High-precision absolute distance measurement system based on microwave coherent forwarding

Abstract

The 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, adopts a two-way forwarding distance measurement architecture, and obtains a high-precision stable phase measurement value by using a high-frequency band two-way forwarding architecture and integral multiple coherent forwarding. And a final absolute distance measurement result can be obtained after the GNSS / pseudo code is used for fixing the ambiguity. After the whole system is realized through hardware, function actual measurement is carried out. After multiple experimental measurements, the measurement precision of submillimeter level can be achieved in kilometer-level distance measurement, and the relative uncertainty of the measurement result is 5 [mu] m + / -4 * 10 <-7 > L.

Description

Technical Field

[0001] The 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 is also developing. 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. Reasonable selection of measurement tools and measurement methods in different environments can effectively reduce measurement costs and improve measurement efficiency.

[0004] At present, the commonly used distance measurement methods include laser rangefinder, infrared rangefinder, ultrasonic rangefinder and microwave rangefinder. Different types of distance measurement instruments have their own advantages and disadvantages. In terms of field applications, laser rangefinders have high accuracy and large range (the measurement range is from tens of meters to more than ten kilometers), but they are not safe for human eyes and are easily affected by the environment. In rainy, snowy or dusty environments, the measurement accuracy and range of laser rangefinders will be greatly reduced; although infrared rangefinders are safe for human eyes, they have poor measurement accuracy and small range, and are as easily affected by the environment as laser rangefinders; ultrasonic rangefinders have simple hardware and low cost, but they have low accuracy and small range, and are easily affected by environmental factors such as temperature, humidity and airflow. Therefore, for field environments, there is an urgent need for a fixed-point absolute distance measurement system and method with high accuracy, large range and not easily affected by the environment. Summary of the invention

[0005] The present invention provides a high-precision absolute distance measurement system based on microwave coherent forwarding. The system adopts a two-way forwarding architecture and uses an integer multiple coherent forwarding method to solve the problem of initial phase uncertainty in the two-way forwarding architecture; combined with GNSS / pseudo-code fixed ambiguity, high-precision absolute distance measurement between two fixed points is achieved. It has been verified in practice that the present invention can achieve sub-millimeter ranging accuracy in kilometer-level distance measurement.

[0006] On the one hand, the present invention provides a high-precision absolute distance measurement system based on microwave coherent forwarding, which adopts 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 containing ambiguity; combines GNSS / pseudo-code to fix the ambiguity, and completes the measurement of the high-precision absolute distance between two fixed points.

[0007] The system specifically comprises: two constant temperature 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 main board is connected to a constant temperature crystal oscillator for generating a high-frequency (S band) microwave ranging signal and sending the signal to a ranging slave board through the transmitting antenna connected thereto, and receiving the high-frequency microwave ranging signal transmitted by the ranging slave board through the receiving antenna connected thereto, analyzing and processing the ranging data, and transmitting the processed ranging data to a universal asynchronous receiver and transmitter (UART); the ranging slave board is connected to another constant temperature crystal oscillator for receiving the high-frequency microwave ranging signal transmitted by the ranging main board through the receiving antenna connected thereto, generating a high-frequency microwave ranging signal of another frequency point after integer multiple coherent forwarding, and sending the signal to the ranging main board through the transmitting antenna connected thereto; the universal asynchronous receiver and transmitter (UART) is used to transmit the ranging data of the ranging main board to a PC, 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; an up-conversion module, which up-converts the analog intermediate frequency signal to a default frequency point f m ;

[0010] The ranging receiving end 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: a mean processing module, which performs mean 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 mean processing to the PC through a universal asynchronous receiver and transmitter (UART);

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

[0013] The ranging receiving end 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 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 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 working state by default, and the ranging data processing and sending part of the ranging main board is in 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 working state; the ranging receiving end part and the coherent forwarding part of the ranging slave board are in working state by default.

[0016] In the system, the ranging main board and the ranging slave board use exactly the same hardware structure, and only different filters are replaced according to the default frequency points of their respective transmission and reception. The default frequency point of the ranging transmission of the ranging main board is f m , the default frequency of ranging reception is f s , and the default frequency of the ranging slave board is f s , the default frequency of 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; and 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, combines the two-way forwarding architecture in the high-frequency band with the integer multiple coherent forwarding method, obtains high-precision, stable phase measurement data containing ambiguity; and uses GNSS / pseudocode to fix the ambiguity, thereby obtaining the final high-precision absolute distance measurement value.

[0019] In the process of using the two-way forwarding architecture to measure the carrier phase, the uncertainty of the phase zero value is a key problem. Specifically, when the measured distance remains unchanged, the carrier phase measurement value obtained after each power-on or reset of the system will jump, which seriously limits the application of carrier phase measurement in high-precision absolute distance measurement. To address this problem, the following will analyze the problem from the perspective of signal generation, signal transmission, and forwarding processes.

[0020] In 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 (i.e. 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 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, can be ignored, then 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 Since the initial conditions of the phase-locked loop are uncertain and the locking time is also uncertain, the initial phase value of the phase-locked loop output signal cannot be determined each time the system is restarted, resulting in a jump in the carrier phase measurement value. 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 problem that may be introduced by the frequency synthesizer, the slave forwarding architecture may also cause the carrier phase jump phenomenon. The slave uses a digital phase-locked loop in the process of coherent forwarding of the received signal. The digital phase-locked loop locks and tracks the received signal in the same way as the phase-locked loop in the frequency synthesizer, so the cause of the problem is also the same. In order to solve the carrier phase jump problem introduced in the slave forwarding architecture, the transmission frequency of the slave should be an integer multiple of the receiving 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 powering on, the ranging mainboard generates a digital intermediate frequency signal, which is then up-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, phase-locked and tracked 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 The high-frequency carrier ranging signal is sent out through the transmitting antenna at the slave end (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, phase-locked tracking and other operations on 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 through the universal asynchronous receiver and transmitter (UART);

[0035] 4) Use GNSS / pseudo-code to measure the rough distance value between the master antenna and the slave antenna and transmit the rough distance value to the PC. The rough distance value can be subsequently processed together with the phase difference output by the ranging mainboard 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] According to the basic measurement theory of carrier phase, 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, N is a natural number, which can be expressed as follows:

[0040]

[0041] Among them, L G is the rough distance between two points measured using GNSS / pseudocode. 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 Combined, 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 of δL G It needs to 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) By adopting integer ratio frequency coherent forwarding, the problem of initial phase jump in the two-way forwarding architecture is solved through frequency planning and coherent signal forwarding, and the design of the absolute distance measurement system is completed.

[0048] 2) By adopting a two-way forwarding architecture, the slave end will not introduce frequency source (oven-controlled crystal oscillator) error, reducing the introduction of system error sources; compared with the dual one-way structure, there is no need to add time stamps to the phase measurement values ​​at both ends of the ranging 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 only 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 distance measuring 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 diagram of the structure 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 an embodiment of the present invention;

[0053] Figure 3 A phase transfer flow chart provided for one embodiment of the present invention;

[0054] Figure 4 It is the structural block diagram of phase zero value jump test;

[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 a diagram showing the result of the phase zero value jump when forwarding fractional ratio 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 further described in detail below in conjunction with the accompanying drawings.

[0059] like Figure 1 As shown, a high-precision absolute distance measurement system based on microwave coherent forwarding is provided as an embodiment of the present invention, mainly comprising: two constant temperature crystal oscillators for generating reference frequencies; two transmitting antennas for transmitting ranging signals; two receiving antennas for receiving ranging signals; a ranging main board is connected to a constant temperature crystal oscillator, for generating high-frequency microwave ranging signals and sending the signals to the ranging slave board through the transmitting antenna connected thereto, and receiving the high-frequency microwave ranging signals transmitted by the ranging slave board through the receiving antenna connected thereto, analyzing and processing the ranging data, and transmitting the processed ranging data to a universal asynchronous receiver transmitter (UART); the ranging slave board is connected to another constant temperature crystal oscillator, for receiving the high-frequency microwave ranging signals transmitted by the ranging main board through the receiving antenna connected thereto, and generating high-frequency microwave ranging signals of another frequency point after integer multiple coherent forwarding, and sending the signals to the ranging main board through the transmitting antenna connected thereto; the universal asynchronous receiver transmitter (UART) is used to transmit the ranging data of the ranging main board to a PC, and the PC completes the final data analysis.

[0060] like Figure 2 As shown, a high-precision absolute distance measurement system based on microwave coherent forwarding provided by an embodiment of the present invention adopts a two-way forwarding architecture to perform high-precision carrier phase measurement. The specific working process of the two-way forwarding architecture is as follows: 1) after startup, the ranging main board generates a digital intermediate frequency signal, which is up-converted to a default frequency of 2160 MHz after digital / analog conversion, and the high-frequency carrier ranging signal is sent out through the master end transmitting antenna; 2) after the ranging slave board performs down-conversion, analog / digital conversion, phase-locked tracking and other operations on the received high-frequency microwave ranging signal with a frequency of 2160 MHz, the tracked signal phase is forwarded in an integer ratio to generate a digital intermediate frequency signal, the digital intermediate frequency signal is up-converted to a default frequency of 6480 MHz after digital / analog conversion, and the high-frequency carrier ranging signal is sent out through the slave end transmitting antenna; 3) after the ranging main board performs down-conversion, analog / digital conversion, phase-locked tracking and other operations on the received high-frequency microwave ranging signal with a frequency of 6480 MHz, the received signal is compared with the local reference signal to obtain a high-precision carrier phase measurement value.

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

[0062]

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

[0064]

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

[0066]

[0067] The phase of the reference signal at the master end is Theoretically, by comparing it with the phase of the signal received by the master end, the carrier phase with integer 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 a 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] According to the basic measurement theory of carrier phase, 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, It 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 measured by GNSS / pseudocode. The floor symbol.

[0075] The rough distance L between two points measured by GNSS / pseudocode G The phase difference without ambiguity obtained after comparing with the ranging mainboard Combined, 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 of δL G It needs to 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 the RF transmission line and attenuator as the transmission path, and removes the antenna and ambiguity fixed structure (GNSS / pseudocode). Using this zero-value jump structure, the following zero-value jump experiments are performed: 1) Set the frequency synthesizer output frequency to a decimal multiple of the input frequency, reset the system multiple times under the same conditions, and observe the phase zero value; 2) Set the slave end coherent forwarding ratio to a decimal, reset the system multiple times under the same conditions, and observe the phase zero value; 3) Set the frequency synthesizer output frequency to an integer multiple of the input frequency, and the slave end coherent forwarding ratio to an integer, reset the system multiple times under the same conditions, and observe 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. When other conditions are the same, the system is reset several 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, and the system is reset multiple times under the same other conditions 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 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, the system is reset multiple times under the same other conditions to observe the phase zero value. It can be found that when the slave end coherent forwarding ratio is set to a decimal, the phase zero value will 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 high-precision absolute distance measurement system based on microwave coherent forwarding, characterized in that: include: Two constant temperature crystal oscillators for generating reference frequencies; two transmitting antennas for transmitting ranging signals; Two receiving antennas are used to receive ranging signals; the ranging main board is connected to a constant temperature crystal oscillator, 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, and at the same time, the high-frequency microwave ranging signal emitted 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 and transmitter (UART); the ranging slave board is connected to another constant temperature crystal oscillator, used to receive the high-frequency microwave ranging signal emitted by the ranging main board 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 main board through the transmitting antenna connected to it; the universal asynchronous receiver and transmitter (UART) is used to transmit the ranging data of the ranging main board to a PC, and the PC completes the final data analysis.

2. A high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 1, characterized in that: The distance measurement main board includes a distance measurement transmitting end part, a distance measurement receiving end part and a distance measurement 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; an up-conversion module, which up-converts the analog intermediate frequency signal to a default frequency point f m ; The ranging receiving end 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 a universal asynchronous receiver and transmitter (UART); The ranging slave board includes a ranging receiving end part and a coherent forwarding part, wherein: The ranging receiving end 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 receiving signal according to the digital intermediate frequency signal; 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 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 .

3. The high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 2, characterized in that: The ranging transmitting end part and the ranging receiving end part of the ranging main board are in working state by default, and the ranging data processing and sending part of the ranging main board is in 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 working state by default.

4. The high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 2, characterized in that: The coherent forwarding ratio k is a positive integer, and f s = k·f m .

5. A method for using a high-precision absolute distance measurement system based on microwave coherent forwarding as claimed in any one of claims 1 to 4, characterized in that: The steps include: 1) After powering on, the ranging mainboard generates a digital intermediate frequency signal, which is then up-converted to the default frequency f after digital / analog conversion. m 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 f m The high-frequency microwave ranging signal is down-converted, analog-to-digital converted, and phase-locked and tracked 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 sends out a high-frequency carrier ranging signal through a transmitting antenna connected to the ranging slave board; 3) The ranging receiving end of the ranging mainboard receives the received frequency f s After down-conversion, analog / digital conversion, and phase-locked tracking operations are performed on 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 a PC for processing via a universal asynchronous receiver / transmitter (UART); 4) Using GNSS / pseudo-code to measure the rough distance value between the antenna of the ranging main board part and the antenna of the ranging slave board part, and transmitting 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.

6. The method for using a high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 5, characterized in that: The calculation method for solving the absolute distance value L of 5) is as follows: 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 Combined, we get the exact distance value L between the two points, which is expressed as follows: Where c is the microwave propagation speed, f s The frequency at which the slave board transmits the signal for ranging.

7. The method for using a high-precision absolute distance measurement system based on microwave coherent forwarding according to claim 6, characterized in that: The rough distance L between two points measured by GNSS / pseudocode G Accuracy of δL G It needs to be better than one quarter of the equivalent wavelength of the high-frequency ranging carrier emitted by the ranging slave board, that is:

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