected to the control logic and the timing circuit, generates a high-frequency clock signal HCLK; A repetition number setting register is connected to the control logic and the timing circuit and is used to set the number of repeated measurements; A fixed delay setting register connected to the control logic and timing circuit for setting the measurement interval td; The output register is connected to the control logic and the timing circuit, and is used to store and output the measurement result TDC_RES and the clock calibration result CAL_RES.
6. The picosecond-level precision time measurement circuit according to claim 5, characterized in that: The low-frequency clock circuit includes an external quartz crystal to ensure high accuracy and stability of the clock signal; The intermediate frequency clock circuit and the high frequency clock circuit generate clock signals through a phase-locked loop PLL or a ring oscillator OSC; The control logic and timing circuit manage the entire measurement process according to the set number of repetitions N and the measurement interval td.
7. The picosecond-level precision time measurement circuit according to claim 5, characterized in that: The repetition number setting register and the fixed delay setting register can dynamically adjust the measurement parameters through the external signals N_VAL and TD_VAL; The output registers can store multiple measurement results and output them synchronously through the control logic.