Troposphere minimum scattering angle calculation method based on geoid

Abstract

The invention provides a troposphere minimum scattering angle calculation method based on a geoid, and the method comprises the steps: constructing a troposphere scattering path geometrical relationship through a transmitting antenna, a receiving antenna, a receiving radio wave ray and a geodetic coordinate of the transmitting radio wave ray encountering a highest obstacle, and proposing a mathematical model of the troposphere minimum scattering angle. Compared with a calculation method given by an ITU-R.P.617 proposal and certain academic papers, the troposphere scattering system signal transmission loss prediction method better meets the troposphere scattering system signal transmission loss prediction requirement, and the troposphere scattering transmission annual average loss median, the antenna deviation loss and the antenna low-rack loss calculation accuracy can be improved. The geoid is adopted to well reflect the shape of the earth, and the distance between the earth surfaces can be accurately measured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of data transmission, and also relates to a method for calculating a scattering angle. BACKGROUND

[0002] Compared with the calculation method of the minimum scattering angle of the troposphere given in the International Telecommunication Union (ITU) ITU-R.P.617 recommendation and some academic papers, the present application has high calculation accuracy, and can accurately calculate the median value of the annual average loss of tropospheric scattering transmission, the antenna deviation loss and the antenna low-elevation loss, and realize the prediction of the signal transmission loss of the tropospheric scattering system.

[0003] The minimum scattering angle is the angle between the two visual horizons of the transmitting and receiving ends in the plane of the earth's great circle, i.e. the minimum scattering angle under the condition that the antenna beam is not tilted, and is an important parameter for predicting the tropospheric scattering loss.

[0004] Based on the tropospheric scattering transmission loss prediction method proposed by Academician Zhang Minggao, the International Telecommunication Union published ITU-R.P.617-1 "Propagation Prediction Techniques and Data Required for the Design of Trans-Horizon Radio-Relay Systems" in 1992; after several revisions, it was upgraded to ITU-R.P.617-2, ITU-R.P.617-3, ITU-R.P.617-4 and ITU-R.P.617-5 versions in 2012, 2013, 2017 and 2019 respectively.

[0005] The minimum scattering angle of the troposphere is an important parameter for calculating the median value of the annual average loss of tropospheric scattering transmission, the antenna deviation loss and the antenna low-elevation loss. Currently, there are two calculation methods: one is the method of ITU-R.P.617-1, ITU-R.P.617-2, ITU-R.P.617-3, ITU-R.P.617-4 and ITU-R.P.617-5 recommendations, and the calculation formula is as follows:

[0006] (mrad)

[0007] Wherein: is the path length of the receiving and transmitting antennas (km);

[0008] is the radius of the earth;

[0009] is the equivalent earth radius factor.

[0010] Some academic papers also proposed the calculation method of the tropospheric minimum scattering angle, the formula is as follows:

[0011]

[0012] Wherein: is the path length of the transmitting and receiving antennas (km);

[0013] is the highest obstacle height encountered by the transmitting radio wave ray;

[0014] is the highest obstacle height encountered by the receiving radio wave ray;

[0015] is the transmitting antenna altitude;

[0016] is the receiving antenna altitude;

[0017] is the distance from the foot of the highest obstacle encountered by the transmitting antenna to the station;

[0018] is the distance from the foot of the highest obstacle encountered by the receiving antenna to the station;

[0019] is the equivalent earth radius.

[0020] The existing two calculation methods of the tropospheric minimum scattering angle are approximate calculation methods based on multiple assumptions.

[0021] (1) The method of ITU-R.P.617 Recommendation

[0022] Assume that the transmitting antenna altitude , the receiving antenna altitude ;

[0023] Assume that the transmitting radio wave ray encounters the highest obstacle altitude , the receiving radio wave ray encounters the highest obstacle altitude ;

[0024] The earth is equivalent to a standard sphere by the equivalent earth radius;

[0025] Assume that the lowest scattering point is located at the intersection of the transmitting and receiving antennas and the earth tangent.

[0026] This simplifies the calculation, such as Figure 1 , the tropospheric minimum scattering angle is equal to the great circle arc distance of the transmitting antenna and the receiving antenna That is, the angle between the transmitting antenna, the receiving antenna, and the center of the sphere.

[0027] The method described in ITU-RP617 recommendation, which does not take into account the altitude of the transmitting antenna, receiving antenna, and obstacles, and uses an equivalent approximation of the Earth, will inevitably introduce deviations in the calculation of the minimum scattering angle.

[0028] (2) Methods in some academic papers

[0029] In the derivation of the minimum scattering angle formula in some academic papers, the Earth is first equated to a standard sphere using an equivalent Earth radius, while assuming the altitude of the transmitting antenna is [not specified]. Altitude of receiving antenna This will also affect the accuracy of the minimum scattering angle calculation.

[0030] To accurately predict tropospheric loss, this invention proposes a method for calculating the minimum tropospheric scattering angle based on the geoid. Summary of the Invention

[0031] To overcome the shortcomings of existing technologies, this invention provides a method for calculating the minimum tropospheric scattering angle based on the geoid.

[0032] The technical solution adopted by this invention to solve its technical problem is:

[0033] The present invention uses the following methods and steps to calculate the minimum tropospheric scattering angle.

[0034] Step 1: Construct the geometric relationship of the tropospheric scattering path;

[0035] The geometric relationship of the tropospheric scattering path is as follows: Figure 1 As shown, where: The geodetic coordinates of the transmitting antenna; The geodetic coordinates of the receiving antenna; The coordinates of the highest obstacle encountered when the emitted radio wave rays are emitted; The coordinates of the highest obstacle encountered when receiving radio waves; This is the lowest scattering point; The angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight; The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight; The angle between the transmitting antenna, the receiving antenna, and the center of the sphere; The radius of the Earth;

[0036] Step 2: Calculate the transmitting antenna With receiving antenna straight-line distance between ;

[0037] Step 3: Calculate the distance between the transmitted radio wave ray and the highest obstacle encountered by the transmitting antenna. ;

[0038] Step 4: Calculate the angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight. ;

[0039] Step 5: Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna;

[0040] Step 6: Calculate the angle between the line connecting the transmitting and receiving antennas and the receiving horizon. ;

[0041] Step 7: Calculate the minimum scattering angle.

[0042] Step 2 calculates the transmitting antenna. With receiving antenna straight-line distance between The specific steps are as follows:

[0043] The positions of the transmitting and receiving antennas are converted to WGS-84 geocentric rectangular coordinates. The WGS-84 geocentric rectangular coordinates of the transmitting antenna are:

[0044] (1);

[0045] in Longitude of the transmitting antenna; The latitude of the transmitting antenna; The altitude of the transmitting antenna; For the first eccentricity, ; It is the semi-major axis of the Earth's ellipsoid;

[0046] (2);

[0047] The geocentric rectangular coordinates of the receiving antenna WGS-84 are:

[0048] (3);

[0049] in: Longitude of the receiving antenna; Latitude of the receiving antenna; Altitude of the receiving antenna; For the first eccentricity, ; The major radius of the Earth's reference ellipsoid;

[0050] (4);

[0051] The straight-line distance AC between the transmitting antenna and the receiving antenna is calculated as follows:

[0052] (5);

[0053] Step 3 calculates the distance between the transmitted radio wave ray encountering the highest obstacle and the transmitting antenna. The specific steps are as follows:

[0054] The location of the emitted radio wave ray encountering the highest obstacle, converted to WGS-84 geocentric rectangular coordinates, is:

[0055] (6);

[0056] in: The longitude of the highest obstacle encountered when emitting radio waves; The latitude at which the emitted radio waves encounter the highest obstacle. The altitude of the highest obstacle encountered when emitting radio waves;

[0057] The distance AD ​​between the transmitted radio wave ray encountering the highest obstacle and the transmitting antenna is calculated as follows:

[0058] (7).

[0059] Step 4 involves calculating the angle between the line connecting the transmitting and receiving antennas and the line of sight for transmission. The calculation formula is:

[0060] (8);

[0061] in: The radius of the Earth; The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna.

[0062] The specific steps for calculating the distance between the highest obstacle encountered by the received radio wave ray and the receiving antenna in step 5 are as follows:

[0063] The received radio wave rays, when encountering the highest obstacle, are converted to WGS-84 Earth-centered, Earth-fixed rectangular coordinates as follows:

[0064] (9);

[0065] in: The longitude of the highest obstacle encountered when receiving radio waves; The latitude at which the highest obstacle is encountered in order to receive radio waves; The altitude of the highest obstacle encountered in order to receive radio waves;

[0066] Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna. for:

[0067] (10).

[0068] Step 6 calculates the angle between the line connecting the transmitting antenna and the receiving antenna and the receiving line of sight. The calculation formula is:

[0069] (11);

[0070] in: The radius of the Earth; The distance between the highest obstacle encountered and the receiving antenna when receiving radio waves.

[0071] The specific steps for calculating the minimum scattering angle in step 7 are as follows:

[0072] Depend on Figure 1 It can be seen that the minimum scattering angle is the angle between the line connecting the transmitting and receiving antennas and the transmitting horizon. The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight. The sum is:

[0073] (12);

[0074] This yields the minimum scattering angle. .

[0075] An electronic device includes: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs are configured to perform the methods described above.

[0076] A computer-readable storage medium storing program code that can be invoked by a processor to perform the method described above.

[0077] The beneficial effects of this invention are that, by using the geoid, the shape of the Earth is well reflected, and the distances between Earth's surfaces can be accurately measured. This invention constructs the geometric relationship of the tropospheric scattering path by using the geodetic coordinates of the transmitting antenna, the receiving antenna, the received radio waves, and the highest obstacle encountered by the transmitted radio waves. It proposes a mathematical model for the minimum tropospheric scattering angle. Compared with the calculation methods given in ITU-RP617 Recommendation and some academic papers, this method is more in line with the requirements for predicting signal transmission loss in tropospheric scattering systems, and can improve the accuracy of calculating the median annual average loss of tropospheric scattering transmission, antenna deflection loss, and antenna undermount loss. Attached Figure Description

[0078] Figure 1This is a schematic diagram of the geometric relationship of the tropospheric scattering path in this invention.

[0079] Figure 2 is a simulation analysis diagram of the difference between the minimum tropospheric scattering angle results of the present invention and ITU-RP617. Figure 2(a) is the simulation analysis diagram with a transmitting antenna height of 10km, Figure 2(b) is the simulation analysis diagram with a transmitting antenna height of 5km, and Figure 2(c) is the simulation analysis diagram with a transmitting antenna height of 1km.

[0080] Figure 3 shows the simulation analysis diagram of the difference between the minimum tropospheric scattering angle results of the present invention and the prior art. Figure 3(a) is the simulation analysis diagram with a transmitting antenna height of 10km, Figure 3(b) is the simulation analysis diagram with a transmitting antenna height of 5km, and Figure 3(c) is the simulation analysis diagram with a transmitting antenna height of 1km. Detailed Implementation

[0081] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0082] The present invention uses the following methods and steps to calculate the minimum tropospheric scattering angle.

[0083] Step 1: Construct the geometric relationship of the tropospheric scattering path;

[0084] The geometric relationship of the tropospheric scattering path is as follows: Figure 1 As shown, where: The geodetic coordinates of the transmitting antenna; The geodetic coordinates of the receiving antenna; The coordinates of the highest obstacle encountered when the emitted radio wave rays are emitted; The coordinates of the highest obstacle encountered when receiving radio waves; This is the lowest scattering point; The angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight; The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight; The angle between the transmitting antenna, the receiving antenna, and the center of the sphere; The radius of the Earth;

[0085] Step 2: Calculate the transmitting antenna With receiving antenna straight-line distance between ;

[0086] Convert the positions of the transmitting and receiving antennas to WGS-84 geocentric rectangular coordinates

[0087] The ground-based rectangular coordinates of the transmitting antenna WGS-84 are:

[0088] (1);

[0089] in Longitude of the transmitting antenna; The latitude of the transmitting antenna; The altitude of the transmitting antenna; For the first eccentricity, ; It is the semi-major axis of the Earth's ellipsoid;

[0090] (2);

[0091] The geocentric rectangular coordinates of the receiving antenna WGS-84 are:

[0092] (3);

[0093] in: Longitude of the receiving antenna; Latitude of the receiving antenna; Altitude of the receiving antenna; For the first eccentricity, ; The major radius of the Earth's reference ellipsoid;

[0094] (4);

[0095] The straight-line distance AC between the transmitting antenna and the receiving antenna is calculated as follows:

[0096] (5);

[0097] Step 3: Calculate the distance between the transmitted radio wave ray and the highest obstacle encountered by the transmitting antenna. ;

[0098] The location of the emitted radio wave ray encountering the highest obstacle, converted to WGS-84 geocentric rectangular coordinates, is:

[0099] (6);

[0100] in: The longitude of the highest obstacle encountered when emitting radio waves; The latitude at which the emitted radio waves encounter the highest obstacle. The altitude of the highest obstacle encountered when emitting radio waves;

[0101] The distance AD ​​between the transmitted radio wave ray encountering the highest obstacle and the transmitting antenna is calculated as follows:

[0102] (7);

[0103] Step 4: Calculate the angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight. ;

[0104] (8);

[0105] in: The radius of the Earth; The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna.

[0106] Step 5: Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna;

[0107] The received radio wave rays, when encountering the highest obstacle, are converted to WGS-84 Earth-centered, Earth-fixed rectangular coordinates as follows:

[0108] (9);

[0109] in: The longitude of the highest obstacle encountered when receiving radio waves; The latitude at which the highest obstacle is encountered in order to receive radio waves; The altitude of the highest obstacle encountered in order to receive radio waves;

[0110] Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna. for:

[0111] (10);

[0112] Step 6: Calculate the angle between the line connecting the transmitting and receiving antennas and the receiving horizon. ;

[0113] (11);

[0114] in: The radius of the Earth; The distance between the highest obstacle encountered when receiving radio waves and the receiving antenna;

[0115] Step 7: Calculate the minimum scattering angle.

[0116] Depend on Figure 1 It can be seen that the minimum scattering angle is the angle between the line connecting the transmitting and receiving antennas and the transmitting horizon. The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight. The sum is:

[0117] (12);

[0118] This yields the minimum scattering angle. .

[0119] The following is an example:

[0120] (1) Antenna position

[0121] Transmitting antenna: Longitude ;latitude The altitudes are respectively , , .

[0122] Receiving antenna: Altitude .

[0123] (2) Location of obstacles

[0124] When the emitted radio wave encounters the highest obstacle, the distance between the emitted antenna and the highest obstacle... altitude ;

[0125] When the received radio wave encounters the highest obstacle, the distance between the receiving antenna and the highest obstacle... altitude ;

[0126] (3) Scope of analysis

[0127] Assuming the Earth is a standard reference ellipsoid, the distance beyond line of sight can be calculated by using formula (13) based on the altitude of the transmitting and receiving antennas.

[0128] (13)

[0129] Table 1. Beyond-line-of-sight distances at different antenna altitudes

[0130]

[0131] (4) Analysis results

[0132] When the distance between the receiving antenna and the transmitting antenna is greater than the beyond-line-of-sight distance As shown in Table 1, in the region of 28°–40° North latitude and 100°–118° East longitude, the minimum tropospheric scattering angle was calculated by applying the methods of this invention, ITU-RP617 Recommendation, and related academic papers.

[0133] Figures 2(a), 2(b), and 2(c) show the simulation analysis of the difference between the results of calculating the minimum tropospheric scattering angle using the two mathematical models of this invention and ITU-RP 617 Recommendation. It can be seen that the antenna altitude has a significant impact on the calculation results; the higher the transmitting antenna, the greater the difference in the calculated results. The main reason for this difference is that the mathematical model in ITU-RP 617 Recommendation is based on various assumptions, particularly the lack of information on the altitude of the antenna and obstacles, as well as the distance between the obstacles and the antenna, in the calculation.

[0134] Figures 3(a), 3(b), and 3(c) show the simulation analysis of the difference between the results of calculating the minimum tropospheric scattering angle using the two methods of this invention and existing technical papers.

[0135] Table 2. Differences in the calculation results of the minimum tropospheric scattering angle of the present invention, ITU-RP617, and academic papers.

[0136]

[0137] In Table 2, the unit is mrad (milliradians).

[0138] It can be seen that when the altitude of the receiving antenna remains constant, but the altitude of the transmitting antenna is different, the calculation results of the two methods will also have some differences. This is mainly because some academic papers derive the minimum tropospheric scattering angle by treating the Earth as a standard sphere with an equivalent Earth radius, and simply equate the distance from the Earth's center to the transmitting and receiving antennas to the Earth's radius, ignoring the antenna altitude.

Claims

1. A method for calculating the minimum tropospheric scattering angle based on the geoid, characterized in that... Includes the following steps: Step 1: Construct the geometric relationship of the tropospheric scattering path; In the geometry of tropospheric scattering paths: The geodetic coordinates of the transmitting antenna; The geodetic coordinates of the receiving antenna; The coordinates of the highest obstacle encountered when the emitted radio wave rays are emitted; The coordinates of the highest obstacle encountered when receiving radio waves; The lowest scattering point; The angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight; The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight; The angle between the transmitting antenna, the receiving antenna, and the center of the sphere; The radius of the Earth; Step 2: Calculate the transmitting antenna With receiving antenna straight-line distance between ; Step 3: Calculate the distance between the transmitted radio wave ray and the highest obstacle encountered by the transmitting antenna. ; Step 4: Calculate the angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight. ; Step 5: Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna; Step 6: Calculate the angle between the line connecting the transmitting and receiving antennas and the receiving horizon. ; Step 7: Calculate the minimum scattering angle.

2. The method for calculating the minimum tropospheric scattering angle based on the geoid according to claim 1, characterized in that: Step 2 calculates the transmitting antenna. With receiving antenna straight-line distance between The specific steps are as follows: The positions of the transmitting and receiving antennas are converted to WGS-84 geocentric rectangular coordinates. The WGS-84 geocentric rectangular coordinates of the transmitting antenna are: （1）； in Longitude of the transmitting antenna; The latitude of the transmitting antenna; The altitude of the transmitting antenna; For the first eccentricity, ; It is the semi-major axis of the Earth's ellipsoid; （2）； The geocentric rectangular coordinates of the receiving antenna WGS-84 are: （3）； in: Longitude of the receiving antenna; Latitude of the receiving antenna; Altitude of the receiving antenna; For the first eccentricity, ; The major radius of the Earth's reference ellipsoid; （4）； The straight-line distance AC between the transmitting antenna and the receiving antenna is calculated as follows: （5）。 3. The method for calculating the minimum tropospheric scattering angle based on the geoid according to claim 1, characterized in that: Step 3 calculates the distance between the transmitted radio wave ray encountering the highest obstacle and the transmitting antenna. The specific steps are as follows: The location of the emitted radio wave ray encountering the highest obstacle, converted to WGS-84 geocentric rectangular coordinates, is: （6）； in: The longitude of the highest obstacle encountered when emitting radio waves; The latitude at which the emitted radio waves encounter the highest obstacle. The altitude of the highest obstacle encountered when emitting radio waves; The distance AD ​​between the transmitted radio wave ray encountering the highest obstacle and the transmitting antenna is calculated as follows: （7）。 4. The method for calculating the minimum tropospheric scattering angle based on the geoid according to claim 1, characterized in that: Step 4 involves calculating the angle between the line connecting the transmitting and receiving antennas and the line of sight for transmission. The calculation formula is: （8）； in: The radius of the Earth; The distance between the highest obstacle encountered when transmitting radio waves and the transmitting antenna.

5. The method for calculating the minimum tropospheric scattering angle based on the geoid according to claim 1, characterized in that: The specific steps for calculating the distance between the highest obstacle encountered by the received radio wave ray and the receiving antenna in step 5 are as follows: The received radio wave rays, when encountering the highest obstacle, are converted to WGS-84 Earth-centered, Earth-fixed rectangular coordinates as follows: （9）； in: The longitude of the highest obstacle encountered when receiving radio waves; The latitude at which the highest obstacle is encountered in order to receive radio waves; The altitude of the highest obstacle encountered in order to receive radio waves; Calculate the distance between the highest obstacle encountered by the received radio wave and the receiving antenna. for: （10）。 6. The method for calculating the minimum tropospheric scattering angle based on the geoid according to claim 1, characterized in that: Step 6 calculates the angle between the line connecting the transmitting antenna and the receiving antenna and the receiving line of sight. The calculation formula is: （11）； in: The radius of the Earth; The distance between the highest obstacle encountered and the receiving antenna when receiving radio waves.

7. The method for calculating the minimum tropospheric scattering angle based on the geoid according to claim 1, characterized in that: The specific steps for calculating the minimum scattering angle in step 7 are as follows: The minimum scattering angle is the angle between the line connecting the transmitting and receiving antennas and the transmitting line of sight. The angle between the line connecting the transmitting and receiving antennas and the receiving line of sight. The sum is: （12）； This yields the minimum scattering angle. .

8. An electronic device, characterized in that, include: One or more processors; Memory; One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs being configured to perform the method as described in any one of claims 1-7.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores program code that can be invoked by a processor to execute the method as described in any one of claims 1-7.

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