CN115469337A - Satellite navigation system multipath interference signal identification method based on two-dimensional focusing analysis - Google Patents
Satellite navigation system multipath interference signal identification method based on two-dimensional focusing analysis Download PDFInfo
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- CN115469337A CN115469337A CN202210985349.XA CN202210985349A CN115469337A CN 115469337 A CN115469337 A CN 115469337A CN 202210985349 A CN202210985349 A CN 202210985349A CN 115469337 A CN115469337 A CN 115469337A
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- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
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Abstract
The invention relates to a satellite navigation system multipath interference signal identification method based on two-dimensional focusing analysis, belongs to the technical field of Global Navigation Satellite System (GNSS) positioning, and particularly relates to a multipath interference signal self-adaptive identification method for a satellite navigation system. Firstly, carrying out two-dimensional focusing imaging on direct wave data; then, the position of multipath interference is found in the direct wave imaging result, and the angle of the multipath signal source is calculated according to the focused position of the multipath interference, so that the high-precision identification of the multipath interference signal is achieved. The method solves the problem that the multipath signals are difficult to accurately identify in a navigation satellite positioning system, effectively reduces the ranging error of the system, reduces the operation amount processed by the system, improves the positioning accuracy and has practical application value.
Description
Technical Field
The invention relates to a satellite navigation system multipath interference signal identification method based on two-dimensional focusing analysis, belongs to the technical field of Global Navigation Satellite System (GNSS) positioning, and particularly relates to a multipath interference signal self-adaptive identification method for a satellite navigation system.
Background
Global satellite navigation systems use signals transmitted from satellites orbiting the earth to resolve the position, velocity, and precise time of a receiver. The GNSS positioning can solve the self coordinates only by receiving signals of at least 4 satellites, and in an open outdoor environment, the terminal can smoothly receive enough satellite signals to realize high-precision positioning. However, because GNSS signals belong to electromagnetic signals, in environments such as cities and mountains, the signals may be reflected by objects such as buildings and mountains, so that multipath signal interference is formed, and high-precision positioning is difficult to achieve.
Signals transmitted by the GNSS satellite can be reflected by an object near the antenna and then reach the receiving antenna, and when a plurality of propagation paths occur, multipath interference occurs, which seriously affects the positioning accuracy and reliability of the system. Multipath interference is a significant error source of GNSS positioning, and compared with direct wave signals, multipath signals have a delayed phase due to a lengthened path, and the amplitude of the multipath signals also changes in the reflection or scattering process, thereby reducing the ranging accuracy of the receiver.
For the suppression of multipath signals, there are three general approaches, namely filtering in the frequency domain, time domain and space domain. Frequency domain filtering refers to the suppression effect achieved by filtering out some unnecessary frequency components in the frequency domain; the time domain filtering takes the multipath signals as delay signals of the reference signals, and filters the delay components according to certain criteria; spatial filtering is the use of a shaped beam to pass a desired signal or a signal in a desired direction and to suppress interference in undesired directions. In spatial filtering, the direction of multipath signal interference needs to be estimated and calculated. However, the traditional direction-of-arrival estimation algorithm has a large calculation amount and large multipath signal identification errors, so that the accuracy of the measurement result is poor.
Disclosure of Invention
In view of this, the invention provides a method for identifying multipath interference signals of a satellite navigation system based on two-dimensional focusing analysis, which mainly comprises the steps of constructing a multipath interference model, carrying out two-position focusing by using a direct wave signal, judging the position of multipath interference in an imaging graph, further calculating the arrival direction of the multipath interference signals, and realizing high-precision identification of the multipath interference signals.
The invention is realized by the following technical scheme.
A satellite navigation system multipath interference signal identification method based on two-dimensional focusing analysis comprises the following steps:
acquiring a navigation signal by using a receiving antenna to obtain direct wave data, and recording the relative geometric position of the receiving antenna and the ground;
step two, carrying out two-dimensional focusing imaging by using the direct wave data acquired in the step one and the recorded relative geometric position of the receiving antenna and the ground to obtain a direct wave image;
step three, identifying the multipath signals in the direct wave image obtained in the step two, and recording the interference positions of the multipath signals;
and step four, calculating the angle of the multipath signal reaching the receiving antenna according to the interference position of the multipath signal recorded in the step three, and finishing the identification of the multipath interference signal of the satellite navigation system based on two-dimensional focusing analysis.
In the first step, when the receiving antenna is used for collecting the navigation signal, the time is not less than 600s;
in the second step, a BP algorithm is adopted for imaging, and the BP imaging step is as follows: firstly, grid division is carried out on an imaging plane, distance pulse compression is carried out on navigation signals, then the distance from a satellite to each grid is calculated, azimuth imaging is realized, and therefore a two-dimensional focusing imaging result of the navigation signals is obtained;
in the third step, the direct wave response is extracted, the amplitude of the residual image is evaluated, and the position of multipath interference is found out;
in the fourth step, the parameter information of each multipath source is calculated by utilizing the focusing position of the multipath interference and combining the position of the direct wave antenna;
assuming the location of some multipath signal interference with (x) n ,y n ) Indicate, and receiver position is noted as (x) a ,y a ) And the direction of the antenna forms an angle theta with the true north direction a The angle theta between the multipath signal interference and the true north direction n Expressed as:
the angle theta of the strip of multi-path interference signal reaching the antenna i Comprises the following steps:
θ i ＝θ n -θ a
in the same way, the angles of other multipath signals in the image reaching the receiving antenna can be calculated, so that high-precision self-adaptive identification of each multipath signal is realized.
Advantageous effects
(1) The method solves the problem that the multipath signals are difficult to accurately identify in a navigation satellite positioning system, effectively reduces the ranging error of the system, reduces the calculation amount processed by the system, improves the positioning accuracy and has practical application value;
(2) The invention discloses a satellite navigation system multipath interference signal high-precision identification method based on two-dimensional focusing analysis. Firstly, carrying out two-dimensional focusing imaging on direct wave data; then, the position of multipath interference is found in the direct wave imaging result, and the angle of the multipath signal source is calculated according to the focused position of the multipath interference, so that the high-precision identification of the multipath interference signal is achieved.
Drawings
Fig. 1 is a schematic diagram of a multipath interference configuration of a navigation signal.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Fig. 1 is a schematic diagram of multipath interference of a navigation signal in this embodiment, specifically: the navigation satellite transmitting signal is received by the receiver, the direct wave signal is a signal which is directly received, but the satellite signal may be received by the receiving antenna after being reflected and diffracted by a plurality of obstacles in the scene, the phase of the satellite signal is delayed, the amplitude of the satellite signal is weakened, and the satellite signal and the direct wave signal are superposed together to generate an error, so that multipath interference is caused, and the performance of a navigation positioning system is influenced.
After signal acquisition, demodulation, and the like, the signal received by the receiving antenna can be represented as:
in the formula, as (t- τ) m )exp(j2πf d ) Representing the received echo signals, where A represents the echo amplitude, s (t) is the satellite transmitted signal, τ m And f d Respectively representing the time delay and the Doppler frequency of the echo signal;
one multipath signal of the satellite is shown, subscript i represents the ith multipath signal in the multipath, W is the number of the multipath, and omega i Denotes the gain of the ith multipath n Is the time delay of the multipath signal; e.g. of the type s (t) is the noise of the echo channel.
In actual imaging, interference is caused by multipath signals, and since the multipath signals are received by the antenna, a response of the multipath signals occurs, reducing image quality. Therefore, a spatial filtering method is considered, so that a receiving antenna directional diagram forms narrow nulls in the arrival direction of multipath signals, and the problem of multipath interference is solved. However, the multipath signal paths are many and difficult to be identified accurately, so that it is difficult to estimate the directions of arrival of all multipath signals accurately.
Based on the above, the invention provides a method for identifying multipath signals with high precision, aiming at the problem that multipath interference in navigation positioning is difficult to identify accurately: firstly, imaging direct wave data; then finding out the position of the multipath interference in the imaging result, and calculating the angle of the multipath signal reaching the antenna according to the position; and adjusting an antenna directional diagram according to the angle to suppress multipath interference.
Examples
A method for high-precision identification of multipath signals comprises the following steps:
step one, direct wave data acquisition.
In this embodiment, a navigation satellite signal receiving system is built in the mature city of Jiangsu province, beidou2_ IGSO5 is used as a transmitting source, a data acquisition experiment is performed in 2021, 7 months and 5 days, and an experiment topological structure is shown in FIG. 1. And (3) carrying out long-time (not less than 600 seconds) data acquisition on the navigation signals, and recording the positions of the receiving antennas.
And step two, two-dimensional focusing of the navigation signals.
And (2) carrying out two-dimensional focusing imaging on the long-time navigation signal acquired in the step one, selecting the ground as a projection plane, taking the position of a receiving antenna as the original point of the imaging plane, synthesizing the frequency points B2a and B2B of the Beidou signal in order to obtain higher distance resolution, and finally adopting a BP algorithm to carry out imaging. The BP imaging procedure was as follows: firstly, grid division is carried out on an imaging plane, distance pulse compression is carried out on navigation signals, then the distance from a satellite to each grid is calculated, azimuth imaging is achieved, and therefore a two-dimensional focusing imaging result of the navigation signals is obtained.
In this embodiment, two-dimensional focusing is performed on the navigation signal.
Step three, multi-path signal identification.
The response result of the satellite signal in the imaging graph is represented by a fuzzy function:
where P is the position of the target point and Q is the position of any target point in the vicinity. λ represents the carrier wavelength and c is the speed of light. Phi TP 、Φ RP The unit vectors from the transmitter and the receiver to the target point P are respectively. Beta is a double base angle of the earth,i.e. phi TP And phi RP The angle between theta is the unit vector of the direction of the bisector of the angle beta. Omega E Is the transmitter equivalent angular velocity, and xi is its equivalent direction of motion. p () and m () are autocorrelation functions of the distance direction and the azimuth direction, respectively.
In this embodiment, the response of the signal can be extracted according to the above formula, and then the noise level of the remaining image is estimated to be 190dB. There are still some images with amplitude higher than the noise, and the responses 10dB higher than the noise are all generated by the multipath signals.
Step four, extracting parameters of a multipath signal source;
assuming the position of a multipath interference signal by (x) n ,y n ) Indicate, and the receiver position is noted as (x) a ,y a ) And the direction of the antenna forms an included angle theta with the north direction a Then the angle theta between the multipath interference and the true north direction n Expressed as:
further, the angle theta of the multipath interference signal reaching the antenna is calculated i Comprises the following steps:
θ i ＝θ n -θ a (4)
in the same way, the angles of other multipath signals in the image reaching the receiving antenna can be calculated, so that high-precision self-adaptive identification of each multipath signal is realized.
In this embodiment, the interference caused by three multipath signals is respectively (430, 50), (478, 93), (553, 164), the receiver position is (0, 0), and the angle θ between the receiving antenna and the true north is a =45 °. According to the equations (3) and (4), the angles from the three multipath signals to the receiving antenna can be calculated to be 38.37 °, 33.99 ° and 28.48 °.
In summary, the invention provides a self-adaptive high-precision identification method for multipath interference signals of a satellite navigation system, which can accurately identify multipath interference signal sources, effectively reduce system ranging errors, reduce the computation amount of system processing, improve positioning precision and have practical application value.
The above embodiments only describe the design principle of the present invention, and the shapes and names of the components in the description may be different without limitation. Therefore, a person skilled in the art of the present invention can modify or substitute the technical solutions described in the foregoing embodiments; such modifications and substitutions do not depart from the spirit and scope of the present invention.
Claims (6)
1. A satellite navigation system multipath interference signal identification method based on two-dimensional focusing analysis is characterized by comprising the following steps:
acquiring a navigation signal by using a receiving antenna to obtain direct wave data, and recording the relative geometric position of the receiving antenna and the ground;
step two, performing two-dimensional focusing imaging by using the direct wave data acquired in the step one and the recorded relative geometric position of the receiving antenna and the ground to obtain a direct wave image;
step three, identifying the multipath interference signals in the direct wave image obtained in the step two, and recording the positions of the multipath interference signals;
and step four, calculating the angle of the multipath interference signal reaching the receiving antenna according to the position of the multipath interference signal recorded in the step three, and finishing the identification of the multipath interference signal of the satellite navigation system based on two-dimensional focusing analysis.
2. The method for identifying the multipath interference signal of the satellite navigation system based on the two-dimensional focusing analysis as claimed in claim 1, wherein:
in the first step, when the receiving antenna is used for collecting the navigation signal, the time is not less than 600s.
3. The method for identifying the multipath interference signal of the satellite navigation system based on the two-dimensional focusing analysis according to claim 1 or 2, wherein:
and in the second step, a BP algorithm is adopted for imaging when two-dimensional focusing imaging is carried out.
4. The method of claim 3, wherein the method comprises:
the imaging method comprises the following specific steps: firstly, grid division is carried out on an imaging plane, distance pulse compression is carried out on navigation signals, then the distance from a satellite to each grid is calculated, azimuth imaging is achieved, and a two-dimensional focusing imaging result of the navigation signals is obtained.
5. The method for identifying the multipath interference signal of the satellite navigation system based on the two-dimensional focusing analysis according to claim 1, 2 or 4, wherein:
in the third step, the method for identifying the multipath signals in the direct wave image comprises the following steps: and extracting direct wave response, and then evaluating the residual image amplitude after the direct wave response is extracted to find out the position of the multipath interference signal.
6. The method for identifying the multipath interference signal of the satellite navigation system based on the two-dimensional focusing analysis according to claim 1, 2 or 4, wherein:
in the fourth step, the method for calculating the angle at which the multipath interference signal reaches the receiving antenna comprises:
let the position of the multipath interference signal be (x) n ,y n ) The receiver position is (x) a ,y a ) The angle between the orientation of the receiving antenna and the north direction is theta a The included angle theta between the multipath interference signal and the north direction n Comprises the following steps:
the angle theta of the strip of multi-path interference signal reaching the receiving antenna i Comprises the following steps:
θ i ＝θ n -θ a 。
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| CN117848374A (en) * | 2024-03-07 | 2024-04-09 | 北京理工大学前沿技术研究院 | Vehicle-mounted anti-interference positioning method and system based on multi-source data fusion |
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| CN117848374A (en) * | 2024-03-07 | 2024-04-09 | 北京理工大学前沿技术研究院 | Vehicle-mounted anti-interference positioning method and system based on multi-source data fusion |
| CN117848374B (en) * | 2024-03-07 | 2024-05-24 | 北京理工大学前沿技术研究院 | Vehicle-mounted anti-interference positioning method and system based on multi-source data fusion |
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