Loran C ninth pulse information demodulation method

Abstract

The invention belongs to the technical field of information demodulation. The invention provides a Loran C ninth pulse information demodulation method. According to the embodiment of the invention, the ninth pulse time delay of the Loran C pulse group signal can be divided into the segment time delay and the intra-segment time delay for measurement only by knowing the initial approximate bit of the Loran C pulse group signal, the Loran C pulse time delay does not need to be accurately measured, and ninth pulse information demodulation can be realized directly through the segment time delay identifier and the intra-segment time delay identifier. Moreover, the method obtains the segment time delay through the envelope peak position time difference, can effectively avoid the problem of fuzzy carrier period, and is high in segment time delay recognition precision. According to the method, phase coding identification is carried out in a phase discrimination mode, the identification speed is high, the accuracy rate is high, and phase inversion of a ninth pulse signal during demodulation can be eliminated. And the time delay in the ninth pulse modulation section of the Loran C pulse group signal is obtained by calculating the phase difference near the maximum peak values of the ninth pulse and the first pulse, so that the identification precision is high, and the realization is simple and convenient.

Description

Technical Field

[0001] The disclosed embodiments relate to the technical field of information demodulation, and in particular to a method for demodulating Loran C ninth pulse information. Background Art

[0002] The Loran-C system is a long-range land-based radio positioning, navigation and timing (PNT) system with the advantages of high transmission power, strong anti-interference ability, long signal range and stable signal phase. When the satellite navigation system is interfered with or unavailable, it can be an important supplement and backup for the satellite navigation system. my country's existing Loran-C systems include the BPL timing system and the "Changhe-2" navigation system. At the same time, my country's major scientific and technological infrastructure projects will plan to build three new Loran-C timing stations in western my country. After completion, they will basically achieve nationwide coverage of Loran-C signals with the existing system. At the same time, by building differential stations, the correction of Loran-C propagation delay can be realized to provide users with high-precision timing.

[0003] The ninth pulse information modulation mode is an information modulation mode added on the basis of the original Loran C signal system. It is mainly used to broadcast Loran timing or navigation differential information, thereby improving the timing and positioning accuracy of the user's Loran C receiver. The ninth pulse modulation is different from the existing Eurofix modulation mode, and the existing Eurofix demodulation method cannot be applied to the ninth pulse information demodulation. Usually, the delay between signals is calculated using the correlation peak position, but the starting position detection error is large, and only the approximate position of the pulse can be obtained, which cannot be used for the demodulation of the ninth pulse signal. The characteristics of the ninth pulse modulation are that the delay between segments is long, the delay difference between different segments has multiple carrier cycles, and the phase demodulation has the problem of multi-cycle identification. The intra-segment delay ranges from 0 to 8.75μs, the delay interval is divided more, and the phase encoding of different pulse group signals will cause the ninth pulse phase inversion, which brings difficulties to the demodulation of information. Summary of the invention

[0004] In order to avoid the shortcomings of the prior art, the present application provides a Loran C ninth pulse information demodulation method to solve the problem in the prior art that it cannot effectively meet the demodulation of the ninth pulse signal modulation information received in the Loran C timing and positioning receiver.

[0005] According to an embodiment of the present disclosure, a method for demodulating Loran C ninth pulse information is provided, the method comprising: Acquire a sine signal and a cosine signal, and respectively perform orthogonal demodulation on the sine signal and the cosine signal with a Loran C pulse group signal to obtain a first orthogonal demodulation signal and a second orthogonal demodulation signal; Processing the first orthogonal demodulation signal and the second orthogonal demodulation signal to obtain a Roland C pulse group signal envelope, and performing pulse peak position detection on the Roland C pulse group signal envelope to obtain a peak time of a first pulse signal, a peak time of a second pulse signal, and a peak time of a ninth pulse signal of the Roland C pulse group signal envelope; Calculate the time difference between the peak time of the first pulse signal and the peak time of the ninth pulse signal, and obtain the segment delay and the segment delay identifier according to the time difference; Obtaining a first pulse phase, a second pulse phase, and a ninth pulse phase according to the first orthogonal demodulation signal and the second orthogonal demodulation signal; Obtaining a first phase difference according to the first pulse phase and the second pulse phase, and performing phase coding identification on the phase difference to determine the type of phase coding of the Loran C pulse group signal, and obtaining a second phase difference according to the type of phase coding, the type of the receiving Loran C station, the first pulse phase and the ninth pulse phase; The second phase difference is corrected by using the segment delay identifier to obtain a corrected phase, and the corrected phase is converted into a quadrant to obtain a phase difference positive angle phase difference; Performing intra-segment delay identification judgment according to the phase difference forward angle phase difference and the segment delay identification to obtain the intra-segment delay identification, and obtaining 5-bit information of the ninth pulse modulation of all the Roland C pulse group signals according to the segment delay identification and the intra-segment delay identification; Decoset decoding is performed on all 5-bit information modulated by the ninth pulse to obtain all 5-bit coset decoded information, and error correction is performed on all 5-bit coset decoded information according to the RS decoding rule of the ninth pulse information debugging mode to obtain demodulated information.

[0006] Further, the steps of acquiring a sine signal and a cosine signal, and respectively performing orthogonal demodulation on the sine signal and the cosine signal with a Roland C pulse group signal to obtain a first orthogonal demodulation signal and a second orthogonal demodulation signal include: Acquire the sine signal and the cosine signal having the same frequency as the Loran C pulse group signal; Multiplying the cosine signal with the Loran C pulse group signal to obtain an I branch signal; Multiplying the sinusoidal signal with the Roland C pulse group signal to obtain a Q branch signal; The I branch signal and the Q branch signal are respectively passed through a low-pass filter to obtain the first orthogonal demodulation signal and the second orthogonal demodulation signal .

[0007] Further, the steps of processing the first orthogonal demodulation signal and the second orthogonal demodulation signal to obtain a Roland C pulse group signal envelope, and performing pulse peak position detection on the Roland C pulse group signal envelope to obtain a peak time of a first pulse signal, a peak time of a second pulse signal, and a peak time of a ninth pulse signal of the Roland C pulse group signal envelope include: The first orthogonal demodulation signal and the second quadrature demodulated signal Take the square and take the square root of the sum to get the Roland C pulse group signal envelope ; At the present moment arrive The peak time of the first pulse signal of the Roland C pulse group signal envelope is detected within the time range ; exist arrive The peak time of the second pulse signal of the Roland C pulse group signal envelope is detected within the time range ; exist arrive The peak time of the ninth pulse signal of the Roland C pulse group signal envelope is detected within the time range .

[0008] Further, the step of calculating the time difference between the peak time of the first pulse signal and the peak time of the ninth pulse signal, and obtaining the segment delay and the segment delay identifier according to the time difference includes: According to the peak time of the first pulse signal and the peak time of the ninth pulse signal Calculate the time difference : ; According to the time difference Get the delay of the segment and the segment delay identifier ;in, when When the time delay is ; when , the segment delay is marked as ; when , the segment delay is marked as ; when , the segment delay is marked as .

[0009] Further, the step of obtaining a first pulse phase, a second pulse phase and a ninth pulse phase according to the first orthogonal demodulation signal and the second orthogonal demodulation signal includes: Based on the first orthogonal demodulation signal and the second orthogonal demodulation signal , calculate the first orthogonal demodulation signal according to formula (1) and the second orthogonal demodulation signal The four-quadrant inverse tangent value of ; where formula (1) is: ; exist arrive within the time frame, Sort them and take the middle value as the first pulse phase ; exist arrive within the time frame, Sort them and take the middle value as the second pulse phase ; exist arrive within the time frame, Sort by the middle value and take it as the ninth pulse phase .

[0010] Further, the step of obtaining a first phase difference according to the first pulse phase and the second pulse phase, performing phase coding identification on the phase difference to determine the type of phase coding of the Loran C pulse group signal, and obtaining a second phase difference according to the type of phase coding, the type of the receiving Loran C station, the first pulse phase and the ninth pulse phase includes: According to the first pulse phase and the second pulse phase , and obtain the first phase difference ; The phase difference Perform phase coding identification to determine the type of the phase coding of the Loran C pulse group signal; wherein, when , then the phase encoding is complementary code; when or , then the phase encoding is the original code; When the receiving Loran C station is the master station and the phase encoding is the original code, the second phase difference is: ; When the receiving Loran C station is the master station and the phase encoding is a complementary code, the second phase difference is: ; When the receiving Loran C station is a secondary station and the phase encoding is the original code, the second phase difference is: ; When the receiving Loran C station is a secondary station and the phase encoding is a complementary code, the second phase difference is: .

[0011] Further, the step of correcting the second phase difference by using the segment delay identifier to obtain a corrected phase, and performing quadrant conversion on the corrected phase to obtain a phase difference positive angle phase difference includes: By the segment delay identification The second phase difference Correction is performed to obtain the corrected phase Among them, when When the phase difference is corrected ;when , correct the phase difference ;when , correct the phase difference ;when , correct the phase difference ; The corrected phase Perform quadrant conversion to obtain the phase difference positive angle phase difference ;in, like , then the phase difference is the positive angle phase difference ; like , then the phase difference is the positive angle phase difference .

[0012] Further, the step of determining the intra-segment delay mark according to the phase difference forward angle phase difference and the segment delay mark to obtain the intra-segment delay mark, and obtaining the 5-bit information of the ninth pulse modulation of all the Roland C pulse group signals according to the segment delay mark and the intra-segment delay mark includes: like , then the intra-segment delay is identified as: ; like , then the intra-segment delay is identified as: , where (*) indicates rounding; Based on the segment delay identifier and the intra-segment delay identifier, the 5-bit information of the ninth pulse modulation of all Loran C pulse group signals is calculated according to formula (2); wherein formula (2) is: , .

[0013] Further, the step of performing coset decoding on all 5-bit information modulated by the ninth pulse to obtain all 5-bit coset decoded information, and performing error correction check on all 5-bit coset decoded information according to the RS decoding rule of the ninth pulse information debugging mode to obtain demodulated information includes: The 24 groups of demodulated information Subtract the coset vectors in the order in which they are found =[0 1 2 3 4 5 6 78 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23], the calculation formula is: ; right Judge the positive and negative to get 24 groups of 5-bit coset decoding information ;in, like , then the 5-bit coset decoding information is ;like , then the 5-bit coset decoding information is .

[0014] Decode all the 5-bit coset information Perform error correction check according to the ninth pulse information debugging mode RS decoding rule; If the verification is successful, the demodulation is judged to be successful and the demodulation information is input; If the check fails, 24 groups of demodulated information are taken again according to the broadcasting order of the Loran C pulse group signal to perform RS error correction check until the check succeeds.

[0015] The technical solution provided by the embodiments of the present disclosure may have the following beneficial effects: In the embodiments of the present disclosure, through the above-mentioned Roland C ninth pulse information demodulation method, on the one hand, the method only needs to know the starting position of the Roland C pulse group signal, and can measure the Roland C ninth pulse delay into segment delay and intra-segment delay. There is no need to accurately measure the Roland C pulse delay, and the ninth pulse information demodulation can be directly realized through the segment delay mark and the intra-segment delay mark. And the method obtains the segment delay method through the envelope peak position time difference, which can effectively avoid the problem of carrier cycle ambiguity, and the segment delay recognition accuracy is high. On the other hand, the method uses a phase-locked method to perform phase coding recognition, which has a fast recognition speed and high accuracy, and can eliminate the phase inversion of the ninth pulse signal during demodulation. And the intra-segment delay of the Roland C ninth pulse modulation of this method is obtained by calculating the phase difference near the maximum peak of the ninth and first pulses, with high recognition accuracy and simple and convenient implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0017] Figure 1 A diagram showing the steps of a method for demodulating Loran C ninth pulse information in an exemplary embodiment of the present disclosure; Figure 2 A specific flow chart showing a method for demodulating the ninth pulse information of Roland C in an exemplary embodiment of the present disclosure; Figure 3 shows a demodulated Loran C pulse group signal in an exemplary embodiment of the present disclosure; Figure 4 1. shows a demodulated Loran C pulse group signal I branch orthogonal demodulation signal in an exemplary embodiment of the present disclosure; Figure 5 1. shows a demodulated Loran C pulse group signal Q branch orthogonal demodulation signal in an exemplary embodiment of the present disclosure; Figure 6 shows the demodulated Loran C pulse group signal envelope in an exemplary embodiment of the present disclosure; Figure 7 The calculation result of the four-quadrant inverse tangent of the demodulated Loran C pulse group signal in the exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0018] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0019] In addition, the accompanying drawings are only schematic illustrations of the embodiments of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0020] In the related technology, the main station of the Roland C system broadcasts 9 pulse signals in each pulse group signal repetition period (GRI), with an interval of 1ms between the first 8 pulse signals and a 2ms interval between the 8th and 9th pulse signals; the sub-station only transmits the first 8 pulses per GRI, with an interval of 1ms between the pulse signals. The phase encoding of each pulse group signal adopts the "two-phase two-cycle complementary" rule for phase encoding, where two-phase means that the initial phase of the signal carrier has "0" or " As shown in Table 1, the current Eurofix debugging method uses three-state pulse shift modulation, which is modulated in the 3rd to 8th pulses of each GRI. Each GRI modulates 1 ASCII code, and a frame of information includes 30 ASCII codes in total, requiring 30 GRIs to complete the modulation.

[0021] Table 1 Phase encoding

[0022] In order to meet the needs of differential information transmission, the ninth pulse modulation method is used to realize the modulation of differential information, providing users with differential information to realize Roland C high-precision timing. The ninth pulse modulation is to insert an additional pulse after the 8th ms of the start of the pulse group signal of the main and auxiliary stations, and its phase encoding is the same as the phase encoding of the 8th pulse. For the main station, the original code of the ninth pulse is "-" and the complement code is "+". For the auxiliary station, the original code of the ninth pulse is "+" and the complement code is "-".

[0023] The ninth pulse information modulation method is designed with a frame length of 120 bits. One frame requires 24 GRIs to complete information modulation. The differential information (45 bits) is encoded by RS to obtain 120 bits of encoded information (24 groups of 5 bits of information). The RS encoded information is coset encoded every 5 bits in the GRI order to eliminate the loop problem caused by RS encoding. Coset encoding is to add the coset vector to the 24 groups of 5 bits of information (modulo 32) after RS ​​encoding. The coset vector is: =[0 1 2 3 4 5 6 7 8 9 10 11 1213 14 15 16 17 18 19 20 21 22 23]. After the coset coding is completed, every 5 bits of modulation information is modulated onto the ninth pulse of a Loran C pulse group signal.

[0024] The ninth pulse modulation realizes information modulation by changing the transmission delay of the ninth pulse signal of the Loran C pulse group signal. The ninth pulse forms a total of 32 states of pulse position modulation to realize differential information broadcasting, of which 32 states can be represented by 5 bits, so a pulse inserted in a GRI can represent 5 bits of information. The 32 states are realized by changing the relative delay, and the modulation delay calculation formula is expressed as:

[0025] In the formula, mod(*) means the remainder; floor(*) means rounding down; The delay of the ninth pulse modulation, It is the decimal representation of 5-bit modulation information. When the integer multiple of 8 is taken, 4 groups of segment delays will be formed. The initial values ​​of the segment delays are 0μs, 50.625μs, 101.25μs and 151.875μs respectively. There are 8 intra-segment delays in each group of segment delays. The intra-segment delay interval is 1.25μs, which is calculated as the phase interval: .information The relationship with 32 kinds of delays is shown in Table 2.

[0026] Table 2 Correspondence between the ninth pulse modulation information and delay

[0027] This example embodiment provides a method for demodulating Loran C ninth pulse information. Figure 1 As shown in , the Loran C ninth pulse information demodulation method may include: step S101 to step S108.

[0028] Step S101: acquiring a sine signal and a cosine signal, and respectively performing orthogonal demodulation on the sine signal and the cosine signal with a Loran C pulse group signal to obtain a first orthogonal demodulation signal and a second orthogonal demodulation signal; Step S102: Processing the first orthogonal demodulation signal and the second orthogonal demodulation signal to obtain a Roland C pulse group signal envelope, and performing pulse peak position detection on the Roland C pulse group signal envelope to obtain a peak time of a first pulse signal, a peak time of a second pulse signal, and a peak time of a ninth pulse signal of the Roland C pulse group signal envelope; Step S103: Calculate the time difference between the peak time of the first pulse signal and the peak time of the ninth pulse signal, and obtain the segment delay and the segment delay identifier according to the time difference; Step S104: obtaining a first pulse phase, a second pulse phase and a ninth pulse phase according to the first orthogonal demodulation signal and the second orthogonal demodulation signal; Step S105: obtaining a first phase difference according to the first pulse phase and the second pulse phase, and performing phase coding identification on the phase difference to determine the type of phase coding of the Loran C pulse group signal, and obtaining a second phase difference according to the type of phase coding, the type of the receiving Loran C station, the first pulse phase and the ninth pulse phase; Step S106: using the segment delay identifier to correct the second phase difference to obtain a corrected phase, and performing quadrant conversion on the corrected phase to obtain a phase difference positive angle phase difference; Step S107: determining the intra-segment delay flag according to the phase difference forward angle phase difference and the segment delay flag to obtain the intra-segment delay flag, and obtaining 5-bit information of the ninth pulse modulation of all the Loran C pulse group signals according to the segment delay flag and the intra-segment delay flag; Step S108: De-coset-decode all 5-bit information modulated by the ninth pulse to obtain all 5-bit coset-decoded information, and perform error correction check on all 5-bit coset-decoded information according to the RS decoding rule of the ninth pulse information debugging mode to obtain demodulated information.

[0029] Through the above-mentioned Roland C ninth pulse information demodulation method, on the one hand, the method only needs to know the starting position of the Roland C pulse group signal, and can measure the Roland C ninth pulse delay into segment delay and intra-segment delay. There is no need to accurately measure the Roland C pulse delay, and the ninth pulse information demodulation can be directly realized through the segment delay mark and the intra-segment delay mark. And this method obtains the segment delay method by the time difference of the envelope peak position, which can effectively avoid the problem of carrier cycle ambiguity, and the segment delay recognition accuracy is high. On the other hand, this method uses the phase detection method for phase coding recognition, which has fast recognition speed and high accuracy, and can eliminate the phase reversal of the ninth pulse signal during demodulation. And the intra-segment delay of the Roland C ninth pulse modulation of this method is obtained by calculating the phase difference near the maximum peak of the ninth and first pulses, with high recognition accuracy and simple and convenient implementation.

[0030] Next, we will refer to Figures 1 to 7 The various steps of the above-mentioned Loran C ninth pulse information demodulation method in this exemplary embodiment are described in more detail.

[0031] In step S101, the ninth pulse modulation of the Roland C signal is to add a pulse for modulation to the existing Roland C signal pulse group signal. Therefore, before the ninth pulse demodulation, based on the existing Roland C pulse group signal filtering and pulse group signal capture, the starting approximate position of the Roland C pulse group signal is determined to be, and the unit is, and then the demodulation of the Roland C ninth pulse signal is completed through the following steps.

[0032] The local system continuously generates 100kHz sine and cosine signals with the same frequency as the Roland C signal, and multiplies the cosine signal with the Roland C pulse group signal to obtain the I branch signal, and multiplies the cosine with the Roland C pulse group signal to obtain the Q branch signal. The I and Q branch signals are respectively passed through low-pass filters to obtain the first orthogonal demodulation signal and the second quadrature demodulated signal .

[0033] In step S102, the pulse signal envelope is acquired.

[0034] For two-way orthogonal demodulation signal and Take the square root of the sum to get the Roland C pulse group signal envelope .

[0035] Pulse peak position detection.

[0036] Take N=500, then arrive The first Loran C pulse group signal envelope is detected within the time range of Peak time , the unit is .exist arrive The second Loran C pulse group signal envelope is detected within the time range Peak time , the unit is .exist arrive The ninth Loran C pulse group signal envelope is detected within the time range of Peak time , the unit is .

[0037] In step S103, the segment delay flag is determined.

[0038] The time difference between the first pulse and the ninth pulse signal is calculated as: , the unit is Through the time difference Get segment delay Segment delay indicator .when When the time delay is ;when , the segment delay is marked as ;when , the segment delay is marked as ;when , the segment delay is marked as ; In step S104, pulse phase calculation: calculate all and The four-quadrant inverse tangent value is calculated as , the unit is °. arrive within the time frame, Sort them and take the middle value as the first pulse phase , the unit is °. arrive within the time frame, Sort them and take the middle value as the second pulse phase , the unit is °. arrive within the time frame, Sort by the middle value and take it as the ninth pulse phase , unit is °.

[0039] In step S105, the phase difference between the second and first pulses is calculated.

[0040] Using the first pulse phase and the second pulse phase Calculate the phase difference , in degrees. If , then the phase difference ;if , then the phase difference .

[0041] Phase encoding identification.

[0042] The positive angle phase difference between the second pulse and the first pulse is used Phase encoding recognition is performed. , then the phase encoding of the pulse group signal is complementary code; when or , then the phase encoding of the pulse group signal is the original code.

[0043] The phase difference between the ninth and first pulses is calculated.

[0044] Using the first pulse phase and the ninth pulse phase Calculate the phase difference , in degrees. If the receiving Loran C station is the main station, the phase difference is calculated as follows: the pulse group signal phase encoding is the original code, and the calculation formula for the phase difference between the ninth and first pulses is ; The phase encoding of the pulse group signal is complementary code, and the calculation formula of the phase difference between the ninth and first pulses is If the receiving Loran C station is a secondary station, the phase difference between the ninth and first pulses is calculated as follows: the pulse group signal phase encoding is the original code, and the phase difference between the ninth and first pulses is calculated as follows: ; The phase encoding of the pulse group signal is complementary code, and the calculation formula of the phase difference between the ninth and first pulses is .

[0045] In step S106, the phase difference between the ninth pulse and the first pulse is corrected.

[0046] By segment delay identification The phase difference between the first pulse and the ninth pulse Correction is performed to obtain the corrected phase , the unit is °. When the phase difference is corrected ;when , correct the phase difference ;when , correct the phase difference ;when , correct the phase difference .

[0047] The phase difference is converted to the positive angle phase difference.

[0048] Correct the phase Convert quadrant to phase difference Positive angle phase difference , in degrees. If , then the phase difference is the positive angle phase difference ;if , then the phase difference is the positive angle phase difference .

[0049] In step S107, the intra-segment delay flag is determined.

[0050] Using phase difference to positive angle phase difference Intra-segment delay marking Calculate. If , the intra-segment delay is marked as; ;if , the intra-segment delay is marked as; Where (*) indicates rounding.

[0051] 5-bit information calculation. Use the segment delay mark and the intra-segment delay mark to calculate the 5-bit information of the ninth pulse modulation of a Loran C pulse group signal. . The calculation formula is , Each Roland C pulse group signal can be demodulated to obtain a 5-bit modulation information. Continuously demodulating the Roland C pulse group signal can obtain 24 groups of 5-bit ninth pulse demodulation information. .

[0052] In step S108, the 24 sets of information are de-coset decoded. Subtract the coset vectors in the order in which they are found =[0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23], the calculation formula is: .right Judge the positive and negative to get 24 groups of 5-bit coset decoding information :if , then the corresponding coset decoding information is ,if , then the corresponding coset decoding information is .

[0053] RS error correction check.

[0054] Decoding information for 24 cosets Perform error correction check according to the RS decoding rule of the ninth pulse information debugging mode. If the check is successful, the demodulation is judged to be successful and the demodulation information is input; if the check is unsuccessful, re-obtain 24 groups of demodulation information according to the broadcasting order of the Roland C pulse group signal for RS error correction check until the check is successful.

[0055] In a specific embodiment, Figure 2 As shown, the ninth pulse is demodulated for the implementation process of the method described in this application. In this embodiment, the Loran C signal is received as the main station, and the starting position of the Loran C pulse group signal is .

[0056] The demodulated Loran C pulse group signal of this embodiment is as follows: Figure 3 As shown in , the I branch signal is obtained by multiplying the cosine signal with the Roland C pulse signal, and the Q branch signal is obtained by multiplying the sine signal with the Roland C pulse signal. The I and Q branch signals are low-pass filtered through a Hamming window with an order of 512 and a cutoff frequency of 10kHz to obtain the I branch orthogonal demodulation signal ,like Figure 4 As shown; obtain the Q branch orthogonal demodulation signal ,like Figure 5 shown.

[0057] For quadrature demodulated signals and Take the square root of the sum to get the Roland C pulse signal envelope ,like Figure 6 shown.

[0058] exist arrive The maximum position of the first Loran C pulse envelope detected within the range is ;exist arrive The maximum position of the second Loran C pulse envelope detected within the range is ;exist arrive The maximum position of the ninth Loran C pulse envelope detected within the range is .

[0059] Calculate the maximum position difference between the ninth pulse and the first pulse envelope .because , the segment delay is marked as .

[0060] use and Calculates the inverse tangent of the four quadrants , inverse tangent calculation The calculation results are as follows Figure 7 As shown. arrive within the time frame, Sort them and take the middle value as the first pulse phase .exist arrive within the time frame, Sort them and take the middle value as the second pulse phase .exist arrive within the time frame, Sort by the middle value and take it as the ninth pulse phase .

[0061] Using the first pulse phase and the second pulse phase Calculate the phase difference .because , phase difference .because , then the phase encoding of the pulse group signal is complementary code.

[0062] Since the receiving Loran C station is the main station, and the phase encoding of the Loran C pulse group signal is complementary code, the calculation formula for the phase difference between the ninth and first pulses is: .

[0063] By segment delay identification The phase difference between the first pulse and the ninth pulse Correction is performed to obtain the corrected phase .because , so correct the phase difference ; Correct the phase Convert quadrant to phase difference Positive angle phase difference .because , then the phase difference is the positive angle phase difference .

[0064] Using phase difference to positive angle phase difference Intra-segment delay marking Calculate. Because , the intra-segment delay is marked as; .

[0065] The 5-bit information of the ninth pulse modulation of the Loran C pulse group signal is: .

[0066] According to the same method, each Loran C pulse group signal can be demodulated to obtain a 5-bit modulation information, and 24 groups of 5-bit ninth pulse demodulation information can be obtained by continuously demodulating 24 groups of Loran C pulse group signals.

[0067] 24 groups of demodulation information Subtract the coset vectors in the order in which they are found =[0 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 16 17 18 19 20 21 22 23], the calculation formula is: .right Judge the positive and negative to get 24 groups of 5-bit coset decoding information :if , then the corresponding coset decoding information is ,if , then the corresponding coset decoding information is Taking the demodulation result of the ninth pulse of the Loran C pulse group signal in this embodiment as an example, . ,therefore Continuously perform coset decoding on 24 groups of ninth pulse signals to obtain 24 groups of coset decoding information , i=1,2,…,23.

[0068] Finally, the 24 sets of co-set decoding information are error-checked according to the RS decoding rules of the ninth pulse information debugging mode: if the check is successful, the demodulation is judged to be successful and the demodulation information is input; if the check is unsuccessful, the 24 sets of demodulation information are re-obtained according to the broadcasting order of the Roland C pulse group signal for RS error correction check until the check is successful.

[0069] Through the above-mentioned Roland C ninth pulse information demodulation method, on the one hand, the method only needs to know the starting position of the Roland C pulse group signal, and can measure the Roland C ninth pulse delay into segment delay and intra-segment delay. There is no need to accurately measure the Roland C pulse delay, and the ninth pulse information demodulation can be directly realized through the segment delay mark and the intra-segment delay mark. And this method obtains the segment delay method by the time difference of the envelope peak position, which can effectively avoid the problem of carrier cycle ambiguity, and the segment delay recognition accuracy is high. On the other hand, this method uses the phase detection method for phase coding recognition, which has fast recognition speed and high accuracy, and can eliminate the phase reversal of the ninth pulse signal during demodulation. And the intra-segment delay of the Roland C ninth pulse modulation of this method is obtained by calculating the phase difference near the maximum peak of the ninth and first pulses, with high recognition accuracy and simple and convenient implementation.

[0070] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0071] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0072] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A method for demodulating Loran C ninth pulse information, characterized in that: The method includes: Acquire a sine signal and a cosine signal, and respectively perform orthogonal demodulation on the sine signal and the cosine signal with a Loran C pulse group signal to obtain a first orthogonal demodulation signal and a second orthogonal demodulation signal; Processing the first orthogonal demodulation signal and the second orthogonal demodulation signal to obtain a Roland C pulse group signal envelope, and performing pulse peak position detection on the Roland C pulse group signal envelope to obtain a peak time of a first pulse signal, a peak time of a second pulse signal, and a peak time of a ninth pulse signal of the Roland C pulse group signal envelope; Calculate the time difference between the peak time of the first pulse signal and the peak time of the ninth pulse signal, and obtain the segment delay and the segment delay identifier according to the time difference; Obtaining a first pulse phase, a second pulse phase, and a ninth pulse phase according to the first orthogonal demodulation signal and the second orthogonal demodulation signal; Obtaining a first phase difference according to the first pulse phase and the second pulse phase, and performing phase coding identification on the phase difference to determine the type of phase coding of the Loran C pulse group signal, and obtaining a second phase difference according to the type of phase coding, the type of the receiving Loran C station, the first pulse phase and the ninth pulse phase; The second phase difference is corrected by using the segment delay identifier to obtain a corrected phase, and the corrected phase is quadrant-converted to obtain a phase difference positive angle phase difference; Performing intra-segment delay identification judgment according to the phase difference forward angle phase difference and the segment delay identification to obtain the intra-segment delay identification, and obtaining 5-bit information of the ninth pulse modulation of all the Roland C pulse group signals according to the segment delay identification and the intra-segment delay identification; Decoset decoding is performed on all 5-bit information modulated by the ninth pulse to obtain all 5-bit coset decoded information, and error correction is performed on all 5-bit coset decoded information according to the RS decoding rule of the ninth pulse information debugging mode to obtain demodulated information.

2. The Loran C ninth pulse information demodulation method according to claim 1, characterized in that: The steps of acquiring a sine signal and a cosine signal, and respectively performing orthogonal demodulation on the sine signal and the cosine signal with a Roland C pulse group signal to obtain a first orthogonal demodulation signal and a second orthogonal demodulation signal include: Acquire the sine signal and the cosine signal having the same frequency as the Loran C pulse group signal; Multiplying the cosine signal with the Loran C pulse group signal to obtain an I branch signal; Multiplying the sinusoidal signal with the Roland C pulse group signal to obtain a Q branch signal; The I branch signal and the Q branch signal are respectively passed through a low-pass filter to obtain the first orthogonal demodulation signal and the second quadrature demodulated signal .

3. The Loran C ninth pulse information demodulation method according to claim 2, characterized in that: The steps of processing the first orthogonal demodulation signal and the second orthogonal demodulation signal to obtain a Roland C pulse group signal envelope, and performing pulse peak position detection on the Roland C pulse group signal envelope to obtain a peak time of a first pulse signal, a peak time of a second pulse signal, and a peak time of a ninth pulse signal of the Roland C pulse group signal envelope include: The first orthogonal demodulation signal and the second quadrature demodulated signal Take the square and take the square root of the sum to get the Roland C pulse group signal envelope ; At the present moment arrive The peak time of the first pulse signal of the Roland C pulse group signal envelope is detected within the time range ; exist arrive The peak time of the second pulse signal of the Roland C pulse group signal envelope is detected within the time range ; exist arrive The peak time of the ninth pulse signal of the Roland C pulse group signal envelope is detected within the time range .

4. The Loran C ninth pulse information demodulation method according to claim 3, characterized in that: The step of calculating the time difference between the peak time of the first pulse signal and the peak time of the ninth pulse signal, and obtaining the segment delay and the segment delay identifier according to the time difference includes: According to the peak time of the first pulse signal and the peak time of the ninth pulse signal Calculate the time difference : ; According to the time difference Get the delay of the segment and the segment delay identifier ;in, when When the time delay is ; when , the segment delay is marked as ; when , the segment delay is marked as ; when , the segment delay is marked as .

5. The Loran C ninth pulse information demodulation method according to claim 4, characterized in that: The step of obtaining a first pulse phase, a second pulse phase and a ninth pulse phase according to the first orthogonal demodulation signal and the second orthogonal demodulation signal comprises: Based on the first orthogonal demodulation signal and the second quadrature demodulated signal , calculate the first orthogonal demodulation signal according to formula (1) and the second quadrature demodulated signal The four-quadrant inverse tangent value of ; where formula (1) is: ; exist arrive within the time frame, Sort them and take the middle value as the first pulse phase ; exist arrive within the time frame, Sort them and take the middle value as the second pulse phase ; exist arrive within the time frame, Sort by the middle value and take it as the ninth pulse phase .

6. The Loran C ninth pulse information demodulation method according to claim 5, characterized in that: The steps of obtaining a first phase difference according to the first pulse phase and the second pulse phase, performing phase coding identification on the phase difference to determine the type of phase coding of the Loran C pulse group signal, and obtaining a second phase difference according to the type of phase coding, the type of the receiving Loran C station, the first pulse phase and the ninth pulse phase include: According to the first pulse phase and the second pulse phase , and obtain the first phase difference ; The phase difference Perform phase coding identification to determine the type of the phase coding of the Loran C pulse group signal; wherein, when , then the phase encoding is complementary code; when or , then the phase encoding is the original code; When the receiving Loran C station is the master station and the phase encoding is the original code, the second phase difference is: ; When the receiving Loran C station is the master station and the phase encoding is a complementary code, the second phase difference is: ; When the receiving Loran C station is a secondary station and the phase encoding is the original code, the second phase difference is: ; When the receiving Loran C station is a secondary station and the phase encoding is a complementary code, the second phase difference is: .

7. The Loran C ninth pulse information demodulation method according to claim 6, characterized in that: The step of correcting the second phase difference by using the segment delay identifier to obtain a corrected phase, and performing quadrant conversion on the corrected phase to obtain a phase difference positive angle phase difference includes: By the segment delay identification The second phase difference Correction is performed to obtain the corrected phase Among them, when When the phase difference is corrected ;when , correct the phase difference ;when , correct the phase difference ;when , correct the phase difference ; The corrected phase Perform quadrant conversion to obtain the phase difference positive angle phase difference ;in, like , then the phase difference is the positive angle phase difference ; like , then the phase difference is the positive angle phase difference .

8. The Loran C ninth pulse information demodulation method according to claim 7, characterized in that: The step of determining the intra-segment delay mark according to the phase difference forward angle phase difference and the segment delay mark to obtain the intra-segment delay mark, and obtaining 5-bit information of the ninth pulse modulation of all the Roland C pulse group signals according to the segment delay mark and the intra-segment delay mark, includes: like , then the intra-segment delay is identified as: ; like , then the intra-segment delay is identified as: , where (*) indicates rounding; Based on the segment delay identifier and the intra-segment delay identifier, the 5-bit information of the ninth pulse modulation of all Loran C pulse group signals is calculated according to formula (2); wherein formula (2) is: , .

9. The Loran C ninth pulse information demodulation method according to claim 8, characterized in that: The step of performing coset decoding on all 5-bit information modulated by the ninth pulse to obtain all 5-bit coset decoded information, and performing error correction check on all 5-bit coset decoded information according to the RS decoding rule of the ninth pulse information debugging mode to obtain demodulated information includes: The 24 groups of demodulated information Subtract the coset vectors in the order in which they are found =[0 1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 17 18 19 20 21 22 23], the calculation formula is: ; right Judge the positive and negative to get 24 groups of 5-bit coset decoding information ;in, like , then the 5-bit coset decoding information is ;like , then the 5-bit coset decoding information is . Decode information for all the 5-bit cosets Perform error correction check according to the ninth pulse information debugging mode RS decoding rule; If the verification is successful, the demodulation is judged to be successful and the demodulation information is input; If the check fails, 24 groups of demodulated information are taken again according to the broadcasting order of the Loran C pulse group signal to perform RS error correction check until the check succeeds.

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