A time delay calibration method for Loran-C signals and a high-precision Loran-C signal simulator

Abstract

The present application relates to a kind of time delay calibration method of Loran C signal and high-precision Loran C signal simulator, after the calibration of trace deviation and signal time delay, the initial moment of simulated Loran C signal can keep synchronization with UTC (NTSC), the high-precision simulation of Loran C signal is realized;The present application uses variable time delay correction model to calibrate the signal time delay caused by signal attenuator, without establishing time delay correction table, overcome the problem that it is difficult to use measuring equipment to accurately measure time delay when signal attenuation is very large, the realization process is simple, easy to operate.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of time frequency, and relates to a time delay calibration method of a Loran C signal and a high-precision Loran C signal simulator. BACKGROUND

[0002] The Loran C system is a main long-range land-based radio time service and navigation system at present, and can be used as an important supplement and backup means of GNSS to meet the demand of PNT application in most fields. The Loran C signal adopts a low-frequency pulse phase system to provide standard time and position services. According to the international telecommunication union (ITU), the center frequency of the Loran C signal is 100 kHz, and the bandwidth is 90-110 kHz. The high-precision ground-based time service system, which is a major scientific and technological infrastructure construction project in the 13th Five-Year Plan, one of the construction contents is to supplement three Loran C time service stations in the western region of China, which is combined with the existing Loran C system to basically realize the national coverage of the Loran C signal.

[0003] With the development and application of the Loran C system, the demand for the high-precision Loran C signal simulator is more and more urgent in the construction period of the Loran C system and in the research and development, production and performance testing of the Loran C receiver.

[0004] At present, the documents related to Loran C signal simulator mainly include: Paper 1 (Tang Jinyuan, et al. Loran C navigation system ground station signal simulator design [J]. Aviation electronic technology, 2007(03):5-8); Paper 2 (Qiao Yongyan, et al. Design of Loran C navigation system signal generator based on single-chip microcomputer [J]. Ship electronic engineering, 2014, 34(08):175-177+184); Paper 3 (Cui Ke, et al. Loran C navigation signal system simulator based on CPU+FPGA [J]. Spacecraft technology, 2021, 41(01):64-70); Patent 1 (Li Shifeng, et al. Loran C time signal simulator [P]. China patent: 102565817B, 2013); Patent 2 (Lu Hui, et al. Loran-C navigation signal simulation platform based on CPU+FPGA [P]. China patent: 110673510B, 2020); Patent 3 (Yuan Jiangbin, et al. Loran-C navigation signal simulator and method [P]. China patent: 111474564B, 2022); Patent 4 (Sukani, et al. Loran C comprehensive signal generating device [P]. China patent: 111650610B, 2022). The above documents all put forward the design, generation and simulation method of Loran C signal, but they all do not mention the traceability deviation of the simulated Loran C signal and the signal time delay caused by the signal attenuator. Although the Loran C signal simulators provided by Patent 1, Patent 3 and Patent 4 all contain the time and frequency reference of GPS / DB+rubidium atomic clock, but the traceability deviation of the time and frequency reference is not measured and calibrated. In addition, since the center frequency of Loran C signal is 100 kHz, the difference of signal time delay caused by signal attenuator working at different signal attenuation amounts in this frequency band is very large, and the above documents do not mention this problem, nor realize the measurement and calibration of signal time delay.

[0005] In summary, the Loran C signal simulator designed based on the prior art has a large deviation between the simulated Loran C signal and the national standard time UTC (NTSC), and this deviation is uncontrollable, which makes it difficult to realize high-precision Loran C signal simulation and cannot meet the practical application requirements of high-precision Loran C signal simulator for current Loran C system construction and Loran C receiver development. SUMMARY

[0006] Technical problems to be solved

[0007] In order to avoid the shortcomings of the prior art, the present application provides a Loran C signal time delay calibration method and a high-precision Loran C signal simulator, which can simulate and generate high-precision Loran C signal synchronized with the national standard time UTC (NTSC) in real time based on the measurement and calibration of traceability deviation and the measurement and calibration of signal time delay.

[0008] Technical scheme

[0009] The application relates to a time delay calibration method for a high-precision Loran C signal simulator, characterized by variable time delay calibration and traceable deviation calibration.

[0010] The variable time delay calibration comprises the following steps:

[0011] The Loran C signal simulator generates a main station M digital signal, a secondary station X digital signal and a secondary station Y digital signal, and outputs an analog Loran C signal after digital signal synthesis, signal attenuation and filtering, wherein the Loran C signal comprises a main station M signal, a secondary station X signal and a secondary station Y signal.

[0012] When the main station M signal is not subjected to variable time delay calibration, the starting time of the main station M digital signal is synchronized with the starting time of a GRP synchronization signal; according to the attenuation amount m of the main station M signal at a current time, the time delay adjustment amount of the starting time of the main station M digital signal is calculated , and the time delay adjustment amount at the current time is used to make advance adjustment on the time delay of the main station M digital signal at the next time, so that the starting time of the adjusted main station M digital signal is ahead of the starting time of the GRP synchronization signal by an amount equal to the ;

[0013] When the secondary station X signal is not subjected to variable time delay calibration, the starting time of the secondary station X digital signal is delayed relative to the starting time of the GRP synchronization signal by TD1; according to the attenuation amount x of the secondary station X signal at a current time, the time delay adjustment amount of the starting time of the secondary station X digital signal is calculated , and the time delay adjustment amount at the current time is used to make advance adjustment on the time delay of the secondary station X digital signal at the next time, so that the starting time of the adjusted secondary station X digital signal is delayed relative to the starting time of the GRP synchronization signal by an amount of ;

[0014] When the secondary station Y signal is not subjected to variable time delay calibration, the starting time of the secondary station Y digital signal is delayed relative to the starting time of the GRP synchronization signal by TD2; according to the attenuation amount y of the secondary station Y signal at a current time, the time delay adjustment amount of the starting time of the secondary station Y digital signal is calculated , and the time delay adjustment amount at the current time is used to make advance adjustment on the time delay of the secondary station Y digital signal at the next time, so that the starting time of the adjusted secondary station Y digital signal is delayed relative to the starting time of the GRP synchronization signal by an amount of ;

[0015] Thus, the real-time calibration of the variable time delay during the operation of the Loran C signal simulator is completed.

[0016] The source deviation calibration is as follows: Without source deviation calibration, the source deviation calibration unit of the Roland C signal simulator generates a 1PPS_#3 signal synchronized with the 1PPS_#2 signal; the time difference between the 1PPS_#2 signal and the national standard time UTC (NTSC) second signal is measured, and its average value is calculated as the source deviation, denoted as τ. diff The data is then input to the source deviation calibration unit; the source deviation calibration unit, based on the source deviation input at the current time, performs a τ adjustment on the start time of the 1PPS_#3 signal at the next time step. diff Proactive adjustments; real-time calibration of traceability deviations.

[0017] The delay adjustment amount at the start time of the master station M digital signal is calculated based on the attenuation amount m of the master station M signal at the current moment. The calculation is as follows:

[0018] Calculate the signal attenuation control parameters of the master station M signal based on the attenuation m at the current moment. ;

[0019] in: The first signal attenuator in the analog signal output unit The signal attenuation amount of each independent attenuation level; ;

[0020] According to signal attenuation control parameters Calculate the time delay adjustment amount of the master station M signal. :

[0021]

[0022] in: For the first The relative time delay of the signal caused by attenuating the signal with each independent attenuation level. When the attenuation of the master station M signal is zero, the time difference between the start time of the GRP synchronization signal and the third zero-crossing point of the master station M signal in the Roland C signal; When the attenuation of the master station M signal is The time difference between the start time of the GRP synchronization signal and the third zero-crossing point of the master station M signal in the Roland C signal.

[0023] The delay adjustment amount at the start time of the digital signal of the secondary station X is calculated based on the attenuation amount x of the secondary station X signal at the current moment. The calculation is as follows:

[0024] Calculate the signal attenuation control parameters of the secondary station X signal based on the attenuation amount x at the current moment.

[0025]

[0026] According to the attenuation amount y of the slave station Y signal, the time delay adjustment amount of the starting moment of the slave station Y digital signal is calculated The calculation is:

[0027] .

[0028] According to the attenuation amount y of the slave station Y signal, the time delay adjustment amount of the starting moment of the slave station Y digital signal is calculated The calculation is:

[0029] According to the attenuation amount y of the slave station Y signal, the signal attenuation control parameter of the slave station Y signal is calculated

[0030] According to the attenuation amount y of the slave station Y signal, the time delay adjustment amount of the starting moment of the slave station Y digital signal is calculated

[0031] .

[0032] The signal attenuation control parameter of the slave station X signal Output to the attenuator built-in in the analog simulator after the starting moment of the GRP synchronization signal is delayed by TD1 for attenuating the slave station X signal.

[0033] The signal attenuation control parameter of the slave station Y signal Output to the attenuator built-in in the analog simulator after the starting moment of the GRP synchronization signal is delayed by TD2 for attenuating the slave station Y signal.

[0034] A high-precision Loran C signal simulator adopting the time delay calibration method, comprising a Beidou antenna, a Beidou timing receiver, a tameable rubidium atomic clock, an up-conversion unit, a master control unit, a synchronization signal generation unit, a digital signal generation unit, a digital signal synthesis unit and an analog signal output unit; characterized in that it further comprises a traceable deviation calibration unit and a variable time delay calibration unit connected with the up-conversion unit, and the up-conversion unit outputs a 100MHz signal as the working frequency of the traceable deviation calibration unit and the variable time delay calibration unit;

[0035] The input end of the traceable deviation calibration unit is connected with the output end of the tameable rubidium atomic clock, the up-conversion unit and the master control unit respectively, and the output end is connected with the input end of the synchronization signal generation unit; the traceable deviation calibration unit receives the 1PPS_#2 signal of the tameable rubidium atomic clock, generates a 1PPS_#3 signal according to the traceable deviation output by the master control unit, adjusts the starting moment of the 1PPS_#3 signal, and outputs the 1PPS_#3 signal to the synchronization signal generation unit;

[0036] ​​​​​The 1PPS_#2 signal is a pulse per second signal and the 1PPS_#3 signal is a pulse per second signal;

[0037] The input end of the variable time delay calibration unit is connected with the output end of the master unit and the output end of the digital signal generation unit, receives the time delay adjustment amount of the master station M signal, the time delay adjustment amount of the secondary station X signal and the time delay adjustment amount of the secondary station Y signal in the Loran C signal and the digital signal of the digital signal generation unit; the variable time delay calibration unit adjusts the starting time of the Loran C digital signal according to the time delay adjustment amount of the three signals, and outputs the adjusted Loran C digital signal to the digital signal synthesis unit;

[0038] The digital signal synthesis unit superimposes the received master station M digital signal, secondary station X digital signal and secondary station Y digital signal in the time domain to form a digital signal, and outputs to the analog signal output unit.

[0039] The signal flow and data flow of the high-precision Loran C signal simulator are as follows:

[0040] The Beidou timing receiver uses the Beidou antenna to receive the Beidou satellite signal to generate time information, and outputs to the master control unit, generates 1PPS_#1 signal and outputs to the tameable rubidium atomic clock; the time information contains time code information and leap second information;

[0041] The tameable rubidium atomic clock accesses the 1PPS_#1 signal, and outputs a 10MHz signal to the up-conversion unit and outputs the 1PPS_#2 signal to the traceable deviation calibration unit;

[0042] The up-conversion receives the 10MHz output by the tameable rubidium atomic clock after up-conversion and outputs a 100MHz signal as the working frequency of the traceable deviation calibration unit, the synchronization signal generation unit, the digital signal synthesis unit, the master control unit and the variable time delay calibration unit;

[0043] The traceable deviation calibration unit receives the 1PPS_#2 signal output by the tameable rubidium atomic clock, generates a 1PPS_#3 signal synchronized with the 1PPS_#2 signal, and outputs the 1PPS_#3 signal to the synchronization signal generation unit, and adjusts the starting time of the 1PPS_#3 signal according to the traceable deviation output by the master control unit;

[0044] The input end of the synchronization signal is connected with the output end of the traceable deviation calibration unit, and the output end is connected with the input end of the digital signal generation unit; the GRP synchronization signal is generated according to the group repetition period of the 1PPS_#3 signal and the Loran C signal;

[0045] The input end of the digital signal generating unit is connected with the output end of the synchronization signal generating unit, and the output end is connected with the input end of the variable time delay calibration unit; timing information is generated according to the GRP synchronization signal and the group repetition period; data coding is performed according to the timing information and the time service information output by the master control unit; the Loran C pulse signal waveform is read according to the GRP synchronization signal, the data coding result and the station chain time difference, three-way Loran C digital signals including the main station M digital signal, the secondary station X digital signal and the secondary station Y digital signal are obtained and output; the timing information includes millisecond, microsecond and nanosecond;

[0046] Wherein: the GRP synchronization signal is a pulse signal, and the repetition period thereof is equal to the group repetition period, denoted as GRI; the starting time of the GRP synchronization signal is synchronized with the starting time of the 1PPS_#3 signal in the initial state of the simulator; the station chain time difference includes the time difference TD1 between the secondary station X signal and the main station M signal, and the time difference TD2 between the secondary station Y signal and the main station M signal;

[0047] The master control unit receives the group repetition period, the trace deviation, the signal attenuation amount, the station chain time difference and other parameters of the Loran C signal input by the user; receives the time information output by the Beidou timing receiver; calculates the time delay adjustment amount and outputs it to the variable time delay calibration unit; outputs the group repetition period to the synchronization signal generating unit to obtain the time service information by potential arrangement and outputs it to the digital signal generating unit; calculates the signal attenuation control parameter according to the signal attenuation amount and outputs it to the analog signal output unit at a specific time;

[0048] Wherein: the signal attenuation control parameter includes the main station M signal attenuation control parameter, the secondary station X signal attenuation control parameter and the secondary station Y signal attenuation control parameter;

[0049] The variable time delay calibration unit receives the main station M digital signal, the secondary station X digital signal and the secondary station Y digital signal output by the digital signal generating unit; receives the main station M signal time delay adjustment amount, the secondary station X signal time delay adjustment amount and the secondary station Y signal time delay adjustment amount calculated by the master control unit, and adjusts the starting time of the received main station M digital signal, secondary station X digital signal and secondary station Y digital signal respectively, and outputs the adjusted main station M digital signal, secondary station X digital signal and secondary station Y digital signal to the digital signal synthesis unit respectively;

[0050] Wherein: the signal attenuation amount includes the main station M signal attenuation amount, the secondary station X signal attenuation amount and the secondary station Y signal attenuation amount; the starting time of the secondary station X digital signal lags behind the starting time of the main station M digital signal by the TD1; the starting time of the secondary station Y digital signal lags behind the starting time of the main station M digital signal by the TD2;

[0051] The digital signal synthesis unit superimposes the received main station M digital signal, the auxiliary station X digital signal and the auxiliary station Y digital signal in time domain to form a digital signal, and outputs the digital signal to the analog signal output unit;

[0052] The digital-to-analog converter of the analog signal output unit converts the digital signal of the digital signal synthesis unit into an analog signal, the signal attenuator of the analog signal output unit receives the signal attenuation control parameter output by the main control unit and attenuates the analog signal output by the digital-to-analog converter, and the filter of the analog signal output unit filters the analog signal output by the signal attenuator and then outputs the analog Loran C signal.

[0053] Advantages

[0054] The time delay calibration method and the high-precision Loran C signal simulator can keep the starting time of the simulated Loran C signal synchronous with UTC (NTSC) after the trace deviation and the signal time delay are calibrated, and high-precision simulation of the Loran C signal is realized. The variable time delay correction model is used to calibrate the signal time delay caused by the signal attenuator, and a time delay correction table does not need to be established, so that the problem that it is difficult to accurately measure the time delay by using measuring equipment when the signal attenuation is large is overcome, and the realization process is simple and easy to operate. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 The circuit schematic diagram of the high-precision Loran C signal simulator of the embodiment of the application is shown in the figure.

[0056] Figure 2 The timing diagram between the 1PPS_#3 signal and the GRP synchronization signal is shown in the figure.

[0057] Figure 3 The device connection diagram for measuring the trace deviation of the embodiment of the application is shown in the figure.

[0058] Figure 4 The timing diagram among the UTC (NTSC) second signal, the 1PPS_#2 signal and the 1PPS_#3 signal without trace deviation calibration is shown in the figure.

[0059] Figure 5 The timing diagram among the UTC (NTSC) second signal, the 1PPS_#2 signal and the 1PPS_#3 signal after trace deviation calibration is shown in the figure.

[0060] Figure 6 The device connection diagram for measuring the signal time delay of the embodiment of the application is shown in the figure.

[0061] Figure 7 The timing diagram between the Loran C signal and the GRP synchronization signal without variable time delay adjustment is shown in the figure.

[0062] Figure 8 Timing diagram of the variable time delay adjusted Loran C signal and the GRP synchronization signal; DETAILED DESCRIPTION

[0063] The application will be further described in conjunction with the embodiments and drawings:

[0064] Figure 1 The high-precision Loran C signal simulator with time delay calibration comprises a Beidou antenna, a Beidou timing receiver, a tamed rubidium atomic clock, an up-conversion unit, a main control unit, a traceable deviation calibration unit, a synchronization signal generation unit, a digital signal generation unit, a variable time delay calibration unit, a digital signal synthesis unit and an analog signal output unit.

[0065] Compared with the existing Loran C signal simulator, the traceable deviation calibration unit and the variable time delay calibration unit are added.

[0066] The input end of the traceable deviation calibration unit is connected with the output end of the tamed rubidium atomic clock, the up-conversion unit and the main control unit respectively, and the output end is connected with the input end of the synchronization signal generation unit; the traceable deviation calibration unit receives the 1PPS_#2 signal of the tamed rubidium atomic clock, generates the 1PPS_#3 signal according to the traceable deviation output by the main control unit, adjusts the starting time of the 1PPS_#3 signal, and outputs the 1PPS_#3 signal to the synchronization signal generation unit.

[0067] The input end of the variable time delay calibration unit is connected with the output end of the main control unit and the output end of the digital signal generation unit, receives the main station M signal time delay adjustment amount, the secondary station X signal time delay adjustment amount and the secondary station Y signal time delay adjustment amount in the Loran C signal, and receives the digital signal of the digital signal generation unit; the variable time delay calibration unit adjusts the starting time of the Loran C digital signal according to the time delay adjustment amounts of the three signals, and outputs the adjusted Loran C digital signal to the digital signal synthesis unit.

[0068] The Beidou timing receiver receives the Beidou satellite navigation positioning and timing system by the Beidou antenna and generates time information and a 1PPS_#1 signal, wherein the time information comprises time code information and leap second information;

[0069] The tamed rubidium atomic clock accesses the 1PPS_#1 signal and outputs a 10MHz signal and a 1PPS_#2 signal; wherein the 1PPS_#2 signal is synchronized with the 1PPS_#1 signal in the stable working period of the rubidium atomic clock;

[0070] The up-conversion unit up-converts the 10MHz signal to a 100MHz signal, and provides the working frequency for the traceable deviation calibration unit, the synchronization signal generation unit, the digital signal generation unit and the variable time delay calibration unit.

[0071] The main functions of the control unit are as follows:

[0072] (1) Receive the configuration information input by the user, including but not limited to group repetition period, trace deviation, signal attenuation, time difference of station chain, other parameters;

[0073] Among them: signal attenuation includes: main station M signal attenuation, denoted as m (unit dB); vice station X signal attenuation, denoted as x (unit dB); vice station Y signal attenuation, denoted as y (unit dB);

[0074] The time difference of station chain includes: the time difference of vice station X signal and main station M signal, denoted as TD1 (unit second); the time difference of vice station Y signal and main station M signal, denoted as TD2 (unit second);

[0075] Other parameters include station identification, system state;

[0076] (2) Receive the time information output by the Beidou timing receiver;

[0077] (3) According to the signal attenuation, calculate the time delay modulation amount through the variable time delay correction model, including , and , and output to the variable time delay calibration unit;

[0078] Among them: denotes the time delay adjustment amount of the main station M signal when the main station M signal attenuation is m , unit second; denotes the time delay adjustment amount of the vice station X signal when the vice station X signal attenuation is x, unit second; denotes the time delay adjustment amount of the vice station Y signal when the vice station Y signal attenuation is y, unit second;

[0079] (4) Output the group repetition period to the synchronization signal generation unit;

[0080] (5) Arrange the time information, other information in a specific format to obtain the time service information and output to the digital signal generation unit;

[0081] (6) According to the signal attenuation, calculate the signal attenuation control parameters, including , and , wherein ;

[0082] Among them: is the signal attenuation control parameter of the main station M signal when the main station M signal attenuation is the signal attenuation control parameter calculated from the signal attenuation amount x of the secondary station X; the signal attenuation control parameter calculated from the signal attenuation amount y of the secondary station Y; the signal attenuation control parameter calculated from the signal attenuation amount y of the secondary station Y;

[0083] (7) sequentially outputting the , and to the analog signal output unit at specific time points, which is implemented as follows:

[0084] outputting the at the starting time point of the GRP synchronization signal;

[0085] outputting the after delaying the TD1 at the starting time point of the GRP synchronization signal;

[0086] outputting the after delaying the TD2 at the starting time point of the GRP synchronization signal;

[0087] The main function of the trace deviation calibration unit is to generate a 1PPS_#3 signal and adjust the starting time point of the 1PPS_#3 signal according to the trace deviation;

[0088] wherein the 1PPS_#3 signal is strictly synchronized with the 1PPS_#2 signal before adjustment;

[0089] The function of the synchronization signal generation unit is to generate a GRP synchronization signal according to the 1PPS_#3 signal and the group repetition period;

[0090] wherein the GRP synchronization signal is a pulse signal, and its repetition period is equal to the group repetition period; the starting time point of the GRP synchronization signal is strictly aligned with the starting time point of the 1PPS_#3 signal in the initial state of the simulator.

[0091] The function of the digital signal generation unit is to generate timing information according to the GRP synchronization signal and the group repetition period, to encode data according to the timing information and the time information, and to obtain and output three-way Loran C digital signals, including the primary station M digital signal, the secondary station X digital signal and the secondary station Y digital signal, according to the GRP synchronization signal, the data encoding result and the station chain time difference reading Loran C pulse signal waveform;

[0092] wherein the starting time point of the secondary station X digital signal lags behind the starting time point of the primary station M digital signal by TD1; the starting time point of the secondary station Y digital signal lags behind the starting time point of the primary station M digital signal by TD2;

[0093] As Figure 2As shown, the timing information refers to the deviation of the starting time of the GRP synchronization signal from the starting time of the 1PPS_#3 signal, including milliseconds, microseconds and nanoseconds; in the initial state of the simulator, the GRP synchronization signal is synchronized with the 1PPS_#3 signal (i.e. the timing information is 0), and the next synchronization time is related to GRI, and since GRI is much smaller than 1s, GRI generally has values of 60ms, 74.3ms, 83.9ms, etc. (which can be set by the user), so in order to enable the user to achieve fast timing, this deviation must be modulated into the signal by data, and the user can recover the 1PP_#3 signal after demodulating the deviation, thereby achieving fast timing (without waiting for the GRP synchronization signal to be synchronized with the 1PPS_#3 signal before timing).

[0094] The main functions of the variable delay calibration unit are: adjusting the starting time of the main station M digital signal in advance and outputting, the adjustment amount being ; adjusting the starting time of the auxiliary station X digital signal in advance and outputting, the adjustment amount being ; adjusting the starting time of the auxiliary station Y digital signal in advance and outputting, the adjustment amount being .

[0095] The main function of the digital signal synthesis unit is to superimpose the main station M digital signal, the auxiliary station X digital signal and the auxiliary station Y digital signal whose time delays have been adjusted by the variable delay calibration unit in the time domain, to form a digital signal, and output;

[0096] The main functions of the analog output unit mainly consist of an analog-to-digital converter, a signal attenuator and a filter, which are as follows:

[0097] (1) The analog-to-digital converter converts the digital signal output by the digital signal synthesis unit into an analog signal, and outputs;

[0098] (2) The signal attenuator is a digital attenuator, which attenuates the amplitude of the analog signal output by the analog-to-digital converter according to the signal attenuation amount received at the current time, and outputs; if the received signal attenuation amount is 0, it means that the signal is not attenuated.

[0099] Among them: the signal attenuator contains N independent attenuation positions, and the signal attenuation amount of each independent position is much smaller than the total signal attenuation amount of the signal attenuator;

[0100] (3) The filter is mainly used to filter the analog signal output by the signal attenuator and output a Loran C signal.

[0101] In the high-precision Loran C signal simulator, the steps of the time delay calibration method are:

[0102] Step 1, refer to Figure 3, the time difference between the 1PPS_#2 signal and the UTC (NTSC) second signal is measured by the time interval timer, and the traceability deviation is calculated from the time difference;

[0103] Step 1.1, after the Beidou timing receiver works normally and outputs the 1PPS_#1 to the tameable rubidium atomic clock, the following steps are executed;

[0104] Step 1.2, after the tameable rubidium atomic clock works normally for 4 hours, the time difference data measured by the time interval timer is collected and recorded by the data acquisition software in the computer, and the data acquisition time is T (unit: hour);

[0105] Optionally, the T is not less than 2 hours;

[0106] Step 1.3, the mean value of the time difference data is calculated, as shown in the following formula:

[0107] (1)

[0108] In the formula: is the traceability deviation (unit: second); represents the i time difference data; represents the number of time difference data;

[0109] Step 2, the traceability deviation calibration unit adjusts the 1PPS_#3 by using the calculated traceability deviation;

[0110] Step 2.1, the calculated traceability deviation is input to the main control unit through the simulator interface;

[0111] Step 2.2, the main control unit sends to the traceability deviation calibration unit through the data bus;

[0112] Step 2.3, the traceability deviation calibration unit makes advance adjustment to the starting time of the 1PPS_#3 signal according to the received , so as to realize the calibration of the traceability deviation;

[0113] Figure 4 is the timing diagram between the UTC (NTSC) second signal, the 1PPS_#2 signal and the 1PPS_#3 signal when the traceability deviation is not calibrated, which shows that the 1PPS_#3 signal is synchronized with the 1PPS_#2 signal, and the starting time of the 1PPS_#3 signal lags behind the starting time of the UTC (NTSC) second by time; Figure 5The timing diagram among the UTC (NTSC) second signal, the 1PPS_#2 signal and the 1PPS_#3 signal after the traceability deviation calibration is shown in the figure, which shows that the 1PPS_#3 signal is synchronized with the UTC (NTSC) second after the advance adjustment of the starting time of the 1PPS_#3 signal. The following is a brief description of the implementation process of the advance adjustment of the starting time of the 1PPS_#3 signal.

[0114] The working frequency is denoted as fs (the value in the embodiment is 100MHz), a timer A is set in the simulator, the count value of the timer is accumulated by 1 at each sampling time (i.e. the reciprocal of fs), the starting time of the 1PPS_#2 signal is taken as the time reference, and it is assumed that the current time is 0 (i.e. the count value of the timer is 0): when the traceability deviation calibration is not performed, a 1PPS_#3 signal is generated when the accumulated value of the timer is fs*1s, a 1PPS_#3 signal is generated again when the accumulated value is fs*2s, and so on, at this time, the 1PPS_#3 signal is synchronized with the 1PPS_#2 signal; when the traceability deviation calibration is performed, a 1PPS_#3 signal is generated when the accumulated value is , a 1PPS_#3 signal is generated again when the accumulated value is , and so on, which ensures that the starting time of the 1PPS_#3 signal is adjusted by relative to the starting time of the 1PPS_#2 signal, and the synchronization between the 1PPS_#3 signal and the UTC (NTSC) second is realized.

[0115] Step 3, referring to Figure 6 , the signal time delay caused by each independent attenuation position of the signal attenuator is measured by using the oscilloscope, and thus the variable time delay correction model parameters are obtained;

[0116] Step 3.1, the GRP synchronization signal and the Loran C signal output by the simulator are connected to channel 1 and channel 2 of the oscilloscope respectively;

[0117] Step 3.2, the channel 1 of the oscilloscope is set as the trigger channel;

[0118] Step 3.3, the signal attenuation amount is set to zero (i.e. the signal is not attenuated) by the main control unit;

[0119] Step 3.4, the oscilloscope is adjusted, and the time difference between the starting time of the GRP signal and the third zero-crossing point of the main station M signal in the Loran C signal is measured by using the time difference measurement function of the oscilloscope, and is denoted as ;

[0120] Step 3.5, referring to step 3.4, the time difference between the starting time of the GRP signal and the third zero-crossing point of the main station M signal is measured when the signal attenuation amount is , and is denoted as ;

[0121] wherein the attenuation amount corresponding to the signal attenuation amount of the jth independent attenuation stage of the signal attenuator; ;

[0122] Step 3.6, according to the signal attenuation amount set by the user, the variable time delay correction model is calculated to obtain the signal relative time delay caused by the attenuation of the signal in the nth independent attenuation stage ; ; wherein: and are the variable time delay correction model parameters;

[0123] Step 4, according to the signal attenuation amount set by the user and the variable time delay correction model, the time delay adjustment amount is calculated;

[0124] Step 4.1, input and to the main control unit;

[0125] Step 4.2, taking the main station M signal attenuation amount as an example, the main control unit calculates the signal attenuation control parameter according to , and the calculation method is as follows:

[0126] (2)

[0127] After the signal attenuator receives , it will choose to enable the jth independent attenuation stage according to the specific value of , and when indicates enablement, and when indicates non-enablement; for example, assuming that the signal attenuator contains 3 independent attenuation stages, the signal attenuation amount of the 1st attenuation stage is 1dB, the signal attenuation amount of the 2nd attenuation stage is 2dB, and the signal attenuation amount of the 3rd attenuation stage is 4dB, when the signal attenuation amount is 5dB, it can be calculated that , , , at this time, after the signal attenuator receives , it will choose to enable the 1st attenuation stage and the 3rd attenuation stage in series to achieve a signal attenuation amount of 5dB.

[0128] Step 4.3, the main control unit calculates the time delay adjustment amount of the main station M signal according to the , , and , and the calculation formula is as follows:

[0129] ​​ (3)

[0130] The formula (3) is the mathematical expression of the variable time delay correction model.

[0131] Wherein: is the relative time delay caused by the attenuation of the signal in the th independent attenuation stage, is the time difference between the starting time of the GRP synchronization signal and the third cycle zero-crossing point of the main station M signal in the Loran-C signal when the attenuation amount of the main station M signal is zero; is the time difference between the starting time of the GRP synchronization signal and the third cycle zero-crossing point of the main station M signal in the Loran-C signal when the attenuation amount of the main station M signal is .

[0132] The calculation of the time delay adjustment amount of the starting time of the digital signal of the secondary station X is .

[0133] According to the attenuation amount x of the secondary station X signal at the current time, the signal attenuation control parameter of the secondary station X signal is calculated

[0134] According to the attenuation amount x of the secondary station X signal at the current time, the signal attenuation control parameter of the secondary station X signal is calculated .

[0135] .

[0136] The calculation of the time delay adjustment amount of the starting time of the digital signal of the secondary station Y is .

[0137] According to the attenuation amount y of the secondary station Y signal, the signal attenuation control parameter of the secondary station Y signal is calculated .

[0138] According to the attenuation amount y of the secondary station Y signal, the signal attenuation control parameter of the secondary station Y signal is calculated .

[0139] .

[0140] Step 5, the variable time delay calibration unit adjusts the signal time delay according to the time delay modulation amount;

[0141] Step 5.1, the main control unit sends the calculated , and to the variable time delay calibration unit through the data bus;

[0142] ​​Step 5.2, the variable time delay calibration unit makes an advance adjustment on the starting time of the main station M digital signal outputted by the digital signal generation unit, makes an advance adjustment on the starting time of the X-station digital signal outputted by the digital signal generation unit, and makes an advance adjustment on the starting time of the Y-station digital signal outputted by the digital signal generation unit, so as to realize calibration of the signal time delay.

[0143] Figure 7 Fig. 3 is a timing diagram between the Loran C signal and the GRP synchronization signal when no variable time delay adjustment is made, which shows that the starting time of the main station M digital signal is synchronized with the starting time of the GRP synchronization signal, the starting time of the X-station signal is delayed by TD1 relative to the starting time of the GRP synchronization signal, and the starting time of the Y-station signal is delayed by TD2 relative to the starting time of the GRP synchronization signal;

[0144] Figure 8 Fig. 4 is a timing diagram between the Loran C signal and the GRP synchronization signal after the variable time delay adjustment is made, which shows that after the variable time delay adjustment is made, the starting time of the main station M digital signal is ahead of the starting time of the GRP synchronization signal by a time of , the starting time of the X-station signal is delayed by a time of relative to the starting time of the GRP synchronization signal, and the starting time of the Y-station signal is delayed by a time of relative to the starting time of the GRP synchronization signal.

[0145] The variable time delay adjustment does not necessarily start at the initial time, but starts as soon as the user sets the signal attenuation (or updates the attenuation attenuation). The timing of the adjustment can be completed before the next GRP signal starting time comes. In actual situation, the user cannot frequently update the signal attenuation, so the timing of the adjustment is not particularly strict. The following briefly describes the implementation process of the advance adjustment of the variable time delay.

[0146] Let the working frequency be fs (the value in the embodiment is 100 MHz), and set a timer B in the simulator. The count value of the timer is accumulated by 1 at each sampling time (i.e. the reciprocal of fs). Take the starting time of the GRP synchronization signal as the time reference, and assume that the current time is 0 (i.e. the count value of the timer is 0). When no variable time delay adjustment is made, the main station M digital signal is generated at the count value of fs*GRI, the X-station digital signal is generated at the count value of , and the Y-station digital signal is generated at the count value of When the variable time delay adjustment is made, the main station M digital signal is generated at the count value of , the X-station digital signal is generated at the count value of , and the Y-station digital signal is generated at the count value of​​​ The substation Y digital signal is generated; during the operation of the simulator, the main station M digital signal, the substation X digital signal and the substation Y digital signal are repeatedly generated at every other Loran C group repetition period GRI time.

[0147] The beneficial effects of the variable time delay calibration method provided by the embodiment are further explained as follows:

[0148] The prior art Loran C signal simulator does not involve the signal delay caused by the signal attenuator when the signal attenuator attenuates the signal. Since the center frequency of the Loran C signal is 100 kHz, the difference in the signal delay caused by the signal attenuator working at different signal attenuation amounts in the frequency band is very large (may cause a subtle amount of time delay difference), that is, the signal delay caused by the signal attenuator is variable, which will seriously affect the accuracy of the Loran C signal simulated by the Loran C signal simulator. For example, when the attenuation amounts of the main station M signal, the substation X signal and the substation Y signal are inconsistent and differ greatly, due to the influence of the signal attenuator, the time difference between the substation X signal and the main station M signal output by the simulator is no longer TD1, and the time difference between the substation Y signal and the main station M signal is no longer TD2. When the long wave receiver accesses the Loran C signal output by the simulator for positioning, the positioning result will have a serious deviation (the long wave receiver needs to obtain TD1 and TD2 when positioning), which does not utilize the function and performance test of the long wave receiver.

[0149] In order to eliminate the signal delay caused by the signal attenuator, a conventional idea is to use an oscilloscope to measure the signal delay of the signal attenuator working at different attenuation amounts, thereby constructing a time delay correction table, and using a table lookup method to calibrate the signal delay. However, actual engineering shows that since the oscilloscope and the simulator both have a non-negligible noise floor, when the Loran C signal attenuation is large, due to the influence of the noise floor, the oscilloscope cannot accurately measure the signal delay, which is the main reason why the Loran C signal simulator is difficult to effectively handle the signal delay caused by the signal attenuator.

[0150] The variable time delay calibration method and the implementation device thereof provided by the embodiment overcome the deficiencies of the prior art, mainly in the following aspects:

[0151] (1) The embodiment provides a variable time delay correction model as shown in formula (3), through which the signal delay caused by any signal attenuation can be calculated, without the need to construct a time delay correction table in advance, and the implementation process is simple;

[0152] (2) The Loran C signal simulator provided by the embodiment generates the main station M signal, the auxiliary station X signal and the auxiliary station Y signal in the Loran C signal through the same signal attenuator to realize signal attenuation, so the signal attenuation caused by the three signals under the same signal attenuation is the same, and therefore the same variable time delay correction model can be used to realize signal time delay calculation;

[0153] (3) The embodiment measures the model parameters in the variable time delay correction model and When the signal attenuator is measured, the signal time delay caused by the signal attenuation of each independent attenuation position of the signal attenuator is measured, and since the attenuation of each independent attenuation position of the signal attenuator is far less than the total attenuation of the signal attenuator, the signal time delay caused by the signal attenuation of each independent attenuation position of the signal attenuator can be measured by using an oscilloscope, and high measurement accuracy can be ensured.

[0154] (4) In the process of measuring the model parameters in the variable time delay correction model and , as described in steps 3.1-3.6, the time difference between the starting time of the GRP signal and the third cycle zero point of the main station M signal in the Loran C signal is measured by using an oscilloscope, instead of directly measuring the time difference between the starting time of the GRP signal and the starting time of the main station M signal in the Loran C signal, because: on the one hand, the signal envelope near the starting time of the main station M signal is small, and the oscilloscope is difficult to accurately capture the starting time of the main station M signal; on the other hand, the long wave receiver usually captures the main station M signal and then tracks the third cycle zero point to realize timing, so the time delay calibration of the third cycle zero point is particularly important.

Claims

1. A time delay calibration method for a high-precision Roland C signal simulator, characterized in that... This includes variable delay calibration and source deviation calibration; The variable delay calibration: The Roland C signal simulator generates a master station M digital signal, a slave station X digital signal, and a slave station Y digital signal, and outputs an analog Roland C signal after digital signal synthesis, signal attenuation, and filtering. The Roland C signal includes the master station M signal, the slave station X signal, and the slave station Y signal. When the master station M signal is not calibrated with variable delay, the start time of the master station M digital signal is synchronized with the start time of the GRP synchronization signal; the delay adjustment amount of the master station M digital signal at the start time is calculated based on the attenuation m of the master station M signal at the current time. And adjust the time delay at that moment. To adjust the time delay of the master station M digital signal at the next moment The adjustment is made so that the start time of the master station M digital signal is ahead of the start time of the GRP synchronization signal, and the lead amount is equal to the stated... ; When the secondary station X signal is not calibrated with variable delay, the start time of the secondary station X digital signal is delayed by TD1 relative to the start time of the GRP synchronization signal; the delay adjustment amount of the secondary station X digital signal start time is calculated based on the attenuation amount x of the secondary station X signal at the current time. And adjust the time delay at that moment. To determine the time delay of the digital signal from the secondary station X at the next moment. The start time delay of the adjusted secondary station X digital signal is relative to the start time of the GRP synchronization signal. The delay; When the secondary station Y signal is not calibrated with variable time delay, the start time of the secondary station Y digital signal has a delay of TD2 relative to the start time of the GRP synchronization signal; the time delay modulation amount at the start time of the secondary station Y digital signal is calculated based on the attenuation amount y of the secondary station Y signal at the current time. And adjust the time delay at that moment. To determine the time delay of the digital signal of the secondary station Y at the next moment. The adjustment is made in advance, and the start time of the adjusted secondary station Y digital signal is relative to the start time of the GRP synchronization signal. The delay; This completes the real-time calibration of variable time delay during operation on the Roland C signal simulator; The source deviation calibration is as follows: Without source deviation calibration, the source deviation calibration unit of the Roland C signal simulator generates a 1PPS_#3 signal synchronized with the 1PPS_#2 signal; the time difference between the 1PPS_#2 signal and the national standard time UTC (NTSC) second signal is measured, and its average value is calculated as the source deviation, denoted as τ. diff The data is then input to the source deviation calibration unit; the source deviation calibration unit, based on the source deviation input at the current time, performs a τ adjustment on the start time of the 1PPS_#3 signal at the next time step. diff Proactive adjustments; real-time calibration of traceability deviations; The delay adjustment amount at the start time of the master station M digital signal is calculated based on the attenuation amount m of the master station M signal at the current moment. The calculation is as follows: Calculate the signal attenuation control parameters of the master station M signal based on the attenuation m at the current moment. ; in: The first signal attenuator in the analog signal output unit The signal attenuation amount of each independent attenuation level; ; According to signal attenuation control parameters Calculate the time delay adjustment amount of the master station M signal. : in: For the first The relative time delay of the signal caused by attenuating the signal with each independent attenuation level. When the attenuation of the master station M signal is zero, the time difference between the start time of the GRP synchronization signal and the third zero-crossing point of the master station M signal in the Roland C signal; When the attenuation of the master station M signal is The time difference between the start time of the GRP synchronization signal and the third zero-crossing point of the master station M signal in the Roland C signal; The delay adjustment amount at the start time of the digital signal of the secondary station X is calculated based on the attenuation amount x of the secondary station X signal at the current moment. The calculation is as follows: Calculate the signal attenuation control parameters of the secondary station X signal based on the attenuation amount x at the current moment. ； according to Calculate the time delay adjustment amount at the start time of the digital signal of the secondary station X. : ； The delay adjustment amount for the start time of the secondary station Y digital signal is calculated based on the attenuation amount y of the secondary station Y signal at the current moment. The calculation is: Calculate the signal attenuation control parameters of the secondary station's Y signal based on the attenuation y. ; according to Calculate the time delay adjustment amount at the start time of the secondary station's Y digital signal. ; 。 2. The time delay calibration method for the high-precision Roland C signal simulator according to claim 1, characterized in that: The signal attenuation control parameters of the secondary station X signal The GRP synchronization signal is output to the simulator's built-in attenuator after a delay of TD1 at the start time to attenuate the secondary station X signal.

3. The time delay calibration method for the high-precision Roland C signal simulator according to claim 1, characterized in that: The signal attenuation control parameters of the secondary station Y signal The GRP synchronization signal is output to the simulator's built-in attenuator after a delay of TD2 at the start time to attenuate the secondary station Y signal.

4. A high-precision Loran-C signal simulator employing the time delay calibration method described in any one of claims 1 to 3, comprising a BeiDou antenna, a BeiDou timing receiver, a disciplined rubidium atomic clock, an up-conversion unit, a main control unit, a synchronization signal generation unit, a digital signal generation unit, a digital signal synthesis unit, and an analog signal output unit; characterized in that: It also includes a traceability deviation calibration unit and a variable time delay calibration unit connected to the upconversion unit. The upconversion unit outputs a 100MHz signal as the operating frequency of the traceability deviation calibration unit and the variable time delay calibration unit. The input terminal of the traceability deviation calibration unit is connected to the output terminals of the disciplined rubidium atomic clock, the up-conversion unit, and the main control unit, respectively, and the output terminal is connected to the input terminal of the synchronization signal generation unit. The traceability deviation calibration unit receives the 1PPS_#2 signal from the disciplined rubidium atomic clock, generates the 1PPS_#3 signal based on the traceability deviation output by the main control unit, adjusts the start time of the 1PPS_#3 signal, and outputs the 1PPS_#3 signal to the synchronization signal generation unit. The 1PPS_#2 signal is a second pulse signal and the 1PPS_#3 signal is a second pulse signal; The input terminal of the variable delay calibration unit is connected to the output terminal of the main control unit and the output terminal of the digital signal generation unit. It receives the delay adjustment amount of the main station M signal, the delay adjustment amount of the secondary station X signal, and the delay adjustment amount of the secondary station Y signal in the Loland C signal, as well as the digital signal from the digital signal generation unit. The variable delay calibration unit adjusts the start time of the Loland C digital signal according to the delay adjustment amount of the three signals, and outputs the adjusted Loland C digital signal to the digital signal synthesis unit. The digital signal synthesis unit superimposes the received main station M digital signal, auxiliary station X digital signal and auxiliary station Y digital signal in the time domain to form a digital signal, and outputs it to the analog signal output unit.

5. The high-precision Loran C signal simulator according to claim 4, characterized in that: The signal stream and data stream of the high-precision Roland C signal simulator are as follows: The BeiDou timing receiver uses a BeiDou antenna to receive BeiDou satellite signals, generates time information, and outputs it to the main control unit. It also generates a 1PPS_#1 signal and outputs it to a disciplined rubidium atomic clock. The time information includes time code information and leap second information. The docile rubidium atomic clock receives the 1PPS_#1 signal and outputs a 10MHz signal to the upconversion unit and a 1PPS_#2 signal to the traceability deviation calibration unit. The upconversion receiver receives a 10MHz signal from a disciplined rubidium atomic clock, which is then upconverted to output a 100MHz signal. This signal serves as the operating frequency for the traceability deviation calibration unit, synchronization signal generation unit, digital signal synthesis unit, main control unit, and variable delay calibration unit. The traceability deviation calibration unit receives the 1PPS_#2 signal output by the disciplined rubidium atomic clock, generates a 1PPS_#3 signal synchronized with the 1PPS_#2 signal, and outputs the 1PPS_#3 signal to the synchronization signal generation unit. Based on the traceability deviation output by the main control unit, the start time of the 1PPS_#3 signal is then adjusted. The input terminal of the synchronization signal is connected to the output of the traceability deviation calibration unit, and its output terminal is connected to the input terminal of the digital signal generation unit; the GRP synchronization signal is generated according to the group repetition period of the 1PPS_#3 signal and the Roland C signal. The input terminal of the digital signal generation unit is connected to the output terminal of the synchronization signal generation unit, and its output terminal is connected to the input terminal of the variable delay calibration unit. Timing information is generated based on the GRP synchronization signal and the group repetition cycle; data encoding is performed based on the timing information output by the main control unit and the timing information; Based on the GRP synchronization signal, data encoding result, and station chain time difference, the Loran C pulse signal waveform is read, and three Loran C digital signals are obtained and output, including the main station M digital signal, the auxiliary station X digital signal, and the auxiliary station Y digital signal; the timing information includes milliseconds, microseconds, and nanoseconds. Wherein: the GRP synchronization signal is a pulse signal, and its repetition period is equal to the group repetition period, denoted as GRI; the start time of the GRP synchronization signal is synchronized with the start time of the 1PPS_#3 signal in the initial state of the simulator; the station chain time difference includes the time difference TD1 between the secondary station X signal and the primary station M signal, and the time difference TD2 between the secondary station Y signal and the primary station M signal; The main control unit receives the group repetition period, source deviation, signal attenuation, station chain time difference, and other parameters of the Loran C signal input by the user; receives the time information output by the Beidou timing receiver; calculates the time delay adjustment and outputs it to the variable time delay calibration unit; outputs the group repetition period to the synchronization signal generation unit, performs potential arrangement to obtain timing information and outputs it to the digital signal generation unit; calculates the signal attenuation control parameters based on the signal attenuation and outputs them to the analog signal output unit at specific times. Wherein: the signal attenuation control parameters include the main station M signal attenuation control parameters, the secondary station X signal attenuation control parameters, and the secondary station Y signal attenuation control parameters; The variable delay calibration unit receives the main station M digital signal, the secondary station X digital signal, and the secondary station Y digital signal output by the digital signal generation unit; it receives the delay adjustment amount of the main station M signal, the secondary station X signal, and the secondary station Y signal calculated by the main control unit, and adjusts the start time of the received main station M digital signal, secondary station X digital signal, and secondary station Y digital signal respectively, and outputs the adjusted main station M digital signal, secondary station X digital signal, and secondary station Y digital signal to the digital signal synthesis unit respectively. Wherein: the signal attenuation includes the attenuation of the main station M signal, the attenuation of the secondary station X signal, and the attenuation of the secondary station Y signal; the start time of the secondary station X digital signal lags behind the start time of the main station M digital signal by TD1; the start time of the secondary station Y digital signal lags behind the start time of the main station M digital signal by TD2. The digital signal synthesis unit superimposes the received main station M digital signal, auxiliary station X digital signal and auxiliary station Y digital signal in the time domain to form a digital signal, and outputs it to the analog signal output unit. The analog signal output unit's digital-to-analog converter converts the digital signal from the digital signal synthesis unit into an analog signal. The signal attenuator of the analog signal output unit receives the signal attenuation control parameters output by the main control unit and attenuates the analog signal output by the digital-to-analog converter. The filter of the analog signal output unit filters the analog signal output by the signal attenuator before outputting it, finally obtaining the analog Roland C signal.

6. A readable storage medium, characterized in that, The readable storage medium stores a computer program that, when executed by a processor, implements the steps of the method as described in any one of claims 1 to 3.

7. A computer program product, characterized in that... It includes computer-executable instructions, which, when executed, are used to implement the method described in any one of claims 1 to 3.

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