CN105245248A - A Method for Realizing Frequency Hopping Communication in Strong Electromagnetic Interference Environment - Google Patents

Abstract

The invention relates to a frequency-hopping communication method, in particular to a method for realizing a frequency-hopping communication in a strong electromagnetic interference environment. The method comprises the following steps: (1) building of a frequency-hopping system mathematical model: performing baseband modulation on an input information code sequence, synchronizing a receiving party and a transmitting party under the control of a frequency-hopping sequence controller, and finishing reception and transmission of a frequency-hopping signal; (2) building of frequency-hopping synchronization: acquiring a correct intermediate-frequency frequency with the same frequency at the same moment through a frequency-hopping receiver and a frequency-hopping transmitter; (3) determination of a frequency-hopping pattern: selecting a coefficient in a Galois field through a frequency-hopping pattern design based on an RS code, and performing transformation; and (4) networking of the frequency-hopping communication: extending the coverage of a radio station to perform networking. The method has the advantages and effects that the bit error rate of a system can be reduced to improve the overall performance of the system. The anti-interference capability in the communication is enhanced. In particular, the communication confidentiality and transmission reliability are enhanced in a complex battlefield communication environment. Moreover, a plurality of frequency-hopping systems can work at the same time within a certain broadband through different frequency-hopping patterns in the frequency-hopping communication, so that the system spectrum utilization ratio is increased greatly.

Description

A Method for Realizing Frequency Hopping Communication in Strong Electromagnetic Interference Environment

technical field

The invention relates to a method for frequency hopping communication, in particular to a method for realizing frequency hopping communication in a strong electromagnetic interference environment, which mainly improves the anti-interference ability of communication and improves the reliability of communication transmission.

Background technique

Due to the continuous, rapid and stable development of my country's economy, the demand for electricity in urban construction and life has grown rapidly. A large number of high-voltage substations and power grids have been completed or are under construction, making the current electromagnetic environment more and more complex. The focus of warfare in the 21st century will be on how to obtain the required information accurately and quickly, and how to deprive the enemy of useful information. Information superiority has become a key factor in determining the outcome of a confrontational war, and ensuring efficient and smooth information transmission is a comprehensive It is the central link of various combat elements and exerting the overall combat capability. In this way, a new element different from the traditional battlefield is formed - the complex electromagnetic environment of the battlefield. In such a battlefield environment, informatization and joint operations have developed into a brand-new combat method. Joint operations under the conditions of informationization require the organic integration of various reconnaissance and detection systems, command and control systems, and offensive weapon systems (including offensive electronic warfare systems) distributed on land, sea, air, and space battlefields to form a unified and efficient The combat system can greatly improve combat effectiveness by capturing information superiority to achieve decision-making superiority and combat operational superiority, realizing a high degree of battlefield situational awareness sharing, and a high degree of coordination and coordination of combat operations. However, where there is a spear, there must be a shield. In the process of competing for information superiority, due to the use of a large number of electronic information equipment, they are not only huge in number, complex in system, diverse in type, but also high in power, making the electromagnetic signals in the battlefield space very dense, forming A very complex electromagnetic environment.

The so-called complex electromagnetic environment refers to the multi-type, full-spectrum, high-density electromagnetic radiation signals generated under the conditions of fierce confrontation between the warring parties on the informationized battlefield, as well as the mutual influence and interference caused by the extensive use of electronic equipment by one's own side, resulting in Sudden changes in the time domain, criss-crossing in the airspace, and crowded overlapping in the frequency domain seriously affect the effectiveness of weapons and equipment, combat command, and the invisible battlefield environment of troop operations.

In order to improve the survivability in a complex electromagnetic environment, it is obviously necessary to study how to use advanced digital signal processing technology to improve or enhance the anti-jamming capability of existing communication systems, especially to improve the interference modes that cannot be countered by conventional anti-jamming technical measures. gender, importance and urgency.

With the rapid development of communication technology, the business requirements are also increasing. This leads to the contradiction between the growth of communication service demand and the limited spectrum resources, which makes the spectrum resources more and more tense. From the perspective of communication countermeasures, the congestion of frequency bands means that the available bandwidth of each communication system is limited, which will inevitably lead to greater difficulty in combating communication interference. Especially for spread spectrum communication, the widened frequency band for improving the signal-to-noise ratio also has the following disadvantages: First, it cannot make full use of the anti-interference potential brought by the widened frequency band. It is actually "wasting" precious spectrum resources; secondly, after occupying an excessively wide frequency band, there are not one but multiple users communicating at the same time in the same cell. In the multipath fading environment, it is inevitable to cause severe intersymbol interference. Realizing anti-jamming communication in limited spectrum resources puts forward new and higher requirements for spectrum resource utilization and narrowband anti-jamming technology. The second problem to be solved is that the Gaussian white noise interference signal has a relatively large impact on the channel, and it is not easy to remove in general. The so-called Gaussian white noise interference signal means that the amplitude distribution of the interference signal obeys the Gaussian distribution, and its power spectral density is evenly distributed. Since the Gaussian white noise interference signal has a very wide frequency band and almost occupies the entire field, it overlaps with the communication signal and cannot distinguish between useful signals and interference signals, and the above-mentioned frequency hopping technology and spread spectrum technology cannot achieve satisfactory results.

Contents of the invention

In order to solve the above technical problems, the present invention provides a method for realizing frequency hopping communication and networking in a strong electromagnetic interference environment, with the purpose of improving the reliability and effectiveness of the communication system so that it can adapt to the complex environment of strong electromagnetic interference.

In order to achieve the above object, the present invention realizes a method for frequency hopping communication in a strong electromagnetic interference environment, the steps are as follows:

(1) The establishment of the mathematical model of the frequency hopping system, through the baseband modulation of the input information code sequence, and then through the control of the frequency hopping sequence controller, the receiver and the sender are synchronized to complete the reception and transmission of the frequency hopping signal;

(2) The establishment of frequency hopping synchronization, so that the frequency hopping receiver and the frequency hopping transmitter use the same frequency at the same time to obtain the correct intermediate frequency;

(3) The determination of the frequency hopping pattern, through the design of the frequency hopping pattern based on the RS code, selects the coefficients in the Galois field, and then transforms;

(4) The networking of frequency hopping communication, and then expand the coverage of the radio station for networking.

In step (1), after the information data at the sending end is converted by the waveform, it enters the carrier modulation, and the carrier is generated by the variable frequency synthesizer controlled by the frequency hopping sequence generator. The value of the frequency hopping sequence is changed once, and the carrier frequency is changed once. The symbol width T _c , then the carrier frequency hops once every time interval T _c ; in this way, the carrier wave and information data generated by the frequency synthesizer are controlled by the frequency hopping sequence generator to perform carrier modulation, and then the low-frequency signal is removed through a high-pass filter. After the signal comes out of the high-pass filter, it is transmitted through the radio frequency filter and received by the receiving end. At the receiving end, the received signal first passes through a wide-band filter. In order to ensure the synchronization of the receiving and sending signals, the receiver itself The vibration signal is also a frequency hopping signal. The hopping rule is controlled by the pseudo-random code of the receiving end, and the pseudo-random code generated by the receiving end is the same as that of the sending end. The law of controlling frequency change is the same. The two frequency synthesizers generate The frequency is corresponding, but the corresponding frequency has a frequency difference f _i , which is exactly the intermediate frequency of the receiver; as long as the pseudo-random codes of the sending and receiving parties are synchronized, the hopping frequencies generated by the frequency synthesizers of the receiving and receiving parties can be synchronized, and pass through a bandpass After the filter, a fixed intermediate frequency signal can be obtained, and then the intermediate frequency signal is demodulated by a data demodulator, and the transmitted information can be restored, and the transmission and reception of the frequency hopping signal is completed so far.

In step (2), during the synchronization process of the receiver, the receiver is in the slow scanning state as soon as it is turned on, and performs frequency hopping at a rate lower than the frequency modulation rate to capture the synchronization information in the preamble sequence. If no synchronization is captured The information will continue to scan slowly and repeat the above steps. If the synchronization information is captured, it will further judge whether it is the leading sequence. If it is the leading sequence, check the synchronization time and follow up. Confirm the leading sequence again, if it is the leading sequence, then receive the network number and time information, if it is not the leading sequence, return to the initial slow scan state, and finally complete the establishment of synchronization.

In step (3), the design process of the frequency hopping pattern is: (1) input the coefficients of the Galois field generator polynomial, the power m of the field, and the values of c1 and c0; the elements in the Galois field have three representations method, for GF(2 ³ ), the generated polynomial is f(x)=x ³ +x+1α=2=(010), for the Galois Field α=2=(010), so that the 2 in the field ³ = 8 elements are represented by three different methods, and the obtained α ⁿ is α ^n-1 , which is left shifted by one bit, and when the highest bit on the left side of the vector is 1, then the left shifted vector is m -1 item, the coefficient of the power corresponding to the generator polynomial is added modulo two, so that the coefficient of Galois is obtained; (2) Calculate the period p of the sequence; (3) Call the sub-function to convert the value of c1 from decimal to power times, and then multiply the power of c1 with the elements in the field to output the power matrix cxm of the multiplication result; (4) determine whether the coefficient c0 is 0, if it is 0, convert the power in the matrix cxm to decimal If the coefficient is not 0, convert c0 and matrix cxm into m-bit 2-element vectors c0-w, cxw, then add the components of c0-w, cxw and convert them to decimal; (5 ) code generator polynomial improvement, in order to solve the problem of asynchronous networking, the Hamming cross-correlation sidelobe surge between any two sequences, the generator polynomial is improved below, and each code bit element of the sequence {p _j } is added A fixed quantity {α ^2j }, we get polynomial; if the polynomial of another sequence {q _j } is generated by the polynomial of Q(α ^s x)=(α ^s x) ² +C ₀ +C ₁ α ^s x, then the relationship between P(x) and Q(x) The difference is expressed as P(x)-Q(α ^s x)=(1-α ^2s )x ² +C ₁ (1-α ^s )x, because ^s in α s can be selected arbitrarily, so the maximum consistency between the two sequences The code number has nothing to do with the start code position between two sequences, and can be used in asynchronous frequency hopping communication network.

In step (4), the frequency hopping communication station has 8 working states, including scanning state, call setting state, sending call state, fixed frequency communication state, late network application state, receiving late network application information state, sending late network guidance Status and frequency hopping communication status, including:

a) Status scanning: Before networking, all frequency-hopping radio stations in the network are in the scanning state, and the status of the frequency-hopping radio stations is determined through status scanning;

b) Calling process: frequency hopping communication can be divided into three steps in the networking process. The first is frequency hopping network calling, that is, a radio station can call all radio stations in this network or other networks by setting it to call a network. The second is frequency hopping selective calling, a certain radio station calls another radio station in this network by setting the calling object in this network; the last is fixed frequency calling, frequency hopping radio station works by setting a fixed working frequency In the fixed-frequency communication state, communicate with the fixed-frequency radio station on the selected channel;

c) Delayed network entry process: When other stations in the network are already in the state of frequency hopping communication, one or more stations fail to join the network for some reason, and certain measures need to be taken to enter the working state of the frequency hopping communication network, then the station will Enter the state of late network application, then enter the state of receiving late network application, once the application is received, it will enter the state of sending late network guidance, and finally enter the state of frequency hopping communication.

Advantages and effects of the present invention: the bit error rate of the system can be reduced so as to improve the overall performance of the system. Improve the anti-interference ability of communication, especially in the complex battlefield communication environment, improve the confidentiality of communication and the reliability of transmission, and frequency hopping communication can use different frequency hopping patterns to accommodate multiple frequency hopping systems in a certain broadband at the same time Work, thereby greatly improving the system spectrum utilization.

Description of drawings

Fig. 1 is a transition diagram of the working state of the frequency hopping communication station in the present invention.

Fig. 2 is a block diagram of the frequency hopping communication system in the present invention.

Fig. 3 is a flow chart of generating a frequency hopping pattern in the present invention.

Fig. 4 is a flow chart of the receiver synchronization in the present invention.

Fig. 5 is a block diagram of the frequency hopping networking process of the present invention.

detailed description

In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings.

A method for realizing frequency hopping communication in a strong electromagnetic interference environment, the steps are as follows:

(1) The establishment of the mathematical model of the frequency hopping system, through the baseband modulation of the input information code sequence, and then through the control of the frequency hopping sequence controller, the receiver and the sender are synchronized to complete the reception and transmission of the frequency hopping signal;

(2) The establishment of frequency hopping synchronization, so that the frequency hopping receiver and the frequency hopping transmitter use the same frequency at the same time to obtain the correct intermediate frequency;

(3) The determination of the frequency hopping pattern, through the design of the frequency hopping pattern based on the RS code, selects the coefficients in the Galois field, and then transforms;

(4) The networking of frequency hopping communication, and then expand the coverage of the radio station for networking.

In step (1), after the information data at the sending end is converted by the waveform, it enters the carrier modulation, and the carrier is generated by the variable frequency synthesizer controlled by the frequency hopping sequence generator. The value of the frequency hopping sequence is changed once, and the carrier frequency is changed once. The symbol width T _c , then the carrier frequency hops once every time interval T _c ; in this way, the carrier wave and information data generated by the frequency synthesizer are controlled by the frequency hopping sequence generator to perform carrier modulation, and then the low-frequency signal is removed through a high-pass filter. After the signal comes out of the high-pass filter, it is transmitted through the radio frequency filter and received by the receiving end. At the receiving end, the received signal first passes through a wide-band filter. In order to ensure the synchronization of the receiving and sending signals, the receiver itself The vibration signal is also a frequency hopping signal. The hopping rule is controlled by the pseudo-random code of the receiving end, and the pseudo-random code generated by the receiving end is the same as that of the sending end. The law of controlling frequency change is the same. The two frequency synthesizers generate The frequency is corresponding, but the corresponding frequency has a frequency difference f _i , which is exactly the intermediate frequency of the receiver; as long as the pseudo-random codes of the sending and receiving parties are synchronized, the hopping frequencies generated by the frequency synthesizers of the receiving and receiving parties can be synchronized, and pass through a bandpass After the filter, a fixed intermediate frequency signal can be obtained, and then the intermediate frequency signal is demodulated by a data demodulator, and the transmitted information can be restored, and the transmission and reception of the frequency hopping signal is completed so far.

In step (2), during the synchronization process of the receiver, the receiver is in the slow scanning state as soon as it is turned on, and performs frequency hopping at a rate lower than the frequency modulation rate to capture the synchronization information in the preamble sequence. If no synchronization is captured The information will continue to scan slowly and repeat the above steps. If the synchronization information is captured, it will further judge whether it is the leading sequence. If it is the leading sequence, check the synchronization time and follow up. Confirm the leading sequence again, if it is the leading sequence, then receive the network number and time information, if it is not the leading sequence, return to the initial slow scan state, and finally complete the establishment of synchronization.

In step (3), the design process of the frequency hopping pattern is: (1) input the coefficients of the Galois field generator polynomial, the power m of the field, and the values of c1 and c0; the elements in the Galois field have three representations method, for GF(2 ³ ), the generated polynomial is f(x)=x ³ +x+1α=2=(010), for the Galois Field α=2=(010), so that the 2 in the field ³ = 8 elements are represented by three different methods, and the obtained α ⁿ is α ^n-1 , which is left shifted by one bit, and when the highest bit on the left side of the vector is 1, then the left shifted vector is m -1 item, the coefficient of the power corresponding to the generator polynomial is added modulo two, so that the coefficient of Galois is obtained; (2) Calculate the period p of the sequence; (3) Call the sub-function to convert the value of c1 from decimal to power times, and then multiply the power of c1 with the elements in the field to output the power matrix cxm of the multiplication result; (4) determine whether the coefficient c0 is 0, if it is 0, convert the power in the matrix cxm to decimal If the coefficient is not 0, convert c0 and matrix cxm into m-bit 2-element vectors c0-w, cxw, then add the components of c0-w, cxw and convert them to decimal; (5 ) code generator polynomial improvement, in order to solve the problem of asynchronous networking, the Hamming cross-correlation sidelobe surge between any two sequences, the generator polynomial is improved below, and each code bit element of the sequence {p _j } is added A fixed quantity {α ^2j }, we get polynomial; if the polynomial of another sequence {q _j } is generated by the polynomial of Q(α ^s x)=(α ^s x) ² +C ₀ +C ₁ α ^s x, then the relationship between P(x) and Q(x) The difference is expressed as P(x)-Q(α ^s x)=(1-α ^2s )x ² +C ₁ (1-α ^s )x, because ^s in α s can be selected arbitrarily, so the maximum consistency between the two sequences The code number has nothing to do with the start code position between two sequences, and can be used in asynchronous frequency hopping communication network.

In step (4), the frequency hopping communication station has 8 working states, including scanning state, call setting state, sending call state, fixed frequency communication state, late network application state, receiving late network application information state, sending late network guidance Status and frequency hopping communication status, including:

In the scanning state, if a station has not yet entered the network, apply for late network entry, thus entering the late network application state, and automatically return to the scanning state after the late network application. In the scanning state, after receiving the network call to the local network or the selective call to the local station, it will automatically enter the frequency hopping communication state. In the scanning state, if you want to call other stations, if you have completed the setting, you can directly call to enter the sending call state. If you have not completed the setting, you will enter the call setting state. After the setting is completed, you will return to the scanning state. If you call other stations, you will enter the sending call state. state. After sending the call, enter the frequency hopping communication state and communicate with the called station. In the state of frequency hopping communication, if it receives late network applications from other stations, it will send late network guidance information while continuing to maintain frequency hopping communication. If a fixed-frequency call is received from a fixed-frequency radio station, the operator can decide to carry out fixed-frequency communication. While maintaining frequency-hopping synchronization, switch to a fixed-frequency channel to communicate with a fixed-frequency radio station. After the communication is completed, return to frequency-hopping communication. state. After the frequency hopping communication is completed or during the frequency hopping communication process, the application enters the scanning state, and then returns to the scanning state. In order to make the stations in the network only search and scan in the network, each station in the network needs to set call parameters before networking. In this way, the radio station in the network enters the frequency hopping communication state only when it monitors the call to the local network or the local station, that is to say, the subordinate station only synchronizes with the main station calling the network number of the local network. Before networking, all frequency hopping stations in the network are in the scanning state. When the master station presses the transceiver switch, the master station will first send out a synchronization signal. After the synchronization signal is correctly received by other stations in the network, each station will automatically correct it first. The clock of this station automatically tracks its own frequency hopping rate to the frequency hopping rate of the main station, and then establishes frequency hopping communication. After the communication is completed, all radio stations in the network return to the scanning state again to wait for the next communication.

Frequency hopping radio calls are divided into the following three modes: frequency hopping network call, frequency hopping selective call, and fixed frequency call.

(1) Frequency hopping network call: Frequency hopping network call refers to a radio station calling all radio stations in this network or other networks to realize frequency hopping communication. When a frequency hopping radio station makes a network call, all other radio stations that have the same frequency hopping frequency table, key number, and network number as the radio station, that is, all radio stations in the same subnet, will respond to the network call signal.

(2) Frequency hopping selective call: frequency hopping selective call refers to a radio station calling another radio station in the network to realize frequency hopping communication. One radio station selectively calls another radio station in the same subnet, as long as the station number to be called is directly selected and the call is made. A radio station cannot selectively call two radio stations with different station numbers at the same time.

(3) Fixed-frequency call: The frequency-hopping radio station can work in the fixed-frequency communication state, and communicate with the fixed-frequency radio station on the selected channel. The fixed-frequency radio station uses the agreed fixed-frequency calling frequency to send a call to the frequency-hopping radio station. The frequency-hopping radio station opens a window at this fixed-frequency calling frequency. After finishing, press the "fixed call" button again to return to the original frequency hopping network.

Delayed access to the network refers to a network access method that requires certain measures to enter the frequency hopping communication network when other stations in the network are already in the state of frequency hopping communication and one or more stations fail to join the network for some reason. Late network access is mainly divided into three types of network access: active application for late network access, passive traction late network access and service synchronization late network access.

(1) Active application for late network access: Active application for late network access refers to the network access method in which the radio station that has not entered the frequency hopping communication network actively sends out a network access application, and then the radio station in the network sends a late network entry guide signal. The working process of actively applying for late network entry is divided into four stages: sending late network application information, receiving late network application information, sending late network guidance information, and late network establishment status.

(2) Passive traction late network entry: Passive traction late network entry refers to a late network entry method in which the stations in the network find out that there are stations that have not entered the network through roll call after networking, and guide the non-network stations to enter the communication network through the late network entry function. The working process is that the unnetworked radio stations are in the scanning state, and the in-network radio stations are in the frequency hopping communication state, directly sending the late-entry network guidance signal, and the unnetworked radio stations are drawn into the frequency hopping communication network.

(3) Service synchronization late network entry: Service synchronization late network entry refers to a late network entry in which stations that have not joined the network do not actively apply, and stations on the network do not call names, but realize late network entry by receiving service synchronization information inserted in the FM data stream Way. The working process is that in the normal frequency hopping communication process, all the stations in the network send service synchronization information on the predetermined service frequency at regular intervals, and the stations that are not connected to the network search for the frequency hopping data stream inserted in the predetermined service frequency. Service synchronization information. After receiving all the necessary synchronization information, the non-network station adjusts the real-time clock to realize the late network entry.

In a strong electromagnetic environment, complex interference will occur in the communication system. Common anti-interference technologies include spread spectrum technology, smart antenna technology, and hybrid technology combining multiple technologies. Frequency hopping is one of the most commonly used spread spectrum methods. Its working principle refers to the communication method in which the carrier frequency of the transmission signal transmitted by both parties is discretely changed according to a predetermined rule, that is to say, the carrier frequency used in communication is controlled by a pseudo-random change code. And jump randomly. From the time domain point of view, the frequency hopping signal is a multi-frequency frequency shift keying signal; from the frequency domain point of view, the frequency spectrum of the frequency hopping signal is a random hopping at unequal intervals on a wide frequency band. Compared with the direct spread system, the pseudo-random sequence in the frequency hopping system is not transmitted directly, but is used to select the channel.

In the model design process of frequency hopping communication, we introduce the following mathematical model. At the sending end of the system, baseband modulation is performed on the input information code sequence to obtain the modulated signal m(t), and its frequency bandwidth is B _m . The pseudo-random code sequence independently generated by the frequency hopping sequence generator is used as a frequency hopping sequence to control the frequency synthesizer, so that the output frequency changes randomly according to different frequency hopping patterns or instructions. The modulation signal m(t) modulates the random carrier frequency to obtain the frequency hopping signal S _i (t), which is similar to the carrier modulation signal, and can be expressed in mathematical formula as: In this formula, ω ₀ +nω _△ and _{ω △} is the frequency _hopping frequency interval. The frequency hopping system undergoes different transformations, and the final output signal is S(t), expressed as: S(t)=S _i (t)+J(t)+n(t). At the receiving end, in order to demodulate the input signal, it is necessary to have a frequency hopping command generated by the same local pseudo code generator as the sending end to control the local frequency synthesizer so that the frequency of the output local oscillator signal jumps correspondingly with the frequency of the sending party. , the hopping local oscillator signal converts the frequency of the received frequency hopping signal, and then passes through a low-pass filter to realize de-hopping to obtain the modulated signal m(t). After low-pass filter, we can get $S_o\left(t\right)=\frac{1}{2}m\left(t\right)+{\mathrm{no}}^{\′}\left(t\right)+J^{\′}\left(t\right).$

The design of frequency hopping system synchronization, frequency hopping synchronization means that the frequency hopping receiver and the frequency hopping transmitter use the same frequency at the same time. In this way, the frequency of the received signal and the frequency generated by the local frequency synthesizer can be mixed to obtain the correct intermediate frequency, and then the information signal can be demodulated from it, otherwise the information signal cannot be demodulated correctly. A digital frequency hopping system refers to a frequency hopping communication system that transmits digital voice or data. Therefore, it transmits frequency hopping synchronization information in the form of data frames. Frequency hopping synchronization methods of digital systems are nothing more than synchronization prefix method, self-synchronization method and reference clock method. Synchronization prefix method. The sending end needs to send a code word containing synchronization information, and after the receiving end decodes it, the local frequency hopper of the receiving end is synchronized with the sending end according to the synchronization information. In addition to bit synchronization and frame synchronization, synchronization information should mainly include real-time status information of frequency hopping patterns or real-time clock information, which is the so-called "TOD" information (Time of the Day). The real-time clock information includes year, month, day, hour, minute, second, millisecond, microsecond, nanosecond, etc.; the status information refers to the real-time code sequence status of the pseudo code generator. According to these information, the receiving end can know the frequency of the current frequency hopping dwell time and the frequency of the next hop dwell time, so that the frequency hoppers at the transceiver end can work synchronously. In order to ensure the correct reception of TOD information, bit synchronization and frame synchronization bits are installed in the synchronization information data frame format as shown in the figure. In addition, error control technology can be used for TOD information bits, such as error correction coding, correlation coding or large number judgment, in order to improve the reliability of transmission.

The design of the frequency hopping pattern, the so-called frequency hopping is the law of carrier hopping. When the frequency hopping communication networking methods are the same, designing a good frequency hopping pattern can greatly reduce frequency hopping code collisions. The design of frequency hopping sequence family mainly involves five parameters: frequency number q, sequence length L, sequence number N, Hamming correlation value H and frequency interval d. These parameters are mutually constrained, and through the analysis of these parameters, an ideal family of frequency hopping sequences can be designed. A sequence is called a non-repeating sequence if each frequency occurs at most once in a sequence period. The design of the frequency hopping pattern is actually the selection of the pseudo-code pattern. In order to obtain a good frequency hopping pattern, the pseudo-random code has the following requirements: 1. Under different translations, the number of overlaps between codes should be small, and the average number of overlaps in the frequency hopping period should be small, which requires the cross-correlation characteristics of the codes 2. The number of coincidences between each code sequence and its own translation should be small, which requires that the autocorrelation characteristics of the code be better; 3. The number of available code sequences should be large, and this number must first meet the frequency hopping of using the same frequency band The number of communication users is required, and it is hoped that the number of them should be as large as possible to meet the confidentiality requirements. The type of frequency hopping pattern generally refers to the pseudo-random code and control method used as the control code of the frequency hopping pattern. At present, the most widely used pseudo-random codes are mainly m-sequence, M-sequence and R-S code sequence. The m-sequence is a commonly used control code for frequency hopping patterns, it is easy to generate, but from the point of view of confidentiality, this frequency hopping pattern has shortcomings in communication systems, because when computer simulation is used, the law can be found quickly property, and the key size of the m-sequence is not large enough. The number of M-sequences is much more than that of m-sequences. It is a non-linear shift register sequence, which can generate many frequency hopping patterns and has strong confidentiality. R-S code is a kind of best approximate orthogonal code, which has many users and is easy to implement, so it is an ideal frequency hopping control code.

Claims (5)

1. A method for realizing frequency-hopping communication under a strong electromagnetic interference environment, characterized in that the steps are as follows: (1) The establishment of the mathematical model of the frequency hopping system, through the baseband modulation of the input information code sequence, and then through the control of the frequency hopping sequence controller, the receiver and the sender are synchronized to complete the reception and transmission of the frequency hopping signal; (2) The establishment of frequency hopping synchronization, so that the frequency hopping receiver and the frequency hopping transmitter use the same frequency at the same time to obtain the correct intermediate frequency; (3) The determination of the frequency hopping pattern, through the design of the frequency hopping pattern based on the RS code, selects the coefficients in the Galois field, and then transforms; (4) The networking of frequency hopping communication, and then expand the coverage of the radio station for networking. 2. A kind of method that realizes frequency hopping communication under strong electromagnetic interference environment according to claim 1, it is characterized in that in the step (1), after sending end information data is converted by waveform, enter carrier modulation, carrier is by frequency hopping The sequence generator controls the variable frequency synthesizer to generate, the value of the frequency hopping sequence is changed once, the carrier frequency is changed once, and the symbol width of the frequency hopping sequence is T _c , then the carrier frequency is hopped once every time interval T _c ; The sequence generator controls the carrier wave and information data generated by the frequency synthesizer to carry out carrier modulation, and then removes the low-frequency signal through the high-pass filter. , the received signal first passes through a wideband filter. In order to ensure the synchronization of the receiving and sending signals, the local oscillator signal of the receiver is also a frequency hopping signal. The hopping rule is controlled by the pseudo-random code at the receiving end, while the receiving The pseudo-random code generated by the end is the same as that of the sender, and the law of controlling frequency change is the same. The frequencies generated by the two frequency synthesizers correspond to each other, but there is a frequency difference f _i between the corresponding frequencies, which is just the intermediate frequency of the receiver; as long as the transceiver The pseudo-random code synchronization of both parties can synchronize the hopping frequencies generated by the frequency synthesizers of the transmitting and receiving parties. After passing through a band-pass filter, a fixed intermediate frequency signal can be obtained, and then the intermediate frequency signal is processed by a data solution. After demodulation by the modulator, the sent information can be restored, and the sending and receiving of the frequency hopping signal is completed. 3. A method for realizing frequency hopping communication in a strong electromagnetic interference environment according to claim 1, characterized in that in step (2), during the synchronization process of the receiving party, the receiving party is in slow scan as soon as it is turned on State, frequency hopping at a rate lower than the frequency modulation rate to capture the synchronization information in the preamble sequence, if no synchronization information is captured, continue to perform slow scanning and repeat the above steps, if the synchronization information is captured, then further judge whether it is a preamble Sequence, if it is the leading sequence, check the synchronization time and follow up, otherwise enter the late network entry state, after checking the synchronization time, confirm the leading sequence again, if it is the leading sequence, receive the network number and time information, if it is not the leading sequence Then return to the initial slow scan state, and finally complete the establishment of synchronization. 4. a kind of method that realizes frequency hopping communication under strong electromagnetic interference environment according to claim 1, it is characterized in that in step (3), the design process to frequency hopping pattern is: (1) input Galois field generation Polynomial coefficients, the power m of the field, and the values of c1 and c0; there are three ways to express the elements in the Galois field. For GF(2 ³ ), the generated polynomial is f(x)=x ³ +x+ 1α=2=(010), for the Galois field α=2=(010), the 2 ³ =8 elements in the field are represented by three different methods, and the obtained α ⁿ is α ^n-1 Shift one bit to the left, and when the highest bit on the left side of the vector is 1, then add the coefficient modulo two of the first m-1 items of the vector after the left shift, and the power corresponding to the generator polynomial, so as to obtain the coefficient of Galois ;(2) Calculate the period p of the sequence; (3) Call the subfunction, convert the value of c1 from decimal to a power representation, and then multiply the power representation of c1 with the elements in the field to output the power of the multiplication result Matrix cxm; (4) Determine whether the coefficient c0 is 0, if it is 0, convert the power in the matrix cxm into a decimal number, and finally output it, if the coefficient is not 0, convert c0 and the matrix cxm into m-bit binary Vector c0-w, cxw, then add the components of c0-w, cxw and convert them into decimal; (5) Improvement of code generator polynomial, in order to solve asynchronous networking, Hamming cross-correlation between any two sequences Lobe surge problem, the generator polynomial is improved as follows, and a fixed amount {α ^2j } is added to each code element of the sequence {p _j } to obtain polynomial; if the polynomial of another sequence {q _j } is generated by the polynomial of Q(α ^s x)=(α ^s x) ² +C ₀ +C ₁ α ^s x, then the relationship between P(x) and Q(x) The difference is expressed as P(x)-Q(α ^s x)=(1-α ^2s )x ² +C ₁ (1-α ^s )x, because ^s in α s can be selected arbitrarily, so the maximum consistency between the two sequences The code number has nothing to do with the start code position between two sequences, and can be used in asynchronous frequency hopping communication network. 5. a kind of method that realizes frequency hopping communication under strong electromagnetic interference environment according to claim 1, it is characterized in that in step (4), frequency hopping communication radio station has 8 operating states, comprises scanning state, call setting state , Sending call status, fixed frequency communication status, late network application status, receiving late network application information status, sending late network guidance status and frequency hopping communication status, including: a) Status scanning: Before networking, all frequency-hopping radio stations in the network are in the scanning state, and the status of the frequency-hopping radio stations is determined through status scanning; b) Calling process: frequency hopping communication can be divided into three steps in the networking process. The first is frequency hopping network calling, that is, a radio station can call all radio stations in this network or other networks by setting it to call a network. The second is frequency hopping selective calling, a certain radio station calls another radio station in this network by setting the calling object in this network; the last is fixed frequency calling, frequency hopping radio station works by setting a fixed working frequency In the fixed-frequency communication state, communicate with the fixed-frequency radio station on the selected channel; c) Delayed network entry process: When other stations in the network are already in the state of frequency hopping communication, one or more stations fail to join the network for some reason, and certain measures need to be taken to enter the working state of the frequency hopping communication network, then the station will Enter the state of late network application, then enter the state of receiving late network application, once the application is received, it will enter the state of sending late network guidance, and finally enter the state of frequency hopping communication.