Interference detection integrated signal design method based on OCDM

Abstract

The invention provides an OCDM-based interference detection integrated signal design method. The method comprises the following implementation steps: constructing an application scene of an interference detection integrated signal; after discrete sampling is carried out on the linear frequency modulation signal, OCDM and discrete Fresnel inverse transformation are carried out; and carrying out time domain compounding on the generated OCDM time domain discrete signal and the interference signal. According to the invention, the orthogonal frequency modulation division multiplexing (OCDM) is carried out on the discrete frequency modulation signal to obtain a plurality of OCDM effective subcarriers with time-frequency orthogonal characteristics, the dependence on time-frequency synchronization in the prior art is avoided, the anti-interference capability is stronger, and the time domain superposition is carried out on each OCDM time domain discrete signal and the interference signal of the corresponding modulation symbol, so that the time domain superposition of the OCDM time domain discrete signal and the interference signal of the modulation symbol corresponding to the OCDM time domain discrete signal is realized. The symbol information is hidden in the dynamic frequency modulation parameter while the anti-interference advantage of the OCDM signal is ensured, the frequency spectrum of the integrated signal has no periodic characteristic, and the concealment of the integrated signal is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of radar technology, specifically relating to an integrated signal design method for interference detection based on OCDM, which can be applied to miniaturized UAV platforms that integrate detection and interference functions. Background Technology

[0002] Integrated jamming and detection signal is a composite signal that combines target detection and jamming functions. It achieves multi-functional synergy through signal waveform design and processing. Its core principle is to combine detection and jamming components within a single signal, balancing detection and electronic countermeasures capabilities to enhance the overall effectiveness of the radar system.

[0003] The technical approach for the integrated interference detection signal design is as follows: First, the received linear frequency modulated signal is discretely sampled in the time domain to obtain a discrete sequence. Then, the sampled signal is modulated to generate a frequency domain modulated signal. After that, a discrete Fourier transform is performed to obtain a discrete time domain modulated signal. At the same time, the discrete sequence of the linear frequency modulated signal is frequency offset forwarded and interference modulated to obtain a discrete time domain interference signal with deceptive interference effect. Finally, the modulated signal and the interference signal are superimposed in the time domain according to the one-to-one correspondence of the sampling points to form an integrated composite signal with both detection and interference functions.

[0004] To overcome the shortcomings of existing integrated radar jamming detection signals, such as poor anti-jamming capability and low concealment, patent application CN118330574A, entitled "CZC-OFDM Integrated Jamming Detection Signal Generation Method, Device, Program Product, and Medium," discloses a method for designing an integrated radar jamming detection signal. This method chaotically transforms a ZC sequence based on a chaotic binary phase sequence, and then modulates the chaotically generated CZC sequence with OFDM to obtain a CZC-OFDM integrated jamming detection signal. This method increases the pseudo-randomness of the signal's spectrum and time-frequency response on the basis of generating a broadband signal, thus achieving better anti-jamming capability. However, because the fixed subcarrier spacing of the OFDM signal results in a periodic spectrum, it is easily identified as an artificially modulated signal by non-cooperative spectrum analysis equipment. Furthermore, the anti-jamming capability of the CZC sequence depends on strict time-frequency synchronization, resulting in relatively poor concealment and anti-jamming capability of the integrated signal. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the existing technologies by providing an integrated signal design method for interference detection based on OCDM, which solves the technical problems of poor anti-interference capability and low concealment in the existing technologies.

[0006] To achieve the above objectives, the technical solution adopted by the present invention includes the following steps:

[0007] (1) Constructing an integrated signal for interference detection:

[0008] An application scenario is constructed, which includes UAVs distributed in three-dimensional space and equipped with an integrated interference detection system, as well as ground-based networked radars distributed on the ground that are both interfered with and detected. The integrated interference detection system includes a signal receiving module, an interference generation module, a signal transmission module, and a data processing module. The linear frequency modulated signal transmitted by the ground-based networked radar is S.

[0009] (2) The integrated interference detection system performs discrete sampling of the linear frequency modulated signal:

[0010] The data processing module samples the linear frequency modulated signal S received by the signal receiving module N times to obtain N discrete frequency modulated signals, where the nth discrete frequency modulated signal is s(n), n∈[1,N], N≥2;

[0011] (3) The integrated interference detection system performs OCDM and discrete Fresnel inverse transform on each discrete frequency modulated signal:

[0012] The integrated interference detection system performs orthogonal frequency modulation division multiplexing (OCDM) on each discrete frequency modulation signal s(n) to obtain M effective OCDM subcarriers containing modulation symbols, and performs discrete inverse Fresnel transform on each effective OCDM subcarrier x(m) to obtain the OCDM time-domain discrete signal p(m) corresponding to x(m), where m∈[1,M], M≥2;

[0013] (4) The integrated interference detection system generates interference signals:

[0014] The interference generation module performs frequency offset forwarding on each discrete frequency modulation signal s(n), and performs OCDM parameterized interference modulation on each forwarded frequency shift component signal s(n)' to obtain M interference signals embedded with modulation symbols, where the m-th interference signal is s(m).

[0015] (5) The integrated interference detection system generates an integrated interference detection signal:

[0016] The interference generation module combines each OCDM time-domain discrete signal p(m) and its corresponding modulation symbol interference signal s(m) in the time domain to obtain the integrated OCDM interference detection signal O(m).

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] This invention performs orthogonal frequency modulation multiplexing (OCDM) on each discrete frequency modulation signal to obtain multiple effective OCDM subcarriers with time-frequency orthogonal characteristics. This avoids the dependence on time-frequency synchronization in existing technologies and has stronger anti-interference capabilities. Furthermore, by superimposing the time-domain discrete signals of each OCDM and the interference signals of their corresponding modulation symbols in the time domain, the anti-interference advantages of the OCDM signal are guaranteed, while the symbol information is hidden in the dynamic frequency modulation parameters. The spectrum of the integrated signal has no periodic characteristics, which effectively improves the concealment of the integrated signal. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the implementation of the present invention.

[0020] Figure 2 This is a schematic diagram illustrating the integrated interference detection signal application scenario of the present invention. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] Reference Figure 1 The present invention includes the following steps:

[0023] Step 1) Construct as follows Figure 2 The application scenarios of the integrated interference detection signal shown are as follows:

[0024] The system constructs an application scenario that includes UAVs distributed in three-dimensional space and equipped with an integrated interference detection system, as well as ground-based networked radars distributed on the ground for interference and detection. When the integrated interference detection system receives an external signal, it generates interference and modulates the received signal, and transmits the resulting integrated interference detection signal to the ground-based networked radar for interference. At the same time, it receives the echo signal of the transmitted integrated signal, processes the echo signal to obtain the speed and distance information of the ground-based networked radar.

[0025] The integrated interference detection system includes: a signal receiving module that receives signals transmitted by a ground-based networked radar; an interference generation module that generates interference signals based on the received signals; a data processing module that performs OCDM modulation on the received signals; and a signal transmitting module that transmits integrated interference detection signals.

[0026] The signal S transmitted by the ground-based network radar is a linear frequency modulated signal;

[0027] Step 2) The integrated interference detection system performs discrete sampling of the linear frequency modulated signal:

[0028] When the linear frequency modulated signal S transmitted by the ground network radar is received by the UAV, the signal receiving module in the integrated interference detection system transmits the received signal to the data processing module. The data processing module performs N time-domain discrete sampling on the received linear frequency modulated signal S to obtain N discrete frequency modulated signals in the time domain, where the nth discrete frequency modulated signal is s(n), n∈[1,N], and in this embodiment N≥2;

[0029] The expression for the nth discrete frequency modulated signal s(n) is:

[0030]

[0031] Among them, A n f represents the magnitude of s(n). c T s μ and μ represent the carrier frequency, sampling frequency, and modulation slope of the linear frequency modulated signal s, respectively; e represents the base of the natural logarithm; and j represents the imaginary unit.

[0032] Step 3) The integrated interference detection system performs OCDM and discrete Fresnel inverse transform on each discrete frequency modulated signal:

[0033] The integrated interference detection system performs orthogonal frequency modulation division multiplexing (OCDM) on each discrete frequency modulation signal s(n). The implementation steps are as follows:

[0034] A discrete Fresnel transform is performed on each discrete frequency modulated signal s(n) to convert the discrete frequency modulated signal from the time domain to the OCDM modulation domain. Then, OCDM symbols are loaded onto each frequency domain preprocessed signal x(n) obtained by the transformation, and the modulation symbols are mapped to the selected frequency domain preprocessed signal to obtain M effective OCDM subcarriers containing modulation symbols.

[0035] Because the discrete frequency modulated signal is mapped to a set of time-frequency two-dimensional orthogonal OCDM subcarriers after the discrete Fresnel transform, the time-frequency two-dimensional orthogonality characteristic allows the OCDM signal to remain orthogonal under Doppler frequency offset and multipath delay. That is, the OCDM signal naturally resists Doppler frequency offset and multipath effects. Therefore, the OCDM signal significantly reduces its dependence on time-frequency synchronization while giving it a strong anti-interference capability.

[0036] The expression for each frequency domain preprocessed signal x(n) is as follows:

[0037]

[0038] The expression for the m-th effective OCDM subcarrier x(m) is:

[0039]

[0040] Where, dm The modulated symbol is M, the total number of effective subcarriers is M, and the index of the corresponding effective subcarrier is m. β m B represents the frequency modulation slope of each modulation symbol, and B represents the bandwidth of the linear frequency modulated signal s.

[0041] The data processing module performs a discrete inverse Fresnel transform on each effective OCDM subcarrier x(m) to obtain the corresponding OCDM time-domain discrete signal p(m), where m∈[1,M], and in this embodiment M≥2.

[0042] Where x(m) corresponds to the OCDM time-domain discrete signal p(m), the expression of which is:

[0043]

[0044] Step 4) The integrated interference detection system generates interference signals:

[0045] The interference generation module performs frequency offset forwarding on each discrete frequency modulated signal s(n), and achieves spectrum shifting through complex exponential modulation, preserving the time-frequency characteristics of the original signal. Then, it performs OCDM parameterized interference modulation on each frequency shift component signal s(n)' obtained by forwarding, and embeds the OCDM modulation symbol into the interference signal through frequency modulation slope modulation, realizing the fusion of signal anti-interference and concealment, and obtaining M interference signals with embedded modulation symbols, where the m-th interference signal is s(m).

[0046] The expression for each frequency-shifted component signal s(n)' is:

[0047]

[0048] The expression for each interference signal s(m) embedded with the modulation symbol is:

[0049]

[0050] β s =μ+λd m

[0051] Where λ represents the slope modulation coefficient, A m β s Let represent the amplitude and frequency modulation slope of s(m), respectively.

[0052] Because the sequence lengths of the discrete signal and s(m) in OCDM must be the same during time-domain composite, the number M of interference signals is the same as the number M of the OCDM time-domain discrete signals p(m) obtained in step 3). Furthermore, when performing OCDM parameterized interference modulation on the frequency-shifting component signal s(n)', to avoid slope distortion while ensuring consistent frequency modulation direction, the parameters in the interference signal should satisfy the following formula:

[0053]

[0054] β s >0

[0055] Step 5) The integrated interference detection system generates an integrated interference detection signal:

[0056] The interference generation module performs time-domain composite of each OCDM time-domain discrete signal p(m) and its corresponding parameterized modulated interference signal s(m) to obtain the integrated OCDM interference detection signal O(m), the expression of which is:

[0057]

[0058] Where α represents the interference amplitude coefficient of s(m).

[0059] When combining the OCDM time-domain discrete signal p(m) and its corresponding modulation symbol interference signal s(m), it is necessary to ensure that the two time-domain signals are time-domain aligned and superimposed according to the sampling points. At the same time, the power ratio of the two signals should be dynamically adjusted to avoid excessively strong or weak interference.

[0060] Time-domain alignment must ensure that the sampling interval T between the two signals is: s They are consistent, with their time origins aligned, and both discrete-time signals have the same sequence length.

[0061] When dynamically adjusting the power ratio of two signals: the value of α is set according to the linear range of the integrated system to prevent the amplitude of the composite signal O(m) from exceeding the linear range of the system's digital-to-analog converter power amplifier, thus avoiding signal clipping distortion. The formula for determining the value of α is:

[0062]

[0063] Among them, A max This represents the maximum allowable signal amplitude of the integrated system, and max|·| represents the maximum instantaneous amplitude of the signal.

Claims

1. A method for designing an integrated interference detection signal based on OCDM, characterized in that, Includes the following steps: (1) Constructing an integrated signal for interference detection: An application scenario is constructed, which includes UAVs distributed in three-dimensional space and equipped with an integrated interference detection system, as well as ground-based networked radars distributed on the ground that are both interfered with and detected. The integrated interference detection system includes a signal receiving module, an interference generation module, a signal transmission module, and a data processing module. The linear frequency modulated signal transmitted by the ground-based networked radar is s. (2) The integrated interference detection system performs discrete sampling of the linear frequency modulated signal: The data processing module samples the linear frequency modulated signal s received by the signal receiving module N times to obtain N discrete frequency modulated signals, where the nth discrete frequency modulated signal is s(n), n∈[1,N], N≥2; (3) The integrated interference detection system performs OCDM and discrete Fresnel inverse transform on each discrete frequency modulated signal: The integrated interference detection system performs orthogonal frequency modulation division multiplexing (OCDM) on each discrete frequency modulation signal s(n) to obtain M effective OCDM subcarriers containing modulation symbols, and performs discrete inverse Fresnel transform on each effective OCDM subcarrier x(m) to obtain the OCDM time-domain discrete signal p(m) corresponding to x(m), where m∈[1,M], M≥2; (4) The integrated interference detection system generates interference signals: The interference generation module performs frequency offset forwarding on each discrete frequency modulation signal s(n), and performs OCDM parameterized interference modulation on each forwarded frequency shift component signal s(n)' to obtain M interference signals with embedded modulation symbols, where the m-th interference signal is s(m). (5) The integrated interference detection system generates an integrated interference detection signal: The interference generation module combines each OCDM time-domain discrete signal p(m) and its corresponding parameterized modulated interference signal s(m) in the time domain to obtain the integrated OCDM interference detection signal O(m).

2. The method according to claim 1, characterized in that, The nth discrete frequency modulated signal mentioned in step (2) is s(n), and its expression is: Among them, A n f represents the magnitude of s(n). c T s μ and μ represent the carrier frequency, sampling frequency, and modulation slope of the linear frequency modulated signal s, respectively; e represents the base of the natural logarithm; and j represents the imaginary unit.

3. The method according to claim 2, characterized in that, The integrated interference detection system described in step (3) performs orthogonal frequency modulation division multiplexing (OCDM) on each discrete frequency modulation signal s(n). The steps are as follows: For each discrete frequency modulated signal s(n), a discrete Fresnel transform is performed, and for each frequency domain preprocessed signal x(n) after the discrete Fresnel transform, OCDM symbols are loaded to obtain M effective OCDM subcarriers containing modulation symbols, where:

4. The method according to claim 3, characterized in that, The effective subcarrier x(m) of OCDM mentioned in step (3) is expressed as follows: Where, d m This represents the modulation symbols contained in x(m), where m represents the index of M, and β m Let x(m) represent the frequency modulation slope, and B represent the bandwidth of the linear frequency modulated signal s.

5. The method according to claim 4, characterized in that, The expression for the OCDM time-domain discrete signal p(m) corresponding to x(m) mentioned in step (3) is:

6. The method according to claim 4, characterized in that, Each frequency-shifted component signal s(n)' mentioned in step (4) has the following expression:

7. The method according to claim 4, characterized in that, The expression for the interference signal s(m) for each embedded modulation symbol mentioned in step (4) is: b s =μ+λd m Where λ represents the slope modulation coefficient, A m β s Let represent the amplitude and frequency modulation slope of s(m), respectively.

8. The method according to claim 4, characterized in that, The integrated OCDM interference detection signal O(m) mentioned in step (5) has the following expression: Where α represents the interference amplitude coefficient of s(m), A max This indicates the maximum allowable signal amplitude of the integrated system.

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