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

Abstract

The application discloses a ground absolute microwave ranging method and system based on double-path echo and RTK differential measurement, which can apply carrier phase ranging to absolute ranging. The system adopts RTK differential measurement to solve the phase integer ambiguity, especially simultaneously differentiates the observation values of two ends of the ranging main terminal, solves the extra error introduced by the traditional RTK double difference in the two-point transfer differential value, and finally compensates the error by using an atmospheric refraction correction structure model, so that the sub-millimeter level precision is achieved under the kilometer level measurement distance.

Description

Technical Field

[0001] The present 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] Ground distance measurement methods can be categorized by the measurement medium into mechanical, optical, and microwave distance measurement. Mechanical distance measurement uses instruments such as vernier calipers and micrometers. This method offers intuitive measurement methods and clearly defined error sources, but it also has a limited measurement limit. With the growing demand for high-precision, long-range measurements in industrial production, optical and microwave distance measurement have become the mainstream distance measurement methods.

[0003] Optical ranging is widely used in high-precision measurement due to its high accuracy, strong resistance to electromagnetic interference, and strong transmission capabilities. For example, combining nanometer-wavelength interferometry with superheterodyne detection schemes can perform absolute distance measurements over tens of meters with an accuracy of up to 1ppm. Emerging femtosecond optical frequency comb technology can achieve nanometer-level accuracy within meter-level ranges. However, optical ranging has strict requirements for manufacturing and operating conditions, resulting in high equipment and maintenance costs.

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

[0005] Generally speaking, precision spread spectrum ranging methods are used to measure distances on the order of hundreds of meters with centimeter-level errors. Radar ranging primarily utilizes FMCW modulation, pulse modulation, frequency-modulated continuous wave (FMCW), phase modulation, Doppler modulation, and code division multiple access (CDMA) modulation. FMCW and CDMA radars have centimeter-level ranging accuracy, while pulse modulation radars can achieve decimeter-level accuracy. Doppler modulation radars are not used directly for ranging, but primarily for measuring the target's velocity relative to the radar. Phase modulation offers the highest accuracy, reaching millimeter-level precision. However, research in the field of high-precision absolute ground-based microwave ranging is currently limited. Summary of the Invention

[0006] To address the above problems, the present invention provides a ground-based absolute microwave ranging method and system based on two-way echo and RTK differential measurement. This method uses a two-way echo ranging system with heterogeneous integer-ratio coherent forwarding as its core, combines it with RTK differential measurement for integer ambiguity resolution, and uses a field atmospheric refraction correction structure to eliminate errors, thereby achieving high-precision measurement of the ground-based absolute ranging system. It has been proven that submillimeter accuracy can be achieved in kilometer-level measurements.

[0007] The technical scheme adopted by the present application is as follows:

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

[0009] S1. A carrier signal and a reference carrier signal are generated at the first measuring point, the carrier signal is pre-processed to obtain a forward signal, and the forward signal is sent to the second measuring point through a transmitting antenna;

[0010] S2. The forward signal is received at the second measuring point, the forward signal is processed to obtain a forward baseband signal, and a local carrier signal consistent with the carrier component of the forward baseband signal is generated locally;

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

[0012] S4. The echo signal is received at the first measuring point, the echo signal is processed to obtain an echo baseband signal, the phase of the echo baseband signal is compared with the phase of the reference carrier signal, and a phase difference value is obtained;

[0013] S5. The position parameters of the first measuring point and the second measuring point are obtained through a global navigation satellite system (GNSS), RTK differential operation is performed on the position parameters at the first measuring point and the second measuring point, a coarse measurement value of the measuring point distance is obtained, phase integer resolution is performed according to the phase difference value, and an accurate value of the measuring point distance is obtained;

[0014] S6. The accurate value of the measuring point distance is corrected according to the atmospheric refraction index, and an absolute distance measurement result between the first measuring point and the second measuring point is obtained.

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

[0016] Further, step S2 is specifically: the forward signal is received at the second measuring point, a local signal is generated through a local oscillator, the forward signal is down-converted to a baseband signal twice to obtain a forward baseband signal, the phase difference between the forward baseband signal and the local signal is detected by using a phase-locked loop, the local signal is adjusted, and a local carrier signal consistent with the phase of the forward baseband signal is generated.

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

[0018] Furthermore, 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.

[0019] Furthermore, 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 from the same group of navigation satellites through corresponding GNSS antennas, and the signals are decoded to obtain the 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, that is, the RTK double difference operation is used to weaken the influence of the 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 based on the phase difference value to obtain the precise 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 high-precision carrier ranging to obtain the accurate 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 is less than 2π, and L r It is the precise 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 includes: acquiring temperature, pressure, and humidity data at different points between the first measuring point and the second measuring point, calculating the atmospheric refractive index based on the temperature, pressure, and humidity data, and then calculating the actual microwave propagation speed to correct the accurate distance value. The atmospheric refractive index n is calculated as follows: Where P is the air pressure, T is the temperature, and 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 transmit RF link is used to up-convert the carrier signal twice to a high-frequency signal and send it through the transmit antenna, which is recorded as the forward signal;

[0030] a second receiving RF link, configured 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 a phase difference between a forward baseband signal and a local oscillator signal using a phase-locked loop, and generate a local carrier signal having a phase consistent with the forward baseband signal;

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

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

[0034] A first receiving RF 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 aids in deambiguation, performing differential calculations on the position parameters of the first and second measuring points to obtain a rough distance measurement. It then performs phase integer calculations based on the phase change value to obtain the precise distance value.

[0038] Atmospheric refraction correction algorithm auxiliary module, 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. This invention employs a two-way echo structure with integer-ratio, frequency-coherent forwarding, ensuring that the frequency multiplication ratio of the frequency-synthesizing phase-locked loop at the echo end is an integer. This method effectively addresses the zero-value variation phenomenon, enabling carrier phase ranging to be successfully applied to absolute ranging.

[0041] 2. The present invention adopts a differential RTK assisted measurement structure in which the master end simultaneously performs differential RTK on data with the same time stamp at both ends. The signals of a group of satellites are observed simultaneously at the first and second measuring points to obtain the signal transmission time and pseudo-code distance from the two receivers to each satellite. These observations are differentially processed to form a single difference. The single difference between the first and second measuring points is then differentiated to obtain the distance between the first and second measuring points, i.e., a rough measurement of the measuring point distance. The phase is then resolved with the phase difference obtained from the carrier ranging to determine the phase integer cycle.

[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 sub-millimeter level. The present invention can be applied to long-distance ranging scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is an 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 This is a hardware implementation block diagram of the ground microwave absolute ranging system in an 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 distance measurement with atmospheric correction in an embodiment of the present invention.

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

[0048] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be noted that the following examples are intended to facilitate 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 uses integer ratio heterogeneous frequency coherent forwarding two-way echo technology to achieve high-precision ground absolute distance measurement. It also uses a combination of RTK differential and two-way echo architecture, uses the high-frequency two-way echo architecture to obtain phase measurement data, and uses the RTK differential method to fix the ambiguity to obtain the absolute distance measurement result. Then, an atmospheric refraction correction structure is used to reduce the atmospheric error, ultimately obtaining a high-precision absolute distance measurement result. The specific steps are as follows:

[0051] S1 generates a carrier signal and a reference carrier signal at the first measuring point, preprocesses the carrier signal, obtains a forward signal, and transmits the forward signal to the second measuring point through the transmitting antenna;

[0052] S2 receives the forward signal at the second measuring point, processes the forward signal to obtain a forward baseband signal, and locally generates a local carrier signal 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 receives the echo signal at the first measuring point, processes the echo signal to obtain an echo baseband signal, compares the phase of the echo baseband signal with the reference carrier signal, and obtains the phase difference;

[0055] S5. Obtain the position parameters of the first and second measuring points using the Global Navigation Satellite System (GNSS), perform RTK differential calculations on the position parameters at the first and second measuring points, and obtain a rough value of the distance between the measuring points with millimeter-level accuracy; then perform phase integer calculations based on the phase difference to obtain the precise value of the distance between the measuring points;

[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, with the accuracy improved to the sub-millimeter level.

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

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

[0059] Further, in the step S3, the local carrier signal is forwarded through integer frequency offset coherent transmission, which is specifically: using a frequency synthesis phase-locked loop structure to lock the frequency within a locking frequency range and generate a carrier signal with an integer multiple of the frequency of the local carrier signal. If the local carrier signal is not within the locking frequency range of the phase-locked loop, the phase-locked loop will lose lock and the forwarding step cannot be performed.

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

[0061] Further, in the step S5, the position parameters of the first measuring point and the second measuring point are obtained through a global navigation satellite system (GNSS), and RTK differential operation is performed on the position parameters of the first measuring point and the second measuring point to obtain a coarse measurement value of the distance between the measuring points, which is specifically: setting a GNSS receiver at each of the first measuring point and the second measuring point, receiving signals of the same set of navigation satellites through corresponding GNSS antennas, decoding the signals to obtain the signal transmission time and pseudo-code distance of each navigation satellite for the two GNSS receivers, performing differential processing on the signal transmission time and pseudo-code distance of each navigation satellite to form a single-difference value for each navigation satellite, and then performing differential processing on the single-difference values of two satellite signals at the same point, i.e., using RTK double-difference operation to weaken the influence of ionospheric and tropospheric delay errors, and finally obtaining a coarse measurement value of the distance between the first measuring point and the second measuring point with a precision of millimeters.

[0062] Further, in the step S5, the phase difference value is used for phase ambiguity resolution to obtain an accurate distance value between the measuring points, which is specifically: using the coarse measurement value of the distance between the measuring points to resolve the phase difference value to obtain an integer value, and inputting the integer value into a high-precision carrier ranging distance calculation formula to obtain an accurate distance value. The coarse measurement value D of the distance between the first measuring point and the second measuring point is GNSS The calculation formula is:

[0063]

[0064] The integer value N obtained by resolving the ambiguity is a :

[0065]

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

[0067]

[0068] Wherein λ is the microwave wavelength, Δφ is the part of the carrier change less than 2π, L r is the precise value of the distance between the first measuring point and the second measuring point, and floor represents the down rounding of the data in the formula.

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

[0070]

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

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

[0073]

[0074] Embodiment 2

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

[0076] As Figure 1 shown, the ground absolute microwave ranging system of the embodiment adopts a double-pass echo measurement system, the echo end retransmission ratio is an integer ratio, the first measuring point and the second measuring point simultaneously perform GNSS positioning, RTK differential measurement and ambiguity resolution; the refraction index is acquired by using a sensor, and finally the atmospheric refraction correction of the distance value is performed.

[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 the carrier signal generated by the FPGA at the first measuring point up 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 the forward signal received by the receiving antenna down to the baseband; the transmitting radio frequency link at the second measuring point, which is used to mix the ranging signal forwarded by the FPGA at the second measuring point up 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, The system is used to receive high-frequency ranging echo signals. The receiving RF link at the first measurement point is used to down-mix the echo signal received by the receiving antenna to baseband to obtain phase information. The ultrastable crystal oscillator module provides a unified reference time standard for the two-way echo ranging system. The GNSS antenna is used to receive signals from navigation satellites. The GNSS receiver receives weak radio signals from the satellite through the antenna, tracks the frequency and phase of the received signal, decodes the signal, processes the decoded signal, and calculates its own position, thereby obtaining the position parameters at the first and second measurement points. The precision measurement unit is used to measure temperature, humidity, and air pressure parameters at different points along the measurement line. Furthermore, in the transmitting RF link, the FPGA integrated control board generates a low-frequency carrier signal. After the carrier signal passes through the corresponding mixer, filter, mixer, filter, and amplifier, the signal is up-converted to the ranging frequency band and transmitted 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 to obtain a low-frequency signal, which is then passed to the phase-locked loop for frequency locking.

[0078] The software algorithm design for the first measurement 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 signal reception; 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 for the second measurement 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 auxiliary unblurring module performs difference operation on the position parameters at the first measuring point and the second measuring point to obtain a coarse measurement value of the measuring point distance, and then performs phase whole cycle resolution on the phase difference value obtained by carrier ranging.

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

[0082] The application adopts the integer ratio heterodyne coherent repeating double-path echo structure, the hardware structures at the first measuring point and the second measuring point are completely same, only the frequency synthesis phase-locked loop at the second measuring point realizes heterodyne repeating, 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 transmitting frequency at the second measuring point is N*f r , and N is an integer.

[0083] As shown in Figure 2 , the hardware design of the first measuring point and the second measuring point keeps the integer ratio of the transmitting and receiving frequencies, the circuit designs of the mixers, filters and the like are same, and the first measuring point and the second measuring point both have GNSS receiving antennas. The hardware design includes: the first measuring point transmitting radio frequency link, which is used for twice up-mixing the baseband signal generated by the frequency source to a high frequency ranging signal; the second measuring point transmitting antenna, which is used for transmitting the absolute ranging signal generated at the first measuring point, that is, the forward signal; the second measuring point receiving antenna, which is used for receiving the forward signal transmitted from the first measuring point; the second measuring point receiving link, which is used for twice down-conversion of the received forward signal by using the mixers and digital ADCs; the second measuring point transmitting link, which is used for up-conversion of the echo end ranging signal to a high frequency echo signal, and the circuit structure at the first measuring point is similar; the first measuring point receiving antenna, which is used for receiving the echo signal, and the second measuring point receiving antenna is consistent; and the first measuring point receiving link, which is consistent with the circuit structure at the second measuring point, down-converts the echo end ranging signal to a base frequency, and then compares the phase with the original signal.

[0084] As shown in Figure 3 , the RTK differential measurement auxiliary unblurring flowchart of the embodiment, the specific flow is that the GNSS RTK differential positioning and double-path echo ranging are simultaneously performed at the first measuring point and the second measuring point, and the differential measurement coarse measurement result is: ambiguity N a can be resolved as: The final ranging result is: Wherein, D GNSS is the coarse measurement value obtained by the GNSS differential positioning, lambda is the microwave wavelength, Delta phi is the part less than 2pi of the carrier change, N a is the multiple of 2pi of the carrier phase change, and L ris the precise measurement value obtained by GNSS differential positioning auxiliary carrier ranging, and floor is the data down rounding in the formula.

[0085] As shown in the flow chart of the embodiment for correcting the precise measurement value obtained by atmospheric refraction ground microwave ranging. Figure 4 The atmospheric refraction module is composed of a precise measurement unit, a data transmission module and a central computing unit. The central computing unit sends a sampling instruction at a fixed interval. After the measurement unit receives the instruction, it 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 refraction index n. According to the atmospheric refraction index calculation formula, where P is the air pressure, T is the temperature, e w is the humidity (water vapor partial pressure), and the ranging result is corrected to obtain L r

[0086] As shown in the flow chart of the embodiment for correcting the precise measurement value obtained by atmospheric refraction ground microwave ranging. Figure 5 The hardware circuit diagram of the present application is shown in the figure. In order to solve the integer ratio frequency coherent repeating double-pass echo system of the application, RTK differential measurement is used to solve the integer ambiguity and atmospheric refraction correction structure for error compensation. The hardware includes GNSS receiving antenna, GNSS receiver, FPGA hardware platform, precise measurement unit and central processing unit. The ranging algorithm in the present application is realized by using hardware description language VHDL, and the ISE software of Xilinx company is used to burn the chip used in the system.

[0087] The key technology of the present application is to use the RTK architecture of differential measurement to assist the integer ratio frequency coherent repeating double-pass echo ground absolute ranging, 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 carrier signals and reference carrier signals at the first measurement point. The carrier signals are passed through a mixer, a filter, etc., and after two times of up-conversion, a high-frequency forward signal is obtained. The forward signal is sent to the second measurement point through the transmitting antenna.

[0089] The forward signal is received at the second measurement point. After the forward signal passes through an amplifier, a filter, a mixer and a digital ADC, it becomes a forward baseband signal after two times of down-conversion. A local carrier signal consistent with the carrier component of the forward baseband signal is generated locally.

[0090] The local carrier signal is subjected to integer frequency ratio coherent repeating. After the repeated carrier signal is subjected to two times of up-conversion through a mixer and a filter, a high-frequency echo signal is obtained. The echo signal is sent to the first measurement point through the transmitting antenna.

[0091] ​An echo signal is received at the first measuring point. The echo signal is down-converted twice through an amplifier, a filter, a mixer, and a digital ADC to obtain an echo baseband signal. The phase of the echo baseband signal is compared with the reference carrier signal to obtain a phase difference value.

[0092] The position parameters of the first and second measuring points are obtained through the Global Navigation Satellite System (GNSS). RTK differential calculations are performed on the position parameters of the first and second measuring points to obtain a rough value of the measuring point distance. Then, the phase integer ambiguity is resolved based on the phase difference 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 and second measuring points. 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 at the time of 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 traditional microwave ranging systems. RTK differential measurement is used to assist in integer ambiguity resolution, which can improve ranging accuracy. At the same time, the influence of atmospheric refraction on ranging error is taken into account and corrected in combination with the atmospheric refraction model, so that the measurement accuracy is improved to the submillimeter 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 scope of protection 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 for measuring the distance between a first measuring point and a second measuring point includes the following steps: S1 generates a carrier signal and a reference carrier signal at the first measuring point, preprocesses the carrier signal, obtains a forward signal, and transmits the forward signal to the second measuring point through the transmitting antenna; S2 receives the forward signal at the second measuring point, processes the forward signal to obtain a forward baseband signal, and locally generates a local carrier signal 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 receives the echo signal at the first measuring point, processes the echo signal to obtain an echo baseband signal, compares the phase of the echo baseband signal with the reference carrier signal, and obtains the phase difference; S5. Obtain the position parameters of the first and second measuring points through the Global Navigation Satellite System (GNSS), perform RTK differential calculations on the position parameters of the first and second measuring points to obtain a rough value of the distance between the measuring points; then perform a phase integer solution based on the phase difference to obtain an accurate value of the distance between the measuring points; S6. Correct the precise value of the distance between the measuring points according to the atmospheric refractive index to obtain an 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, 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, characterized in that: In step S3, the local carrier signal is coherently forwarded with an integer frequency ratio, specifically by using a frequency synthesis phase-locked loop structure to lock the frequency within a locked frequency range and generate a carrier signal with a frequency that is an integer multiple of the local carrier signal frequency.

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 the 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 from 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 based on 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: A rough measurement of the distance between the first measuring point and the second measuring point The calculation formula is: , The integer value obtained by defuzzification for: , The distance calculation formula of the carrier ranging is: ,in is the microwave wavelength, Insufficient carrier variation part, It is the precise 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 8, 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 based on the temperature, air pressure, and humidity data. The atmospheric refractive index n is calculated using the following formula: ,in is the air pressure, T is the temperature, is humidity; the absolute distance measurement result between the first measuring point and the second measuring point 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 and second measuring points, including: The carrier generation module is used to set the carrier frequency and amplitude and generate the carrier signal and the reference carrier signal; The first transmit RF link is used to up-convert the carrier signal twice to a high-frequency signal and send it through the transmit antenna, which is recorded as the forward signal; a second receiving RF link, configured 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; a second carrier tracking and locking module, configured to detect a phase difference between a forward baseband signal and a local oscillator signal using a phase-locked loop, and generate a local carrier signal having a phase consistent with the forward baseband signal; Integer ratio frequency coherent forwarding module, used to forward the local carrier signal at an integer multiple of the frequency; The second transmitting RF link is used to up-convert the forwarded local carrier signal twice to a high-frequency signal and send it through the transmitting antenna, which is recorded as an echo signal; A first receiving RF 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 aids in deambiguation, performing differential calculations on the position parameters of the first and second measuring points to obtain a rough distance measurement. It then performs phase integer calculations based on the phase change value to obtain the precise distance value. Atmospheric refraction correction algorithm auxiliary module, used to correct the precise distance value according to the atmospheric refraction index.

Images