CN112020830A - Telegraph text signal broadcasting method and device based on phase discontinuous R-CSK modulation - Google Patents

Telegraph text signal broadcasting method and device based on phase discontinuous R-CSK modulation Download PDF

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CN112020830A
CN112020830A CN201980026986.0A CN201980026986A CN112020830A CN 112020830 A CN112020830 A CN 112020830A CN 201980026986 A CN201980026986 A CN 201980026986A CN 112020830 A CN112020830 A CN 112020830A
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phase
message
spread spectrum
text
signal
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CN112020830B (en
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王盾
陈耀辉
李申阳
陈思源
李东俊
董启甲
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Space Star Technology Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H04L27/20—Modulator circuits; Transmitter circuits

Abstract

The invention discloses a method and a device for broadcasting telegraph text signals based on phase discontinuous R-CSK modulation, wherein the method comprises the following steps: modulating the basic message on the in-phase I branch, carrying out BPSK-DSSS direct sequence spread spectrum on the basic message, and constructing an in-phase I branch baseband signal; modulating the spread message on the orthogonal Q branch, performing phase non-continuous R-CSK-DSSS direct sequence spread spectrum on the spread message, and constructing an orthogonal Q branch baseband signal; when the spread message is modulated, determining a pseudorandom spread spectrum sequence for each symbol to be modulated, and keeping a fixed phase interval between two symbols to be modulated which are adjacent in value by adopting a cyclic shift mode on a basic pseudorandom spread spectrum sequence, wherein the fixed phase interval is at least larger than the chip phase of one pseudorandom spread spectrum sequence, namely the phase interval between the initial phases (taking the chip as a unit) of the pseudorandom spread spectrum sequences which are respectively corresponding to two modulation symbols which are adjacent in any value is a fixed value and has a difference of more than two chips; and carrying out IQ quadrature modulation on the basic message baseband signal of the in-phase I branch and the expanded message baseband signal of the quadrature Q branch to form a double-rate composite message signal and broadcast the double-rate composite message signal.

Description

Telegraph text signal broadcasting method and device based on phase discontinuous R-CSK modulation
Technical Field
The invention relates to a telegraph text signal broadcasting method and device based on phase discontinuous R-CSK modulation, and belongs to the technical field of communication and navigation signal design.
Background
In the design of modern communication and navigation systems, according to different application requirements, composite messages meeting different requirements are often required to be simultaneously broadcast in signals of the same frequency point. Such as: basic telegraph text is broadcasted according to a certain information rate to meet the requirements of the basic service performance or the open service performance of the system, and expanded telegraph text with the same or different information rates is broadcasted at the same time to meet the requirements of the additional service performance or the non-open service performance of the system. Because the expanded text message signal is not always completely disclosed, the system requires the designed composite text message signal, and can ensure that the basic text message user can perfectly receive the basic text message in the composite text message signal under the condition of not knowing whether the expanded text message signal exists or not.
For communication and navigation systems using direct sequence spread spectrum signal systems, the rate of broadcast messages is generally less than the reciprocal of the spreading code period. For example, the spreading code period of the GPS L1C/A code in the United states is 1ms, and the rate of the navigation message is 50 bps; the spread spectrum code period of the WAAS satellite navigation satellite-based augmentation system is 1ms, and the speed of the navigation message is 500 sps. If the broadcast rate of the telegraph text is increased, the code length of the spread code is shortened, or the polarity is overturned for a plurality of times in one code period, so that the relevant characteristics during signal receiving and tracking are reduced, and the signal receiving performance is damaged.
On the other hand, for the japanese QZSS quasi zenith satellite navigation system which also adopts a code shift keying modulation mode (CSK modulation mode for short) to broadcast messages, in order to provide necessary spreading code chips and code period time information for CSK demodulation, the QZSS system designs a special pilot channel which does not broadcast messages in an L6 signal which broadcasts CSK modulated messages, and the pilot channel signal and the message broadcast signals are combined in a TDM time division multiplexing mode and broadcast in the same carrier phase.
In order to reduce the CSK demodulation error rate, an intuitive solution is to repeat the spreading code sequence modulated by a given information symbol multiple times, increasing the signal propagation energy of a single modulation symbol. Meanwhile, in order to avoid the problem of information rate reduction caused by repeated broadcasting, the information bit number occupied by a single modulation symbol is increased proportionally, and the information rate is kept unchanged. For such a CSK modulation scheme, the present patent is referred to as a repetitive phase shift keying modulation scheme (R-CSK modulation scheme for short).
Generally, for convenience of engineering implementation, CSK/R-CSK modulation generally employs a phase sequence advance or phase sequence retard manner to assign different PRN (pseudo random noise) phases to modulation information symbols one by one, and maps the modulation information to a continuous phase region of the PRN code. When multipath interference exists, the CSK/R-CSK modulation signal adopting the phase configuration is easy to generate larger correlation peak side lobes at the output end of the signal demodulator, interference on CSK/R-CSK demodulation judgment is realized, and the CSK/R-CSK demodulation error rate is increased.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method and a device for controlling the broadcast of the telegraph signal based on the phase discontinuous R-CSK modulation, which can effectively meet the requirement of broadcasting various telegraph messages in the application of communication and navigation systems and have good multipath inhibition performance.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention provides a telegraph text signal broadcasting method based on phase discontinuous R-CSK modulation, which comprises the following steps:
modulating the basic message on the in-phase I branch, carrying out BPSK-DSSS direct sequence spread spectrum on the basic message, and constructing an in-phase I branch baseband signal;
modulating the spread message on the orthogonal Q branch, performing phase non-continuous R-CSK-DSSS direct sequence spread spectrum on the spread message, and constructing an orthogonal Q branch baseband signal; when the spread message is modulated, determining a pseudorandom spread spectrum sequence for each symbol to be modulated, and keeping a fixed phase interval between two symbols to be modulated which are adjacent in value by adopting a cyclic shift mode on a basic pseudorandom spread spectrum sequence, wherein the fixed phase interval is at least larger than the chip phase of one pseudorandom spread spectrum sequence, namely the phase interval between the initial phases (taking the chip as a unit) of the pseudorandom spread spectrum sequences which are respectively corresponding to two modulation symbols which are adjacent in any value is a fixed value and has a difference of more than two chips;
carrying out IQ quadrature modulation on a basic message baseband signal of an in-phase I branch and an expanded message baseband signal of a quadrature Q branch to obtain an intermediate frequency carrier signal, carrying out up-conversion processing on the intermediate frequency carrier signal to obtain a radio frequency carrier signal, and finally carrying out power amplification processing to form a double-rate composite message signal which is transmitted by a transmitting antenna.
As a preferred technical scheme of the invention: assuming that the phase interval is Z and any numerical value in the text to be modulated is i, the initial phase of the pseudorandom spreading sequence is PRN (i × Z); and i is 0 to M-1, M is the number of the telegraph text information symbols to be modulated, and Z is equal to or more than 2 chips and less than or equal to the number of chips corresponding to one pseudorandom spread spectrum sequence period.
As a preferred technical scheme of the invention: in the telegraph text signal broadcasting method based on the phase discontinuous R-CSK modulation, the in-phase I branch baseband signal is constructed according to the following method on the in-phase I branch:
channel coding is carried out on the basic text to obtain a coded bit stream DB(t)；
Generating basic text by the basic text spread spectrum code generator according to the basic text spread spectrum code period clock and the Chip clock provided by the time sequence generatorSpreading code CB(t) a bit stream D corresponding to the obtained elementary textB(t) carrying out BPSK-DSSS direct sequence spread spectrum modulation, and updating bit stream corresponding to basic text to CB(t)·DB(t)；
Power proportioning coefficient A based on preset basic telegraph textIPress SI(t)＝AI·CB(t)·DB(t) obtaining an in-phase I branch baseband signal SI(t)。
As a preferred technical scheme of the invention: in the telegraph text signal broadcasting method based on the phase discontinuous R-CSK modulation, the quadrature Q branch baseband signal is constructed on the quadrature Q branch according to the following method:
carrying out channel coding on the extension message to obtain a coded bit stream;
performing 1-fold operation on the corresponding bit stream after the expanded text coding according to the expanded text symbol clock provided by the time sequence generator>KRbit serial/parallel conversion is carried out to obtain parallel data streams; wherein each KRThe duration of bit parallel data, namely the length of symbol time is equal to N times of the cycle time of spreading codes of the extended text;
according to the spreading message spreading code period clock provided by the time sequence generator, generating a phase offset corresponding to the parallel data stream by the phase selection module according to a preset phase equal interval discontinuous mapping relation;
generating an extended message spread spectrum code by an extended message spread spectrum code generator according to a period clock of the extended message code, a Chip clock and a phase offset corresponding to a parallel data stream provided by a time sequence generator, repeating the extended message spread spectrum code for multiple times or zero times, namely, not repeating the phase and the like, and discontinuously configuring code shift keying modulation at equal intervals to obtain a modulated extended message spread spectrum code signal
Figure BDA0002732579640000031
And combining with a preset expanded message power ratio coefficient AQPush-button
Figure BDA0002732579640000041
Obtaining a pseudorandom spreading sequenceColumn SQ(t), i.e. quadrature Q branch baseband signal SQ(t) wherein the code phase of the pseudorandom spreading sequence is controlled by the spreading text, (a)I)2+(AQ)21. When the code shift keying modulation is not repeatedly performed on the basis of the spread text spread spectrum code at equal intervals, the modulation mode is the CSK modulation.
As a preferred technical scheme of the invention: the spread message symbol clock is an integral multiple of the spread message code period clock and is synchronous with the spread message code period clock.
The invention also provides a telegraph text signal broadcasting device based on phase discontinuous R-CSK modulation, which comprises:
the first modulation unit is used for modulating the basic message on the in-phase I branch, carrying out BPSK-DSSS direct sequence spread spectrum on the basic message and constructing an in-phase I branch baseband signal;
the second modulation unit is used for modulating the spread message on the orthogonal Q branch, performing phase non-continuous R-CSK-DSSS direct sequence spread spectrum on the spread message and constructing an orthogonal Q branch baseband signal; when the spread message is modulated, determining a pseudorandom spread spectrum sequence for each symbol to be modulated, and keeping a fixed phase interval between two symbols to be modulated which are adjacent in value by adopting a cyclic shift mode on a basic pseudorandom spread spectrum sequence, wherein the fixed phase interval is at least larger than the chip phase of one pseudorandom spread spectrum sequence, namely the phase interval between the initial phases (taking the chip as a unit) of the pseudorandom spread spectrum sequences which are respectively corresponding to two modulation symbols which are adjacent in any value is a fixed value and has a difference of more than two chips;
the carrier modulation unit is used for carrying out IQ quadrature modulation on a basic text baseband signal of the in-phase I branch and an extended text baseband signal of the quadrature Q branch to obtain an intermediate frequency carrier signal, and then carrying out up-conversion processing on the intermediate frequency carrier signal to obtain a radio frequency carrier signal;
and the sending unit is used for carrying out power amplification processing on the radio frequency carrier signal to form a double-rate composite telegraph text signal for broadcasting.
As a preferred technical scheme of the invention: assuming that the phase interval is Z and any numerical value in the text to be modulated is i, the initial phase of the pseudorandom spreading sequence is PRN (i × Z); and i is 0 to M-1, M is the number of the telegraph text information symbols to be modulated, and Z is equal to or more than 2 chips and less than or equal to the number of chips corresponding to one pseudorandom spread spectrum sequence period.
As a preferred technical solution of the present invention, in the teletext signal transmission apparatus based on phase discontinuous R-CSK modulation according to the embodiment of the present invention, the first modulation unit includes:
a coding subunit, configured to perform channel coding on the basic text to obtain a coded bit stream DB(t)；
A first spread spectrum modulation subunit for generating a basic text spread spectrum code C by the basic text spread spectrum code generator according to the basic text spread spectrum code period clock and the Chip clock provided by the time sequence generatorB(t) a bit stream D corresponding to the obtained elementary textB(t) carrying out BPSK-DSSS direct sequence spread spectrum modulation, and updating bit stream corresponding to basic text to CB(t)·DB(t)；
A baseband signal generating subunit for generating a power ratio coefficient A based on a preset basic messageIPress SI(t)＝AI·CB(t)·DB(t) obtaining an in-phase I branch baseband signal SI(t)。
As a preferred technical solution of the present invention, in the teletext signal transmission apparatus based on phase discontinuous R-CSK modulation according to the embodiment of the present invention, the second modulation unit includes:
the coding subunit is used for carrying out channel coding on the extended text to obtain a coded bit stream;
a serial/parallel conversion subunit for performing 1->KRbit serial/parallel conversion is carried out to obtain parallel data streams; wherein each KRThe duration of bit parallel data, namely the length of symbol time is equal to N times of the cycle time of spreading codes of the extended text;
the phase offset subunit is used for generating phase offset corresponding to the parallel data stream according to the extended message spread spectrum code periodic clock provided by the time sequence generator and the preset phase equal interval non-continuous mapping relation by the phase selection module;
a second spread spectrum modulation subunit, configured to generate an extended text spread spectrum code according to the extended text code period clock, the Chip clock, and the phase offset corresponding to the parallel data stream provided by the timing generator, and perform phase-equispaced non-continuous configuration code shift keying modulation based on the extended text spread spectrum code repeated multiple times or repeated zero times, i.e., not repeated, to obtain a modulated extended text spread spectrum code signal
Figure BDA0002732579640000051
And combining with a preset expanded message power ratio coefficient AQPush-button
Figure BDA0002732579640000052
Obtaining a pseudorandom spreading sequence SQ(t), i.e. quadrature Q branch baseband signal SQ(t) wherein the code phase of the pseudorandom spreading sequence is controlled by the spreading text, (a)I)2+(AQ)21. When the code shift keying modulation is not repeatedly performed on the basis of the spread text spread spectrum code at equal intervals, the modulation mode is the CSK modulation.
As a preferred technical solution of the present invention, the spread message symbol clock is an integer multiple of the spread message code period clock and is synchronized with the spread message code period clock.
Compared with the prior art, the telegraph text signal broadcasting method based on the phase discontinuous R-CSK modulation has the following excellent effects:
the invention relates to a telegraph text signal broadcasting method based on phase discontinuous R-CSK modulation, which adopts IQ two-path quadrature modulation, wherein a BPSK binary phase shift keying carrier modulation is adopted on an in-phase I branch, and a baseband signal is a basic telegraph text subjected to DSSS direct sequence spread spectrum; BPSK binary phase shift keying carrier modulation is adopted on the orthogonal Q branch, a baseband signal is a pseudo-random spread spectrum sequence which is subjected to repeated times or repeated zero times, namely, phase of non-repeated phase shift, is subjected to equidistant discontinuous configuration code shift keying modulation, and the code phase of the pseudo-random sequence is controlled by a broadcast spreading message; under the condition of the same spreading code length or period, a CSK modulation mode is adopted, and the telegraph text broadcasting rate higher than the DSSS direct sequence spread spectrum can be obtained; because the invention adopts code shift keying modulation of repeated phase shift for many times, compared with the conventional CSK modulation system, the demodulation performance of the receiver can be effectively improved under the condition of the same broadcast effective information rate; the CSK modulation information transmission rate can be improved, meanwhile, the signal power density of a receiving end is kept unchanged, and the software and hardware cost and the power consumption of the receiving end for demodulating CSK messages are prevented from being greatly increased; the invention assigns different PRN phases for modulation information symbols one by one, the phases are discontinuous and differ from each other by a fixed phase interval. When the delay time of the multipath interference signal is between two specified phases, the related peak sidelobe interference is not generated any more, thereby obtaining better multipath interference suppression performance. Because the invention adopts the phase equispaced discontinuous configuration R-CSK modulation, compared with the conventional phase continuous configuration CSK/R-CSK modulation system, the invention can effectively inhibit the multipath signal interference of the delay time between the appointed phases and improve the demodulation performance of the receiver; because the basic message and the expanded message are respectively placed on the orthogonal IQ branch, different power ratios can be configured for the basic message signal and the expanded message signal with different message rates, and the signal broadcasting efficiency is improved; because IQ branches are orthogonal, the phase difference of carriers is 90 degrees, and the influence of high-power expanded message signals on the receiving performance of basic message signals can be effectively avoided; BPSK signals are broadcast on the I branch, which not only can provide synchronous information required by CSK demodulation for the Q branch, but also can effectively broadcast basic telegraph text; because the basic text signal and the spread text signal are different in spread spectrum code and orthogonal in carrier, a system user only needing to receive the basic text does not need to consider the existence of the spread text, the design of the basic text receiver can be simplified, and the cost of the basic text receiver is reduced. The method is suitable for the fields of communication, navigation system design and the like.
Drawings
Fig. 1 is a block diagram of a broadcast method in a telegraph signal broadcast method based on phase discontinuous R-CSK modulation according to the present invention;
FIG. 2 is a timing relationship of components of an I-branch baseband signal;
FIG. 3 is a timing relationship of components of a Q branch baseband signal;
FIG. 4 is a constellation diagram of complex baseband signals;
FIG. 5 is a diagram of a basic text signal receiver;
FIG. 6 is a block diagram of a dual rate coherent receiver for telegraph text signals;
FIG. 7 is a diagram of a dual rate teletext signal non-coherent receiver arrangement;
FIG. 8 is a diagram of a comb filter configuration;
FIG. 9 is a schematic block diagram of multipath interference signal formation;
FIG. 10(a) is a graph of a phase mapping of conventional CSK/R-CSK modulation information to PRN code (phase sequence advance);
FIG. 10(b) is a graph of a conventional CSK/R-CSK modulation information to PRN code phase mapping (phase sequence lag);
FIG. 11 is a block diagram of a multipath signal impact mechanism analysis;
FIG. 12 is a diagram of a conventional CSK/R-CSK modulated multipath signal impact analysis;
FIG. 13 is a graph of theoretical ber for conventional CSK/R-CSK modulated information transmission in the presence of multipath interference signals;
FIG. 14 is a diagram illustrating a phase mapping relationship between phase discontinuity R-CSK modulation information and PRN code according to the present invention;
FIG. 15 is a diagram illustrating an analysis of the effects of phase discontinuous CSK/R-CSK modulated multi-path signals according to the present invention;
FIG. 16 is a diagram showing the comparison of simulation effect between the error rate of information transmission of phase-discontinuous R-CSK of the present invention and the error rate of conventional R-CSK information in a multipath scenario;
FIG. 17 is a schematic block diagram of a phase discontinuous R-CSK demodulation matched filter circuit according to the present invention;
fig. 18 is a schematic structural diagram of a textual signal broadcasting device based on phase discontinuous R-CSK modulation according to an embodiment of the present invention.
Detailed Description
The following description will explain embodiments of the present invention in further detail with reference to the accompanying drawings.
In practical application, as shown in fig. 1, the telegraph text signal broadcasting method based on the phase discontinuous R-CSK modulation of the invention adopts IQ two-path quadrature modulation to realize the broadcasting of a double-rate composite telegraph text signal.
Modulating the basic message on the in-phase I branch, carrying out BPSK-DSSS direct sequence spread spectrum on the basic message, and constructing an in-phase I branch baseband signal;
modulating the spread message on the orthogonal Q branch, performing phase non-continuous R-CSK-DSSS direct sequence spread spectrum on the spread message, and constructing an orthogonal Q branch baseband signal; when the spread message is modulated, a pseudorandom spread spectrum sequence is determined for each symbol to be modulated, a fixed phase interval is kept between two symbols to be modulated which are adjacent in numerical value by adopting a cyclic shift mode on a basic pseudorandom spread spectrum sequence, the fixed phase interval is at least larger than the chip phase of one pseudorandom spread spectrum sequence, namely, the phase interval between the initial phases (chip units) of the pseudorandom spread spectrum sequences which are respectively corresponding to two modulation symbols which are adjacent in any numerical value is a fixed value and has a difference of more than two chips;
the construction of the in-phase I branch baseband signal and the quadrature Q branch baseband signal is implemented by the following methods, respectively.
The specific method for constructing the in-phase I branch baseband signal is as follows:
channel coding is carried out on the basic text to obtain a coded bit stream DB(t)；
Generating a basic text spread spectrum code C by a basic text spread spectrum code generator according to a basic text spread spectrum code period clock and a Chip clock provided by a time sequence generatorB(t) a bit stream D corresponding to the obtained elementary textB(t) carrying out BPSK-DSSS direct sequence spread spectrum modulation, and updating bit stream corresponding to basic text to CB(t)·DB(t)；
As shown in FIG. 2, the time sequence relation of each component of the in-phase I branch baseband signal is given, and the basic text is providedThe time length of the clock is TBS1ms, the information of the basic text is formed into a rate R after block coding and channel codingB＝1/TBSBit stream D of 1kbps and with a value of plus or minus 1B(t) of (d). Basic text spreading code CB(T) code rate of 10.23MHz, basic text spread spectrum code period time length TBC1ms, and takes positive and negative 1. The correspondence between the text and the pseudo-random sequence is 1->“PRN(0)+”,-1->"PRN (0) -", where "PRN (0) +" denotes a positive-polarity pseudo-random sequence whose initial phase is 0, and "PRN (0) -" denotes a negative-polarity pseudo-random sequence whose initial phase is 0.
Power proportioning coefficient A based on preset basic telegraph textIPress SI(t)＝AI·CB(t)·DB(t) obtaining an in-phase I branch baseband signal SI(t)。
For the construction of the quadrature Q branch baseband signal, the specific method is as follows:
carrying out channel coding on the extension message to obtain a coded bit stream;
performing 1-fold operation on the corresponding bit stream after the expanded text coding according to the expanded text symbol clock provided by the time sequence generator>KRbit serial/parallel conversion is carried out to obtain parallel data streams; wherein each KRThe duration of bit parallel data, namely the length of symbol time is equal to N times of the cycle time of spreading codes of the extended text;
according to the spreading message spreading code periodic clock (referred to as spreading message code periodic clock in fig. 1) provided by the timing generator, the phase selection module generates the phase offset corresponding to the parallel data stream according to the preset phase equidistant non-continuous mapping relation. Here, let the spreading code period length of the spread text be L chips, and the information symbol KRThe number of bits and corresponding information symbols is
Figure BDA0002732579640000091
The phase interval of the configuration is Z, wherein Z is an integer greater than 1. The phase offset corresponding to the parallel data streams
Figure BDA0002732579640000092
Wherein i is 0,1, …, M-1, Z and M satisfy the constraint of M x Z ≦ L;
FIG. 3 shows the time sequence relationship of each component of the quadrature Q branch signal, extending the time length T of the telegraph symbol clockES,REqual to the spread-spectrum code period of the spread-textECBy a factor of N, using KRbit represents a symbol, extending the speed R of broadcast of the message informationE＝KR/TES,R. Without loss of generality, for convenience of subsequent explanation, the clock time length T of the spreading code period of the extended text is setECRepeating the phase shift 2 times (N2) for 1ms, and extending the telegraph symbol clock time length TES,R2ms, 6 bits is used to represent a symbol (K)R6), the message value range is 0-63, the phase interval Z is 64 chips, the corresponding phase offset is 64 i, i is 0,1, …,63, the message information broadcasting rate R is expandedE,R＝6/TES,RThe method comprises the steps of modulating 2 same pseudo-random sequences (namely, a 6-bit telegraph text (i) corresponds to N PRNs (i × Z) in the graph 3) repeatedly with the same phase at 3kbps, sequentially connecting the 2 pseudo-random sequences with the same phase offset to form a new modulation symbol, and completing phase-equal-interval discontinuous configuration code shift keying modulation of multiple repeated phase shifts. The correspondence between the 6-bit telegram (i) and the PRN (i × Z) in fig. 3 is only an embodiment of the present invention, and other correspondence relationships are also possible.
Generating an extended message spread spectrum code by an extended message spread spectrum code generator according to a period clock of the extended message code, a Chip clock and a phase offset corresponding to a parallel data stream provided by a time sequence generator, repeating the extended message spread spectrum code for multiple times or zero times, namely, not repeating the phase and the like, and discontinuously configuring code shift keying modulation at equal intervals to obtain a modulated extended message spread spectrum code signal
Figure BDA0002732579640000101
And combining with a preset expanded message power ratio coefficient AQPush-button
Figure BDA0002732579640000102
Obtaining a pseudorandom spreading sequence SQ(t), i.e. quadrature Q branch baseband signal SQ(t), wherein the code phase of the pseudorandom spreading sequence is controlled by the spreading text.
(AI)2+(AQ)2＝1
As shown in FIG. 4, the current setting is given
Figure BDA0002732579640000103
In this case, the constellation of the complex baseband signal is only an example, and the power matching relationship is not limited to this correspondence.
In the embodiment of the application, when the phase-equal-interval discontinuous configuration code shift keying modulation is not repeatedly performed based on the spread spectrum code of the spread message, the modulation mode is the CSK modulation.
In the present example of the invention, the phase interval Z is an integer greater than 1. Let the delay time of the multipath interference signal be taum(chip unit), the code phase of the multipath interference signal is
Figure BDA0002732579640000104
Wherein
Figure BDA0002732579640000105
And setting a code phase for the signal transmitting end according to a preset phase mapping relation. When the delay time of the multipath interference signal exceeds 1 spreading code chip and is less than Z-1 chips, the code phase of the multipath interference signal will not be the same as any preset code phase, and any relevant peak side lobe interference will not be generated at the demodulation output end of the receiver CSK/R-CSK signal. For example, when the chip time of the spreading code is 1 microsecond, the CSK/R-CSK modulation signal with the phase interval set to 64 is not influenced by the multipath interference signal with the delay path of 30-1890 meters. The larger the phase interval Z is, the wider the delay range of the multipath interference signal can be suppressed, and under the constraint that M x Z is less than or equal to L inequality, the maximum delay suppression range of the multipath interference signal can be obtained by equal-interval phase configuration.
In the present example of the present invention, in order to ensure that the receiving end obtains the same message demodulation performance, a higher signal transmission power is generally configured for the branch with a high message rate, without considering the channel coding difference between the basic message and the extended message.
The two branches use different spreading code sequences. When the message rates are different, the IQ branch can allocate different transmission powers, so that the basic message and the extended message received by the receiving end have the same receiving performance. The spread spectrum codes and messages of the two paths of the broadcast signal IQ are kept synchronous with each other.
For the in-phase I branch baseband signal SI(t) and quadrature Q branch baseband signal SQThe complex expression of (t) is as follows:
S(t)＝SI(t)+jSQ(t)
wherein j is an imaginary number.
Then, IQ quadrature modulation is carried out on the in-phase I branch baseband signal and the quadrature Q branch baseband signal to obtain an intermediate frequency carrier signal, up-conversion processing is carried out on the intermediate frequency carrier signal to obtain a radio frequency carrier signal, and finally, power amplification processing is carried out to form a double-rate composite telegraph text signal which is sent to a transmitting antenna for broadcasting.
The radio frequency transmission signal of the dual rate composite text signal is expressed herein as follows:
Figure BDA0002732579640000111
wherein, PsRepresenting the total power of the transmitted RF signal of the composite message, fcRepresenting the transmitted signal frequency.
In the telegraph text signal broadcasting method based on the phase discontinuous R-CSK modulation, the basic telegraph text and the expanded telegraph text are respectively placed on orthogonal IQ branches, the broadcasting speed of the expanded telegraph text is increased only by increasing the power of the expanded telegraph text signal, and the signal broadcasting efficiency is improved; IQ branches are orthogonal, and the phase difference of carriers is 90 degrees, so that the influence of high-power expanded message signals on the receiving performance of basic message signals can be effectively avoided; the BPSK signal broadcast on the I branch can not only provide the Q branch with the synchronous information required by CSK demodulation, but also effectively broadcast the basic telegraph text; the code shift keying modulation technology of phase equispaced non-continuous configuration is adopted, which is repeated for multiple times or zero times, namely, the phase is not repeatedly shifted, so that the information broadcasting rate can be effectively improved, the signal broadcasting efficiency is further improved, and the multipath interference signals are effectively inhibited.
Aiming at the designed telegraph text signal broadcasting method based on the phase non-continuous R-CSK modulation, the invention further designs a double-rate telegraph text signal receiving method, which comprises a basic telegraph text receiving method, an extended telegraph text coherent demodulation receiving method and an extended telegraph text noncoherent demodulation receiving method in the telegraph text signal based on the phase non-continuous R-CSK modulation; the basic text message receiving method, as shown in fig. 5, is specifically as follows:
a radio frequency carrier signal received by a receiver antenna is processed by a radio frequency Front-End (RF Front-End) to output a digital intermediate frequency signal; firstly, the digital intermediate frequency signal and a carrier frequency-mixing copied by a carrier ring output orthogonal IQ two-path baseband signal, and the IQ two-path baseband signal respectively carries out correlation operation with a basic message spread spectrum code copied by a basic message spread spectrum code generator to obtain IQ two-path correlation results; then IQ two-path correlation results are used as the input of a phase discrimination filtering module, the phase discrimination filtering module calculates a Carrier phase discrimination error and a Code phase discrimination error and filters the phase discrimination error, the filtering results are respectively used for adjusting Carrier NCO (Carrier NCO) and Code NCO (Code NCO), so that the Carrier output by the Carrier NCO is consistent with a receiving Carrier, a basic text spread spectrum Code copied by a basic text spread spectrum Code generator under the control of the Code NCO is consistent with the receiving basic text spread spectrum Code, and the Carrier and the spread spectrum Code in a receiving signal at the next moment are still thoroughly stripped in a tracking loop; and meanwhile, the correlation result output by the I branch correlator is judged by the basic text judgment module to output the basic text data bit.
A coherent demodulation and reception method for spreading a telegraph text signal based on phase discontinuous R-CSK modulation is shown in fig. 6, and specifically includes the following steps:
when demodulating the basic message, transmitting an extended message spread spectrum code periodic clock and a Chip clock which are obtained after synchronization and are synchronous with a received signal to an extended message spread spectrum code generator and a coherent matching filtering module, and transmitting an extended message symbol clock and the extended message spread spectrum code periodic clock to a comb filter; transmitting the Q branch baseband signal to a comb filter, and superposing N groups of pseudorandom sequence data in the same symbol into 1 group of pseudorandom sequence data by the comb filter;
the comb filter is shown in fig. 8: the comb filter delays the input data by N-1 times in sequence under the control of a periodic clock of the spread message spread spectrum code, and the periodic time T of the spread message spread spectrum code is delayed and expanded every timeECSecond, the N-1 time delay data and the input data are superposed and then sent to a data interception module; secondly, the data interception module intercepts input data stream under the control of an expanded message symbol clock and an expanded message spread spectrum code period clock, outputs data superposed for N times in the same symbol, and the data time length is the expanded message spread spectrum code period time TECAnd second. The intercepted data is sent to a coherent matched filtering module.
Then, the coherent matched filter module controls the received time length to be T under the control of the spread message symbol clock and the spread message spread spectrum code period clockECThe data block and the spread message spread spectrum code generated by the spread message spread spectrum code generator under the control of the spread message spread spectrum code period clock and the Chip clock are subjected to correlation matching calculation, correlation results are output to a correlation peak searching module, the phase of the local spread message spread spectrum code corresponding to the correlation peak is searched, and the phase is converted into bit data to be output;
and finally, the bit data output by the correlation peak searching module passes through a channel decoding module to obtain transmitted expanded text data.
A method for receiving and demodulating spread message noncoherent in message signal based on phase discontinuous R-CSK modulation is shown in fig. 7, and specifically includes the following steps:
when demodulating the basic message, transmitting an extended message spread spectrum code periodic clock and a Chip clock which are obtained after synchronization and are synchronous with a received signal to an extended message spread spectrum code generator and a non-coherent matched filtering module, and transmitting an extended message symbol clock and the extended message spread spectrum code periodic clock to a comb filter; the baseband IQ two-path signals are transmitted to a comb filter, and the comb filter superposes N groups of pseudo-random sequence data in the same symbol into 1 group of pseudo-random sequence data;
the comb filter is shown in fig. 8: the comb filter delays the input data by N-1 times in sequence under the control of a periodic clock of the spread message spread spectrum code, and the periodic time T of the spread message spread spectrum code is delayed and expanded every timeECSecond, the N-1 time delay data and the input data are superposed and then sent to a data interception module; secondly, the data interception module intercepts input data stream under the control of an expanded message symbol clock and an expanded message spread spectrum code period clock, outputs data superposed for N times in the same symbol, and the data time length is the expanded message spread spectrum code period time TECAnd second. The intercepted data is transmitted to a non-coherent matched filtering module.
Then, the incoherent matched filter module takes the received time length as T under the control of the spread message symbol clock and the spread message spread spectrum code period clockECThe data block and the spread message spread spectrum code generated by the spread message spread spectrum code generator under the control of the spread message spread spectrum code period clock and the Chip clock are subjected to correlation matching calculation, correlation results are output to a correlation peak searching module, the phase of the local spread message spread spectrum code corresponding to the correlation peak is searched, and the phase is converted into bit data to be output;
and finally, the bit data output by the correlation peak searching module passes through a channel decoding module to obtain transmitted expanded text data.
Fig. 9 shows a schematic block diagram of the formation of multipath interference signals, and in general, during the operation of a receiver, in addition to a direct signal transmitted by a satellite, a signal transmitted by the same satellite due to reflection from other objects (such as buildings, etc.), that is, a multipath signal, is received at the same time. Suppose the satellite signal transmission time t0Time t at which the receiver receives the direct signal1Should be equal to the signal transmission time t0Plus a signal propagation time delay tau1I.e. t1＝t0+τ1Time t at which the receiver receives a multipath signal2Equal to the signal transmission time t0Plus propagation time delay tau of the signal to the building2And building to receiver propagation time delay tau3I.e. t2＝t0+τ2+τ3. Obviously, the time delay for a multipath signal to reach the receiver is longer than the direct signal, and the multipath signal power is weaker than the direct signal power due to reflection loss, and spatial propagation loss.
In general, conventional CSK/R-CSK modulation employs phase sequence advance or phase sequence retard to assign different PRN phases to modulation information symbols one by one, and maps the modulation information to a continuous phase region of PRN codes, and fig. 10(a) and 10(b) take CSK (6) as an example, and respectively show phase sequence advance and phase sequence retard phase mapping diagrams.
When multipath interference exists, multipath signals with integral chip time delay easily cause larger correlation peak side lobes at the output end of the CSK/R-CSK signal demodulator, interfere the CSK/R-CSK demodulation judgment and increase the CSK/R-CSK demodulation error rate. Taking the mapping relation graph (phase sequence advance) of the conventional CSK/R-CSK modulation information and the PRN code phase shown in fig. 10(a) as an example, aiming at the CSK (6) modulation, the modulation information is 30, the multipath time delay is 5 chips, the multipath signal power is attenuated by 3dB compared with the direct signal, and the condition of 0 degree of phase difference with the direct signal carrier is simulated, fig. 11 shows an analysis graph of the multipath influence mechanism under the above simulation condition, from which it can be seen that, because the multipath signal delay is consistent with the mapping phase of the modulation information 25, a large correlation peak side lobe formed by the multipath signal exists at the demodulation output end of the CSK/R-CSK signal besides the correlation peak formed by the direct signal, which will seriously interfere the CSK/R-CSK demodulation decision.
The effect of multipath signals at different chip delays on different modulated information symbols may also vary. Also taking the phase mapping relation diagram (phase sequence advance) of the PRN code and the conventional CSK/R-CSK modulation information shown in fig. 10(a) as an example, for the CSK (6) modulation, when the modulation text is 0, since a large correlation peak side lobe formed by a multipath signal does not occur, the influence of the multipath signal is not generated, as shown in fig. 12 (a); when the modulation message is 30, when the time delay of the multipath signal is 1 to 30 chips, a large correlation peak side lobe formed by the multipath signal appears, so that the multipath signal is influenced by the multipath signal with the time delay of 1 to 30 chips, as shown in fig. 12 (b); when the modulation text is 63, when the time delay of the multipath signal is 1 to 63 chips, a large correlation peak side lobe formed by the multipath signal appears, so that the multipath signal is influenced by the multipath signal with the time delay of 1 to 63 chips, as shown in fig. 12 (c); as can be seen from fig. 12, the conventional CSK (6) modulated signal is affected by the multipath signal with the time delay of 1-63 chips, and when the time delay of the multipath signal is greater than 63 chips, since there is no mapping phase of the modulation information in the delay range, the correlation value interference caused by the multipath signal is not generated, so that the multipath signal will not be affected.
The influence of multipath interference on conventional CSK/R-CSK modulation can be more intuitively explained from the angle of demodulation error rate, theoretical calculation is carried out on the error rate performance of CSK/R-CSK when multipath interference signals exist or not, and related symbols and corresponding relations are agreed as follows:
when no multipath interference exists, the calculation formula of the coherent demodulation symbol error rate of the conventional CSK/R-CSK modulation is as follows:
Figure BDA0002732579640000151
wherein E iss/N0＝Eb/N0×K＝Eb/N0×log2M, K is the bit number of each symbol, and the system M is 2K。
The formula converted into the bit error rate of the information is as follows:
Figure BDA0002732579640000152
in CSK/R-CSK demodulation, due to the existence of integer chip delay multipath interference signal, when matching filtering is carried out, the multipath signal can form a larger correlation value output RMLet the maximum correlation peak RmaxThe ratio of (d) is mu, and the size of mu is affected by the carrier phase, the size of the multipath signal delay and the multipath signal power. Coherence of conventional CSK/R-CSK modulation in the presence of multipath interferenceThe demodulated symbol error rate calculation formula is as follows:
Figure BDA0002732579640000161
the formula converted into the bit error rate of the information is as follows:
Figure BDA0002732579640000162
FIG. 13 is a graph showing a theoretical ber curve for conventional CSK/R-CSK modulation in the presence of a multipath interference signal, where the curve "theoretical-conventional CSK/R-CSK-no multipath" is a coherent demodulation ber curve in the absence of a multipath signal; the theory-conventional CSK/R-CSK-with multipath is a coherent demodulation error rate curve in the presence of multipath signals with power 3dB less attenuated than a direct signal, delay time of an integer number of chips (within a phase mapping range), and phase difference of 0 degree (i.e., μ ═ 0.707) from a direct signal carrier. As is clear from fig. 13, the coherent demodulation error rate is significantly higher in the presence of multipath interference than in the absence of multipath interference.
Fig. 14 shows a phase mapping relationship between phase discontinuous R-CSK modulation information and PRN code according to one embodiment of the present invention. Taking CSK (6) modulation as an example, assuming that the phase interval Z is 64 and the information symbol i takes values of 0 to 63, the corresponding spreading code initial phase is PRN (i × Z).
In order to more intuitively embody the effectiveness of the phase discontinuous CSK/R-CSK modulation provided by the invention relative to the conventional CSK/R-CSK modulation, analysis is still carried out from two aspects of correlation peak side lobe and demodulation error rate.
Taking CSK (6) as an example, the phase discontinuity mode proposed by the present invention is adopted to perform simulation for the situation that the modulation information symbol is 30, the multipath time delay is 1-256 chips, the multipath signal power is 3dB less attenuated than the direct signal, and the phase difference with the direct signal carrier is 0 degree, and for the convenience of simulation, the equal-interval phase configuration with the phase interval Z equal to 64 is adopted here. The impact analysis of the phase discontinuous CSK/R-CSK modulated multipath signal proposed by the present invention is shown in fig. 15. It can be seen from the figure that when the multipath delay time is greater than or equal to 1 chip and less than or equal to 63 chips, because the mapping phase of the modulation information does not exist in the delay range, the correlation value interference caused by the multipath signal is not generated, and therefore, the multipath signal is not influenced in the range, and when the chip time of the spreading code is 1 microsecond, the delay time corresponds to the range of 30-1890 meters. When the multipath delay time is equal to or greater than 64 chips, although the multipath signal still suffers interference of correlation values, the multipath signal influence is dispersed only when the multipath delay time is an integral multiple of 64 chips of the phase interval Z, that is, only suffers the influence of the multipath signal with the integral number of chips of the phase interval Z. And with the increase of the time delay of the multipath signal, the signal power is gradually weakened, and the influence of the multipath signal with the time delay larger than 63 chips is very small, so the phase discontinuous CSK/R-CSK modulation of the invention can effectively inhibit the influence of the multipath interference signal.
The effectiveness of the proposed phase-discontinuous R-CSK modulation in suppressing multipath interference compared to conventional CSK/R-CSK modulation can be more intuitively illustrated from the viewpoint of demodulation error rate as well. For the convenience of simulation calculation and without loss of generality, R-CSK (6,2) is taken as an example, and simulation is performed for the case that equal-interval phase discontinuous configuration with a phase interval of Z-64 is adopted, the multipath delay time is 1 chip, the multipath signal power is attenuated by 3dB compared with a direct signal, and the phase difference between the multipath signal power and a direct signal carrier is 0 degree. The simulation effect comparison of the bit error rate of the phase discontinuous R-CSK information transmission of the invention and the bit error rate of the conventional R-CSK information under the multipath scene is shown in FIG. 16. It can be seen that under the condition of 1-chip multipath interference, the information transmission error rate of the phase discontinuous R-CSK of the invention is basically consistent with the theoretical curve and is obviously superior to the conventional R-CSK modulation.
In addition, fig. 17 shows a schematic block diagram of a demodulation matched filter circuit for phase discontinuous R-CSK modulation proposed by the present invention, and compared with conventional CSK/R-CSK modulation, the phase discontinuous R-CSK modulation proposed by the present invention hardly increases the signal demodulation operation cost.
Fig. 18 is a schematic structural diagram of a composition of a phase discontinuous R-CSK modulation-based telegraph signal broadcasting device according to an embodiment of the present invention, and as shown in fig. 18, the phase discontinuous R-CSK modulation-based telegraph signal broadcasting device according to the embodiment of the present invention includes:
the first modulation unit 180 is configured to modulate the basic message on the in-phase I branch, perform BPSK-DSSS direct sequence spread spectrum on the basic message, and construct an in-phase I branch baseband signal;
the second modulation unit 181 is configured to modulate the spread message on the quadrature Q branch, perform phase-discontinuous R-CSK-DSSS direct sequence spread spectrum on the spread message, and construct a quadrature Q branch baseband signal; when the spread message is modulated, a pseudorandom spread spectrum sequence is determined for each symbol to be modulated, a fixed phase interval is kept between two symbols to be modulated which are adjacent in numerical value by adopting a cyclic shift mode on a basic pseudorandom spread spectrum sequence, the fixed phase interval is at least larger than the chip phase of one pseudorandom spread spectrum sequence, namely, the phase interval between the initial phases (chip units) of the pseudorandom spread spectrum sequences which are respectively corresponding to two modulation symbols which are adjacent in any numerical value is a fixed value and has a difference of more than two chips;
a carrier modulation unit 182, configured to perform IQ quadrature modulation on the basic text baseband signal of the in-phase I branch and the extended text baseband signal of the quadrature Q branch to obtain an intermediate frequency carrier signal, and perform up-conversion processing on the intermediate frequency carrier signal to obtain a radio frequency carrier signal;
and the sending unit 183 is configured to perform power amplification processing on the radio frequency carrier signal to form a dual-rate composite text signal for broadcasting.
As a preferred technical scheme of the invention: assuming that the phase interval is Z and any numerical value in the text to be modulated is i, the initial phase of the pseudorandom spreading sequence is PRN (i × Z); and i is 0 to M-1, M is the number of the telegraph text information symbols to be modulated, and Z is equal to or more than 2 chips and less than or equal to the number of chips corresponding to one pseudorandom spread spectrum sequence period.
As a preferred technical solution of the present invention, in the teletext signal transmission apparatus based on phase discontinuous R-CSK modulation according to the embodiment of the present invention, the first modulation unit 180 includes:
a coding subunit, configured to perform channel coding on the basic text to obtain a coded bit stream DB(t)；
A first spread spectrum modulation subunit for generating a basic text spread spectrum code C by the basic text spread spectrum code generator according to the basic text spread spectrum code period clock and the Chip clock provided by the time sequence generatorB(t) a bit stream D corresponding to the obtained elementary textB(t) carrying out BPSK-DSSS direct sequence spread spectrum modulation, and updating bit stream corresponding to basic text to CB(t)·DB(t)；
A baseband signal generating subunit for generating a power ratio coefficient A based on a preset basic messageIPress SI(t)＝AI·CB(t)·DB(t) obtaining an in-phase I branch baseband signal SI(t)；
As a preferred technical solution of the present invention, in the teletext signal transmission apparatus based on phase discontinuous R-CSK modulation according to the embodiment of the present invention, the second modulation unit 181 includes:
the coding subunit is used for carrying out channel coding on the extended text to obtain a coded bit stream;
a serial/parallel conversion subunit for performing 1->KRbit serial/parallel conversion is carried out to obtain parallel data streams; wherein each KRThe duration of bit parallel data, namely the length of symbol time is equal to N times of the cycle time of spreading codes of the extended text;
the phase offset subunit is used for generating phase offset corresponding to the parallel data stream according to the extended message spread spectrum code periodic clock provided by the time sequence generator and the preset phase equal interval non-continuous mapping relation by the phase selection module;
a second spread spectrum modulation subunit for generating spread spectrum codes according to the spread spectrum code period clock provided by the time sequence generator, the Chip clock and the phase offset corresponding to the parallel data stream, and repeating the spread spectrum codes for multiple times or zero times based on the spread spectrum codes, i.e. not repeating the phaseThe code shift keying modulation is discontinuously configured at equal intervals to obtain a modulated spread text spread spectrum code signal
Figure BDA0002732579640000191
And combining with a preset expanded message power ratio coefficient AQPush-button
Figure BDA0002732579640000192
Obtaining a pseudorandom spreading sequence SQ(t), i.e. quadrature Q branch baseband signal SQ(t) wherein the code phase of the pseudorandom spreading sequence is controlled by the spreading text, (a)I)2+(AQ)2＝1。
As a preferred technical solution of the present invention, the spread message symbol clock is an integer multiple of the spread message code period clock and is synchronized with the spread message code period clock.
In the embodiment of the application, when the phase-equal-interval discontinuous configuration code shift keying modulation is not repeatedly performed based on the spread spectrum code of the spread message, the modulation mode is the CSK modulation.
Compared with the prior art, the telegraph text signal broadcasting method based on the phase discontinuous R-CSK modulation has the following excellent effects:
the invention relates to a telegraph text signal broadcasting method based on phase discontinuous R-CSK modulation, which adopts IQ two-path quadrature modulation, wherein a BPSK binary phase shift keying carrier modulation is adopted on an in-phase I branch, and a baseband signal is a basic telegraph text subjected to DSSS direct sequence spread spectrum; BPSK binary phase shift keying carrier modulation is adopted on the orthogonal Q branch, a baseband signal is a pseudo-random spread spectrum sequence which is subjected to repeated times or repeated zero times, namely, phase of non-repeated phase shift, is subjected to equidistant discontinuous configuration code shift keying modulation, and the code phase of the pseudo-random sequence is controlled by a broadcast spreading message; under the condition of the same spreading code length or period, a CSK modulation mode is adopted, and the telegraph text broadcasting rate higher than the DSSS direct sequence spread spectrum can be obtained; because the invention adopts code shift keying modulation of repeated phase shift for many times, compared with the conventional CSK modulation system, the demodulation performance of the receiver can be effectively improved under the condition of the same broadcast effective information rate; the CSK modulation information transmission rate can be improved, meanwhile, the signal power density of a receiving end is kept unchanged, and the software and hardware cost and the power consumption of the receiving end for demodulating CSK messages are prevented from being greatly increased; the invention assigns different PRN phases for modulation information symbols one by one, the phases are discontinuous and differ from each other by a fixed phase interval. When the delay time of the multipath interference signal is between two specified phases, the related peak sidelobe interference is not generated any more, thereby obtaining better multipath interference suppression performance; because the invention adopts the phase equispaced discontinuous configuration R-CSK modulation, compared with the conventional phase continuous configuration CSK/R-CSK modulation system, the invention can effectively inhibit the multipath signal interference of the delay time between the appointed phases and improve the demodulation performance of the receiver; because the basic message and the expanded message are respectively placed on the orthogonal IQ branch, different power ratios can be configured for the basic message signal and the expanded message signal with different message rates, and the signal broadcasting efficiency is improved; because IQ branches are orthogonal, the phase difference of carriers is 90 degrees, and the influence of high-power expanded message signals on the receiving performance of basic message signals can be effectively avoided; BPSK signals are broadcast on the I branch, which not only can provide synchronous information required by CSK demodulation for the Q branch, but also can effectively broadcast basic telegraph text; because the basic text signal and the spread text signal are different in spread spectrum code and orthogonal in carrier, a system user only needing to receive the basic text does not need to consider the existence of the spread text, the design of the basic text receiver can be simplified, and the cost of the basic text receiver is reduced. The method is suitable for the fields of communication, navigation system design and the like.
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

Claims (10)

1. A telegraph text signal broadcasting method based on phase discontinuous R-CSK modulation is characterized in that: the method comprises the following steps:
modulating the basic message on the in-phase I branch, carrying out BPSK-DSSS direct sequence spread spectrum on the basic message, and constructing an in-phase I branch baseband signal;
modulating the spread message on the orthogonal Q branch, performing phase non-continuous R-CSK-DSSS direct sequence spread spectrum on the spread message, and constructing an orthogonal Q branch baseband signal; when the spread message is modulated, a pseudorandom spread spectrum sequence is determined for each symbol to be modulated, a fixed phase interval is kept between two symbols to be modulated which are adjacent in numerical value by adopting a cyclic shift mode on a basic pseudorandom spread spectrum sequence, the fixed phase interval is at least larger than the chip phase of one pseudorandom spread spectrum sequence, namely, the phase interval between the initial phases of the pseudorandom spread spectrum sequences respectively corresponding to two modulation symbols which are adjacent in any numerical value is a fixed value, and the phase difference is more than two chips;
carrying out IQ quadrature modulation on a basic message baseband signal of an in-phase I branch and an expanded message baseband signal of a quadrature Q branch to obtain an intermediate frequency carrier signal, carrying out up-conversion processing on the intermediate frequency carrier signal to obtain a radio frequency carrier signal, and finally carrying out power amplification processing to form a double-rate composite message signal which is transmitted by a transmitting antenna.
2. The method of claim 1, wherein the method further comprises:
when the phase interval is Z and any numerical value in the text to be modulated is i, the initial phase of the pseudorandom spread spectrum sequence is PRN (i × Z); and i is 0 to M-1, M is the number of the telegraph text information symbols to be modulated, and Z is equal to or more than 2 chips and less than or equal to the number of chips corresponding to one pseudorandom spread spectrum sequence period.
3. Method for the signal dissemination of a telegraph text based on phase-discontinuous R-CSK modulation according to claim 1 or 2, characterized in that: the constructing of the in-phase I branch baseband signal comprises:
channel coding is carried out on the basic text to obtain a coded bit stream DB(t)；
According to the basic message spread spectrum code period clock and Chip clock provided by time sequence generatorThe spreading code generator generates a basic text spreading code CB(t) a bit stream D corresponding to the obtained elementary textB(t) carrying out BPSK-DSSS direct sequence spread spectrum modulation, and updating bit stream corresponding to basic text to CB(t)·DB(t)；
Power proportioning coefficient A based on preset basic telegraph textIPress SI(t)＝AI·CB(t)·DB(t) obtaining an in-phase I branch baseband signal SI(t)。
4. Method for the signal dissemination of a telegraph text based on phase-discontinuous R-CSK modulation according to claim 1 or 2, characterized in that: the constructing of the quadrature Q branch baseband signal includes:
carrying out channel coding on the extension message to obtain a coded bit stream;
performing 1-fold operation on the corresponding bit stream after the expanded text coding according to the expanded text symbol clock provided by the time sequence generator>KRbit serial/parallel conversion is carried out to obtain parallel data streams; wherein each KRThe duration of bit parallel data, namely the length of symbol time is equal to N times of the cycle time of spreading codes of the extended text;
according to the spreading message spreading code period clock provided by the time sequence generator, generating a phase offset corresponding to the parallel data stream by the phase selection module according to a preset phase equal interval discontinuous mapping relation;
generating an extended message spread spectrum code by an extended message spread spectrum code generator according to a period clock of the extended message code, a Chip clock and a phase offset corresponding to a parallel data stream provided by a time sequence generator, repeating the extended message spread spectrum code for multiple times or zero times, namely, not repeating the phase and the like, and discontinuously configuring code shift keying modulation at equal intervals to obtain a modulated extended message spread spectrum code signal
Figure FDA0002732579630000021
And combining with a preset expanded message power ratio coefficient AQPush-button
Figure FDA0002732579630000022
Obtaining a pseudorandom spreading sequence SQ(t), i.e. quadrature Q branch baseband signal SQ(t) wherein the code phase of the pseudorandom spreading sequence is controlled by the spreading text, (a)I)2+(AQ)2＝1。
5. Method for the signal dissemination of a telegraph text based on phase-discontinuous R-CSK modulation according to claim 1 or 2, characterized in that: the spread message symbol clock is an integral multiple of the spread message code period clock and is synchronous with the spread message code period clock.
6. A telegraph text signal broadcasting device based on phase discontinuous R-CSK modulation is characterized in that: the device comprises:
the first modulation unit is used for modulating the basic message on the in-phase I branch, carrying out BPSK-DSSS direct sequence spread spectrum on the basic message and constructing an in-phase I branch baseband signal;
the second modulation unit is used for modulating the spread message on the orthogonal Q branch, performing phase non-continuous R-CSK-DSSS direct sequence spread spectrum on the spread message and constructing an orthogonal Q branch baseband signal; when the spread message is modulated, a pseudorandom spread spectrum sequence is determined for each symbol to be modulated, a fixed phase interval is kept between two symbols to be modulated which are adjacent in numerical value by adopting a cyclic shift mode on a basic pseudorandom spread spectrum sequence, the fixed phase interval is at least larger than the chip phase of one pseudorandom spread spectrum sequence, namely, the phase interval between the initial phases of the pseudorandom spread spectrum sequences respectively corresponding to two modulation symbols which are adjacent in any numerical value is a fixed value, and the phase difference is more than two chips;
the carrier modulation unit is used for carrying out IQ quadrature modulation on a basic text baseband signal of the in-phase I branch and an extended text baseband signal of the quadrature Q branch to obtain an intermediate frequency carrier signal, and then carrying out up-conversion processing on the intermediate frequency carrier signal to obtain a radio frequency carrier signal;
and the sending unit is used for carrying out power amplification processing on the radio frequency carrier signal to form a double-rate composite telegraph text signal for broadcasting.
7. The apparatus according to claim 6, wherein said apparatus further comprises:
when the phase interval is Z and any numerical value in the text to be modulated is i, the initial phase of the pseudorandom spread spectrum sequence is PRN (i × Z); and i is 0 to M-1, M is the number of the telegraph text information symbols to be modulated, and Z is equal to or more than 2 chips and less than or equal to the number of chips corresponding to one pseudorandom spread spectrum sequence period.
8. The phase discontinuous R-CSK modulation based telegraph text signal broadcasting device according to claim 6 or 7, characterized in that: the first modulation unit includes:
a coding subunit, configured to perform channel coding on the basic text to obtain a coded bit stream DB(t)；
A first spread spectrum modulation subunit for generating a basic text spread spectrum code C by the basic text spread spectrum code generator according to the basic text spread spectrum code period clock and the Chip clock provided by the time sequence generatorB(t) a bit stream D corresponding to the obtained elementary textB(t) carrying out BPSK-DSSS direct sequence spread spectrum modulation, and updating bit stream corresponding to basic text to CB(t)·DB(t)；
A baseband signal generating subunit for generating a power ratio coefficient A based on a preset basic messageIPress SI(t)＝AI·CB(t)·DB(t) obtaining an in-phase I branch baseband signal SI(t)。
9. The phase discontinuous R-CSK modulation based telegraph text signal broadcasting device according to claim 6 or 7, characterized in that: the second modulation unit includes:
the coding subunit is used for carrying out channel coding on the extended text to obtain a coded bit stream;
a serial/parallel conversion subunit for performing a conversion according to the extended text symbols provided by the timing generatorA clock for performing 1->KRbit serial/parallel conversion is carried out to obtain parallel data streams; wherein each KRThe duration of bit parallel data, namely the length of symbol time is equal to N times of the cycle time of spreading codes of the extended text;
the phase offset subunit is used for generating phase offset corresponding to the parallel data stream according to the extended message spread spectrum code periodic clock provided by the time sequence generator and the preset phase equal interval non-continuous mapping relation by the phase selection module;
a second spread spectrum modulation subunit, configured to generate an extended text spread spectrum code according to the extended text code period clock, the Chip clock, and the phase offset corresponding to the parallel data stream provided by the timing generator, and perform phase-equispaced non-continuous configuration code shift keying modulation based on the extended text spread spectrum code repeated multiple times or repeated zero times, i.e., not repeated, to obtain a modulated extended text spread spectrum code signal
Figure FDA0002732579630000041
And combining with a preset expanded message power ratio coefficient AQPush-button
Figure FDA0002732579630000042
Obtaining a pseudorandom spreading sequence SQ(t), i.e. quadrature Q branch baseband signal SQ(t) wherein the code phase of the pseudorandom spreading sequence is controlled by the spreading text, (a)I)2+(AQ)2＝1。
10. The phase discontinuous R-CSK modulation based telegraph text signal broadcasting device according to claim 6 or 7, characterized in that: the spread message symbol clock is an integral multiple of the spread message code period clock and is synchronous with the spread message code period clock.
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