Anti-satellite signal loss tracking system and method for two-dimensional ballistic correction fuses

Abstract

This invention discloses a method and system for tracking satellite signals that resists loss of lock in a two-dimensional ballistic correction fuze. It can be used to track high-dynamic, weak satellite signals received by a single antenna on a two-dimensional ballistic correction fuze when the antenna is briefly blocked by a projectile. The system includes several functional modules: a vector tracking Kalman filter, a phase-locked loop / frequency-locked loop filter, a carrier / code NCO, a correlator, a carrier / code phase discriminator, and a loss-of-lock detector. The high-dynamic, weak satellite signals received by a single antenna on a two-dimensional ballistic correction fuze are characterized by discontinuity, large amplitude variations, and susceptibility to loss of lock. This invention can track satellite signals received by a single antenna rotating on a two-dimensional ballistic correction fuze, improving the tracking loop's resistance to loss of lock. Compared to traditional tracking methods, this invention has stronger resistance to loss of lock and, combined with a vector tracking method, achieves higher tracking accuracy.

Description

Technical Field

[0001] This invention relates to the field of satellite signal tracking technology, and more specifically to an anti-satellite signal loss tracking system and method for two-dimensional ballistic correction fuses. Background Technology

[0002] When a single antenna mounted on the upper side of a two-dimensional ballistic correction fuze receives satellite signals, it is affected by the short-term obstruction of the projectile. The received high-dynamic weak satellite signals are discontinuous, have large amplitude variations, and are prone to loss of lock. Traditional scalar tracking loops are prone to loss of lock during satellite signal tracking.

[0003] The existing solution involves mounting an omnidirectional antenna at the front of the fuze. When the projectile rotates the fuze, the omnidirectional antenna, due to its omnidirectional characteristics, is not affected by projectile obstruction or rotational Doppler interference, allowing a traditional scalar tracking loop to achieve stable satellite signal tracking. However, using a single antenna mounted on the side of the cylindrical part of the fuze to receive satellite signals offers advantages such as small antenna size, low cost, and simple structure. It also enables roll attitude measurement based on satellite signals, making it necessary to study navigation and velocity measurement functions under this mounting method. However, when using a single side antenna to receive satellite signals, it is subject to projectile obstruction and modulation of the rotational Doppler frequency. This makes it easy for traditional scalar tracking loops to lose lock during satellite signal tracking, and currently, there is no solution to this problem. Summary of the Invention

[0004] In view of this, the present invention provides a satellite signal lock-off tracking system and method for a two-dimensional ballistic correction fuze, which can solve the problem of traditional scalar tracking loops easily losing lock-off during satellite signal tracking in high-dynamic environments where the antenna of a two-dimensional ballistic correction fuze is blocked for a short time. Using this invention, stable and accurate satellite signal tracking can be achieved.

[0005] To achieve the above objectives, the technical solution of the anti-satellite signal loss-tracking system for two-dimensional ballistic correction fuses of the present invention is as follows: the system includes a vector tracking Kalman filter, a phase-locked loop / frequency-locked loop filter, a carrier / code NCO, a correlator, a carrier / code phase discriminator, and a loss-tracking detector.

[0006] The carrier / code NCO generates local carrier and code signals based on the tracking results of the satellite signal by the selected filter, and sends them to the correlator.

[0007] The correlator receives satellite signal input, performs correlation operations on the satellite signal with the local carrier and code signal, and obtains I and Q values ​​from the correlation operation results. These I and Q values ​​are then input to the carrier / code phase discriminator.

[0008] The carrier / code phase discriminator calculates the carrier frequency discrimination error ω using I and Q values. e carrier phase detection error φe .

[0009] The loss-of-lock discriminator determines whether the loop is lost-locked and selects the appropriate filter type. If the loop is lost-locked, a vector tracking Kalman filter is selected; otherwise, a phase-locked loop / frequency-locked loop filter is selected.

[0010] The vector tracking Kalman filter combines real-time updated navigation information with auxiliary state variables to perform vector tracking of satellite signals.

[0011] Phase-locked loop (PLL) / frequency-locked loop (FLL) filters are scalar tracking loops used for scalar tracking of satellite signals.

[0012] Furthermore, the correlator receives the satellite signal input and performs correlation operations on the satellite signal with the local carrier and code signals. The correlation operation results in I and Q values, where the I and Q values ​​include the instantaneous correlation branch I and Q values. P and Q P , advance related branch I, Q value I E and Q E Lagging related branch I, Q value I L and Q L .

[0013] Furthermore, the workflow of the unlock detection device is as follows:

[0014] First, the carrier-to-noise ratio (CNR) is calculated using I and Q values, and a CNR of less than 38 dB·Hz is taken as a prerequisite for loss of lock-in.

[0015] Secondly, the frequency discrimination error ω within 1 second of the tracking loop's operating period. e Phase detection error φ e Perform mean squared error statistics.

[0016] Finally, using the average frequency of the channel with a carrier-to-noise ratio greater than 40 dB·Hz as the reference frequency, the error between the local signal Doppler frequency and the reference frequency is detected, which is the Doppler frequency offset.

[0017] The unlocking condition for frequency discrimination error is that the mean square error is greater than 300 Hz within 1 second; the unlocking condition for phase discrimination error is that the mean square error is greater than 60° within 1 second; and the unlocking condition for Doppler frequency shift is greater than 300 Hz.

[0018] If the three conditions for loss of lock are met—frequency detection error, phase detection error, and Doppler frequency offset—two or more of the conditions are satisfied, then the loop is considered to be out of lock; otherwise, it is considered not out of lock.

[0019] Another embodiment of the present invention provides a method for tracking satellite signal loss of lock for a two-dimensional ballistic correction fuze, comprising the following steps:

[0020] Step 1: Receive satellite signal input, perform correlation calculations between the satellite signal and the local carrier and code signal, and obtain the I and Q values ​​from the correlation calculation results;

[0021] Step 2: Use I and Q values ​​to perform carrier / code phase discrimination to obtain the carrier frequency discrimination error ω. e carrier phase detection error φ e ;

[0022] Step 3: Determine if the loop is out of lock and select the type of filter to be used. If it is out of lock, select the vector tracking Kalman filter and proceed to Step 4. If it is not out of lock, select the phase-locked loop / frequency-locked loop filter and proceed to Step 5.

[0023] Step 4: The vector tracking Kalman filter, combined with the real-time updated navigation information auxiliary state variables, performs vector tracking on the satellite signal. Based on the vector tracking results, the local carrier and code signals are adjusted, and the process returns to Step 1.

[0024] Step 5: The phase-locked loop / frequency-locked loop filter is a scalar tracking loop used to perform scalar tracking on the satellite signal. Based on the scalar tracking result, the local carrier and code signal are adjusted, and the process returns to step 1.

[0025] Furthermore, correlation operations are performed between the satellite signal and the local carrier and code signal. The results of the correlation operations yield I and Q values, where the I and Q values ​​include the instantaneous correlation branch I and Q values. P and Q P , advance related branch I, Q value I E and Q E Lagging related branch I, Q value I L and Q L .

[0026] Furthermore, step 3 specifically includes the following steps:

[0027] First, the carrier-to-noise ratio is calculated using I and Q values, and a carrier-to-noise ratio of less than 38dB·Hz is taken as a prerequisite for loss of lock.

[0028] Secondly, the frequency discrimination error ω within 1 second of the tracking loop's operating period. e Phase detection error φ e Perform mean squared error statistics;

[0029] Finally, using the average frequency of the channel with a carrier-to-noise ratio greater than 40dB·Hz as the reference frequency, the error between the local signal Doppler frequency and the reference frequency is detected, which is the Doppler frequency offset.

[0030] The unlocking condition for frequency discrimination error is that the mean square error is greater than 300 Hz within 1 second; the unlocking condition for phase discrimination error is that the mean square error is greater than 60° within 1 second; and the unlocking condition for Doppler frequency shift is greater than 300 Hz.

[0031] If the three conditions for loss of lock are met—frequency detection error, phase detection error, and Doppler frequency offset—two or more of the conditions are satisfied, then the loop is considered to be out of lock; otherwise, it is considered not out of lock.

[0032] Beneficial effects:

[0033] 1. This invention designs an anti-satellite signal loss-tracking method for two-dimensional ballistic correction fuses, which can be used to track highly dynamic and weak satellite signals. This invention can improve the stability and accuracy of satellite signal tracking under highly dynamic and weak signal conditions with relatively low computational load, providing stable carrier / code frequency and phase information for satellite signal navigation and positioning.

[0034] 2. In this invention, scalar tracking offers advantages such as low computational complexity and fast tracking response when the signal strength is high and the tracking loop is healthy and not lost lock. When the signal strength is weak and the tracking loop is lost lock, a vector tracking filter comes into play to assist the scalar loop in tracking satellite signals. This method introduces the correlation characteristics between projectile motion information and satellite signals into the vector tracking loop and uses a vector-assisted scalar filter to jointly assist tracking of all satellite tracking channels. When the code or carrier scalar tracking loop fails, assistance is provided to improve the loop's dynamics and enhance the tracking accuracy and reliability of discontinuous, rapidly changing satellite signals. Scalar tracking loops have advantages such as low computational complexity, simple implementation, and fast response speed, but they suffer from drawbacks such as easy loss of lock and low accuracy when tracking rotating, discontinuous satellite signals. This invention solves the problems of easy satellite loss and easy loss of lock when tracking satellite signals received by a single rotating antenna by combining scalar and vector tracking methods. At the same time, the vector tracking filter only operates when the scalar tracking loop is about to lose lock, reducing computational complexity. Attached Figure Description

[0035] Figure 1 This is a block diagram of the anti-satellite signal loss tracking system for a two-dimensional ballistic correction fuze provided by the present invention;

[0036] Figure 2 This is a schematic diagram of a lock loss detector. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Example 1:

[0039] This invention designs an anti-satellite signal loss-tracking system for a two-dimensional ballistic correction fuze, which includes the following components: a vector tracking Kalman filter 1, a phase-locked loop / frequency-locked loop filter 2, a carrier / code NCO 3, a correlator 4, a carrier / code phase discriminator 5, and a loss-tracking detector 6.

[0040] The carrier / code NCO3 generates local carrier and code signals based on the tracking results of the satellite signal by the selected filter, and sends them to the correlator 4;

[0041] Correlator 4 receives satellite signal input, performs correlation operation on the satellite signal with the local carrier and code signal, and obtains I and Q values ​​from the correlation operation results. The above I and Q values ​​are input to carrier / code phase discriminator 5.

[0042] The carrier / code phase discriminator 5 calculates the carrier frequency discrimination error ω using the I and Q values. e carrier phase detection error φ e ;

[0043] The loss-of-lock discriminator 6 determines whether the loop is lost-locked and selects the actual filter type to be used. If the loop is lost-locked, the vector tracking Kalman filter 1 is selected; if the loop is not lost-locked, the phase-locked loop / frequency-locked loop filter 2 is selected.

[0044] Vector tracking Kalman filter 1 combines real-time updated navigation information with auxiliary state variables to perform vector tracking of satellite signals;

[0045] Phase-locked loop / frequency-locked loop filter 2 is a scalar tracking loop used for scalar tracking of satellite signals.

[0046] The satellite signal is input into the tracking loop and correlated with the local carrier / code signal generated by the local carrier / code NCO3 in correlator 4. The correlation result yields I and Q values, including the I and Q values ​​of the instantaneous correlation branch. P and Q P , advance related branch I, Q value I E and Q E Lagging related branch I, Q value I L and Q L The I and Q values ​​are input into the carrier / code phase discriminator 5, which uses the I and Q values ​​to calculate the carrier frequency discrimination error ω. e carrier phase detection error φ e The loss-of-lock discriminator 6 determines the loss of lock based on the frequency discrimination error ω. e carrier phase detection error φ e The system determines whether the loop has lost lock and selects the appropriate filter type for use. The block diagram of the lockout detector 6 is shown below. Figure 2 As shown.

[0047] The working process of the loss-of-lock discriminator 6 is as follows: First, it calculates the carrier-to-noise ratio (CNR) using the I and Q values. Since the CNR more accurately characterizes the signal strength relative to noise than the signal amplitude, it is almost impossible to distinguish the satellite signal from the noise when the CNR is less than 38 dB·Hz. Therefore, a CNR less than 38 dB·Hz is used as a prerequisite for loss of lock. Second, it measures the frequency discrimination error ω within 1 second of the tracking loop's operating period. e Phase detection error φ e Statistical mean square error is performed. Finally, using the average frequency of channels with a carrier-to-noise ratio greater than 40 dB·Hz as the reference frequency, the error between the local signal Doppler frequency and the reference frequency is detected, which is the Doppler frequency offset. When two or more of the three unlocking conditions—frequency discrimination error, phase discrimination error, and Doppler frequency offset—are met, if the frequency discrimination error has a mean square error greater than 300 Hz within 1 second, the phase discrimination error has a mean square error greater than 60° within 1 second, and the Doppler frequency offset is greater than 300 Hz, the loop is considered to be unlocked. This unlocking condition setting improves loop stability and prevents the adjustment state of the tracking loop during a brief obstruction process from being mistakenly judged as unlocking.

[0048] Example 2

[0049] Based on the above principles, another embodiment of the present invention provides a method for tracking satellite signal loss of lock using a two-dimensional ballistic correction fuze, the specific steps of which are as follows:

[0050] Step 1: Receive satellite signal input, perform correlation operations between the satellite signal and the local carrier and code signals, and obtain the I and Q values ​​from the correlation operation results; where the I and Q values ​​include the instantaneous correlation branch I and Q values. P and Q P , advance related branch I, Q value I E and Q E Lagging related branch I, Q value I L and Q L .

[0051] Step 2: Use I and Q values ​​to perform carrier / code phase discrimination to obtain the carrier frequency discrimination error ω. e carrier phase detection error φ e ;

[0052] Step 3: Determine whether the loop is out of lock and select the actual filter type to be used. If it is out of lock, select the vector tracking Kalman filter (1) and proceed to step 4. If it is not out of lock, select the phase-locked loop / frequency-locked loop filter (2) and proceed to step 5.

[0053] The process of determining if a lock has been lost is as follows:

[0054] First, the carrier-to-noise ratio is calculated using I and Q values, and a carrier-to-noise ratio of less than 38dB·Hz is taken as a prerequisite for loss of lock.

[0055] Secondly, the frequency discrimination error ω within 1 second of the tracking loop's operating period. e Phase detection error φ e Perform mean squared error statistics;

[0056] Finally, using the average frequency of the channel with a carrier-to-noise ratio greater than 40dB·Hz as the reference frequency, the error between the local signal Doppler frequency and the reference frequency is detected, which is the Doppler frequency offset.

[0057] The unlocking condition for frequency discrimination error is that the mean square error is greater than 300 Hz within 1 second; the unlocking condition for phase discrimination error is that the mean square error is greater than 60° within 1 second; and the unlocking condition for Doppler frequency shift is greater than 300 Hz.

[0058] If the three conditions for loss of lock are met—frequency detection error, phase detection error, and Doppler frequency offset—two or more of the conditions are satisfied, then the loop is considered to be out of lock; otherwise, it is considered not out of lock.

[0059] Step 4: Vector tracking Kalman filter (1) Combine the real-time updated navigation information with auxiliary state variables to perform vector tracking of satellite signals, adjust the local carrier and code signals according to the vector tracking results, and return to step 1;

[0060] Step 5: The phase-locked loop / frequency-locked loop filter (2) is a scalar tracking loop used to perform scalar tracking on the satellite signal. Based on the scalar tracking result, the local carrier and code signal are adjusted, and the process returns to step 1.

[0061] This invention offers advantages such as low computational complexity and fast tracking response in scalar tracking when signal strength is high and the tracking loop is healthy and not lost. When signal strength is weak and the tracking loop is lost, a vector tracking filter comes into play, assisting the scalar loop in satellite signal tracking. This method introduces the correlation characteristics between projectile motion information and satellite signals into the vector tracking loop and uses a vector-assisted scalar filter to jointly assist tracking of all satellite tracking channels. When the code or carrier scalar tracking loop fails, assistance is provided to improve the loop's dynamics and enhance the tracking accuracy and reliability of discontinuous, rapidly changing satellite signals.

[0062] Scalar tracking loops offer advantages such as low computational complexity, simple implementation, and fast response speed. However, they suffer from drawbacks like easy loss of lock and low accuracy when tracking rotating, discontinuous satellite signals. This invention addresses the issues of easy satellite loss and lock-up when tracking satellite signals received by a single rotating antenna by combining scalar and vector tracking methods. Furthermore, the vector tracking filter only operates at the moment the scalar tracking loop is about to lose lock, thus reducing computational complexity.

[0063] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A satellite signal loss-tracking system for two-dimensional ballistic correction fuses, characterized in that, It includes the following functional modules: vector tracking Kalman filter (1), phase-locked loop / frequency-locked loop filter (2), carrier / code NCO (3), correlator (4), carrier / code phase discriminator (5), and lockout discriminator (6); The carrier / code NCO (3) generates local carrier and code signals based on the tracking results of the satellite signals by the selected filter, and sends them to the correlator (4). The correlator (4) receives satellite signal input, and the correlator (4) performs correlation operation on the satellite signal and the local carrier and code signal. The correlation operation result is I and Q values, and the above I and Q values ​​are input to the carrier / code phase discriminator (5). The carrier / code phase discriminator (5) calculates the carrier frequency discrimination error using the I and Q values. carrier phase detection error ; The lockout discriminator (6) determines whether the loop is locked and selects the type of filter to be used. If the loop is locked, the vector tracking Kalman filter (1) is selected; if the loop is not locked, the phase-locked loop / frequency-locked loop filter (2) is selected. The working process of the lockout discriminator (6) is as follows: First, the carrier-to-noise ratio is calculated using I and Q values, and a carrier-to-noise ratio of less than 38dB·Hz is taken as a prerequisite for loss of lock. Secondly, the frequency discrimination error within 1 second of the tracking loop's operating period. and phase detection error Perform mean squared error statistics; Finally, using the average frequency of the channel with a carrier-to-noise ratio greater than 40dB·Hz as the reference frequency, the error between the local signal Doppler frequency and the reference frequency is detected, which is the Doppler frequency offset. The unlocking condition for the frequency discrimination error is that the mean square error is greater than 300 Hz within 1 second; the unlocking condition for the phase discrimination error is that the mean square error is greater than 60° within 1 second; and the unlocking condition for the Doppler frequency shift is greater than 300 Hz. If the above-mentioned unlocking preconditions are met, and two or more of the three unlocking conditions—frequency detection error, phase detection error, and Doppler frequency offset—are met, then the loop is considered to be unlocked; otherwise, it is considered not to be unlocked. The vector tracking Kalman filter (1) combines real-time updated navigation information with auxiliary state variables to perform vector tracking of satellite signals; The phase-locked loop / frequency-locked loop filter (2) is a scalar tracking loop used for scalar tracking of satellite signals.

2. The anti-satellite signal loss tracking system for a two-dimensional ballistic correction fuze as described in claim 1, characterized in that, The correlator (4) receives the satellite signal input and performs a correlation operation between the satellite signal and the local carrier and code signal. The correlation operation results in I and Q values, where the I and Q values ​​include the instantaneous correlation branch I and Q values. P and Q P , advance related branch I, Q value I E and Q E Lagging related branch I, Q value I L and Q L .

3. A method for tracking satellite signal loss of lock in a two-dimensional ballistic correction fuze, characterized in that, Includes the following steps: Step 1: Receive satellite signal input, perform correlation calculation on the satellite signal and the local carrier and code signal, and obtain the I and Q values ​​from the correlation calculation results; Step 2: Use the I and Q values ​​to perform carrier / code phase discrimination to obtain the carrier frequency discrimination error. carrier phase detection error ; Step 3: Determine whether the loop is unlocked and select the actual filter type. If it is unlocked, select the vector tracking Kalman filter (1) and proceed to step 4. If it is not unlocked, select the phase-locked loop / frequency-locked loop filter (2) and proceed to step 5. Step 3 specifically includes the following steps: First, the carrier-to-noise ratio is calculated using I and Q values, and a carrier-to-noise ratio of less than 38dB·Hz is taken as a prerequisite for loss of lock. Secondly, the frequency discrimination error within 1 second of the tracking loop's operating period. and phase detection error Perform mean squared error statistics; Finally, using the average frequency of the channel with a carrier-to-noise ratio greater than 40dB·Hz as the reference frequency, the error between the local signal Doppler frequency and the reference frequency is detected, which is the Doppler frequency offset. The unlocking condition for the frequency discrimination error is that the mean square error is greater than 300 Hz within 1 second; the unlocking condition for the phase discrimination error is that the mean square error is greater than 60° within 1 second; and the unlocking condition for the Doppler frequency shift is greater than 300 Hz. If the above-mentioned unlocking preconditions are met, and two or more of the three unlocking conditions—frequency detection error, phase detection error, and Doppler frequency offset—are met, then the loop is considered to be unlocked; otherwise, it is considered not to be unlocked. Step 4: Vector tracking Kalman filter (1) Combine the real-time updated navigation information with the auxiliary state variables to perform vector tracking of the satellite signal, adjust the local carrier and code signal according to the vector tracking results, and return to step 1; Step 5: The phase-locked loop / frequency-locked loop filter (2) is a scalar tracking loop used to perform scalar tracking on satellite signals. Based on the scalar tracking results, the local carrier and code signals are adjusted, and the process returns to step 1.

4. The anti-satellite signal loss tracking method for a two-dimensional ballistic correction fuze as described in claim 3, characterized in that, The satellite signal is correlated with the local carrier and code signal, and the correlation result yields I and Q values, where the I and Q values ​​include the instantaneous correlation branch I and Q values. P and Q P , advance related branch I, Q value I E and Q E Lagging related branch I, Q value I L and Q L .

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