A high dynamic anti-interference method based on random discrete time-frequency phase distribution

Abstract

The present invention relates to a high-dynamic anti-interference method based on random discrete time-frequency phase distribution, which is suitable for the transmission of high-dynamic anti-interference signals and belongs to the field of satellite communication technology. The method designs the time-frequency phase distribution range and distribution granularity of the random discrete carrier frequency according to the usage scenario, uses carriers in the three dimensions of time, frequency, and phase to perform multi-carrier modulation on the transmitting end signal, and synthesizes the signals on multiple carriers into one carrier at the receiving end to demodulate the information data. Analysis results show that the signal capture method designed by the present invention has excellent anti-interference and anti-interception performance, and the receiving terminal has the characteristics of fast capture speed and easy engineering implementation.

Description

Technical Field

[0001] The present invention relates to a high-dynamic anti-interference method based on random discrete time-frequency phase distribution, which is suitable for the transmission of high-dynamic anti-interference signals and belongs to the technical field of satellite communications. Background Art

[0002] Satellite communication systems, characterized by open channels, are susceptible to various fading and thermal noise effects within wireless links. They must also withstand electromagnetic interference from land, sea, air, and space. Therefore, anti-interference capabilities are particularly important in satellite channel transmission. Engineering implementation requires the use of signal, spatial, and temporal processing technologies, employing a comprehensive approach to enhance anti-interference capabilities. If satellite communication terminals are deployed on highly dynamic platforms, the high speeds and wide dynamic ranges of acceleration and jerk, combined with the high-speed operation of the communication satellite, can produce significant Doppler shifts. The carrier frequency deviation and frequency deviation rate of the signals received by the satellite communication terminals are both significant, directly impacting signal acquisition. This impact is even more severe at lower communication rates, potentially disrupting normal communication. Different platforms, due to varying dynamic parameters, experience varying Doppler effects. To ensure rapid link establishment under highly dynamic conditions while maintaining robust spatial interference resistance, satellite communication signal design requires targeted performance. Summary of the Invention

[0003] This paper addresses the design challenges of high-dynamic anti-interference signals and proposes a high-dynamic anti-interference method based on random discrete time-frequency-phase distribution. This method designs the bandwidth of the transmission signal based on service requirements, and the time-frequency-phase distribution range and granularity of the random discrete carrier frequencies according to the usage scenario. The method then uses carriers in the time, frequency, and phase dimensions to perform multi-carrier modulation on the transmitting end signal. At the receiving end, the signals on multiple carriers are combined into a single carrier to demodulate the information data.

[0004] The technical solution adopted by the present invention is:

[0005] A high-dynamic anti-interference method based on random discrete time-frequency phase distribution includes the following steps:

[0006] (1) According to the usage scenario of the satellite channel terminal, set the carrier frequency range, frequency interval range and the number of frequency points N;

[0007] (2) Designing a custom time-varying pseudo-random function, using the parameters set in step (1) to generate N frequency points with different phases, and generating K carrier groups, each group including N frequency points with different phases, and then presetting the generated carrier information in the satellite channel terminal; wherein K is a set value;

[0008] (3) Use the M sequence to spread the baseband signal to be sent, randomly modulate the spread spectrum signals at different times onto N carriers in different carrier groups, and send the synthesized signal;

[0009] (4) The receiving terminal receives the signal, despreads and demodulates it, then reads the group number and frequency point number in the frame header and stores the frequency deviation value of the current carrier;

[0010] (5) Calculate the carrier information on multiple carriers based on the frequency offset value of the current carrier obtained in step (4), and then demodulate the data on each carrier based on the information of the multiple carriers and combine them.

[0011] Furthermore, the specific process of step (1) is as follows:

[0012] Step (1-1): Calculate the maximum value of the Doppler frequency shift f1 according to the high dynamic usage scenario of the satellite channel terminal; calculate the maximum frequency offset f caused by the frequency source in the link according to the stability of the satellite channel terminal and the onboard frequency source 2， ; Set the range of carrier frequency to [(-f1-f2)(f1+f2)];

[0013] Step (1-2): Determine the frequency interval range [df a df b ];

[0014] Step (1-3): Calculate the number of frequency point values ​​N based on the range of the carrier frequency and the range of the frequency interval.

[0015] Furthermore, the specific process of step (2) is as follows:

[0016] Step (2-1): Design a time-varying pseudo-random function that can generate pseudo-random numbers; set the random seed, initial value, carrier frequency range [(-f1-f2)(f1+f2)], and minimum frequency interval df a , the number of frequency points N and the time parameter t are input into the time-varying pseudo-random function; the output is N frequency points between [(-f1-f2)(f1+f2)];

[0017] Step (2-2): Input the random seed, initial value, phase range [02*π], phase interval and output phase number N into the time-varying pseudo-random function; output the random phase values ​​corresponding to N frequency points;

[0018] Step (2-3): Generate K carrier groups, each group includes N frequency points with different phases, and then preset the generated carrier information in the satellite channel terminal; where K is a set value.

[0019] Furthermore, the specific process of step (3) is as follows:

[0020] Step (3-1): Design the baseband signal into multiple burst frames, each of which is divided into a frame header and a data portion; the frame header portion adopts a modulation method with a demodulation threshold lower than a set value, and the data portion adopts a high-order modulation method;

[0021] Step (3-2): Use the M sequence to spread the baseband signal to be transmitted;

[0022] Step (3-3): Randomly modulate the spread spectrum signals at different times onto N carriers in different carrier groups, and send the synthesized signals.

[0023] Compared with the background technology, the present invention has the following advantages:

[0024] 1. The carrier group of the satellite channel terminal transmitting end of the method of the present invention constructs the carrier frequency according to the three dimensions of time, frequency and phase. Each frame signal randomly adopts a different carrier group, and the carrier interval in each group is random, which has anti-interference and anti-interception performance.

[0025] 2. The carrier group design of the satellite channel terminal transmitting end of the method of the present invention takes into account the Doppler frequency shift in the link and the stability of the frequency source in advance, so that the receiving terminal can achieve rapid signal capture.

[0026] 3. The satellite channel terminal receiving end of the method of the present invention synthesizes the signals on multiple carriers into one carrier and demodulates the data of the data part without reducing the channel transmission performance. DETAILED DESCRIPTION

[0027] The present invention is described in detail below.

[0028] A high-dynamic anti-interference method based on random discrete time-frequency phase distribution includes the following steps:

[0029] (1) According to the usage scenario of the satellite channel terminal, set the carrier frequency range, frequency interval range and the number of frequency points N;

[0030] The specific method of step (1) is as follows:

[0031] Step (1-1): Calculate the maximum value of the Doppler frequency shift f1 according to the high dynamic usage scenario of the satellite channel terminal; calculate the maximum frequency offset f caused by the frequency source in the link according to the stability of the satellite channel terminal and the onboard frequency source 2， ; Set the range of carrier frequency to [(-f1-f2)(f1+f2)];

[0032] Step (1-2): Determine the frequency interval range [df a df b ];

[0033] Step (1-3): Calculate the number of frequency point values ​​N based on the range of the carrier frequency and the range of the frequency interval.

[0034] (2) Designing a custom time-varying pseudo-random function, using the parameters set in step (1) to generate N frequency points with different phases, and generating K carrier groups, each group including N frequency points with different phases, and then presetting the generated carrier information in the satellite channel terminal; wherein K is a set value;

[0035] The specific method of step (2) is as follows:

[0036] Step (2-1): Design a time-varying pseudo-random function that can generate pseudo-random numbers; set the random seed, initial value, carrier frequency range [(-f1-f2)(f1+f2)], and minimum frequency interval df a , the number of frequency points N and the time parameter t are input into the time-varying pseudo-random function; the output is N frequency points between [(-f1-f2)(f1+f2)];

[0037] Step (2-2): Input the random seed, initial value, phase range [02*π], phase interval and output phase number N into the time-varying pseudo-random function; output the random phase values ​​corresponding to N frequency points;

[0038] Step (2-3): Generate K carrier groups, each group includes N frequency points with different phases, and then preset the generated carrier information in the satellite channel terminal; where K is a set value.

[0039] (3) Use the M sequence to spread the baseband signal to be sent, randomly modulate the spread spectrum signals at different times onto N carriers in different carrier groups, and send the synthesized signal;

[0040] The specific method of step (3) is as follows:

[0041] Step (3-1): Design the baseband signal into multiple burst frames, each of which is divided into a frame header and a data portion; the frame header portion adopts a modulation method with a demodulation threshold lower than a set value, and the data portion adopts a high-order modulation method;

[0042] Step (3-2): Use the M sequence to spread the baseband signal to be transmitted;

[0043] Step (3-3): Randomly modulate the spread spectrum signals at different times onto N carriers in different carrier groups, and send the synthesized signals.

[0044] (4) The receiving terminal receives the signal, despreads and demodulates it, then reads the group number and frequency point number in the frame header and stores the frequency deviation value of the current carrier;

[0045] (5) Calculate the carrier information on multiple carriers based on the frequency offset value of the current carrier obtained in step (4), and then demodulate the data on each carrier based on the information of the multiple carriers and combine them.

[0046] In summary, the present invention designs the time-frequency-phase distribution range and distribution granularity of random discrete carrier frequencies based on the usage scenario. It then uses digital carriers in the three dimensions of time, frequency, and phase to perform multi-carrier modulation on the transmitting end signal. At the receiving end, the signals on these multiple carriers are combined onto a single carrier to demodulate the information data. Because the carrier group design at the transmitting end of the satellite channel terminal takes into account the Doppler shift in the link and the stability of the frequency source, the receiving terminal can quickly capture signals without compromising the transmission performance of the satellite channel.

Claims

1. A high-dynamic anti-interference method based on random discrete time-frequency phase distribution, characterized in that: The steps include: (1) According to the usage scenario of the satellite channel terminal, set the carrier frequency range, frequency interval range and the number of frequency points N; (2) Design a custom time-varying pseudo-random function, use the parameters set in step (1) to generate N frequency points with different phases, and generate K carrier groups, each group includes N frequency points with different phases, and then preset the generated carrier information in the satellite channel terminal; where K is a set value; (3) Use the M sequence to spread the baseband signal to be sent, randomly modulate the spread spectrum signals at different times onto N carriers in different carrier groups, and send the synthesized signal; (4) The receiving terminal receives the signal, despreads and demodulates it, then reads the group number and frequency point number in the frame header and stores the frequency deviation value of the current carrier; (5) Calculate the carrier information on multiple carriers based on the frequency deviation value of the current carrier obtained in step (4), and then demodulate the data on each carrier based on the information of the multiple carriers and combine them; The specific process of step (1) is as follows: Step (1-1): Calculate the maximum value of the Doppler frequency shift f1 according to the high-dynamic usage scenario of the satellite channel terminal; calculate the maximum frequency offset f2 caused by the frequency source in the link according to the stability of the satellite channel terminal and the onboard frequency source; set the carrier frequency range to [(-f1-f2) (f1+f2)]; Step (1-2): Determine the frequency interval range [df a df b ]; where df a is the minimum frequency interval; Step (1-3): Calculate the number of frequency points N based on the range of the carrier frequency and the range of the frequency interval; The specific process of step (2) is as follows: Step (2-1): Design a time-varying pseudo-random function that can generate pseudo-random numbers; set the random seed, initial value, carrier frequency range [(-f1- f2) (f1+ f2)], minimum frequency interval df a , the number of frequency points N and the time parameter t are input into the time-varying pseudo-random function; the output is N frequency points between [(-f1- f2) (f1+ f2)]; Step (2-2): Input the random seed, initial value, phase range [0 2*π], phase interval and output phase number N into the time-varying pseudo-random function; output the random phase values ​​corresponding to N frequency points; Step (2-3): Generate K carrier groups, each group includes N frequency points with different phases, and then preset the generated carrier information in the satellite channel terminal; where K is a set value.

2. A high-dynamic anti-interference method based on random discrete time-frequency phase distribution according to claim 1, characterized in that: The specific process of step (3) is: Step (3-1): Design the baseband signal into multiple burst frames, each frame is divided into a frame header and a data part; the frame header part adopts a modulation method with a demodulation threshold lower than the set value, and the data part adopts a high-order modulation method; Step (3-2): Use the M sequence to spread the baseband signal to be transmitted; Step (3-3): Randomly modulate the spread spectrum signals at different times onto N carriers in different carrier groups and send the synthesized signals.