Dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signal

Abstract

The invention discloses a dual-mode direct position estimation receiver positioning method based on a GPS L1 / BDS B1C signal. The method comprises the following steps: predicting a priori value of a state quantity of a current epoch dual-mode DPE receiver; decomposing the priori value into a position-clock difference domain priori value and a speed-clock drift domain priori value; generating a five-dimensional position-clock difference domain grid space and a five-dimensional speed-clock drift domain grid space; calculating a correlation function and a Doppler spectrum of each visible satellite in the current epoch receiving data; calculating joint accumulation of a position-clock difference domain grid space and a speed-clock drift domain grid space; forming a state quantity observation value of the current epoch; and obtaining a navigation solution of the current epoch dual-mode DPE receiver. The method has the advantages that satellite signals of two constellations of GPS and BDS (Beidou navigation satellite system) are combined, more visible satellites are provided for navigation solution, and compared with a single-mode DPE receiver, the positioning performance under the environments of serious signal attenuation, multipath and non-line-of-sight transmission and the like is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite navigation receivers, and in particular relates to a dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals. Background Art

[0002] As the application field of the Global Navigation Satellite System (GNSS) gradually expands, its application environment is becoming increasingly complex, which makes traditional GNSS receivers face more challenges. With the development of smart devices and autonomous driving technology, high-performance and reliable navigation in urban environments has become a hot topic in the GNSS field in recent years. In response to the problem that traditional GNSS scalar receivers have poor performance or even cannot work properly in complex environments, the idea of ​​integrating various algorithms on the basis of traditional scalar receivers to improve their robustness has been widely carried out. In addition, from the perspective of receiver positioning methods, more robust new receiver structures have been proposed, such as vector receivers and direct position estimation (DPE) receivers. The core idea is to improve the working performance in complex environments through mutual assistance between visible satellite signals. Vector receivers control all tracking loops through navigation solution feedback, and still retain the tracking loop, while DPE receivers obtain navigation solutions by directly accumulating all visible satellite signals in the navigation domain, realizing mutual assistance between signals at a deeper level.

[0003] There have been a lot of research results on improving the performance of DPE receivers, such as the joint global positioning system (GPS) and visual DPE, which estimates the receiver position directly from the visual features extracted from the original GPS L1 signal and the original camera image; according to the different satellite signal quality, different weighting models are used to reduce the impact of low-quality satellite signals on the joint accumulation output, thereby improving the performance of DPE in complex environments. Although DPE receivers have certain performance advantages over traditional receivers, in complex urban environments, when faced with severe signal attenuation, multipath and non-line-of-sight transmission phenomena, the performance of DPE receivers will still be seriously affected. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals, which receiver can still have good navigation performance when facing severe signal attenuation, multipath and non-line-of-sight transmission phenomena.

[0005] In order to achieve the above object, the dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signal provided by the present invention comprises the following steps performed in sequence:

[0006] 1) Establish the state transfer equation of the dual-mode DPE receiver based on GPS L1 / BDS B1C signal, and use the above state transfer equation and the navigation solution of the previous epoch to predict the prior value of the dual-mode DPE receiver state quantity in the current epoch;

[0007] 2) Decomposing the prior value of the dual-mode DPE receiver state quantity of the current epoch into two parts: a prior value in the position-clock error domain and a prior value in the velocity-clock drift domain;

[0008] 3) Generate a five-dimensional position-clock error domain grid space and a five-dimensional velocity-clock drift domain grid space with the above-mentioned position-clock error domain prior value and velocity-clock drift domain prior value as the center respectively;

[0009] 4) Use fast Fourier transform to calculate the correlation function and Doppler spectrum of each visible satellite in the received data of the current epoch;

[0010] 5) using a table lookup method to calculate the joint accumulation of the position-clock error domain grid space and the velocity-clock drift domain grid space obtained in step 3) from the correlation function and Doppler spectrum of the above-mentioned visible satellite signals;

[0011] 6) The maximum value of the joint accumulation of the above position-clock error domain grid space is taken as the observation value of the position-clock error of the current epoch, and the maximum value of the joint accumulation of the velocity-clock drift domain grid space is taken as the observation value of the velocity-clock drift of the current epoch, and the observation values ​​of the position-clock error and velocity-clock drift constitute the state quantity observation value of the current epoch;

[0012] 7) The state quantity observation value of the current epoch obtained in step 6) is sent to the Kalman filter to obtain the navigation solution of the dual-mode DPE receiver of the current epoch.

[0013] In step 1), the state transfer equation of the dual-mode DPE receiver based on the GPS L1 / BDS B1C signal is established, and the method of predicting the prior value of the state quantity of the dual-mode DPE receiver in the current epoch by using the state transfer equation and the navigation solution of the previous epoch is:

[0014] First, the state quantity of the dual-mode DPE receiver is defined as Where p = (x, y, z) T represents the three-dimensional position of the dual-mode DPE receiver, represents the three-dimensional velocity of the dual-mode DPE receiver, δt g and δt bRespectively represent the clock errors of dual-mode DPE receivers under GPS and BDS systems, and They represent the clock drift of the dual-mode DPE receiver under GPS and BDS systems respectively;

[0015] Then, the state transfer equation of the dual-mode DPE receiver based on GPS L1 / BDS B1C signal is established:

[0016]

[0017] Wherein, the subscript k represents the epoch index; the superscripts “-” and “+” represent the prior estimate and the posterior estimate, respectively; represents the navigation solution of the previous epoch; F represents the one-step state transfer matrix. In low-dynamic applications, it is assumed that the receiver moves at a constant speed. In this case, the one-step state transfer matrix F is expressed as:

[0018]

[0019] Among them, Δt represents the time interval from the k-1th epoch to the kth epoch, and I represents the unit matrix; according to the navigation solution of the previous epoch The state transfer equation shown in formula (1) is used to obtain the prior value of the state quantity of the dual-mode DPE receiver in the current epoch: And the symbol Abbreviated as x - .

[0020] In step 2), the method of decomposing the a priori value of the current epoch dual-mode DPE receiver state quantity into two parts: a position-clock difference domain a priori value and a velocity-clock drift domain a priori value is:

[0021] The prior value of the dual-mode DPE receiver state quantity of the current epoch It is decomposed into the position-clock error domain prior value and the velocity-clock drift domain prior value, where the position-clock error domain prior value is expressed as The speed-clock drift domain prior is expressed as

[0022] In step 3), the method of generating a five-dimensional position-clock error domain grid space and a five-dimensional velocity-clock drift domain grid space with the above-mentioned position-clock error domain prior value and velocity-clock drift domain prior value as the center is:

[0023] Prior value in position-clock difference domain and speed-clock drift domain prior As the center, generate the five-dimensional position-clock error domain grid space and the five-dimensional velocity-clock drift domain grid space, and record the states corresponding to each position-clock error domain grid point and each velocity-clock drift domain grid point as and Where L represents the total number of grid points.

[0024] In step 4), the method of using fast Fourier transform to respectively calculate the correlation function and Doppler spectrum of each visible satellite in the received data of the current epoch is:

[0025] First, the signal obtained by down-converting the GPS L1 and BDS B1C signals received by the dual-mode DPE receiver antenna is expressed as:

[0026]

[0027] Wherein, the superscript i represents the physical quantity corresponding to the i-th visible satellite; the subscripts g and b represent the physical quantities corresponding to the visible satellites of GPS L1 and BDS B1C, respectively; M and N represent the number of visible satellites of GPS L1 and BDS B1C, respectively; n(t) represents additive white noise, which is assumed to obey Gaussian distribution; Represents the GPS L1 signal, the formula is:

[0028]

[0029] Among them, a i Indicates the amplitude of visible satellite signals; C i (t-τ i ) represents the pseudo-random code of the visible satellite signal; τ i Indicates the code delay of the visible satellite signal; Indicates the Doppler frequency of visible satellite signals; It represents the BDS B1C signal, which is composed of a data component and a pilot component. The energy ratio of the data component and the pilot component is 1:3. Therefore, the BDS B1C signal is represented as:

[0030]

[0031] in, and The BDS B1C signal is divided into a BOC (1,1) narrowband part and a BOC (6,1) wideband part, where f sc_a =1.023MHz and f sc_b =6.138MHz represents the subcarrier frequencies of the narrowband part and the broadband part respectively;

[0032] Then, the correlation function and Doppler spectrum of each visible satellite of GPS L1 and BDS B1C in the received data of the current epoch are calculated by fast Fourier transform respectively; first, the correlation function of each visible satellite signal of GPS L1 and BDS B1C is calculated by fast Fourier transform, and the correlation function of GPS L1 signal is calculated by fast Fourier transform. Correlation function with BDS B1C signal Respectively expressed as:

[0033]

[0034] Where F represents FFT operation; (·) * represents the conjugate operation; (·) -1 represents the inverse operation; represents the Doppler frequency corresponding to the prior value of the dual-mode DPE receiver state; sc(t) represents the subcarrier of the BDS B1C signal; R g (·) represents the autocorrelation function of GPSL1 signal:

[0035]

[0036] R data / pilot (·) represents the autocorrelation function of the BDS B1C signal:

[0037]

[0038] Then use fast Fourier transform to calculate the Doppler spectrum of each visible satellite signal of GPS L1 and BDS B1C. The Doppler spectrum of GPS L1 signal And the Doppler spectrum of the BDS B1C signal Respectively expressed as:

[0039]

[0040]

[0041] Among them, τ i- The code delay is mapped from the prior state quantity representing the center of the position-clock domain grid; the Doppler spectrum of the GPS L1 signal and the BDS B1C signal is uniformly expressed as:

[0042]

[0043] Among them, T coh Indicates the integration time.

[0044] In step 5), the method of using a table lookup method to calculate the joint accumulation of the position-clock error domain grid space and the velocity-clock drift domain grid space obtained in step 3) from the correlation function and Doppler spectrum of the above-mentioned visible satellite signals is:

[0045] First, the joint accumulation of the position-clock error domain grid space is calculated using the table lookup method: the code delay of each visible satellite is calculated according to the receiver state quantity of the grid point in the position-clock error domain grid space:

[0046]

[0047] Where c represents the speed of light; p i Indicates the three-dimensional position of the visible satellite; δt i Indicates the clock error of the visible satellite;

[0048] Then, according to the calculated code delay of each visible satellite signal, the corresponding correlation function value is extracted from the correlation function of each visible satellite signal pre-calculated in step 4), which is the so-called "table lookup method"; finally, the correlation function values ​​of all visible satellite signals extracted at the grid point are accumulated to obtain the joint accumulation of the position-clock error domain grid point, and the joint accumulation of all the position-clock error domain grid points constitutes the joint accumulation of the position-clock error domain grid space;

[0049] Then use the table lookup method to calculate the joint accumulation of the velocity-clock drift domain grid space: first, calculate the corresponding Doppler frequency of each visible satellite based on the receiver state quantity of the grid point in the velocity-clock drift domain grid space:

[0050]

[0051] in, represents the three-dimensional velocity of the visible satellite; f c =1575.42MHz represents the carrier frequency of L1 band; represents the clock drift of the visible satellite; then, according to the calculated Doppler frequencies of the visible satellite signals, the corresponding Doppler frequency values ​​are extracted from the Doppler spectra of the visible satellite signals pre-calculated in step 4) using a table lookup method; finally, the Doppler frequency values ​​of all visible satellite signals extracted at the grid point are accumulated to obtain the joint accumulation of the speed-clock drift domain grid points, and the joint accumulation of all the speed-clock drift domain grid points constitutes the joint accumulation of the speed-clock drift domain grid space.

[0052] In step 6), the method of taking the joint accumulated maximum value of the position-clock error domain grid space as the observed value of the position-clock error of the current epoch, taking the joint accumulated maximum value of the velocity-clock drift domain grid space as the observed value of the velocity-clock drift of the current epoch, and forming the state quantity observed value of the current epoch by the observed values ​​of the position-clock error and the velocity-clock drift is:

[0053] The joint accumulation maximum value of the position-clock error domain grid space calculated in step 5) is taken as the observation value of the position-clock error of the current epoch, and the joint accumulation maximum value of the velocity-clock drift domain grid space calculated in step 5) is taken as the observation value of the velocity-clock drift of the current epoch, expressed as:

[0054]

[0055] The above-mentioned position-clock error and velocity-clock drift observation values ​​constitute the state quantity observation value of the current epoch.

[0056] The dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals provided by the present invention has the following advantages:

[0057] The combination of satellite signals from the GPS and BDS (Beidou Navigation Satellite System) constellations provides more visible satellites for navigation solutions. Compared with single-mode DPE receivers, it improves positioning performance in environments with severe signal attenuation, multipath and non-line-of-sight transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The invention provides a receiver positioning flow chart for dual-mode direct position estimation based on GPS L1 / BDS B1C signals.

[0059] Figure 2 This is the satellite geometric distribution of GPS and BDS within the experimental acquisition time of 0 to 36 seconds.

[0060] Figure 3 (a) shows the change of the carrier-to-noise ratio of all visible GPS satellites during the entire acquisition process of the experiment.

[0061] Figure 3 (b) shows the change of the carrier-to-noise ratio of all BDS visible satellites during the entire acquisition process of the experiment.

[0062] Figure 4 The geometric distribution of visible satellites of GPS and BDS is collected in the experimental period of 38s to 43s.

[0063] Figure 5 The geometric distribution of visible satellites of GPS and BDS is collected in the experimental period of 48s to 51s.

[0064] Figure 6 The geometric distribution of visible satellites of GPS and BDS is collected within the time range of 53s to 61s;

[0065] Figure 7 This paper compares the positioning errors of a single-mode DPE receiver based on GPS L1 satellite signal, a single-mode DPE receiver based on BDS B1C signal, a dual-mode scalar receiver based on GPS L1 and BDS B1C, and a dual-mode DPE receiver based on GPS L1 and BDS B1C within the signal acquisition time.

[0066] Figure 8This figure compares the cumulative distribution of three-dimensional positioning errors of a single-mode DPE receiver based on GPS L1 satellite signal, a single-mode DPE receiver based on BDSB1C signal, and a dual-mode DPE receiver based on GPS L1 and BDS B1C within the signal acquisition time. DETAILED DESCRIPTION

[0067] The dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals provided by the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0068] like Figure 1 As shown, the dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals provided by the present invention includes the following steps performed in sequence:

[0069] 1) Establish the state transfer equation of the dual-mode DPE (direct position estimation) receiver based on GPS L1 / BDS B1C signal, and use the above state transfer equation and the navigation solution of the previous epoch to predict the prior value of the dual-mode DPE receiver state quantity in the current epoch;

[0070] First, the state quantity of the dual-mode DPE receiver is defined as Where p = (x, y, z) T represents the three-dimensional position of the dual-mode DPE receiver, represents the three-dimensional velocity of the dual-mode DPE receiver, δt g and δt b Respectively represent the clock errors of dual-mode DPE receivers under GPS and BDS systems, and They represent the clock drift of the dual-mode DPE receiver under GPS and BDS systems respectively;

[0071] Then, the state transfer equation of the dual-mode DPE receiver based on GPS L1 / BDS B1C signal is established:

[0072]

[0073] Wherein, the subscript k represents the epoch index; the superscripts “-” and “+” represent the prior estimate and the posterior estimate, respectively; represents the navigation solution of the previous epoch; F represents the one-step state transfer matrix. In low-dynamic applications, it is generally assumed that the receiver moves at a constant speed. In this case, the one-step state transfer matrix F is expressed as:

[0074]

[0075] Among them, Δt represents the time interval from the k-1th epoch to the kth epoch, and I represents the unit matrix; according to the navigation solution of the previous epoch The state transfer equation shown in formula (1) is used to obtain the prior value of the state quantity of the dual-mode DPE receiver in the current epoch: And the symbol Abbreviated as x - .

[0076] 2) Decomposing the prior value of the dual-mode DPE receiver state quantity of the current epoch into two parts: a prior value in the position-clock error domain and a prior value in the velocity-clock drift domain;

[0077] The prior value of the dual-mode DPE receiver state quantity of the current epoch It is decomposed into the position-clock error domain prior value and the velocity-clock drift domain prior value, where the position-clock error domain prior value is expressed as The speed-clock drift domain prior is expressed as

[0078] 3) Generate a five-dimensional position-clock error domain grid space and a five-dimensional velocity-clock drift domain grid space with the above-mentioned position-clock error domain prior value and velocity-clock drift domain prior value as the center respectively;

[0079] Prior value in position-clock difference domain and speed-clock drift domain prior As the center, generate the five-dimensional position-clock error domain grid space and the five-dimensional velocity-clock drift domain grid space, and record the states corresponding to each position-clock error domain grid point and each velocity-clock drift domain grid point as and Where L represents the total number of grid points.

[0080] 4) Use Fast Fourier Transform (FFT) to calculate the correlation function and Doppler spectrum of each visible satellite in the received data of the current epoch;

[0081] First, the signal obtained by down-converting the GPS L1 and BDS B1C signals received by the dual-mode DPE receiver antenna is expressed as:

[0082]

[0083] Wherein, the superscript i represents the physical quantity corresponding to the i-th visible satellite; the subscripts g and b represent the physical quantities corresponding to the visible satellites of GPS L1 and BDS B1C, respectively; M and N represent the number of visible satellites of GPS L1 and BDS B1C, respectively; n(t) represents additive white noise, which is generally assumed to obey Gaussian distribution; Represents the GPS L1 signal, the formula is:

[0084]

[0085] Among them, a iIndicates the amplitude of visible satellite signals; C i (t-τ i ) represents the pseudo-random code of the visible satellite signal; τ i Indicates the code delay of the visible satellite signal; Indicates the Doppler frequency of visible satellite signals; It represents the BDS B1C signal, which is composed of a data component and a pilot component. The energy ratio of the data component and the pilot component is 1:3. Therefore, the BDS B1C signal is represented as:

[0086]

[0087] in, and The BDS B1C signal is divided into a BOC (1,1) narrowband part and a BOC (6,1) wideband part, where f sc_a =1.023MHz and f sc_b =6.138MHz represents the subcarrier frequencies of the narrowband part and the broadband part respectively;

[0088] Then, the correlation function and Doppler spectrum of each visible satellite of GPS L1 and BDS B1C in the received data of the current epoch are calculated by fast Fourier transform respectively; first, the correlation function of each visible satellite signal of GPS L1 and BDS B1C is calculated by fast Fourier transform, and the correlation function of GPS L1 signal is calculated by fast Fourier transform. Correlation function with BDS B1C signal Respectively expressed as:

[0089]

[0090] Where F represents FFT operation; (·) * represents the conjugate operation; (·) -1 represents the inverse operation; represents the Doppler frequency corresponding to the prior value of the dual-mode DPE receiver state; sc(t) represents the subcarrier of the BDS B1C signal; R g (·) represents the autocorrelation function of GPSL1 signal:

[0091]

[0092] R data / pilot (·) represents the autocorrelation function of the BDS B1C signal:

[0093]

[0094] Then use fast Fourier transform to calculate the Doppler spectrum of each visible satellite signal of GPS L1 and BDS B1C. The Doppler spectrum of GPS L1 signal And the Doppler spectrum of the BDS B1C signal Respectively expressed as:

[0095]

[0096] Among them, τ i- The code delay is mapped out by the prior state quantity representing the center of the position-clock difference domain grid. The Doppler spectrum of the GPS L1 signal and the BDS B1C signal can be uniformly expressed as:

[0097]

[0098] Among them, T coh Indicates the integration time.

[0099] 5) using a table lookup method to calculate the joint accumulation of the position-clock error domain grid space and the velocity-clock drift domain grid space obtained in step 3) from the correlation function and Doppler spectrum of the above-mentioned visible satellite signals;

[0100] First, the joint accumulation of the position-clock error domain grid space is calculated using the table lookup method: First, the code delay of each visible satellite is calculated according to the receiver state quantity of the grid point in the position-clock error domain grid space:

[0101]

[0102] Where c represents the speed of light; p i Indicates the three-dimensional position of the visible satellite; δt i Indicates the clock error of the visible satellite;

[0103] Then, according to the calculated code delay of each visible satellite signal, the corresponding correlation function value is extracted from the correlation function of each visible satellite signal pre-calculated in step 4), which is the so-called "table lookup method"; finally, the correlation function values ​​of all visible satellite signals extracted at the grid point are accumulated to obtain the joint accumulation of the position-clock error domain grid points, and the joint accumulation of all position-clock error domain grid points constitutes the joint accumulation of the position-clock error domain grid space.

[0104] Then use the table lookup method to calculate the joint accumulation of the velocity-clock drift domain grid space: Similar to the calculation of the joint accumulation of the position-clock error domain grid space, first calculate the corresponding Doppler frequency of each visible satellite based on the receiver state quantity of the grid point in the velocity-clock drift domain grid space:

[0105]

[0106] in, represents the three-dimensional velocity of the visible satellite; f c =1575.42MHz represents the carrier frequency of L1 band; represents the clock drift of the visible satellite; then, according to the calculated Doppler frequencies of the visible satellite signals, the corresponding Doppler frequency values ​​are extracted from the Doppler spectra of the visible satellite signals pre-calculated in step 4) using a table lookup method; finally, the Doppler frequency values ​​of all visible satellite signals extracted at the grid point are accumulated to obtain the joint accumulation of the speed-clock drift domain grid points, and the joint accumulation of all the speed-clock drift domain grid points constitutes the joint accumulation of the speed-clock drift domain grid space.

[0107] 6) The maximum value of the joint accumulation of the above position-clock error domain grid space is taken as the observation value of the position-clock error of the current epoch, and the maximum value of the joint accumulation of the velocity-clock drift domain grid space is taken as the observation value of the velocity-clock drift of the current epoch, and the observation values ​​of the position-clock error and velocity-clock drift constitute the state quantity observation value of the current epoch;

[0108] The joint accumulation maximum value of the position-clock error domain grid space calculated in step 5) is taken as the observation value of the position-clock error of the current epoch, and the joint accumulation maximum value of the velocity-clock drift domain grid space calculated in step 5) is taken as the observation value of the velocity-clock drift of the current epoch, expressed as:

[0109]

[0110] The above-mentioned position-clock error and velocity-clock drift observation values ​​constitute the state quantity observation value of the current epoch.

[0111] 7) The state quantity observation value of the current epoch obtained in step 6) is sent to the Kalman filter to obtain the navigation solution of the dual-mode DPE receiver of the current epoch.

[0112] The effects of the present invention can be further illustrated by the following experimental results.

[0113] Experimental acquisition system and scenario description: The data acquisition system includes BladeRF-XA4 RF front end, BT-300 antenna and laptop loaded with control software. The positioning results of u-blox EVK-M8T are used as reference. The data acquisition location of the experiment is near a flyover in a certain city. The acquisition date is May 29, 2024. The total data duration is 70s. The first 36s are in a relatively open environment. During this period, the acquisition system remains stationary. After 36s, the acquisition system moves at a uniform speed to an environment with building influence. The influence of buildings is relatively small during 38s-43s and 53s-61s, and the influence of buildings on satellite signals is relatively large during 48s-51s. The number of GPS satellites and BDS satellites in the signals collected by this experiment is greater than 4, so GPS and BDS single-mode systems can also be used for positioning. The signals collected in the experiment are processed using a single-mode DPE receiver based on GPS L1 satellite signals, a single-mode DPE receiver based on BDS B1C signals, a dual-mode scalar receiver based on GPS L1 and BDSB1C, and a dual-mode DPE receiver based on GPS L1 and BDS B1C, and the positioning errors of several receivers are compared.

[0114] Figure 2 The geometric distribution of visible satellites of GPS and BDS within the experimental acquisition time of 0 to 36 seconds;

[0115] Figure 3 This is the change of the carrier-to-noise ratio of all visible satellites during the entire acquisition process of the experiment;

[0116] in Figure 3 (a) and Figure 3 (b) shows the change of the carrier-to-noise ratio of the visible satellites of GPS and BDS respectively. It can be seen from the figure that after 36 seconds, the carrier-to-noise ratio of each visible satellite signal of GPS and BDS has different degrees of attenuation due to reasons such as building shielding.

[0117] Figure 4 The geometric distribution of visible satellites of GPS and BDS within 38s to 43s of experimental acquisition time;

[0118] Will Figure 4 and Figure 2 By comparison, it can be seen that the signals of the visible satellites G20, G23, G30 and B28, B50 cannot be received by the receiver during the period from 38s to 43s because they are blocked by buildings.

[0119] Figure 5 The geometric distribution of visible satellites of GPS and BDS within 48s to 51s of experimental acquisition time;

[0120] It can be seen from the figure that due to the severe obstruction of buildings during the period from 48s to 51s, only the signals of visible satellites G23, G24, G30 and B43, B50 were received by the receiver.

[0121] Figure 6 The geometric distribution of visible satellites of GPS and BDS in the experimental acquisition time of 53s to 61s;

[0122] Will Figure 6 and Figure 2 By comparison, it can be seen that the signals of the visible satellites G5, G20, G30 and B50 cannot be received by the receiver during the period from 53s to 61s because they are blocked by buildings.

[0123] Figure 7 This paper compares the positioning errors of a single-mode DPE receiver based on GPS L1 satellite signal, a single-mode DPE receiver based on BDSB1C signal, a dual-mode scalar receiver based on GPS L1 and BDS B1C, and a dual-mode DPE receiver based on GPS L1 and BDSB1C within the signal acquisition time.

[0124] from Figure 7 It can be seen from the figure that due to the influence of the buildings at the collection site, the three-dimensional positioning errors of the single-mode DPE receiver based on GPS L1 satellite signals, the single-mode DPE receiver based on BDS B1C signals, the dual-mode scalar receiver based on GPS L1 and BDS B1C, and the dual-mode DPE receiver based on GPS L1 and BDS B1C all fluctuated to varying degrees. The three-dimensional positioning errors of the single-mode DPE receiver based on GPS L1 and the single-mode DPE receiver based on BDS B1C increased significantly from 38s to 43s; the positioning error of the dual-mode scalar receiver based on GPS L1 and BDS B1C increased sharply from 48s to 51s, and ultimately it was impossible to locate; the three-dimensional positioning error of the single-mode DPE receiver based on GPS L1 increased from 53s to 61s. At all times, the positioning error of the dual-mode DPE receiver based on GPS L1 and BDS B1C is smaller than that of the other three receivers, indicating that when the satellite signal is weak due to building obstruction, the dual-mode DPE receiver based on GPS L1 and BDS B1C provided by the present invention still has good positioning performance.

[0125] Figure 8 This figure compares the cumulative distribution of three-dimensional positioning errors of a single-mode DPE receiver based on GPS L1 satellite signal, a single-mode DPE receiver based on BDSB1C signal, and a dual-mode DPE receiver based on GPS L1 and BDS B1C within the signal acquisition time.

[0126] from Figure 8It can be seen that the dual-mode DPE receiver achieves a positioning accuracy better than 20m at a probability level of 80%, which proves the performance advantage of the dual-mode DPE receiver based on GPS L1 and BDS B1C provided by the present invention.

Claims

1. A dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals, characterized in that: The positioning method comprises the following steps performed in sequence: 1) Establish the state transfer equation of the dual-mode DPE receiver based on GPS L1 / BDS B1C signal, and use the above state transfer equation and the navigation solution of the previous epoch to predict the prior value of the dual-mode DPE receiver state quantity in the current epoch; 2) Decomposing the prior value of the dual-mode DPE receiver state quantity of the current epoch into two parts: a prior value in the position-clock error domain and a prior value in the velocity-clock drift domain; 3) Generate a five-dimensional position-clock error domain grid space and a five-dimensional velocity-clock drift domain grid space with the above-mentioned position-clock error domain prior value and velocity-clock drift domain prior value as the center respectively; 4) Use fast Fourier transform to calculate the correlation function and Doppler spectrum of each visible satellite in the received data of the current epoch; 5) using a table lookup method to calculate the joint accumulation of the position-clock error domain grid space and the velocity-clock drift domain grid space obtained in step 3) from the correlation function and Doppler spectrum of the above-mentioned visible satellite signals; 6) The maximum value of the joint accumulation of the above position-clock error domain grid space is taken as the observation value of the position-clock error of the current epoch, and the maximum value of the joint accumulation of the velocity-clock drift domain grid space is taken as the observation value of the velocity-clock drift of the current epoch, and the observation values ​​of the position-clock error and velocity-clock drift constitute the state quantity observation value of the current epoch; 7) The state quantity observation value of the current epoch obtained in step 6) is sent to the Kalman filter to obtain the navigation solution of the dual-mode DPE receiver of the current epoch.

2. The dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals according to claim 1 is characterized in that: In step 1), the state transfer equation of the dual-mode DPE receiver based on the GPS L1 / BDS B1C signal is established, and the method of predicting the prior value of the state quantity of the dual-mode DPE receiver in the current epoch by using the state transfer equation and the navigation solution of the previous epoch is: First, the state quantity of the dual-mode DPE receiver is defined as Where p = (x, y, z) T represents the three-dimensional position of the dual-mode DPE receiver, represents the three-dimensional velocity of the dual-mode DPE receiver, δt g and δt b Respectively represent the clock errors of dual-mode DPE receivers under GPS and BDS systems, and They represent the clock drift of the dual-mode DPE receiver under GPS and BDS systems respectively; Then, the state transfer equation of the dual-mode DPE receiver based on GPS L1 / BDS B1C signal is established: Wherein, the subscript k represents the epoch index; the superscripts "-" and "+" represent the prior estimate and the posterior estimate, respectively; represents the navigation solution of the previous epoch; F represents the one-step state transfer matrix. In low-dynamic applications, it is assumed that the receiver moves at a constant speed. In this case, the one-step state transfer matrix F is expressed as: Among them, Δt represents the time interval from the k-1th epoch to the kth epoch, and I represents the unit matrix; according to the navigation solution of the previous epoch The state transfer equation shown in formula (1) is used to obtain the prior value of the state quantity of the dual-mode DPE receiver in the current epoch: And the symbol Abbreviated as 3. The dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals according to claim 1 is characterized in that: In step 2), the method of decomposing the a priori value of the current epoch dual-mode DPE receiver state quantity into two parts: a position-clock difference domain a priori value and a velocity-clock drift domain a priori value is: The prior value of the dual-mode DPE receiver state quantity of the current epoch It is decomposed into the position-clock error domain prior value and the velocity-clock drift domain prior value, where the position-clock error domain prior value is expressed as The speed-clock drift domain prior is expressed as 4. The dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals according to claim 1 is characterized in that: In step 3), the method of generating a five-dimensional position-clock error domain grid space and a five-dimensional velocity-clock drift domain grid space with the above-mentioned position-clock error domain prior value and velocity-clock drift domain prior value as the center is: Prior value in position-clock difference domain and speed-clock drift domain prior As the center, generate the five-dimensional position-clock error domain grid space and the five-dimensional velocity-clock drift domain grid space, and record the states corresponding to each position-clock error domain grid point and each velocity-clock drift domain grid point as and Where L represents the total number of grid points.

5. The dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals according to claim 1 is characterized in that: In step 4), the method of using fast Fourier transform to respectively calculate the correlation function and Doppler spectrum of each visible satellite in the received data of the current epoch is: First, the signal obtained by down-converting the GPS L1 and BDS B1C signals received by the dual-mode DPE receiver antenna is expressed as: Wherein, the superscript i represents the physical quantity corresponding to the i-th visible satellite; the subscripts g and b represent the physical quantities corresponding to the visible satellites of GPS L1 and BDS B1C, respectively; M and N represent the number of visible satellites of GPS L1 and BDS B1C, respectively; n(t) represents additive white noise, which is assumed to obey Gaussian distribution; Represents the GPS L1 signal, the formula is: Among them, a i Indicates the amplitude of visible satellite signals; C i (t-τ i ) represents the pseudo-random code of the visible satellite signal; τ i Indicates the code delay of the visible satellite signal; Indicates the Doppler frequency of visible satellite signals; It represents the BDS B1C signal, which is composed of a data component and a pilot component. The energy ratio of the data component and the pilot component is 1:

3. Therefore, the BDS B1C signal is represented as: in, and The pseudo-random codes representing the data component and pilot component of the BDS B1C signal respectively; the BDS B1C signal is further divided into a BOC (1,1) narrowband part and a BOC (6,1) wideband part, where f sc_a =1.023MHz and f sc_b =6.138MHz represents the subcarrier frequencies of the narrowband part and the broadband part respectively; Then, the correlation function and Doppler spectrum of each visible satellite of GPS L1 and BDS B1C in the received data of the current epoch are calculated by fast Fourier transform respectively; first, the correlation function of each visible satellite signal of GPS L1 and BDS B1C is calculated by fast Fourier transform, and the correlation function of GPS L1 signal is calculated by fast Fourier transform. Correlation function with BDS B1C signal Respectively expressed as: Where F represents FFT operation; (·) * represents the conjugate operation; (·) -1 represents the inverse operation; represents the Doppler frequency corresponding to the prior value of the dual-mode DPE receiver state; sc(t) represents the subcarrier of the BDS B1C signal; R g (·) represents the autocorrelation function of the GPS L1 signal: R data / pilot (·) represents the autocorrelation function of the BDS B1C signal: Then use the fast Fourier transform to calculate the Doppler spectrum of each visible satellite signal of GPS L1 and BDS B1C, and the Doppler spectrum of GPSL1 signal And the Doppler spectrum of the BDS B1C signal Respectively expressed as: Among them, τ i- The code delay is mapped from the prior state quantity representing the center of the position-clock domain grid; the Doppler spectrum of the GPS L1 signal and the BDS B1C signal is uniformly expressed as: Among them, T coh Indicates the integration time.

6. The dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals according to claim 1 is characterized in that: In step 5), the method of using a table lookup method to calculate the joint accumulation of the position-clock error domain grid space and the velocity-clock drift domain grid space obtained in step 3) from the correlation function and Doppler spectrum of the above-mentioned visible satellite signals is: First, the joint accumulation of the position-clock error domain grid space is calculated using the table lookup method: the code delay of each visible satellite is calculated according to the receiver state quantity of the grid point in the position-clock error domain grid space: Where c represents the speed of light; p i Indicates the three-dimensional position of the visible satellite; δt i Indicates the clock error of the visible satellite; Then, according to the calculated code delay of each visible satellite signal, the corresponding correlation function value is extracted from the correlation function of each visible satellite signal pre-calculated in step 4), which is the so-called "table lookup method"; finally, the correlation function values ​​of all visible satellite signals extracted at the grid point are accumulated to obtain the joint accumulation of the position-clock error domain grid point, and the joint accumulation of all the position-clock error domain grid points constitutes the joint accumulation of the position-clock error domain grid space; Then use the table lookup method to calculate the joint accumulation of the velocity-clock drift domain grid space: first, calculate the corresponding Doppler frequency of each visible satellite based on the receiver state quantity of the grid point in the velocity-clock drift domain grid space: in, represents the three-dimensional velocity of the visible satellite; f c =1575.42MHz represents the carrier frequency of L1 band; represents the clock drift of the visible satellite; then, according to the calculated Doppler frequencies of the visible satellite signals, the corresponding Doppler frequency values ​​are extracted from the Doppler spectra of the visible satellite signals pre-calculated in step 4) using a table lookup method; finally, the Doppler frequency values ​​of all visible satellite signals extracted at the grid point are accumulated to obtain the joint accumulation of the speed-clock drift domain grid points, and the joint accumulation of all the speed-clock drift domain grid points constitutes the joint accumulation of the speed-clock drift domain grid space.

7. The dual-mode direct position estimation receiver positioning method based on GPS L1 / BDS B1C signals according to claim 1 is characterized in that: In step 6), the method of taking the joint accumulated maximum value of the position-clock error domain grid space as the observed value of the position-clock error of the current epoch, taking the joint accumulated maximum value of the velocity-clock drift domain grid space as the observed value of the velocity-clock drift of the current epoch, and forming the state quantity observed value of the current epoch by the observed values ​​of the position-clock error and the velocity-clock drift is: The joint accumulation maximum value of the position-clock error domain grid space calculated in step 5) is taken as the observation value of the position-clock error of the current epoch, and the joint accumulation maximum value of the velocity-clock drift domain grid space calculated in step 5) is taken as the observation value of the velocity-clock drift of the current epoch, expressed as: The above-mentioned position-clock error and velocity-clock drift observation values ​​constitute the state quantity observation value of the current epoch.

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