A high-precision absolute distance measurement system based on microwave coherent forwarding

Abstract

The present invention discloses a high-precision absolute distance measurement system based on microwave coherent forwarding, which is used for high-precision distance measurement between two fixed points. The measurement system adopts a two-way forwarding ranging architecture, using the high-frequency two-way forwarding architecture and integer multiple coherent forwarding to obtain high-precision and stable phase measurement values. After using GNSS / pseudo-code to fix the ambiguity, the final absolute distance measurement result can be obtained. After the overall system is implemented in hardware, the function is tested. After multiple experimental measurements, the present invention has achieved sub-millimeter measurement accuracy in kilometer-level distance measurement, and the relative uncertainty of the measurement result is 5um±4×10 ‑7 L.

Description

Technical Field

[0001] The present invention belongs to the technical field of outdoor high-precision distance measurement, and in particular relates to a high-precision absolute distance measurement system based on microwave coherent forwarding. Background Art

[0002] In daily life, scientific research and engineering applications, the measurement of length, as a basic metrological need, is of self-evident importance.

[0003] With the development of society and the progress of the times, distance measurement technology has also advanced. From contact distance measurement tools such as rulers and vernier calipers to non-contact distance measurement instruments such as sonar and total stations, the accuracy and range of distance measurement have been improved. Choosing the right measurement tools and methods in different environments can effectively reduce measurement costs and improve measurement efficiency.

[0004] Currently, commonly used distance measurement methods include laser rangefinders, infrared rangefinders, ultrasonic rangefinders, and microwave rangefinders. Each type of rangefinder has its own advantages and disadvantages. For field applications, laser rangefinders offer high accuracy and a wide range (ranging from tens of meters to over ten kilometers), but they are eye-unsafe and susceptible to environmental influences. Rain, snow, or dust can significantly reduce the accuracy and range of laser rangefinders. While infrared rangefinders are eye-safe, they suffer from poor accuracy, a short range, and, like laser rangefinders, are susceptible to environmental influences. Ultrasonic rangefinders offer simple hardware and low cost, but they also suffer from low accuracy, a short range, and are susceptible to environmental factors such as temperature, humidity, and airflow. Therefore, for field applications, there is an urgent need for a fixed-point absolute distance measurement system and method that is highly accurate, has a long range, and is not susceptible to environmental influences. Summary of the Invention

[0005] This invention provides a high-precision absolute distance measurement system based on microwave coherent forwarding. This system employs a two-way forwarding architecture and uses integer-multiple coherent forwarding to address the initial phase uncertainty inherent in two-way forwarding. Combined with GNSS / pseudo-code fixed ambiguity, this system enables high-precision absolute distance measurement between two fixed points. Practical verification demonstrates that this system can achieve sub-millimeter ranging accuracy for kilometer-level distance measurements.

[0006] On one hand, the present invention provides a high-precision absolute distance measurement system based on microwave coherent forwarding. The system uses a ranging (primary / secondary) board to generate a ranging signal, uses integer multiple coherent forwarding to fix the initial phase, and then obtains a high-precision distance with ambiguity. Combined with GNSS / pseudo-code fixed ambiguity, the high-precision absolute distance measurement between two fixed points is completed.

[0007] The system specifically includes: two oven-controlled crystal oscillators for generating a highly stable reference frequency; two transmitting antennas for transmitting ranging signals; and two receiving antennas for receiving ranging signals. A ranging mainboard is connected to one oven-controlled crystal oscillator and is used to generate a high-frequency (S-band) microwave ranging signal and transmit the signal to a ranging slave board via the transmitting antenna connected thereto. The high-frequency microwave ranging signal transmitted by the ranging slave board is received via the receiving antenna connected thereto, the ranging data is analyzed and processed, and the processed ranging data is transmitted to a universal asynchronous receiver / transmitter (UART). The ranging slave board is connected to another oven-controlled crystal oscillator and is used to receive the high-frequency microwave ranging signal transmitted by the ranging mainboard via the receiving antenna connected thereto, generate a high-frequency microwave ranging signal of another frequency point after integer multiple coherent forwarding, and transmit the signal to the ranging mainboard via the transmitting antenna connected thereto. The universal asynchronous receiver / transmitter (UART) is used to transmit the ranging data of the ranging mainboard to a personal computer, and the PC completes the final data analysis.

[0008] In the system, the ranging mainboard includes a ranging transmitting end part, a ranging receiving end part and a ranging data processing and sending part, wherein,

[0009] The ranging transmitter part includes: a digital intermediate frequency signal generation module, which is used to generate a digital intermediate frequency signal based on a constant temperature crystal oscillator; a digital / analog conversion module, which converts the digital intermediate frequency signal into an analog intermediate frequency signal; and an up-conversion module, which up-converts the analog intermediate frequency signal to the default frequency point f. m ;

[0010] The ranging receiver part includes: a down-conversion module, which down-converts the high-frequency microwave ranging signal to an analog intermediate frequency; an analog / digital conversion module, which converts the analog intermediate frequency signal into a digital intermediate frequency signal; a phase-locked loop module, which locks and outputs the phase of the signal received by the ranging mainboard according to the digital intermediate frequency signal;

[0011] The ranging data processing and sending part includes: an average processing module, which performs average processing on the phase data output by the ranging mainboard to filter out some noise interference; a data sending module, which sends the ranging data after average processing to the PC through the universal asynchronous receiver and transmitter (UART);

[0012] The ranging slave board includes a ranging receiver part and a coherent forwarding part, wherein:

[0013] The ranging receiver part includes: a down-conversion module, which down-converts the high-frequency microwave ranging signal to an analog intermediate frequency; an analog / digital conversion module, which converts the analog intermediate frequency signal into a digital intermediate frequency signal; a phase-locked loop module, which locks and outputs the phase of the ranging slave board receiving signal according to the digital intermediate frequency signal;

[0014] The coherent forwarding part includes: a coherent module, which forwards the locked received signal to generate a digital intermediate frequency signal, and maintains the phase ratio relationship as the coherent forwarding ratio k during the forwarding process; a digital / analog conversion module, which converts the digital intermediate frequency digital signal into an analog intermediate frequency signal; an up-conversion module, which up-converts the analog intermediate frequency signal to the default frequency point f s .

[0015] In the system, the ranging transmitting end part and the ranging receiving end part of the ranging main board are in the working state by default, and the ranging data processing and sending part of the ranging main board is in the non-working state by default. When the ranging receiving end part of the ranging main board locks the signal phase, the ranging data processing and sending part of the ranging main board automatically changes to the working state; the ranging receiving end part and the coherent forwarding part of the ranging slave board are in the working state by default.

[0016] In the system, the ranging main board and ranging slave board use the same hardware structure, only different filters are replaced according to the default frequency of their respective transmission and reception. The default frequency of ranging transmission of ranging main board is f m , the default frequency point for ranging reception is f s , and the default frequency of the ranging slave board is f s , the default frequency point for ranging reception is f m ;f s f m The coherent forwarding ratio k is a positive integer, and f s =k·f m The ranging main board and ranging slave board use exactly the same hardware structure, which simplifies the system design and reduces the cost of use. In addition, the ranging main board and ranging slave board use different default frequencies, which effectively reduces the same-frequency interference.

[0017] Another aspect of the present invention provides a method for using a high-precision absolute distance measurement system based on microwave coherent forwarding.

[0018] The present invention mainly emphasizes the use of integer forwarding ratios to solve the initial phase uncertainty problem existing in the two-way forwarding architecture. It combines the high-frequency two-way forwarding architecture with the integer multiple coherent forwarding method to obtain high-precision and stable phase measurement data containing ambiguity; and uses GNSS / pseudo-code to fix the ambiguity, thereby obtaining the final high-precision absolute distance measurement value.

[0019] When using a two-way forwarding architecture for carrier phase measurement, phase zero uncertainty is a key issue. Specifically, while the measured distance remains constant, the carrier phase measurement value fluctuates after each system power-up or reset. This severely limits the application of carrier phase measurement for high-precision absolute distance measurement. This issue will be analyzed below from the perspectives of signal generation, transmission, and forwarding.

[0020] During the ranging process, the links that can cause phase jumps involve the frequency synthesizer generating the carrier signal (i.e., the frequency conversion process of the signal by the up-conversion module and the down-conversion module) and the coherent forwarding of the slave end (i.e., the ranging slave board). Both links involve phase locking.

[0021] For the frequency synthesizer, let the input signal of the frequency synthesizer (that is, the output signal of the constant temperature crystal oscillator) S in (t) is:

[0022] S in (t)=sin(2πf in t+θ)#(3)

[0023] Among them, f in is the frequency of the input signal, θ is the initial phase of the input signal, and t is the time.

[0024] In theory, the output signal of the frequency synthesizer is for:

[0025]

[0026] Among them, f out The frequency of the frequency synthesizer output signal.

[0027] Since the internal core of the frequency synthesizer is a phase-locked loop module, when the phase-locked loop tracks the input signal, the phase locked by the phase-locked loop is not necessarily 2πf under ideal conditions due to the uncertainty of the initial conditions of the phase-locked loop and the existence of integer ambiguity in the input signal. in t+θ, but 2πf in t+θ+2nπ, where n is a natural number, then the actual output signal of the frequency synthesizer is:

[0028]

[0029] when When is an integer, It can be ignored, so no matter what value n takes, the initial phase value of the actual output signal of the frequency synthesizer is when When is not an integer, It cannot be ignored that the initial phase value of the actual output signal of the frequency synthesizer is Because the initial conditions and lock time of the phase-locked loop are uncertain, the initial phase value of the phase-locked loop output signal cannot be determined each time the system restarts, causing the carrier phase measurement value to jump. To avoid this phenomenon, the output frequency of the frequency synthesizer can be set to an integer multiple of the input frequency.

[0030] In addition to the carrier phase jump issues that may be introduced by the frequency synthesizer, the slave forwarding architecture can also cause carrier phase jumps. The slave utilizes a digital phase-locked loop (DPLL) to coherently forward the received signal. This DPLL locks and tracks the received signal in the same way as the PLL in the frequency synthesizer, leading to the same cause. To address the carrier phase jump issues introduced by the slave forwarding architecture, the slave's transmit frequency should be an integer multiple of the receive frequency.

[0031] After properly adjusting the output frequency of the frequency synthesizer and the coherent forwarding ratio of the slave board, the steps of the high-precision absolute distance measurement method based on this system are as follows:

[0032] 1) After power on, the ranging mainboard generates a digital intermediate frequency signal, which is then converted to the default frequency f after digital / analog conversion. m The high-frequency carrier ranging signal is sent out through the main end transmitting antenna (i.e. the transmitting antenna connected to the ranging main board);

[0033] 2) The ranging receiving end of the ranging slave board receives the received frequency f m The high-frequency microwave ranging signal is down-converted, analog-to-digital converted, and phase-locked to obtain the phase of the received signal; the coherent forwarding part of the ranging slave board forwards the locked received signal to generate a digital intermediate frequency ranging signal, and the phase ratio is maintained during the forwarding process as the coherent forwarding ratio k; the digital intermediate frequency ranging signal is up-converted to the default frequency point f after digital-to-analog conversion. s And send out the high-frequency carrier ranging signal through the slave transmitting antenna (i.e. the transmitting antenna connected to the ranging slave board);

[0034] 3) The ranging receiving end of the ranging mainboard receives the received frequency f s After down-conversion, analog-to-digital conversion, and phase-locked tracking of the high-frequency microwave ranging signal, the received signal is compared with the local reference signal to obtain the phase difference between the received signal and the local reference signal; the phase difference is averaged and then sent to the PC for processing via the Universal Asynchronous Receiver Transmitter (UART);

[0035] 4) Use GNSS / pseudo-code to measure the rough distance between the master antenna and the slave antenna and transmit the rough distance value to the PC. This rough distance value can be combined with the phase difference output by the ranging motherboard to obtain the final accurate distance value;

[0036] 5) Use the phase difference output by the ranging mainboard and the rough distance value obtained by GNSS / pseudo-code measurement to solve and calculate, and finally obtain the unambiguous absolute distance value.

[0037] Based on the basic carrier phase measurement theory, the absolute distance between two points can be expressed as follows:

[0038]

[0039] Where c is the microwave propagation speed, τ is the round-trip transmission delay of the microwave signal between the master antenna and the slave antenna, is the phase difference including ambiguity, is the phase difference without ambiguity obtained by comparing the received signal of the ranging mainboard with the local reference signal, f s The frequency of the signal transmitted from the ranging board is N, which is a natural number and can be expressed as follows:

[0040]

[0041] Among them, L G is the rough distance between two points measured using GNSS / pseudocode. is the floor symbol.

[0042] The rough distance L between two points measured by GNSS / pseudocode G The phase difference without ambiguity obtained by comparing the received signal of the ranging mainboard with the local reference signal By combining them, we can get the exact distance value L between the two points, which is expressed as follows:

[0043]

[0044] At the same time, to ensure the accuracy of L, the rough distance value L between the two points obtained by GNSS / pseudocode measurement G Accuracy δL G It must be better than one quarter of the equivalent wavelength of the high-frequency ranging carrier emitted by the ranging slave board, that is:

[0045]

[0046] Compared with the traditional fixed-point absolute distance measurement system, the main improvements of the present invention are:

[0047] 1) Integer ratio frequency coherent forwarding is adopted. Through frequency planning and coherent signal forwarding, the initial phase jump problem of the two-way forwarding architecture is solved, and the design of the absolute distance measurement system is completed.

[0048] 2) The dual-pass forwarding architecture eliminates frequency source (oven-controlled crystal oscillator) errors at the slave end, reducing the introduction of system error sources. Compared with the dual-one-pass architecture, there is no need to add time stamps to the phase measurement values ​​at both ends of the ranging process for simultaneous processing, reducing the complexity of the overall structure.

[0049] 3) The hardware structure of the master and slave ends is basically the same, and different center frequencies can be obtained by adjusting a few filters, reducing the complexity and cost of the system.

[0050] 4) Using microwaves as the measurement carrier is less susceptible to environmental interference than rangefinder instruments that use lasers, ultrasonic waves, etc. as carriers; and the propagation attenuation of microwaves is small, which significantly improves the ranging range. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic structural diagram of a high-precision absolute distance measurement system provided by one embodiment of the present invention;

[0052] Figure 2 A schematic diagram of a phase measurement principle of a two-way forwarding structure provided by one embodiment of the present invention;

[0053] Figure 3 A phase transfer flow chart provided in accordance with an embodiment of the present invention;

[0054] Figure 4 This is the block diagram of the phase zero jump test structure;

[0055] Figure 5 This is the result diagram of the phase zero value jump of the frequency synthesizer with non-integer frequency multiplication;

[0056] Figure 6 This is the result diagram of the phase zero value jump of the fractional ratio forwarding from the slave end;

[0057] Figure 7 This is a diagram showing the result of solving the phase zero value stabilization problem after the phase zero value jump in one embodiment of the present invention. DETAILED DESCRIPTION

[0058] The technical solution of the present invention is described in further detail below with reference to the accompanying drawings.

[0059] like Figure 1 As shown, a high-precision absolute distance measurement system based on microwave coherent forwarding, provided by one embodiment of the present invention, mainly includes: two oven-controlled crystal oscillators for generating a reference frequency; two transmitting antennas for transmitting ranging signals; and two receiving antennas for receiving ranging signals. The ranging main board is connected to one oven-controlled crystal oscillator, which is used to generate a high-frequency microwave ranging signal and transmit the signal to the ranging slave board via the transmitting antenna connected to it. At the same time, the high-frequency microwave ranging signal transmitted by the ranging slave board is received via the receiving antenna connected to it, the ranging data is analyzed and processed, and the processed ranging data is transmitted to a universal asynchronous receiver transmitter (UART). The ranging slave board is connected to another oven-controlled crystal oscillator, which is used to receive the high-frequency microwave ranging signal transmitted by the ranging main board via the receiving antenna connected to it, generate a high-frequency microwave ranging signal at another frequency point after integer multiple coherent forwarding, and transmit the signal to the ranging main board via the transmitting antenna connected to it. The universal asynchronous receiver transmitter (UART) is used to transmit the ranging data from the ranging main board to a PC, and the PC completes the final data analysis.

[0060] like Figure 2 As shown, an embodiment of the present invention provides a high-precision absolute distance measurement system based on microwave coherent forwarding, which uses a two-way forwarding architecture to perform high-precision carrier phase measurement. The specific workflow of the two-way forwarding architecture is as follows: 1) After powering on, the ranging main board generates a digital intermediate frequency signal, which is up-converted to the default frequency of 2160 MHz after digital-to-analog conversion, and the high-frequency carrier ranging signal is transmitted through the master-end transmitting antenna; 2) The ranging slave board performs down-conversion, analog-to-digital conversion, and phase-locked tracking on the received high-frequency microwave ranging signal at a frequency of 2160 MHz, and then forwards the tracked signal phase in an integer ratio to generate a digital intermediate frequency signal. The digital intermediate frequency signal is up-converted to the default frequency of 6480 MHz after digital-to-analog conversion, and the high-frequency carrier ranging signal is transmitted through the slave-end transmitting antenna; 3) The ranging main board performs down-conversion, analog-to-digital conversion, and phase-locked tracking on the received high-frequency microwave ranging signal at a frequency of 6480 MHz, and then compares the received signal with a local reference signal to obtain a high-precision carrier phase measurement value.

[0061] like Figure 3 As shown in Figure 2, due to the spatial transmission delay of the signal, the signal phase between the master and slave ends satisfies the following relationship:

[0062]

[0063] Among them, τ is the time required for the carrier to travel between the master and slave ends, Respectively represent the sending signal phase and receiving signal phase of the master end, They represent the phase of the transmitted signal and the phase of the received signal at the slave end, respectively. Since the slave end coherently forwards the signal transmitted from the master end, that is, the slave end first uses a phase-locked loop to track the phase of the master end's transmitted signal, and then forwards the phase proportionally according to the coherent forwarding ratio k, the phase of the transmitted signal and the phase of the received signal at the slave end can be expressed as follows:

[0064]

[0065] Substituting equations (10) and (8) into equation (9), we can obtain the relationship between the phase of the master-side received signal and the phase of the transmitted signal:

[0066]

[0067] The current master-side reference signal phase is Theoretically, by comparing it with the phase of the signal received by the master end, the carrier phase with whole-cycle ambiguity can be obtained:

[0068]

[0069] Among them, fm 、f s are the transmitting frequencies of the master and slave ends respectively. In fact, since the sinusoidal carrier signal has 2π ambiguity, the phase obtained by the master end is The part of the carrier phase that is less than 2π after removing the full cycle.

[0070] Based on the basic carrier phase measurement theory, the absolute distance between two points can be expressed as follows:

[0071]

[0072] Where c is the microwave propagation speed, is the phase difference including ambiguity, is the phase difference without ambiguity obtained by comparing the received signal of the ranging mainboard with the local reference signal. N is a natural number and can be expressed as follows:

[0073]

[0074] Among them, L G The rough distance between two points obtained by GNSS / pseudocode measurement. is the floor symbol.

[0075] The rough distance L between two points measured by GNSS / pseudocode G The phase difference without ambiguity obtained after phase comparison with the ranging mainboard By combining them, we can get the exact distance value L between the two points, which is expressed as follows:

[0076]

[0077] At the same time, to ensure the accuracy of L, the rough distance value L between the two points obtained by GNSS / pseudocode measurement G Accuracy δL G It must be better than one quarter of the equivalent wavelength of the high-frequency ranging carrier emitted by the ranging slave board, that is:

[0078]

[0079] like Figure 4 As shown, based on the present invention, a zero-value jump test can be performed. Figure 1The high-precision absolute distance measurement system structure shown in the figure uses an RF transmission line and attenuator as the transmission path, eliminating the antenna and ambiguity fixing structure (GNSS / pseudocode). Using this zero-value jump structure, the following zero-value jump experiments were performed: 1) Setting the frequency synthesizer output frequency to a decimal multiple of the input frequency, resetting the system multiple times while maintaining all other conditions, and observing the phase zero value; 2) Setting the slave coherent forwarding ratio to a decimal, resetting the system multiple times while maintaining all other conditions, and observing the phase zero value; 3) Setting the frequency synthesizer output frequency to an integer multiple of the input frequency and the slave coherent forwarding ratio to an integer, resetting the system multiple times while maintaining all other conditions, and observing the phase zero value.

[0080] like Figure 5 As shown in the figure, the frequency synthesizer output frequency is set to a decimal multiple of the input frequency. With other conditions remaining the same, the system is reset multiple times to observe the phase zero value. It can be found that when the frequency synthesizer output frequency is set to a decimal multiple of the input frequency, the phase zero value jumps after the system is reset.

[0081] like Figure 6 As shown in the figure, the slave coherent forwarding ratio is set to a decimal. With other conditions remaining the same, the system is reset multiple times to observe the phase zero value. It can be found that when the slave coherent forwarding ratio is set to a decimal, the phase zero value jumps after the system is reset.

[0082] like Figure 7 As shown in FIG. , in one embodiment of the present invention, when the frequency synthesizer output frequency is set to an integer multiple of the input frequency and the slave-end coherent forwarding ratio is set to an integer, and other conditions are consistent, the system is reset multiple times to observe the phase zero value. It is found that when the slave-end coherent forwarding ratio is set to a decimal, the phase zero value does not jump after the system is reset.

[0083] After the overall system is implemented in hardware, the function is tested. After multiple experimental measurements, the present invention achieves sub-millimeter measurement accuracy in kilometer-level distance measurement, and the relative uncertainty of the measurement result is 5um±4×10 -7 L.

Claims

1. A method for using a high-precision absolute distance measurement system based on microwave coherent forwarding, characterized in that: The steps include: 1) After power on, the ranging mainboard generates a digital intermediate frequency signal, which is then up-converted to the default frequency after digital / analog conversion. And send out the high-frequency carrier ranging signal through the transmitting antenna connected to the ranging mainboard; 2) The ranging receiving end of the ranging slave board receives the received frequency The high-frequency microwave ranging signal is down-converted, analog-to-digital converted, and phase-locked to obtain the phase of the received signal; the coherent forwarding part of the ranging slave board forwards the locked received signal to generate a digital intermediate frequency ranging signal, and in the forwarding process, the phase ratio is maintained as the coherent forwarding ratio. ;The digital intermediate frequency ranging signal is up-converted to the default frequency after digital / analog conversion and sends out the high-frequency carrier ranging signal through the transmitting antenna connected to the ranging slave board; 3) The ranging receiving end of the ranging mainboard receives the received frequency After down-conversion, analog-to-digital conversion, and phase-locked tracking of the high-frequency microwave ranging signal, the received signal is compared with the local reference signal to obtain the phase difference between the received signal and the local reference signal; After averaging the phase difference, it is sent to the PC for processing via the Universal Asynchronous Receiver Transmitter (UART); 4) Use GNSS / pseudo-code to measure the rough distance between the antenna of the ranging main board and the antenna of the ranging slave board, and transmit the rough distance value to the PC for processing; 5) Use the phase difference output by the ranging mainboard and the rough distance value obtained by GNSS / pseudo-code measurement to solve and calculate, and finally obtain the unambiguous absolute distance value; Absolute distance value The solution calculation method is as follows: The rough distance between two points measured by GNSS / pseudocode The phase difference without ambiguity obtained by comparing the received signal of the ranging mainboard with the local reference signal Combined to get the exact distance between two points , It is expressed as follows: ， in, is the microwave propagation speed, The frequency of the signal transmitted from the board for ranging.

2. The method for using a high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 1, characterized in that: The rough distance between two points measured by GNSS / pseudo-code Accuracy It must be better than one quarter of the equivalent wavelength of the high-frequency ranging carrier emitted by the ranging slave board, that is: 。 3. A high-precision absolute distance measurement system based on microwave coherent forwarding according to any one of claims 1 to 2, characterized in that: include: Two oven-controlled crystal oscillators for generating reference frequencies; two transmitting antennas for transmitting ranging signals; Two receiving antennas are used to receive ranging signals. The ranging mainboard is connected to a constant temperature crystal oscillator and is used to generate a high-frequency microwave ranging signal and send the signal to the ranging slave board through the transmitting antenna connected to it. At the same time, the high-frequency microwave ranging signal transmitted by the ranging slave board is received through the receiving antenna connected to it, the ranging data is analyzed and processed, and the processed ranging data is transmitted to a universal asynchronous receiver transmitter (UART). The ranging slave board is connected to another constant temperature crystal oscillator and is used to receive the high-frequency microwave ranging signal transmitted by the ranging mainboard through the receiving antenna connected to it, and generate a high-frequency microwave ranging signal of another frequency point after integer multiple coherent forwarding, and send the signal to the ranging mainboard through the transmitting antenna connected to it. The universal asynchronous receiver transmitter (UART) is used to transmit the ranging data of the ranging mainboard to a PC, and the PC completes the final data analysis.

4. The high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 3, characterized in that: The ranging mainboard includes a ranging transmitting end part, a ranging receiving end part and a ranging data processing and sending part, wherein: The ranging transmitter part includes: a digital intermediate frequency signal generation module, which is used to generate a digital intermediate frequency signal based on a constant temperature crystal oscillator; a digital / analog conversion module, which converts the digital intermediate frequency signal into an analog intermediate frequency signal; and an up-conversion module, which up-converts the analog intermediate frequency signal to the default frequency point. ; The ranging receiver part includes: a down-conversion module, which down-converts the high-frequency microwave ranging signal to an analog intermediate frequency; an analog / digital conversion module, which converts the analog intermediate frequency signal into a digital intermediate frequency signal; a phase-locked loop module, which locks and outputs the phase of the signal received by the ranging mainboard according to the digital intermediate frequency signal; The ranging data processing and sending part includes: an average processing module, which performs average processing on the phase data output by the ranging mainboard; a data sending module, which sends the ranging data after average processing to the PC through the universal asynchronous receiver and transmitter (UART); The ranging slave board includes a ranging receiving end part and a coherent forwarding part, wherein, The ranging receiver part includes: a down-conversion module, which down-converts the high-frequency microwave ranging signal to an analog intermediate frequency; an analog / digital conversion module, which converts the analog intermediate frequency signal into a digital intermediate frequency signal; a phase-locked loop module, which locks and outputs the phase of the ranging slave board receiving signal according to the digital intermediate frequency signal; The coherent forwarding part includes: a coherent module that forwards the locked received signal to generate a digital intermediate frequency signal, and maintains the phase ratio relationship as the coherent forwarding ratio during the forwarding process. ; Digital / Analog conversion module, converts digital intermediate frequency digital signal into analog intermediate frequency signal; up-conversion module, up-converts analog intermediate frequency signal to the default frequency point .

5. The high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 4, characterized in that: The ranging transmitting end part and the ranging receiving end part of the ranging main board are in the working state by default, and the ranging data processing and sending part of the ranging main board is in the non-working state by default. When the ranging receiving end part of the ranging main board locks the signal phase, the ranging data processing and sending part of the ranging main board automatically changes to the working state; the ranging receiving end part and the coherent forwarding part of the ranging slave board are in the working state by default.

6. The high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 4, characterized in that: Coherent forwarding ratio is a positive integer, and .

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