Ground absolute microwave distance measurement method and system based on two-way echo and RTK differential measurement

Abstract

The invention discloses a ground absolute microwave distance measurement method and system based on two-way echo and RTK differential measurement. Carrier phase distance measurement can be applied to absolute distance measurement. The system adopts RTK differential measurement to carry out phase integer calculation, and particularly, difference is carried out on simultaneous calibration values at two ranging ends at a ranging main end, so that an extra error introduced by transmitting a differential value at two points in the traditional RTK double difference is solved; and finally, the system carries out error compensation by using an atmospheric refraction correction structure model, and the submillimeter precision is achieved under a kilometer-level measurement distance.

Description

Technical Field

[0001] The invention belongs to the field of ground microwave absolute ranging, and relates to a ground absolute microwave ranging method and system, and in particular to a ground absolute microwave ranging method and system based on two-way echo and RTK differential measurement. Background Art

[0002] The ground distance measurement method can be divided into mechanical distance measurement, optical distance measurement and microwave distance measurement according to the measurement medium. Mechanical distance measurement uses instruments such as vernier calipers and micrometers. This method has an intuitive measurement method and a clear error source, but the upper limit of measurement is relatively short. With the growing demand for high-precision and long-range measurements in industrial production, optical distance measurement and microwave distance measurement have begun to become the mainstream distance measurement methods.

[0003] Optical ranging is widely used in the field of high-precision measurement due to its high accuracy, strong anti-electromagnetic interference ability and strong transmission capability. For example, the combination of nanometer wavelength interferometry and superheterodyne detection scheme can perform absolute distance measurement within a range of tens of meters with an accuracy of up to 1ppm; the emerging femtosecond optical frequency comb technology can achieve nanometer-level accuracy within a meter-level range. However, optical ranging has strict requirements for manufacturing and operating conditions, and the equipment cost and maintenance cost are relatively expensive.

[0004] Microwave ranging is generally used in aerospace measurement and control, autonomous navigation, airport navigation, radar ranging and other fields, and the measurement distance is long. For example, Chinese patent document with publication number CN103954937A discloses a design method for a wide range and high precision microwave ranging radar system. Chinese patent document with publication number CN114488108A discloses a microwave rangefinder.

[0005] Generally speaking, the precision spread spectrum ranging method is used to measure the length of hundreds of meters, and the error is at the centimeter level; radar ranging mainly uses FMCW modulation, pulse modulation, frequency modulated continuous wave, phase modulation, Doppler modulation, code division multiple access modulation, etc. Among them, the ranging accuracy of FMCW radar and code division multiple access radar is at the centimeter level, and the pulse modulation radar can reach the decimeter level. Doppler modulation radar is not directly used for ranging, but is mainly used to measure the speed of the target relative to the radar. Phase modulation ranging has the highest accuracy and can reach millimeter level accuracy. However, in the field of ground microwave high-precision absolute ranging, there are still few related studies. Summary of the invention

[0006] To solve the above problems, the present invention provides a ground absolute microwave ranging method and system based on two-way echo and RTK differential measurement. The two-way echo ranging system with heterogeneous integer ratio coherent forwarding is taken as the core, and RTK differential measurement is combined to perform integer ambiguity resolution. The field atmospheric refraction correction structure is used to eliminate errors, so as to realize high-precision measurement of the ground absolute ranging system. It has been verified that sub-millimeter accuracy can be achieved in kilometer-level measurement.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A ground absolute microwave ranging method based on two-way echo and RTK differential measurement is used to measure the distance between a first measuring point and a second measuring point, comprising the following steps:

[0009] S1. Generate a carrier signal and a reference carrier signal at the first measuring point, pre-process the carrier signal to obtain a forward signal, and send the forward signal to the second measuring point through the transmitting antenna;

[0010] S2. receiving a forward signal at a second measuring point, processing the forward signal to obtain a forward baseband signal, and generating a local carrier signal locally that is consistent with the carrier component of the forward baseband signal;

[0011] S3. The local carrier signal is coherently forwarded with an integer frequency ratio, the forwarded carrier signal is processed to obtain an echo signal, and the echo signal is sent to the first measuring point through the transmitting antenna;

[0012] S4. Receiving an echo signal at the first measuring point, processing the echo signal to obtain an echo baseband signal, comparing the phase of the echo baseband signal with the reference carrier signal, and obtaining a phase difference;

[0013] S5. Obtain the position parameters of the first measuring point and the second measuring point through the global navigation satellite system GNSS, perform RTK differential operation on the position parameters at the first measuring point and the second measuring point to obtain a rough value of the measuring point distance; then perform phase integer solution according to the phase difference value to obtain an accurate value of the measuring point distance;

[0014] S6. Correct the precise value of the distance between the measuring points according to the atmospheric refractive index to obtain the absolute distance measurement result between the first measuring point and the second measuring point.

[0015] Furthermore, in step S1, the carrier signal is preprocessed, specifically: the carrier signal is up-converted twice to a high-frequency signal.

[0016] Furthermore, step S2 is specifically as follows: receiving a forward signal at a second measuring point, generating a local signal through a local oscillator, down-converting the forward signal to a baseband signal twice to obtain a forward baseband signal, using a phase-locked loop to detect a phase difference between the forward baseband signal and the local signal, adjusting the local signal, and generating a local carrier signal whose phase is consistent with the forward baseband signal.

[0017] Furthermore, in step S3, the local carrier signal is coherently forwarded with an integer frequency ratio, specifically: a frequency synthesis phase-locked loop structure is used to lock the frequency within a locked frequency range, and a carrier signal with a frequency that is an integer multiple of the local carrier signal frequency is generated.

[0018] Further, in step S3, the forwarded carrier signal is processed by up-converting the forwarded carrier signal twice to a high-frequency signal; in step S4, the echo signal is processed to obtain an echo baseband signal, specifically, the echo signal is down-converted twice to obtain an echo baseband signal.

[0019] Further, in step S5, the position parameters of the first measuring point and the second measuring point are obtained through the global navigation satellite system GNSS, and RTK differential operation is performed on the position parameters at the first measuring point and the second measuring point to obtain a rough measurement value of the measuring point distance, specifically: GNSS receivers are respectively set at the first measuring point and the second measuring point, and the two GNSS receivers receive signals of the same group of navigation satellites through corresponding GNSS antennas, and the signals are decoded to obtain signal transmission time and pseudo code distance from the two GNSS receivers to each navigation satellite, and the signal transmission time and pseudo code distance of each navigation satellite are differentially processed to form a single difference value of each navigation satellite, and then the single difference values ​​of the two navigation satellite signals are differentially processed at the same point, that is, RTK double difference operation is used to weaken the influence of ionospheric and tropospheric delay errors, and finally a rough measurement value of the distance between the first measuring point and the second measuring point is obtained with an accuracy of millimeter level.

[0020] Furthermore, in step S5, the phase integer solution is performed according to the phase difference value to obtain the precise value of the measuring point distance, specifically: the phase difference value is defuzzified using the rough measured value of the measuring point distance to obtain the integer value, and the integer value is brought into the distance calculation formula of the high-precision carrier ranging to obtain the precise distance value.

[0021] Furthermore, the rough measured value D of the distance between the first measuring point and the second measuring point GNSS The calculation formula is:

[0022]

[0023] The integer value N obtained by defuzzification a for:

[0024] The distance calculation formula of the carrier ranging is: Where λ is the microwave wavelength, Δφ is the part of the carrier wave that changes by less than 2π, and L r It is the precise measured value of the distance between the first measuring point and the second measuring point. Floor means rounding down the data in the formula.

[0025] Furthermore, in step S6, the atmospheric refractive index acquisition step is: obtaining the temperature, air pressure, and humidity data at different points between the first measuring point and the second measuring point, calculating the atmospheric refractive index according to the temperature, air pressure, and humidity data, and then calculating the actual microwave propagation speed, and correcting the precise distance value. The atmospheric refractive index n calculation formula is: Where P is the air pressure, T is the temperature, e w is humidity; the absolute distance measurement result L between the first measuring point and the second measuring point r The calculation formula is:

[0026]

[0027] A ground absolute microwave ranging system based on two-way echo and RTK differential measurement, comprising:

[0028] The carrier generation module is used to set the carrier frequency and amplitude, and generate the carrier signal and the reference carrier signal;

[0029] The first transmitting radio frequency link is used to up-convert the carrier signal twice to a high-frequency signal and send it through a transmitting antenna, which is recorded as a forward signal;

[0030] A second receiving radio frequency link is used to receive a forward signal through a receiving antenna and down-convert the forward signal twice to a baseband signal to obtain a forward baseband signal;

[0031] A second carrier tracking and locking module, configured to detect the difference between the phase of the forward baseband signal and the phase of the local oscillator signal using a phase locking loop, and generate a local carrier signal consistent with the phase of the forward baseband signal;

[0032] Integer ratio frequency coherent forwarding module, used to forward the local carrier signal at an integer multiple frequency;

[0033] The second transmitting radio frequency link is used to up-convert the forwarded local carrier signal twice into a high-frequency signal and send it through the transmitting antenna, which is recorded as an echo signal;

[0034] A first receiving radio frequency link is used to receive the echo signal through the receiving antenna, and down-convert the echo signal twice to a baseband signal to obtain an echo baseband signal;

[0035] A first carrier tracking and locking module, used to lock the echo baseband signal;

[0036] A phase comparison module is used to compare the echo baseband signal with the reference carrier signal to obtain a phase change value;

[0037] The double-difference RTK algorithm-assisted deambiguation module is used to perform differential calculation on the position parameters at the first measuring point and the second measuring point to obtain a rough measurement value of the measuring point distance; then perform phase integer calculation based on the phase change value to obtain an accurate distance value;

[0038] The atmospheric refraction correction algorithm auxiliary module is used to correct the precise distance value according to the atmospheric refraction index.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention adopts a two-way echo structure with integer ratio frequency-different coherent forwarding, so that the frequency multiplication ratio of the frequency synthesis phase-locked loop at the echo end is an integer. This method effectively solves the zero value variation phenomenon, so that the carrier phase ranging can be successfully applied to absolute ranging.

[0041] 2. The present invention adopts a differential RTK auxiliary measurement structure for data with the same time scale at both ends at the master end, observes signals of a group of satellites at the first measuring point and the second measuring point at the same time, obtains the signal transmission time and pseudo code distance from the two receivers to each satellite, performs differential processing on these observation values, forms a single difference, and then performs differential processing on the single difference value of the first measuring point and the second measuring point to obtain the distance between the first measuring point and the second measuring point, that is, the rough measurement value of the measuring point distance, and then performs phase integer solution with the phase difference value obtained by carrier ranging.

[0042] 3. The present invention uses an atmospheric refraction correction structure to correct the distance result value, takes the influence of atmospheric refraction into account in microwave ranging, improves the measurement accuracy, and makes the accuracy reach the sub-millimeter level. The present invention can be applied to long-distance ranging scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The overall architecture diagram of a ground absolute microwave ranging system based on two-way echo and RTK differential measurement in an embodiment of the present invention.

[0044] Figure 2 The hardware implementation block diagram of the ground microwave absolute ranging system in the embodiment of the present invention.

[0045] Figure 3 This is a flow chart of RTK differential measurement assisted deambiguation in an embodiment of the present invention.

[0046] Figure 4 This is a flow chart of the atmospheric correction distance measurement in an embodiment of the present invention.

[0047] Figure 5 FIG. 4 is a diagram of the measured hardware of the ranging system in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0049] Example 1

[0050] A ground absolute microwave ranging method based on two-way echo and RTK differential measurement, using integer ratio heterogeneous frequency coherent forwarding two-way echo technology to achieve high-precision ground absolute distance measurement, and using the combination of RTK differential and two-way echo architecture, using the high-frequency two-way echo architecture to obtain phase measurement data, and using the RTK differential method to fix the ambiguity, and then obtain the absolute distance measurement result, and then use the atmospheric refraction correction structure to reduce the atmospheric error, and finally obtain a high-precision absolute distance measurement result. The specific steps are as follows:

[0051] S1. Generate a carrier signal and a reference carrier signal at the first measuring point, pre-process the carrier signal to obtain a forward signal, and send the forward signal to the second measuring point through the transmitting antenna;

[0052] S2. receiving a forward signal at a second measuring point, processing the forward signal to obtain a forward baseband signal, and generating a local carrier signal locally that is consistent with the carrier component of the forward baseband signal;

[0053] S3. The local carrier signal is coherently forwarded with an integer frequency ratio, the forwarded carrier signal is processed to obtain an echo signal, and the echo signal is sent to the first measuring point through the transmitting antenna;

[0054] S4. Receiving an echo signal at the first measuring point, processing the echo signal to obtain an echo baseband signal, comparing the phase of the echo baseband signal with the reference carrier signal, and obtaining a phase difference;

[0055] S5. Obtain the position parameters of the first measuring point and the second measuring point through the global navigation satellite system GNSS, perform RTK differential operation on the position parameters at the first measuring point and the second measuring point, and obtain a rough value of the measuring point distance with an accuracy of millimeters; then perform phase integer solution according to the phase difference value to obtain the precise value of the measuring point distance;

[0056] S6. The precise value of the distance between the measuring points is corrected according to the atmospheric refractive index to obtain the absolute distance measurement result between the first measuring point and the second measuring point, and the accuracy is improved to the sub-millimeter level.

[0057] Furthermore, in step S1, the carrier signal is preprocessed, specifically: the carrier signal is up-converted twice to a high-frequency signal.

[0058] Furthermore, step S2 is specifically as follows: receiving a forward signal at a second measuring point, generating a local signal through a local oscillator, down-converting the forward signal to a baseband signal twice to obtain a forward baseband signal, using a phase-locked loop to detect a phase difference between the forward baseband signal and the local signal, adjusting the local signal, and generating a local carrier signal whose phase is consistent with the forward baseband signal.

[0059] Furthermore, in step S3, the local carrier signal is coherently forwarded with an integer frequency ratio, specifically: a frequency synthesis phase-locked loop structure is used to lock the frequency within the locked frequency range, and a carrier signal with a frequency that is an integer multiple of the local carrier signal frequency is generated. If the local carrier signal is not within the locked frequency range of the phase-locked loop, the forwarding step cannot be performed after the phase-locked loop loses lock.

[0060] Further, in step S3, the forwarded carrier signal is processed by up-converting the forwarded carrier signal twice to a high-frequency signal; in step S4, the echo signal is processed to obtain an echo baseband signal, specifically, the echo signal is down-converted twice to obtain an echo baseband signal.

[0061] Further, in step S5, the position parameters of the first measuring point and the second measuring point are obtained through the global navigation satellite system GNSS, and RTK differential operation is performed on the position parameters at the first measuring point and the second measuring point to obtain a rough measurement value of the measuring point distance, specifically: GNSS receivers are respectively set at the first measuring point and the second measuring point, and the two GNSS receivers receive signals of the same group of navigation satellites through corresponding GNSS antennas, and the signals are decoded to obtain signal transmission time and pseudocode distance from the two GNSS receivers to each navigation satellite, and the signal transmission time and pseudocode distance of each navigation satellite are differentially processed to form a single difference value of each navigation satellite, and then the single difference values ​​of the two satellite signals are differentiated at the same point, that is, RTK double difference operation is used to weaken the influence of ionospheric and tropospheric delay errors, and finally a rough measurement value of the distance between the first measuring point and the second measuring point is obtained with an accuracy of millimeter level.

[0062] Further, in step S5, the phase integer solution is performed according to the phase difference value to obtain the accurate value of the measuring point distance, specifically: the phase difference value is defuzzified using the rough measured value of the measuring point distance to obtain the integer value, and the integer value is brought into the distance calculation formula of the high-precision carrier ranging to obtain the accurate distance value. The rough measured value D of the distance between the first measuring point and the second measuring point GNSS The calculation formula is:

[0063]

[0064] The integer value N obtained by defuzzification a for:

[0065]

[0066] The distance calculation formula of the carrier ranging is:

[0067]

[0068] Where λ is the microwave wavelength, Δφ is the part of the carrier wave that changes by less than 2π, and L r It is the precise measured value of the distance between the first measuring point and the second measuring point. Floor means rounding down the data in the formula.

[0069] In step S6, the atmospheric refractive index acquisition step is: using a sensor to acquire temperature, air pressure, and humidity data at different points between the first measuring point and the second measuring point, and calculating the atmospheric refractive index n according to the temperature, air pressure, and humidity data. The atmospheric refractive index n calculation formula is:

[0070]

[0071] Where P is the air pressure, T is the temperature, e w It is humidity;

[0072] The absolute distance measurement result L between the first measuring point and the second measuring point r The calculation formula is:

[0073]

[0074] Example 2

[0075] A ground absolute microwave ranging system based on two-way echo and RTK differential measurement has been field tested in a baseline field in Hangzhou.

[0076] like Figure 1 As shown, the ground absolute microwave ranging system of this embodiment adopts a two-way echo measurement system, the forwarding ratio of the echo end is an integer ratio, the first measuring point and the second measuring point are simultaneously GNSS positioned, RTK differential measurement and ambiguity resolution are performed; the refractive index is obtained through the sensor, and finally the atmospheric refraction correction is performed on the distance value.

[0077] Specifically, the ground absolute microwave ranging system of the present invention includes hardware design and software design. The ranging system hardware mainly includes: a transmitting radio frequency link at the first measuring point, which is used to mix up the carrier signal generated by the FPGA at the first measuring point to the transmitting frequency and transmit it through the transmitting antenna; the transmitting antenna at the first measuring point, which is used to send the forward signal after up-mixing; the receiving antenna at the second measuring point, which is used to receive the forward signal; the receiving radio frequency link at the second measuring point, which is used to mix down the forward signal received by the receiving antenna to the baseband; the transmitting radio frequency link at the second measuring point, which is used to mix up the ranging signal forwarded by the FPGA at the second measuring point to the transmitting frequency and transmit it through the transmitting antenna; the transmitting antenna at the second measuring point, which is used to send the ranging echo signal after up-mixing; the receiving antenna at the first measuring point, Used to receive high-frequency ranging echo signals; the receiving RF link at the first measuring point is used to mix the echo signal received by the receiving antenna down to the baseband to obtain phase information; the ultra-stable crystal oscillator module provides a unified reference time standard for the two-way echo ranging system; the GNSS antenna is used to receive the signal of the navigation satellite; the GNSS receiver receives the weak radio signal sent by the satellite through the antenna, tracks the frequency and phase of the received signal and decodes the signal, processes the decoded signal, calculates its own position, that is, obtains the position parameters at the first measuring point and the second measuring point; the precision measurement unit is used to measure the temperature, humidity, and air pressure parameters at different points of the measuring line. Further, in the transmitting RF link, the FPGA integrated control board generates a low-frequency carrier signal, and the carrier signal passes through the corresponding mixer, filter, mixer, filter, and amplifier in sequence, and then the signal is up-converted to the ranging frequency band and sent through the transmitting antenna; in the receiving RF link, after the receiving antenna receives the signal, it passes through the corresponding amplifier, mixer, filter, amplifier, and ADC in sequence to obtain a low-frequency signal, which is then passed to the phase-locked loop for frequency locking.

[0078] The software algorithm design of the first measuring point includes: a carrier generation module, which is used to generate a stable carrier signal and a reference carrier signal to provide a basis for subsequent transmission; a carrier tracking and locking module, which uses a phase-locked loop to detect the difference between the phase of the received echo signal and the phase of the local oscillator signal, and generates a signal that is consistent with the phase of the echo signal to ensure accurate reception of the signal; a phase comparison module, which compares the received signal with the phase of the local reference carrier to obtain the carrier ranging value.

[0079] The software algorithm design of the second measuring point includes: a carrier tracking and locking module, which uses a phase-locked loop to detect the difference between the phase of the received forward signal and the phase of the local oscillator signal, and generates a local carrier signal that is consistent with the phase of the forward signal to ensure the accuracy of the received signal; an integer ratio frequency difference module, which is used to generate a signal that is different from the carrier signal frequency and has an integer ratio relationship.

[0080] The double-difference RTK algorithm assists in the deambiguation module, which performs differential calculation on the position parameters at the first and second measuring points to obtain a rough measurement value of the measuring point distance, and then performs phase integer solution with the phase difference value obtained by the carrier ranging.

[0081] The atmospheric refraction correction algorithm auxiliary module is used to calculate the atmospheric refraction index n under different temperatures, air pressures, and humidity and calculate the actual microwave propagation speed, and correct the distance value of the measurement path.

[0082] The present invention adopts a two-way echo structure of integer ratio heterodyne coherent forwarding. The hardware structure at the first measuring point and the second measuring point is exactly the same, except that the frequency synthesis phase-locked loop at the second measuring point realizes heterodyne forwarding, and the transmitting and receiving frequencies have a specific integer ratio relationship, that is, the transmitting ranging frequency at the first measuring point is f r , the transmission frequency at the second measuring point is N×f r , N is an integer.

[0083] like Figure 2 As shown, the hardware design of this embodiment maintains an integer ratio between the transmitting and receiving frequencies of the first measuring point and the second measuring point, and the circuit designs of the mixer, filter, etc. are the same. The first measuring point and the second measuring point both have GNSS receiving antennas. Its hardware design includes: a transmitting RF link at the first measuring point, which is used to up-mix the baseband signal generated by the frequency source twice to a high-frequency ranging signal; a transmitting antenna at the second measuring point, which is used to send the absolute ranging signal generated at the first measuring point - the forward signal; a receiving antenna at the second measuring point, which is used to receive the forward signal transmitted from the first measuring point; a receiving link at the second measuring point, which uses the mixer and the forward signal received by the digital ADC to perform two down-conversions; a transmitting link at the second measuring point, which is used to up-convert the echo end ranging signal to a high-frequency echo signal, which is similar to the circuit structure at the first measuring point; a receiving antenna at the first measuring point, which is used to receive the echo signal, which is consistent with the receiving antenna at the second measuring point; a receiving link at the first measuring point, which is consistent with the circuit structure at the second measuring point, down-converts the echo end ranging signal to the baseband, and then compares the phase with the original signal.

[0084] like Figure 3 As shown in the flowchart of RTK differential measurement assisted deambiguation in this embodiment, the specific process is that GNSS RTK differential positioning and two-way echo ranging are performed at both ends of the first measuring point and the second measuring point at the same time, and the rough measurement result of the differential measurement is: Fuzziness N a It can be solved as: The final ranging result is: Where D GNSS is the rough value obtained by GNSS differential positioning, λ is the microwave wavelength, Δφ is the part of the carrier change that is less than 2π, and N a is a multiple of 2π of carrier phase change, L rIt is the precise value obtained by GNSS differential positioning assisted carrier ranging, and floor is the data in the formula rounded down.

[0085] like Figure 4 As shown in FIG. 1 , the flow chart of the precise measurement value obtained by ground microwave ranging by atmospheric refraction correction in this embodiment. The atmospheric refraction module is composed of a precision measurement unit, a data transmission module and a central computing unit. The central computing unit sends sampling instructions at fixed intervals. After receiving the instructions, the measurement unit collects data and transmits the data directly to the central computing unit through the data transmission module. The central computing unit processes and calculates the transmitted data and finally obtains the atmospheric refractive index n. According to the atmospheric refractive index calculation formula, Where P is the air pressure, T is the temperature, e w is the humidity (water vapor partial pressure), and the distance measurement result is corrected to obtain L r for:

[0086] like Figure 5 The hardware circuit diagram of the present invention is shown. In order to compensate for the error of the integer ratio frequency-independent coherent forwarding two-way echo system of the invention, RTK differential measurement is used to solve the integer ambiguity and atmospheric refraction correction structure. The hardware includes a GNSS receiving antenna, a GNSS receiver, an FPGA hardware platform, a precision measurement unit and a central processing unit. The ranging algorithm in the present invention is implemented using the hardware description language VHDL and burned into the chip used in the system using the ISE software of Xilinx.

[0087] The key technology of the present invention is to use the RTK architecture of differential measurement to assist the two-way echo ground absolute distance measurement of integer ratio heterogeneous frequency coherent forwarding, and then use the atmospheric refraction correction structure to correct the error. The measurement steps are as follows:

[0088] After the ranging starts, the carrier generation module generates a carrier signal and a reference carrier signal at the first measuring point, passes the carrier signal through a mixer, a filter, etc., and after two up-conversions, a high-frequency forward signal is obtained, and the forward signal is sent to the second measuring point through the transmitting antenna;

[0089] A forward signal is received at the second measuring point. The forward signal passes through an amplifier, a filter, a mixer and a digital ADC, and is converted into a forward baseband signal after two down-conversions. A local carrier signal consistent with the carrier component of the forward baseband signal is generated locally.

[0090] The local carrier signal is coherently forwarded with an integer frequency ratio, and the forwarded carrier signal is twice up-converted through a mixer, a filter, etc. to obtain a high-frequency echo signal, and the echo signal is sent to the first measuring point through a transmitting antenna;

[0091] An echo signal is received at a first measuring point, and an echo baseband signal is obtained after the echo signal is down-converted twice through an amplifier, a filter, a mixer, and a digital ADC, and a phase difference value is obtained by comparing the phase of the echo baseband signal with that of a reference carrier signal;

[0092] The position parameters of the first and second measuring points are obtained through the global navigation satellite system GNSS, and the position parameters at the first and second measuring points are subjected to RTK differential operation to obtain a rough value of the measuring point distance; then, the phase integer ambiguity is resolved according to the phase difference value to obtain the precise value of the measuring point distance; the differential measurement result is: Fuzziness N a It can be solved as: The final ranging result is:

[0093]

[0094] The precise value of the distance between the measuring points is corrected according to the atmospheric refractive index to obtain the absolute distance measurement result between the first measuring point and the second measuring point. Specifically, when using two-way echo ranging, humidity, temperature and air pressure sensors are placed between the two measuring points to collect meteorological data. After the ranging is completed, the data is processed to obtain the atmospheric refractive index n during the ranging. The refractive index is calculated using the formula: Substituting the atmospheric refractive index, the absolute distance between the two points is: After a single measurement is completed, multiple measurements are taken and the average value is obtained through averaging to improve the ranging accuracy.

[0095] In the above method, the two-way echo structure adopts integer frequency coherent forwarding, which can be applied to the field of absolute ranging compared with the traditional microwave ranging system, and uses RTK differential measurement to assist in integer ambiguity resolution, which can improve the ranging accuracy. At the same time, the influence of atmospheric refraction on ranging error is taken into account, and correction is made in combination with the atmospheric refraction model to improve the measurement accuracy to the sub-millimeter level.

[0096] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A ground absolute microwave ranging method based on two-way echo and RTK differential measurement, characterized in that: The method is used to measure the distance between a first measuring point and a second measuring point, comprising the following steps: S1. Generate a carrier signal and a reference carrier signal at the first measuring point, pre-process the carrier signal to obtain a forward signal, and send the forward signal to the second measuring point through the transmitting antenna; S2. receiving a forward signal at a second measuring point, processing the forward signal to obtain a forward baseband signal, and generating a local carrier signal locally that is consistent with the carrier component of the forward baseband signal; S3. The local carrier signal is coherently forwarded with an integer frequency ratio, the forwarded carrier signal is processed to obtain an echo signal, and the echo signal is sent to the first measuring point through the transmitting antenna; S4. Receiving an echo signal at the first measuring point, processing the echo signal to obtain an echo baseband signal, comparing the phase of the echo baseband signal with the reference carrier signal, and obtaining a phase difference; S5. Obtain the position parameters of the first measuring point and the second measuring point through the global navigation satellite system GNSS, perform RTK differential operation on the position parameters at the first measuring point and the second measuring point to obtain a rough value of the measuring point distance; then perform phase integer solution according to the phase difference value to obtain an accurate value of the measuring point distance; S6. Correct the precise value of the distance between the measuring points according to the atmospheric refractive index to obtain the absolute distance measurement result between the first measuring point and the second measuring point.

2. The ground absolute microwave ranging method based on two-way echo and RTK differential measurement according to claim 1 is characterized in that: In step S1, the carrier signal is preprocessed, specifically: the carrier signal is up-converted twice to a high-frequency signal.

3. The ground absolute microwave ranging method based on two-way echo and RTK differential measurement according to claim 1 is characterized in that: Step S2 is specifically as follows: receiving a forward signal at a second measuring point, generating a local signal through a local oscillator, down-converting the forward signal to a baseband signal twice to obtain a forward baseband signal, using a phase-locked loop to detect the phase difference between the forward baseband signal and the local signal, adjusting the local signal, and generating a local carrier signal whose phase is consistent with the forward baseband signal.

4. The ground absolute microwave ranging method based on two-way echo and RTK differential measurement according to claim 1 is characterized in that: In step S3, the local carrier signal is coherently forwarded with an integer frequency ratio, specifically: a frequency synthesis phase-locked loop structure is used to lock the frequency within a locked frequency range, and a carrier signal with a frequency that is an integer multiple of the local carrier signal frequency is generated.

5. The ground absolute microwave ranging method based on two-way echo and RTK differential measurement according to claim 1, characterized in that: In step S3, the forwarded carrier signal is processed, specifically: the forwarded carrier signal is up-converted twice to a high-frequency signal; in step S4, the echo signal is processed to obtain an echo baseband signal, specifically: the echo signal is down-converted twice to obtain an echo baseband signal.

6. The ground absolute microwave ranging method based on two-way echo and RTK differential measurement according to claim 1, characterized in that: In step S5, the position parameters of the first measuring point and the second measuring point are obtained through the global navigation satellite system GNSS, and RTK differential operation is performed on the position parameters at the first measuring point and the second measuring point to obtain a rough measurement value of the measuring point distance. Specifically, GNSS receivers are respectively set at the first measuring point and the second measuring point, and the two GNSS receivers receive signals of the same group of navigation satellites through corresponding GNSS antennas, and the signals are decoded to obtain signal transmission time and pseudo code distance from the two GNSS receivers to each navigation satellite, and the signal transmission time and pseudo code distance of each navigation satellite are differentially processed to form a single difference value of each navigation satellite, and then the single difference value of the two navigation satellite signals is differentially processed at the same point to obtain a rough measurement value of the distance between the first measuring point and the second measuring point.

7. The ground absolute microwave ranging method based on two-way echo and RTK differential measurement according to claim 1, characterized in that: In step S5, the phase integer solution is performed according to the phase difference value to obtain the accurate value of the measuring point distance, specifically: the phase difference value is defuzzified using the rough measurement value of the measuring point distance to obtain the integer value, and the integer value is substituted into the distance calculation formula of the carrier ranging to obtain the accurate distance value.

8. The ground absolute microwave ranging method based on two-way echo and RTK differential measurement according to claim 7, characterized in that: The rough measured value D of the distance between the first measuring point and the second measuring point GNSS The calculation formula is: The integer value N obtained by defuzzification a for: The distance calculation formula of the carrier ranging is: Where λ is the microwave wavelength, Δφ is the part of the carrier wave that changes by less than 2π, and L r It is the precise measured value of the distance between the first measuring point and the second measuring point. Floor means rounding down the data in the formula.

9. The ground absolute microwave ranging method based on two-way echo and RTK differential measurement according to claim 1, characterized in that: In step S6, the atmospheric refractive index acquisition step is: using a sensor to acquire temperature, air pressure, and humidity data at different points between the first measuring point and the second measuring point, and calculating the atmospheric refractive index n according to the temperature, air pressure, and humidity data. The atmospheric refractive index n calculation formula is: Where P is the air pressure, T is the temperature, e w is humidity; the absolute distance measurement result L between the first measuring point and the second measuring point r The calculation formula is:

10. A ground absolute microwave ranging system based on two-way echo and RTK differential measurement, characterized in that: Used to measure the distance between the first measuring point and the second measuring point, including: A carrier generation module, used to set the carrier frequency and amplitude, and generate a carrier signal and a reference carrier signal; The first transmitting radio frequency link is used to up-convert the carrier signal twice to a high-frequency signal and send it through a transmitting antenna, which is recorded as a forward signal; A second receiving radio frequency link is used to receive the forward signal through the receiving antenna and down-convert the forward signal twice to a baseband signal to obtain a forward baseband signal; A second carrier tracking and locking module, configured to detect the difference between the phase of the forward baseband signal and the phase of the local oscillator signal using a phase locking loop, and generate a local carrier signal consistent with the phase of the forward baseband signal; An integer ratio frequency-coherent forwarding module is used to forward the local carrier signal at an integer multiple of the frequency; The second transmitting radio frequency link is used to up-convert the forwarded local carrier signal twice into a high-frequency signal and send it through the transmitting antenna, which is recorded as an echo signal; A first receiving radio frequency link is used to receive the echo signal through the receiving antenna, and down-convert the echo signal twice to a baseband signal to obtain an echo baseband signal; A first carrier tracking and locking module, used to lock the echo baseband signal; A phase comparison module is used to compare the echo baseband signal with the reference carrier signal to obtain a phase change value; The double-difference RTK algorithm-assisted deambiguation module is used to perform differential calculation on the position parameters at the first measuring point and the second measuring point to obtain a rough measurement value of the measuring point distance; then perform phase integer calculation based on the phase change value to obtain an accurate distance value; The atmospheric refraction correction algorithm auxiliary module is used to correct the precise distance value according to the atmospheric refraction index.

Images