Low earth orbit satellite signal capturing method and device

Abstract

The invention belongs to the technical field of signal capturing, and relates to a low-orbit satellite signal capturing method and device. The method comprises the following steps: acquiring a radio frequency signal sent by a low earth orbit satellite to obtain a zero intermediate frequency signal; obtaining orbit parameters, current time, current positioning, forecast entry and exit time, minimum Doppler frequency shift and maximum Doppler frequency shift of the low-orbit satellite; if it is judged that the current time is within the entry and exit time of the low-orbit satellite, a conjugate multiplication result is obtained according to the zero intermediate frequency signal; obtaining a discrete Fourier transform result according to the conjugate multiplication result, the minimum Doppler frequency shift in the exit-entry time and the maximum Doppler frequency shift in the exit-entry time; and judging according to a discrete Fourier transform result, if the capture is judged to be successful, calculating a Doppler frequency offset result obtained by capture, and outputting the Doppler frequency offset result, the pilot band of the zero intermediate frequency signal and the data segment of the zero intermediate frequency signal as capture results. According to the invention, the calculation amount of low-orbit satellite signal acquisition is small and the power consumption is low.

Description

Technical Field

[0001] The present application relates to the technical field of signal capture, and in particular to a method and device for capturing low-orbit satellite signals. Background Art

[0002] As the number of Internet users continues to increase worldwide, the demand for high-speed, low-latency and global coverage communication services is growing.

[0003] Low-orbit satellite communication systems have faster satellite movement and shorter signal propagation distances, and can provide these services to meet user needs. Moreover, the advancement of low-orbit satellite communication technology has enabled its application areas to continue to expand. In addition to traditional communication services, low-orbit satellites are also used in the Internet of Things, intelligent transportation, telemedicine, navigation enhancement, environmental monitoring and other fields. The growth in demand in these areas has driven market expansion.

[0004] However, low-orbit satellites also face challenges, such as faster speeds leading to a greater Doppler effect and shorter transit times of low-orbit satellites. These factors bring considerable challenges and difficulties to ground terminals in capturing low-orbit satellite signals.

[0005] Generally, in low-orbit satellite communication systems, in order for the ground-based low-orbit satellite signal receiving end to be able to quickly estimate the carrier frequency difference and bit deviation, a known preamble, i.e., a pilot sequence, is usually carried in each frame. The receiving end uses the known pilot sequence to capture the low-orbit satellite signal, i.e., signal arrival detection and a rough estimate of the phase and frequency of the received signal.

[0006] In the current ground receiver low-orbit satellite signal capture method, most ground low-orbit satellite signal receivers are always in a powered-on capture state to prevent missing the signals transmitted by the low-orbit satellite to the ground during the short satellite transit time.

[0007] However, these methods have high requirements on the power consumption of the receiver and the complexity of the acquisition algorithm. Summary of the invention

[0008] Based on this, it is necessary to provide a low-orbit satellite signal capture method and device to address the above-mentioned technical problems, so as to reduce the computational complexity, computational complexity and power consumption of low-orbit satellite signal capture.

[0009] A low-orbit satellite signal acquisition method, comprising:

[0010] Acquire the radio frequency signal sent by the low-orbit satellite, and obtain the zero intermediate frequency signal according to the radio frequency signal;

[0011] Obtain the orbital parameters, current time and current position of the low-orbit satellite, and predict the entry and exit time of the low-orbit satellite relative to the ground from the current time to multiple hours in the future, the minimum Doppler shift during the entry and exit time, and the maximum Doppler shift during the entry and exit time;

[0012] A judgment is made based on the current time and the entry and exit time of the low-orbit satellite. If it is judged that the current time is within the entry and exit time of the low-orbit satellite, a conjugate multiplication result is obtained based on the zero intermediate frequency signal; a discrete Fourier transform result is obtained based on the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time;

[0013] A judgment is made based on the discrete Fourier transform result. If the capture is successful, the Doppler frequency deviation result obtained by the capture is calculated, and the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal, and the data segment of the zero intermediate frequency signal are output as the capture result.

[0014] In one embodiment, a judgment is made based on the current time and the entry and exit time of the low-orbit satellite. If it is determined that the current time is within the entry and exit time of the low-orbit satellite, a conjugate multiplication result is obtained based on the zero intermediate frequency signal; a discrete Fourier transform result is obtained based on the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time, including:

[0015] According to the current time and the entry and exit time of the low-orbit satellite, it is judged whether the current time is within the entry and exit time of the low-orbit satellite;

[0016] If it is determined that the current time is within the entry and exit time of the low-orbit satellite, the zero intermediate frequency signal and the pilot pseudo-random sequence are conjugate multiplied in the time dimension to obtain a conjugate multiplication result;

[0017] According to the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time, a discrete Fourier transform calculation is performed in the frequency dimension to obtain a discrete Fourier transform result.

[0018] In one embodiment, a discrete Fourier transform calculation is performed in the frequency dimension according to the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time to obtain a discrete Fourier transform result, including:

[0019]

[0020] In the formula, s f (k) is the discrete Fourier transform result, M is the number of points in the pilot pseudo-random sequence, s t (n) is the result of conjugate multiplication, j is the imaginary number sign, k = floor (f dn / fstep ),floor(f dn / f step) +1,…,ceil(f up / f step ), where floor(.) is rounded down, ceil(.) is rounded up, and f step is the frequency search interval of discrete Fourier transform, f dn is the minimum Doppler frequency shift during the entry and exit time, f up is the maximum Doppler shift during the entry and exit time.

[0021] In one embodiment, the zero intermediate frequency signal and the pilot pseudo-random sequence are conjugate multiplied in the time dimension to obtain a conjugate multiplication result, including:

[0022]

[0023] In the formula, s t (n) is the conjugate multiplication result, M is the number of points of the pilot pseudo-random sequence, s(n) is the zero intermediate frequency signal, conj(.) is the conjugate conversion, and pn(n) is the pilot pseudo-random sequence.

[0024] In one embodiment, if it is determined that the current time is not within the entry and exit time of the low-orbit satellite, the calculation channel of the conjugate multiplication result and the discrete Fourier transform result is closed.

[0025] In one embodiment, a judgment is made based on a discrete Fourier transform result. If the capture is successful, the Doppler frequency deviation result obtained by the capture is calculated, and the conjugate multiplication result is output as the capture result, including:

[0026] According to the discrete Fourier transform results, the peak value, mean value and peak index of the signal are obtained, and it is judged whether the capture is successful;

[0027] If the capture is successful, the Doppler frequency deviation result obtained by the capture is calculated according to the peak index, and the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal and the data segment of the zero intermediate frequency signal are output as the capture result;

[0028] If it is judged that the capture fails, the forecast is repeated and the next round of capture is carried out.

[0029] In one embodiment, according to the discrete Fourier transform result, the peak value, mean value and peak index of the signal are obtained, and whether the capture is successful is determined, including:

[0030] According to the discrete Fourier transform results, the peak value, mean value and peak index of the signal are obtained;

[0031] Based on the peak value and the mean value, the peak-to-average ratio is calculated;

[0032] Compare the peak-to-average ratio with the capture success threshold to determine whether the capture is successful.

[0033] In one embodiment, obtaining a radio frequency signal sent by a low-orbit satellite and obtaining a zero intermediate frequency signal according to the radio frequency signal includes:

[0034] Obtain the radio frequency signal sent by the low-orbit satellite, perform radio frequency down-conversion, and obtain the intermediate frequency signal;

[0035] Perform analog-to-digital conversion sampling on the intermediate frequency signal to obtain an intermediate frequency sampling signal;

[0036] The intermediate frequency sampling signal is digitally down-converted to zero intermediate frequency to obtain a zero intermediate frequency signal.

[0037] A low-orbit satellite signal capture device adopts a low-orbit satellite signal capture method, including: a front-end unit and a capture processing unit;

[0038] The front-end unit is used to obtain the radio frequency signal sent by the low-orbit satellite and obtain the zero intermediate frequency signal according to the radio frequency signal;

[0039] The capture processing unit includes: a control module, a positioning module, a storage module, a conversion module and a correlator module, the control module is respectively connected to the positioning module, the storage module, the conversion module and the correlator module, and the control module is also connected to the front unit;

[0040] The control module is used to obtain the orbital parameters of the low-orbit satellite, and in combination with the current time and the current positioning, predict the low-orbit satellite entry and exit time relative to the ground from the current time to multiple hours in the future, the minimum Doppler frequency shift during the entry and exit time, and the maximum Doppler frequency shift during the entry and exit time; it is also used to judge whether the current time is within the low-orbit satellite entry and exit time according to the current time and the low-orbit satellite entry and exit time; it is also used to send the zero intermediate frequency signal to the correlator module; it is also used to judge whether the capture is successful according to the discrete Fourier transform result, and when it is judged that the capture is successful, calculate the Doppler frequency deviation result obtained by the capture, and output the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal, and the data segment of the zero intermediate frequency signal as the capture result;

[0041] The positioning module is used to obtain the current time and current location;

[0042] The storage module is used to store the entry and exit time, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time;

[0043] The transformation module is used to obtain a discrete Fourier transform result according to the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time;

[0044] The correlator module is used to determine when the current time is within the entry and exit time of the low-orbit satellite, and obtain the conjugate multiplication result based on the zero intermediate frequency signal.

[0045] In one embodiment, the front unit includes: an acquisition module, a sampling module and a frequency conversion module connected in sequence;

[0046] The acquisition module is used to acquire the radio frequency signal sent by the low-orbit satellite, and obtain the intermediate frequency signal after the radio frequency down-conversion;

[0047] The sampling module is used to perform analog-to-digital conversion sampling on the intermediate frequency signal to obtain an intermediate frequency sampling signal;

[0048] The frequency conversion module is used to digitally down-convert the intermediate frequency sampling signal to a zero intermediate frequency to obtain a zero intermediate frequency signal.

[0049] The above-mentioned low-orbit satellite signal capture method and device is a technology for predicting Doppler frequency shift based on the satellite orbit motion model. By analyzing the orbital parameters and motion laws of the low-orbit satellite, the entry and exit time and Doppler frequency shift of the low-orbit satellite relative to the ground low-orbit satellite signal capture terminal in the future are predicted. The ground low-orbit satellite signal capture terminal captures the low-orbit satellite transmission signal on this basis. Compared with the traditional method, it can:

[0050] 1) Predict the entry and exit times and Doppler shift of low-orbit satellite signals in advance;

[0051] 2) The ground-based low-orbit satellite signal acquisition terminal can control the switch of acquisition-related modules according to the predicted entry and exit time of the low-orbit satellite to save power consumption;

[0052] 3) The ground-based low-orbit satellite signal acquisition terminal can configure the frequency search of the relevant acquisition module according to the predicted Doppler frequency shift during the entry and exit time of the low-orbit satellite, and reduce the number of frequency points searched and the search range of the frequency points through prior information (predicted entry and exit time and Doppler frequency shift) to reduce the search time and complexity in the frequency dimension, avoid interference introduction during full-frequency search, and reduce interference from irrelevant frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is an application scenario diagram of a low-orbit satellite signal acquisition method in an embodiment;

[0054] Figure 2 A schematic diagram of a flow chart of a method for capturing a low-orbit satellite signal in one embodiment;

[0055] Figure 3 A frame format diagram of a low-orbit satellite transmitting end of a low-orbit satellite signal acquisition method in one embodiment;

[0056] Figure 4 is a structural block diagram of a low-orbit satellite signal acquisition device in one embodiment;

[0057] Figure 5 A diagram of a partial working process of a low-orbit satellite signal acquisition device in one embodiment. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application 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 application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0059] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "multiple groups" means at least two groups, such as two groups, three groups, etc., unless otherwise clearly and specifically defined.

[0060] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0061] In addition, the technical solutions between the various embodiments of the present application can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0062] The present application provides a low-orbit satellite signal acquisition method, which can be applied to Figure 1 In the application scenario diagram shown, the terminal 102 communicates with the server 104 through the network, and the terminal 102 may include but is not limited to various personal computers, laptops, smart phones, tablet computers and portable wearable devices, and the server 104 may be various portal websites, servers corresponding to the backend of the work system, etc.

[0063] This application provides a low-orbit satellite signal acquisition method, such as Figure 2 The flowchart shown in FIG. 1 shows a method for applying the method to Figure 1 The following is an example of a terminal in the example, including:

[0064] Step 202: Acquire a radio frequency signal sent by a low-orbit satellite, and obtain a zero intermediate frequency signal according to the radio frequency signal.

[0065] Specifically:

[0066] Obtain the radio frequency signal sent by the low-orbit satellite, and obtain the intermediate frequency signal after radio frequency down-conversion;

[0067] Performing analog-to-digital conversion (ADC) sampling on the intermediate frequency signal to obtain an intermediate frequency sampling signal;

[0068] The intermediate frequency sampling signal is digitally down-converted to zero intermediate frequency to obtain a zero intermediate frequency signal.

[0069] In this step, if Figure 3 The frame format of the low-orbit satellite transmitter shown in the figure, the pilot sequence in the frame header used for capture in the low-orbit satellite transmission frame is a pseudo-random (Pseudo-Noise, PN) sequence known to both the transmitter and the receiver, that is, a pilot pseudo-random sequence (which can be obtained according to the prior art), wherein the bit "0" in the pilot segment and the data segment information is converted to "+1" after bipolar IQ conversion, and the bit "1" is converted to "-1" after bipolar IQ conversion, and then modulated to radio frequency by the carrier and sent out by the antenna of the low-orbit satellite. The capture of the ground low-orbit satellite signal capture terminal is to detect the presence or absence of the signal by capturing the pilot segment signal in the frame signal reaching the ground from the low-orbit satellite and estimating the starting data position and Doppler frequency deviation of the signal of the low-orbit satellite transmission frame.

[0070] Step 204, obtain the orbital parameters, current time and current position of the low-orbit satellite, and predict the entry and exit time of the low-orbit satellite relative to the ground from the current time to multiple hours in the future, the minimum Doppler shift during the entry and exit time, and the maximum Doppler shift during the entry and exit time.

[0071] In this step, the orbital parameters of the low-orbit satellite, that is, the two-row elements of the low-orbit satellite, can be obtained according to the existing technology.

[0072] The specific forecasting process is an existing technology, for example, using a satellite forecasting model (such as SGP4 (Simplified General Perturbations Version 4th) satellite orbit motion model) for forecasting, and the satellite forecasting model includes the motion laws of low-orbit satellites.

[0073] The minimum Doppler shift within the entry and exit time and the maximum Doppler shift within the entry and exit time constitute the Doppler shift range.

[0074] Step 206, make a judgment based on the current time and the entry and exit time of the low-orbit satellite. If it is judged that the current time is within the entry and exit time of the low-orbit satellite, obtain the conjugate multiplication result based on the zero intermediate frequency signal; obtain the discrete Fourier transform result based on the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time.

[0075] Specifically:

[0076] The current time and the entry and exit time of the low-orbit satellite are judged. If the current time is judged to be within the entry and exit time of the low-orbit satellite, the zero intermediate frequency signal and the pilot pseudo-random sequence are conjugate multiplied in the time dimension to obtain the conjugate multiplication result;

[0077] According to the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time, a discrete Fourier transform calculation is performed in the frequency dimension to obtain a discrete Fourier transform result.

[0078] More specifically:

[0079] According to the current time and the entry and exit time of the low-orbit satellite, it is judged whether the current time is within the entry and exit time of the low-orbit satellite;

[0080] If it is determined that the current time is within the entry and exit time of the low-orbit satellite, the zero intermediate frequency signal and the pilot pseudo-random sequence are conjugate multiplied in the time dimension to obtain the conjugate multiplication result:

[0081]

[0082] In the formula, s t (n) is the conjugate multiplication result, M is the number of points of the pilot pseudo-random sequence, s(n) is the zero intermediate frequency signal, conj(.) is the conjugate conversion, and pn(n) is the pilot pseudo-random sequence (which can be obtained by the prior art);

[0083] According to the conjugate multiplication result, the minimum Doppler shift during the entry and exit time, and the maximum Doppler shift during the entry and exit time, a discrete Fourier transform (DFT) calculation is performed in the frequency dimension to obtain the discrete Fourier transform result:

[0084]

[0085] In the formula, s f(k) is the discrete Fourier transform result, M is the number of points of the pilot pseudo-random sequence, that is, the coherent integration length of DFT, s t (n) is the result of conjugate multiplication, j is the imaginary number sign, k = floor (f dn / f step ),floor(f dn / f step) +1,…,ceil(f up / f step ), where floor(.) is rounded down, ceil(.) is rounded up, and f step is the frequency search interval of discrete Fourier transform, f dn is the minimum Doppler frequency shift during the entry and exit time, f up is the maximum Doppler shift during the entry and exit time.

[0086] In this step, if it is determined that the current time is not within the entry and exit time of the low-orbit satellite, the calculation channels of the conjugate multiplication result and the discrete Fourier transform result are closed.

[0087] Step 208, judging based on the discrete Fourier transform result, if it is judged that the capture is successful, calculating the captured Doppler frequency deviation result, and outputting the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal and the data segment of the zero intermediate frequency signal as the capture result.

[0088] Specifically: according to the discrete Fourier transform result, the peak value, mean value and peak index of the signal are obtained, and it is determined whether the capture is successful; if the capture is determined to be successful, the Doppler frequency deviation result obtained by the capture is calculated according to the peak index, and the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal and the data segment of the zero intermediate frequency signal are output as the capture result; if it is determined that the capture fails, the forecast is re-performed and the next round of capture is carried out.

[0089] Among them: according to the discrete Fourier transform result, the peak value, mean value and peak index of the signal are obtained, and whether the capture is successful is judged, including: according to the discrete Fourier transform result, the peak value, mean value and peak index of the signal are obtained; according to the peak value and mean value, the peak-to-average ratio is calculated; the peak-to-average ratio is compared with the capture success threshold to judge whether the capture is successful.

[0090] In this step, the capture success threshold is an empirical value, which can be set or adjusted by software according to the prior art. How to judge whether the capture is successful belongs to the prior art and will not be described in detail here.

[0091] The above-mentioned low-orbit satellite signal acquisition method is a technology for predicting Doppler frequency shift based on the satellite orbit motion model. By analyzing the orbital parameters and motion laws of the low-orbit satellite, the entry and exit time and Doppler frequency shift of the low-orbit satellite relative to the ground low-orbit satellite signal acquisition terminal in the future are predicted. On this basis, the ground low-orbit satellite signal acquisition terminal captures the low-orbit satellite transmission signal. Compared with the traditional method, it can:

[0092] 1) Predict the entry and exit times and Doppler shift of low-orbit satellite signals in advance;

[0093] 2) The ground-based low-orbit satellite signal acquisition terminal can control the switch of acquisition-related modules according to the predicted entry and exit time of the low-orbit satellite to save power consumption;

[0094] 3) The ground-based low-orbit satellite signal acquisition terminal can configure the frequency search of the relevant acquisition module according to the predicted Doppler frequency shift during the entry and exit time of the low-orbit satellite, and reduce the number of frequency points searched and the search range of the frequency points through prior information (predicted entry and exit time and Doppler frequency shift) to reduce the search time and complexity in the frequency dimension, avoid interference introduction during full-frequency search, and reduce interference from irrelevant frequencies.

[0095] It should be understood that although Figure 2 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 2 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0096] The present application also provides a low-orbit satellite signal acquisition device, such as Figure 4 As shown, in one embodiment, it includes: a front-end unit and a capture processing unit.

[0097] The front-end unit is used to acquire the radio frequency signal sent by the low-orbit satellite and obtain the zero intermediate frequency signal according to the radio frequency signal. The front-end unit includes: an acquisition module, a sampling module and a frequency conversion module. In the front-end unit, the acquisition module, the sampling module and the frequency conversion module are connected in sequence.

[0098] The acquisition module is used to acquire the radio frequency signal sent by the low-orbit satellite and perform radio frequency down-conversion on the radio frequency signal to obtain an intermediate frequency signal.

[0099] The sampling module is used to perform analog-to-digital conversion sampling on the intermediate frequency signal to obtain an intermediate frequency sampling signal.

[0100] The frequency conversion module is used to digitally down-convert the intermediate frequency sampling signal to a zero intermediate frequency to obtain a zero intermediate frequency signal.

[0101] The capture processing unit includes: a control module, a positioning module, a storage module, a conversion module and a correlator module. In the capture processing unit, the control module is respectively connected to the positioning module, the storage module, the conversion module and the correlator module, and the control module is also connected to the front unit.

[0102] The control module is used to obtain the orbital parameters of the low-orbit satellite, and in combination with the current time and the current positioning, predict the low-orbit satellite entry and exit time relative to the ground from the current time to multiple hours in the future, the minimum Doppler frequency shift during the entry and exit time, and the maximum Doppler frequency shift during the entry and exit time; it is also used to judge whether the current time is within the low-orbit satellite entry and exit time according to the current time and the low-orbit satellite entry and exit time; it is also used to send the zero intermediate frequency signal to the correlator module; it is also used to judge whether the capture is successful according to the discrete Fourier transform result, and when it is judged that the capture is successful, calculate the Doppler frequency deviation result obtained by the capture, and output the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal, and the data segment of the zero intermediate frequency signal as the capture result;

[0103] The positioning module is used to obtain the current time and current position of the capture device (i.e. the current latitude and longitude information);

[0104] The storage module is used to store the entry and exit time, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time;

[0105] The transformation module is used to obtain a discrete Fourier transform result according to the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time;

[0106] The correlator module is used to determine when the current time is within the entry and exit time of the low-orbit satellite, and obtain the conjugate multiplication result based on the zero intermediate frequency signal.

[0107] The working process of a low-orbit satellite signal capture device (the low-orbit satellite signal capture device is used as a ground low-orbit satellite signal capture terminal) is as follows:

[0108] 1) The front-end unit receives the RF signal sent by the low-orbit satellite and converts the received RF signal r(t) to an intermediate frequency signal r through RF down-conversion. d (t).

[0109] 2) For the intermediate frequency signal r d (t) Perform analog-to-digital conversion sampling to obtain the intermediate frequency sampling signal sIF (n).

[0110] 3) Sample the intermediate frequency signal s IF (n) is digitally down-converted to zero intermediate frequency to obtain a zero intermediate frequency signal s(n) (this signal is a digital signal).

[0111] 4) Input the zero intermediate frequency digital signal s(n) into the capture processing unit and enter the low-orbit satellite signal capture processing flow, as follows: Figure 5 shown.

[0112] 4.1) The capture processing unit uses the control module and the positioning module (e.g., Global Navigation Satellite System (GNSS) module) to calculate the low-orbit satellite signal relative to the ground within the forecast period from the current time to the next N hours (parameter N can be set) to capture the low-orbit satellite entry and exit time (i.e., entry and exit time) t of the terminal 0 ~t 1 and entry and exit time t 0 ~t 1 The minimum Doppler frequency shift f dn and the maximum Doppler shift f up , and the entry and exit time t 0 ~t 1 , minimum Doppler frequency shift f dn and the maximum Doppler shift f up Store in storage module.

[0113] 4.2) The capture processing unit obtains the current time and current position of the low-orbit satellite signal capture device through the positioning module, obtains the stored low-orbit satellite entry and exit time through the storage module, and uses the control module to determine whether the current time is within the low-orbit satellite entry and exit time. If the current time is not within the low-orbit satellite entry and exit time, the control module closes the conversion module and the correlator module, and enters a loop judgment state (continuously judging whether the current time is within the low-orbit satellite entry and exit time). If the current time is within the low-orbit satellite signal entry and exit time, the conversion module and the correlator module are turned on and calculations are performed.

[0114] 4.3) The control module sends the zero intermediate frequency signal s(n) to the correlator module, and the correlator module performs conjugate multiplication calculation on s(n) and the known pilot pseudo-random sequence in the time dimension to obtain the conjugate multiplication result s t (n).

[0115] 4.4) After the correlator module has finished calculating, the control module will calculate the result of the correlator, i.e. the conjugate multiplication result s t (n) and the minimum Doppler frequency shift f stored in the storage moduledn and the maximum Doppler shift f up The transformation module uses the minimum Doppler frequency shift f dn and the maximum Doppler shift f up , will s t (n) Perform discrete Fourier transform calculation in the frequency dimension to obtain the discrete Fourier transform result s f (k). After the discrete Fourier transform is calculated, the peak value peek, mean value mean, and peak index idx of the discrete Fourier transform of the signal are obtained, and the results are passed to the control module. The control module calculates the peak-to-average ratio based on the peak value peek and mean value mean, and compares it with the capture success threshold threshold to determine whether the capture is successful.

[0116] 4.5) If the capture is judged to be successful, the control module calculates the captured Doppler frequency deviation result fdopper according to the peak index of the discrete Fourier transform (how to calculate is the prior art), and stores the zero intermediate frequency data s(n) containing the pilot segment and the data segment into the storage module, and outputs it as the capture result; if the capture is judged to be unsuccessful, it means that the signal segment does not contain the pilot signal of the low-orbit satellite signal, then enter 4.1 to loop and perform the next round of capture (the capture process is moment-to-moment capture).

[0117] For the specific definition of a low-orbit satellite signal capture device, please refer to the definition of a low-orbit satellite signal capture method above, which will not be repeated here. Each module in the above device can be implemented in whole or in part by software, hardware and a combination thereof. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0118] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0119] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0120] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for capturing low-orbit satellite signals, characterized in that: include: Acquire the radio frequency signal sent by the low-orbit satellite, and obtain the zero intermediate frequency signal according to the radio frequency signal; Obtain the orbital parameters, current time and current position of the low-orbit satellite, and predict the entry and exit time of the low-orbit satellite relative to the ground from the current time to multiple hours in the future, the minimum Doppler shift during the entry and exit time, and the maximum Doppler shift during the entry and exit time; The judgment is made based on the current time and the entry and exit time of the low-orbit satellite. If it is judged that the current time is within the entry and exit time of the low-orbit satellite, the conjugate multiplication result is obtained based on the zero intermediate frequency signal; The discrete Fourier transform result is obtained according to the conjugate multiplication result, the minimum Doppler frequency shift during the entry and exit time, and the maximum Doppler frequency shift during the entry and exit time; A judgment is made based on the discrete Fourier transform result. If the capture is successful, the Doppler frequency deviation result obtained by the capture is calculated, and the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal, and the data segment of the zero intermediate frequency signal are output as the capture result.

2. A low-orbit satellite signal acquisition method according to claim 1, characterized in that: The judgment is made based on the current time and the entry and exit time of the low-orbit satellite. If it is judged that the current time is within the entry and exit time of the low-orbit satellite, the conjugate multiplication result is obtained based on the zero intermediate frequency signal; According to the conjugate multiplication result, the minimum Doppler frequency shift during the entry and exit time, and the maximum Doppler frequency shift during the entry and exit time, the discrete Fourier transform result is obtained, including: According to the current time and the entry and exit time of the low-orbit satellite, it is judged whether the current time is within the entry and exit time of the low-orbit satellite; If it is determined that the current time is within the entry and exit time of the low-orbit satellite, the zero intermediate frequency signal and the pilot pseudo-random sequence are conjugate multiplied in the time dimension to obtain a conjugate multiplication result; According to the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time, a discrete Fourier transform calculation is performed in the frequency dimension to obtain a discrete Fourier transform result.

3. A low-orbit satellite signal acquisition method according to claim 2, characterized in that: According to the conjugate multiplication result, the minimum Doppler frequency shift during the entry and exit time, and the maximum Doppler frequency shift during the entry and exit time, a discrete Fourier transform calculation is performed in the frequency dimension to obtain the discrete Fourier transform result, including: In the formula, s f (k) is the discrete Fourier transform result, M is the number of points in the pilot pseudo-random sequence, s t (n) is the result of conjugate multiplication, j is the imaginary number sign, k = floor (f dn / f step ),floor(f dn / f step) +1,…,ceil(f up / f step ), where floor(.) is rounded down, ceil(.) is rounded up, and f step is the frequency search interval of discrete Fourier transform, f dn is the minimum Doppler frequency shift during the entry and exit time, f up is the maximum Doppler shift during the entry and exit time.

4. A low-orbit satellite signal acquisition method according to claim 3, characterized in that: The zero intermediate frequency signal and the pilot pseudo-random sequence are conjugate multiplied in the time dimension to obtain the conjugate multiplication result, including: In the formula, s t (n) is the conjugate multiplication result, M is the number of points of the pilot pseudo-random sequence, s(n) is the zero intermediate frequency signal, conj(.) is the conjugate conversion, and pn(n) is the pilot pseudo-random sequence.

5. A low-orbit satellite signal acquisition method according to any one of claims 1 to 4, characterized in that: If it is determined that the current time is not within the entry and exit time of the low-orbit satellite, the calculation channel of the conjugate multiplication result and the discrete Fourier transform result is closed.

6. A method for capturing low-orbit satellite signals according to any one of claims 1 to 4, characterized in that: The discrete Fourier transform result is used to determine if the capture is successful. The Doppler frequency deviation result obtained by the capture is calculated, and the conjugate multiplication result is output as the capture result, including: According to the discrete Fourier transform results, the peak value, mean value and peak index of the signal are obtained, and it is judged whether the capture is successful; If the capture is successful, the Doppler frequency deviation result obtained by the capture is calculated according to the peak index, and the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal and the data segment of the zero intermediate frequency signal are output as the capture result; If it is judged that the capture fails, the forecast is repeated and the next round of capture is carried out.

7. A low-orbit satellite signal acquisition method according to claim 6, characterized in that: According to the discrete Fourier transform results, the peak value, mean value and peak index of the signal are obtained, and whether the capture is successful is determined, including: According to the discrete Fourier transform results, the peak value, mean value and peak index of the signal are obtained; Based on the peak value and the mean value, the peak-to-average ratio is calculated; Compare the peak-to-average ratio with the capture success threshold to determine whether the capture is successful.

8. A method for capturing low-orbit satellite signals according to any one of claims 1 to 4, characterized in that: Obtain the radio frequency signal sent by the low-orbit satellite and obtain the zero intermediate frequency signal according to the radio frequency signal, including: Obtain the radio frequency signal sent by the low-orbit satellite, and obtain the intermediate frequency signal after radio frequency down-conversion; Perform analog-to-digital conversion sampling on the intermediate frequency signal to obtain an intermediate frequency sampling signal; The intermediate frequency sampling signal is digitally down-converted to zero intermediate frequency to obtain a zero intermediate frequency signal.

9. A low-orbit satellite signal acquisition device, characterized in that: A low-orbit satellite signal capture method according to any one of claims 1 to 8, comprising: a front-end unit and a capture processing unit; The front-end unit is used to obtain the radio frequency signal sent by the low-orbit satellite and obtain the zero intermediate frequency signal according to the radio frequency signal; The capture processing unit includes: a control module, a positioning module, a storage module, a conversion module and a correlator module, the control module is respectively connected to the positioning module, the storage module, the conversion module and the correlator module, and the control module is also connected to the front unit; The control module is used to obtain the orbital parameters of the low-orbit satellite, and in combination with the current time and the current positioning, predict the low-orbit satellite entry and exit time relative to the ground from the current time to multiple hours in the future, the minimum Doppler frequency shift during the entry and exit time, and the maximum Doppler frequency shift during the entry and exit time; it is also used to judge whether the current time is within the low-orbit satellite entry and exit time according to the current time and the low-orbit satellite entry and exit time; it is also used to send the zero intermediate frequency signal to the correlator module; it is also used to judge whether the capture is successful according to the discrete Fourier transform result, and when it is judged that the capture is successful, calculate the Doppler frequency deviation result obtained by the capture, and output the Doppler frequency deviation result, the pilot segment of the zero intermediate frequency signal, and the data segment of the zero intermediate frequency signal as the capture result; The positioning module is used to obtain the current time and current location; The storage module is used to store the entry and exit time, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time; The transformation module is used to obtain a discrete Fourier transform result according to the conjugate multiplication result, the minimum Doppler frequency shift within the entry and exit time, and the maximum Doppler frequency shift within the entry and exit time; The correlator module is used to determine when the current time is within the entry and exit time of the low-orbit satellite, and obtain the conjugate multiplication result based on the zero intermediate frequency signal.

10. The low-orbit satellite signal acquisition device according to claim 9, characterized in that: The front unit includes: an acquisition module, a sampling module and a frequency conversion module which are connected in sequence; The acquisition module is used to acquire the radio frequency signal sent by the low-orbit satellite, perform radio frequency down-conversion, and obtain the intermediate frequency signal; The sampling module is used to perform analog-to-digital conversion sampling on the intermediate frequency signal to obtain an intermediate frequency sampling signal; The frequency conversion module is used to digitally down-convert the intermediate frequency sampling signal to a zero intermediate frequency to obtain a zero intermediate frequency signal.

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