Low-interception signal design method for anomaly defense of short-range detection high-end equipment

Abstract

The invention discloses a low-interception signal design method for anomaly defense of short-range detection high-end equipment, and relates to the technical field of radio countermeasure of modern electronic warfare. A low-interception detection signal is designed for a digital radio signal frequency measurement receiver commonly used in electronic warfare, and the risk that the detection signal is intercepted by an enemy electronic reconnaissance system in the working process is reduced, so that the capacity of equipment for actively defending against enemy interference is improved. Firstly, a chaotic function is designed and used for generating a group of random sequences; secondly, converting the random sequence into rectangular coordinates by using a 16-point constellation diagram, and generating subcarrier modulation information; then, performing subcarrier amplitude modulation on the orthogonal frequency division multiplexing signal by using multiple groups of modulation information to generate a baseband signal; and finally, respectively modulating the baseband signals to different carrier frequencies, and simultaneously transmitting the baseband signals outwards through different antennas by using a multiple-input multiple-output technology. The designed detection signal is represented as a broadband multi-carrier simultaneous arrival signal, has a lower instantaneous power spectral density peak value, can effectively reduce the risk that the detection signal is intercepted by an enemy frequency measurement receiver in the working process, and further improves the capability of defending the enemy interference in the equipment working process.

Description

Technical Field

[0001] The present invention relates to the field of modern electronic warfare radio countermeasures, and particularly to a design method for abnormal defense of low-intercept signals of short-range detection high-end equipment. Background Art

[0002] With the rapid development of software, hardware, and digital signal processing technologies, various radio detection equipment are widely used in modern battlefields. Whether the radio detection signals they emit can avoid the monitoring of the enemy's electronic reconnaissance system is directly related to the safety of short-range radio detection equipment during operation, reducing the risk of being struck by enemy weapons. Therefore, the design of low-intercept detection signals has become a research hotspot. Broadly speaking, low-intercept detection signals can be divided into three directions: anti-interception, anti-sorting, and anti-identification. Anti-interception can be further divided into anti-detection and anti-parameter measurement. When the energy of the detection signal at the location of the electronic reconnaissance frequency measurement receiver is lower than the detection threshold of the receiver, that is, the electronic reconnaissance frequency measurement receiver cannot detect the existence of the detection signal, at this time, the signal can be considered an anti-detection signal. When the energy of the detection signal at the location of the electronic reconnaissance frequency measurement receiver is higher than the detection threshold of the receiver, but the relevant parameters of the detection signal cannot be accurately measured by it, at this time, the signal can be considered an anti-parameter measurement signal.

[0003] Compared with traditional analog radio signal frequency measurement receivers, single-bit digital frequency measurement receivers not only have characteristics such as high sensitivity and fast frequency measurement speed, but also have advantages such as small volume, low hardware complexity, large instantaneous bandwidth, and strong ability to process simultaneously arriving signals. They can quickly detect the relevant parameters of various forms of radio detection signals. Since its performance in all aspects has reached or even exceeded that of traditional analog frequency measurement receivers and has broad development and application prospects. Therefore, the present invention targets single-bit digital frequency measurement receivers and designs a low-intercept radio detection signal to reduce the risk of radio detection signals being intercepted by the enemy and enhance the ability of the equipment to defend against enemy interference during operation.

[0004] Currently, the design of low-intercept detection signals mainly targets traditional analog frequency measurement receivers, such as instantaneous frequency measurement receivers, superheterodyne receivers, etc. Since the working principles of single-bit digital frequency measurement receivers and traditional analog frequency measurement receivers are different, the low-intercept performance of the low-intercept detection signals designed for traditional frequency measurement receivers is greatly reduced when facing single-bit digital frequency measurement receivers, and some even completely fail, and the safety of radio detection equipment during actual combat cannot be effectively guaranteed. And the current research on low-intercept detection signals designed for single-bit digital frequency measurement receivers is still in its infancy. Summary of the Invention

[0005] Aiming at the problem that the low-intercept detection signal designed based on the traditional analog frequency measurement receiver at the current stage has a reduced or ineffective low-intercept performance when facing the reconnaissance of a single-bit digital frequency measurement receiver, seriously threatening the safety of the equipment, and the lack of research results in the relevant research fields, the present invention provides a design method for a broadband multi-carrier simultaneous arrival low-intercept detection signal based on orthogonal frequency division multiplexing modulation technology. The designed detection signal has good low-intercept performance, can effectively reduce the risk of the detection signal being intercepted by a single-bit digital frequency measurement receiver, and improve the ability of the equipment to defend against enemy interference during the working process.

[0006] To achieve the above object, the present invention provides a design method for a low-intercept signal for abnormal defense of short-range detection high-end equipment, including the following steps:

[0007] Step 1: Design the number of sub-carriers and the frequency interval of the orthogonal frequency division multiplexing signal;

[0008] Step 2: Design a chaotic function to generate a random sequence;

[0009] Step 3: Use a 16-point constellation diagram to transform the random sequence into the rectangular coordinate system to generate modulation information;

[0010] Step 4: Use multiple groups of modulation information to perform sub-carrier amplitude modulation on the orthogonal frequency division multiplexing signal respectively to generate a baseband signal;

[0011] Step 5: Modulate the baseband signal onto multiple carrier frequencies with a certain frequency interval respectively;

[0012] Step 6: Distribute the modulated signals to each antenna of the multi-transmit and multi-receive detection equipment respectively and transmit them outward simultaneously to obtain a broadband multi-carrier simultaneous arrival low-intercept detection signal.

[0013] A further technical solution lies in: The method for designing the number of sub-carriers and the interval of the orthogonal frequency division multiplexing signal is as follows:

[0014] The baseband orthogonal frequency division multiplexing signal can be expressed as:

[0015]

[0016] In formula (1), a k , b k are the sub-carrier amplitudes of the orthogonal frequency division multiplexing signal, N is the number of sub-carriers, f k =kΔf is the frequency of the k-th sub-carrier of the baseband orthogonal frequency division multiplexing signal, Δf is the frequency difference between adjacent sub-carriers, and at this time the bandwidth of each baseband detection signal is B = NΔf.

[0017] Compared with the application of the orthogonal frequency division multiplexing signal in the field of communication systems, the detection signal of this equipment does not need to transmit specific information, but ak , b k As the sub - carrier amplitude of the orthogonal frequency - division multiplexing (OFDM) signal, it plays an important role in improving the time - domain waveform of the detection signal and affecting the distribution of the spectral peak, etc.

[0018] A further technical solution lies in: The design method of the chaotic function for generating the random sequence is as follows:

[0019] The expression of the designed chaotic function is shown in Equation (2):

[0020]

[0021] In Equation (2), x n is the initial value of the chaotic function, and r is the fractal coefficient of the chaotic function.

[0022] Compared with the classical chaotic function, the designed chaotic function is more uniformly distributed in the interval [-1, 1], and is more sensitive to the initial value x n of the function and the fractal coefficient r. By changing the function initial value and the fractal coefficient, random sequences of any length can be generated to meet the requirements of modulating the sub - carrier amplitude of the orthogonal frequency - division multiplexing signal.

[0023] A further technical solution lies in: The method of using a 16 - point constellation diagram to group every 4 digits of the random sequence generated by the chaotic function and transform it into the rectangular coordinate to generate the sub - carrier amplitude modulation information is as follows:

[0024] Quantize the original random sequence generated by the chaotic function. Data less than or equal to 0 is quantized to 0, and data greater than 0 is quantized to 1. The sequence generated by the original chaotic function is transformed into a random 0, 1 sequence. Using a 16 - point constellation diagram, every 4 digits are grouped as a set, and the 0, 1 sequence is transformed into the rectangular coordinate. The horizontal and vertical coordinates corresponding to each group of digits in the rectangular coordinate are the modulation information of the sub - carrier amplitude of the orthogonal frequency - division multiplexing signal, further expanding the types of modulation information and enhancing the randomness of the time - domain and frequency - domain waveforms of the synthesized signal.

[0025] A further technical solution lies in: The method of using different modulation information to perform amplitude modulation on the sub - carriers of multiple orthogonal frequency - division multiplexing signals to generate multiple groups of base - band detection signals is as follows:

[0026]

[0027] At the same time, according to Parseval's energy conservation theorem formula:

[0028]

[0029] In Equation (6), x(n) is the time-domain sampling point of the signal, X(k) is the frequency-domain data generated after the time-domain sampling points of the signal are subjected to FFT, and N is the number of points of the FFT. By continuously changing the amplitude modulation information of each subcarrier of the orthogonal frequency division multiplexing signal, the time-domain waveform of the synthesized signal will continuously change, and the peak value of the corresponding spectrogram of the signal will also randomly change within the signal bandwidth.

[0030] A further technical solution lies in: The method of modulating different baseband orthogonal frequency division multiplexing subcarrier amplitude modulation signals to different carrier frequencies respectively and synthesizing a wideband multi-carrier to reach the detection signal simultaneously is as follows:

[0031]

[0032] Finally, the expression of the wideband multi-carrier low-intercept detection signal that can be obtained is:

[0033] S(t) = s1(t) + s2(t) +... + s n (t)(10)

[0034] For the modulation carrier frequencies of signals s1(t), s2(t), …, s n (t) The selection should follow the following principles:

[0035] (1) The difference between the frequency after the first subcarrier of signal s2(t) is modulated and the frequency after the last subcarrier of signal s1(t) is modulated should be equal to the frequency difference Δf between the subcarriers of the orthogonal frequency division multiplexing signal.

[0036] (2) The difference between the frequency after the first subcarrier of signal s3(t) is modulated and the frequency after the last subcarrier of signal s2(t) is modulated should be equal to the frequency difference Δf between the subcarriers of the orthogonal frequency division multiplexing signal.

[0037] (3) The difference between the frequency after the first subcarrier of signal s n (t) is modulated and the frequency after the last subcarrier of signal s n-1 (t) is modulated should be equal to the frequency difference Δf between the subcarriers of the orthogonal frequency division multiplexing signal.

[0038] A further technical solution lies in: The method of distributing the obtained n-channel modulated orthogonal frequency division multiplexing signals to each antenna of the multi-transmitter and multi-receiver detection equipment respectively to obtain the transmitted signal is as follows:

[0039] According to the number of antenna array elements of the multi-transmission and multi-reception detection equipment and the number of obtained orthogonal frequency division multiplexing (OFDM) baseband signals, multiple groups of OFDM signals are allocated to each antenna. For example, if the number of array elements is n and the number of subcarriers of each OFDM signal is N, then each antenna transmits a signal containing N subcarriers (each antenna transmits 1 OFDM signal), and the total number of subcarriers of the synthesized detection signal is n*N.

[0040] A further technical solution lies in: the method for evaluating the reconnaissance performance of an anti-electronic reconnaissance frequency measurement receiver for a broadband multi-carrier simultaneous arrival detection signal is as follows:

[0041] First, model the electronic reconnaissance frequency measurement receiver (single-bit digital frequency measurement receiver), and then input the broadband multi-carrier simultaneous arrival detection signal into the model of the frequency measurement receiver to obtain the signal frequency detection result.

[0042] The beneficial effects produced by adopting the above technical solution are as follows: the method uses the designed chaotic function to generate a random sequence, transforms the random sequence into the rectangular coordinate through a 16-point constellation diagram, generates multiple groups of modulation information to perform amplitude modulation on the subcarriers of the OFDM signal, and finally distributes the modulated OFDM signals to each antenna of the multi-transmission and multi-reception detection equipment for transmission, jointly forming n*N paths of simultaneous arrival signals, which not only reduces the peak value of the instantaneous power spectral density of the detection signal but also improves the performance of the detection signal against the monitoring of the digital frequency measurement receiver. Further reduces the risk of being targeted by the enemy during the operation of the equipment, enhances the active defense ability, can be applied to the field of modern electronic warfare radio countermeasures, and has broad development prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0044] Figure 1 is a schematic flow chart of the low-intercept detection signal design method in an embodiment of the present invention;

[0045] Figure 2 is a schematic diagram of a 16-point constellation diagram for transforming the amplitude modulation information of subcarriers in an embodiment of the present invention;

[0046] Figure 3 is a schematic diagram of synthesizing a broadband multi-carrier detection signal from 4 paths of OFDM signals in an embodiment of the present invention;

[0047] Figure 4 is a comparison diagram of the peak value of the instantaneous power spectral density of a broadband multi-carrier detection signal synthesized from 4 paths of OFDM signals in an embodiment of the present invention and a linear frequency modulation signal with the same bandwidth;

[0048] Figure 5It is the spectrum simulation result diagram of the broadband multi-carrier detection signal synthesized by 4-channel orthogonal frequency division multiplexing signals in the embodiments of the present invention, and is output by a single-bit digital frequency measurement receiver;

[0049] Figure 6 It is the result statistics of the carrier frequency measurement of the low-intercept detection signal by the single-bit digital frequency measurement receiver in the embodiments of the present invention under different sub-carrier amplitude modulation information. Specific implementation manners

[0050] The following describes the technical solutions in the embodiments of the present invention clearly and completely with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Those skilled in the art may make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0052] The embodiments of the present invention disclose a design method for a low-intercept signal for abnormal defense of short-range detection high-end equipment, which relates to the field of modern electronic warfare radio countermeasure technology. For the digital radio signal frequency measurement receiver commonly used in electronic warfare, a low-intercept detection signal is designed to reduce the risk of the detection signal being intercepted by the enemy's electronic reconnaissance system during operation, so as to improve the security of the equipment. First, a chaotic function is designed and used to generate a set of random sequences; secondly, the 16-point constellation diagram is used to transform the random sequences into the rectangular coordinates to generate sub-carrier modulation information; then, multiple groups of modulation information are used to perform sub-carrier amplitude modulation on the orthogonal frequency division multiplexing signals respectively to generate baseband signals; finally, the baseband signals are modulated to different carrier frequencies respectively and transmitted outward simultaneously through different antennas by using the multiple-transmitter and multiple-receiver technology. The designed detection signal appears as n*N channels of signals arriving simultaneously for the single-bit digital frequency measurement receiver in the time domain. In addition to having a large bandwidth and a low instantaneous power spectral density peak, it can also effectively affect the measurement process of the carrier frequency of the signal by the single-bit digital frequency measurement receiver, making the result with a large error output by it, reducing the probability of being intercepted by the frequency measurement receiver, and further reducing the risk of being targeted by the enemy during the operation of the equipment, and enhancing the active defense ability.

[0053] As Figure 1 shown, the embodiments of the present invention disclose a design method for a low-intercept signal for abnormal defense of short-range detection high-end equipment, including the following steps:

[0054] Step 1: Design the number of subcarriers and frequency interval of the orthogonal frequency division multiplexing (OFDM) signal;

[0055] Step 2: Design a chaotic function to generate a random sequence;

[0056] Step 3: Use a 16-point constellation diagram to transform the random sequence into the rectangular coordinate system to generate modulation information;

[0057] Step 4: Use multiple groups of modulation information to perform subcarrier amplitude modulation on the OFDM signal respectively to generate a baseband signal;

[0058] Step 5: Modulate the baseband signal onto multiple carrier frequencies with a certain frequency interval respectively;

[0059] Step 6: Distribute the modulated signals to each antenna of the multiple-input multiple-output (MIMO) detection equipment respectively and transmit them outward simultaneously to obtain a wideband multi-carrier simultaneous arrival low-intercept detection signal.

[0060] The above steps are described in detail as follows:

[0061] The method for designing the number of subcarriers and the interval of the OFDM signal in step 1) is as follows:

[0062] The baseband OFDM signal can be expressed as

[0063]

[0064] In formula (1), a k , b k are the subcarrier amplitudes of the OFDM signal, N is the number of subcarriers, f k = kΔf is the frequency of the k-th subcarrier of the baseband OFDM signal, Δf is the frequency difference between adjacent subcarriers, and the bandwidth of each baseband detection signal is B = NΔf at this time.

[0065] Compared with the application of the OFDM signal in the field of communication systems, the detection signal of this equipment does not need to transmit specific information, but a k , b k as the subcarrier amplitudes of the OFDM signal play an important role in improving the time-domain waveform of the detection signal and affecting the spectral peak distribution, etc.

[0066] The design method of the chaotic function for generating a random sequence in step 2) is as follows:

[0067] The expression of the designed chaotic function is shown in formula (2):

[0068]

[0069] In formula (2), x n$x_0$ is the initial value of the chaotic function, and $r$ is the fractal coefficient of the chaotic function.

[0070] Compared with the classical chaotic function, the designed chaotic function is more uniformly distributed in the interval [-1, 1], and is more sensitive to the initial value $x$ of the function n and the fractal coefficient $r$. By changing the function initial value and the fractal coefficient, different random sequences of any length can be generated to meet the requirements for modulating the sub-carrier amplitude of the orthogonal frequency division multiplexing signal.

[0071] In step 3), the random sequence generated by the chaotic function is grouped into sets of 4 numbers each using a 16-point constellation diagram and transformed into the rectangular coordinate system to generate the sub-carrier amplitude modulation information:

[0072] The original random sequence generated by the chaotic function is quantized. Data less than or equal to 0 is quantized to 0, and data greater than 0 is quantized to 1. The sequence generated by the original chaotic function is transformed into a random 0, 1 sequence. Using a 16-point constellation diagram, every 4 numbers form a group, and the 0, 1 sequence is transformed into the rectangular coordinate system. The horizontal and vertical coordinates corresponding to each group of numbers in the rectangular coordinate system are the modulation information of the sub-carrier amplitude of the orthogonal frequency division multiplexing signal, further expanding the types of modulation information and enhancing the randomness of the time-domain and frequency-domain waveforms of the synthesized signal. Figure 2 Fig. 13 is a schematic diagram of a 16-point constellation for generating sub-carrier amplitude modulation information.

[0073] In step 4), the sub-carriers of multiple orthogonal frequency division multiplexing signals are respectively amplitude-modulated using different modulation information to generate multiple groups of baseband detection signals:

[0074]

[0075]

[0076] At the same time, according to Parseval's energy conservation theorem formula:

[0077]

[0078] In formula (6), $x(n)$ is the time-domain sampling point of the signal, $X(k)$ is the frequency-domain data generated after the time-domain sampling points of the signal are subjected to FFT, and $N$ is the number of points of FFT. By continuously changing the amplitude modulation information of each sub-carrier of the orthogonal frequency division multiplexing signal, the time-domain waveform of the synthesized signal will continuously change, and the peak value of the corresponding frequency spectrum diagram of the signal will also randomly change within the signal bandwidth.

[0079] In step 6), different baseband orthogonal frequency division multiplexing sub-carrier amplitude modulation signals are respectively modulated to different carrier frequencies, and the method for synthesizing a wideband multi-carrier to simultaneously arrive at the detection signal is as follows:

[0080]

[0081] Finally, the expression of the broadband multi-carrier low-intercept detection signal can be obtained as follows:

[0082] S(t) = s1(t) + s2(t) +... + s n (t)(12)

[0083] For the modulation carrier frequencies of signals s1(t), s2(t), …, s n (t) The selection should follow the following principles:

[0084] (1) The difference between the frequency after the first sub-carrier modulation of signal s2(t) and the frequency after the last sub-carrier modulation of signal s1(t) should be equal to the frequency difference Δf between the sub-carriers of the orthogonal frequency division multiplexing signal.

[0085] (2) The difference between the frequency after the first sub-carrier modulation of signal s3(t) and the frequency after the last sub-carrier modulation of signal s2(t) should be equal to the frequency difference Δf between the sub-carriers of the orthogonal frequency division multiplexing signal.

[0086] (3) The difference between the frequency after the first sub-carrier modulation of signal s n (t) and the frequency after the last sub-carrier modulation of signal s n-1 (t) should be equal to the frequency difference Δf between the sub-carriers of the orthogonal frequency division multiplexing signal.

[0087] A further technical solution is as follows: The obtained n-channel modulated orthogonal frequency division multiplexing signals are respectively allocated to each antenna of the multiple-input multiple-output detection equipment, and the method for obtaining the transmitted signal is as follows:

[0088] According to the number of antenna array elements of the multiple-input multiple-output detection equipment and the number of obtained orthogonal frequency division multiplexing baseband signals, multiple groups of orthogonal frequency division multiplexing signals are allocated to each antenna. For example, if the number of array elements is n and the number of sub-carriers of each orthogonal frequency division multiplexing signal is N, then each antenna transmits a signal containing N sub-carriers (each antenna transmits 1 orthogonal frequency division multiplexing signal), and the total number of sub-carriers of the synthesized detection signal is n*N.

[0089] Figure 3 is a schematic diagram of synthesizing a broadband multi-carrier detection signal from 4-channel orthogonal frequency division multiplexing signals; Figure 4 is a comparison of the peak of the instantaneous power spectral density between the synthesized 4-channel orthogonal frequency division multiplexing signals and the linear frequency modulation signal under the same conditions; Figure 5 is the spectrum simulation result output after the synthesized 4-channel orthogonal frequency division multiplexing signals pass through a single-bit digital frequency measurement receiver.

[0090] A further technical solution lies in that: the method for evaluating the reconnaissance performance of an anti-electronic reconnaissance frequency measurement receiver for a broadband multi-carrier simultaneous arrival detection signal is as follows:

[0091] First, model the electronic reconnaissance frequency measurement receiver (single-bit digitized frequency measurement receiver), and then input the broadband multi-carrier simultaneous arrival detection signal into the model of the frequency measurement receiver to obtain the signal frequency detection result.

[0092] For the low-intercept detection signal under different modulation information, the carrier frequency measurement results of the frequency measurement receiver are as Figure 6 shown.

Claims

1. A method for designing a short-range detection method for high-end equipment abnormality defense and low interception signal, characterized in that The steps include: Design the number of subcarriers and frequency spacing of OFDM signals; Design chaotic functions to generate random sequences; The random sequence is transformed into rectangular coordinates using a 16-point constellation diagram to generate modulation information; Using multiple groups of modulation information, the subcarrier amplitude modulation is performed on the OFDM signal to generate a baseband signal; Modulate the baseband signal onto multiple carrier frequencies with certain frequency intervals; The modulated signal is distributed to each antenna of the multi-transmitter and multi-receiver detection equipment respectively, and transmitted outward at the same time to obtain a broadband multi-carrier low intercept detection signal that arrives at the same time.

2. The method for designing a low interception signal for short-range detection of high-end equipment abnormality defense as claimed in claim 1, characterized in that: The method for designing the number and spacing of subcarriers of OFDM signals is as follows: The expression of baseband OFDM signal is: In formula (1), a k , b k is the subcarrier amplitude of the OFDM signal, N is the number of subcarriers, f k =kΔf is the frequency of the kth subcarrier of the baseband OFDM signal, Δf is the frequency difference between adjacent subcarriers, and the bandwidth of each baseband detection signal is B=NΔf. Compared with the application of OFDM signals in the field of communication systems, the detection signal of this equipment does not need to transmit specific information, but a k , b k As the subcarrier amplitude of the OFDM signal, it plays an important role in improving the time domain waveform of the detection signal and affecting the spectrum peak distribution.

3. The method for designing a low interception signal for short-range detection of high-end equipment abnormality defense as claimed in claim 2, characterized in that: The chaotic function design method for generating random sequences is as follows: The expression of the designed chaos function is shown in formula (2): In formula (2), x n is the initial value of the chaotic function, and r is the fractal coefficient of the chaotic function. Compared with the classical chaotic function, the designed chaotic function is more evenly distributed in the interval [-1,1], and for the initial value x of the function n And the fractal coefficient r has a strong sensitivity. By changing the initial value of the chaotic function and the fractal coefficient, different random sequences of arbitrary length can be generated to meet the needs of modulating the subcarrier amplitude of the orthogonal frequency division multiplexing signal.

4. The method for designing a low interception signal for short-range detection of high-end equipment abnormality defense as claimed in claim 3 is characterized in that: The random sequence generated by the chaotic function is transformed into rectangular coordinates using a 16-point constellation diagram, with each group of 4 numbers, to generate subcarrier amplitude modulation information. The original random sequence generated by the chaotic function is quantized, and the data less than or equal to 0 is quantized to 0, and the data greater than 0 is quantized to 1. The sequence generated by the original chaotic function is transformed into a random sequence of 0 and 1. Using the 16-point constellation diagram, each 4 numbers are grouped together to transform the 0 and 1 sequence into rectangular coordinates. The horizontal and vertical coordinates corresponding to each group of numbers in the rectangular coordinates are the modulation information of the subcarrier amplitude of the orthogonal frequency division multiplexing signal, which further expands the types of modulation information and enhances the randomness of the waveform of the synthetic signal in the time domain and frequency domain.

5. The method for designing a low interception signal for short-range detection of high-end equipment abnormality defense as claimed in claim 4 is characterized in that: The subcarriers of multiple OFDM signals are amplitude modulated using different modulation information to generate multiple groups of baseband detection signals: At the same time, according to the Pasval energy conservation theorem: In formula (6), x(n) is the time domain sampling point of the signal, X(k) is the frequency domain data generated by the signal time domain sampling point after FFT, and N is the number of FFT points. By continuously changing the amplitude modulation information of each subcarrier of the OFDM signal, the time domain waveform of the synthesized signal will continue to change, and the peak value of the spectrum graph corresponding to the signal will also change randomly within the signal bandwidth.

6. The method for designing a low interception signal for short-range detection of high-end equipment abnormality defense as claimed in claim 5, characterized in that: The method of modulating different baseband OFDM subcarrier amplitude modulation signals to different carrier frequencies to synthesize a broadband multi-carrier detection signal that arrives at the same time is as follows: Finally, the expression of broadband multi-carrier low intercept detection signal can be obtained as: S(t)=s1(t)+s2(t)+...+s n (t) (10) For signals s1(t), s2(t), ..., s n (t) modulated carrier frequency The selection should follow the following principles: (1) The difference between the frequency of the first subcarrier modulated by signal s2(t) and the frequency of the last subcarrier modulated by signal s1(t) must be equal to the frequency difference Δf between the subcarriers of the OFDM signal. (2) The difference between the frequency of the first subcarrier modulated by signal s3(t) and the frequency of the last subcarrier modulated by signal s2(t) must be equal to the frequency difference Δf between the subcarriers of the OFDM signal. (3)Signal s n (t) The frequency after the first subcarrier is modulated, which is consistent with the signal s n-1 (t) The frequency difference of the last subcarrier after modulation must be equal to the frequency difference Δf between the subcarriers of the OFDM signal.

7. The method for designing a low interception signal for short-range detection of high-end equipment abnormality defense as claimed in claim 6, characterized in that: The obtained n-channel modulated OFDM signals are respectively distributed to the antennas of the multi-transmit multi-receive detection equipment to obtain the transmission signal as follows: According to the number of antenna array elements of the multi-transmit multi-receive detection equipment and the number of obtained OFDM baseband signals, multiple groups of OFDM signals are allocated to each antenna. For example, if the number of array elements is n, the number of subcarriers of each OFDM signal is N, and the signal transmitted by each antenna contains N subcarriers (each antenna transmits 1 OFDM signal), the total number of subcarriers of the composite detection signal is n*N.

8. The method for designing a low interception signal for short-range detection of high-end equipment abnormality defense as claimed in claim 7, characterized in that: The method for evaluating the reconnaissance performance of a receiver for anti-electronic reconnaissance frequency measurement of broadband multi-carrier simultaneous arrival detection signals is as follows: Firstly, the electronic reconnaissance frequency measurement receiver (single-bit digital frequency measurement receiver) is modeled, and then the broadband multi-carrier detection signal simultaneously arriving at the frequency measurement receiver is input into the model to obtain the signal frequency detection result.

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