CN108089163A - Frequency-agile radar transmit cycle design method based on optical bistable chaotic model - Google Patents

Abstract

The invention discloses a method for designing a frequency-hopping radar emission period based on an optical bistable chaotic model. A chaotic sequence with pseudo-random, noise-like and non-periodic characteristic changes, and the sequence is mapped and normalized in the radar frequency hopping period space, so as to carry out adaptive optimization design of the radar frequency hopping transmission period. The beneficial effects achieved by the present invention are: using the optical bistable chaotic model to optimize the design of the radar frequency hopping transmission cycle, generating a frequency hopping cycle with pseudo-random, noise-like and non-periodic characteristic changes, and maximizing the frequency hopping radar signal parameters. Maximum uncertainty, thereby improving the radio frequency stealth performance of the radar system.

Description

Design Method of Frequency Hopping Radar Transmission Period Based on Optical Bistable Chaos Model

technical field

The invention relates to a method for designing a frequency-hopping radar emission cycle based on an optical bistable chaotic model, and belongs to the technical field of radar frequency-hopping cycle design.

Background technique

In modern electronic warfare, stealth is a key factor for aircraft to improve its survivability and defense penetration capabilities, and it is also an important condition to ensure that the enemy is discovered and attacked first in warfare. Since the U.S. Defense Advanced Research Projects Agency in the mid-1970s took the lead in conducting research on aircraft stealth technology, after nearly half a century of development, all military powers in the world have made great progress and development in aircraft stealth technology. Various new stealth fighters emerge in an endless stream, and stealth aircraft are playing an increasingly important role on the modern battlefield. Outstanding representatives of stealth aircraft are the American F-117A stealth fighter, B-2 stealth bomber and F-22 advanced tactical stealth fighter, which respectively represent different historical stages of stealth aircraft and the development direction of stealth technology. Throughout the development of stealth aircraft, aircraft stealth technology includes radar stealth technology, infrared stealth technology, acoustic stealth technology, visible light stealth technology, laser stealth technology and radio frequency stealth technology.

Among them, radio frequency stealth technology is a new stealth technology that has been proposed in recent years. It is used to counter passive detection systems. The purpose is to keep the enemy in constant guessing. When the enemy finds the target, it thinks it is too late. On the premise of not emitting electromagnetic waves, the passive detection system can detect a long distance and has strong concealment, which poses a serious threat to the survivability of the aircraft. With the development and application of stealth technology, more and more stealth weapons with excellent performance will appear on the future battlefield, breaking the established offensive and defensive balance, promoting major changes in various detection systems in the defense system, and constantly Promote the development of stealth technology.

Radio frequency stealth technology refers to the target feature reduction control technology of radio frequency radiation signals, the purpose is to increase the difficulty of signal detection, sorting and identification of enemy radio frequency passive detection systems, and realize the "stealth" of weapon platforms relative to enemy radio frequency passive detection systems. ". The schematic diagram of the propagation of the radio frequency signal radiated by the aircraft radio frequency active sensor and its detection and processing by the passive detection system is shown in Figure 1.

The maximum uncertainty strategy is an important aspect of radio frequency stealth design. Through a certain strategy, the uncertainty of the radio frequency radiation signal parameters is maximized, making it difficult for the enemy passive detection system to detect, thereby improving the anti-interception and anti-sorting of radio frequency signals and anti-identification performance. Frequency hopping radar uses frequency hopping sequences to realize pseudo-random changes in the frequency characteristics of radar signals, thereby ensuring the radio frequency stealth performance of signals.

Although the traditional method puts forward the design idea of radar frequency hopping signal, which increases the uncertainty of radar signal parameters and improves its radio frequency stealth performance, these methods do not consider the uncertainty of frequency hopping transmission cycle, and the frequency hopping The period is a fixed value, and the enemy passive detection system can still estimate the radar signal through characteristic parameters such as frequency hopping rate and frequency hopping frequency set, so as to realize the interception, sorting and identification of airborne radar frequency hopping signals. In addition, although the currently commonly used Logistic chaotic map has good sequence randomness, it is widely used and its form is too simple. The enemy is easy to attack and decipher, and its security performance is poor; Frequency hopping periods are prone to clustering.

Contents of the invention

In order to solve the deficiencies in the prior art, the object of the present invention is to provide a method for designing the frequency-hopping radar emission cycle based on the optical bistable chaotic model, which uses the optical bistable chaotic model to optimize the design of the radar frequency-hopping emission cycle, and generates pseudo The frequency hopping period with random, noise-like and aperiodic characteristic changes maximizes the maximum uncertainty of the frequency-hopping radar signal parameters, thereby improving the radio frequency stealth performance of the radar system.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for designing a frequency-hopping radar emission period based on an optical bistable chaotic model is characterized in that it comprises the following steps:

Step 1) According to the radio frequency stealth maximum uncertainty strategy, determine the parameters of the optical bistable chaos model and the initial value of the system;

Step 2) Taking maximizing the uncertainty of the frequency hopping radar transmission period as the optimization goal, using the optical bistable chaotic model to design the frequency hopping radar transmission period, and generating an optical bistable chaotic sequence;

Step 3) designing and determining the frequency hopping radar transmission cycle sequence;

Step 4) Measure the uncertainty of the frequency hopping radar transmission period to obtain the frequency hopping radar transmission period with the maximum uncertainty.

Aforesaid a kind of frequency-hopping radar launch cycle design method based on optical bistable chaotic model, it is characterized in that, in the described step 1), specific content is: obtain the parameter A of optical bistable chaotic model, B and system initial value x ₀ , guaranteeing that the generated sequence has pseudorandom, noise-like and aperiodic properties.

Aforesaid a kind of frequency-hopping radar launch period design method based on optical bistable chaos model, it is characterized in that, described step 2) in optical bistable chaos model is as follows x _k+1 =Asin ² (x _k -B), formula Among them, A and B are system parameters, x _k represents the sequence value of the kth iteration, and x _k+1 represents the sequence value of the k+1th iteration;

For all x _k , given the parameters A, B and the initial value x ₀ of the system, the optical bistable chaotic sequence of arbitrary length can be obtained through the iterative calculation of the optical bistable chaotic model.

Aforesaid a kind of frequency hopping radar launch cycle design method based on optical bistable chaos model, it is characterized in that, described step 3) comprises the steps:

31) Determine two chaotic sequences: respectively at the initial value of the system and chaotic sequence and N is the number in the chaotic sequence;

32) According to the fixed frequency modulation period, the chaotic sequence is compared and normalized;

33) Determine the frequency hopping period according to the processing result of step 32).

Aforesaid a kind of frequency hopping radar emission period design method based on optical bistable chaos model, it is characterized in that, described step 32) comprises the following content:

Make the difference between two chaotic sequences to generate a chaotic sequence with pseudo-random, noise-like and non-periodic characteristic changes as follows:

Aforesaid a kind of frequency hopping radar launch cycle design method based on optical bistable chaos model, it is characterized in that, described step 33) comprises the following content:

Set the fixed frequency hopping period of the traditional frequency hopping radar as T _a , and set the chaotic sequence Mapping and normalization in the radar frequency hopping cycle space are as follows: in, is the optical bistable chaotic sequence Mapping sequence in frequency hopping period space;

Frequency Hopping Radar Follows the Mapping Sequence The transmission period of the frequency hopping signal is adaptively controlled.

Aforesaid a kind of frequency hopping radar launch cycle design method based on optical bistable chaotic model is characterized in that, described step 4) in the specific content is:

The uncertainty of the transmitted signal parameters of the radar system is represented by entropy. The greater the uncertainty of the signal parameters, the greater the entropy value. The mathematical expression of entropy is as follows: In the formula, T={T ₁ , T ₂ ,...,T _i ,...,T _N } represents the set of all frequency hopping periods, h(T) represents the entropy value of the frequency hopping period, p(T _i ) is The probability density function of T _i .

The beneficial effects achieved by the present invention: 1) This method not only ensures the maximum uncertainty of the frequency hopping radar signal parameters, but also improves the radio frequency stealth performance of the frequency hopping radar, and the optical bistable chaotic model has good security and is not easy to be attacked; 2) According to the sensitivity of the initial value of the chaotic sequence, this method makes the difference between the optical bistable chaotic sequence generated by the initial value of two different systems, which overcomes the clustering phenomenon of the chaotic sequence directly generated by the traditional optical bistable mapping, and can be used in the radar Mapping and normalization processing are carried out in the frequency hopping cycle space to obtain the frequency hopping radar transmission cycle with the greatest uncertainty; 3) The optical bistable chaotic model adopted is relatively complex, has better security, and is difficult to be attacked by the enemy 4) It not only meets the maximum uncertainty of radar signal parameters, but also helps to improve the radio frequency stealth performance of frequency hopping radar, and the optical bistable chaotic model has good security and is not easy to be attacked and deciphered.

Description of drawings

Figure 1 is a schematic diagram of the process of aircraft radio frequency radiation signal being intercepted by passive detection system;

Fig. 2 is a flow chart of frequency hopping radar transmission cycle design;

Figure 3 is the optical bistable chaotic sequence when the initial value is 0.5;

Figure 4 is the optical bistable chaotic sequence when the initial value is 0.6;

Fig. 5 is the frequency hopping radar transmission period when the initial value is 0.5;

Fig. 6 is the frequency hopping radar transmission period when the initial value is 0.6;

Figure 7 is a comparison curve of the frequency hopping radar transmission period under different methods.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

The present invention first utilizes the optical bistable chaotic model in the chaos theory, according to the initial value sensitivity of the chaotic sequence, sets the optical bistable model parameter value and the initial value of the system, and generates chaos with pseudo-random, noise-like and non-periodic characteristic changes Then, with the optimization goal of maximizing the uncertainty of the frequency-hopping radar transmission period, the difference between the optical bistable chaotic sequences generated by two different initial values of the system is made, and then mapped and summed in the radar frequency-hopping period space Normalized processing, the frequency hopping radar transmission period with the maximum uncertainty can be obtained.

The specific steps are:

Step 1) Determine the parameters of the optical bistable chaotic model and the initial value of the system. In this step, considering the sensitivity of the initial value of the chaotic sequence, the parameters A and B of the optical bistable chaotic model and the initial value x ₀ of the system should be determined first to ensure that the generated The sequence of has pseudorandom, noise-like and aperiodic properties.

Step 2) adopt the optical bistable chaotic model to carry out the frequency hopping radar launch period design, the optical bistable chaotic model is as follows: x _k+1 =Asin ² (x _k −B), where A and B are system parameters, x _k Indicates the sequence value of the kth iteration, and x _k+1 represents the sequence value of the k+1th iteration.

For all x _k , given the parameters A, B and the initial value x ₀ of the system, the optical bistable chaotic sequence of any length can be obtained through the iterative calculation of the optical bistable chaotic model.

respectively in the system initial value and chaotic sequence and And make the difference between the two chaotic sequences to generate a chaotic sequence with pseudo-random, noise-like and non-periodic characteristic changes as follows:

Step 3) Design the frequency hopping radar transmission period sequence: given the fixed frequency hopping period of the traditional frequency hopping radar as Ta, the chaotic sequence Mapping and normalization in the radar frequency hopping cycle space are as follows: In the formula, is the optical bistable chaotic sequence Mapped sequence in frequency hopping period space. Frequency Hopping Radar can follow the mapping sequence The transmission period of the frequency hopping signal is adaptively controlled.

Step 4) Measure the uncertainty of the transmission period of the frequency hopping radar. The uncertainty of the transmission signal parameters of the radar system is usually characterized by entropy. The greater the uncertainty of the signal parameters, the greater its entropy value. The mathematical expression of entropy is as follows: In the formula, T={T ₁ , T ₂ ,...,T _i ,...,T _N } represents the set of all frequency hopping periods, h(T) represents the entropy value of the frequency hopping period, p(T _i ) is The probability density function of T _i .

The simulation result of the present invention is described in conjunction with embodiment:

Assume that the parameters in step 1 are shown in Table 1.

Table 1 Simulation parameter settings

The optical bistable chaotic sequence when the initial value is 0.5 is shown in Figure 3, the optical bistable chaotic sequence when the initial value is 0.6 is shown in Figure 4, and the frequency hopping radar transmission period when the initial value is 0.5 is shown in Figure 5 , the frequency hopping radar transmission period when the initial value is 0.6 is shown in Figure 6.

It can be seen from the figure that even though the initial value difference is small, after many iterations, the sequence values produced by the optical bistable chaotic map are not the same, but there is an obvious clustering phenomenon. Therefore, the difference between the optical bistable chaotic sequence generated by two different initial values is used to control the radar frequency hopping period by using the new sequence obtained.

The frequency hopping period comparison curves under different methods are shown in Fig. 7 . It can be seen from Fig. 7 that the frequency hopping cycle generated by the frequency hopping radar transmission cycle design method based on the optical bistable chaotic model changes according to the pseudo-random, noise-like and aperiodic characteristics within the range of values, which overcomes the traditional optical bistable mapping. The clustering phenomenon of frequency hopping periods is generated, which makes it difficult for enemy passive detection systems to estimate and predict the timing of frequency hopping signals. The traditional frequency hopping radar uses a fixed frequency hopping period, which has the worst uncertainty and is easily detected by the enemy's interception receiver.

Table 2 Comparison of entropy values under different methods

Use the information entropy in step 4) to measure the uncertainty of the frequency hopping radar transmission period. Table 2 shows the comparison of entropy values under different frequency hopping cycle design methods. It can be seen from Table 2 that the entropy value of the frequency hopping radar transmission cycle design method based on the optical bistable chaotic model is 5.7038, while the frequency hopping cycles used in the fixed frequency hopping cycle method are all fixed values, and their entropy value is 0 . Therefore, the signal parameter uncertainty of frequency-hopping radar transmission period design method based on optical bistable chaos model is far better than that of fixed frequency-hopping period method, so it has better radio frequency stealth performance.

From the above simulation results, it can be known that the frequency hopping radar transmission cycle design method based on the optical bistable chaotic model aims at maximizing the uncertainty of the radar frequency hopping cycle, and uses the optical bistable chaotic map to generate a pseudo-random sequence with chaotic characteristics. , and map the sequence in the radar frequency hopping cycle space, and adaptively optimize the design of the frequency hopping radar transmission cycle, thereby effectively increasing the uncertainty of the radar transmission signal parameters and further improving its radio frequency stealth performance.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. It should also be regarded as the protection scope of the present invention.

Claims (7)

1. A frequency-hopping radar launch cycle design method based on optical bistable chaos model, is characterized in that, comprises the steps: Step 1) According to the radio frequency stealth maximum uncertainty strategy, determine the parameters of the optical bistable chaos model and the initial value of the system; Step 2) Taking maximizing the uncertainty of the frequency hopping radar transmission period as the optimization goal, using the optical bistable chaotic model to design the frequency hopping radar transmission period, and generating an optical bistable chaotic sequence; Step 3) designing and determining the frequency hopping radar transmission cycle sequence; Step 4) Measure the uncertainty of the frequency hopping radar transmission period to obtain the frequency hopping radar transmission period with the maximum uncertainty. 2. a kind of frequency-hopping radar launch cycle design method based on optical bistable chaotic model according to claim 1, is characterized in that, in described step 1), specific content is: obtain the parameter and system of optical bistable chaotic model The initial value x ₀ ensures that the generated sequence has pseudo-random, noise-like and non-periodic characteristics. 3. a kind of frequency-hopping radar launch cycle design method based on optical bistable chaos model according to claim 2, it is characterized in that, in described step 2), optical bistable chaos model is as follows x _k+1 =Asin ² ( x _k -B), where A and B are system parameters, x _k represents the sequence value of the kth iteration, and x _k+1 represents the sequence value of the k+1 iteration; For all x _k , given the parameters A, B and the initial value x ₀ of the system, the optical bistable chaotic sequence of arbitrary length can be obtained through the iterative calculation of the optical bistable chaotic model. 4. a kind of frequency-hopping radar launch cycle design method based on optical bistable chaotic model according to claim 1, is characterized in that, described step 3) comprises the steps: 31) Determine two chaotic sequences: respectively at the initial value of the system and chaotic sequence and N is the number in the chaotic sequence; 32) According to the fixed frequency modulation period, the chaotic sequence is compared and normalized; 33) Determine the frequency hopping period according to the processing result of step 32). 5. a kind of frequency-hopping radar launch cycle design method based on optical bistable chaos model according to claim 4, is characterized in that, described step 32) comprises the following content: Make the difference between two chaotic sequences to generate a chaotic sequence with pseudo-random, noise-like and non-periodic characteristic changes as follows: 6. a kind of frequency-hopping radar launch cycle design method based on optical bistable chaotic model according to claim 5, is characterized in that, described step 33) comprises the following content: Set the fixed frequency hopping period of the traditional frequency hopping radar as T _a , and set the chaotic sequence Mapping and normalization in the radar frequency hopping cycle space are as follows: in, is the optical bistable chaotic sequence Mapping sequence in frequency hopping period space; Frequency Hopping Radar Follows the Mapping Sequence The transmission period of the frequency hopping signal is adaptively controlled. 7. a kind of frequency-hopping radar launch cycle design method based on optical bistable chaotic model according to claim 6, is characterized in that, described step 4) in the specific content is: The uncertainty of the transmitted signal parameters of the radar system is represented by entropy. The greater the uncertainty of the signal parameters, the greater the entropy value. The mathematical expression of entropy is as follows: In the formula, T={T ₁ , T ₂ ,...,T _i ,...,T _N } represents the set of all frequency hopping periods, h(T) represents the entropy value of the frequency hopping period, p(T _i ) is The probability density function of T _i .