A method for JTIDS signal reconnaissance, identification and positioning

Abstract

The application discloses a JTIDS signal reconnaissance identification positioning method, which comprises the following steps: receiving signals through a plurality of parallel receiving channels according to the frequency hopping frequency points of the JTIDS signals; judging whether the pulse width of each received pulse signal conforms to the JTIDS signal characteristics through threshold detection, and obtaining the pulse arrival time of each pulse; sorting the pulses conforming to the JTIDS signal pulse width based on the pulse interval, and obtaining the frequency hopping frequency sequence; realizing the TOA measurement synchronization between the main station and the vice station through frequency point matching; obtaining the time difference between the radiation source signal and each positioning platform based on the synchronized arrival time, and solving the spatial position of the target through the time difference cross positioning method. The application can realize the JTIDS signal reconnaissance identification and positioning through the known frequency hopping frequency point set, pulse width and pulse interval of the JTIDS signal, without the complicated processing process such as MSK detection demodulation, reconnaissance and cracking of soft spread spectrum signal PN code, artificial intelligence algorithm classifier design and the like, so that the system complexity is simplified.

Description

Technical Field

[0001] This invention relates to the field of identification and positioning technology, and in particular to a JTIDS signal detection, identification, and positioning method. Background Technology

[0002] JTIDS is a high-capacity, anti-jamming, and highly secure Joint Tactical Information Distribution System that integrates communication, navigation, and identification functions. It ensures real-time interactive transmission of information between command centers and combat platforms. As a communication carrier for the Link 16 data link, JTIDS is currently widely used on various combat platforms. Therefore, in a combat environment, the real-time, efficient, and accurate interception, identification, search, location, and other applications of JTIDS signals are of significant military importance.

[0003] JTIDS employs multiple techniques, including direct sequence spread spectrum, high-speed frequency hopping, and RS coding, with MSK modulation, exhibiting strong anti-interference and anti-interception capabilities. Extensive research has been conducted by scholars both domestically and internationally on the various techniques and signal characteristics employed by JTIDS. Research focuses primarily on the detection and estimation of frequency-hopping signals, estimation of spread spectrum sequence pseudo-random codes, and identification of MSK modulation schemes. Extractable feature parameters include frequency hopping pattern, pulse width, TOA, modulation scheme, carrier frequency, code rate, and PN code.

[0004] However, while research on JTIDS signal reconnaissance techniques has yielded some results, these studies have not designed corresponding reconnaissance schemes for different application scenarios from a systemic perspective. Depending on the platform's reconnaissance mission, the signal characteristics and technical parameters that need to be measured vary. Therefore, based on the above, it is necessary to design corresponding JTIDS signal reconnaissance and identification systems according to different reconnaissance requirements. Summary of the Invention

[0005] In view of this, the present invention provides a method for detecting, identifying and locating JTIDS signals, which eliminates the need for complex processing such as MSK detection and demodulation, detection and cracking of soft spread spectrum signal PN code, and design of artificial intelligence algorithm classifier. The detection, identification and location of JTIDS signals can be achieved by using the known frequency hopping frequency point set, pulse width and pulse interval of JTIDS signals, thereby simplifying the system complexity.

[0006] This invention discloses a JTIDS signal detection, identification, and localization method, which includes:

[0007] Step 1: Receive the signal through a multi-channel parallel receiving channel based on the frequency hopping point of the JTIDS signal;

[0008] Step 2: Determine whether the pulse width of each received pulse signal conforms to the JTIDS signal characteristics through threshold detection, and obtain the pulse arrival time of each pulse;

[0009] Step 3: Based on the pulse interval, pulses that conform to the pulse width of the JTIDS signal are sorted to obtain the frequency hopping sequence;

[0010] Step 4: Achieve TOA measurement synchronization between the master station and the slave station through frequency matching;

[0011] Step 5: Based on the arrival time after synchronization, obtain the time difference between the arrival of the radiation source signal at each positioning platform, and calculate the target spatial position using the time difference cross-positioning method.

[0012] Further, step 1 includes:

[0013] Step 11: The frequency hopping point set based on the JTIDS signal is prior knowledge. Configure the center frequencies of multiple parallel channels respectively so that the receiving channel corresponds to the frequency hopping point set;

[0014] Step 12: Multi-channel parallel reception channels receive wideband, high-hopping signals with full probability.

[0015] Further, step 12 includes:

[0016] The received signal is converted from analog to digital and then enters each receiving channel. Each receiving channel samples, filters, and extracts the converted signal in sequence.

[0017] Further, step 2 includes:

[0018] A sliding window correlation detection method is used to construct a rectangular window and perform sliding correlation with the received signal. The peak value after correlation operation corresponds to the pulse arrival time, and the pulse width T corresponds to the difference between the points with amplitudes equal to half the pulse peak value.

[0019] Two thresholds are set. The first is the peak detection threshold, used to determine whether a pulse has been detected. Exceeding the peak detection threshold indicates that a signal has been intercepted. A false alarm probability is set. Based on the relationship between the false alarm probability and the threshold, we can obtain:

[0020] (1)

[0021] in, This represents the probability of a false alarm. For noise power, This is the peak detection threshold corresponding to the false alarm probability;

[0022] The second is the pulse width detection threshold, which sets the allowable pulse estimation error range for the system. If the pulse width T satisfies:

[0023] (2)

[0024] The received signal is then considered to be a JTIDS signal.

[0025] Furthermore, if the signal at the center frequency of any channel leaks into adjacent channels due to the reception of multiple parallel receiving channels, and the adjacent channels have outputs at the same arrival time, the interference can be eliminated by comparing the pulse peak magnitudes of each signal.

[0026] Further, step 3 includes:

[0027] Step 31: Concatenate the outputs of all channels after interference removal according to the arrival time sequence of the pulses to obtain the arrival time sequence of all pulses;

[0028] Step 32: Based on the pulse interval of the JTIDS signal, perform a sequence search on the arrival time sequence of all pulses to sort the JTIDS pulse signals and obtain the frequency hopping sequence.

[0029] Further, step 32 includes:

[0030] Step 321: Starting from the first pulse, determine whether there is a pulse at an integer multiple of the pulse interval based on the pulse interval of the JTIDS signal. First, determine whether the interval between the second pulse and the first pulse is less than the pulse interval of the JTIDS signal. If it is less, continue searching for the next pulse. If it is greater than the pulse interval of the JTIDS signal, determine the relationship between the interval between the two pulses and twice the pulse interval, and so on.

[0031] Step 322: If the interval between two pulses is an integer multiple of the pulse interval of the JTIDS signal, then take that pulse as a new starting point and continue the search, repeating step 321 until the sequence search is completed.

[0032] Step 323: If the pulse interval between the pulse found starting from the first pulse and the first pulse is equal to or an integer multiple of the pulse interval of the JTIDS signal, then the found pulse is removed from the original sequence, and a new round of searching is performed based on the arrival time of the remaining pulse sequence; if no pulse is found, then the first pulse is removed, and a new search is started starting from the second pulse, until all sequences are removed before the operation ends; by sorting the pulse intervals, a series of frequency values ​​sorted by the JTIDS signal frequency hopping time, i.e., the pulse arrival time, are extracted from the data of all channels, i.e., the frequency hopping frequency sequence.

[0033] Furthermore, through frequency point mapping, frequency hopping sequences can be converted into data that is easy to transmit;

[0034] The frequency mapping process is as follows: the frequency hopping frequency corresponding to each pulse in the JTIDS pulse signal is in the corresponding frequency hopping channel, and each channel has a channel number. Thus, the frequency hopping frequency sequence is mapped to a series of channel numbers.

[0035] Furthermore, in step 4, the synchronization of TOA measurements between the master station and the slave station through frequency point matching includes:

[0036] The frequency hopping frequency sequence in the master station is sequentially retrieved, and a frequency hopping frequency sequence in the slave station that is the same as the frequency hopping frequency sequence extracted from the master station is searched. If the matching condition is met, the matching ends. If not, the remaining frequency hopping frequency sequences in the master station are traversed until the matching condition is met or the traversal of the frequency hopping frequency sequences in the master station ends. The matching condition is as follows: if P frequency points in two sets of frequency hopping frequency sequences match, it is determined that the two stations receive the same signal. When the two stations meet the matching condition, the starting point of TOA is re-determined based on the position of the pulses of the two stations when they match, thus achieving synchronization of TOA measurement between the two stations.

[0037] Further, step 5 includes:

[0038] Time difference cross-positioning is based on the geometric positioning principle of hyperbolic intersection. By measuring the time difference between the arrival of the radiation source signal at each positioning platform, the time difference determines that the radiation source is located on a spatial hyperboloid with the current positions of the two positioning platforms as the focus. After deploying more than 4 positioning platforms, 3 spatial hyperboloids can be obtained accordingly, and their intersection point is the spatial position of the target radiation source.

[0039] Because of the adoption of the above technical solution, the present invention has the following advantages:

[0040] The beneficial effects of this invention, achieved by employing the above scheme, are as follows: By using broadband RF direct acquisition and channelized reception technology, the detection probability of JTIDS signals in the entire frequency hopping band and time domain is improved; joint sorting and identification of JTIDS signals is realized through dual-threshold signal detection and pulse interval sorting; the measurement accuracy of TOA is improved through multi-cycle cumulative averaging; and TOA measurement synchronization between multiple stations is achieved through frequency point matching. Finally, based on the measured TOA results, multi-station time difference cross-location of the target is completed. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0042] Figure 1This is a flowchart illustrating a JTIDS signal detection, identification, and positioning method according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of the JTIDS signal full probability reception model based on multiple parallel channels according to an embodiment of the present invention;

[0044] Figure 3 This is a flowchart of a signal sorting algorithm based on pulse interval according to an embodiment of the present invention;

[0045] Figure 4 This is a flowchart of the frequency point matching algorithm according to an embodiment of the present invention. Detailed Implementation

[0046] The present invention will be further described in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art should fall within the protection scope of the present invention.

[0047] This invention provides an embodiment of a JTIDS signal detection, identification, and positioning method. The technical solution involves: first, intercepting the JTIDS signal; second, detecting the JTIDS signal based on sliding correlation and eliminating interference from adjacent channels; third, achieving signal sorting based on pulse intervals; fourth, accurately estimating the TOA (Time of Arrival); then, the master station synchronizes the measurement results received from multiple slave stations; finally, the TDOA (Time of Arrival) is calculated to complete the target positioning solution. Figure 1 The diagram shown is a flowchart of the JTIDS signal detection and identification method implemented in this invention. The method includes steps such as multi-channel reception, detection, sorting, TOA estimation, matching synchronization, and location calculation.

[0048] (1) Intercepting JTIDS signals. This embodiment can intercept wideband, high-hopping-rate JTIDS signals in parallel and in real time with full probability. Since the frequency hopping frequency set of the JTIDS signal is prior knowledge, these carrier frequencies can be used to configure the channel center frequency so that the receiving channel corresponds to the frequency set. Figure 2This is a block diagram of the channelized reception system. This embodiment uses direct RF sampling at a sampling rate of 880MHz, employing a CIC filter followed by an FIR filter design, resulting in 51 channels. The CIC filter is a 3-stage cascaded filter with a decimation factor of 11; the FIR filter has a passband cutoff frequency of 2MHz, and considering the filter order, its stopband cutoff frequency is set to 4MHz, with a decimation factor of 5, resulting in a baseband signal data rate of 20MHz. As the JTIDS signal interception scheme in this embodiment, different frequency band divisions and different numbers of multiple channels can be used for signal reception, including filter bank design and decimation factor design. This approach is consistent with the concept of this embodiment, also employing multi-channel, full-channel reception, requiring only adjustments based on the adaptability of hardware and software processing resources.

[0049] JTIDS signal detection based on sliding correlation. Based on the pulse modulation characteristics of the JTIDS signal, 51 filtered channels are monitored and analyzed. Determining whether a signal is a JTIDS signal through threshold detection is one of the key problems and technologies addressed in this embodiment. Considering the characteristic that the JTIDS signal pulse width is always 6.4 microseconds, this embodiment designs a dual-threshold detection method. First, a sliding window correlation detection method is used, constructing a rectangular window to perform sliding correlation with the received signal. The correlation detection involved in this invention can be replaced by other correlation algorithms, such as delay multiplication correlation, frequency doubling correlation, etc., all aiming to obtain the correlation peak for subsequent threshold detection and TOA estimation, and all falling within the energy detection range. The peak value after correlation operation corresponds to the pulse arrival time, and the difference between points with amplitudes equal to half the pulse peak value corresponds to the pulse width T. Two thresholds are designed: the first is the peak detection threshold, setting the false alarm probability. Based on the relationship between the false alarm probability and the threshold, we can obtain:

[0050] (1)

[0051] in, This represents the probability of a false alarm. For noise power, This is the peak detection threshold corresponding to the false alarm probability;

[0052] The second is the pulse width detection threshold, which sets the allowable pulse estimation error range for the system. If the pulse width T satisfies:

[0053] (2)

[0054] The received signal is then considered to be a JTIDS signal.

[0055] The design of the system's multi-channel parallel reception may cause the signal at this frequency to leak into adjacent channels, so that adjacent channels may also have outputs at the same arrival time. Interference can be eliminated by comparing the pulse peak size of each channel.

[0056] Signal sorting based on pulse intervals. The outputs of all channels after interference removal are concatenated according to the arrival time sequence of the pulses to obtain the arrival time sequence of all pulses within a certain time width. Based on the pulse interval (13 microseconds) of the JTIDS signal, the sequence search approach can be used to sort the JTIDS pulse signal. The specific algorithm flow is as follows: Figure 3 As shown. The basic idea of ​​signal sorting is as follows: Starting from the first pulse, determine whether a pulse exists at an integer multiple of the JTIDS signal's pulse interval (PRI). First, check if the interval between the second and first pulses is less than the known PRI. If it is less, continue searching for the next pulse; if it is greater than the known PRI, determine the relationship between the interval between the two pulses and 2 × PRI, and so on. If the interval between the two pulses is an integer multiple of the known PRI (allowing for a certain system tolerance), use that pulse as a new starting point to continue searching, repeating the above process until the current sequence search is completed. If a pulse that meets the conditions is found starting from the first pulse, these pulses are removed from the original sequence, and a new round of searching is performed based on the arrival time of the remaining pulse sequence; if no pulse is found, the first pulse is removed, and a new search begins starting from the second pulse, until all sequences are removed before the operation ends. By sorting the pulse intervals, a series of frequency values ​​sorted by the JTIDS signal's frequency hopping time (pulse TOA) are extracted from the data of all channels, i.e., the frequency hopping frequency sequence. Each pulse corresponds to a frequency hopping frequency in a corresponding frequency hopping channel. Each channel has a channel number. Thus, the frequency hopping frequency sequence can be mapped to a series of channel numbers. This process is called frequency point mapping. Through frequency point mapping, the frequency hopping frequency sequence can be converted into data that is easy to transmit.

[0057] Accurate TOA estimation. The JTIDS signal is a pulse train composed of multiple pulses with constant pulse intervals. By utilizing the periodicity of multiple pulses and averaging over multiple periods, the measurement accuracy can be improved compared to the TOA estimate of a single pulse. times.

[0058] Inter-station synchronization based on frequency matching. The secondary station transmits TOA information with a local timestamp and de-hopping frequency sequence information, resolving the synchronization problem of inter-station TOA measurements through frequency matching. The algorithm flow is as follows: Figure 4As shown. The algorithm sequentially retrieves the frequency hopping frequency sequence from the master station and searches for a frequency hopping frequency sequence in the slave station that matches the currently extracted master station sequence. If the matching condition is met, the matching ends; otherwise, it continues to traverse the remaining frequency hopping frequency sequences in the master station until the matching condition is met or the traversal of the frequency hopping frequency sequences in the master station is complete. A crucial aspect of the algorithm is setting the matching condition. The matching condition is defined as follows: if P frequency points in two sets of frequency hopping frequency sequences match, it can be determined that the two stations are receiving the same signal. When the two stations meet the matching condition, the TOA starting point is re-determined based on the positions of the pulses at the time of matching, thus achieving synchronization of TOA measurements between the two stations. Simulation analysis shows that this frequency point matching scheme is highly feasible and can achieve TOA measurement synchronization between stations through frequency point matching.

[0059] Location Calculation. Based on the measured TOA, the time difference of arrival (TOA) of each station can be obtained. The spatial location of the target can then be calculated using the time difference cross-location method. Time difference cross-location is based on the geometric positioning principle of hyperbolic intersection. By measuring the time difference between the arrival of the radiation source signal at each positioning platform, this time difference determines that the radiation source lies on a spatial hyperboloid with the current positions of the two positioning platforms as foci. After deploying four or more positioning platforms, three spatial hyperboloids can be obtained accordingly, and their intersection point is the spatial location of the target radiation source.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for detecting, identifying, and locating JTIDS signals, characterized in that, include: Step 1: Receive the signal through a multi-channel parallel receiving channel based on the frequency hopping point of the JTIDS signal; Step 2: Determine whether the pulse width of each received pulse signal conforms to the JTIDS signal characteristics through threshold detection, and obtain the pulse arrival time of each pulse; Step 3: Based on the pulse interval, pulses that conform to the pulse width of the JTIDS signal are sorted to obtain the frequency hopping sequence; Step 4: Achieve TOA measurement synchronization between the master station and the slave station through frequency matching; Step 5: Based on the arrival time after synchronization, obtain the time difference between the arrival of the radiation source signal at each positioning platform, and calculate the target spatial position using the time difference cross-positioning method; Step 2 includes: A sliding window correlation detection method is used to construct a rectangular window and perform sliding correlation with the received signal. The peak value after correlation operation corresponds to the pulse arrival time, and the difference between the points with amplitudes equal to half of the pulse peak value corresponds to the pulse width T. Two thresholds are set. The first is the peak detection threshold, used to determine whether a pulse has been detected. Exceeding the peak detection threshold indicates that a signal has been intercepted. A false alarm probability is set. Based on the relationship between the false alarm probability and the threshold, we can obtain: （1） in, This represents the probability of a false alarm. For noise power, This is the peak detection threshold corresponding to the false alarm probability; The second is the pulse width detection threshold, which sets the allowable pulse estimation error range for the system. If the pulse width T satisfies: （2） The received signal is then considered to be a JTIDS signal; Step 3 includes: Step 31: Concatenate the outputs of all channels after interference removal according to the arrival time sequence of the pulses to obtain the arrival time sequence of all pulses; Step 32: Based on the pulse interval of the JTIDS signal, perform a sequence search on the arrival time sequence of all pulses to sort the JTIDS pulse signals and obtain the frequency hopping sequence; Step 32 includes: Step 321: Starting from the first pulse, determine whether there is a pulse at an integer multiple of the pulse interval based on the pulse interval of the JTIDS signal. First, determine whether the interval between the second pulse and the first pulse is less than the pulse interval of the JTIDS signal. If it is less, continue searching for the next pulse. If it is greater than the pulse interval of the JTIDS signal, determine the relationship between the interval between the two pulses and twice the pulse interval, and so on. Step 322: If the interval between two pulses is an integer multiple of the pulse interval of the JTIDS signal, then take that pulse as a new starting point and continue the search, repeating step 321 until the sequence search is completed. Step 323: If the pulse interval between the pulse found starting from the first pulse and the first pulse is equal to or an integer multiple of the pulse interval of the JTIDS signal, then the found pulse is removed from the original sequence, and a new round of searching is performed based on the arrival time of the remaining pulse sequence; if no pulse is found, then the first pulse is removed, and a new search is started starting from the second pulse, until all sequences are removed before the operation ends; by sorting the pulse intervals, a series of frequency values ​​sorted by the JTIDS signal frequency hopping time, i.e., the pulse arrival time, are extracted from the data of all channels, i.e., the frequency hopping frequency sequence. In step 4, the synchronization of TOA measurements between the master station and the slave station through frequency point matching includes: The frequency hopping frequency sequence in the master station is sequentially retrieved, and a frequency hopping frequency sequence in the slave station that is the same as the frequency hopping frequency sequence extracted from the master station is searched. If the matching condition is met, the matching ends. If not, the remaining frequency hopping frequency sequences in the master station are traversed until the matching condition is met or the traversal of the frequency hopping frequency sequences in the master station ends. The matching condition is as follows: if P frequency points in two sets of frequency hopping frequency sequences match, it is determined that the two stations receive the same signal. When the two stations meet the matching condition, the starting point of TOA is re-determined based on the position of the pulses of the two stations when they match, thus achieving synchronization of TOA measurement between the two stations.

2. The method according to claim 1, characterized in that, Step 1 includes: Step 11: The frequency hopping point set based on the JTIDS signal is prior knowledge. Configure the center frequencies of multiple parallel channels respectively so that the receiving channel corresponds to the frequency hopping point set; Step 12: Multi-channel parallel reception channels receive wideband, high-hopping signals with full probability.

3. The method according to claim 2, characterized in that, Step 12 includes: The received signal is converted from analog to digital and then enters each receiving channel. Each receiving channel samples, filters, and extracts the converted signal in sequence.

4. The method according to claim 1, characterized in that, If the signal at the center frequency of any channel is leaked into adjacent channels due to the reception of multiple parallel receiving channels, and the adjacent channels have outputs at the same arrival time, the interference can be eliminated by comparing the pulse peak size of each signal.

5. The method according to claim 1, characterized in that, Frequency point mapping can convert frequency hopping sequences into data that is easy to transmit. The frequency mapping process is as follows: the frequency hopping frequency corresponding to each pulse in the JTIDS pulse signal is in the corresponding frequency hopping channel, and each channel has a channel number. Thus, the frequency hopping frequency sequence is mapped to a series of channel numbers.

6. The method according to claim 1, characterized in that, Step 5 includes: Time difference cross-positioning is based on the geometric positioning principle of hyperbolic intersection. By measuring the time difference between the arrival of the radiation source signal at each positioning platform, the time difference determines that the radiation source is located on a spatial hyperboloid with the current positions of the two positioning platforms as the focus. After deploying more than 4 positioning platforms, 3 spatial hyperboloids can be obtained accordingly, and their intersection point is the spatial position of the target radiation source.

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