CN111736187A - High-precision high-sensitivity single-satellite GNSS positioning method based on passive synthetic aperture - Google Patents

High-precision high-sensitivity single-satellite GNSS positioning method based on passive synthetic aperture Download PDF

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CN111736187A
CN111736187A CN202010572996.9A CN202010572996A CN111736187A CN 111736187 A CN111736187 A CN 111736187A CN 202010572996 A CN202010572996 A CN 202010572996A CN 111736187 A CN111736187 A CN 111736187A
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synthetic aperture
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CN111736187B (en
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郇浩
陶然
张莉婷
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Beijing Institute of Technology BIT
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    • G—PHYSICS
    • 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
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/393—Trajectory determination or predictive tracking, e.g. Kalman filtering
    • G—PHYSICS
    • 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
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position

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Abstract

The invention discloses a high-precision high-sensitivity single-satellite GNSS positioning method based on a passive synthetic aperture, and belongs to the technical field of wireless communication. The method comprises the steps of continuously receiving signals transmitted by a single navigation satellite, establishing a GNSS positioning model capable of accumulating long-time phases of the signals for the first time, namely utilizing an omnidirectional antenna to accumulate the long-time phases of the navigation signals in the satellite overhead process, synthesizing a receiving antenna virtual aperture with the diameter being several kilometers, measuring the azimuth position perpendicular to the motion track of the satellite and the distance position in the azimuth direction by changing the positioning principle from the traditional four-satellite ranging positioning at the zero Doppler moment, namely realizing the GNSS positioning of a target based on a high-precision high-sensitivity single satellite of a passive synthetic aperture. The method can realize high-precision and high-sensitivity GNSS positioning under the condition of insufficient visible satellites, and can improve the positioning performance under the noise condition. The noise comprises noise under the scenes of forest shielding, insufficient visible star number, weak signals and the like.

Description

High-precision high-sensitivity single-satellite GNSS positioning method based on passive synthetic aperture
Technical Field
The invention relates to a method for realizing GNSS positioning under a single satellite by utilizing a passive synthetic aperture technology, belonging to the technical field of wireless communication.
Background
In the traditional GNSS positioning method, a simultaneous equation set of transmission distances (pseudo distances) from a plurality of satellites to a user is utilized, and the position and clock error information of the user are solved on the basis. The traditional GNSS positioning method has poor sensitivity, is difficult to process signals in the environment with weak signals, such as forest sheltering, insufficient visible star number, weak signals and the like, has large positioning result error and even can not position in some places. In addition, the conventional GNSS positioning method needs a large number of satellites, at least four satellites, and the situation that information of the four satellites cannot be received in an environment with weak signals due to poor sensitivity can also cause a problem that a positioning result has a large error and even some places cannot be positioned.
Disclosure of Invention
The method aims to solve the problems that the traditional GNSS positioning method is poor in sensitivity, difficult in signal processing, large in positioning result error and even incapable of positioning in some places in the scenes of forest sheltering, insufficient in visible star number, weak signals and the like. The invention discloses a high-precision high-sensitivity single-satellite GNSS positioning method based on a passive synthetic aperture, which aims to: the high-precision high-sensitivity single satellite based on the passive synthetic aperture realizes the GNSS positioning of the target, and can still realize the high-sensitivity and high-precision positioning of the target under the scenes of forest shielding, insufficient number of visible satellites, weak signals and the like.
The purpose of the invention is realized by the following technical scheme:
the invention discloses a high-precision high-sensitivity single-satellite GNSS positioning method based on a passive synthetic aperture, which comprises the steps of establishing a GNSS positioning model based on the passive synthetic aperture by continuously receiving signals transmitted by a single navigation satellite in a small squint angle scene, and performing carrier removal processing on the received signals based on the GNSS positioning model of the passive synthetic aperture to obtain zero intermediate frequency signals after carrier removal; carrying out segmentation interception on the zero intermediate frequency signal after the carrier wave to obtain a two-dimensional frequency modulation signal matrix subjected to segmentation interception; performing square spectrum, normalization and mean value removal on each line of the two-dimensional frequency modulation signal matrix to obtain a two-dimensional frequency modulation signal square spectrum matrix again; extracting column signals corresponding to zero frequency of a two-dimensional frequency modulation signal square spectrum matrix and a locally generated matched filter for matched filtering; collecting matched filtering results under different modulation frequencies, recording correlation values corresponding to the different modulation frequencies and different time delays, and generating a two-dimensional search matrix of the modulation frequencies and the azimuth time; obtaining the radial distance between a receiver and a navigation satellite through a two-dimensional search matrix, and deducing satellite position information at the transmitting time by combining satellite ephemeris; and deducing the position information of the receiver by combining the radial distance and the geographical position information, namely realizing the GNSS positioning of the target based on the high-precision high-sensitivity single satellite of the passive synthetic aperture.
The purpose of the invention is realized by the following technical scheme:
the invention discloses a high-precision high-sensitivity single-satellite GNSS positioning method based on a passive synthetic aperture, which comprises the following steps:
step one, in a small oblique angle scene, continuously receiving signals transmitted by a single navigation satellite, establishing a GNSS positioning model based on a passive synthetic aperture, and performing carrier removal processing on the received signals based on the GNSS positioning model of the passive synthetic aperture to obtain zero intermediate frequency signals after carrier removal.
Step 1.1: under the small oblique angle scene, the oblique distance between the navigation satellite and the receiver is R, and the radial distance between the navigation satellite and the receiver is R0Establishing said pitch R and radial distance R0The relationship (2) of (c).
Under the small oblique angle scene, the oblique distance between the navigation satellite and the receiver is R, and the radial distance between the navigation satellite and the receiver is R0Establishing said pitch R and radial distance R0The relationship of (a) is shown in formula (1),
Figure BDA0002550079880000021
wherein: the navigation satellite velocity is v, and the azimuth time at zero Doppler time is tp。
Step 1.2: the slant distance R and the radial distance R established based on step 1.1 are R0And establishing a GNSS positioning model based on the passive synthetic aperture.
The slant distance R and the radial distance R established based on step 1.1 are R0Establishing a received signal r of a GNSS positioning based on a passive synthetic aperture0The model of (t) is shown in equation (2),
Figure BDA0002550079880000022
wherein: omega0For transmitting signal carrier, K is received signal amplitude, C (t) is signal chip, D (t) is navigation message, c is light speed, and theta is initial phase of transmitting signal.
Step 1.3: the received signal in step 1.2 is processed by carrier removal to obtain a zero intermediate frequency signal r (t) after carrier removal as shown in formula (3),
Figure BDA0002550079880000023
wherein: omega1Is the residual frequency offset after carrier removal.
And step two, carrying out segmentation interception on the zero intermediate frequency signal obtained in the step one to obtain a two-dimensional frequency modulation signal matrix of segmentation interception.
Carrying out sectional interception on the zero intermediate frequency signal obtained in the step one to obtain a two-dimensional frequency modulation signal matrix of sectional interception as shown in a formula (4),
Figure BDA0002550079880000024
wherein: omega1The initial frequency of the chirp signal, i.e., the residual frequency offset after the carrier of the radio frequency signal is removed, and Δ t is the sampling interval.
And step three, performing square spectrum, normalization and mean value removal on each row of the two-dimensional frequency modulation signal matrix in the step two to obtain a two-dimensional frequency modulation signal square spectrum matrix again.
And step four, extracting column signals corresponding to the zero frequency of the two-dimensional frequency modulation signal square spectrum matrix in the step three, wherein the column signals present a linear frequency modulation characteristic, and determining the frequency modulation frequency of the linear frequency modulation signal according to the linear frequency modulation characteristic.
Extracting column signal r 'corresponding to zero frequency of two-dimensional frequency modulation signal square spectrum matrix in step three is shown in formula (5), wherein Doppler frequency of r' showsLinear frequency modulation characteristic with frequency modulation rate of 2k ═ ω0v2/cR0。
Figure BDA0002550079880000031
And fifthly, locally generating a matched filter, performing matched filtering on the matched filter and the received Doppler signal, collecting matched filtering results under different modulation frequencies, recording correlation values corresponding to the different modulation frequencies and different time delays, and generating a two-dimensional search matrix of the modulation frequency-azimuth time.
The structure of the locally generated matched filter is shown in formula (6), the matched filter performs matched filtering with the received Doppler signal r', matched filtering results under different modulation frequencies are collected, correlation values corresponding to different modulation frequencies mu and different time delays t are recorded, and a two-dimensional search matrix of modulation frequency-azimuth direction time is generated.
Figure BDA0002550079880000032
Where mu is the frequency modulation of the matched filter, TSIs the synthetic pore size time. Wherein μ has a value range of
Figure BDA0002550079880000033
Wherein R is0Has a value range of
Figure BDA0002550079880000034
According to positioning error Δ R0Determining a search step Δ μ ═ c μ2/ωv2ΔR0When mu is equal to ω0v2/cR0Can be accurately matched with the Doppler signal. And sequentially bringing the estimated values of mu into a matched filter to generate a plurality of groups of filters, performing matched filtering with the received Doppler signal r', collecting matched filtering results under different modulation frequencies mu, recording correlation values corresponding to different modulation frequencies mu and different time delays t, and generating a modulation frequency-azimuth time two-dimensional search matrix M as shown in a formula (7).
Figure BDA0002550079880000035
And sixthly, the frequency modulation rate of the matched filter corresponding to the maximum correlation value in the two-dimensional search matrix obtained in the step five is the frequency modulation rate of the Doppler signal, and the time delay position where the maximum correlation value appears is the downward direction time of the zero Doppler plane. The carrier wave of the navigation satellite reflected signal, the speed of the navigation satellite and the speed of light are known, and the radial distance between the receiver and the navigation satellite is obtained by solving the demodulation frequency.
The frequency modulation rate of the matched filter corresponding to the maximum correlation value in the two-dimensional search matrix obtained in the step five is the frequency modulation rate omega of the Doppler signal0v2/cR0The time delay position where the maximum correlation value appears is the azimuth time t under the zero Doppler surfacep. Navigation satellite reflected signal carrier omega0The speed v and the light speed c of the navigation satellite are known, and the radial distance R between the receiver and the navigation satellite is obtained by solving the frequency modulation rate0。
And seventhly, deducing satellite transmitting time represented by the code phase and satellite position information at the transmitting time by combining the code phase of the signal corresponding to the zero Doppler face lower azimuth time obtained in the sixth step and the satellite ephemeris in the received navigation signal.
Step eight, the real distance R between the receiver and the navigation satellite at the moment of zero Doppler surface obtained in step six0Combining the geographical position information of the satellite at zero Doppler time obtained in the seventh step with the real distance R0And the position information of the receiver is deduced, namely the GNSS positioning of the target is realized by the high-precision high-sensitivity single satellite based on the passive synthetic aperture.
Has the advantages that:
the invention discloses a high-precision high-sensitivity single satellite target-based GNSS positioning method based on passive synthetic aperture, which comprises the steps of continuously receiving signals transmitted by a single navigation satellite, establishing a GNSS positioning model capable of accumulating long-time phases of the signals for the first time, namely, utilizing an omnidirectional antenna to accumulate the long-time phases of the navigation signals in the satellite overhead process, synthesizing a receiving antenna virtual aperture with the diameter being several kilometers, measuring the azimuth position perpendicular to the satellite motion track and the distance position in the azimuth direction by changing the positioning principle from the traditional four-satellite ranging positioning at the zero Doppler moment, and realizing the GNSS positioning under the condition of insufficient visible satellites. The method can improve the positioning performance under the noise condition. The noise comprises noise under the scenes of forest shielding, insufficient visible star number, weak signals and the like.
Drawings
FIG. 1 is a system block diagram of a high-precision high-sensitivity single-satellite GNSS positioning method based on a passive synthetic aperture according to the present invention
FIG. 2 is a simplified geometric model of a single-satellite GNSS positioning system based on synthetic aperture technology
FIG. 3 is a diagram of the position relationship between the receiver and the navigation satellite
FIG. 4 is a schematic diagram of receiver position under ECEF coordinate system
FIG. 5 is a geometric diagram of a satellite and a receiver in an xyz coordinate system
FIG. 6 is a two-dimensional search result of a matched filter
Detailed Description
For a better understanding of the objects and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
To verify the feasibility of the method, a GPS satellite is selected as the navigation satellite, the frequency f of the GPS signal emitted by the navigation satellite01575.42MHz, BPSK as modulation mode, 1MHz as signal sampling rate, 19751.44647km as orbit height h of satellite at zero Doppler time obtained by satellite ephemeris, 26122.44647km as orbit radius R as view center slope distance019797km, an equivalent satellite-borne receiver velocity v of 3.873km/s, a synthetic aperture time T of 6s, and a radiation source orientation time position TPAnd the position coordinate of the satellite in the ECEF coordinate system is (-13570902.341035,8402284.753703,20678840.152951) at T/2.
As shown in fig. 1, the high-precision high-sensitivity single-satellite GNSS positioning method based on the passive synthetic aperture disclosed in this embodiment includes the following specific steps:
step one, in a small oblique angle scene, continuously receiving signals transmitted by a single navigation satellite, establishing a GNSS positioning model based on a passive synthetic aperture, and performing carrier removal processing on the received signals based on the GNSS positioning model of the passive synthetic aperture to obtain zero intermediate frequency signals after carrier removal.
Step 1.1: under the small oblique angle scene, the oblique distance between the navigation satellite and the receiver is R, and the radial distance between the navigation satellite and the receiver is R0Establishing said pitch R and radial distance R0The relationship (2) of (c).
Under the small oblique angle scene, the oblique distance between the navigation satellite and the receiver is R, and the radial distance between the navigation satellite and the receiver is R0Establishing said pitch R and radial distance R0The relationship of (a) is shown in formula (1),
Figure BDA0002550079880000051
wherein: the navigation satellite velocity is v, and the azimuth time at zero Doppler time is tp。
Step 1.2: the slant distance R and the radial distance R established based on step 1.1 are R0And establishing a GNSS positioning model based on the passive synthetic aperture.
The navigation signal s (t) transmitted on the satellite is,
s(t)＝C(t)D(t)exp(ω0t+θ) (2)
wherein, the transmitting signal adopts C/A coding, BPSK modulation, omega0For transmitting signal carrier, C (t) is signal chip, D (t) is navigation message, theta is initial phase of transmitting signal
The slant distance R and the radial distance R established based on step 1.1 are R0And the navigation signals S (t) emitted on the satellites, establishing a received signal r of the GNSS positioning based on the passive synthetic aperture0The model of (t) is shown in formula (3),
Figure BDA0002550079880000052
step 1.3: the received signal in step 1.2 is processed by carrier removal to obtain a zero intermediate frequency signal r (t) after carrier removal as shown in formula (4),
Figure BDA0002550079880000053
wherein: omega1Is the residual frequency offset after carrier removal.
And step two, carrying out segmentation interception on the zero intermediate frequency signal obtained in the step one to obtain a two-dimensional frequency modulation signal matrix of segmentation interception.
Figure BDA0002550079880000061
In the formula: omega1In this example, each group is changed into a two-dimensional matrix of 12000 × 500 according to a window function designed in an actual scene, and the distance is 500 points, and the direction is 12000 points.
Thirdly, performing square spectrum, normalization and mean value removal on each row of the two-dimensional frequency modulation signal matrix in the second step to obtain a two-dimensional frequency modulation signal square spectrum matrix again;
and then extracting column signals corresponding to the zero frequency of the square spectrum matrix, wherein the sampling rate is 2000Hz, and estimating Doppler parameters in the received signals by using a method of locally generating matched filter matched filtering. In the example, the frequency modulation rate of the received signal is determined to be 20-30 according to the prior information, and the step is 0.025. The actual tuning frequency is 25 and the initial frequency is 150. And performing matched filtering on the baseband signals to obtain correlation values of the two signals, and finally obtaining the maximum correlation value under the correct down-conversion frequency, namely the corresponding frequency modulation rate. The search case for a matched filter is shown in fig. 6. Wherein, the x axis represents the searching range of the frequency modulation, namely the parameter K corresponding to the matched filter, the y axis represents the time, wherein, the time corresponding to the peak value is the azimuth time tp. It can be found that the highest point gets the corresponding actual fm and initial frequency at x-25 and y-3, respectivelyBy formula, R is obtainedo＝19797.481km,tp3 s. Actual view center slope distance R019797km, the radiation source is oriented at a time position tpIt was 0.3 s.
Step four, extracting a column signal r 'corresponding to the zero frequency of the two-dimensional frequency modulation signal square spectrum matrix in the step three, wherein the sampling rate of the signal is 2000Hz, the Doppler frequency of the r' shows a linear frequency modulation characteristic, and the frequency modulation rate is 2 k-omega0v2/cR0。
Figure BDA0002550079880000062
And fifthly, locally generating a matched filter structure as shown in a formula (), performing matched filtering on the matched filter and the received Doppler signal r', collecting matched filtering results under different modulation frequencies, recording correlation values corresponding to different modulation frequencies mu and different time delays t, and generating a two-dimensional search matrix of modulation frequency-azimuth direction time.
Figure BDA0002550079880000063
Where mu is the frequency modulation of the matched filter, TSIs the synthetic pore size time. Wherein μ has a value range of
Figure BDA0002550079880000064
Wherein R is0Has a value range of
Figure BDA0002550079880000065
According to positioning error Δ R0Determining a search step Δ μ ═ c μ2/ωv2ΔR0When mu is equal to ω0v2/cR0Can be accurately matched with the Doppler signal. In the example, the frequency modulation rate of the received signal is determined to be 20-30 according to the prior information, and the step is 0.025. The actual tuning frequency is 25 and the initial frequency is 150. Sequentially bringing the estimated value of mu into a matched filter to generate a plurality of groups of filters, performing matched filtering with the received Doppler signal r' and collecting different tonesAnd recording correlation values corresponding to different modulation frequencies mu and different time delays t according to the matched filtering result under the frequency mu, and generating a two-dimensional search matrix M of modulation frequency-azimuth time.
Figure BDA0002550079880000071
Step six and step five, the modulation frequency of the matched filter corresponding to the maximum correlation value in the frequency modulation frequency-azimuth time two-dimensional search matrix is a-omega0v2/cR0Navigation satellite transmit signal carrier omega0The speed v and the light speed c of the navigation satellite are known, and the radial distance R between the receiver and the navigation satellite is obtained by solving the frequency modulation rate0。
Figure BDA0002550079880000072
The search for a matched filter in this example is shown in figure 6. Wherein, the x axis represents the searching range of the frequency modulation, namely the parameter K corresponding to the matched filter, the y axis represents the time, wherein, the time corresponding to the peak value is the azimuth time tp. It can be found that the highest point obtains the corresponding actual frequency modulation rate and initial frequency at x-25 and y-3, and then R is obtained by the formulao＝19797.481km,tp3 s. Actual view center slope distance R019797km, the radiation source is oriented at a time position tpIt was 0.3 s.
Step seven, obtaining the time t of the lower direction of the zero Doppler surface through the step sixpThe code phase of the corresponding signal is combined with the satellite ephemeris in the received navigation signal to deduce the satellite transmission time t 'characterized by the code phase'pAnd, and at t'pPosition coordinates (X) of navigation satellite in ECEF coordinate system at momentk,Yk,Zk)
Step eight, the real distance R between the receiver and the navigation satellite at the moment of zero Doppler surface obtained in step six0Combining the geographical position information of the satellite at zero Doppler time obtained in the seventh step with the real distanceFrom R0And the position information of the receiver is deduced, namely the GNSS positioning of the target is realized by the high-precision high-sensitivity single satellite based on the passive synthetic aperture.
At t'pPosition coordinates (X) of navigation satellite in ECEF coordinate system at momentk,Yk,Zk) At this time, the distance relationship between the receiver and the navigation satellite is t'pThe navigation satellite is positioned at the nearest distance (namely zero Doppler plane time) to the receiver along the flight track direction of the satellite at the moment, and the nearest distance is R0Knowing the flight trajectory of the satellite, the coordinate position (x, y, z) of the receiver in the ECEF coordinate is finally obtained as shown in fig. 4, and the specific conversion process is as follows.
Because the time of the synthetic aperture is shorter, the navigation satellite can be positioned at tpThe motion at the moment is similar to the motion on a circle, the radius of the circle is the orbit radius of the point at the moment, the orbit radius can be obtained as R through a navigation message, and the earth is similar to the orbit radius of ReThe sphere of (2) sets up a rectangular coordinate system x ' y ' z ' on the plane of the orbit which runs by the navigation satellite as the x ' Oy ' plane, and obtains a geometric relation graph of the navigation satellite and the receiver as shown in fig. 5, the included angle between the connecting line of the navigation satellite and the center of the orbit and the x axis is α, and the included angle between the connecting line of the receiver and the center of the orbit and the z axis is α
Figure BDA0002550079880000073
The center of the orbit is the earth center, so that the position coordinate (X ') of the navigation satellite in the X ' y ' z ' coordinate system can be obtained 'k,Y′k,Z′k) And the coordinate position (x ', y', z ') of the receiver in the x' y 'z' coordinate system
Figure BDA0002550079880000081
And the distance between the navigation satellite and the receiver is R0Then the formula can be obtained
Figure BDA0002550079880000087
Finally, α expression sum can be obtained
Figure BDA0002550079880000082
Has a value of
Figure BDA0002550079880000083
An xOy plane of an xyz coordinate system (ECEF coordinate system) is rotated by a gamma angle (corresponding to the rotation position between an orbit plane and a meridian) along a z axis, and then the yOy plane is rotated by a beta angle (corresponding to the orbit inclination angle of a GPS (global positioning system) 55 DEG) along the x axis to finally obtain a coordinate conversion relation between an x 'y' z 'coordinate system as follows, wherein the x' y 'z' coordinate system is a rectangular coordinate system established by taking the orbit plane of a navigation satellite as an x 'Oy' plane
x′＝x cosγ+y sinγ
y′＝-x sinγcosβ+y cosγcosβ+z sinβ (13)
z′＝x sinγsinβ-y cosγsinβ+z cosβ
The position coordinates (X) of the known navigation satellite in the ECEF coordinate systemk,Yk,Zk) The position coordinate (X ') of the navigation satellite in the X ' y ' z ' coordinate system can be obtained by formula (13) 'k,Y′k,Z′k) Substituting equation (12) to obtain α and
Figure BDA0002550079880000084
α and
Figure BDA0002550079880000085
substituting the formula (10) to obtain the coordinate position value (x ', y ', z ') of the receiver in the x ' y ' z ' coordinate system, and substituting the (x ', y ', z ') into the formula (13) to solve the equation to obtain the coordinate position value (x, y, z) of the receiver in the ECEF coordinate system.
Given the coordinates of the navigation satellite (-13570902.341035,8402284.753703,20678840.152951), the trajectory of the navigation satellite is, for example, γ 2.878709rad, and β is 55 °, the position of the navigation satellite in the x ' y ' z ' coordinate system can be obtained by equation (13)Coordinate (15291167.85,14313915.4,15610067.3), substituting equation (12) results in α ═ 43.1 ° and
Figure BDA0002550079880000088
value of α and
Figure BDA0002550079880000086
and substituting the formula (10) to obtain a coordinate position value (4626380.467,4329290.271,665950.8395) of the receiver under an x 'y' z 'coordinate system, and substituting the (x', y ', z') into the formula (13) to solve the equation to obtain a coordinate position value (-4971426.47, -665563.6037,3928322.454) of the receiver under an ECEF coordinate, namely, the GNSS positioning of the target is realized by the high-precision high-sensitivity single satellite based on the passive synthetic aperture.
The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (6)

1. A high-precision high-sensitivity single-satellite GNSS positioning method based on passive synthetic aperture is characterized in that: the method comprises the following steps:
firstly, in a small oblique angle scene, continuously receiving signals transmitted by a single navigation satellite, establishing a GNSS positioning model based on a passive synthetic aperture, and performing carrier removal processing on the received signals based on the GNSS positioning model of the passive synthetic aperture to obtain zero intermediate frequency signals after carrier removal;
step two, carrying out segmentation interception on the zero intermediate frequency signal obtained in the step one to obtain a two-dimensional frequency modulation signal matrix subjected to segmentation interception;
thirdly, performing square spectrum, normalization and mean value removal on each row of the two-dimensional frequency modulation signal matrix in the second step to obtain a two-dimensional frequency modulation signal square spectrum matrix again;
extracting column signals corresponding to the zero frequency of the two-dimensional frequency modulation signal square spectrum matrix in the step three, wherein the column signals have a linear frequency modulation characteristic, and determining the frequency modulation frequency of the linear frequency modulation signal according to the linear frequency modulation characteristic;
step five, locally generating a matched filter, performing matched filtering on the matched filter and the received Doppler signal, collecting matched filtering results under different modulation frequencies, recording correlation values corresponding to the different modulation frequencies and different time delays, and generating a two-dimensional search matrix of modulation frequency-azimuth time;
step six, the frequency modulation rate of the matched filter corresponding to the maximum correlation value in the two-dimensional search matrix obtained in the step five is the frequency modulation rate of the Doppler signal, and the time delay position where the maximum correlation value appears is the lower azimuth time of the zero Doppler plane; the navigation satellite reflected signal carrier, the navigation satellite speed and the light speed are known, and the radial distance between the receiver and the navigation satellite is obtained by solving the demodulation frequency;
step seven, deducing satellite transmitting time represented by the code phase and satellite position information at the transmitting time by combining the code phase of the signal corresponding to the azimuth time under the zero Doppler plane obtained in the step six and the satellite ephemeris in the received navigation signal;
and step eight, the real distance between the receiver and the navigation satellite at the moment of zero Doppler time obtained in the step six, and the geographical position information of the satellite at the moment of zero Doppler time obtained in the step seven, wherein the position information of the receiver is deduced by combining the real distance and the geographical position information, namely the GNSS positioning of the target is realized by the high-precision high-sensitivity single satellite based on the passive synthetic aperture.
2. The passive synthetic aperture-based high-precision high-sensitivity single-satellite GNSS positioning method of claim 1, wherein: the first implementation method comprises the following steps of,
step 1.1: under the small oblique angle scene, the oblique distance between the navigation satellite and the receiver is R, and the radial distance between the navigation satellite and the receiver is R0Establishing said pitch R and radial distance R0The relationship of (1);
scene at small squint angleThe slant distance between the navigation satellite and the receiver is R, and the radial distance between the navigation satellite and the receiver is R0Establishing said pitch R and radial distance R0The relationship of (a) is shown in formula (1),
Figure FDA0002550079870000011
wherein: the navigation satellite velocity is v, and the azimuth time at zero Doppler time is tp；
Step 1.2: the slant distance R and the radial distance R established based on step 1.1 are R0Establishing a GNSS positioning model based on the passive synthetic aperture;
the slant distance R and the radial distance R established based on step 1.1 are R0Establishing a received signal r of a GNSS positioning based on a passive synthetic aperture0The model of (t) is shown in equation (2),
Figure FDA0002550079870000021
wherein: omega0Is a transmitting signal carrier wave, K is a receiving signal amplitude, C (t) is a signal code sheet, D (t) is a navigation message, c is a light velocity, and theta is an initial phase of a transmitting signal;
step 1.3: the received signal in step 1.2 is processed by carrier removal to obtain a zero intermediate frequency signal r (t) after carrier removal as shown in formula (3),
Figure FDA0002550079870000022
wherein: omega1Is the residual frequency offset after carrier removal.
3. The passive synthetic aperture-based high-precision high-sensitivity single-satellite GNSS positioning method of claim 2, wherein: the second step is realized by the method that,
carrying out sectional interception on the zero intermediate frequency signal obtained in the step one to obtain a two-dimensional frequency modulation signal matrix of sectional interception as shown in a formula (4),
Figure FDA0002550079870000023
wherein: omega1The initial frequency of the chirp signal, i.e., the residual frequency offset after the carrier of the radio frequency signal is removed, and Δ t is the sampling interval.
4. The passive synthetic aperture-based high-precision high-sensitivity single-satellite GNSS positioning method of claim 3, wherein: the implementation method of the fourth step is that,
extracting column signals r 'corresponding to the two-dimensional frequency modulation signal square spectrum matrix zero frequency in the step three as shown in formula (5), wherein the Doppler frequency of r' shows linear frequency modulation characteristic, and the frequency modulation rate is 2 k-omega0v2/cR0；
Figure FDA0002550079870000024
。
5. The method according to claim 4, wherein the method comprises the following steps: the fifth step is to realize that the method is that,
the structure of the locally generated matched filter is shown in a formula (6), the matched filter and the received Doppler signal r' are subjected to matched filtering, matched filtering results under different modulation frequencies are collected, correlation values corresponding to different modulation frequencies mu and different time delays t are recorded, and a two-dimensional search matrix of modulation frequency-azimuth direction time is generated;
m(t)＝rect(t)exp(iμt2),
Figure FDA0002550079870000031
where mu is the frequency modulation of the matched filter, TSIs the synthetic aperture time; wherein μ has a value range of
Figure FDA0002550079870000032
Wherein R is0Has a value range of
Figure FDA0002550079870000033
According to positioning error Δ R0Determining a search step Δ μ ═ c μ2/ωv2ΔR0When mu is equal to ω0v2/cR0The time can be accurately matched with the Doppler signal; sequentially bringing the estimated values of mu into a matched filter to generate a plurality of groups of filters, performing matched filtering with the received Doppler signal r', collecting matched filtering results under different modulation frequencies mu, recording correlation values corresponding to different modulation frequencies mu and different time delays t, and generating a modulation frequency-azimuth time two-dimensional search matrix M as shown in a formula (7);
Figure FDA0002550079870000034
。
6. the passive synthetic aperture-based high-precision high-sensitivity single-satellite GNSS positioning method of claim 5, wherein: the sixth realization method comprises the following steps of,
the frequency modulation rate of the matched filter corresponding to the maximum correlation value in the two-dimensional search matrix obtained in the step five is the frequency modulation rate omega of the Doppler signal0v2/cR0The time delay position where the maximum correlation value appears is the azimuth time t under the zero Doppler surfacep(ii) a Navigation satellite reflected signal carrier omega0The speed v and the light speed c of the navigation satellite are known, and the radial distance R between the receiver and the navigation satellite is obtained by solving the frequency modulation rate0。
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