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

Abstract

The invention relates to a high-dynamic anti-interference method based on random discrete time-frequency phase distribution, is suitable for transmission of high-dynamic anti-interference signals, and belongs to the technical field of satellite communication. The method comprises the following steps: designing a time-frequency phase distribution range and distribution granularity of random discrete carrier frequency according to a use scene, carrying out multi-carrier modulation on a signal at a sending end by using carriers in three dimensions of time, frequency and phase, and synthesizing the signals on a plurality of carriers on one carrier at a receiving end to demodulate information data. An analysis result shows that the signal capturing method designed by the invention has good anti-interference and anti-interception performance, and the receiving terminal has the characteristics of high capturing speed and easiness in engineering realization.

Description

Technical Field

[0001] The 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 have the characteristics of open channels and are easily affected by various fading and thermal noise from wireless links. They must also withstand electromagnetic interference from land, sea, air, and space. Therefore, anti-interference ability in satellite channel transmission is particularly important. In engineering implementation, it is necessary to consider the use of signal, space, and time processing technologies, and use a variety of means to enhance anti-interference capabilities. If the satellite communication terminal is deployed on a high-dynamic platform, due to the high flight speed of the high-dynamic platform, the dynamic change range of acceleration and jerk is large, and the communication satellite is also running at high speed. The system will produce a large Doppler frequency shift, and the carrier frequency deviation and frequency deviation change rate of the signal received by the satellite communication terminal are large, which directly affects the satellite communication terminal's capture of the signal. When the communication rate is low, this impact is more serious, and even normal communication cannot be achieved. Due to different dynamic change parameters of different high-dynamic platforms, the impact of the Doppler effect is also different. In order to ensure that the link is quickly established under high-dynamic conditions and have spatial anti-interference capabilities, it is necessary to design the satellite communication signal for performance. Summary of the invention

[0003] Aiming at the design problem of high-dynamic anti-interference signals, the present invention proposes a high-dynamic anti-interference method based on random discrete time-frequency phase distribution. The method designs the bandwidth of the transmission signal according to business requirements, designs the time-frequency phase distribution range and distribution granularity of the random discrete carrier frequency according to the usage scenario, uses the carriers of 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.

[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 comprises the following steps:

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

[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 f according to the high dynamic usage scenario of the satellite channel terminal 1 ; According to the stability of the satellite channel terminal and the onboard frequency source, calculate the maximum frequency offset f caused by the frequency source in the link 2， ; Set the carrier frequency range to [(-f 1 -f 2 )(f 1 +f 2 )];

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

[0014] Step (1-3): Calculate the number of frequency point values ​​N according to 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 [(-f 1 -f 2 )(f 1 +f 2 )], 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 [(-f 1 -f 2 )(f 1 +f 2 )];

[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; wherein 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 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 a set value, and the data part 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 of different carrier groups and send the synthesized signals.

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

[0024] 1. The satellite channel terminal transmitting end carrier group 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 realize 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, which will not reduce 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 comprises the following steps:

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

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

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

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

[0033] Step (1-3): Calculate the number of frequency point values ​​N according to 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 [(-f 1 -f 2 )(f 1 +f 2 )], 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 [(-f 1 -f 2 )(f 1 +f 2 )];

[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; wherein 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 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 a set value, and the data part 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 of 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 according to the usage scenario, uses the digital carriers of 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. Since the carrier group design at the transmitting end of the satellite channel terminal considers the Doppler frequency shift in the link and the stability of the frequency source in advance, the receiving terminal can realize rapid signal capture without reducing 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, the range of the carrier frequency, the range of the frequency interval, and the number of frequency points N are set; (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; (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 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.

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 (1) is as follows: Step (1-1): According to the high dynamic usage scenario of the satellite channel terminal, calculate the maximum value of the Doppler frequency shift f1; according to the stability of the satellite channel terminal and the onboard frequency source, calculate the maximum frequency offset f caused by the frequency source in the link 2， ; Set the range of carrier frequency to [(-f1-f2)(f1+f2)]; Step (1-2): Determine the range of frequency spacing [df a df b ]; Step (1-3): Calculate the number of frequency point values ​​N according to the range of the carrier frequency and the range of the frequency interval.

3. The high dynamic anti-interference method based on random discrete time-frequency phase distribution according to claim 2 is characterized in that: 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)], and minimum frequency interval df a , the number of frequency point values ​​N and the time parameter t are input into the time-varying pseudo-random function; the output is N frequency point values ​​between [(-f1-f2)(f1+f2)]; 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; 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; wherein K is a set value.

4. The high dynamic anti-interference method based on random discrete time-frequency phase distribution according to claim 1 is characterized in that: The specific process of step (3) is as follows: 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 a 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 of different carrier groups and send the synthesized signals.