CN114966772A - Inbound baseband signal generation method and device of Beidou positioning system - Google Patents
Inbound baseband signal generation method and device of Beidou positioning system Download PDFInfo
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Abstract
The invention discloses an inbound baseband signal generation method and device of a Beidou positioning system. The method comprises the following steps: processing the input code frequency control word to generate a pseudo code synchronous signal; counting the pseudo code synchronizing signals to generate telegraph text symbol synchronizing signals; generating a transmitting pseudo code according to the pseudo code synchronizing signal; generating telegraph text symbols in different transmitting stages according to the telegraph text symbol synchronizing signal; and forming an inbound baseband signal of the Beidou positioning system according to the transmitted pseudo code and the textual sign XOR. The invention can meet the use requirements of different users and has certain use value.
Description
Technical Field
The invention relates to the technical field of satellite navigation signal processing, in particular to an inbound baseband signal generation method and device of a Beidou positioning system.
Background
The Beidou satellite navigation system is a satellite navigation system independently constructed and operated in China. The Beidou third satellite navigation system is formed by a constellation of 3 GEO satellites, 3 IGSO satellites and 24 MEO satellites. And in 7 and 31 months in 2020, the Beidou third satellite navigation system is comprehensively built along with the completion of networking and transmitting of 30 satellites.
The big dipper third system GEO satellite newly increases the signal of new system RDSS discrepancy in station, provides regional short message communication service for china and surrounding area user. The novel system RDSS inbound signal form of the Beidou No. three system is the pseudo code direct sequence spread spectrum, BPSK modulation and burst frame information structural form, which is the same as the Beidou No. two system. Each burst frame consists of three sections, namely a synchronization header, a service section and a data section, and each section is generated by spreading different PN codes. Different from the big dipper two, in the big dipper two satellite navigation system, service section and data section information all adopt convolutional coding, and in the new system RDSS inbound signal, the text of the data section adopts a more complicated Turbo coding mode of variable total length, block check and block coding, and the coding is more complicated.
Disclosure of Invention
The technical problem solved by the invention is as follows: the defects of the prior art are overcome, and the inbound baseband signal generation method and the inbound baseband signal generation device of the Beidou positioning system are provided.
The technical solution of the invention is as follows:
in a first aspect, an embodiment of the present invention provides a method for generating an inbound baseband signal of a beidou positioning system, including:
processing the input code frequency control word to generate a pseudo code synchronous signal;
counting the pseudo code synchronizing signals to generate telegraph text symbol synchronizing signals;
generating a transmitting pseudo code according to the pseudo code synchronizing signal;
generating telegraph text symbols in different transmitting stages according to the telegraph text symbol synchronizing signal;
and forming an inbound baseband signal of the Beidou positioning system according to the transmitted pseudo code and the textual sign XOR.
Optionally, the processing the input code frequency control word to generate a pseudo code synchronization signal includes:
accumulating a code NCO (digital oscillator) according to an input code frequency control word to obtain an accumulated amount of the code NCO;
and acquiring a negative-positive jump edge of the code NCO accumulation amount to generate the pseudo code synchronization signal.
Optionally, the counting the pseudo code synchronization signal to generate a text symbol synchronization signal includes:
when the frame mark is in a frame mark transmitting stage and the pseudo code synchronizing signal count is full, generating the telegraph text symbol synchronizing signal;
in a non-frame identification transmitting stage, the current transmitting state is a fourth gear transmitting state, and under the condition that the pseudo code synchronizing signal pulse count value is 126 and 254, the telegraph text symbol synchronizing signal is generated;
and in a non-frame identification transmitting stage, the current transmitting state is a non-fourth gear transmitting state, and when the pseudo code synchronizing signal pulse count is full, the telegraph text symbol synchronizing signal is generated.
Optionally, the generating a transmission pseudo code according to the pseudo code synchronization signal includes:
at the start position of a synchronization head, under the drive of the pseudo code synchronization signal, carrying out shift operation on a first shift register group to generate a first output sequence of the first shift register group;
at the beginning position of the data segment, under the drive of the pseudo code synchronizing signal, carrying out shift operation on a second shift register group to generate a second output sequence of the second shift register group;
in the stage of transmitting a synchronization head, a frame identifier and a service segment, the first output sequence is used as the transmitting pseudo code;
and in a data segment transmitting stage, taking an exclusive-or value of the first output sequence and the second output sequence as the transmitting pseudo code.
Optionally, the generating text symbols of different transmission phases according to the text symbol synchronization signal includes:
generating a transmitting stage indication signal according to the telegraph text symbol synchronization signal;
and generating text symbols of different transmission phases based on the transmission phase indication signal.
In a second aspect, an embodiment of the present invention provides an inbound baseband signal generating apparatus for a beidou positioning system, including:
the pseudo code synchronizing signal generating module is used for processing the input code frequency control word to generate a pseudo code synchronizing signal;
the message synchronization signal generation module is used for counting the pseudo code synchronization signals and generating message symbol synchronization signals;
the transmitting pseudo code generating module is used for generating transmitting pseudo codes according to the pseudo code synchronizing signals;
the message symbol generating module is used for generating message symbols in different transmitting stages according to the message symbol synchronizing signal;
and the inbound baseband signal generation module is used for forming an inbound baseband signal of the Beidou positioning system according to the exclusive OR of the transmitting pseudo code and the telegraph text symbols.
Optionally, the pseudo code synchronization signal generating module includes:
a code NCO accumulated amount obtaining unit, configured to accumulate a code NCO (digital oscillator) according to an input code frequency control word to obtain a code NCO accumulated amount;
and the pseudo code synchronizing signal generating unit is used for acquiring the negative-positive jumping edge of the code NCO accumulation amount and generating the pseudo code synchronizing signal.
Optionally, the text synchronization signal generating module includes:
the first synchronizing signal generating unit is used for generating the telegraph text symbol synchronizing signal when the frame identification transmitting stage is in and the pseudo code synchronizing signal count is full;
the second synchronizing signal generating unit is used for generating the telegraph sign synchronizing signal when the current transmitting state is a fourth gear transmitting state in a non-frame identification transmitting stage and the pulse counting value of the pseudo code synchronizing signal is 126 and 254;
and the third synchronizing signal generating unit is used for generating the telegraph text symbol synchronizing signal when the current transmission state is a non-fourth gear transmission state in a non-frame identification transmission stage and the pulse count of the pseudo code synchronizing signal is full.
Optionally, the transmitting pseudo code generating module includes:
the first output sequence generating unit is used for carrying out shift operation on a first shift register group under the driving of the pseudo code synchronizing signal to generate a first output sequence of the first shift register group;
a second output sequence generating unit, configured to perform a shift operation on a second shift register set at a start position of a data segment under the driving of the pseudo code synchronization signal, so as to generate a second output sequence of the second shift register set;
the first transmission pseudo code acquisition unit is used for taking the first output sequence as the transmission pseudo code in the transmission stage of the synchronization head, the frame identifier and the service segment;
and the second transmitting pseudo code acquisition unit is used for taking the exclusive or value of the first output sequence and the second output sequence as the transmitting pseudo code in a data segment transmitting stage.
Optionally, the textual symbol generation module includes:
the transmitting stage indication signal generating unit is used for generating a transmitting stage indication signal according to the message symbol synchronization signal;
and the message symbol generating unit is used for generating message symbols in different transmitting stages based on the transmitting stage indication signal.
Compared with the prior art, the invention has the advantages that:
according to the embodiment of the invention, only the service section message to be transmitted, the data section message to be transmitted and the internal interleaving coefficients of different groups are needed to be written into the corresponding RAM, and the device can generate the RDSS inbound baseband signal according to the inbound signal generation requirement and the configured gear. The device is simple to use, can be matched with gears, can meet the use requirements of different users, is already applied to the actual RDSS short message communication, and has certain use value.
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Fig. 1 is a flowchart illustrating steps of an inbound baseband signal generating method of a beidou positioning system according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an inbound baseband signal generation process according to an embodiment of the present invention;
FIG. 3 is a block diagram of a data segment packet 1/2Turbo code according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of an inbound baseband signal generating device of a beidou positioning system according to an embodiment of the present invention.
Detailed Description
Example one
Referring to fig. 1, a flowchart illustrating steps of a method for generating an inbound baseband signal of a beidou positioning system according to an embodiment of the present invention is shown, and as shown in fig. 1, the method may include the following steps:
step 101: and processing the input code frequency control word to generate a pseudo code synchronous signal.
The embodiment of the invention can generate the message information/symbol rate of four gears which can be matched with gears according to the use requirements of users with different transmitting power levels.
For this process, reference may be made to fig. 2.
First, an input code frequency control word may be processed to generate a pseudo code synchronization signal, which may be described in detail in conjunction with the following specific implementation.
In a specific implementation manner of the present invention, the step 101 may include:
substep a 1: according to the input code frequency control word, the code NCO (digital oscillator) is accumulated to obtain the accumulated amount of the code NCO.
In this embodiment, a code NCO (digital oscillator) may be accumulated according to an input code frequency control word to obtain a code NCO accumulated amount.
After the code NCO accumulation is obtained, sub-step a2 is performed.
Substep A2: and acquiring a negative-positive jumping edge of the accumulated code NCO amount to generate the pseudo code synchronizing signal.
After the code NCO accumulation is obtained, the pseudo code synchronization signal pulses can be counted to generate the telegraph symbol synchronization signal symb _ en.
After the pseudo code synchronization signal is generated, step 102 and step 103 are performed.
Step 102: and counting the pseudo code synchronizing signals to generate telegraph text symbol synchronizing signals.
After generating the pseudo code synchronization signal, the pseudo code synchronization signal may be counted to generate a text symbol synchronization signal, and in a specific implementation, corresponding operations may be performed according to different transmission phases to generate a text symbol synchronization signal, which may be described in detail in conjunction with the following specific implementation.
In another specific implementation manner of the present invention, the step 102 may include:
substep B1: and when the pseudo code synchronizing signal count is full in a frame identification transmitting stage, generating the telegraph text symbol synchronizing signal.
In this embodiment, when the frame identification transmission phase is in progress and the pseudo code synchronization signal count is full, the telegraph symbol synchronization signal may be generated, specifically, the following example is generated:
in the frame identification transmitting stage, the pulse counting range of the pseudo code synchronizing signal is 0-X-1, and X is 4.08M/2k is 2040.
Where 4.08MHz is the pseudo-code rate of RDSS transmissions and 2ksps is the frame identifier rate.
In the frame mark transmitting stage, when the pseudo code synchronizing signal pulse count is full, the telegraph symbol synchronizing signal pulse is generated.
Substep B2: and in a non-frame identification transmission phase, the current transmission state is a fourth gear transmission state, and the telegraph sign synchronization signal is generated under the condition that the pseudo code synchronization signal pulse count value is 126 and 254.
Substep B3: and in a non-frame identification transmitting stage, the current transmitting state is a non-fourth gear transmitting state, and the telegraph text symbol synchronizing signal is generated when the pseudo code synchronizing signal pulse count is full.
In the non-frame identification transmission phase, the current transmission state is the fourth gear transmission state, and in the case that the pseudo code synchronizing signal pulse count values are 126 and 254, the telegraph symbol synchronizing signal can be generated.
In the non-frame identification transmitting stage, the current transmitting state is a non-fourth gear transmitting state, and when the pseudo code synchronizing signal pulse count is full, the telegraph text symbol synchronizing signal can be generated.
Specifically, the generation process is exemplified as follows:
in other transmitting phases, the pulse count range of the pseudo code synchronous signal is 0-Y-1, and Y is 4.08M/symb _ rate.
Where 4.08MHz is the pseudo code rate of the RDSS transmission and symb _ rate is the inbound signal message symbol rate. The value of symb _ rate is related to the gear: in the first gear, symb _ rate is 4kbps, and corresponds to Y1020; in the second gear, symb _ rate is 8kbps, and corresponds to Y510; in the third gear, symb _ rate is 16kbps, and corresponding Y is 255; in the fourth gear, the symbol _ rate is 32kbps, which is more specific, and Y is still 255.
In other transmitting stage, if it is the fourth gear transmitting, the message symbol synchronizing signal pulse is generated when the pseudo code synchronizing signal pulse count value is 126 and 254. If not, the message symbol synchronizing signal pulse symb _ en is generated when the pseudo code synchronizing signal pulse count is full.
Step 103: and generating a transmitting pseudo code according to the pseudo code synchronizing signal.
After generating the pseudo code synchronization signal, the transmitting pseudo code may be generated according to the pseudo code synchronization signal, and specifically, the generation process of the transmitting pseudo code may be described in detail in conjunction with the following specific implementation manner.
In a specific implementation manner of the present invention, the step 103 may include:
substep C1: and at the start position of the synchronization head, under the drive of the pseudo code synchronization signal, carrying out shift operation on a first shift register group to generate a first output sequence of the first shift register group.
In the embodiment of the invention, after the pseudo code synchronizing signal is generated, at the start position of the synchronizing head, the first shift register group can be shifted under the driving of the pseudo code synchronizing signal to generate the first output sequence of the first shift register group.
Substep C2: and at the start position of the data segment, under the drive of the pseudo code synchronous signal, carrying out shift operation on a second shift register group to generate a second output sequence of the second shift register group.
After generating the pseudo code synchronizing signal, at the beginning position of the data segment, the second shift register group can be shifted under the driving of the pseudo code synchronizing signal to generate a second output sequence of the second shift register group.
After the first output sequence and the second output sequence are generated, sub-step C3 and sub-step C4 are performed.
Substep C3: and in the stages of synchronization head, frame identification and service segment transmission, the first output sequence is used as the transmission pseudo code.
After generating the first output sequence, the first output sequence may be used as a transmission pseudocode during the synchronization header, frame identification and service segment transmission phases.
Substep C4: and in a data segment transmitting stage, taking an exclusive OR value of the first output sequence and the second output sequence as the transmitting pseudo code.
After the first output sequence and the second output sequence are generated, an exclusive or value of the first output sequence and the second output sequence can be used as a transmission pseudo code in a data segment transmission stage.
The above-described process may be described in detail in connection with the following examples.
At the start position of the synchronization head, the initial phase and tap of the G1 shift register group are put into the corresponding register clock, and the shift register group G1 continuously performs shift operation under the drive of the pseudo code synchronization signal to generate an output sequence G1 of the G1 shift register group. At the beginning position of the data segment, the initial phase and tap of the G2 shift register group are put into the corresponding register clock, and the shift register group G2 continuously performs shift operation under the drive of the pseudo code synchronizing signal, so as to generate the output sequence G2 of the G2 shift register group.
And in the stages of synchronization head, frame identification and service segment transmission, selecting an output sequence g1 as a transmission pseudo code. During the data segment transmission phase, the exclusive or value of the output sequences g1 and g2 is selected as the transmission pseudo code.
Step 104: and generating the message symbols in different transmitting stages according to the message symbol synchronization signal.
After generating the message symbol synchronization signal, message symbols for different transmission phases may be generated from the message symbol synchronization signal. Specifically, the transmission phase indication signal may be generated from the message symbol synchronization signal, and then the message symbols of different transmission phases may be generated based on the transmission phase indication signal.
The process of generating the transmission phase indication signal can be described in detail in connection with the following examples.
(1) The RDSS transmission starts and immediately enters the sync header transmission phase tx _ sync. In the synchronous head transmitting phase, the telegraph symbol synchronous signal symb _ en is counted from 0, and after the counting reaches Z-1, the synchronous head transmitting phase is stopped, and the frame mark transmitting phase tx _ frame _ flag is entered.
The size of Z is gear dependent, and since the sync header is fixed to 9ms, Z is 9 symb _ rate, which is the incoming signal telegraph symbol rate at different gear.
(2) In the frame mark transmitting phase tx _ frame _ flag, the frame mark is fixed to 12 symbols, so the counting range of the telegraph text symbol synchronization signal is 0-11. After the count is full of 11, the traffic segment data transmission phase tx _ duty is entered.
(3) And in the traffic segment transmitting phase tx _ duty, counting the telegraph text symbol synchronizing signals from 0, stopping the traffic segment transmitting phase after counting to A-1, and entering a variable-length data segment transmitting phase tx _ data. And a-52 x 4-208, wherein 52 is the service segment fixed length, and 4 is the service segment 1/4 rate convolutional coded data length.
(4) And in the data segment transmitting phase tx _ data, counting the telegraph text symbol synchronizing signals from 0, stopping the data segment transmitting phase after B-1 is counted, and ending the whole RDSS transmitting process immediately. Since the data segment transmission length is variable and not fixed, and turbo coding with 1/2 rate is adopted, B is data _ len × 2, where data _ len is the length of the text to be transmitted of the data segment, and 2 is the turbo coding gain.
The generation of textual symbols for different transmission phases may be described by way of example as follows:
(1) and in the synchronous hair shooting stage, the telegraph text symbol is always 0.
(2) The frame identification is transmitted, the text symbol is 12symbol Walsh sequence, the Walsh sequence is related to the gear: the first gear is "011011010000", the second gear is "010001110101", the third gear is "010111000110", and the fourth gear is "010110110011".
(3) In the service segment transmitting stage, the telegraph text symbols are the telegraph text symbols after (4,1,7) convolutional coding of the 1/4 rate of the telegraph text information of the service segment to be transmitted. In the service section transmitting stage, the text symbol generation process is as follows:
sequentially reading the service segment telegraph text to be transmitted from the service segment telegraph text RAM to be transmitted, and obtaining the telegraph text symbol after (4,1,7) convolutional coding according to four input generating polynomials of the (4,1,7) convolutional coder. The length of the output sequence after encoding is 4 times of the length of the input sequence.
(4) And in the data segment transmitting stage, the message symbol is the message symbol after the message information of the data segment to be transmitted is subjected to grouping check and grouping coding. The block coding mode is turbo coding of 1/2 rate.
Step 105: and forming an inbound baseband signal of the Beidou positioning system according to the transmitted pseudo code and the textual sign XOR.
After the transmission pseudo code and the telegraph text symbol are generated through the steps, the inbound baseband signal of the Beidou positioning system can be formed according to the exclusive OR of the transmission pseudo code and the telegraph text symbol, and the generation process can be specifically as follows:
as shown in fig. 3, the Turbo encoded text symbols generation process for the data segment packet 1/2 is as follows:
(1) and carrying out grouping check and grouping coding on the data segment message according to the original message length of the data segment. Setting the original message length as Nbit, L as N to get integer 970, M as N to get surplus 970, grouping according to the values of M and L, wherein the grouping rule is as follows:
1) and if L is 0 and M is less than 970, inserting 24-bit CRC check codes when grouping, and performing Turbo coding according to the length of the grouping N +24 bits.
2) If L is 1 and M<970, when N is odd number, it can make Turbo coding by two groups, and the length of former group is
The latter group being of length
When N is even number, then according to the packet length
Turbo coding is performed in two groups.
3) If L is more than 1 and M is less than 970, the first L-1 group carries out Turbo coding according to each group of 997 bits, and the last group and the remainder bits carry out coding according to the coding format of 2).
4) If M is 0, namely N is a positive integer of 970, then 24-bit CRC check codes are directly inserted into each group during grouping, and Turbo coding is carried out according to the length of 970+ 24-bit grouping.
And writing the text data which is grouped and added with the 24-bit CRC code into a text RAM of a data section to be transmitted in sequence.
And writing the inner interleaving coefficients corresponding to the packet messages into the inner interleaving coefficient RAM of different packets. As can be seen from the grouping rule in step (1), there are at most three packet lengths: and if the length of the last group of packets is last _ len, the length of the 2 nd group of packets from the last is last _ len +1 or last _ len, and the lengths of other groups are standard groups and are fixed to be 994 bits. And writing the three groups of corresponding inner interleaving coefficients into the inner interleaving coefficient RAM of different groups according to the actual grouping situation.
And carrying out 1/2 rate Turbo coding on each grouped text symbol. The Turbo coding of 1/2 rate includes the following steps:
1) reading the text data of each group from the text RAM of the data segment to be transmitted, reading the corresponding inner interleaving coefficient from the inner interleaving coefficient RAM of the corresponding group, and carrying out inner interleaving processing on the grouped original text to obtain the grouped text symbols after the inner interleaving processing.
2) And sequentially inputting the grouped original text symbols into a recursive system convolution encoder 1 to obtain encoded data 1, and sequentially inputting the grouped text symbols subjected to internal interleaving treatment into a recursive system convolution encoder 2 to obtain encoded data 2.
3) And performing puncturing processing on the coded data 1 and the coded data 2 according to a puncturing rule to obtain punctured coded data.
4) And performing outer interleaving processing on the punctured coded data, wherein the size of an outer interleaver is M, 40 rows and N, 50 columns. After the information bits are encoded, they are written in rows and read out in columns.
In this embodiment, the 1/2Turbo coding module consists of 5 modules including an inner interleaver module, 2 convolutional encoder modules, an erasure module and an outer interleaver module.
In order to verify the correctness of the block coding of the data segment, RTL simulation verification is carried out on the data segment. In the simulation, the original message length is selected as a typical value of 2000 bits, and when the message length is subjected to grouping check according to a grouping rule, the message length is divided into three groups. The first group has the length of 970 bits, and after 24-bit CRC check codes are added, 994 bits are totally obtained, the 994 bits are subjected to 1/2-rate Turbo coding and tail coiling 12 bits, and the total of 2000 bits is obtained after coding. The length of the second group and the third group are both 515 bits, the second group and the third group are 539 bits after 24-bit CRC code is added, and the third group is 1090 bits after Turbo coding and tail adding. From the experimental results, when the original text length is 2000bit, the original text length is divided into three groups for Turbo coding. Intl _ len is the length of each packet (actual length/2).
Example two
Referring to fig. 4, a schematic structural diagram of an inbound baseband signal generating apparatus of a beidou positioning system according to an embodiment of the present invention is shown, and as shown in fig. 4, the apparatus may include the following modules:
a pseudo code synchronizing signal generating module 410, configured to process the input code frequency control word to generate a pseudo code synchronizing signal;
a message synchronization signal generation module 420, configured to count the pseudo code synchronization signal and generate a message symbol synchronization signal;
a transmission pseudo code generating module 430, configured to generate a transmission pseudo code according to the pseudo code synchronization signal;
the message symbol generating module 440 is configured to generate message symbols in different transmission stages according to the message symbol synchronization signal;
and an inbound baseband signal generating module 450, configured to form an inbound baseband signal of the beidou positioning system according to the xor of the transmission pseudo code and the text symbol.
Optionally, the pseudo code synchronization signal generating module includes:
a code NCO accumulated amount obtaining unit, configured to accumulate a code NCO (digital oscillator) according to an input code frequency control word to obtain a code NCO accumulated amount;
and the pseudo code synchronizing signal generating unit is used for acquiring the negative-positive jumping edge of the code NCO accumulation amount and generating the pseudo code synchronizing signal.
Optionally, the text synchronization signal generating module includes:
the first synchronizing signal generating unit is used for generating the telegraph text symbol synchronizing signal when the frame identification transmitting stage is in and the pseudo code synchronizing signal count is full;
the second synchronizing signal generating unit is used for generating the telegraph sign synchronizing signal when the current transmitting state is a fourth gear transmitting state in a non-frame identification transmitting stage and the pulse counting value of the pseudo code synchronizing signal is 126 and 254;
and the third synchronizing signal generating unit is used for generating the telegraph text symbol synchronizing signal when the current transmission state is a non-fourth gear transmission state in a non-frame identification transmission stage and the pulse count of the pseudo code synchronizing signal is full.
Optionally, the transmitting pseudo code generating module includes:
the first output sequence generating unit is used for carrying out shift operation on a first shift register group under the driving of the pseudo code synchronizing signal to generate a first output sequence of the first shift register group;
a second output sequence generating unit, configured to perform a shift operation on a second shift register set at a start position of a data segment under the driving of the pseudo code synchronization signal, so as to generate a second output sequence of the second shift register set;
the first transmitting pseudo code acquisition unit is used for taking the first output sequence as the transmitting pseudo code in the stages of synchronizing head, frame identification and service section transmission;
and the second transmitting pseudo code acquisition unit is used for taking the exclusive or value of the first output sequence and the second output sequence as the transmitting pseudo code in a data segment transmitting stage.
Optionally, the text symbol generation module includes:
the transmitting stage indication signal generating unit is used for generating a transmitting stage indication signal according to the message symbol synchronization signal;
and the message symbol generating unit is used for generating message symbols in different transmitting stages based on the transmitting stage indication signal.
The detailed description set forth herein may provide those skilled in the art with a more complete understanding of the present application, and is not intended to limit the present application in any way. Thus, it will be appreciated by those skilled in the art that modifications or equivalents may still be made to the present application; all technical solutions and modifications thereof which do not depart from the spirit and technical essence of the present application should be covered by the scope of protection of the present patent application.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Claims (10)
1. An inbound baseband signal generation method of a Beidou positioning system is characterized by comprising the following steps:
processing the input code frequency control word to generate a pseudo code synchronous signal;
counting the pseudo code synchronizing signals to generate telegraph text symbol synchronizing signals;
generating a transmitting pseudo code according to the pseudo code synchronizing signal;
generating telegraph text symbols in different transmitting stages according to the telegraph text symbol synchronizing signal;
and forming an inbound baseband signal of the Beidou positioning system according to the transmitted pseudo code and the textual sign XOR.
2. The method of claim 1, wherein processing the input code frequency control word to generate the pseudo code synchronization signal comprises:
accumulating the code NCO according to the input code frequency control word to obtain the accumulated amount of the code NCO;
and acquiring a negative-positive jump edge of the code NCO accumulation amount to generate the pseudo code synchronization signal.
3. The method of claim 1, wherein counting the pseudo-code synchronization signal to generate a textual symbol synchronization signal comprises:
when the frame mark is in a frame mark transmitting stage and the pseudo code synchronizing signal count is full, generating the telegraph text symbol synchronizing signal;
in a non-frame identification transmitting stage, the current transmitting state is a fourth gear transmitting state, and under the condition that the pulse count value of the pseudo code synchronizing signal is 126 and 254, the telegraph text symbol synchronizing signal is generated;
and in a non-frame identification transmitting stage, the current transmitting state is a non-fourth gear transmitting state, and the telegraph text symbol synchronizing signal is generated when the pseudo code synchronizing signal pulse count is full.
4. The method of claim 1, wherein generating a transmit pseudo code from the pseudo code synchronization signal comprises:
at the start position of a synchronization head, under the drive of the pseudo code synchronization signal, carrying out shift operation on a first shift register group to generate a first output sequence of the first shift register group;
at the beginning position of the data segment, under the drive of the pseudo code synchronizing signal, carrying out shift operation on a second shift register group to generate a second output sequence of the second shift register group;
in the stage of transmitting a synchronization head, a frame identifier and a service segment, the first output sequence is used as the transmitting pseudo code;
and in a data segment transmitting stage, taking an exclusive OR value of the first output sequence and the second output sequence as the transmitting pseudo code.
5. The method of claim 1, wherein generating the message symbols for different transmission phases based on the message symbol synchronization signal comprises:
generating a transmitting stage indication signal according to the telegraph text symbol synchronization signal;
and generating text symbols of different transmission phases based on the transmission phase indication signal.
6. The utility model provides a big dipper positioning system's inbound baseband signal generates device which characterized in that includes:
the pseudo code synchronizing signal generating module is used for processing the input code frequency control word to generate a pseudo code synchronizing signal;
the message synchronization signal generation module is used for counting the pseudo code synchronization signals and generating message symbol synchronization signals;
the transmitting pseudo code generating module is used for generating transmitting pseudo codes according to the pseudo code synchronizing signals;
the message symbol generating module is used for generating message symbols in different transmitting stages according to the message symbol synchronizing signal;
and the inbound baseband signal generation module is used for forming an inbound baseband signal of the Beidou positioning system according to the exclusive OR of the transmitting pseudo code and the telegraph text symbols.
7. The apparatus of claim 6, wherein the pseudo-code synchronization signal generation module comprises:
the code NCO accumulated amount acquisition unit is used for accumulating the code NCO according to the input code frequency control word to obtain the code NCO accumulated amount;
and the pseudo code synchronizing signal generating unit is used for acquiring the negative-positive jumping edge of the code NCO accumulation amount and generating the pseudo code synchronizing signal.
8. The apparatus of claim 6, wherein the text synchronization signal generating module comprises:
the first synchronizing signal generating unit is used for generating the telegraph text symbol synchronizing signal when the frame identification transmitting stage is in and the pseudo code synchronizing signal count is full;
the second synchronizing signal generating unit is used for generating the telegraph sign synchronizing signal when the current transmitting state is a fourth gear transmitting state in a non-frame identification transmitting stage and the pulse counting value of the pseudo code synchronizing signal is 126 and 254;
and the third synchronizing signal generating unit is used for generating the telegraph text symbol synchronizing signal when the current transmission state is a non-fourth gear transmission state in a non-frame identification transmission stage and the pulse count of the pseudo code synchronizing signal is full.
9. The apparatus of claim 6, wherein the transmit pseudo-code generation module comprises:
the first output sequence generating unit is used for carrying out shift operation on a first shift register group under the driving of the pseudo code synchronizing signal to generate a first output sequence of the first shift register group;
a second output sequence generating unit, configured to perform a shift operation on a second shift register set at a start position of a data segment under the driving of the pseudo code synchronization signal, so as to generate a second output sequence of the second shift register set;
the first transmission pseudo code acquisition unit is used for taking the first output sequence as the transmission pseudo code in the transmission stage of the synchronization head, the frame identifier and the service segment;
and the second transmitting pseudo code acquisition unit is used for taking the exclusive or value of the first output sequence and the second output sequence as the transmitting pseudo code in a data segment transmitting stage.
10. The apparatus of claim 6, wherein the textual symbol generation module comprises:
the transmitting stage indication signal generating unit is used for generating a transmitting stage indication signal according to the message symbol synchronization signal;
and the message symbol generating unit is used for generating message symbols in different transmitting stages based on the transmitting stage indication signal.
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