CN117478471A - FSK and FM composite modulation-demodulation realization method - Google Patents
FSK and FM composite modulation-demodulation realization method Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/12—Modulator circuits; Transmitter circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B13/00—Transmission systems characterised by the medium used for transmission, not provided for in groups H04B3/00 - H04B11/00
- H04B13/02—Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J1/00—Frequency-division multiplex systems
- H04J1/02—Details
- H04J1/06—Arrangements for supplying the carrier waves ; Arrangements for supplying synchronisation signals
- H04J1/065—Synchronisation of carrier sources at the receiving station with the carrier source at the transmitting station
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/14—Demodulator circuits; Receiver circuits
- H04L27/144—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements
- H04L27/152—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements using controlled oscillators, e.g. PLL arrangements
- H04L27/1525—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements using controlled oscillators, e.g. PLL arrangements using quadrature demodulation
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- Y02D30/00—Reducing energy consumption in communication networks
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Abstract
The invention provides a method for realizing FSK and FM composite modulation and demodulation, which comprises the following steps of S101: acquiring user-specified data for parallel-to-serial conversion to form a code element signal; s102: the code element signal is subjected to FSK modulation to form a modulated signal S 1 (n); s103: audio signal and modulated signal S 1 (n) performing superposition and integral calculation; s104: determining unrecovered signal S Fm (n); s105: generating an in-phase component S I (n) and orthogonal component S Q (n); s106: obtaining a processed in-phase component I (n) and a processed quadrature component Q (n); s107: obtaining a recovery signal S S (n); s108: obtaining an FSK time domain signal; s109: obtain result B FSK (n); s110: restoring the user specified numberAccording to the above. The analog communication system is improved to have the capability of transmitting analog audio data and digital state data.
Description
Technical Field
The invention relates to the technical field of aviation sonar buoy application, in particular to an FSK and FM composite modulation-demodulation implementation method.
Background
The aviation sonobuoy is used for sending underwater target underwater sound detection data to water for receiving and processing, and the traditional sonobuoy system adopts an analog FM (frequency modulation) modulation and demodulation communication mode, so that only underwater audio data can be transmitted, and digital state data cannot be transmitted. With the continuous abundance of sonobuoy functions, digital information with a certain data volume needs to be transmitted, and a method is needed to realize simultaneous transmission of analog data and digital data, so that the aviation sonobuoy has the capability of simultaneously transmitting underwater audio data and self data state information.
Disclosure of Invention
In view of this, the implementation method of FSK and FM complex modulation and demodulation provided by the invention can improve the analog communication system, so that the analog communication system has the capability of transmitting analog audio data and digital state data at the same time.
A method for realizing FSK and FM complex modulation and demodulation adopts an analog FM modulation and demodulation communication mode to transmit digital state data, and the method comprises the following steps:
s101: acquiring user-specified data for parallel-to-serial conversion to form a code element signal; the user designated data are Beidou data or instruction data;
s102: the code element signal is subjected to FSK modulation to form a modulated signal S 1 (n)；
S103: acquiring an original audio signal to be transmitted, wherein the audio signal and a modulated signal S 1 (n) performing superposition and integral calculation;
s104: after integration, FM modulation is carried out and transmission is carried out, a demodulation end of communication end equipment carries out FM demodulation on the signals after FM modulation, and unrecovered signals S are determined Fm (n)；
S105: the unrecovered signal S Fm (n) multiplying the quadrature carrier wave generated by the digitally controllable oscillator to generate an in-phase component S I (n) and orthogonal component S Q (n)；
S106: the in-phase component S I (n) and orthogonal component S Q (n) performing low-pass filter signal processing to inhibit high-frequency components and obtain a processed in-phase component I (n) and a processed quadrature component Q (n);
S107：the processed in-phase component I (n) and the processed quadrature component Q (n) are subjected to arctangent differential processing to obtain a recovery signal S S (n)；
S108: the recovery signal S S (n) performing low-pass filtering and band-pass filtering processing to obtain FSK time domain signals;
s109: the FSK time domain signal carries out bit demodulation, low-pass filtering and sampling judgment to obtain a result B FKK (n)；
S110: results B FSK (n) using correlation of barker codes to find the beginning of the specified data, and splicing code elements to recover the user specified data.
Advantageous effects
The digital communication system is adopted, so that the requirement of transmitting digital information by the aviation sonobuoy can be met, but the platform is often limited by communication bandwidth, the frequency of an audio signal is generally required to be reduced by adopting the digital communication system, and the same communication distance is required to be increased by increasing the transmitting power; the analog communication system sonobuoy can exist for a long time in the future, so that the existing communication system has the capability of transmitting digital information and has practical significance. The analog communication system circuit has simple implementation form, is still largely used in engineering, and can realize the function of simultaneously transmitting analog signals and digital signals or single-transmission digital signals by simply improving the analog communication system circuit without adopting a complex circuit form for the communication system with the requirements of transmitting a small amount of digital control instructions and state information.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and other drawings may be obtained according to these drawings without inventive effort to a person of ordinary skill in the art.
Fig. 1 is a block diagram of frequency division multiplexed signal generation;
FIG. 2 is a block diagram of complex modulated signal generation;
fig. 3 is a block diagram of an FSK demodulation implementation.
Detailed Description
Embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
Other advantages and effects of the present disclosure will become readily apparent to those skilled in the art from the following disclosure, which describes embodiments of the present disclosure by way of specific examples. It will be apparent that the described embodiments are merely some, but not all embodiments of the present disclosure. The disclosure may be embodied or practiced in other different specific embodiments, and details within the subject specification may be modified or changed from various points of view and applications without departing from the spirit of the disclosure. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict. All other embodiments, which can be made by one of ordinary skill in the art without inventive effort, based on the embodiments in this disclosure are intended to be within the scope of this disclosure.
It is noted that various aspects of the embodiments are described below within the scope of the following claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the present disclosure, one skilled in the art will appreciate that one aspect described herein may be implemented independently of any other aspect, and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented and/or a method practiced using any number of the aspects set forth herein. In addition, such apparatus may be implemented and/or such methods practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.
It should also be noted that the illustrations provided in the following embodiments merely illustrate the basic concepts of the disclosure by way of illustration, and only the components related to the disclosure are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.
The whole idea is as follows:
1) As shown in fig. 1, the FSK digital symbol signal framing mode is a long 1 synchronization header, a barker synchronization header, and user data; coarse synchronization is carried out through a long 1 synchronization head during demodulation, fine synchronization is carried out through a Barker code synchronization head, and bit stream data is restored into user data;
2) As shown in fig. 2, the implementing method of FSK and FM composite modulation and demodulation carries out FSK modulation on a digital signal, generates an FSK analog signal, carries out band-pass filtering on the FSK signal, carries out low-pass filtering on an audio signal, carries out frequency division multiplexing on the FSK signal and the audio signal, and carries out FM modulation on the frequency division multiplexed signal;
3) As shown in fig. 3, when the demodulation end performs FM demodulation, an orthographic demodulation and differential approximation formula is adopted to convert arctangent solving into multiplication and addition processing, so as to reduce the operand of the demodulation algorithm and the requirement on a processor, and the method is specific:
the method adopts an analog FM modulation and demodulation communication mode to transmit digital state data, and comprises the following steps:
s101: acquiring user-specified data for parallel-to-serial conversion to form a code element signal; the user designated data are Beidou data or instruction data, and specifically:
firstly, user specified data are converted into bit data, then the bit data are packaged, and a long 1 synchronization head and a barker code synchronization head are added to form a code element signal, wherein the long 1 synchronization head is used for coarse synchronization of a demodulation end, and the barker code synchronization head is used for fine synchronization of the demodulation end.
S102: FSK modulating the code element signal to form a modulated signal S 1 (n) wherein:
order the
Then
S 1 (n) is expressed as:
wherein f c And f 0 A, according to the matched coefficient of the user communication rate k Is a symbol signal, T b For the symbol period of time,is the initial phase; k. n is a natural number.
S103: acquiring an original audio signal to be transmitted, the audio signal and a modulated signal S 1 (n) performing superposition and integral calculation, specifically: the audio signal is an FSK signal comprising:
1) Audio signal and modulated signal S 1 (n) after superposition, expressed as: s is S 0 (n)＝S 1 (n)+S 2 (n)，
Wherein S is 1 (n) is FSK signal, S 2 (n) is an audio signal;
for S 0 (n) performing integral summation expressed as:
wherein Fs is the sampling rate, specifically 2 times f c The above;
2) Integrating and summing the signals subjected to FM modulation to S Fm (n) is represented by the formula,
wherein: freqdev is the modulation frequency offset, F c Freqdev passes through soft for the final radio frequency modulation frequencyThe component or hardware performs the control implementation.
Compared with the traditional method, the method has the advantages that the digital modulation signal and the original analog signal are combined, so that a compact implementation mode is provided for the analog buoy to be capable of transmitting digital data.
S104: FM modulation is carried out after integration and S is transmitted Fm (n) the demodulation end of the communication end device firstly carries out FM demodulation on the FM modulated signal to determine an unrecovered signal S Fm (n), specifically:
the communication terminal equipment, for example, a docking equipment or a remote receiving equipment which is in communication docking with a user, firstly carries out FM demodulation on the signal by a demodulation terminal of the communication terminal equipment after receiving the signal, and the received FM signal has the following expression after sampling: unrecovered signal S Fm (n) the expression:
s105: unrecovered signal S Fm (n) multiplying the quadrature carrier wave generated by the digitally controllable oscillator to generate an in-phase component S I (n) and orthogonal component S Q (n), specifically:
unrecovered signal S Fm (n) multiplying the quadrature carrier generated by the NCO, and omittingAnd F c Generates an in-phase component S I (n) and orthogonal component S Q (n), wherein,
s106: in-phase component S I (n) and orthogonal component S Q (n) Low pass filteringWave device signal processing, which is to restrain high frequency component to obtain processed in-phase component I (n) and processed quadrature component Q (n), concretely:
in-phase component S I (n) and orthogonal component S Q (n) processing the signal by a low-pass filter to suppress the high-frequency component and obtain an in-phase component I (n) and a quadrature component Q (n), wherein,
s107: the processed in-phase component I (n) and the processed quadrature component Q (n) are subjected to arctangent differential processing to obtain a recovery signal Ss (n), specifically:
the arctangent signal is subjected to differential approximation processing to recover the original signal, with the purpose of: the calculation amount of the demodulation algorithm is reduced, the inverse tangent differential processing is simplified into four operations through differential approximation processing, a complex hardware processor is not needed, and the calculation process is as follows:
a further conversion is made available which,
s108: the recovery signal Ss (n) is subjected to low-pass filtering and band-pass filtering processing to obtain an FSK time domain signal, and the method is specific:
performing low-pass filtering on Ss (n), wherein the low-pass filtering cutoff frequency is the upper limit of the audio frequency of the user, and demodulating an audio signal;
performing band-pass filtering on Ss (n), and performing band-pass filtering on the center frequency f c And obtaining the FSK time domain signal by frequency offset twice the bandwidth.
S109: performing bit demodulation, low-pass filtering and sampling judgment on the FSK time domain signal to obtain a result B FSK (n), specifically:
bit demodulation is firstly carried out on the FSK time domain signal, and the FSK signal time domain S FSK The expression (t) is:
S FSK (t)＝S 1 (t)cosω 1 t+S 2 (t)cosω 2 t, wherein S 1 (t)、S 2 (t) symbol data, ω being a reception frequency, t being time; a n g is a gate function;
in demodulation, for S FSK (t) multiplying cos ω with carrier wave respectively 1 t、cosω 2 t, obtaining an upper sideband signal S up (t)，
Then low-pass filtering is carried out to obtain a lower sideband signal S down (t)，
S up (t)＝S 1 (t)
S down (t)＝S 2 (t)；
Sampling and judging to obtain result B FSK (n)
When a is n Andis 1 or 0,1 represents S up (t) is greater than S dowm (t), 0 represents S up (t) is less than S dowm (t), at any time S up (t) and S dowm (t) size relationship, S in S102 is recovered by sampling judgment method 1 A of (n) k The represented symbol.
S110: results B FSK And (n) utilizing the correlation of the barker code to find the beginning of the appointed data, splicing the code elements to recover the user appointed data, for example, utilizing the correlation of the barker code to find the beginning of the appointed data, splicing the code elements to recover the user data (the receiving end equipment recovers the digital data sent by the transmitting end).
The invention enables the sonobuoy system adopting the analog communication system to simultaneously transmit the analog audio data and the digital state data, and improves the communication capacity of the sonobuoy system adopting the analog communication system.
The foregoing is merely specific embodiments of the disclosure, but the protection scope of the disclosure is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the disclosure are intended to be covered by the protection scope of the disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.
Claims (10)
1. The method for realizing FSK and FM composite modulation and demodulation adopts an analog FM modulation and demodulation communication mode to transmit digital state data, and is characterized by comprising the following steps:
s101: acquiring user-specified data for parallel-to-serial conversion to form a code element signal; the user designated data are Beidou data or instruction data;
s102: the code element signal is subjected to FSK modulation to form a modulated signal S 1 (n)；
S103: acquiring an original audio signal to be transmitted, wherein the audio signal and a modulated signalS 1 (n) performing superposition and integral calculation;
s104: after integration, FM modulation is carried out and transmission is carried out, a demodulation end of communication end equipment carries out FM demodulation on the signals after FM modulation, and unrecovered signals S are determined Fm (n)；
S105: the unrecovered signal S Fm (n) multiplying the quadrature carrier generated by the digitally controllable oscillator to generate an in-phase component S I (n) and orthogonal component S Q (n)；
S106: the in-phase component S I (n) and orthogonal component S Q (n) performing low-pass filter signal processing to inhibit high-frequency components and obtain a processed in-phase component I (n) and a processed quadrature component Q (n);
s107: the processed in-phase component I (n) and the processed quadrature component Q (n) are subjected to arctangent differential processing to obtain a recovery signal S S (n)；
S108: the recovery signal S S (n) performing low-pass filtering and band-pass filtering processing to obtain FSK time domain signals;
s109: the FSK time domain signal carries out bit demodulation, low-pass filtering and sampling judgment to obtain a result B FSK (n)；
S110: results B FSK (n) using correlation of barker codes to find the beginning of the specified data, and splicing code elements to recover the user specified data.
2. The FSK and FM complex modem implementation method of claim 1, wherein the serial converting in S101 to form a symbol signal comprises:
firstly, converting the user specified data into bit data, packaging the bit data, and adding a long 1 synchronization head and a barker code synchronization head to form a code element signal, wherein the long 1 synchronization head is used for coarse synchronization of a demodulation end, and the barker code synchronization head is used for fine synchronization of the demodulation end.
3. The FSK and FM complex modem implementation of claim 1The method is characterized in that the symbol signal in S102 is subjected to FSK modulation to form a modulated signal S 1 (n) wherein:
order the
S is then 1 (n) is expressed as:
wherein f c And f 0 A, according to the matched coefficient of the user communication rate k Is a symbol signal, T b For the symbol period of time,is the initial phase; k. n is a natural number.
4. The method for implementing FSK and FM complex modulation and demodulation according to claim 1, wherein said audio signal is an FSK signal, and S103 is said audio signal and a modulated signal S 1 (n) performing a superposition and integration calculation, comprising:
the audio signal and the modulated signal S 1 (n) after superposition, expressed as:
S 0 (n)＝S 1 (n)+S 2 (n) wherein S 1 (n) is FSK signal, S 2 (n) is an audio signal;
for S 0 (n) performing integral summation expressed as:
wherein Fs is the sampling rate, specifically 2 times f c The above;
integrating and summing the signals subjected to FM modulation to S Fm (n) is represented by the formula,
wherein: freqdev is the modulation frequency offset, F c For the final radio frequency modulation frequency, freqdev is controlled by software or hardware.
5. The method as claimed in claim 4, wherein the communication terminal device is a docking device or a remote receiving device for communicating with the user terminal, and the unrecovered signal S after FM demodulation in S104 Fm The expression of (n) is:
6. the method for implementing FSK and FM complex modem according to claim 5, wherein S105: generating an in-phase component S I (n) and orthogonal component S Q (n) comprising;
the unrecovered signal S Fm (n) multiplying the quadrature carrier generated by the NCO, and omittingAnd F c Generates an in-phase component S I (n) and orthogonal component S Q (n), wherein,
7. the method for implementing FSK and FM complex modem according to claim 6,
s106, obtaining a processed in-phase component I (n) and a processed quadrature component Q (n), wherein the steps comprise;
in-phase component S I (n) and orthogonal component S Q (n) processing the signal by a low-pass filter to suppress the high-frequency component and obtain an in-phase component I (n) and a quadrature component Q (n), wherein,
8. the method for implementing FSK and FM complex modem according to claim 7,
the in-phase component I (n) after processing and the quadrature component Q (n) after processing in S107 are subjected to arctangent differential processing to obtain a recovery signal Ss (n):
a further conversion is made available which,
9. the method for implementing FSK and FM complex modem according to claim 8,
s108, performing low-pass filtering and band-pass filtering processing on the recovery signal Ss (n) to obtain an FSK time domain signal, wherein the method comprises the following steps:
performing low-pass filtering on Ss (n), wherein the low-pass filtering cutoff frequency is the upper limit of the audio frequency of the user, and demodulating an audio signal;
performing band-pass filtering on Ss (n), and performing band-pass filtering on the center frequency f c And obtaining the FSK time domain signal by frequency offset twice the bandwidth.
10. The method for implementing FSK and FM complex modems according to claim 9, wherein,
s109: the FSK time domain signal carries out bit demodulation, low-pass filtering and sampling judgment to obtain a result B SSK (n) comprising:
bit demodulation is firstly carried out on the FSK time domain signal, and the FSK signal time domain S FSK The expression (t) is:
S FSK (t)＝S 1 (t)cosω 1 t+S 2 (t)cosω 2 t, wherein S 1 (t)、S 2 (t) symbol data, ω being a reception frequency, t being time;a n g is a gate function;
in demodulation, for S FSK (t) multiplying cos ω with carrier wave respectively 1 t、cosω 2 t, obtaining an upper sideband signal S up (t)，
Then low-pass filtering is carried out to obtain a lower sideband signal S down (t)，
S up (t)＝S 1 (t)
S down (t)＝S 2 (t)
Sampling and judging to obtain result B FSK (n)
When a is n Andis 1 or 0, wherein 1 represents S up (t) is greater than S dowm (t), 0 represents S up (t) is less than S dowm (t), then, at any time S up (t) and S dowm (t) size relationship, S in S102 is recovered by sampling judgment method 1 A of (n) k The represented symbol.
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