A method and device for reducing radio frequency interference in a phased array radio telescope

Abstract

The application relates to the field of radio astronomy signal processing, and discloses a radio frequency interference reduction method and device for a phased array radio telescope, wherein the method comprises the following steps: acquiring relative position information of a plurality of navigation satellites, determining potential interference satellites from the plurality of navigation satellites according to the relative position information; acquiring a wideband signal collected by the phased array radio telescope, and determining a plurality of interfered subbands in the wideband signal; matching the interfered subbands with the potential interference satellites, and determining subband interference information of the interfered subbands according to a matching result; acquiring a signal subspace and an interference subspace of the interfered subbands, and then determining a skew projection matrix of the interfered subbands; and simultaneously performing interference reduction and digital beam forming on the interfered subbands according to the skew projection matrix and the signal subspace. The technical scheme provided by one or more embodiments of the application can realize continuous interference reduction of the phased array radio telescope on the in-orbit satellites.

Description

Technical Field

[0001] This application relates to the field of radio astronomy signal processing, and in particular to a method and apparatus for reducing radio frequency interference in a phased array radio telescope. Background Technology

[0002] As crucial instruments for studying the evolution of celestial bodies and phenomena, phased-array radio telescopes (PASTs) are highly sensitive to radio frequency interference due to their large field of view. In practical applications, when capturing radio signals from the sky, PASTs are easily affected by continuous interference from satellites operating in the same frequency band and sky region. Therefore, eliminating satellite interference is one of the key aspects of signal processing for PASTs. Summary of the Invention

[0003] This application provides a method and apparatus for reducing radio frequency interference of a phased array radio telescope, which can reduce the interference of the phased array radio telescope to on-orbit navigation satellites.

[0004] The first aspect of this application provides a method for reducing radio frequency interference (RFI) in a phased array radio telescope. The method includes: acquiring relative position information of multiple navigation satellites; identifying potential interfering satellites among the multiple navigation satellites based on the relative position information, wherein the relative position information includes at least azimuth and elevation angles; acquiring broadband signals collected by the phased array radio telescope and converting them into a sub-band signal set; identifying multiple interfering sub-bands in the sub-band signal set; matching the interfering sub-bands with the potential interfering satellites; determining the interference information of the interfering sub-bands based on the matching results; acquiring the signal subspace and interference subspace of the interfering sub-bands; determining the oblique projection matrix of the interfering sub-bands based on the signal subspace and interference subspace; and performing interference reduction and digital beamforming on the interfering sub-bands based on the oblique projection matrix and the signal subspace.

[0005] A second aspect of this application provides a radio frequency interference reduction device for a phased array radio telescope. The device includes: a parameter acquisition unit, configured to acquire relative position information of multiple navigation satellites, and determine potential interfering satellites among the multiple navigation satellites based on the relative position information, wherein the relative position information includes at least azimuth and elevation angles; an interference determination unit, configured to acquire broadband signals collected by the phased array radio telescope and convert them into a sub-band signal set, determine multiple interfering sub-bands in the sub-band signal set, match the interfering sub-bands with the potential interfering satellites, and determine sub-band interference information of the interfering sub-bands based on the matching results; and an interference reduction unit, configured to acquire the signal subspace and interference subspace of the interfering sub-bands, determine the oblique projection matrix of the interfering sub-bands based on the signal subspace and interference subspace, and perform interference reduction and digital beamforming on the interfering sub-bands based on the oblique projection matrix and the signal subspace.

[0006] The technical solution provided in one or more embodiments of this application firstly identifies potential interfering satellites that may cause interference based on the position information of multiple navigation satellites and the observation range of the phased array radio telescope. Then, it obtains multiple interfered sub-bands from the phased array radio telescope, performs frequency matching between the potential interfering satellites and the interfered sub-bands, and determines the corresponding sub-band interference information. Furthermore, it constructs an oblique projection matrix for interference reduction and uses this oblique projection matrix to process the sub-band signals of the phased array radio telescope to reduce interference to on-orbit navigation satellites. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0008] Figure 1 A schematic diagram illustrating the steps of a method for reducing radio frequency interference in a phased array radio telescope, provided as one embodiment of this application;

[0009] Figure 2 A schematic diagram illustrating the steps of vector information coordinate transformation provided in one embodiment of this application;

[0010] Figure 3 A schematic diagram illustrating the steps for determining sub-band interference information provided in one embodiment of this application;

[0011] Figure 4 A schematic diagram illustrating the composition of a phased array provided in one embodiment of this application;

[0012] Figure 5(a) shows the power spectrum of received data after conventional beamforming processing according to an embodiment of this application;

[0013] Figure 5(b) shows the power spectrum of received data after interference reduction and conventional beamforming processing according to an embodiment of this application;

[0014] Figure 6 This is a schematic diagram of the structure of a radio frequency interference reduction device for a phased array radio telescope provided in one embodiment of this application. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] Furthermore, the use of terms such as "first," "second," etc., in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of embodiments in this application, unless otherwise stated, "multiple" means two or more. Additionally, the use of "based on" or "according to" implies openness and inclusiveness, because processes, steps, calculations, or other actions "based on" or "according to" one or more of the stated conditions or values ​​may in practice be based on additional conditions or beyond the stated values.

[0017] Fast radio bursts (FRBs) are short, sudden radio pulses that appear in the dynamic universe. Detecting and locating FRBs allows us to correlate them with specific celestial objects or environments, which is of great significance for astronomical research. Phased array radio telescopes (PATs) have a large field of view and high sensitivity. Specifically, a phased array system can form multiple beams, and by adjusting the direction and number of beams, multiple sky regions can be monitored simultaneously. By monitoring the signals from multiple beams in real time, FRBs can be quickly captured, thus enabling large-field-of-view observation and multi-target monitoring of FRBs.

[0018] However, the large field of view of phased array radio telescopes makes them more susceptible to interference from multiple directions, especially radio frequency interference from satellites in orbit at the same frequency. For example, some continuously operating navigation satellite systems (such as BeiDou and GPS) cause continuous interference to L-band phased array radio telescopes, affecting the observation of astronomical signals. In related technologies, interference is usually digitally reduced by using a marked threshold method, but this method has limitations and requires a high strength of the interference signal, making it unsuitable for reducing navigation satellite interference. In view of this, this application provides one or more embodiments of a method and apparatus for reducing radio frequency interference of phased array radio telescopes, which can solve the above problems and reduce continuous interference from phased array radio telescopes to satellites in orbit, especially radio frequency interference from navigation satellites.

[0019] Please see Figure 1 One embodiment of this application provides a method for reducing radio frequency interference in a phased array radio telescope, which may include the following steps:

[0020] S1: Obtain the relative position information of multiple navigation satellites, and determine potential interfering satellites among the multiple navigation satellites based on the relative position information, wherein the relative position information includes at least azimuth and elevation angles.

[0021] The aforementioned relative position information refers to the navigation satellite's position relative to the ground station, such as azimuth, elevation, radial velocity, and Doppler frequency, used to determine the navigation satellite's orientation in space. The aforementioned potential interfering satellites can be understood as navigation satellites that may cause radio frequency interference to the phased array radio telescope. The aforementioned relative position information includes at least azimuth and elevation angles. The azimuth angle can be understood as the angle between the navigation satellite's projected position and its line of sight on the horizontal plane where the telescope is located, rotated clockwise from true north. The elevation angle can be understood as the angle between the navigation satellite's line of sight and the local horizontal plane.

[0022] In this embodiment, the relative position information of navigation satellites is used to determine whether they are potential interfering satellites. For example, the relative position information of navigation satellites can be compared with the observation range of a phased array radio telescope, and potential interfering satellites can be identified based on the comparison result. Specifically, the observation range of the phased array radio telescope is obtained, and navigation satellites are compared sequentially. If the relative position information of the current navigation satellite falls within the observation range, the current navigation satellite is identified as a potential interfering satellite, thereby identifying one or more potential interfering satellites. When determining the observation range of the phased array radio telescope, the influence of beam sidelobes should also be considered; for cases with poor sidelobe suppression, the observation range used for judgment should be appropriately expanded.

[0023] S3: Acquire the broadband signal collected by the phased array radio telescope, decompose the broadband signal into multiple sub-bands, identify multiple interfering sub-bands in the sub-bands, match the interfering sub-band with the potential interfering satellite for any interfering sub-band, and determine the sub-band interference information of the interfering sub-band based on the matching result.

[0024] The aforementioned broadband signal can be understood as an electromagnetic signal received by a phased-array radio telescope. It may contain target signals, noise, and radio frequency interference, and has a wide frequency range, with bandwidth determined by the receiving filter and sampling rate. A polyphase filter divides the broadband signal into multiple narrower frequency bands, each serving as a sub-band, facilitating independent analysis and processing of signals in different frequency bands. The aforementioned interfered sub-band can be understood as the sub-band whose frequency band is affected by interference.

[0025] In this embodiment, multiple interfered sub-bands are identified among multiple sub-bands of the broadband signal. Specifically, within each sub-band, the power characteristics of the signal are detected to determine whether the sub-band is interfered with. If the power of a sub-band increases beyond a set threshold, the sub-band is considered to be potentially interfered with, and the current sub-band is designated as an interfered sub-band.

[0026] In this embodiment, the detected jammed subband is matched with potential jamming satellites to determine the subband interference information. This subband interference information includes relevant information about the matched potential jamming satellites, such as their number, operating frequency, operating bandwidth, Doppler frequency, azimuth angle, and elevation angle. Specifically, matching can be performed based on parameters such as the operating frequency and bandwidth of the potential jamming satellites, as well as the frequency position and bandwidth of the jammed subband. For example, if the frequency range of a certain jammed subband coincides with or partially overlaps with the operating frequency range of a potential jamming satellite, then that potential jamming satellite is considered a possible source of interference for the current jammed subband. Furthermore, the relevant information of all matched potential jamming satellites for the current jammed subband is obtained as the subband interference information.

[0027] In one embodiment, the sub-band interference information of each interfered sub-band can be expressed as a set. Specifically, a set of potential interfering satellites corresponding to any interfered sub-band is constructed. , , ,in, This represents the number of operating frequencies corresponding to the nth potential interfering satellite. Let n be the number of the nth potential interfering satellite. For the m-th operating frequency of the n-th potential interfering satellite, For the m-th operating bandwidth of the n-th potential interfering satellite, , Let be the azimuth angle of the nth potential interfering satellite. Let be the elevation angle of the nth potential interfering satellite.

[0028] S5: Determine the signal subspace of the interfered sub-band based on the system beam distribution, obtain the interference subspace based on the sub-band interference information, determine the oblique projection matrix of the interfered sub-band based on the interference subspace and the signal subspace, perform interference reduction on the interfered sub-band based on the oblique projection matrix and the signal subspace, and simultaneously perform digital beamforming on the interfered sub-band based on the oblique projection matrix and the signal subspace.

[0029] The aforementioned signal subspace characterizes the desired array response pattern of a specific beam pointing at a specific sub-band frequency, and can be constructed using the steering vector of the specific beam pointing at that sub-band frequency. The aforementioned interference subspace represents the influence of multiple interfering satellites on the two-dimensional spatial and frequency domains of the sub-band, and can be obtained by the distribution of phased array elements combined with azimuth, elevation, and sub-band frequencies. The aforementioned oblique projection matrix is ​​calculated using the signal and interference subspaces and is used to suppress radio frequency interference while preserving the desired signal. Specifically, the received signal is projected through this oblique projection matrix to suppress interference components in the data while preserving the desired signal. This process effectively improves signal quality and detectability, ultimately reducing the continuous interference from phased array radio telescopes to on-orbit satellites.

[0030] In this embodiment, an oblique projection matrix is ​​determined based on the signal subspace and interference subspace of the interfered subband, and interference reduction of the interfered subband is achieved through the oblique projection matrix. Specifically, by acquiring the relative position information of the navigation satellite relative to the phased array radio telescope, such as azimuth and elevation angles, and comparing it with the telescope's observation range or signal azimuth source, potential interfering satellites that may generate radio frequency interference can be accurately identified, clarifying the target direction for subsequent interference reduction. Furthermore, subband interference information, including interference source number, operating frequency, and Doppler frequency, is acquired, achieving a fine representation of the interference. By determining the oblique projection matrix based on the signal subspace and interference subspace of the interfered subband, and processing the interfered subband using the oblique projection matrix, the desired signal can be preserved while effectively suppressing continuous interference from potential interfering satellites, thus achieving the reduction of continuous interference from on-orbit satellites by the phased array radio telescope.

[0031] In one possible implementation, the aforementioned relative position information is used to characterize the spatial position information of the navigation satellite relative to the phased array radio telescope. Based on this, the relative position information of multiple navigation satellites can be obtained according to the vector information of the navigation satellite. The specific steps are as follows: obtaining the vector information of the navigation satellite, the vector information including the target position vector and the target velocity vector, and determining the relative position information of the navigation satellite according to the vector information, wherein the vector information is based on the northeast-northeast coordinate system.

[0032] In this embodiment, the aforementioned vector information includes a target position vector and a target velocity vector, and is obtained based on a northeast-northeast coordinate system centered on the location of the phased array radio telescope. This northeast-northeast coordinate system is suitable for observation on the Earth's surface and facilitates the description of the navigation satellite's position relative to the phased array radio telescope. In the northeast-northeast coordinate system, the x-axis points to geographic east, the y-axis points to geographic north, and the z-axis points vertically upwards towards the sky. The aforementioned target position vector can be understood as a vector pointing from the phased array radio telescope's location to the navigation satellite, representing the satellite's position in space. The aforementioned target velocity vector can be understood as a vector representing the magnitude and direction of the navigation satellite's velocity, used to reflect the navigation satellite's operational status.

[0033] In this embodiment, by determining the relative position information using the vector information of navigation satellites, the position and motion state of the navigation satellites relative to the phased array radio telescope can be obtained, thereby identifying potential interfering satellites. Specifically, the azimuth and elevation angles of the satellites relative to the phased array radio telescope can be calculated based on the target position vector and target velocity vector of the navigation satellites as relative position information. Based on this relative position information, it can be determined which navigation satellites might interfere with the radio telescope's observations. Optionally, the angle projected onto the horizontal plane of the northeast-sky coordinate system can be used as the azimuth angle, and the angle projected onto the vertical plane of the northeast-sky coordinate system can be used as the elevation angle. Optionally, the azimuth and elevation angles measured in other coordinate systems can also be converted to the azimuth and elevation angles in the northeast-sky coordinate system.

[0034] In one implementation, since it is difficult to measure the position and calculate the orbit of navigation satellites in the northeast-northeast coordinate system, a coordinate transformation can be performed between the true equatorial mean boundary coordinate system and the geocentric-ground-fixed coordinate system to obtain the vector information of each navigation satellite. The true equatorial mean boundary coordinate system is an inertial coordinate system with the Earth's center as the origin and the equatorial plane as the reference; the orbital parameters of navigation satellites are easier to describe in this system. The geocentric-ground-fixed coordinate system is a geocentric-ground-fixed coordinate system with the Earth's center as the origin, which corresponds to the geographical coordinates on the Earth's surface, facilitating the unification of global navigation satellites into a single coordinate system.

[0035] In this embodiment, by converting vector information in the geocentric-fixed coordinate system to vector information in the northeast-sky coordinate system, a more comprehensive understanding of the relative position information of all navigation satellites can be obtained, thereby more accurately representing the relative position information in the northeast-sky coordinate system. Please refer to [link / reference]. Figure 2 The conversion of vector information in the geocentric-fixed coordinate system to vector information in the northeast-sky coordinate system specifically includes the following steps:

[0036] S31: Obtain the position information of the phased array radio telescope, the position information representing the telescope coordinate parameters in the geocentric-earth-fixed coordinate system, and determine the basic position vector and rotation matrix of the phased array radio telescope based on the position information, the rotation matrix being used for coordinate transformation between the geocentric-earth-fixed coordinate system and the northeast-sky coordinate system.

[0037] S33: Obtain the first position vector and the first velocity vector of the navigation satellite, and determine the relative position vector between the navigation satellite and the phased array radio telescope based on the first position vector and the basic position vector.

[0038] S35: Determine the target position vector based on the rotation matrix and the relative position vector, and determine the target velocity vector based on the rotation matrix and the target position vector, and define the target position vector and the target velocity vector as the vector information.

[0039] In step S31 above, the telescope coordinate parameters can be the longitude of the phased array radio telescope in the geocentric-Earth-fixed coordinate system. ,latitude and height The aforementioned basic position vector is the position vector of the phased array radio telescope in the geocentric-fixed coordinate system, and the aforementioned rotation matrix is ​​used for the conversion of vector information in different coordinate systems. The basic position vector and rotation matrix of the phased array radio telescope are determined based on the telescope coordinate parameters. Specifically, the basic position vector... Rotation matrix ,in, , , (rice).

[0040] In step S33 above, the first position vector and the first velocity vector are vector information of the navigation satellite in a geocentric-ground-fixed coordinate system, and the relative position vector is used to describe the relative positional relationship between the navigation satellite and the phased array radio telescope in the geocentric-ground-fixed coordinate system. Specifically, the first position vector and the first velocity vector of the navigation satellite are obtained, and the relative position vector is determined based on the first position vector and the base position vector. , ,in, The first position vector, This is the first velocity vector.

[0041] In step S35 above, the target position vector and the target velocity vector are vector information of the navigation satellite in the northeast-northeast coordinate system. Specifically, the target position vector... The aforementioned target velocity vector .

[0042] In this embodiment, the relative position information of the navigation satellite is further determined based on vector information. This relative position information may include azimuth, elevation, radial velocity, and Doppler frequency. The radial velocity can be understood as the relative motion velocity component of the navigation satellite relative to the phased array radio telescope along their line of sight, and the Doppler frequency can be understood as the received signal frequency offset caused by the relative radial motion between the navigation satellite and the phased array radio telescope.

[0043] Specifically, the satellite coordinate parameters of the navigation satellite are determined based on the target position vector of the navigation satellite, and the aforementioned satellite coordinate parameters include a first direction parameter. Second direction parameter and third-party parameters These parameters are used to characterize the coordinates of the navigation satellite on the x-axis, y-axis, and z-axis of the northeast celestial coordinate system, respectively. Further, the azimuth angle is determined based on the first and second direction parameters. The pitch angle is determined based on the first directional parameter, the second directional parameter, and the third directional parameter. And determine the radial velocity based on the target position vector and the target velocity vector. The Doppler frequency is determined based on the target velocity vector. ,in, The operating frequency of navigation satellites, The speed of electromagnetic waves in a medium is usually taken as the speed of light, i.e., 3 × 10⁻⁶. 8 m / s.

[0044] In one embodiment, the aforementioned pitch angle can be a pitch angle corrected for atmospheric refraction. Since radio signals experience path bending due to refraction as they pass through the atmosphere, affecting the observation of the pitch angle, the pitch angle can be corrected using the following empirical formula: , ,in, The Earth's surface refractive index. 315×10 -6 , For tropospheric thickness, , For the Earth's radius, , This is the corrected pitch angle.

[0045] In this embodiment, when obtaining the first position vector and the first velocity vector using the geocentric-fixed coordinate system, since the orbital parameters of the navigation satellite are easier to describe in the true equatorial mean boundary coordinate system, obtaining the vector information in the true equatorial mean boundary coordinate system and converting it to the vector information in the geocentric-fixed coordinate system includes the following steps:

[0046] S41: Obtain the orbital parameters of multiple navigation satellites, and determine the current position vector and current velocity vector of the navigation satellites based on the orbital parameters. The current position vector and the current velocity vector are based on the true equatorial mean boundary coordinate system.

[0047] S43: Obtain the transformation parameters of the geocentric coordinate system, convert the current position vector into the first position vector according to the transformation parameters, and convert the current velocity vector into the first velocity vector according to the transformation parameters.

[0048] In step S41, the aforementioned current position vector and current velocity vector are vector information of the navigation satellite in the true equatorial mean boundary coordinate system. Specifically, these can be obtained based on the navigation satellite's orbital parameters, which are used to predict the navigation satellite's orbital position in the next few days. The current position vector and current velocity vector are obtained by predicting the navigation satellite's orbital parameters based on these parameters. For example, text information from a TLE file can be used as the source of the orbital parameters. A TLE file is a commonly used file in the industry to describe the basic orbital parameters of objects in Earth's orbit. Further, the SDP4 model is used to calculate the current position and velocity of the navigation satellite based on the orbital parameters, which are then used as the current position vector and current velocity vector.

[0049] In step S43, the aforementioned transformation parameters of the geocentric-ground-fixed coordinate system are used to realize the transformation of vector information between the true equatorial mean boundary coordinate system and the geocentric-ground-fixed coordinate system. Its core is to map the orbital parameters of the navigation satellite to the geocentric-ground-fixed coordinate system by considering factors such as the Earth's rotation. Specifically, the aforementioned first position vector... ,in, The above is the current position vector. For Greenwich Mean Time (GMT), As the conversion parameters mentioned above, The aforementioned first velocity vector ,in, The above is the current velocity vector. It should be noted that, It is a timescale based on the Earth's rotation and is calculated using UTC time.

[0050] In one possible implementation, potential interfering satellites are identified among multiple navigation satellites based on the azimuth and elevation angles of the navigation satellites. Specifically, the azimuth and elevation angles of each navigation satellite are obtained, along with the observation range of the phased array radio telescope, which includes both the elevation and azimuth angle ranges. Further, if the azimuth angle of the current navigation satellite is within the azimuth angle range and the elevation angle of the navigation satellite is within the elevation angle range, then the current navigation satellite is identified as a potential interfering satellite, thereby identifying multiple potential interfering satellites among the multiple navigation satellites.

[0051] In this embodiment, the azimuth and elevation ranges of the phased array radio telescope are determined by the beams generated by the phased array elements. Specifically, the phased array antenna generates beams pointing in multiple directions, and the sky regions pointed to by each beam are taken as the observation range of the phased array radio telescope. These observation ranges can be further determined using elevation and azimuth angles to form the elevation and azimuth ranges of the phased array radio telescope. The azimuth range is... The above pitch angle range is Compare the azimuth angles of all navigation satellites with the aforementioned azimuth angle range, and compare the elevation angles of all navigation satellites with the aforementioned elevation angle range. If the azimuth angle of a navigation satellite is within the range... And the pitch angle is at If the current navigation satellite is identified as a potential interfering satellite, then multiple potential interfering satellites can be identified among multiple navigation satellites. For example, if the azimuth range observed by the current phased array radio telescope is [-180°, 180°] and the elevation range is [45°, 90°], and a certain navigation satellite has an azimuth of 60° and an elevation of 50°, then the current navigation satellite is identified as a potential interfering satellite.

[0052] In one possible implementation, multiple interfered sub-bands are determined from multiple sub-bands of a broadband signal by measuring the energy of the sub-bands. Specifically, the broadband signal is divided into multiple sub-bands using a polyphase filter, the energy of each sub-band is obtained, and the minimum energy is determined from the energy of the multiple sub-bands. Here, the aforementioned sub-bands refer to dividing the broadband signal into multiple narrower frequency bands, for example, dividing the broadband signal into 1250 sub-bands, each with a bandwidth of 0.96MHz. Each sub-band contains multiple sampling points, and the aforementioned energy can be understood as the total power or energy of the signal within each sub-band. The energy of the current sub-band can be determined by summing the energy of all sampling points within the sub-band.

[0053] Furthermore, since radio signals are inherently weak, and the power of navigation satellite signals is far higher than the background noise of phased array radio telescopes, if the energy of a certain subband is significantly higher than that of other subbands or significantly higher than a preset condition, it can be determined that the subband is subject to interference. Specifically, for any subband, it is determined whether the energy of the subband meets the preset condition, and the subband that meets the preset condition is identified as the interfered subband. The preset condition is that the energy is greater than or equal to the product of a minimum energy and a preset threshold value.

[0054] For example, the subband frequency of each subband is ,in, The energy of each subband is ,in, The energy of the above subbands is calculated using the following formula: ,in, Let L be the l-th sample point in the n-th subband, L be the number of samples processed in this iteration, and K be the number of subbands. Further, the minimum energy is determined among multiple subbands. And set a threshold value When other subbands have energy When this happens, the sub-band is considered the interfered sub-band.

[0055] In one possible implementation, please refer to Figure 3 The process of matching the interfered subband with potential interfering satellites and determining the subband interference information based on the matching results specifically includes the following steps:

[0056] S71: Obtain the frequency information of one or more potential interfering satellites, determine the interference frequency range of each potential interfering satellite based on the frequency information, and obtain the sub-band frequency of each interfered sub-band.

[0057] S73: For any jammed sub-band, if the sub-band frequency of the jammed sub-band is within the jamming frequency range of any potential jamming satellite, then the potential jamming satellite is identified as the target jamming satellite of the jammed sub-band.

[0058] S75: Obtain the target azimuth and target elevation angles of each target jamming satellite, and determine the sub-band jamming information of the jammed sub-band based on the target azimuth and target elevation angles of the target jamming satellite.

[0059] In step S71, the aforementioned frequency information includes the operating frequency, operating bandwidth, and Doppler frequency of the potential jamming satellite. For any potential jamming satellite, the jamming frequency range of the current potential jamming satellite is determined based on its operating frequency, operating bandwidth, and Doppler frequency. Each potential jamming satellite has its own unique jamming frequency range. Specifically, the aforementioned jamming frequency range can be expressed as follows: ,in, For operating frequency, for The corresponding Doppler frequency, for The operating bandwidth corresponding to the frequency point.

[0060] In step S73, furthermore, potential jamming satellites that have an interference relationship with each jammed sub-band are identified, and these potential jamming satellites are designated as target jamming satellites. Specifically, the sub-band frequency of the jammed sub-band is matched with the interference frequency range of the potential jamming satellites to determine the target jamming satellite corresponding to the jammed sub-band.

[0061] In step S75, the sub-band interference information may include the satellite number, operating frequency, azimuth angle, and elevation angle of the target jamming satellite corresponding to the jammed sub-band. Specifically, the sub-band interference information can be expressed in the following manner: ,in, This indicates that in the current subband i, there is Several satellites caused interference. Indicates the first The azimuth angle of each satellite, Indicates the first The elevation angle of a satellite. The value of j ranges from 1 to J.

[0062] In one possible implementation, an oblique projection matrix is ​​generated using the signal subspace and the interference subspace to precisely reduce navigation satellite radio frequency interference for each beam. For any interfered subband, the signal subspace of the interfered subband on any beam is first determined based on the phased array beam information of the phased array radio telescope and the subband frequency of the interfered subband. The phased array beam information can be understood as the direction of the phased array beam and the phase difference of each corresponding element. This phased array information can be obtained based on the coordinate parameters of the phased array elements and the beam direction. Further, for any interfered subband, an interference subspace is constructed based on its subband interference information. This interference subspace characterizes the spatial frequency distribution of the interference signal in the phased array and is used for subsequent projection reduction of radio frequency interference.

[0063] Specifically, the aforementioned phased array beam information can be obtained in the following manner: ,in, Indicates the first The phase difference corresponding to each array element, and the coordinates of the reference array element are... , No. The coordinates of each array element are , The operating frequency of the currently interfered sub-band. This represents the current beam direction. The aforementioned signal subspace can be obtained as follows: , Indicates that the interfered subband i is in the beam The signal subspace on, This represents the number of phased array elements. The aforementioned interference subspace can be obtained as follows: ,in, , For the first The height with the first The antenna, the first The phase difference corresponding to each interference.

[0064] Furthermore, an orthogonal projection matrix of the interfered sub-band is established based on the interference subspace, and an oblique projection matrix of the interfered sub-band is determined based on the orthogonal projection matrix and the signal subspace. The orthogonal projection matrix can be determined as follows: The above Represents the orthogonal projection matrix. Let I represent the interference subspace of the interfered subband, and let I denote a diagonal matrix. For an operating frequency of... The interfered sub-band in the beam The oblique projection matrix on the surface can be determined in the following way: Among them, the above Represents the oblique projection matrix. Indicates the interfering subband in the beam The signal subspace on, This represents the orthogonal projection matrix.

[0065] Furthermore, the received data matrix of any interfered sub-band is obtained. This matrix is ​​composed of signal samples from the interfered sub-bands of multiple array elements. The above received data matrix can be expressed as follows: ,in, For the number of elements in a phased array, This represents the number of sample points for the signal. For the beam... Interference reduction and digital beamforming of the interfered subbands can be performed in the following manner: ,in, It is the oblique projection matrix. It is the conjugate transpose of the signal subspace.

[0066] It should be noted that during the operation of a phased array radio telescope, multiple beams are generated to detect and receive broadband signals. Based on this, when performing interference reduction on any interfered subband, all beams should be traversed to construct signal and interference subspaces. For any interfered subband, all beams are traversed, and the corresponding signal subspace is constructed according to the beam direction. For example, with 90 beams, one interfered subband should form 90 signal subspaces and one interference subspace. Further, using the signal and interference subspaces, all subbands and beams are traversed, and the oblique projection matrix corresponding to each subband and each beam is calculated. The oblique projection matrix is ​​then used to perform interference reduction on the interfered subband.

[0067] In one embodiment, see Figure 4 , Figure 4 The diagram shows the composition of a phased array. In this embodiment, the phased array is composed of an array of 112 array elements, which are evenly arranged. The beam pointing set is used as the observation range of the phased array radio telescope. The observation range can be further determined by the elevation angle and azimuth angle to form the elevation angle range and azimuth angle range of the phased array radio telescope.

[0068] In one embodiment, there exists a scenario involving two broadband interferences and a single-carrier signal. The pitch and azimuth angles of the interferences and the signal differ, as shown in Figures 5(a) and 5(b). Figure 5(a) shows the power spectrum of the received data after conventional beamforming processing, where the two broadband interferences still exist. Figure 5(b) shows the power spectrum of the received data after interference reduction and conventional beamforming processing. The original broadband interference is significantly reduced to below the noise floor after interference reduction processing, making the target signal easier to detect and analyze. This process verifies the effectiveness of the proposed interference reduction method.

[0069] Please see Figure 6 This application also provides a radio frequency interference reduction device for a phased array radio telescope, the device comprising:

[0070] The parameter acquisition unit 100 is used to acquire the relative position information of multiple navigation satellites and determine potential interfering satellites among the multiple navigation satellites based on the relative position information, wherein the relative position information includes at least azimuth and elevation angles;

[0071] The interference determination unit 200 is used to acquire broadband signals collected by phased array radio telescopes, decompose the broadband signals into multiple subbands, determine multiple interfered subbands in the subbands, match the interfered subband with the potential interfering satellite for any interfered subband, and determine the subband interference information of the interfered subband based on the matching result.

[0072] The interference reduction unit 300 is used to determine the signal subspace of the interfered subband according to the system beam distribution, obtain the interference subspace according to the subband interference information, determine the oblique projection matrix of the interfered subband based on the interference subspace and the signal subspace, perform interference reduction on the interfered subband according to the oblique projection matrix and the signal subspace, and perform digital beamforming on the interfered subband according to the oblique projection matrix and the signal subspace.

[0073] in,

[0074] In one embodiment, the parameter acquisition unit 100 is specifically used to acquire vector information of any navigation satellite, the vector information including target position vector and target velocity vector, and determine the relative position information of the navigation satellite based on the vector information, the relative position information including azimuth angle, elevation angle, radial velocity and Doppler frequency, and identify potential interfering satellites among the multiple navigation satellites based on the relative position information of each navigation satellite and the observation range of the phased array radio telescope.

[0075] In one embodiment, the interference determination unit 200 is specifically configured to divide the broadband signal into multiple sub-bands, determine whether the energy of any sub-band meets a preset condition for each sub-band, determine the sub-band that meets the preset condition as the interfered sub-band, and if the sub-band frequency of the interfered sub-band is within the interference frequency range of any potential interfering satellite, then determine the potential interfering satellite as the target interfering satellite of the interfered sub-band, and determine the sub-band interference information of the interfered sub-band based on the relative position information of the target interfering satellite.

[0076] In one embodiment, the interference reduction unit 300 is specifically configured to acquire the phased array information of the phased array radio telescope and the sub-band frequency of the interfered sub-band, determine the signal subspace based on the phased array information and the sub-band frequency, construct the interference subspace of the interfered sub-band based on the sub-band interference information of the interfered sub-band, establish the orthogonal projection matrix of the interfered sub-band based on the interference subspace, determine the oblique projection matrix of the interfered sub-band based on the orthogonal projection matrix and the signal subspace, and perform interference reduction and digital beamforming on the interfered sub-band based on the oblique projection matrix and the signal subspace.

[0077] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0078] For ease of description, the above devices are described separately by function as various units. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware.

[0079] Those skilled in the art will understand that embodiments of this application can be provided as methods or apparatus. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0080] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the apparatus embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0081] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

[0082] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for reducing radio frequency interference in a phased array radio telescope, characterized in that, The method includes: The relative position information of multiple navigation satellites is obtained, and potential interfering satellites are identified among the multiple navigation satellites based on the relative position information, wherein the relative position information includes at least azimuth and elevation angles; The broadband signal acquired by the phased array radio telescope is decomposed into multiple sub-bands, and multiple interfering sub-bands are identified in the sub-bands. For any interfering sub-band, the interfering sub-band is matched with the potential interfering satellite, and the sub-band interference information of the interfering sub-band is determined according to the matching result. The signal subspace of the interfered sub-band is determined based on the phased array beam distribution. The interference subspace is obtained based on the sub-band interference information. The oblique projection matrix of the interfered sub-band is determined based on the interference subspace and the signal subspace. The interference of the interfered sub-band is reduced based on the oblique projection matrix and the signal subspace. At the same time, digital beamforming is performed on the interfered sub-band based on the oblique projection matrix and the signal subspace. The process of matching the interfered subband with the potential interfering satellite and determining the subband interference information of the interfered subband based on the matching result includes: Obtain the frequency information of one or more potential interfering satellites, determine the interference frequency range of each potential interfering satellite based on the frequency information, and obtain the sub-band frequency of each interfered sub-band. If the subband frequency of the interfered subband is within the interference frequency range of any of the potential interfering satellites, then the potential interfering satellite is identified as the target interfering satellite of the interfered subband. Obtain the target azimuth and target elevation angles of each of the target jamming satellites, and determine the sub-band jamming information of the jammed sub-band based on the target azimuth and target elevation angles of each of the target jamming satellites; The process of determining the signal subspace of the interfered sub-band based on the phased array beam distribution, obtaining the interference subspace based on the sub-band interference information, and determining the oblique projection matrix of the interfered sub-band based on the interference subspace and the signal subspace includes: The phased array beam information of the phased array radio telescope and the sub-band frequency of the interfered sub-band are obtained. The signal subspace is determined based on the phased array beam information and the sub-band frequency. The interference subspace of the interfered sub-band is constructed based on the sub-band interference information of the interfered sub-band. The orthogonal projection matrix of the interfered sub-band is established based on the interference subspace, and the oblique projection matrix of the interfered sub-band is determined based on the orthogonal projection matrix and the signal subspace.

2. The method according to claim 1, characterized in that, The relative position information is used to characterize the position information of the navigation satellite relative to the phased array radio telescope; Obtaining the relative position information of multiple navigation satellites includes: For any navigation satellite, obtain the vector information of the navigation satellite, the vector information including the target position vector and the target velocity vector, and determine the relative position information of the navigation satellite based on the vector information, wherein the vector information is based on the northeast-northeast coordinate system.

3. The method according to claim 2, characterized in that, Obtaining the vector information of the navigation satellites includes: The position information of the phased array radio telescope is obtained, and the position information represents the telescope coordinate parameters in the geocentric-earth-fixed coordinate system. The basic position vector and rotation matrix of the phased array radio telescope are determined based on the position information. The rotation matrix is ​​used for coordinate transformation between the geocentric-earth-fixed coordinate system and the northeast-sky coordinate system. For any navigation satellite, obtain the first position vector and the first velocity vector of the navigation satellite, and determine the relative position vector between the navigation satellite and the phased array radio telescope based on the first position vector and the base position vector; The target position vector is determined based on the rotation matrix and the relative position vector, and the target velocity vector is determined based on the rotation matrix and the target position vector. The target position vector and the target velocity vector are then used as the vector information.

4. The method according to claim 3, characterized in that, The first position vector and the first velocity vector are based on a geocentric coordinate system; obtaining the first position vector and the first velocity vector of the navigation satellite includes: Obtain the orbital parameter text of the navigation satellite, and determine the current position vector and current velocity vector of the navigation satellite based on the orbital parameter text. The current position vector and the current velocity vector are based on the true equatorial mean boundary coordinate system. Obtain the transformation parameters of the geocentric coordinate system, convert the current position vector into the first position vector according to the transformation parameters, and convert the current velocity vector into the first velocity vector according to the transformation parameters.

5. The method according to claim 2, characterized in that, The relative position information also includes radial velocity and Doppler frequency; determining the relative position information of the navigation satellite based on the vector information includes: The satellite coordinate parameters of the navigation satellite are determined based on the target position vector of the navigation satellite. The satellite coordinate parameters include a first direction parameter, a second direction parameter, and a third direction parameter. The satellite coordinate parameters are used to characterize the coordinate parameters of the navigation satellite on different directional axes in the northeast celestial coordinate system. The azimuth angle is determined based on the first direction parameter and the second direction parameter, the pitch angle is determined based on the first direction parameter, the second direction parameter and the third direction parameter, the radial velocity is determined based on the target position vector and the target velocity vector, and the Doppler frequency is determined based on the target velocity vector.

6. The method according to claim 1, characterized in that, Based on the relative position information, potential interfering satellites are identified from among the multiple navigation satellites, including: The azimuth and elevation angles of each navigation satellite are obtained, and the observation range of the phased array radio telescope is obtained, the observation range including the elevation angle range and the azimuth angle range; For any navigation satellite, if the azimuth angle of the navigation satellite is within the azimuth angle range and the elevation angle of the navigation satellite is within the elevation angle range, then the navigation satellite is determined to be a potential interference satellite.

7. The method according to claim 1, characterized in that, Decomposing the broadband signal into multiple sub-bands, and identifying multiple interfered sub-bands within the sub-bands, includes: The energy of each subband is obtained, and the minimum energy is determined among the energies of the multiple subbands; For any subband, determine whether the energy of the subband meets a preset condition, and determine the subband that meets the preset condition as the interfered subband, wherein the preset condition is that the energy of the subband is greater than or equal to the product of the minimum energy and the preset threshold value.

8. A radio frequency interference reduction device for a phased array radio telescope, characterized in that, The device includes: A parameter acquisition unit is used to acquire the relative position information of multiple navigation satellites and determine potential interfering satellites among the multiple navigation satellites based on the relative position information, wherein the relative position information includes at least azimuth and elevation angles; The interference determination unit is used to acquire broadband signals collected by phased array radio telescopes, decompose the broadband signals into multiple sub-bands, identify multiple interfered sub-bands in the sub-bands, match the interfered sub-band with the potential interfering satellite for any interfered sub-band, and determine the sub-band interference information of the interfered sub-band based on the matching result. An interference reduction unit is configured to determine the signal subspace of the interfered sub-band based on the phased array beam distribution, obtain the interference subspace based on the sub-band interference information, determine the oblique projection matrix of the interfered sub-band based on the interference subspace and the signal subspace, perform interference reduction on the interfered sub-band based on the oblique projection matrix and the signal subspace, and simultaneously perform digital beamforming on the interfered sub-band based on the oblique projection matrix and the signal subspace. The process of matching the interfered subband with the potential interfering satellite and determining the subband interference information of the interfered subband based on the matching result includes: Obtain the frequency information of one or more potential interfering satellites, determine the interference frequency range of each potential interfering satellite based on the frequency information, and obtain the sub-band frequency of each interfered sub-band. If the subband frequency of the interfered subband is within the interference frequency range of any of the potential interfering satellites, then the potential interfering satellite is identified as the target interfering satellite of the interfered subband. Obtain the target azimuth and target elevation angles of each of the target jamming satellites, and determine the sub-band jamming information of the jammed sub-band based on the target azimuth and target elevation angles of each of the target jamming satellites; The process of determining the signal subspace of the interfered sub-band based on the phased array beam distribution, obtaining the interference subspace based on the sub-band interference information, and determining the oblique projection matrix of the interfered sub-band based on the interference subspace and the signal subspace includes: The phased array beam information of the phased array radio telescope and the sub-band frequency of the interfered sub-band are obtained. The signal subspace is determined based on the phased array beam information and the sub-band frequency. The interference subspace of the interfered sub-band is constructed based on the sub-band interference information of the interfered sub-band. The orthogonal projection matrix of the interfered sub-band is established based on the interference subspace, and the oblique projection matrix of the interfered sub-band is determined based on the orthogonal projection matrix and the signal subspace.

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