Satellite navigation suppressing interference detection method based on GNSS occultation signal-to-noise ratio data

Abstract

The invention discloses a satellite navigation suppressing interference detection method based on GNSS occultation signal-to-noise ratio data. The satellite navigation suppressing interference detection method comprises the following steps: step 1, acquiring voltage signal-to-noise ratio data of navigation satellite signals received by a forward antenna and a backward antenna of an occultation receiver; step 2, carrying out filtering processing on the voltage signal-to-noise ratio data, and carrying out normalization processing on a filtered voltage signal-to-noise ratio value; 3, setting the length of a time window, and screening all satellite numbers of which the signal duration is greater than a set threshold value in the time window; step 4, combining the screened satellite numbers in pairs, and calculating cosine similarity coefficients of voltage signal-to-noise ratio sequences of two satellite signals corresponding to all combinations in a time window; step 5, calculating an average value of the cosine similarity coefficients in the detection time window, setting a detection threshold value, performing judgment according to the detection threshold value, and determining whether the satellite numbers are in the same range or not; and detection of satellite navigation suppression interference is realized. The method disclosed by the invention can continuously detect the satellite navigation suppressing interference in the coverage area range of the GNSS occultation receiver, is wide in detection coverage area, can realize satellite navigation suppressing interference detection in a large area range, especially beyond a territorial range, and has important significance for acquiring the global satellite navigation suppressing interference situation.

Description

Technical Field

[0001] The invention belongs to the field of satellite navigation, and in particular relates to a satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data in the field. Background Art

[0002] The global satellite navigation system is widely popular in navigation and timing applications due to its wide coverage, high timing accuracy and low application cost. Due to the vulnerability of satellite navigation signals such as low landing power and open signal structure, the stable operation of the satellite navigation system is affected by various interferences in a complex electromagnetic environment. The main threats come from suppression interference and deception interference. Among them, suppression interference is extremely destructive. The jammer overloads or saturates the receiver by transmitting strong interference signals, reducing or completely losing the receiver's ability to work.

[0003] To defend against satellite navigation suppression jamming attacks, we must first detect the suppression jamming. Domestic and foreign research institutions and scholars have developed many satellite navigation suppression jamming detection technologies, such as time-frequency domain energy detection, cyclostationary analysis, matched filter detection, and covariance matrix-based detection. These methods mainly use signal processing technology to construct interference detection quantities and detect suppression jamming by observing abnormal changes in the detection quantities. These methods construct interference detection quantities based on signal characteristic parameters and require the use of dedicated signal processing methods, which cannot be directly applied to general navigation terminals.

[0004] In recent years, low-orbit GNSS occultation technology has developed rapidly. The low-orbit satellite-borne GNSS occultation receiver antenna can receive satellite navigation signals from high orbits and interference signals from the ground, and can output parameters such as signal-to-noise ratio, providing conditions for wide-area satellite navigation to suppress interference detection. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a low-cost, simple and efficient satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data, which can use the voltage signal-to-noise ratio data of GNSS occultation measurement to realize the detection of ground suppression interference, thereby providing technical support for wide-area satellite navigation interference detection.

[0006] The present invention adopts the following technical solution:

[0007] A satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data, the improvement of which is that it comprises the following steps:

[0008] Step 1, obtaining voltage signal-to-noise ratio data of navigation satellite signals received by the forward and backward antennas of the occultation receiver;

[0009] Step 2, filtering the voltage signal-to-noise ratio data, and normalizing the filtered voltage signal-to-noise ratio value;

[0010] Step 3, set the time window length, and filter all satellite numbers whose signal duration in the time window is greater than the set threshold;

[0011] Step 4: Combine the selected satellite numbers in pairs and calculate the cosine similarity coefficient of the voltage signal-to-noise ratio sequences of the two satellite signals corresponding to all combinations in the time window:

[0012] The sampling rate of the voltage signal-to-noise ratio is 1 Hz. There are T voltage signal-to-noise ratio sample values ​​in the detection time window. The cosine similarity coefficient of the voltage signal-to-noise ratio sequence of any two satellite signals received in the detection time window is calculated:

[0013]

[0014] In the above formula, ρ i,j (k) is the cosine similarity coefficient of the voltage signal-to-noise ratio of the i-th satellite and the voltage signal-to-noise ratio of the j-th satellite in the k-th detection time window, SNR′ V,i (n) is the normalized voltage signal-to-noise ratio of the ith satellite at time n, SNR′ V,j (n) is the normalized voltage signal-to-noise ratio of the jth satellite at time n, |SNR′ V,i | is the modulus of the normalized voltage signal-to-noise ratio sequence of the ith satellite in the kth detection time window, |SNR′ V,j | is the modulus of the normalized voltage signal-to-noise ratio sequence of the jth satellite in the kth detection time window, and N is the number of satellite numbers that meet the duration requirements obtained by screening in step 3;

[0015] Step 5, calculate the average value of the cosine similarity coefficient within the detection time window, set the detection threshold, make a decision based on the detection threshold, and realize the detection of satellite navigation suppression interference.

[0016] Furthermore, the step 1 is specifically as follows:

[0017] The calculation formula for the equivalent 1s voltage signal-to-noise ratio of the i-th satellite received on the forward or backward antenna of the occultation receiver is:

[0018]

[0019] In the above formula, SNR V,i (n) is the equivalent 1s voltage signal-to-noise ratio of the ith satellite at time n, A s,i (n) is the signal amplitude of the i-th satellite received at time n, A n (n) is the average amplitude of the noise signal within 1s from the sampling time.

[0020] Furthermore, the step 2 is specifically as follows:

[0021] Design a bandpass filter to filter the voltage signal-to-noise ratio data, set the lower cutoff frequency of the passband to 0.02Hz, and the upper cutoff frequency to 0.075Hz;

[0022] Use the designed bandpass filter to filter the voltage signal-to-noise ratio data:

[0023]

[0024] In the above formula, is the voltage signal-to-noise ratio of the ith satellite after filtering at time n, h(n) is the unit impulse response of the bandpass filter at time n, is the convolution operator;

[0025] Use the original value of the voltage signal-to-noise ratio to normalize the filtered voltage signal-to-noise ratio:

[0026]

[0027] In the above formula, SNR′ V,i (n) is the normalized voltage signal-to-noise ratio of the i-th satellite at time n.

[0028] Furthermore, the step 3 is specifically as follows:

[0029] Set the detection time window to T seconds and the signal duration judgment threshold to The satellite number set obtained by screening is:

[0030]

[0031] In the above formula, T i is the duration of the i-th satellite in the detection time window, and the number of satellite numbers that meet the duration requirements is N.

[0032] Furthermore, the step 5 is specifically as follows:

[0033] Take the arithmetic mean of the multiple cosine similarity coefficients calculated in the same time window in step 4 to obtain the interference detection amount M(k) of the kth detection time window:

[0034]

[0035] In the above formula, L is the cosine similarity coefficient ρ calculated in the kth detection time window i,j (k) quantity;

[0036] The detection threshold is set to Th. When M(k)>Th, it is determined that the receiver is subject to suppression interference.

[0037] The beneficial effects of the present invention are:

[0038] The method disclosed in the present invention realizes the detection of satellite navigation suppression interference based on the universal signal parameters that can be output by the GNSS occultation receiver. Since the GNSS occultation is constantly moving, the method of the present invention can continuously detect the satellite navigation suppression interference within the area covered by the GNSS occultation receiver. The detection coverage is wide, and the satellite navigation suppression interference detection can be realized in a large area, especially outside the national territory, which is of great significance for obtaining the global satellite navigation suppression interference situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic flow diagram of the method of the present invention;

[0040] Figure 2 This is a graph of the voltage signal-to-noise ratio of different satellites changing with time during the period from 11:10 to 12:00 on January 29, 2021 during the COSMIC-2 occultation;

[0041] Figure 3 This is a graph of the filtered and normalized values ​​of the voltage signal-to-noise ratio of different satellites during the period from 11:10 to 12:00 on January 29, 2021, during the COSMIC-2 occultation;

[0042] Figure 4 This is a graph of the suppression interference detection results based on the voltage signal-to-noise ratio data of the COSMIC-2 occultation from 11:10 to 12:00 on January 29, 2021. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0044] Embodiment 1, this embodiment discloses a satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data, such as Figure 1 As shown, the following steps are included:

[0045] Step 1: Obtain the voltage signal-to-noise ratio data of the navigation satellite signal received by the forward and backward antennas of the occultation receiver:

[0046] The calculation formula for the equivalent 1s voltage signal-to-noise ratio of the i-th satellite received on the forward or backward antenna of the occultation receiver is:

[0047]

[0048] In the above formula, i is the satellite PRN number, n is the voltage signal-to-noise ratio sampling time, SNR V,i (n) is the equivalent 1s voltage signal-to-noise ratio of the ith satellite at time n, A s,i (n) is the signal amplitude of the i-th satellite received at time n, A n (n) is the average amplitude of the noise signal within 1 s from the sampling time. The data products released by each occultation constellation include voltage signal-to-noise ratio data, which can be directly obtained.

[0049] Step 2: Design a bandpass filter to filter the voltage signal-to-noise ratio data and normalize the filtered voltage signal-to-noise ratio value:

[0050] In order to eliminate the low-frequency variation effect of the voltage signal-to-noise ratio caused by the geometric distribution change between the low-orbit occultation satellite and the high-orbit navigation satellite, and the high-frequency oscillation effect of the voltage signal-to-noise ratio caused by the satellite signal passing through the troposphere and ionosphere, a bandpass filter is designed to filter the voltage signal-to-noise ratio data. The passband cutoff frequency of the filter is determined by the spectrum analysis of the voltage signal-to-noise ratio data. Usually, the lower limit cutoff frequency of the passband is set to 0.02Hz, and the upper limit cutoff frequency is set to 0.075Hz;

[0051] Use the designed bandpass filter to filter the voltage signal-to-noise ratio data:

[0052]

[0053] In the above formula, is the voltage signal-to-noise ratio of the ith satellite after filtering at time n, h(n) is the unit impulse response of the bandpass filter at time n, is the convolution operator;

[0054] In order to eliminate the influence of the received satellite signal strength on the satellite navigation interference detection, the voltage signal-to-noise ratio after filtering is normalized using the original value of the voltage signal-to-noise ratio:

[0055]

[0056] In the above formula, SNR′ V,i (n) is the normalized voltage signal-to-noise ratio of the i-th satellite at time n.

[0057] Step 3: Set the time window length and filter all satellite numbers whose signal duration in the time window is greater than the set threshold:

[0058] Set the detection time window to T seconds (s) and the signal duration judgment threshold to The satellite number set obtained by screening is:

[0059]

[0060] In the above formula, i is the satellite PRN number, T i is the duration of the i-th satellite in the detection time window, and the number of satellite numbers that meet the duration requirements is N, which is defined as:

[0061] N=card(S)

[0062] Step 4: Combine the selected satellite numbers in pairs and calculate the cosine similarity coefficient of the voltage signal-to-noise ratio sequences of the two satellite signals corresponding to all combinations in the time window:

[0063] The sampling rate of the voltage signal-to-noise ratio is 1 Hz. There are T voltage signal-to-noise ratio sample values ​​in the detection time window. The cosine similarity coefficient of the voltage signal-to-noise ratio sequence of any two satellite signals received in the detection time window is calculated:

[0064]

[0065] In the above formula, ρ i,j (k) is the cosine similarity coefficient of the voltage signal-to-noise ratio of the i-th satellite and the voltage signal-to-noise ratio of the j-th satellite in the k-th detection time window, SNR′ V,i (n) is the normalized voltage signal-to-noise ratio of the ith satellite at time n, SNR′ V,j (n) is the normalized voltage signal-to-noise ratio of the jth satellite at time n, |SNR′ V,i | is the modulus of the normalized voltage signal-to-noise ratio sequence of the ith satellite in the kth detection time window, |SNR′ V,j | is the modulus of the normalized voltage signal-to-noise ratio sequence of the jth satellite in the kth detection time window, and N is the number of satellite numbers that meet the duration requirements obtained by screening in step 3;

[0066] Step 5, calculate the average value of the cosine similarity coefficient within the detection time window, set the detection threshold, make a decision based on the detection threshold, and realize the detection of satellite navigation suppression interference:

[0067] Since the number of visible satellites in different detection time windows is different, in order to eliminate the influence of the number of visible satellites on interference detection, the arithmetic mean of the multiple cosine similarity coefficients calculated in the same time window in step 4 is taken to obtain the interference detection amount M(k) of the kth detection time window:

[0068]

[0069] In the above formula, L is the cosine similarity coefficient ρ calculated in the kth detection time window i,j The number of (k) is calculated as:

[0070]

[0071] A threshold decision is made based on the value of the interference detection quantity M(k), and the detection threshold is set as Th based on experience. When M(k)>Th, it is determined that the receiver is subject to suppressed interference.

[0072] The method of the present invention is further described in detail below through specific examples:

[0073] Step 1: Obtain the voltage signal-to-noise ratio data of the satellite signal received by the forward and backward antennas of the occultation receiver. In this embodiment, the level 1b podTc2 data in the public COSMIC-2 occultation data set is selected, and the data from 11:10 to 12:00 on January 29, 2021 is selected. Figure 2 This is a graph showing the voltage signal-to-noise ratio of different satellites changing with time during this period.

[0074] Step 2: Design a bandpass filter to filter the voltage signal-to-noise ratio data and normalize the filtered voltage signal-to-noise ratio value. In this embodiment, a 6th-order Butterworth bandpass filter is designed, and the lower limit cutoff frequency of the passband is set to 0.02 Hz and the upper limit cutoff frequency is set to 0.075 Hz. The values ​​of the voltage signal-to-noise ratios of different satellites after filtering and normalization are as follows: Figure 3 shown.

[0075] Step 3: Set the time window length to 900s, the signal duration judgment threshold to 675s, and filter all satellite numbers whose signal duration in the time window is greater than the set threshold;

[0076] Step 4: Combine the selected satellite numbers in pairs and calculate the cosine similarity coefficients of the voltage signal-to-noise ratio sequences of the two satellite signals corresponding to all combinations within the time window;

[0077] Step 5, calculate the average value of the cosine similarity coefficient within the detection time window, set the detection threshold to 0.5, make a decision based on the detection threshold, and realize the detection of satellite navigation suppression interference. The satellite navigation interference detection result of this embodiment is as follows: Figure 4 shown.

Claims

1. A satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data, characterized in that: The steps include: Step 1, obtaining voltage signal-to-noise ratio data of navigation satellite signals received by the forward and backward antennas of the occultation receiver; Step 2, filtering the voltage signal-to-noise ratio data, and normalizing the filtered voltage signal-to-noise ratio value; Step 3, set the time window length, and filter all satellite numbers whose signal duration in the time window is greater than the set threshold; Step 4: Combine the selected satellite numbers in pairs and calculate the cosine similarity coefficient of the voltage signal-to-noise ratio sequences of the two satellite signals corresponding to all combinations in the time window: The sampling rate of the voltage signal-to-noise ratio is 1 Hz. There are T voltage signal-to-noise ratio sample values ​​in the detection time window. The cosine similarity coefficient of the voltage signal-to-noise ratio sequence of any two satellite signals received in the detection time window is calculated: In the above formula, ρ i,j (k) is the cosine similarity coefficient of the voltage signal-to-noise ratio of the i-th satellite and the voltage signal-to-noise ratio of the j-th satellite in the k-th detection time window, SNR′ V,i (n) is the normalized voltage signal-to-noise ratio of the ith satellite at time n, SNR′ V,j (n) is the normalized voltage signal-to-noise ratio of the jth satellite at time n, |SNR′ V,i | is the modulus of the normalized voltage signal-to-noise ratio sequence of the ith satellite in the kth detection time window, |SNR′ V,j | is the modulus of the normalized voltage signal-to-noise ratio sequence of the jth satellite in the kth detection time window, and N is the number of satellite numbers that meet the duration requirements obtained by screening in step 3; Step 5, calculate the average value of the cosine similarity coefficient within the detection time window, set the detection threshold, make a decision based on the detection threshold, and realize the detection of satellite navigation suppression interference.

2. The satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data according to claim 1 is characterized in that: The step 1 is specifically as follows: The calculation formula for the equivalent 1s voltage signal-to-noise ratio of the i-th satellite received on the forward or backward antenna of the occultation receiver is: In the above formula, SNR V,i (n) is the equivalent 1s voltage signal-to-noise ratio of the ith satellite at time n, A s,i (n) is the signal amplitude of the i-th satellite received at time n, A n (n) is the average amplitude of the noise signal within 1s from the sampling time.

3. The satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data according to claim 2 is characterized in that: The step 2 is specifically as follows: Design a bandpass filter to filter the voltage signal-to-noise ratio data, set the lower cutoff frequency of the passband to 0.02Hz, and the upper cutoff frequency to 0.075Hz; Use the designed bandpass filter to filter the voltage signal-to-noise ratio data: In the above formula, is the voltage signal-to-noise ratio of the ith satellite after filtering at time n, h(n) is the unit impulse response of the bandpass filter at time n, is the convolution operator; Use the original value of the voltage signal-to-noise ratio to normalize the filtered voltage signal-to-noise ratio: In the above formula, SNR′ V,i (n) is the normalized voltage signal-to-noise ratio of the i-th satellite at time n.

4. The satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data according to claim 1, characterized in that: The step 3 is specifically as follows: Set the detection time window to T seconds and the signal duration judgment threshold to The satellite number set obtained by screening is: In the above formula, T i is the duration of the i-th satellite in the detection time window, and the number of satellite numbers that meet the duration requirements is N.

5. The satellite navigation suppression interference detection method based on GNSS occultation signal-to-noise ratio data according to claim 1, characterized in that: The step 5 is specifically as follows: Take the arithmetic mean of the multiple cosine similarity coefficients calculated in the same time window in step 4 to obtain the interference detection amount M(k) of the kth detection time window: In the above formula, L is the cosine similarity coefficient ρ calculated in the kth detection time window i,j (k) quantity; The detection threshold is set to Th. When M(k)>Th, it is determined that the receiver is subject to suppression interference.

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