阅读说明：本技术 一种改进的高动态捕获方法、装置、设备及存储介质 (Improved high dynamic capture method, device, equipment and storage medium ) 是由 符春 张雪松 陈国弘 许图 于 2021-08-25 设计创作，主要内容包括：本发明提供一种改进的高动态捕获方法、装置、设备及存储介质,通过预设方法,对预设的初始多普勒搜索范围采用初始频率步长进行搜索,搜索到的第一颗卫星,根据第一颗卫星得到的多普勒频率作为搜索中心,并根据接收机在静止状态时,卫星与接收机之间因多普勒效应产生的频移范围,得到目标多普勒搜索范围,根据预设的频率步长,进行频率区间划分,再分别对每个频率区间进行搜索,捕获卫星信号。该方案利用了卫星相对运动保持不变,可重新设定频率搜索范围,因此可缩小需要搜索的频率范围,也减小了搜索次数,从而缩短了捕获卫星的时间,对硬件资源开销也有较大的降低。(The invention provides an improved high dynamic capture method, device, equipment and storage medium, which search a preset initial Doppler search range by adopting an initial frequency step length through a preset method, search a first searched satellite, obtain a target Doppler search range according to the Doppler frequency obtained by the first satellite, the frequency shift range generated between the satellite and a receiver due to the Doppler effect when the receiver is in a static state, divide frequency intervals according to the preset frequency step length, and respectively search each frequency interval to capture satellite signals. The scheme utilizes the fact that the relative motion of the satellite is kept unchanged, and the frequency searching range can be reset, so that the frequency range needing to be searched can be shortened, the searching times are also reduced, the time for capturing the satellite is shortened, and the cost of hardware resources is also greatly reduced.)

1. An improved high dynamic acquisition method, comprising:

based on the known satellite number, searching a first satellite in a preset initial frequency searching range according to a preset method and a preset frequency step length to obtain a corresponding Doppler frequency as an initial Doppler frequency;

when the receiver is in a static state, acquiring a frequency shift range between a first satellite and the receiver due to Doppler effect;

updating the initial Doppler search range according to the frequency shift range by taking the initial Doppler frequency as a search center to obtain a target Doppler frequency;

dividing frequency intervals according to the target Doppler search range and the frequency step length;

and searching each frequency interval respectively to acquire a new satellite signal.

2. The method according to claim 1, wherein after the step of searching for the first satellite in the preset initial frequency search range according to the preset method and frequency step based on the known satellite number to obtain the corresponding doppler frequency as the initial doppler frequency, the method further comprises:

if the first satellite search fails, the satellite codes are replaced, and the search is carried out again until the satellite signals are searched.

3. The method of claim 1, wherein the predetermined method is embodied as one of a two-dimensional search, an FFT-based time-domain parallel acquisition, and a PMF-FFT acquisition.

4. The method according to claim 1, wherein the step of updating the initial doppler search range according to the frequency shift range by using the doppler frequency of the first satellite as a search center to obtain the target doppler frequency further comprises:

and updating the initial Doppler frequency according to the deviation of the RF clock crystal oscillator of the receiver.

5. The method of claim 1, wherein said step of separately searching each frequency bin to acquire a new satellite signal further comprises:

when a new satellite signal is acquired, the doppler frequency of the new satellite signal is set to the initial doppler frequency.

6. The method of claim 1, wherein before the step of dividing the frequency interval according to the target doppler search range and the frequency step, further comprising:

receiving and processing external ephemeris information, wherein the external ephemeris information comprises time information and position information;

calculating the position and the speed of a satellite corresponding to the external ephemeris, the pitch angle of the satellite and the theoretical Doppler frequency according to the time information and the position information;

screening the satellites according to a preset pitch angle threshold value to obtain a plurality of target satellites;

after error correction is carried out on the theoretical Doppler frequencies of the target satellites, the Doppler frequencies of the target satellites are obtained, and satellite search is carried out;

after the searching of a plurality of target satellites is finished, selecting the Doppler frequency of the target satellite searched finally as the initial Doppler frequency;

and taking the initial Doppler frequency as a search center, and obtaining the target Doppler frequency according to the frequency shift.

7. The method according to claim 6, wherein after performing the error correction on the theoretical doppler frequencies of the target satellites to obtain doppler frequencies of the target satellites, the method further comprises:

and if the search of the plurality of target satellites fails, searching according to a preset frequency step length by taking the theoretical Doppler frequency as a central point to acquire satellite signals.

8. An improved high dynamic acquisition device, comprising a first satellite search module, a frequency shift range acquisition module, a search range acquisition module, a frequency interval division module and a satellite signal acquisition module, wherein:

the first satellite searching module is used for searching a first satellite in a preset initial frequency searching range according to a preset method and a preset frequency step length based on a known satellite number to obtain a corresponding Doppler frequency as an initial Doppler frequency;

the frequency shift range acquisition module is used for acquiring a frequency shift range generated between the first satellite and the receiver due to Doppler effect when the receiver is in a static state;

the search range acquisition module is used for updating the initial Doppler search range according to the frequency shift range by taking the Doppler frequency of the first satellite as a search center to obtain a target Doppler frequency;

the frequency interval division module is used for dividing frequency intervals according to the target Doppler search range and the frequency step length;

the satellite signal acquisition module is used for searching each frequency interval respectively and acquiring a new satellite signal.

9. An apparatus comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the steps of the method of any of claims 1 to 7 are implemented when the computer program is executed by the processor.

10. A storage medium having a computer program stored thereon, the computer program, when being executed by a processor, realizing the steps of the method of any one of claims 1 to 7.

Technical Field

The present invention relates to the field of signal acquisition technologies, and in particular, to an improved high dynamic acquisition method, apparatus, device, and storage medium.

Background

In the case of stationary or low-speed motion, the two-dimensional search technology is mostly adopted for satellite signal acquisition. The two-dimensional search is influenced by the Doppler frequency between the receiver and the satellite, and the larger the Doppler frequency is, the more time is needed for processing, so that the acquisition speed is low, and the requirements of environments such as high dynamics and the like on real-time performance cannot be met. With the development of technologies such as digital signal processing and the like, some new capture strategies are researched and applied, in the aspect of high dynamic state, a series-parallel combined capture method is adopted, a two-dimensional search range of Doppler frequency offset and pseudo-random code is divided into sub-intervals, and a parallel channel is utilized to save capture time. There are three major capture methods available: two-dimensional search, FFT-based time-domain parallel search, segmented matched filtering, and FFT time-frequency two-dimensional search (PMF-FFT).

However, the current capture algorithm has the following problems: (1) the doppler shift is large because of the high-speed motion of the carrier, and besides the doppler effect generated by the satellite motion, the carrier itself also generates a very large doppler effect, and the carrier frequency has a frequency shift of several kHz or even hundreds of kHz, and when a satellite signal is acquired, more frequency searches need to be performed, which results in a great increase in the acquisition time. (2) The hardware resource overhead is large, and the realization is complex. The parallel capturing algorithm based on FFT needs to perform FFT-IFFT besides two multipliers, adders and integrators, the number of points of each FFT change is two ranging code periods, the occupied resources are large, the calculation complexity is high, and the Doppler search still needs to be performed by adopting a frequency scanning strategy in a frequency domain.

Disclosure of Invention

In view of the foregoing, there is a need to provide an improved high dynamic capture method, apparatus, device and storage medium.

An improved high dynamic acquisition method, the method comprising: based on the known satellite number, searching a first satellite in a preset initial frequency searching range according to a preset method and a preset frequency step length to obtain a corresponding Doppler frequency as an initial Doppler frequency; when the receiver is in a static state, acquiring a frequency shift range between a first satellite and the receiver due to Doppler effect; updating the initial Doppler search range according to the frequency shift range by taking the initial Doppler frequency as a search center to obtain a target Doppler frequency; dividing frequency intervals according to the target Doppler search range and the frequency step length; and searching each frequency interval respectively to acquire a new satellite signal.

In one embodiment, after the step of performing a search for a first satellite in a preset initial frequency search range according to a preset method and a preset frequency step based on a known satellite number to obtain a corresponding doppler frequency as an initial doppler frequency, the method further includes: if the first satellite search fails, the satellite code is changed, and the search is carried out again until the satellite signal is searched.

In one embodiment, the preset method is specifically one of two-dimensional search, FFT-based time-domain parallel acquisition, and PMF-FFT acquisition.

In one embodiment, before the step of updating the initial doppler search range according to the frequency shift range by using the doppler frequency of the first satellite as a search center to obtain a target doppler frequency, the method further includes: and updating the initial Doppler frequency according to the deviation of the RF clock crystal oscillator of the receiver.

In one embodiment, after the step of separately searching each frequency interval and acquiring a new satellite signal, the method further includes: when a new satellite signal is acquired, the doppler frequency of the new satellite signal is set to the initial doppler frequency.

In one embodiment, before the step of dividing the frequency interval according to the target doppler search range and the frequency step, the method further includes: receiving and processing external ephemeris information, wherein the external ephemeris information comprises time information and position information; calculating the position and the speed of a satellite corresponding to the external ephemeris, the pitch angle of the satellite and the theoretical Doppler frequency according to the time information and the position information; screening the satellites according to a preset pitch angle threshold value to obtain a plurality of target satellites; after error correction is carried out on the theoretical Doppler frequencies of the target satellites, the Doppler frequencies of the target satellites are obtained, and satellite search is carried out; after the searching of a plurality of target satellites is finished, selecting the Doppler frequency of the target satellite searched finally as the initial Doppler frequency; and taking the initial Doppler frequency as a search center, and obtaining the target Doppler frequency according to the frequency shift.

In one embodiment, after performing error correction on the theoretical doppler frequencies of the multiple target satellites to obtain the doppler frequencies of the multiple target satellites, the satellite searching step further includes: and if the search of the plurality of target satellites fails, searching according to a preset frequency step length by taking the theoretical Doppler frequency as a central point to acquire satellite signals.

An improved high dynamic capturing device comprises a first satellite searching module, a frequency shift range acquiring module, a searching range acquiring module, a frequency interval dividing module and a satellite signal capturing module, wherein: the first satellite searching module is used for searching a first satellite in a preset initial frequency searching range according to a preset method and a preset frequency step length based on a known satellite number to obtain a corresponding Doppler frequency as an initial Doppler frequency; the frequency shift range acquisition module is used for acquiring a frequency shift range generated between the first satellite and the receiver due to Doppler effect when the receiver is in a static state; the search range acquisition module is used for updating the initial Doppler search range according to the frequency shift range by taking the Doppler frequency of the first satellite as a search center to obtain a target Doppler frequency; the frequency interval division module is used for dividing frequency intervals according to the target Doppler search range and the frequency step length; the satellite signal acquisition module is used for searching each frequency interval respectively and acquiring a new satellite signal.

An apparatus comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of an improved high dynamic capture method as described in the various embodiments above when executing the program.

A storage medium having stored thereon a computer program which, when executed by a processor, carries out the steps of an improved high dynamic capture method as described in the various embodiments above.

According to the improved high dynamic capturing method, the improved high dynamic capturing device, the improved high dynamic capturing equipment and the improved high dynamic capturing storage medium, through a preset method, a preset initial Doppler search range is searched by adopting an initial frequency step length, a searched first satellite is used as a search center according to Doppler frequency obtained by the first satellite, a target Doppler search range is obtained according to a frequency shift range generated between the satellite and a receiver due to Doppler effect when the receiver is in a static state, frequency intervals are divided according to the preset frequency step length, then each frequency interval is searched respectively, and satellite signals are captured; the relative motion of the satellite is kept unchanged, and the frequency searching range can be reset, so that the frequency range to be searched can be shortened, the searching times are also reduced, the time for capturing the satellite is shortened, and the hardware resource overhead is also greatly reduced.

Drawings

FIG. 1 is a schematic flow chart diagram of an improved high dynamic capture method in one embodiment;

FIG. 2 is a flow diagram illustrating ephemeris information assisted acquisition, according to an embodiment;

FIG. 3 is a block diagram of an improved high dynamic capture device in one embodiment;

fig. 4 is an internal structural diagram of the device in one embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings by way of specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The improved high dynamic acquisition method provided by the application can be applied to the application environment of acquisition of satellite signals. The acquisition of the satellite signal is mainly a series of operations on the signal after frequency down-conversion, amplification and analog-to-digital conversion (the satellite signal is submerged in noise), the satellite signal is extracted from the noise, and a rough estimation of its pseudo code phase and carrier frequency is provided. The main processes of the series of operations are as follows: the receiver locally replicates the spreading code and carrier in the satellite signal and, using the properties of pseudocode autocorrelation and cross-correlation, produces the maximum correlation only if the code phase and carrier frequency of the reconstructed signal match the received satellite signal. Thus, the signal acquisition process is effectively a two-dimensional search process of the pseudo-code phase and carrier frequency.

Theoretical analysis in the prior art shows that if frequency offset search is used, the step length is set to be 500Hz, and for acquisition of a certain satellite, the acquisition method needs to search 41 × 2046 (the frequency point number is multiplied by the code phase, 41 indicates that the searched frequency range is [ -10Khz, 10Khz ], and 2046 is the number of B1 code phases) units in total. The process can be completed only by a digital correlator, and the hardware is easy to design and implement. However, the number of search range units is large, the calculation amount for searching each satellite is large, and the acquisition time is long.

In one embodiment, as shown in FIG. 1, there is provided an improved high dynamic capture method comprising the steps of:

s110, based on the known satellite number, searching a preset initial frequency searching range for a first satellite according to a preset method and a preset frequency step length, and obtaining a corresponding Doppler frequency as an initial Doppler frequency.

In one embodiment, the preset method in step S110 is specifically one of two-dimensional search, FFT-based time-domain parallel acquisition, and PMF-FFT acquisition.

Specifically, first, the first satellite needs to be determined first, and then the subsequent calculation can be performed according to the doppler frequency of the first satellite, so that in order to improve the efficiency of acquiring the first satellite, the acquisition of the first satellite can be performed by combining any one of serial search, FFT-based time domain parallel acquisition, and PMF-FFT acquisition, and preferably, the acquisition of the first satellite is performed by using the PMF-FFT method. And taking the Doppler frequency of the searched first satellite as the initial Doppler frequency.

In one embodiment, after step S110, the method further includes: if the first satellite search fails, the satellite codes are replaced, and the search is carried out again until the satellite signals are searched. Specifically, when the first satellite is not searched by using the code of the first satellite, the satellite signal search is performed by replacing other known satellite codes, and if the first satellite is not searched, the satellite number is continuously replaced until the satellite signal is searched.

S120, when the receiver is in a static state, acquiring a frequency shift range between the first satellite and the receiver due to the Doppler effect.

Specifically, although the center frequency of the GNSS satellite transmission carrier is a constant, the relative motion between the GNSS receiver and the satellite generates doppler shift, so the carrier frequency of the satellite received by the GNSS receiver varies. Doppler shift versus relative motion:

in the formula f_dmIs Doppler shift, f_rIs the carrier frequency, v, of the satellite signal_dmIs the relative velocity of the satellite and the receiver, and c is the speed of light. Taking the carrier of 1575.42MHz, L1 on the GPS satellite as an example, the receiver does not move, the relative velocity between the GNSS receiver and the satellite is 929m/s, and then the frequency shift due to the doppler effect is:

from the above results, it can be seen that the Doppler shift caused by the motion of the satellite is + -5 kHz. Assuming that the receiver moves relatively at 929m/s, which is the same speed as the satellite, the doppler shift due to the relative motion of the two will reach ± 10 kHz.

S130, the initial Doppler frequency is used as a search center, and the initial Doppler search range is updated according to the frequency shift range to obtain the target Doppler frequency.

Specifically, the relative motion between the satellites in the sky is the same whether the receiver is stationary or moving at a high speed, i.e., the difference between the doppler of each satellite relative to the receiver is the same in both states of the receiver, and as can be seen from the above example in step S130, the range of doppler frequencies is known as [ -5kHz, 5kHz when the receiver is stationary]According to this principle, it can be known that after the Doppler frequency f of the first satellite is obtained, the frequency search range can be reset to [ f-5kHz, f +5kHz]Thus, the Doppler frequency range to be searched for in acquisition can be narrowed. By the method, half of the time can be shortened on the basis of the original search strategy which is based onThe frequency range search of (2), wherein f is usually set to 0, thus the search times are increased by one time, and the search strategy of the scheme utilizes the fact that the relative motion of the satellite is kept unchanged, so that the search range is reduced, the search times are also reduced, and the time for capturing the satellite is shortened.

In one embodiment, before step S130, the method further includes: and updating the initial Doppler frequency according to the deviation of the RF clock crystal oscillator of the receiver. In particular, deviations in the receiver's own RF clock crystal can also produce an offset in the received signal carrier frequency. Theoretical calculations indicate that a crystal oscillator deviation of 1ppm can cause a frequency offset of 1.57kHz at the carrier frequency of L1 and a frequency offset of 1.56kHz at the frequency point of B1.

In one embodiment, as shown in fig. 2, before step S140, the method further includes: s141, receiving and processing external ephemeris information, wherein the external ephemeris information comprises time information and position information; s142, calculating the position and the speed of the satellite corresponding to the external ephemeris, the pitch angle of the satellite and the theoretical Doppler frequency according to the time information and the position information; s143, screening the satellites according to a preset pitch angle threshold value to obtain a plurality of target satellites; s144, correcting errors of the theoretical Doppler frequencies of the target satellites to obtain the Doppler frequencies of the target satellites, and searching the satellites; s145, after the searching of the plurality of target satellites is completed, selecting the Doppler frequency of the target satellite searched finally as the initial Doppler frequency; s146, the initial Doppler frequency is used as a search center, and the target Doppler frequency is obtained according to the frequency shift.

Specifically, the ephemeris information assistance may also play a very important role in high-dynamic applications, and the currently visible satellites may be known according to the ephemeris information, so that the search time may be greatly shortened. The approximate Doppler frequency of the satellite can be calculated according to the ephemeris information, and the search operation is performed by taking the Doppler frequency as a base point, so that the times of the search operation can be greatly reduced, and the acquisition speed and efficiency are improved, and the specific process is as follows:

receiving and processing external ephemeris information (including time information and position information); secondly, respectively calculating the position and the speed of the satellite corresponding to each ephemeris and the theoretical Doppler frequency (without the Doppler frequency generated by the crystal oscillator error of the receiver) of the receiver according to the time and the position; calculating the pitch angle of each satellite, selecting the satellite with the pitch angle larger than a threshold value, and performing preferential capture according to the calculated Doppler value; fourthly, after the screened satellites are searched, other satellites continue to be searched according to a serial search method or an FFT time domain search method.

In one embodiment, after step S144, the method further includes: and if the search of the plurality of target satellites fails, searching according to a preset frequency step length by taking the theoretical Doppler frequency as a central point to acquire satellite signals. Specifically, when the target satellite search fails, the frequency of [ -5kHz, 5kHz ] is scanned directly with the theoretical doppler frequency as a center point according to a preset frequency step.

S140, dividing the frequency interval according to the target Doppler search range and the frequency step.

In particular, assume that the receiver needs to search for a Doppler frequency range ofThe carrier frequency of the actual input signal is atWithin the range. If the frequency search step is f_stepThen all Doppler frequency points covering the search range are

In the formula, i represents the ith search.

Continuing the example above, only a frequency range of 10kHz needs to be searched, and (2 × 5/0.5+1) ═ 21 frequency searches are needed, calculated in steps of 500 Hz. No matter the classic two-dimensional serial search or the time domain search based on FFT is adopted, the search of frequency points can be reduced, and the higher the dynamic state is, the more the reduction is.

S150 searches each frequency interval to acquire a new satellite signal.

Specifically, each frequency interval is searched, and acquisition of a new satellite signal is achieved.

In one embodiment, after step S150, the method further includes: when a new satellite signal is acquired, the doppler frequency of the new satellite signal is set to the initial doppler frequency. Specifically, when a new satellite signal is acquired, the doppler frequency of the new satellite signal needs to be set as the initial doppler frequency, and then the above steps S130-S150 are repeated until all the acquisition is completed.

In the above embodiment, by using a preset method, a preset initial doppler search range is searched by using an initial frequency step length, a searched first satellite is used as a search center according to a doppler frequency obtained by the first satellite, a target doppler search range is obtained according to a frequency shift range generated between the satellite and a receiver due to a doppler effect when the receiver is in a stationary state, frequency intervals are divided according to the preset frequency step length, and then each frequency interval is searched respectively to capture a satellite signal; the relative motion of the satellite is kept unchanged, and the frequency searching range can be reset, so that the frequency range to be searched can be shortened, the searching times are also reduced, the time for capturing the satellite is shortened, and the hardware resource overhead is also greatly reduced.

In one embodiment, as shown in fig. 3, an improved high dynamic acquisition apparatus 200 is provided, which includes a first satellite search module 210, a stationary frequency shift calculation module 220, a search range acquisition module 230, a frequency interval division module 240, and a satellite signal acquisition module 250, wherein:

the first satellite search module 210 is configured to, based on a known satellite number, perform a first satellite search for a preset initial frequency search range according to a preset method and a preset frequency step length, and obtain a corresponding doppler frequency as an initial doppler frequency;

the frequency shift range obtaining module 220 is configured to obtain a frequency shift range between the first satellite and the receiver due to a doppler effect when the receiver is in a stationary state;

the search range acquisition module 240 is configured to update the initial doppler search range according to the frequency shift range by using the doppler frequency of the first satellite as a search center, so as to obtain a target doppler frequency;

the frequency interval division module 250 is configured to divide a frequency interval according to the target doppler search range and the frequency step;

the satellite signal acquisition module 260 is configured to search each frequency interval to acquire a new satellite signal.

In one embodiment, a device is provided, which may be a server, and its internal structure diagram may be as shown in fig. 4. The device includes a processor, a memory, a network interface, and a database connected by a system bus. Wherein the processor of the device is configured to provide computing and control capabilities. The memory of the device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The database of the device is used for storing configuration templates and also can be used for storing target webpage data. The network interface of the device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement an improved high dynamic capture method.

Those skilled in the art will appreciate that the configuration shown in fig. 4 is a block diagram of only a portion of the configuration associated with the present application and does not constitute a limitation on the devices to which the present application applies, and that a particular device may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.

In an embodiment, there is also provided a storage medium storing a computer program comprising program instructions which, when executed by a computer, cause the computer to perform the method according to the preceding embodiment, the computer may be part of an improved high dynamic capture device as mentioned above.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.

It will be apparent to those skilled in the art that the modules or steps of the invention described above may be implemented in a general purpose computing device, they may be centralized on a single computing device or distributed across a network of computing devices, and optionally they may be implemented in program code executable by a computing device, such that they may be stored on a computer storage medium (ROM/RAM, magnetic disks, optical disks) and executed by a computing device, and in some cases, the steps shown or described may be performed in an order different than that described herein, or they may be separately fabricated into individual integrated circuit modules, or multiple ones of them may be fabricated into a single integrated circuit module. Thus, the present invention is not limited to any specific combination of hardware and software.

The foregoing is a more detailed description of the present invention that is presented in conjunction with specific embodiments, and the practice of the invention is not to be considered limited to those descriptions. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.