Method for estimating the elevation angle of the incoming wave for ionospheric oblique sounding based on polarization response

Abstract

The application discloses a method for estimating the elevation angle of a slant ionospheric sounding incoming wave based on polarization response, which comprises the following steps: obtaining the polarization response information of the incoming wave through an orthogonal receiving antenna, so as to determine the limit polarization of the incoming wave signal from the ionosphere into free space, and determining the direction of the incoming wave through the relationship between the limit polarization and the elevation angle of the incoming wave and the geomagnetic field. The method for estimating the elevation angle of the slant ionospheric sounding incoming wave based on polarization response can be applied to the acquisition of the elevation angle information of the incoming wave through the processing and estimation of the polarization information of the electromagnetic wave, and can also be used as an auxiliary means of the traditional short-wave direction finding method.

Description

Technical Field

[0001] This invention relates to the field of ionospheric research and application technology, and in particular to a method for estimating the elevation angle of incoming waves from oblique ionospheric detection based on polarization response. Background Technology

[0002] Ionospheric sounding is a crucial means of acquiring ionospheric information, providing vital ionospheric environmental information support for ionospheric research, communication, navigation, and direction finding. Traditional ground-based ionospheric sounding methods include vertical sounding, oblique sounding, and reflected backscattering sounding. These methods typically acquire information such as signal strength, propagation delay, Doppler shift, and Doppler broadening of the probed signal. Based on this information, the ionospheric electron density distribution and the distribution and motion of ionospheric inhomogeneities can be inverted. With the development of sounding technology, the amount of information that can be obtained has gradually increased, such as acquiring the azimuth information of the probed signal. Azimuth information is usually obtained through array antennas or networked sounding equipment. To date, no publicly available technology for acquiring the azimuth information of incoming waves using oblique sounding has been found. The method for estimating the elevation angle of incoming waves in oblique ionospheric sounding in this application utilizes the polarization information of the incoming wave received by an orthogonal cross-loop antenna to estimate the elevation angle of the oblique sounding wave.

[0003] Currently, polarization information processing has received widespread attention in the fields of optical, radar, and satellite communications, particularly in radar target detection, enhancement, filtering, and identification, demonstrating its enormous application potential. However, the depth and breadth of research on polarization information processing in wireless communications are far from commensurate with its importance. In the shortwave application field, due to the complexity of ionospheric wave propagation, research on the application of polarization information is relatively limited. In the shortwave band, the main application of polarization is currently polarization diversity technology, while practical polarization information processing is mainly applied to ionospheric detection. In ionospheric detection, the earliest method utilizing polarization information was vertical detection, typically employing orthogonal antenna pairs to receive the detection echo signal reflected from the ionosphere above the detection station, measuring information such as the polarization of the transmitted signal, and using the polarization information of electromagnetic waves to achieve the separation of O-waves and X-waves. Subsequently, research was conducted on ox-wave separation technology based on polarization information for oblique detection, as well as research on polarization response prediction methods for oblique detection in different transceiver links. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for estimating the elevation angle of incoming waves in ionospheric oblique detection based on polarization response. This method can be applied to ionospheric oblique detection to obtain the elevation angle information of incoming waves, and can also serve as an auxiliary means for traditional shortwave direction finding methods.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for estimating the elevation angle of incoming waves from oblique ionospheric detection based on polarization response includes the following steps:

[0008] Step 1: Construct a pair of orthogonal receiving antennas. The receiving antennas sense the incoming wave signal from the ionosphere, and their elevation angle is [value missing]. This allows us to obtain the amplitude ratio and phase difference between the two antenna arms.

[0009] Step 2: Calculate the latitude and longitude of the incoming wave's location outside the ionosphere, and calculate the geomagnetic field vector from the ionosphere to the location in free space. and will Vector projection onto the antenna coordinate system;

[0010] Step 3: Based on the projection relationship between coordinate systems, the coordinates determined by the wave propagation direction and the geomagnetic field direction are... The unit vectors of the axes are projected onto the coordinate system where the receiving antenna is located;

[0011] Step 4: Calculate the polarization ratio at the ionosphere exit position based on the definition of polarization ratio and the amplitude ratio and phase difference between the two antenna arms. The angle between the wave propagation direction vector and the geomagnetic field vector can be solved based on the vector relationship between them. The limiting polarization of an incoming wave as it enters free space from the ionosphere can be obtained using the limiting polarization formula. ;

[0012] Step 5, within the effective range of the incoming wave elevation angle, increment by step size. Conduct a search to find and The minimum elevation angle is used to estimate the elevation angle of the incoming wave from the oblique probe of the ionosphere.

[0013] A further improvement to the above technical solution is as follows:

[0014] In the above technical solution, preferably, in step 1, each antenna arm of the receiving antenna is connected to a receiving channel, and each receiving channel outputs two signals, I and Q, to obtain the amplitude and phase information of each antenna arm and obtain the amplitude ratio between two orthogonal antenna arms. and phase difference ,in and These represent the amplitudes of the two orthogonal antenna arms, respectively.

[0015] In the above technical solution, preferably, in step 2, the coordinates of the geomagnetic field vector at the location where the radio wave exits the ionosphere in the geocentric coordinate system are solved according to the IGRF model. In this system, the origin of the geocentric coordinate system coincides with the center of the Earth. The line of intersection between the axis and the prime meridian plane and the equatorial plane is positive when it points outwards. The axis coincides with the Earth's axis of rotation, with north being positive. shaft and A right-handed system formed by perpendicular planes.

[0016] In the above technical solution, preferably, in step 2, the following steps are performed: The vector projection onto the coordinate system where the receiving antenna is located is:

[0017]

[0018] The geographic coordinates of the receiving end are: The distance between the receiving antenna and the transmitting antenna is D km.

[0019] In the above technical solution, preferably, in step 3, the coordinate system determined by the direction of radio wave propagation and the direction of the geomagnetic field is... Projected onto the Cartesian coordinate system where the receiving antenna is located In the middle, for , And normalize the projection , .

[0020] In the above technical solution, preferably, in step 4, according to the definition of polarization ratio, the relationship between the receiving antenna response and the polarization ratio is as follows: The calculated polarization ratio of the incoming wave is .

[0021] In the above technical solution, preferably, in step 4, the solution is obtained based on the vector relationship between the wave propagation direction vector and the geomagnetic field vector. Vectors and Angle between vectors According to the limiting polarization formula

[0022]

[0023] Calculate the limiting polarization at the ionosphere exit point of radio waves In the formula , The amount of electron charge. For electronic quality.

[0024] The method for estimating the elevation angle of incoming waves from the ionosphere based on polarization response provided by this invention has the following advantages compared with the prior art:

[0025] This invention discloses a method for estimating the elevation angle of incoming waves in oblique ionospheric detection based on polarization response. By acquiring polarization response information of the incoming wave using an orthogonal receiving antenna, the limiting polarization of the incoming wave signal as it enters free space from the ionosphere is determined. The direction of arrival is then determined by the relationship between the limiting polarization and the elevation angle of the incoming wave, the geomagnetic field, etc. This invention estimates the elevation angle of oblique detection by processing electromagnetic wave polarization information. It can be applied to oblique ionospheric detection to obtain the elevation angle of incoming waves and can also serve as an auxiliary means for traditional shortwave direction finding methods. Attached Figure Description

[0026] Figure 1 This is the receiving antenna response diagram in Embodiment 1 of the present invention.

[0027] Figure 2 It is the coordinate system determined by the wave propagation direction and the geomagnetic field direction in Embodiment 1 of the present invention.

[0028] Figure 3 This is a geometric diagram of the calculated position of the incoming wave from the ionosphere to free space in Embodiment 1 of the present invention.

[0029] Figure 4 This is a diagram showing the relationship between the coordinate system of the ionospheric position determined by the wave propagation direction and the geomagnetic field and the coordinate system of the receiving antenna in Embodiment 1 of the present invention.

[0030] Figure 5 This is a schematic diagram of the process for detecting the elevation angle of incoming waves according to the present invention. Detailed Implementation

[0031] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0032] Example 1

[0033] Figures 1 to 5 This invention illustrates one embodiment of the method for estimating the elevation angle of an incoming wave from an ionospheric oblique detection system based on polarization response. In the ionospheric oblique detection system, the receiving antenna senses the incoming wave signal from the ionosphere, whose elevation angle is... Each antenna arm of the receiving antenna is connected to a receiving channel. Each receiving channel outputs two signals, I and Q, to obtain their amplitude and phase information. This allows us to obtain the amplitude ratio and phase difference between the two antenna arms. The latitude and longitude of the ionospheric location are calculated through geometric structure calculations. Based on the IGRF model, the geomagnetic field vector from the ionosphere to the free space location is calculated. and will The vector is projected onto the antenna coordinate system. Based on the projection relationship between coordinate systems, the coordinate system determined by the wave propagation direction and the geomagnetic field direction is then projected onto the antenna coordinate system. If the unit vectors of the two antenna arms are projected onto the coordinate system of the antenna, the polarization ratio at the ionosphere exit position can be obtained according to the definition of polarization ratio and the amplitude ratio and phase difference between the two antenna arms. The angle between the wave propagation direction vector and the geomagnetic field vector is calculated based on the vector relationship between them. Then, according to the limiting polarization formula, the limiting polarization of the incoming wave when it enters free space from the ionosphere can be obtained. Within the effective range of the incoming wave elevation angle, the step size is... Conduct a search to find and The desired elevation angle is the one that minimizes the distance, thus achieving the purpose of estimating the elevation angle of incoming waves detected obliquely to the ionosphere.

[0034] The method for detecting the elevation angle of an incoming wave according to the present invention includes the following steps:

[0035] Step S1, the geographical coordinates of the receiving end are known to be... The distance between the receiving antenna and the transmitting antenna D, and the azimuth angle of the receiving end relative to the transmitting end. The receiving end uses an orthogonal magnetic loop antenna to receive the incoming wave, such as Figure 1 As shown, there is a center frequency plane waves at an angle Incident at the receiving end;

[0036] The receiving antenna senses incoming wave signals from the ionosphere at an elevation angle of . Each antenna arm of the receiving antenna is connected to a receiving channel. Each receiving channel outputs two signals, I and Q, to acquire the amplitude and phase information of each antenna arm, thereby obtaining the amplitude ratio between two orthogonal antenna arms. and phase difference .

[0037] Step S2: Establish a rectangular coordinate system along the east-north-up direction at the location of the receiving antenna. The center of the receiving antenna coincides with the origin of the coordinate system, and the two orthogonal antenna arms are positioned along the east-north direction, respectively. For example... Figure 2 As shown, a rectangular coordinate system is established at the location where the incoming wave enters free space from the ionosphere. The direction of electromagnetic wave propagation is along The axis, the geomagnetic field vector is located at The plane is at an angle to the direction of propagation. ;

[0038] Step S3, as follows Figure 3 As shown, starting from the receiving end, the angle is... Draw a ray in the opposite direction and intersect it at the bottom of the ionosphere. This point is where the radio wave enters free space from the ionosphere. The latitude and longitude of the ionosphere can be obtained through geometric relationships and geodetic calculations.

[0039] Step S4: Solve the coordinates of the geomagnetic field vector at the location where the radio wave exits the ionosphere in the geocentric coordinate system based on the IGRF model. In this system, the origin of the geocentric coordinate system coincides with the center of the Earth. The line of intersection between the axis and the prime meridian plane and the equatorial plane is positive when it points outwards. The axis coincides with the Earth's axis of rotation, with north being positive. shaft and A right-handed system formed by perpendicular planes.

[0040] Step S5, based on the projection relationship between the geocentric coordinate system and the coordinate system where the receiving antenna is located, such as... Figure 4 As shown, in step S4 The vector projection onto the coordinate system where the antenna is located is:

[0041] .

[0042] Step S6: Based on the projection relationship between the coordinate systems established in Step S5, the coordinates determined by the direction of radio wave propagation and the direction of the geomagnetic field are... Projected onto the Cartesian coordinate system where the receiving antenna is located In the middle, for , And normalize the projection , .

[0043] Step S7, according to the definition of polarization ratio, the relationship between the receiving antenna response and the polarization ratio is as follows: The calculated polarization ratio of the incoming wave is .

[0044] Step S8, derived from steps S5 and S6, solves for the result based on the vector relationship between the wave propagation direction vector and the geomagnetic field vector. Vectors and Angle between vectors According to the limiting polarization formula

[0045]

[0046] Calculate the limiting polarization at the ionosphere exit point of radio waves In the formula , The amount of electron charge. For electronic quality.

[0047] Step S9, in Within the interval, by step size Repeat steps S1 to S8, and calculate the corresponding step size. and Distance between , find Minimum incoming wave elevation angle That's what we're looking for; the search is now complete.

[0048] This invention presents a method for estimating the elevation angle of incoming waves from ionospheric oblique detection based on polarization response. It utilizes a pair of orthogonal antennas to acquire the amplitude and phase of the antennas, thereby obtaining the limiting polarization information of the incoming wave. The elevation angle of the incoming wave is then estimated using this limiting polarization information. Compared to existing methods for acquiring the azimuth information of incoming waves, this method only requires a pair of orthogonal antennas to estimate the elevation angle, which is of practical value for the development of ionospheric oblique detection technology.

[0049] Example 2

[0050] In this embodiment, the method for detecting the elevation angle of incoming waves according to the present invention is applied to shortwave direction finding and positioning. Simulation is performed on a specific shortwave oblique detection link:

[0051] Assuming the receiver's geographical location is (33°, 109°), the center frequency of the radio wave is 10MHz, the azimuth angle is 110°, and the distances between the receiver and transmitter are set to 500km, 600km, 700km, 800km, 900km, 1000km, and 1500km respectively; and assuming the ionosphere is a homogeneous, collision-free cold plasma. Table 1 shows the simulation results of the estimated ionospheric oblique detection wave elevation angle provided by this invention.

[0052] Table 1

[0053]

[0054] As can be seen from Table 1, without considering measurement errors, the estimation error of the incoming wave elevation angle tends to 0, proving that the method of detecting the incoming wave elevation angle of the present invention can be applied to shortwave direction finding and positioning.

[0055] The above embodiments are merely preferred examples of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for estimating the elevation angle of incoming waves from an obliquely detected ionosphere based on polarization response, characterized in that, Includes the following steps: Step 1: Construct a pair of orthogonal receiving antennas. The receiving antennas sense the incoming wave signal from the ionosphere, and their elevation angle is [value missing]. This allows us to obtain the amplitude ratio and phase difference between the two antenna arms. Step 2: Calculate the latitude and longitude of the incoming wave's location outside the ionosphere, and calculate the geomagnetic field vector from the ionosphere to the location in free space. and will Vector projection onto the antenna coordinate system; Step 3: Based on the projection relationship between coordinate systems, the coordinates determined by the wave propagation direction and the geomagnetic field direction are... The unit vectors of the axes are projected onto the coordinate system where the receiving antenna is located; Step 4: Calculate the polarization ratio at the ionosphere exit position based on the definition of polarization ratio and the amplitude ratio and phase difference between the two antenna arms. The angle between the wave propagation direction vector and the geomagnetic field vector can be solved based on the vector relationship between them. The limiting polarization of an incoming wave as it enters free space from the ionosphere can be obtained using the limiting polarization formula. ; In step 4, according to the definition of polarization ratio, the relationship between the receiving antenna response and the polarization ratio is as follows: The calculated polarization ratio of the incoming wave is In the formula The amplitude ratio between the two orthogonal antenna arms. Phase difference; Step 5, within the effective range of the incoming wave elevation angle, increment by step size. Conduct a search to find and The minimum elevation angle is used to estimate the elevation angle of the incoming wave from the oblique probe of the ionosphere.

2. The method for estimating the elevation angle of an ionospheric oblique detection wave based on polarization response according to claim 1, characterized in that, In step 1, each antenna arm of the receiving antenna is connected to a receiving channel, and each receiving channel outputs two signals, I and Q, to obtain the amplitude and phase information of each antenna arm and to obtain the amplitude ratio between two orthogonal antenna arms. and phase difference ,in These represent the amplitudes of the two orthogonal antenna arms, respectively.

3. The method for estimating the elevation angle of an ionospheric oblique detection wave based on polarization response according to claim 1, characterized in that, In step 2, the coordinates of the geomagnetic field vector at the location of the radio wave exiting the ionosphere in the geocentric coordinate system are solved according to the IGRF model. In this system, the origin of the geocentric coordinate system coincides with the center of the Earth. The line of intersection between the axis and the prime meridian plane and the equatorial plane is positive when it points outwards. The axis coincides with the Earth's axis of rotation, with north being positive. shaft and A right-handed system formed by perpendicular planes.

4. The method for estimating the elevation angle of an ionospheric oblique detection wave based on polarization response according to claim 3, characterized in that, In step 2, The vector projection onto the coordinate system where the receiving antenna is located is: ； The geographic coordinates of the receiving end are: The distance between the receiving antenna and the transmitting antenna is D.

5. The method for estimating the elevation angle of an ionospheric oblique detection wave based on polarization response according to claim 4, characterized in that, In step 3, the coordinate system determined by the direction of radio wave propagation and the direction of the geomagnetic field will be... Projected onto the Cartesian coordinate system where the receiving antenna is located In the middle, for , And normalize the projection , .

6. The method for estimating the elevation angle of an ionospheric oblique detection wave based on polarization response according to claim 5, characterized in that, In step 4, the solution is obtained based on the vector relationship between the wave propagation direction vector and the geomagnetic field vector. Vectors and Angle between vectors According to the limiting polarization formula: ； Calculate the limiting polarization at the ionosphere exit point of radio waves In the formula , The amount of electron charge. For electronic quality.

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