A method and system for generating pseudolite signals within a tunnel

Abstract

The application discloses a tunnel inside pseudolite signal generation method and system, and the method comprises the following steps: constructing a satellite digital intermediate frequency signal model; acquiring all satellite analog parameter information inputted in real time, and inputting the analog parameter information into the satellite digital intermediate frequency signal model respectively to generate multi-channel satellite intermediate frequency digital signals; adding and filtering the multi-channel satellite intermediate frequency digital signals, and then carrying out digital-to-analog conversion to obtain satellite intermediate frequency analog signals; and carrying out frequency conversion on the satellite intermediate frequency analog signals to output radio frequency signals. The application designs and generates satellite signals needed to be received by a target analog position in view of the specific environment in a tunnel, can effectively solve the problem of generating navigation signals in the tunnel from nothing, can meet the real-time and reliable positioning demand of a general navigation terminal in the tunnel without any change, and is expected to bring good social and economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of signal simulation, in particular to a tunnel pseudo-satellite signal generation method and system. BACKGROUND

[0002] At present, millions of highway operating vehicles have installed satellite navigation positioning terminals and accessed the nationwide network control system. However, when the key operating vehicles enter the tunnel, the satellite navigation positioning device on the vehicle cannot work normally due to the shielding of the navigation satellite, and the position state of the vehicle cannot be identified. When such vehicles appear abnormal, the monitoring system cannot timely perceive, and thus the best abnormal processing time is missed due to the inaccurate position of the abnormal vehicle, and even a secondary major accident can be caused, resulting in huge losses.

[0003] In order to improve the operation safety level of the tunnel and the supervision ability and service level of the tunnel operation safety, satellite signal simulation technology is adopted to realize the comprehensive coverage of satellite signals in the field of transportation. At present, the satellite navigation signal simulation generation technology abroad is very mature, and there are many related simulation instruments on the market, such as STR4750, STR4760, GSS7700, GSS8000 series of SPIRENT company in the United Kingdom, N7609B series of Agilent company, 1000, 2000, 4000 series satellite simulators developed by CAST company in the United States, and GS100, GS600, GS1010 series developed by Welnavigate company. Most of these simulators abroad adopt modular structure, which is composed of a separate computer and a case or adopts an independent case and a card integrated structure, has strong complex data calculation processing ability, can simulate more channels of satellite navigation signals at the same time, is suitable for low, high and ultrahigh dynamic signal simulation scenes, and can flexibly configure the simulator signals according to the user's demand through the man-machine interface, and is mainly applied to the fields of simulation and performance test during equipment development.

[0004] The satellite navigation signal simulation products on the domestic market at present are mainly GNS8000 series simulator developed by National Defense Science and Technology University, CSG-5000 single-port simulator developed by Aerospace Science and Technology Group 503 Institute, HWA-RNSS-7000 series satellite navigation simulator developed by Huailikaitong company, and simulators developed and produced by Beijing Leike company and Beijing University of Aeronautics and Astronautics, etc.

[0005] At present, the domestic satellite navigation signal simulation products are similar to foreign products, mostly in the mode of signal simulator body combined with computer (or board), which can realize signal simulation generation and flexible configuration of simulation scene according to user demand, although it can simulate satellite signals in various motion states (low, medium and high dynamic) of users, but the simulator structure is complex, the implementation method is complex, the implementation difficulty is high, and the product is expensive, which is more applied to simulation verification and real-time closed-loop performance test in the process of equipment research and development.

[0006] The satellite navigation signal simulation products and methods on the market have the following disadvantages:

[0007] 1) The signal simulation scene is various and complex, and has more redundant functions, and the implementation method is more complex;

[0008] 2) High cost and expensive price;

[0009] 3) It is mostly an auxiliary device for main equipment research and development, the real-time performance of signal simulation generation is not strong, and it cannot directly generate good economic and social benefits. SUMMARY

[0010] Therefore, the application provides a tunnel pseudo-satellite signal generation method and system, which solves the problem that there is no satellite signal in the tunnel and the user cannot be positioned through the satellite navigation signal.

[0011] The first aspect of the application provides a tunnel pseudo-satellite signal generation method, which comprises the following steps: constructing a satellite digital intermediate frequency signal model; acquiring all satellite simulation parameter information input from outside in real time, and inputting the satellite simulation parameter information into the satellite digital intermediate frequency signal model respectively to generate multi-channel satellite intermediate frequency digital signals; adding and filtering the multi-channel satellite intermediate frequency digital signals, and then performing digital-to-analog conversion to obtain satellite intermediate frequency analog signals; and performing frequency conversion on the satellite intermediate frequency analog signals to output radio frequency signals.

[0012] Further, the step of acquiring analog parameter information and inputting into the satellite digital intermediate frequency signal model to generate the satellite intermediate frequency digital signal comprises: acquiring external input information in real time, extracting analog parameter information, the analog parameter information at least including satellite navigation message parameter, target analog position parameter, analog speed parameter and analog time parameter; using the extracted analog parameter information to generate real-time control parameter, the control parameter at least including navigation message bit data stream, pseudo code phase, code frequency control word and carrier frequency control word; using the code frequency control word to control the generated navigation message bit data to transmit in real time according to the established transmission rate; using the pseudo code phase, code frequency control word and carrier frequency control word to generate pseudo code and carrier signal; after aligning the initial edges of the pseudo code and navigation message bit data, XOR adding the two to generate the corresponding spread spectrum code; carrier modulating the spread spectrum code and carrier signal to generate the satellite intermediate frequency digital signal.

[0013] Further, the step of using the extracted analog parameter information to generate real-time control parameter comprises: using the satellite navigation message parameter to calculate the navigation message bit data stream of the satellite, combining the analog time parameter to iteratively calculate the position of each satellite and the signal transmission time; using the analog position parameter, analog time parameter and navigation message parameter to calculate error compensation parameter, the error compensation parameter at least including satellite clock difference compensation, relativistic effect compensation, ionospheric delay error compensation, tropospheric delay error compensation and earth rotation compensation; using the error compensation parameter to correct the satellite signal propagation time, and correcting the satellite signal transmission time according to the corrected satellite signal propagation time; according to the satellite signal transmission time and the set radio frequency local oscillator frequency, sampling frequency and bit width of the digital control oscillator, calculating the pseudo code phase, code frequency control word and carrier frequency control word.

[0014] Further, the method for calculating and compiling the navigation message bit data stream of the satellite comprises: judging whether the current navigation message parameter is valid in real time, if not, updating the navigation message parameter, if yes, compiling the navigation message; dividing the floating point parameter of the navigation message by the proportion factor to become an integer, and then converting it into binary bit data; compiling and filling according to the navigation message frame format and its content one by one until the navigation message data compilation of one superframe is completed; after continuously calculating and compiling the navigation message data of two superframes, using the navigation message data of the second superframe to verify the correctness of the navigation message data of the first superframe; if the navigation message data information of the two superframes is inconsistent, continue to calculate and compile the navigation message data of the next superframe according to the input navigation message parameter until the navigation message data of the adjacent two superframes is consistent, then stop calculating and compiling the navigation message bit data; judging whether the input analog time parameter is close to the whole point in time, if yes, calculating and compiling the navigation message bit data stream of the next period, if not, not performing any operation.

[0015] Further, the method for calculating the position of the satellite and the signal transmission time comprises the following steps: setting an initial satellite signal propagation time; calculating the satellite signal transmission time by using the analog time parameter and the satellite signal propagation time; calculating the satellite position according to the satellite signal transmission time and the navigation message parameter; calculating the satellite true distance by using the analog position parameter and the calculated satellite position, and updating the satellite signal propagation time; iteratively calculating the satellite signal transmission time, the satellite position and the satellite signal propagation time until the satellite position changes less than 3 meters in two adjacent iterations.

[0016] Further, the method for calculating the pseudo-code phase, the code frequency control word and the carrier frequency control word comprises the following steps: calculating the pseudo-code phase of the satellite signal transmission time according to the satellite signal transmission time, the navigation message frame and the characteristics of the pseudo-code sequence and the corresponding relationship between them; calculating the instantaneous speed of the satellite according to the satellite signal transmission time; calculating the relative speed between the satellite and the analog position according to the analog speed parameter and the instantaneous speed of the satellite; calculating the instantaneous carrier Doppler frequency information and the code Doppler frequency information of the satellite signal by using the relative speed, the carrier frequency of the satellite signal and the pseudo-code frequency of the satellite signal; calculating the carrier intermediate frequency, the Doppler carrier intermediate frequency and the Doppler code frequency according to the set radio frequency local oscillator frequency and the carrier Doppler frequency information and the code Doppler frequency information; calculating the code frequency control word and the carrier frequency control word according to the set sampling frequency, the bit width of the digital control oscillator and the Doppler carrier intermediate frequency and the Doppler code frequency.

[0017] The second aspect of the present application provides a tunnel pseudo-satellite signal generation system, which comprises: a memory for storing a computer program; and a processor for executing the computer program to realize the steps of the tunnel pseudo-satellite signal generation method.

[0018] The third aspect of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the steps of the tunnel pseudo-satellite signal generation method.

[0019] The tunnel pseudo-satellite signal generation method and system first establish a satellite digital intermediate frequency signal model, then acquire analog parameter information composed of target analog position information of the tunnel wall calibrated by surveying and mapping and the like, time information, speed information and navigation message parameters of the satellite transmitted by the external equipment of the tunnel through an optical fiber and the like, calculate the satellite position and the satellite signal transmission time, obtain the Beidou / GPS satellite signal that should be received by the analog position point according to the satellite digital intermediate frequency signal model, and broadcast the Beidou / GPS satellite signal through a signal transmission antenna, so as to meet the real-time and reliable positioning requirement of the general navigation terminal in the tunnel without any change. BRIEF DESCRIPTION OF DRAWINGS

[0020] For the purpose of illustration and not limitation, the present application will now be described based on the preferred embodiments thereof, particularly with reference to the attached drawings, in which:

[0021] Figure 1 is a flow chart of a tunnel pseudo-satellite signal generation method provided by an embodiment of the present application;

[0022] Figure 2 is a flow chart of a single-channel satellite intermediate frequency digital signal generation method provided by an embodiment of the present application;

[0023] Figure 3 is a schematic diagram of a tunnel pseudo-satellite signal generation system provided by another embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to enable a more complete understanding of the above-mentioned objects, features and advantages of the present application, the present application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0025] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application. The described embodiments are merely some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0027] Figure 1 is a flow chart of a tunnel pseudo-satellite signal generation method provided by an embodiment of the present application. The tunnel pseudo-satellite signal generation method inputs the analog position information, time information, speed information, and satellite navigation message parameters of the target from the outside, accurately calculates the motion trajectory of the Beidou / GPS on-orbit satellite in real time according to the input information, determines the position coordinates of the on-orbit satellite, then obtains the satellite signal that the analog position point should receive according to the satellite digital intermediate frequency signal model and signal generation mechanism, and finally synchronously broadcasts the standard Beidou / GPS satellite signal through the signal transmitting antenna, so as to meet the real-time and reliable positioning requirements of the general navigation terminal in the tunnel without any change.

[0028] Please refer to the attached Figure 1 The tunnel pseudo-satellite signal generation method includes the following steps:

[0029] S100, constructing a satellite digital intermediate frequency signal model.

[0030] The embodiment mainly relates to analog transmission of an L1 frequency band of a GPS signal or a B1 frequency band of a Beidou signal, and the satellite digital intermediate frequency signal model comprises a GPS satellite digital intermediate frequency signal model generated by an intermediate frequency signal of the L1 frequency band or a Beidou satellite digital intermediate frequency signal model generated by an intermediate frequency signal of the B1 frequency band.

[0031] (1) GPS satellite digital intermediate frequency signal model

[0032] The GPS interface control file is used, the carrier frequency f1 of the signal of the L1 frequency band is 1575.42 MHz, the signal transmitted by the GPS satellite contains navigation text data, a ranging code and a carrier signal, the ranging code on the L1 frequency band contains a C / A code and a P code, and the data code is modulated by spread spectrum, and then is modulated by BPSK with two phase quadrature carriers, and the signal structure can be represented as:

[0033]

[0034] In the formula, P C and P Y are respectively the transmission power of the C / A code and the P code signal, C1 (t) and C2 (t) are respectively the C / A code and the P code signal of the satellite, D (t) is the navigation text data, is the initial phase of the carrier L1, and the following mainly describes the C / A ranging code signal.

[0035] The actual satellite signal received by the receiver is delayed due to the transmission of the troposphere and the ionosphere in addition to the signal delay caused by the geometric distance. The real satellite signal can be represented as the following formula:

[0036]

[0037] The signal containing the carrier Doppler is represented as the following formula:

[0038]

[0039] In the formula, j represents the label of different satellites, represents the carrier initial phase, f d represents the Doppler frequency shift, τ represents the signal transmission delay, and the carrier delay τ carrier and the ranging code delay τ code are two kinds, and can be represented as the following formula:

[0040] τ code = Δt SV + t tropo - t iono + ρ / c

[0041] τ carrier = Δt SV + t tropo + t iono + ρ / c (4)

[0042] where Δt SV is the satellite clock error, t ropot and t iono are troposphere and ionosphere delay errors, ρ represents the geometric transmission distance from satellite to receiver, and c represents the speed of light.

[0043] From the signal expressions of equations (2) and (3), the following equation can be obtained:

[0044]

[0045] In the equation, f d represents the Doppler shift, f1 is the carrier frequency of the L1 band signal, and τ carrier is the carrier delay.

[0046] From the above equation (5), the change of the Doppler shift can be simulated by calculating the carrier transmission delay.

[0047] The GPS satellite digital intermediate frequency signal model can be expressed as:

[0048]

[0049] In the equation, j represents the label of different satellites, P C is the transmission power of the C / A code signal, C1 is the C / A code signal of the satellite, D is the navigation data, T s is the sampling period of the digital signal, k represents the kth sampling time, τ code is the ranging code delay, τ carrier is the carrier delay, f IF is the carrier intermediate frequency, f1 is the carrier frequency of the L1 band signal, and φ represents the initial phase of the carrier.

[0050] The signal simulation of the GPS satellite L1 frequency point is to generate the required simulated satellite digital intermediate frequency signal according to the satellite signal structure and the mathematical model of the digital intermediate frequency signal.

[0051] (2) Beidou satellite digital intermediate frequency signal model

[0052] The carrier frequency of the Beidou satellite signal B1 band is 1561.098 MHz, and its signal is composed of I and Q branches modulated on the carrier. Its signal expression is as follows:

[0053]

[0054] wherein A B1I , A B1Q are the amplitudes of the I and Q branch signals in B1, respectively; C B1I , C B1Q are the ranging codes of the I and Q branch signals in B1, respectively; D B1I , D B1Q are the data codes of the I and Q branch signals in B1, respectively. , and f1 is the carrier frequency of B1.

[0055] Since the Q branch of B1 signal is licensed service and the I branch is open service, the following mainly describes the I branch signal of the signal. The Beidou satellite is divided into MEO / IGSO satellite and GEO satellite, and each type of satellite contains different navigation messages, wherein the D1 navigation message of MEO / IGSO satellite is modulated with NH (Neumann-Hoffman) code, and the GEO satellite uses D2 navigation message. The frequency signal models are also different, and the formula of the actually received MEO / IGSO satellite signal is described as:

[0056]

[0057] The formula of the actually received GEO satellite signal is:

[0058]

[0059] wherein τ carrier and τ code are the carrier delay and the ranging code delay, respectively, f1 is the carrier frequency of B1, is the initial phase value of the carrier, D1 is the D1 navigation message data, D2 is the D2 navigation message data, and NH is the HN code modulated on the D1 navigation message.

[0060] The digital intermediate frequency signal model of MEO / IGSO satellite is:

[0061]

[0062] The digital intermediate frequency signal model of GEO satellite is:

[0063]

[0064] wherein j represents the label of different satellites, A B1I is the amplitude of the I branch signal in B1, C B1I is the ranging code of the I branch signal in B1, T s is the sampling period of the digital signal, k is the kth sampling time, τ code is the ranging code delay, and τ carrierD1 is D1 navigation message data, NH is HN code modulated on D1 navigation message, D2 is D2 navigation message data, f IF f is the carrier frequency of the intermediate frequency signal, f1 is the carrier frequency of the B1 signal, is the initial phase of the carrier.

[0065] The signal simulation of the B1 frequency point of the Beidou satellite is to generate the required simulated satellite digital intermediate frequency signal according to the satellite signal structure and the mathematical model of the digital intermediate frequency signal.

[0066] The satellite digital intermediate frequency signal model is constituted according to the GPS satellite digital intermediate frequency signal model and the Beidou satellite digital intermediate frequency signal model.

[0067] S200, acquiring all satellite simulation parameter information input from the outside, inputting to the satellite digital intermediate frequency signal model respectively, and generating multi-channel satellite intermediate frequency digital signals.

[0068] Figure 2 is a flow chart of the single-channel satellite intermediate frequency digital signal generation provided by an embodiment of the present application. Please refer to Figure 2 The specific implementation method for generating the satellite intermediate frequency digital signal is:

[0069] S201, acquiring external input information in real time, and extracting simulation parameter information.

[0070] The external input information is mainly to provide known parameter information to be simulated for generating standard Beidou / GPS satellite signals, including simulation position information, speed information, time information, and navigation message information of each satellite.

[0071] The simulation position information is a fixed position coordinate of the tunnel wall target calibrated by surveying and mapping method, rather than a trajectory data, and the satellite navigation signal that can be received at this fixed position is simulated at each simulation moment.

[0072] The simulation speed information corresponds to the simulation position information, and is a speed value in a static state, and the theoretical value is 0.

[0073] The simulation time information is the receiving moment of the satellite signal to be simulated, in order to ensure the real-time of the simulation signal, the receiving moment is the current local real-time, which is provided by the external time service device of the tunnel in real time.

[0074] The input satellite combination to be simulated has undergone the satellite optimal distribution selection process, which can ensure that the satellite to be simulated has good geometric distribution and DOP value, and the satellite is necessarily visible, so that the satellite visibility does not need to be judged, and the number of satellites to be simulated is 8 Beidou navigation satellites (B1I frequency point) and 8 GPS navigation satellites (L1 frequency point).

[0075] Since the external input information is inputted according to the agreed format, the simulation parameter information extraction method is as follows:

[0076] According to the agreed format, the corresponding simulation parameters are extracted one by one, including the navigation message parameters of each satellite, the simulation position parameters, the simulation speed parameters and the simulation time parameters, which are then stored in the corresponding structure for subsequent use. The simulation parameter information is the to-be-simulated data transmitted through optical fiber and the like according to the agreed format; the simulation position parameters are the position information of the target points on the tunnel wall calibrated by surveying and mapping and the like; the simulation speed parameters take the theoretical value 0 as the simulation value; the simulation time parameters are the real-time time sequence provided by the external timing device of the tunnel; and each satellite to be simulated has undergone the satellite optimal distribution selection process, and the satellite combination has good geometric distribution and DOP value, and the satellite is necessarily visible, so that the satellite visibility judgment is not necessary.

[0077] The navigation message parameters of the satellite include satellite ephemeris parameters, satellite clock correction parameters, satellite health status, satellite system time information, ionospheric delay correction parameters and satellite almanac parameters, and each part of the parameters has its respective purpose. Using the navigation message parameters of the satellite, on the one hand, the downlink navigation message bit data stream of the satellite can be calculated, and on the other hand, the ephemeris parameters can be used to calculate the position coordinates and instantaneous speed of the satellite. The satellite clock bias compensation, the relativistic effect compensation, the ionospheric delay compensation and the tropospheric delay compensation can be calculated from the simulation position parameters, the simulation time parameters and the navigation message parameters.

[0078] S202, real-time control parameters are generated using the extracted simulation parameter information. The real-time control parameters include the navigation message bit data stream of each satellite, the pseudo code phase, the code frequency control word and the carrier frequency control word.

[0079] Specifically, in step S202, the specific implementation method for generating real-time control parameters is as follows:

[0080] S2021, the navigation message bit data stream of the satellite is calculated and composed using the extracted simulation parameter information.

[0081] In this embodiment, the navigation message bit data of the satellite is calculated and composed in real time using the obtained navigation message parameters of the satellite, and the specific implementation is as follows:

[0082] In this embodiment, the navigation message bit data of the satellite is calculated and composed in real time using the obtained navigation message parameters of the satellite, and the specific implementation is as follows:

[0083] According to the ephemeris reference time, it is judged whether the current ephemeris parameter is valid. If not, the ephemeris parameter is updated; if yes, the navigation message is grouped. Since the input parameter is a floating point data, and the satellite navigation message is binary bit data, the floating point parameter needs to be divided by a scale factor to become an integer, and then converted into binary bit data, and then grouped and filled according to the navigation message frame format and its content one by one until the navigation message of one super frame is grouped. In addition, the update period of GPS satellite ephemeris is 2 hours, and the update period of BDS satellite ephemeris is 1 hour, and generally at the whole point, so according to the validity of the navigation message, it is not necessary to calculate and group the navigation message in real time, but only needs to continuously group the navigation message data of 2 super frames, the second super frame is used to check the correctness of the first super frame data, if the data information of the two super frames is inconsistent, then continue to encode the navigation message data of the next super frame according to the input parameter, until the navigation message data of the adjacent two super frames is consistent, then stop calculating and grouping the navigation message bit data. When the navigation message is issued, the navigation message bit data of one super frame that has passed the check is continuously issued until the input analog time parameter approaches the whole point (GPS satellite message is even whole point) and then the calculation and grouping of the navigation message data of the next period is performed. The algorithm is efficient, real-time and easy to implement as a whole.

[0084] S2022, the position and signal transmission time of the satellite are calculated by using the extracted analog parameter information.

[0085] In this embodiment, the position and signal transmission time of the satellite are calculated by using the navigation message parameter, analog position parameter and analog time parameter of the satellite in the extracted analog parameter information.

[0086] In this embodiment, the calculation method of the position and signal transmission time of the satellite is as follows:

[0087] S2022-1, an initial signal propagation time is set.

[0088] According to the approximate distance of the satellite orbit from the ground, an initial signal propagation time t d0 is set. d = t d0 .

[0089] S2022-2, the satellite signal transmission time T s is calculated.

[0090] T s = T r -t d (12)

[0091] Wherein, T r is the input analog time parameter.

[0092] S2022-3, the satellite signal transmission time Ts and satellite ephemeris parameters to calculate satellite position (x s , y s , z s ).

[0093] S2022-4, according to the following formula (13), using the calculated satellite position and input analog position parameters, calculate satellite true distance and update signal propagation time

[0094]

[0095] Where (x r , y r , z r ) is the spatial rectangular coordinates of the analog position, (x s , y s , z s ) is the spatial rectangular coordinates of the satellite, is the satellite true distance, and c is the speed of light.

[0096] S2022-5, repeat steps S2022-2 ~ S2022-4 until the satellite position changes less than 3 meters in two adjacent iterations, stop iteration calculation.

[0097] The satellite coordinates (x s , y s , z s ) in the spatial rectangular coordinate system, satellite signal propagation time t d and further satellite signal transmission time T s are obtained by the above S2022-1 ~ S2022-5 method.

[0098] S2023, using the extracted analog parameter information, calculate the error compensation parameter.

[0099] This embodiment is to calculate the error compensation parameter value that needs to be compensated by using the analog position parameter, analog time parameter and navigation message parameter in the analog parameter information. Among them, the error compensation parameter mainly includes the propagation delay error in the satellite signal propagation process, including satellite clock error compensation, relativistic effect compensation, ionospheric delay error compensation, tropospheric delay error compensation and earth rotation compensation.

[0100] Among them, the satellite clock error compensation: because the receiver will remove the influence of the satellite clock error in the positioning solution, and the satellite clock error is calculated according to the satellite clock error parameter in the navigation message, therefore, in the satellite signal simulation, the satellite clock error needs to be calculated according to the satellite clock error parameter and added to the satellite signal propagation time calculated in S2022.

[0101] Among them, the relativistic effect compensation: the relativistic effect refers to the phenomenon that the relative clock error between the satellite clock and the receiver clock is caused due to the different motion states (motion speed and gravity potential) of the satellite clock and the receiver clock, so it is necessary to calculate the clock error introduced by the relativistic effect through the relativistic calculation formula, and then add it to the satellite signal propagation time calculated in S2022.

[0102] Among them, ionospheric delay error compensation: the satellite signal will be delayed when passing through the ionosphere, and the ionosphere delay value is estimated in real time according to the commonly used ionospheric delay estimation model, and the delay value is added to the satellite signal propagation time calculated in S2022.

[0103] Among them, the tropospheric delay error compensation: the satellite signal will be delayed when passing through the troposphere, and the troposphere delay value is estimated in real time according to the commonly used troposphere delay estimation model, and the delay value is added to the satellite signal propagation time calculated in S2022.

[0104] Among them, the earth rotation compensation: because the satellite signal propagation needs a certain time, and in this period of time, the earth rotates a certain distance, so the satellite position coordinate system corresponding to the signal transmission time and the satellite position coordinate system corresponding to the signal receiving time are not the same coordinate system, and the rotation angle of the two coordinate systems is the rotation angle of the earth in this period of time, and the position of the satellite also changes in this period of time, so it is necessary to compensate the influence of the earth rotation to the satellite signal propagation time calculated in S2022.

[0105] S2024, using the calculated error compensation parameters, corrects the satellite signal propagation time, and corrects and updates the satellite signal transmission time according to the corrected satellite signal propagation time.

[0106] After the above various necessary error compensation, the satellite signal propagation time t d is corrected, and the satellite signal transmission time T s is also corrected according to the formula T s =T r -t d is further corrected and updated, which can be used to generate correct pseudo code phase and Doppler frequency information subsequently.

[0107] S2025, according to the satellite signal transmission time and the set radio frequency local oscillator frequency, sampling frequency and bit width of digital control oscillator, the pseudo code phase, code frequency control word and carrier frequency control word are calculated.

[0108] In particular, the step method in S2025 is taken as an example of GPS satellite L1 frequency point for detailed description of this embodiment, and Beidou satellite B1 frequency point refers to the method and principle.

[0109] S2025-1, calculate the code phase corresponding to the satellite signal transmission time.

[0110] The code phase information corresponding to the satellite signal transmission time is calculated according to the satellite signal transmission time. Because one frame of the navigation message in the satellite signal is 30s and one sub-frame is 6s, the transmission time T s Modulo 30 to get the count value in the frame, divide the value by 6 and take the integer to get the sub-frame count value, modulo 6 to get the count value in the sub-frame; divide the count value in the sub-frame by 0.6 (the word length in the sub-frame is 0.6s), take the integer to get the word count in the sub-frame, and multiply the decimal part by 0.6 to get the count value in the word; divide the count value in the word by 0.02 (0.02s for one bit), take the integer to get the bit count in the word, and multiply the decimal part by 0.02 to get the count value in the bit; divide the count value in the bit by 0.001 (0.001s for the C / A code period), take the integer to get the millisecond count in the bit, and multiply the decimal part by 0.001 to get the count value in the millisecond; multiply the count value in the millisecond by the code frequency value of the C / A code, take the integer to get the code element count in the C / A code period, and multiply the decimal part by the code frequency value to get the count value in the code element, i.e. the code phase value corresponding to the satellite signal transmission time.

[0111] S2025-2, calculate the instantaneous carrier Doppler frequency and the code Doppler frequency.

[0112] According to the input navigation message parameters and the calculated satellite signal transmission time T s , calculate the instantaneous velocity v s of the satellite, and combine the input analog velocity to calculate the relative velocity between the satellite and the analog position The expression is:

[0113]

[0114] In the formula, is the relative velocity between the satellite and the analog position; v s is the instantaneous velocity of the satellite; v r is the input analog velocity.

[0115] Calculate the instantaneous carrier Doppler frequency of the satellite signal:

[0116]

[0117] In the formula, f car_dop is the instantaneous carrier Doppler frequency; is the relative velocity between the satellite and the analog position; f car is the carrier frequency of the satellite signal; and c is the speed of light.

[0118] The code Doppler frequency of the satellite signal is calculated:

[0119]

[0120] where f code_dop is the code Doppler frequency, f car is the carrier frequency of the satellite signal, and f code is the pseudo code frequency of the satellite signal.

[0121] S2025-3, the carrier intermediate frequency frequency with Doppler and the code frequency with Doppler are calculated.

[0122] According to the set radio frequency local oscillator frequency f0, the carrier intermediate frequency frequency f i is calculated; and in combination with the instantaneous carrier Doppler frequency and the code Doppler frequency calculated in S2025-2, the actual carrier intermediate frequency frequency with Doppler f i ′ and the code frequency with Doppler f code are calculated.

[0123] S2025-4, the carrier frequency control word and the code frequency control word are calculated.

[0124] According to the set sampling frequency FS (set to 50MHz) and the bit width of the NCO (set to 32), in combination with the carrier intermediate frequency frequency with Doppler f i ′ and the code frequency with Doppler f code calculated in S2025-3, the frequency control word FCW of the carrier and the pseudo code can be obtained:

[0125]

[0126]

[0127] where FCW car is the carrier frequency control word; and FCW code is the code frequency control word.

[0128] S203, the pseudo code and the carrier signal are generated by using the generated real-time control parameters of the pseudo code phase, the code frequency control word and the carrier frequency control word.

[0129] The generation of the pseudo code and the carrier is mainly achieved by controlling the code phase and the carrier phase through the code NCO and the carrier NCO, and the speed of the code NCO and the carrier NCO is controlled and updated by the code frequency control word and the carrier frequency control word respectively:

[0130] NCO car = NCO car + FCW car

[0131] NCO code =NCO code +FCW ode (18)

[0132] wherein, NCO car is a carrier NCO, NCO code is a pseudo code NCO.

[0133] According to the generation principle of the code NCO and the pseudo code, the pseudo code sequence corresponding to each satellite can be generated. According to the carrier NCO, the digital carrier signal can be generated by looking up a table.

[0134] S204, the generated pseudo code sequence and the generated real-time control parameter navigation message bit data are XOR added to generate the corresponding spread spectrum code.

[0135] Under the action of the homologous clock, the initial phases of the pseudo code and the navigation message bit data are aligned, the pseudo code and the navigation message bit data are XOR added to generate the corresponding spread spectrum code, and spread spectrum modulation is realized.

[0136] S205, the spread spectrum code generated in S204 and the digital carrier signal generated in S203 are carrier modulated to generate a single-channel satellite intermediate frequency digital signal.

[0137] S300, the satellite intermediate frequency digital signal is digitally-analog converted to obtain a satellite intermediate frequency analog signal.

[0138] According to the single-channel satellite intermediate frequency digital signal generation method in S200, the intermediate frequency digital signals of all input satellites are generated, that is, a multi-channel satellite intermediate frequency digital signal is obtained; after filtering, the multi-channel satellite intermediate frequency digital signals are added and digitally-analog converted to obtain a satellite intermediate frequency analog signal that should be received by an analog position point. In this way, the intermediate frequency digital signals of all satellites are through an analog channel, which well avoids the problem of poor channel consistency and improves the performance.

[0139] S400, the satellite intermediate frequency analog signal is frequency converted to output a radio frequency signal.

[0140] The satellite intermediate frequency analog signal obtained in S300 is up-converted to a radio frequency signal, and the radio frequency signal is attenuated and then broadcast in real time by a transmitting antenna, so as to realize the generation and real-time broadcast of the satellite radio frequency signal.

[0141] The tunnel inside pseudolite signal generation method first establishes a satellite digital intermediate frequency signal model; then, obtains analog parameter information composed of tunnel wall target analog position information calibrated by surveying and mapping and the like, time information, speed information and satellite navigation message parameters and the like transmitted by a tunnel external device through an optical fiber and the like, calculates a satellite position and a satellite signal transmission time, obtains a Beidou / GPS satellite signal that should be received by the analog position point according to the satellite digital intermediate frequency signal model, and synchronously broadcasts the Beidou / GPS satellite signal through a signal transmission antenna, so as to meet the real-time and reliable positioning requirement of a general navigation terminal in the tunnel without any change.

[0142] The analog position information used in the embodiment is a fixed position coordinate instead of a trajectory data, the analog scene is simple, and the real-time performance of the analog signal is strong.

[0143] The tunnel inside pseudolite signal generation method is designed for the specific environment in the tunnel, is strong in pertinence and practicability, is easy to implement, effectively reduces the cost, effectively solves the problem of generating a navigation signal in the tunnel from scratch, and brings good social and economic benefits.

[0144] Corresponding to the above method embodiment, refer to Figure 3 , Figure 3 A structure diagram of a tunnel inside pseudolite signal generation system provided by another embodiment of the application, the system 100 can include:

[0145] The memory 101 is used for storing a computer program;

[0146] The processor 102 is used for implementing the following steps when executing the computer program stored in the memory 101:

[0147] The satellite digital intermediate frequency signal model is constructed; all satellite analog parameter information inputted from outside is acquired in real time and is inputted to the satellite digital intermediate frequency signal model respectively, a multi-channel satellite intermediate frequency digital signal is generated, the multi-channel satellite intermediate frequency digital signal is filtered and added, digital-to-analog conversion is performed, a satellite intermediate frequency analog signal is obtained, and the satellite intermediate frequency analog signal is frequency-converted to output a radio frequency signal.

[0148] For the introduction of the device provided by the application, refer to the above method embodiment, and the application will not be described here.

[0149] Corresponding to the above method embodiment, the application further provides a computer readable storage medium, the computer readable storage medium stores a computer program, and the computer program can implement the following steps when executed by a processor:

[0150] The satellite digital intermediate frequency signal model is constructed; analog parameter information of all satellites inputted in real time is inputted into the satellite digital intermediate frequency signal model respectively to generate multi-channel satellite intermediate frequency digital signals; the multi-channel satellite intermediate frequency digital signals are added and filtered and then converted into digital-analog to obtain satellite intermediate frequency analog signals; the satellite intermediate frequency analog signals are converted in frequency to output radio frequency signals.

[0151] The computer readable storage medium can include a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk and various storage program codes.

[0152] For the computer readable storage medium provided by the application, refer to the above method embodiments, and the application will not be described here.

[0153] The above specific embodiments do not constitute a limitation on the protection scope of the application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can occur depending on design requirements and other factors. Any modification, equivalent replacement and improvement within the spirit and principles of the application should be included in the protection scope of the application.

Claims

1. A method for generating pseudo-satellite signals in a tunnel, characterized in that, include: Construct a satellite digital intermediate frequency signal model; The system acquires the simulated parameter information of all satellites from external input in real time, and inputs it into the satellite digital intermediate frequency signal model to generate multi-channel satellite intermediate frequency digital signals. The satellite intermediate frequency digital signals from multiple channels are summed, filtered, and then converted from digital to analog to obtain the satellite intermediate frequency analog signal. The satellite intermediate frequency analog signal is converted to output a radio frequency signal; The satellite digital intermediate frequency signal model includes the GPS satellite digital intermediate frequency signal model and the BeiDou satellite digital intermediate frequency signal model; The GPS satellite digital intermediate frequency signal model is as follows: In the formula, j represents the designation of different satellites, and P C C1 is the C / A code signal transmission power, D is the satellite's C / A code signal, and T is the navigation message data. s Let τ be the sampling period of the digital signal, k represent the k-th sampling time, and τ be the sampling period of the digital signal. code For the ranging code delay, τ carrier For carrier delay, f IF f1 is the carrier intermediate frequency, f1 is the carrier frequency of the L1 band signal, and φ1 represents the initial phase of the L1 band signal carrier. The BeiDou satellite digital intermediate frequency signal model is as follows: MEO / IGSO satellite digital intermediate frequency signal model: GEO satellite digital intermediate frequency signal model: In the formula, j represents the designation of different satellites, A B1I Let C be the amplitude of the signal in branch I of B1. B1I T is the ranging code for the I branch signal in B1. s Let τ be the sampling period of the digital signal, k be the k-th sampling time, and τ be the sampling period of the digital signal. code For the ranging code delay, τ carrier For carrier delay, D1 is the D1 navigation message data, NH is the HN code modulated on the D1 navigation message, D2 is the D2 navigation message data, f IF f is the carrier frequency of the intermediate frequency signal. B1 Let φ be the carrier frequency of signal B1. B1I This is the initial phase of the carrier wave for signal B1; The method for calculating and compiling the navigation message bit data stream of the satellite is as follows: The system continuously checks whether the current navigation message parameters are valid. If invalid, it updates the navigation message parameters; if valid, it groups the navigation messages. Divide the floating-point parameters of the navigation message by the scaling factor to convert them into integers, and then convert them into binary bit data. Group and fill in the navigation message frame one by one according to its format and content until a superframe of navigation message data is completed. After continuously calculating and grouping the navigation message data of two superframes, the correctness of the navigation message data of the first superframe is verified by using the navigation message data of the second superframe. If the navigation message data information of two superframes is inconsistent, the navigation message data of the next superframe will continue to be calculated and grouped according to the input navigation message parameters until the navigation message data of two adjacent superframes are consistent, then the calculation and grouping of navigation message bit data will stop. The system continuously checks whether the input analog time parameter is close to the hour. If it is, it performs calculation and grouping of the navigation message bit data stream for the next cycle. If not, it does not perform any operation. The simulated position parameters are the fixed position coordinates of the target on the tunnel wall, and each simulated time parameter simulates the satellite navigation signal that can be received at this fixed position; the simulated velocity parameters correspond to the simulated position parameters and are the velocity values ​​in a stationary state.

2. The method for generating pseudo-satellite signals in a tunnel according to claim 1, characterized in that, The steps for obtaining satellite analog parameter information, inputting it into the satellite digital intermediate frequency signal model, and generating the satellite intermediate frequency digital signal include: Real-time acquisition of external input information and extraction of simulation parameter information, which includes at least the navigation message parameters of each satellite, the simulated position parameters of the target, the simulated velocity parameters, and the simulated time parameters; Using the extracted simulation parameter information, real-time control parameters are generated. The control parameters include at least the navigation message bit data stream, pseudocode phase, code frequency control word, and carrier frequency control word for each satellite. The generated navigation message bit data is transmitted in real time at a predetermined transmission rate using code frequency control words. The pseudocode phase, code frequency control word, and carrier frequency control word are used to generate pseudocode and carrier signals; After aligning the pseudocode and the initial edges of the navigation message bit data, XOR the two and add them to generate the corresponding spreading code. The spreading code and carrier signal are carrier modulated to generate a satellite intermediate frequency digital signal.

3. The method for generating pseudo-satellite signals in a tunnel according to claim 2, characterized in that, The step of generating real-time control parameters using the extracted simulation parameter information includes: Using the navigation message parameters of each satellite, the navigation message bit data stream of each satellite is calculated and compiled, and the position and signal transmission time of each satellite are iteratively calculated by combining the simulated time parameters; Using simulated position parameters, simulated time parameters, and navigation message parameters, error compensation parameters are calculated. These error compensation parameters include at least satellite clock error compensation, relativistic effect compensation, ionospheric delay error compensation, tropospheric delay error compensation, and Earth rotation compensation. The satellite signal propagation time is corrected using error compensation parameters, and the satellite signal transmission time is then corrected and updated based on the corrected satellite signal propagation time. Based on the satellite signal transmission time and the set radio frequency local oscillator frequency, sampling frequency, and bit width of the digitally controlled oscillator, calculate the pseudo-code phase, code frequency control word, and carrier frequency control word.

4. The method for generating pseudo-satellite signals in a tunnel according to claim 3, characterized in that, The method for calculating the satellite's position and signal transmission time is as follows: Set the initial satellite signal propagation time; The satellite signal transmission time is calculated using simulated time parameters and satellite signal propagation time. Calculate the satellite position based on the satellite signal transmission time and navigation message parameters; The true distance to the satellite is calculated using simulated position parameters and calculated satellite positions, and the signal propagation time is updated. The satellite signal transmission time, satellite position, and satellite signal propagation time are calculated iteratively until the satellite position change between two adjacent iterations is less than 3 meters.

5. The method for generating pseudo-satellite signals in a tunnel according to claim 2, characterized in that, The calculation methods for the pseudocode phase, code frequency control word, and carrier frequency control word are as follows: The pseudocode phase at the signal transmission time is calculated based on the characteristics of the satellite signal transmission time, navigation message frame, and pseudocode sequence, as well as the correspondence between the two. Calculate the satellite's instantaneous velocity based on the satellite signal transmission time; Calculate the relative velocity between the satellite and the simulated position based on the simulated velocity parameters and the satellite's instantaneous velocity; Using relative velocity, the carrier frequency of the satellite signal, and the pseudocode frequency of the satellite signal, the instantaneous carrier Doppler frequency information and code Doppler frequency information of the satellite signal are calculated. Based on the set radio frequency local oscillator frequency, carrier Doppler frequency information, and code Doppler frequency information, the carrier intermediate frequency, the carrier intermediate frequency with Doppler, and the code frequency with Doppler are calculated. Based on the set sampling frequency and the bit width of the digitally controlled oscillator, as well as the calculated carrier intermediate frequency with Doppler and code frequency with Doppler, the code frequency control word and carrier frequency control word are calculated.

6. A pseudo-satellite signal generation system in a tunnel, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the tunnel pseudo-satellite signal generation method as described in any one of claims 1 to 5.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the tunnel pseudo-satellite signal generation method as described in any one of claims 1 to 5.

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