Antenna relative phase center error calibration method, electronic device and medium

Abstract

The application discloses an antenna relative phase center error calibration method, electronic equipment and medium. The method can comprise: collecting a plurality of groups of GNSS satellite observations through two antennas respectively; performing epoch-to-epoch and antenna-to-antenna difference on the GNSS satellite observations respectively, and constructing phase center error measurement values of twice difference; through 4-order polynomial expansion, a fitting formula of the phase center error measurement values of twice difference is established; according to the plurality of groups of GNSS satellite observations, the fitting coefficients are solved simultaneously; the fitting coefficients are substituted into the fitting formula, and a calibration result is obtained, which is a model of the relative antenna phase center error. The application utilizes the characteristics that the ambiguity remains unchanged during the receiver continuously locking the satellite signal, adopts the epoch-to-epoch difference to eliminate the ambiguity, and avoids the difficulty in reliable solution of the ambiguity of the low-cost antenna.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of GNSS antenna phase center error calibration, and more particularly to an antenna relative phase center error calibration method, an electronic device and a medium. BACKGROUND

[0002] Antenna phase center error is an error contained in the global navigation satellite system (GNSS) carrier phase observation. The calibration of the antenna phase center error is an important link in satellite navigation data processing, which directly affects the accuracy and reliability of GNSS high-precision positioning. The antenna phase center refers to the equivalent point of the antenna transmitting or receiving signals in a given direction. The position of the antenna phase center changes with the change of the signal incident direction, and the distance between the actual phase center of the received signal and the ideal average phase center is generally referred to as the phase center variation (PCV). In addition, since the installation point of the antenna and the ideal average phase center are usually not consistent, the concept of phase center offset (PCO) is introduced to represent the three-dimensional vector from the antenna installation point to the ideal average phase center. Therefore, the antenna phase center error includes PCO and PCV, that is, the phase center error is the vector sum of PCO and PCV. Of course, the phase center error can also be represented by a unified parameter, that is, the phase center correction (PCC). Directly using PCC has the same effect as using the combination of PCV and PCO.

[0003] In order to eliminate the antenna phase center error in GNSS applications, it is necessary to measure and calibrate it with certain technical means. The process of antenna phase center error calibration is to measure the phase center error of the antenna in multiple signal incident directions by using special equipment in a special calibration site, and then to obtain the values of the phase center error in multiple signal incident directions. Then, by fitting the measured values, the model of the antenna phase center error can be obtained, which can be a function relationship between the phase center error size and the signal incident direction, or a table recording the phase center error size in different directions. In addition, when the accuracy requirement of the antenna phase center error model is not high, or due to the limitation of the satellite receiving conditions, part of the phase center error information in different directions cannot be collected, only the relationship between the phase center error and the elevation angle of the signal incident direction can be calibrated. In this case, the calibrated model is a function relationship between the phase center error and the elevation angle of the signal incident direction, or a table recording the phase center error size in different elevation angles. After the calibration is completed, the model can be stored in the receiver for real-time elimination of the phase bias in the carrier phase observation.

[0004] The common antenna phase center error calibration methods mainly include darkroom calibration method, absolute field calibration method and relative field calibration method. The darkroom calibration method transmits signals to the antenna to be measured in a microwave darkroom that can fully suppress reflected signals, and directly measures the phase center error of the antenna to be measured by measuring the phase deviation of the received signal of the antenna to be measured and the transmitted signal. The absolute field calibration method simultaneously uses a reference antenna and a measured antenna to collect real GNSS satellite signals in an open environment, and then calculates the phase center error of the measured antenna by calculating the phase difference value of the signals received by the two antennas. Another feature of the absolute field calibration is that it uses a calibration robot to accurately adjust the direction of the measured antenna, so that real signals can be incident on the measured antenna from all directions in a short time. The relative field calibration is similar to the absolute field calibration, and the main difference is that it does not use a calibration robot, which has the advantages of easy implementation and very low cost, and the disadvantages of 1) requiring a long time of days for calibration, and 2) since the measured antenna is always in a static state, the data collected in which signal incident directions depend on which directions have visible satellites; therefore, due to the uneven distribution of visible satellites, the relative field calibration method usually only calibrates the relationship between the phase center error and the elevation angle of the signal incident direction.

[0005] For low-cost antennas, due to the low consistency of the phase center error, each antenna must be calibrated separately. In this case, if the existing calibration method is used, it requires high cost (such as building a darkroom, customizing a calibration robot, or purchasing a high-precision antenna as a reference antenna), which is contrary to the original intention of using low-cost antennas.

[0006] Although the relative on-site calibration method is a relatively low-cost calibration method, the traditional method requires the unknown ambiguity parameters in the carrier phase observation to be eliminated by solving the integer ambiguity; considering that the low-cost antenna usually has a large phase center error, if the integer ambiguity is solved, there may be problems such as low success rate or failure to solve the fixed solution, and the traditional relative on-site calibration method is also not suitable for the phase center error calibration of the low-cost antenna.

[0007] At present, it is still necessary to develop an antenna relative phase center error calibration method suitable for low-cost antennas.

[0008] The information disclosed in the background section of the present application is only intended to deepen the understanding of the general background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art. SUMMARY

[0009] The present application provides an antenna relative phase center error calibration method, electronic equipment and medium, which can utilize the characteristics that the ambiguity remains unchanged during the receiver continuously locks the satellite signal, adopt epoch difference to eliminate ambiguity, and avoid the difficulty of reliable solution of ambiguity of low-cost antenna.

[0010] In a first aspect, the present disclosure provides an antenna relative phase center error calibration method, comprising:

[0011] Collecting a plurality of sets of GNSS satellite observations through two antennas respectively;

[0012] Performing epoch difference and antenna difference on the GNSS satellite observations respectively, and constructing phase center error measurement values of twice difference;

[0013] Establishing a fitting formula of the phase center error measurement values of twice difference through 4-order polynomial expansion;

[0014] Solving the fitting coefficients according to the plurality of sets of GNSS satellite observations;

[0015] Substituting the fitting coefficients into the fitting formula to obtain a calibration result, which is a model of relative antenna phase center error.

[0016] Preferably, the phase center error measurement values of twice difference are:

[0017] ,

[0018] wherein, indicates the phase center error measurement values of twice difference, denotes the carrier phase observation, the superscript denotes the satellite number, the subscripts 1, 2 denote the antenna number, the subscripts t1, t2 denote the observed epoch, and p denotes the geometric distance between the satellite and the antenna installation point.

[0019] Preferably, the fitting formula is:

[0020]

[0021] wherein, denotes the twice-differenced phase center error measurement, and a1, a2, a3, a4 denote the fitting coefficients.

[0022] Preferably, the model of the relative antenna phase center error is:

[0023]

[0024] wherein, is the relative phase center error at the elevation angle .

[0025] Preferably, the method further comprises:

[0026] High-precision double-antenna orientation is performed according to the model of the relative antenna phase center error.

[0027] Preferably, the high-precision double-antenna orientation performed according to the model of the relative antenna phase center error comprises:

[0028] After the GNSS observations are collected, the satellite elevation angle is calculated according to the satellite ephemeris;

[0029] The relative phase center error value is calculated and eliminated using the model of the relative phase center error.

[0030] High-precision double-antenna orientation is performed using the corrected carrier phase observation.

[0031] Preferably, before the multiple sets of GNSS satellite observations are collected, the method further comprises:

[0032] Two antennas to be tested are arranged.

[0033] Preferably, the arrangement of the two antennas to be tested comprises:

[0034] Two test points are determined on the calibration site, and the coordinates of the test points are calibrated.

[0035] The two antennas to be tested are arranged horizontally at the two test points, and the orientations of the two antennas are consistent.

[0036] In a second aspect, the embodiments of the present disclosure further provide an electronic device, which comprises:

[0037] ​​a memory storing executable instructions;

[0038] a processor running the executable instructions in the memory to implement the antenna relative phase center error calibration method.

[0039] In a third aspect, the embodiments of the present disclosure further provide a computer readable storage medium storing a computer program, which, when executed by a processor, implements the antenna relative phase center error calibration method.

[0040] The beneficial effects are that:

[0041] The present application does not use a high-precision antenna as a reference antenna in the data collection process, but uses two low-cost antennas as reference antennas; time difference is used in the data processing process to eliminate the integer ambiguity; and finally the relative phase center error of the two low-cost antennas, i.e., the difference of the phase center error in each elevation angle, is solved.

[0042] The method and apparatus of the present application have other characteristics and advantages, which will be apparent from or set forth in the accompanying drawings and the detailed description that follows, which together serve to explain certain principles of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0043] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout and in which:

[0044] Figure 1 A flow chart showing the steps of the antenna relative phase center error calibration method according to one embodiment of the present application is shown. DETAILED DESCRIPTION

[0045] Preferred embodiments of the present application will be described in more detail below. Although the following describes preferred embodiments of the present application, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0046] To facilitate understanding of the scheme and effects of the embodiments of the present application, three specific application examples are given below. Those skilled in the art should understand that the examples are only for the convenience of understanding the present application, and any specific details thereof are not intended to limit the present application in any way. Example 1

[0047] Figure 1 A flow chart showing steps of an antenna relative phase center error calibration method according to an embodiment of the application.

[0048] As Figure 1 shown, the antenna relative phase center error calibration method comprises:

[0049] Step 101, collecting multiple sets of GNSS satellite observations through two antennas respectively;

[0050] Step 102, performing inter-epoch and inter-antenna difference on the GNSS satellite observations respectively, and constructing phase center error measurement values of double difference;

[0051] Step 103, establishing a fitting formula of the phase center error measurement values of double difference through 4th order polynomial expansion;

[0052] Step 104, solving the fitting coefficients simultaneously according to the multiple sets of GNSS satellite observations;

[0053] Step 105, substituting the fitting coefficients into the fitting formula to obtain a calibration result, which is a model of relative antenna phase center error.

[0054] In one example, the phase center error measurement values of double difference are:

[0055] ,

[0056] wherein, represents the phase center error measurement values of double difference, represents carrier phase observations, superscripts represent satellite numbers, subscripts 1 and 2 represent antenna numbers, and subscripts t1 and t2 represent observed epochs, and p represents geometric distances between satellites and antenna installation points.

[0057] In one example, the fitting formula is:

[0058] ,

[0059] wherein, represents the phase center error measurement values of double difference, and a1, a2, a3 and a4 represent fitting coefficients.

[0060] In one example, the model of relative antenna phase center error is:

[0061] ,

[0062] wherein, is the relative phase center error at an elevation angle of .

[0063] In one example, the method further comprises:

[0064] High-precision dual-antenna orientation according to the model of relative antenna phase center error.

[0065] In one example, the high-precision dual-antenna orientation according to the model of relative antenna phase center error comprises:

[0066] After collecting GNSS observations, the satellite elevation angle is calculated according to the satellite ephemeris;

[0067] The relative phase center error value is calculated and eliminated using the model of relative phase center error;

[0068] High-precision dual-antenna orientation using corrected carrier phase observations.

[0069] In one example, before collecting multiple sets of GNSS satellite observations, the method further comprises:

[0070] Arranging two antennas to be tested.

[0071] In one example, the method of arranging two antennas to be tested comprises:

[0072] Determining two test points on the calibration site, and calibrating the coordinates of the test points.

[0073] Arranging two antennas to be tested horizontally at the two test points, and the orientations of the two antennas are consistent.

[0074] Specifically, an open calibration site is selected, and in order to reduce the influence of satellite signal blocking by nearby objects and multipath error on the accuracy of carrier phase observations, objects and buildings that may block satellites around the site are avoided as much as possible; at the same time, gravel or choke coils can be laid under the antennas to reduce reflected signals from the ground.

[0075] Two test points are selected, which are several meters apart, and high-precision GNSS antennas and satellite navigation receivers are used to calibrate the accurate coordinates of the two points. Specifically, precise point positioning (PPP) or relative carrier phase positioning (RTK) can be used.

[0076] The two low-cost antennas to be calibrated are arranged horizontally at the two points, and the orientations of the two antennas are consistent. The orientation of the antenna can be defined as the direction of the North Reference Point (NRP). The NRP can be defined by the antenna manufacturer, or the direction of the cable connection port can be used as the NRP, or it can be defined by the user.

[0077] GNSS observations, including pseudorange and carrier phase observations, are collected using a dual-antenna receiver connected to two low-cost antennas or two co-timed receivers connected to two low-cost antennas respectively. Each antenna can observe and collect observations of every GNSS satellite in view at each time instance, so multiple sets of observations can be collected. The data collection lasts for at least one day.

[0078] The carrier phase observations of each satellite are used to perform inter-epoch and inter-antenna differencing respectively, and the twice-differenced phase center error measurements are constructed. The twice-differenced phase center error measurements can be represented as:

[0079]

[0080] wherein represents the carrier phase observations, the superscript represents the satellite number, the subscripts 1 and 2 represent the antenna numbers, and the subscripts t1 and t2 represent the epochs of the observations. p represents the geometric distance between the satellite and the antenna installation point, which can be calculated from the coordinates of the antenna installation point and the satellite. The satellite coordinates can be calculated according to the ephemeris broadcast by the GNSS satellite. represents the inter-antenna differencing, i.e., the difference between the carrier phase observations of the same satellite by the two antennas at the same time instance, which can be used to eliminate some common errors such as ionospheric errors and tropospheric errors; represents the inter-epoch differencing of the inter-antenna differencing measurements, which can be used to eliminate the ambiguity parameters in the carrier phase observations. Traditional antenna calibration methods usually use complex ambiguity resolution algorithms to resolve the values of the ambiguity parameters, but such algorithms usually require that the carrier phase observations do not contain too much bias, which is true for high-precision GNSS antennas. However, the carrier phase observations of low-cost antennas usually contain large phase center errors, up to several centimeters, so it is difficult to perform reliable integer ambiguity resolution. Therefore, the inter-epoch differencing is used to eliminate the ambiguity parameters by taking advantage of the fact that the ambiguity remains unchanged under the condition that the satellite is continuously locked by the receiver.

[0081] Using the observations of all visible GNSS satellites by the two antennas during the data collection period, a large number of twice-differenced phase center error measurements can be constructed. The distance between the two antennas is very small compared to the distance from the antennas to the satellites, so it can be considered that the incident directions of the same satellite to the two antennas are parallel, i.e., ; represents the elevation angle of satellite 1 with respect to antenna 1 at epoch t1. After the inter-antenna and inter-epoch twice-differencing operations, the twice-differenced phase center error measurements only contain the phase center errors at two different epochs and two antennas, which can be represented as:

[0082] ​ ,

[0083] where, is the twice-difference measurement, is the to-be-calibrated relative phase center error at the elevation angle is the relative phase center error, i.e. the difference of the phase center errors of the two antennas.

[0084] The phase center error is related to both the azimuth angle and the elevation angle, but in the relative in-situ calibration, the antenna to be measured is in a static state, and the observation of the visible satellite cannot cover the entire antenna hemisphere, so in the relative in-situ calibration, only the relationship between the phase center error and the elevation angle is calibrated. Since the phase center error usually changes less with the azimuth angle and changes more with the elevation angle, in actual GNSS applications, only the phase center error related to the elevation angle is used to correct most of the phase center error. In addition, t1 and t2 need to be separated by at least 1 hour to ensure that the satellite elevation angle changes significantly.

[0085] After obtaining a large number of twice-difference observations of the phase center error, the next step is to fit the phase center error model. A 4th order polynomial is used to expand the relative phase center error :

[0086] ,

[0087] where a1, a2, a3, a4 represent the to-be-solved fitting coefficients, and when the four coefficients are determined, a unique relative phase center error value can be determined through the elevation angle.

[0088] Bringing the fitting model into the calculation expression of the phase center error measurement and the relative phase center error, the relationship between the constructed twice-difference measurement and the to-be-solved coefficients can be obtained:

[0089] ,

[0090] Since a large number of measurements are constructed, a plurality of sets of difference measurement fitting formulas are obtained according to a plurality of sets of GNSS satellite observations, and then the fitting parameters are solved by the least square method to obtain the model of the relative antenna phase center error.

[0091] After calibrating the model of the relative phase center error, in actual two-antenna orientation applications, the orientation algorithm always uses the difference form of the GNSS observation. After the receiver collects the GNSS observation, the satellite elevation angle can be calculated according to the satellite ephemeris, then the value of the relative phase center error is estimated using the calibrated model of the relative phase center error, and the estimated value is used to eliminate the phase center error contained in the differential carrier phase observation between the antennas; then high-precision two-antenna orientation can be performed using the corrected carrier phase observation.

[0092] The method is suitable for low-cost antennas, has the characteristics of simple operation, and requires low equipment for antenna calibration. It does not need to build an anechoic chamber or customize a calibration robot. Since the antenna calibration is for dual-antenna directional applications, it also does not need a high-precision antenna with an accurately known phase center error as a reference antenna. In view of the difficulty in reliably solving the ambiguity caused by the centimeter-level deviation of the carrier phase observation of the low-cost antenna, the ambiguity is kept unchanged during the receiver continuously locking the satellite signal. The epoch difference is used to eliminate the ambiguity, and the difficulty in reliably solving the ambiguity of the low-cost antenna is avoided.

[0093] The method can calibrate the model of the relative phase center error of two antennas, so that the dual-antenna directional application is no longer limited to high-precision antennas with small phase center errors. Low-cost antennas with large phase center deviations can be selected, which helps the scale and industrialization of dual-antenna directional applications. Embodiment 2

[0094] The present disclosure provides an electronic device, comprising: a memory storing executable instructions; and a processor running the executable instructions in the memory to implement the above-mentioned antenna relative phase center error calibration method.

[0095] The electronic device according to the embodiments of the present disclosure comprises a memory and a processor.

[0096] The memory is configured to store non-transitory computer-readable instructions. Specifically, the memory can include one or more computer program products, which can include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may, for example, include random access memory (RAM), cache memory, and / or the like. The non-volatile memory may, for example, include read-only memory (ROM), hard disk, flash memory, and / or the like.

[0097] The processor can be a central processing unit (CPU) or other forms of processing units having data processing and / or instruction execution capabilities, and can control other components in the electronic device to perform desired functions. In an embodiment of the present disclosure, the processor is configured to run the computer-readable instructions stored in the memory.

[0098] Those skilled in the art should understand that, in order to solve the technical problem of how to obtain a good user experience effect, the present embodiment can also include well-known structures such as a communication bus, an interface, and the like, which should also be included in the protection scope of the present disclosure.

[0099] Detailed description of the present embodiment can refer to the corresponding description in the foregoing embodiments, which will not be repeated here. Embodiment 3

[0100] The computer readable storage medium of the present embodiment stores a computer program, and the computer program is executed by a processor to implement the antenna relative phase center error calibration method.

[0101] The computer readable storage medium of the present embodiment stores a computer program, and the computer program is executed by a processor to implement the antenna relative phase center error calibration method.

[0102] The computer readable storage medium includes, but is not limited to, optical storage media (for example, CD-ROM and DVD), magneto-optical storage media (for example, MO), magnetic storage media (for example, magnetic tape or mobile hard disk), media with built-in rewritable non-volatile memory (for example, memory card), and media with built-in ROM (for example, ROM cartridge).

[0103] Those skilled in the art should understand that the above description of the embodiments of the present application is only for the purpose of exemplarily illustrating the beneficial effects of the embodiments of the present application, and is not intended to limit the embodiments of the present application to any examples given.

[0104] The above has described the embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An antenna relative phase center error calibration method, characterized in that, The method comprises: collecting multiple sets of GNSS satellite observations through two antennas respectively; performing inter-epoch and inter-antenna difference on the GNSS satellite observations respectively to construct twice-differenced phase center error measurements; establishing a fitting formula of the twice-differenced phase center error measurements through 4th order polynomial expansion; simultaneously solving fitting coefficients according to the multiple sets of GNSS satellite observations; substituting the fitting coefficients into the fitting formula to obtain a calibration result, which is a model of relative antenna phase center error; wherein the twice-differenced phase center error measurements are: wherein denotes the twice-differenced phase center error measurement, denotes the carrier phase observations, the superscript denotes the satellite number, the subscripts 1, 2 denote the antenna number, the subscripts t1, t2 denote the epoch of the observation, and p denotes the geometric range from the satellite to the antenna installation point; wherein the fitting formula is: wherein denotes the twice-differenced phase center error measurement, and a1, a2, a3, a4 denote the fitting coefficients; wherein the model of relative antenna phase center error is: wherein is the relative phase center error at the elevation angle of 90°.

2. The antenna relative phase center error calibration method of claim 1, wherein, The method further comprises: performing high-precision dual-antenna orientation according to the model of relative antenna phase center error.

3. The antenna relative phase center error calibration method of claim 2, wherein, The high-precision dual-antenna orientation according to the model of relative antenna phase center error comprises: after collecting GNSS observations, calculating satellite elevation angles according to satellite ephemeris; calculating relative phase center error values using the model of relative phase center error and eliminating them; performing high-precision dual-antenna orientation using corrected carrier phase observations.

4. The antenna relative phase center error calibration method of claim 3, wherein, Before collecting multiple sets of GNSS satellite observations, the method further comprises: arranging two antennas to be tested.

5. The antenna relative phase center error calibration method of claim 4, wherein, Arranging two antennas to be tested comprises: determining two test points on the calibration site and calibrating coordinates of the test points; arranging two antennas to be tested horizontally on the two test points, and the orientations of the two antennas are consistent.

6. An electronic device, comprising: The electronic device comprises: a memory storing executable instructions; a processor running the executable instructions in the memory to implement the antenna relative phase center error calibration method in any one of claims 1-5.

7. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program which, when executed by a processor, implements the antenna relative phase center error calibration method in any one of claims 1-5.

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