CN116719063A - A method and system for rapid acquisition of ground-based navigation signals - Google Patents
A method and system for rapid acquisition of ground-based navigation signals Download PDFInfo
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
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- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
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Abstract
本发明公开了一种地基导航信号的快速捕获方法和系统。通过对数字信号正交下变频、低通滤波、重量化和重采样处理,获得重采样的I/Q基带信号,基于该信号实施捕获,在一个测距码周期内使用两组匹配滤波来检测,以采样点连续计数为时间戳采集捕获信息列表,根据时间戳计算捕获时隙值构成跳时图案子样本,完成跳时图案的捕获,根据两组匹配滤波积分值计算信号频率的估计,实现了地基导航信号时域、频域和发射时隙三维度的快速搜索,具有捕获速度快、信号频率估计范围大、有效抑制旁瓣干扰的优势。
The invention discloses a method and system for quickly acquiring ground-based navigation signals. Through orthogonal down-conversion, low-pass filtering, reweighting and resampling of the digital signal, the resampled I/Q baseband signal is obtained. Based on the signal, acquisition is performed and two sets of matched filters are used for detection within a ranging code period. , collect the capture information list with the continuous count of sampling points as the timestamp, calculate the capture time slot value according to the timestamp to form the time-hopping pattern sub-sample, complete the capture of the time-hopping pattern, and calculate the estimation of the signal frequency based on the two sets of matched filtering integral values to achieve It achieves rapid search in the three dimensions of time domain, frequency domain and transmission time slot of ground-based navigation signals, and has the advantages of fast acquisition speed, large signal frequency estimation range, and effective suppression of side lobe interference.
Description
技术领域Technical field
本发明涉及导航技术领域,尤其是涉及一种地基导航系统信号的快速捕获方法和系统。The invention relates to the field of navigation technology, and in particular to a method and system for quickly acquiring signals from a ground-based navigation system.
背景技术Background technique
作为卫星导航系统的重要补充,地基导航系统在某些方面有着独特的优势,可以克服卫星信号微弱、易受抗干、不能在室内使用等缺点。为了克服“远近效应”问题,地基导航系统在信号体制上采用了跳时/直序-码分多址信号(TH/DS-CDMA),通过划分时隙,不同伪卫星在不同时隙发射扩频信号,即时分的扩频通信体制,它既能克服“远近效应”,也能具有扩频信号的测距能力。As an important supplement to satellite navigation systems, ground-based navigation systems have unique advantages in some aspects and can overcome the disadvantages of weak satellite signals, susceptibility to interference, and inability to be used indoors. In order to overcome the "far and near effect" problem, the ground-based navigation system adopts time hopping/direct sequence code division multiple access signal (TH/DS-CDMA) in the signal system. By dividing the time slots, different pseudolites transmit spreaded signals in different time slots. Frequency signal, that is, a split-spectrum communication system, which can not only overcome the "far and near effect", but also have the ranging capability of spread spectrum signals.
TH/DS-CDMA不是一种连续播发的信号,系统中的伪卫星都有自己的信号发射时间窗口,只在特定的时隙发送导航信号,一般某个时隙只有一个伪卫星的发射窗口是打开的,多个伪卫星之间是分时播发信号的。即便是采取分时的方式,对于接收设备来说,与多个伪卫星之间的距离是不相等的,不同伪卫星之间的信号在接收端依然会有时间上的重叠。所以,在地基导航系统中每个伪卫星的发射窗口并不固定,而是一个已知的、具有随机特性的跳时序列,也就是跳时图案,避免两个伪卫星之间固定存在信号接收上的时间重叠。如在Locata系统中,一个跳时图案的超帧结构长200,每帧时间Tf内划分了10个时隙,每个时隙的持续时间Ts为0.1ms,每一颗伪卫星选择在每帧10个时隙中的某个时隙发射信号,而跳时图案的循环周期为200。TH/DS-CDMA is not a continuously broadcast signal. The pseudolites in the system have their own signal transmission time windows, and navigation signals are only sent in specific time slots. Generally, the emission window of only one pseudolite in a certain time slot is When turned on, multiple pseudolites broadcast signals in a time-sharing manner. Even if time-sharing is adopted, for the receiving equipment, the distance to multiple pseudolites is not equal, and the signals between different pseudolites will still overlap in time at the receiving end. Therefore, in the ground-based navigation system, the launch window of each pseudolite is not fixed, but a known, random time-hopping sequence, that is, a time-hopping pattern, to avoid fixed signal reception between two pseudolites. time overlap. For example, in the Locata system, the superframe structure of a time-hopping pattern is 200 long, and 10 time slots are divided into each frame time T f . The duration of each time slot T s is 0.1ms. Each pseudolite is selected in The signal is transmitted in one of the 10 time slots in each frame, and the time-hopping pattern has a cycle period of 200.
跳时信号体制的引入使得传统的扩频信号接收技术不再适用,而问题的难点主要集中在信号的捕获阶段,需要在信号非连续播发的条件下,在时域(码相位)和频域(多普勒)两个维度检测信号,常用的检测方法有串行搜索、并行搜索、FFT和匹配滤波,其捕获时间与资源占用成反比关系,一般而言,FFT和匹配滤波占用较多的软硬件资源,但是捕获时间可以大为缩短。The introduction of the time-hopping signal system makes the traditional spread spectrum signal receiving technology no longer applicable, and the difficulty of the problem is mainly concentrated in the signal acquisition stage, which requires discontinuous broadcasting of signals in the time domain (code phase) and frequency domain. (Doppler) two-dimensional detection signal. Commonly used detection methods include serial search, parallel search, FFT and matched filtering. The acquisition time is inversely proportional to resource usage. Generally speaking, FFT and matched filtering take up more time. Hardware and software resources, but capture time can be significantly reduced.
地基导航信号的捕获主要有两个关键问题:There are two key issues in capturing ground-based navigation signals:
(1)跳时图案的捕获(1) Capture of time-jumping patterns
地基导航信号的捕获不仅要在时域和频域检测信号,还要同时检测信号的多个发射时隙,与已知的跳时图案匹配,因此是时域、频域和发射时隙三个维度上的信号检测。基于传统的扩频信号捕获技术上来理解,当在某个时域和某个频域两维点上检测到信号,需要继续驻留多个时隙帧的时间来确认存在信号发射的时隙。The capture of ground-based navigation signals requires not only detecting signals in the time domain and frequency domain, but also detecting multiple transmission time slots of the signal at the same time to match the known time hopping pattern, so it is three times: time domain, frequency domain and transmission time slot. Signal detection in dimensions. Based on the understanding of traditional spread spectrum signal capture technology, when a signal is detected at a two-dimensional point in a certain time domain and a certain frequency domain, it needs to continue to reside for multiple time slot frames to confirm that there is a time slot for signal transmission.
(2)信号频率的捕获(2) Capture of signal frequency
由于地基导航系统采用了跳时信号体制,存在频率牵引带宽和捕获带宽不匹配的问题。Since the ground-based navigation system adopts a time-hopping signal system, there is a problem of mismatch between the frequency traction bandwidth and the acquisition bandwidth.
信号检测因频率未完全匹配而带来的功率损耗符合sinc2衰减:Ploss(Δf)=sinc2(πTΔf)。T是检测积分时间,Δf是频率偏差,典型的,当损耗约为3.9dB,这对于地基信号接收强度而言有很大概率能够检测到,但是在后续的信号频率牵引中,由于跳时发射的体制,相邻的发射时隙以帧时间Tf为平均间隔,对于利用相邻两个发射时隙积分值来计算频率误差的鉴频器而言,所能分辨的频率误差范围约为/>即频率牵引带宽与捕获带宽的不匹配,频率牵引带宽要远小于捕获带宽。为了实现频率牵引带宽和捕获带宽的匹配,在信号搜索时可以以/>为频率分辨率,但引起的信号功率损耗差异并不显著,且会增加捕获时间或者资源消耗。The power loss caused by signal detection due to incomplete frequency matching is consistent with sinc 2 attenuation: P loss (Δf) = sinc 2 (πTΔf). T is the detection integration time, Δf is the frequency deviation, typically, when The loss is about 3.9dB, which has a high probability of being detected based on the ground-based signal reception strength. However, in the subsequent signal frequency pulling, due to the time-hopping transmission system, the adjacent transmission time slots are based on the frame time T f Average interval, for a frequency discriminator that uses the integrated values of two adjacent transmit time slots to calculate the frequency error, the frequency error range that can be resolved is approximately/> That is, there is a mismatch between the frequency traction bandwidth and the capture bandwidth. The frequency traction bandwidth is much smaller than the capture bandwidth. In order to match the frequency traction bandwidth and acquisition bandwidth, you can use/> is the frequency resolution, but the difference in signal power loss caused is not significant, and will increase the capture time or resource consumption.
因此,地基导航信号的捕获要在时域、频域和跳时发射时隙展开三维度搜索,并且信号频率的捕获减小至范围内。Therefore, the capture of ground-based navigation signals requires a three-dimensional search in the time domain, frequency domain and time-hopping transmission time slots, and the capture of signal frequencies is reduced to within the range.
发明内容Contents of the invention
本发明所要解决的技术问题,在于提供一种地基导航信号的快速捕获方法和系统,以实现地基导航信号时域、频域和跳时图案的快速捕获,并且频率捕获的精度在范围内。The technical problem to be solved by the present invention is to provide a method and system for rapid acquisition of ground-based navigation signals to achieve rapid acquisition of time domain, frequency domain and time-hopping patterns of ground-based navigation signals, and the accuracy of frequency acquisition is within within the range.
为了解决上述技术问题,本发明首先提供了一种地基导航信号的快速捕获方法,包括以下步骤:In order to solve the above technical problems, the present invention first provides a method for quickly acquiring ground-based navigation signals, which includes the following steps:
步骤一,高于四倍码速率采样的地基导航数字信号经正交数字下变频、低通滤波和重量化处理,以两倍码速率重采样,获得重采样的I/Q基带信号;Step 1: The ground-based navigation digital signal sampled at a rate higher than four times the code rate is subjected to orthogonal digital down-conversion, low-pass filtering and weighting processing, and then resampled at twice the code rate to obtain a resampled I/Q baseband signal;
步骤二,基于重采样的I/Q基带信号,以0.5个码片为分辨率,使用两组匹配滤波在时域搜索地基伪卫星信号;其中,第一组匹配滤波深度L-1,输出测距码序列前个码片积分值,第二组匹配滤波深度L+1,输出测距码序列后/>个码片积分值,L是测距码序列周期长度,地基导航跳时信号一个发射时隙Ts播发一个完整周期长度的测距码;Step 2: Based on the resampled I/Q baseband signal, with a resolution of 0.5 chips, use two sets of matched filters to search for ground-based pseudolite signals in the time domain; among them, the first set of matched filters has a depth of L-1 and outputs measured before code sequence chip integral value, the second set of matching filter depth L+1, after outputting the ranging code sequence/> Chip integral value, L is the ranging code sequence period length, one transmission time slot T s of the ground-based navigation time-hopping signal broadcasts a ranging code with a complete period length;
步骤三,基于两组匹配滤波积分值计算Ts时间2L个采样点的功率值,当功率值大于设定门限Pth,以采样点连续计数值Kk为时间戳,将两组匹配滤波积分值Ik1/Qk1、Ik2/Qk2、功率值Pk记录到捕获信息列表;Step 3: Calculate the power value of 2L sampling points at time T s based on the two sets of matched filter integral values. When the power value is greater than the set threshold P th , use the continuous count value K k of the sampling points as the timestamp to integrate the two sets of matched filter points. The values I k1 /Q k1 , I k2 /Q k2 , and power value P k are recorded in the capture information list;
步骤四,根据捕获信息列表,基于时间戳计算捕获时隙值Tk构成跳时图案子样本,完成信号的跳时图案捕获;Step 4: According to the capture information list, the capture time slot value T k is calculated based on the timestamp to form a time-hopping pattern subsample, and the time-hopping pattern capture of the signal is completed;
步骤五,根据捕获信息列表,基于两组匹配滤波积分值计算信号频率估计 Step 5: According to the captured information list, calculate the signal frequency estimate based on two sets of matched filter integral values.
优选的,所述正交数字下变频处理以为频率间隔对信号进行频域搜索。Preferably, the orthogonal digital down-conversion process is based on Perform a frequency domain search of the signal for frequency intervals.
优选的,所述捕获信息列表在2L个采样间隔内只存储有最大功率值的一条捕获信息。Preferably, the acquisition information list stores only one piece of acquisition information with the maximum power value within 2L sampling intervals.
优选的,所述匹配滤波搜索,在连续的两帧时间2Tf内未检测到信号,则退出当前目标伪卫星的搜索或者清空捕获信息列表重新启动搜索,其中Tf是地基导航信号跳时发射的帧时间,包含N个发射时隙Ts。Preferably, in the matched filter search, if no signal is detected within two consecutive frames of time 2T f , the search for the current target pseudolite will be exited or the capture information list will be cleared to restart the search, where T f is the time-hopping emission of the ground-based navigation signal. The frame time includes N transmission time slots T s .
优选的,所述捕获时隙值Tk相对于第一条记录时间戳K1计算:Preferably, the capture time slot value T k is calculated relative to the first recording timestamp K 1 :
优选的,所述信号频率估计采取的计算方法:Preferably, the signal frequency is estimated to be Calculation method adopted:
其中,m是捕获信息列表的记录条数。Among them, m is the number of records in the captured information list.
优选的,所述信号频率估计是在完成跳时图案捕获删除虚警捕获信息记录后计算。Preferably, the signal frequency is estimated to be It is calculated after completing the time jump pattern capture and deleting the false alarm capture information record.
为了解决上述技术问题,本发明还提供了一种地基导航信号的快速捕获系统,包括:In order to solve the above technical problems, the present invention also provides a rapid acquisition system for ground-based navigation signals, including:
载波数控振荡器,产生本地参考载波信号;Carrier CNC oscillator generates local reference carrier signal;
数字下变频器,与所述载波数控振荡器相连,将输入的中频采样信号正交下变频至零中频,输出I/Q基带信号;A digital downconverter, connected to the carrier digitally controlled oscillator, orthogonally downconverts the input intermediate frequency sampling signal to zero intermediate frequency, and outputs an I/Q baseband signal;
低通滤波及重量化模块,与所述数字下变频器相连,根据码速率对信号低通滤波,并重量化为2比特的I/Q信号;A low-pass filtering and reweighting module is connected to the digital downconverter, low-pass filters the signal according to the code rate, and reweights it into a 2-bit I/Q signal;
采样数控振荡器,产生重采样的时钟信号;Sampling a digitally controlled oscillator to generate a resampled clock signal;
采样点连续计数器,与所述采样数控振荡器相连,对重采样后的采样点连续计数;A sampling point continuous counter, connected to the sampling numerical control oscillator, to continuously count the sampling points after resampling;
抽取器,与所述低通滤波及重量化模块、采样数控振荡器相连,对低通滤波及重量化模块输出的信号重采样,获得两倍码速率的重采样I/Q信号;An extractor, connected to the low-pass filtering and reweighting module and the sampling CNC oscillator, resamples the signal output by the low-pass filtering and reweighting module to obtain a resampled I/Q signal with twice the code rate;
匹配搜索器,与所述抽取器、采样数控振荡器、采样点连续计数器相连,使用匹配滤波器对信号进行搜索;A matching searcher, connected to the decimator, a sampling numerically controlled oscillator, and a sampling point continuous counter, and uses a matching filter to search for signals;
跳时图案捕获和频率估计模块,与所述匹配搜索器相连,基于匹配搜索结果进行跳时图案的捕获和信号频率估计;A time-hopping pattern capture and frequency estimation module, connected to the matching searcher, performs time-hopping pattern capture and signal frequency estimation based on the matching search results;
所述匹配搜索器包含两组匹配滤波器:第一组匹配滤波器,输出测距码序列前个码片L-1个采样点的I/Q积分值;第二组匹配滤波器,输出测距码序列后/>个码片L+1个采样点的I/Q积分值;The matching searcher includes two sets of matching filters: the first set of matching filters, before outputting the ranging code sequence The I/Q integral value of L-1 sampling points for each chip; the second set of matched filters, after outputting the ranging code sequence/> The I/Q integral value of L+1 sampling points for each chip;
所述匹配搜索器还包含一个峰值记录器,与所述第一组匹配滤波器、第二组匹配滤波器、采样点连续计数器相连,计算功率值与预设的门限比较,若大于门限,记录一条信息:第一组匹配滤波器输出的I/Q积分值Lk1/Qk1、第二组匹配滤波输出的I/Q积分值Ik2/Qk2、功率值和采样点连续计数值Kk。The matching searcher also includes a peak recorder, which is connected to the first set of matched filters, the second set of matched filters, and a sampling point continuous counter. The calculated power value is compared with a preset threshold. If it is greater than the threshold, it is recorded. A piece of information: the I/Q integral value L k1 /Q k1 output by the first set of matched filters, the I/Q integral value I k2 /Q k2 output by the second set of matched filters, the power value and the sampling point continuous count value K k .
优选的,所述峰值记录器在2L个采样点内只记录具有最大功率值的一条信息。Preferably, the peak recorder records only one piece of information with the maximum power value within 2L sampling points.
优选的,所述跳时图案捕获和频率估计模块,根据峰值记录器记录的采样点连续计数值Kk计算捕获时隙值Tk:构成跳时图案的子样本,进行跳时图案捕获,根据峰值记录器记录的第一组、第二组匹配滤波器输出的I/Q积分值计算频率估计/> Preferably, the time-hopping pattern capture and frequency estimation module calculates the capture time slot value T k according to the continuous count value K k of sampling points recorded by the peak recorder: The subsamples that constitute the time-hopping pattern are captured, and the frequency estimate is calculated based on the I/Q integral values of the first and second sets of matched filter outputs recorded by the peak recorder/>
其中,m是峰值记录器中的记录条数。Among them, m is the number of records in the peak recorder.
本发明实现的地基导航信号快速捕获方法和系统的主要优点:The main advantages of the ground-based navigation signal rapid acquisition method and system implemented by the present invention are:
(1)通过匹配滤波实现地基导航信号时域、频域和发射时隙的三维度快速搜索,在5~10个子帧时间内,就可以捕获到信号;(1) Realize three-dimensional rapid search of ground-based navigation signals in time domain, frequency domain and transmission time slot through matching filtering, and the signal can be captured within 5 to 10 subframes;
(2)通过分组匹配滤波实现在大范围内信号频率的精确估计;(2) Through group matching filtering, the Accurate estimation of signal frequency over a wide range;
(3)频域搜索以为间隔,大幅度减少了高动态应用中多普勒频点的搜索个数,缩短了捕获时间;(3) Frequency domain search based on as the interval, which greatly reduces the number of Doppler frequency point searches in high-dynamic applications and shortens the acquisition time;
(4)通过测距码序列码相位完整检测,能有效抑制自相关函数的旁瓣干扰,准确捕获主峰。(4) Through the complete detection of the ranging code sequence code phase, the side lobe interference of the autocorrelation function can be effectively suppressed and the main peak can be accurately captured.
附图说明Description of the drawings
附图用于提供对本发明的进一步理解,并且构成本申请的一部分,与本发明实施例一起用于解释本发明,并不构成对本发明的不当限定。在附图中:The drawings are used to provide a further understanding of the present invention and constitute a part of the present application. They are used to explain the present invention together with the embodiments of the present invention and do not constitute an improper limitation of the present invention. In the attached picture:
图1为地基导航信号跳时发射的示意图;Figure 1 is a schematic diagram of time-hopping transmission of ground-based navigation signals;
图2为本发明地基导航信号快速捕获方法实施例的流程图;Figure 2 is a flow chart of an embodiment of a ground-based navigation signal rapid acquisition method according to the present invention;
图3为本发明地基导航信号快速捕获系统实施例的组成示意图;Figure 3 is a schematic diagram of the composition of an embodiment of the ground-based navigation signal rapid acquisition system of the present invention;
图4为本发明实施例中匹配搜索器的组成示意图。Figure 4 is a schematic diagram of the composition of a matching searcher in an embodiment of the present invention.
具体实施方式Detailed ways
为了使本发明的目的、技术方案及优点更加清楚明白,以下结合实施例,对本发明进行进一步详细说明。应当理解,此处所描述的具体实施例仅仅用以解释本发明,并不用于限定本发明。In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with examples. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.
在地基导航系统中,一个跳时图案使用超帧、子帧和时隙来描述。如图1所示,跳时图案的一个周期称为超帧,一个超帧包含了M个子帧,每个子帧中划分了N个时隙,每个时隙时间为Ts,一般与测距码周期相同,一个子帧的时间Tf即为N·Ts。具体应用中,地基伪卫星部署数量的上限取决于N,即在一个子帧内,每一个时隙只允许一个伪卫星发射信号,且伪卫星在子帧内的发射时隙并不固定。In ground-based navigation systems, a time-hopping pattern is described using superframes, subframes, and time slots. As shown in Figure 1, a period of the time hopping pattern is called a superframe. A superframe contains M subframes. Each subframe is divided into N time slots. The time of each time slot is T s. Generally, it is related to ranging. The code period is the same, and the time T f of one subframe is N·T s . In specific applications, the upper limit of the number of ground-based pseudolites deployed depends on N, that is, within a subframe, only one pseudolite is allowed to transmit signals in each time slot, and the pseudolite's transmission time slot within a subframe is not fixed.
实施例1Example 1
图2为本发明地基导航信号快速捕获方法实施例的流程示意图。图2所示的方法实施例主要包括如下步骤:Figure 2 is a schematic flow chart of an embodiment of a ground-based navigation signal rapid acquisition method according to the present invention. The method embodiment shown in Figure 2 mainly includes the following steps:
步骤S101,高于四倍码速率采样的地基导航数字信号经正交数字下变频、低通滤波和重量化处理,以两倍码速率重采样,获得重采样的I/Q基带信号;Step S101, the ground-based navigation digital signal sampled at a rate higher than four times the code rate is subjected to orthogonal digital down-conversion, low-pass filtering and weighting processing, and is resampled at twice the code rate to obtain a resampled I/Q baseband signal;
步骤S102,基于重采样的I/Q基带信号,以0.5个码片为分辨率,使用两组匹配滤波在时域搜索地基伪卫星信号;其中,第一组匹配滤波深度L-1,输出测距码序列前个码片积分值,第二组匹配滤波深度L+1,输出测距码序列后/>个码片积分值,L是测距码序列周期长度,地基导航跳时信号一个发射时隙Ts播发一个完整周期长度的测距码;Step S102, based on the resampled I/Q baseband signal, with a resolution of 0.5 chips, use two sets of matched filters to search for ground-based pseudolite signals in the time domain; among them, the first set of matched filters has a depth of L-1 and outputs measured before code sequence chip integral value, the second set of matching filter depth L+1, after outputting the ranging code sequence/> Chip integral value, L is the ranging code sequence period length, one transmission time slot T s of the ground-based navigation time-hopping signal broadcasts a ranging code with a complete period length;
步骤S103,基于两组匹配滤波积分值计算Ts时间2L个采样点的功率值,当功率值大于设定门限Pth,以采样点连续计数值Kk为时间戳,将两组匹配滤波积分值Ik1/Qk1、Ik2/Qk2、功率值Pk记录到捕获信息列表;Step S103, calculate the power values of 2L sampling points at time T s based on two sets of matched filter integral values. When the power value is greater than the set threshold P th , use the continuous count value K k of sampling points as the timestamp, and combine the two sets of matched filter integrals. The values I k1 /Q k1 , I k2 /Q k2 , and power value P k are recorded in the capture information list;
步骤S104,根据捕获信息列表,基于时间戳计算捕获时隙值Tk构成跳时图案子样本,完成信号的跳时图案捕获;Step S104, according to the capture information list, calculate the capture time slot value T k based on the timestamp to form a time hopping pattern subsample, completing the time hopping pattern capture of the signal;
步骤S105,根据捕获信息列表,基于两组匹配滤波积分值计算信号频率估计 Step S105, according to the captured information list, calculate the signal frequency estimate based on two sets of matched filter integral values.
其中,步骤S101的正交数字下变频处理,为适应不同的载体应用场景,对于静态或者低动态应用,以数字信号的标称中频进行混频,在高动态应用中,正交数字下变频处理还要以为频率间隔对信号进行频域搜索;原始地基导航数字信号的采样率需高于四倍码速率,便于低通滤波截止频率指标的设计和产生两倍码速率的重采样时钟信号。Among them, the orthogonal digital down-conversion process in step S101 is to adapt to different carrier application scenarios. For static or low-dynamic applications, the nominal intermediate frequency of the digital signal is used for mixing. In high-dynamic applications, orthogonal digital down-conversion process Also with Perform a frequency domain search on the signal for the frequency interval; the sampling rate of the original ground-based navigation digital signal needs to be higher than four times the code rate, which facilitates the design of the low-pass filter cutoff frequency indicator and the generation of a resampled clock signal with twice the code rate.
其中,步骤S102的第一组、第二组匹配滤波的深度可以互换,测距码为伪随机序列,L为奇数,两组匹配滤波的积分长度几近相等。次优的,两组深度都是L。Among them, the depths of the first group and the second group of matched filters in step S102 can be interchanged, the ranging code is a pseudo-random sequence, L is an odd number, and the integral lengths of the two groups of matched filters are almost equal. Suboptimal, both sets of depths are L.
其中,步骤S103基于两组匹配滤波积分值计算Ts时间2L个采样点的功率值,是根据第一组、第二组匹配滤波I/Q积分值的和来计算。Among them, step S103 calculates the power value of 2L sampling points in T s time based on two sets of matched filter integral values, which is calculated based on the sum of the first set and the second set of matched filter I/Q integral values.
其中,为进一步提高对自相关函数旁瓣干扰的抑制,步骤S103中可约束捕获信息列表在2L个采样间隔内只存储有最大功率值的一条捕获信息,根据自相关函数峰值的唯一性,在2L个采样间隔内检测到更高功率值时,则替换已有记录。Among them, in order to further improve the suppression of autocorrelation function side lobe interference, in step S103, the acquisition information list can be constrained to only store one piece of acquisition information with the maximum power value within 2L sampling intervals. According to the uniqueness of the autocorrelation function peak, in When a higher power value is detected within 2L sampling intervals, the existing record is replaced.
其中,为进一步提高信号搜索的效率,步骤S102、S103的匹配滤波搜索在连续的两帧时间2Tf内未检测到信号,则退出当前目标伪卫星的搜索或者清空捕获信息列表重新启动搜索,在高动态应用中,可更换搜索频点后再启动匹配滤波搜索。Among them, in order to further improve the efficiency of signal search, if no signal is detected in the matched filter search of steps S102 and S103 within two consecutive frames of time 2T f , the search for the current target pseudolite will be exited or the capture information list will be cleared and the search will be restarted. In highly dynamic applications, you can change the search frequency point and then start the matching filter search.
其中,步骤S104,捕获时隙值相对于第一条记录时间戳K1计算,捕获信息列表的第一个记录标记为时隙0,计算后续记录采样点计数值的增量,根据每个时隙有2L个采样点,折算到时隙值:Among them, in step S104, the capture time slot value is calculated relative to the first record timestamp K 1. The first record in the capture information list is marked as time slot 0. The increment of the subsequent record sampling point count value is calculated. According to each time There are 2L sampling points in the slot, converted to the time slot value:
其中,步骤S105中的信号频率估计基于每一条捕获记录独立计算频率偏差/>后再求均值:Among them, the signal frequency estimation in step S105 Frequency deviation is calculated independently based on each captured record/> Then find the mean:
m是捕获信息列表的记录条数。由于两组匹配滤波的积分时间近似为因此,上述信号频率估计的可检测范围为/>基于地基导航的信号接收功率相对较强以及求平均处理,/>的估计精度在/>范围内。m is the number of records in the captured information list. Since the integration time of the two sets of matched filters is approximately Therefore, the detectable range of the above signal frequency estimate is/> The signal reception power based on ground-based navigation is relatively strong and the averaging process,/> The estimation accuracy is/> within the range.
另外,为进一步提高信号频率估计的精度,信号频率估计可以在完成跳时图案捕获且删除虚警捕获信息记录后计算。In addition, in order to further improve the accuracy of signal frequency estimation, signal frequency estimation It can be calculated after the time jump pattern capture is completed and the false alarm capture information record is deleted.
实施例2Example 2
图3为本发明地基导航信号快速捕获系统实施例的组成示意图。如图3所示,实施例包括:载波数控振荡器120、数字下变频器130、低通滤波及重量化模块(170、180)、采样数控振荡器140、采样点连续计数器150、抽取器(190、200)、匹配搜索器210、跳时图案捕获和频率估计模块220。Figure 3 is a schematic diagram of the composition of an embodiment of the ground-based navigation signal rapid acquisition system of the present invention. As shown in Figure 3, the embodiment includes: a carrier numerically controlled oscillator 120, a digital downconverter 130, a low-pass filtering and weighting module (170, 180), a sampling numerically controlled oscillator 140, a sampling point continuous counter 150, a decimator ( 190, 200), match searcher 210, time-hopping pattern capture and frequency estimation module 220.
载波数控振荡器120产生本地参考载波信号205,参考载波信号205一般是一个3~5比特的信号。数字下变频器130将输入地基导航数字信号205与本地参考载波信号205正交混频,输出多比特的I/Q基带信号211、212。The carrier numerically controlled oscillator 120 generates a local reference carrier signal 205. The reference carrier signal 205 is generally a 3-5 bit signal. The digital downconverter 130 orthogonally mixes the input ground-based navigation digital signal 205 and the local reference carrier signal 205, and outputs multi-bit I/Q baseband signals 211 and 212.
I/Q基带信号211、212经过低通滤波和重量化模块170、180,得到2~4比特的重量化I/Q基带信号213、214。为兼顾量化损失和资源消耗,优选的,I/Q基带信号213、214可以为2比特。The I/Q baseband signals 211 and 212 pass through the low-pass filtering and reweighting modules 170 and 180 to obtain 2 to 4-bit reweighted I/Q baseband signals 213 and 214. In order to take into account quantization loss and resource consumption, preferably, the I/Q baseband signals 213 and 214 can be 2 bits.
采样数控振荡器140产生两倍码速率重采样时钟信号218。在静态或低动态应用中,可以以标称的码速率来计算所需重采样时钟信号218的频率,而在高动态应用中,应考虑多普勒效应引起的实际码速率的微小变化。采样点连续计数器150以采样时钟信号218为基准,进行连续计数,输出连续计数值217,作为捕获过程的时间戳。The sampling digitally controlled oscillator 140 generates a twice code rate resampled clock signal 218. In static or low dynamic applications, the frequency of the required resampled clock signal 218 can be calculated at the nominal code rate, while in high dynamic applications, small changes in the actual code rate due to the Doppler effect should be taken into account. The sampling point continuous counter 150 performs continuous counting based on the sampling clock signal 218, and outputs a continuous count value 217 as a timestamp of the capture process.
重量化的I/Q基带信号213、214,进入抽取器190、200,以重采样时钟信号218进行抽取,获得重采样的I/Q基带信号215、216,并进入匹配搜索器210。The weighted I/Q baseband signals 213 and 214 enter the extractors 190 and 200 and are extracted with the resampled clock signal 218 to obtain the resampled I/Q baseband signals 215 and 216, and enter the matching searcher 210.
匹配搜索器210的搜索结果219,作为跳时图案捕获和频率估计模块220的输入,进行跳时图案的捕获和信号频率的估计。The search results 219 of the matching searcher 210 are used as inputs to the time-hopping pattern capture and frequency estimation module 220 to capture the time-hopping pattern and estimate the signal frequency.
图4是实施例匹配搜索器的组成示意图。如图4所示,包括:延迟寄存器(310、320)、加法器(330、340)、2分频器400、3比特2L级移位寄存器(350、360)、选择器(370、380)、1比特L级移位寄存器390、第一组匹配滤波器(410、430)、第二组匹配滤波器(420、440)、峰值记录器450。Figure 4 is a schematic diagram of the composition of the matching searcher according to the embodiment. As shown in Figure 4, it includes: delay register (310, 320), adder (330, 340), 2-divider 400, 3-bit 2L level shift register (350, 360), selector (370, 380) , 1-bit L-stage shift register 390, a first set of matched filters (410, 430), a second set of matched filters (420, 440), and a peak recorder 450.
重采样的I/Q基带信号215、216进入延迟寄存器310、320,得到延迟信号301、302,与未延迟的信号215、216进入加法器330、340,得到相邻采样点两两之和的信号311、312,若输入的重采样I/Q基带信号215、216为2比特,则信号311、312为3比特。The resampled I/Q baseband signals 215 and 216 enter the delay registers 310 and 320 to obtain delayed signals 301 and 302, and enter the adders 330 and 340 with the undelayed signals 215 and 216 to obtain the sum of the two adjacent sampling points. Signals 311 and 312, if the input resampled I/Q baseband signals 215 and 216 are 2 bits, then the signals 311 and 312 are 3 bits.
采样点两两之和311、312进入3比特2L级移位寄存器350、360,分为长度L的奇数延迟数据组313、315和偶数延迟数据组314、316输出,并进入选择器370、380。The sums 311 and 312 of the two sampling points enter the 3-bit 2L stage shift registers 350 and 360, and are divided into odd delay data groups 313 and 315 of length L and even delay data groups 314 and 316 for output, and enter the selectors 370 and 380. .
重采样时钟信号218经2分频器400,输出频率为码速率占空比为50%的选择信号355,在选择信号355的控制下,选择器370、380选择奇数延迟数据组313、315或者偶数延迟数据组314、316作为输出317、318,并将317、318的前个数据321、323送入第一组匹配滤波器410、430,后/>个数据322、324送入第二组匹配滤波器420、440。The resampled clock signal 218 passes through the 2-divider 400 and outputs a selection signal 355 whose frequency is a code rate and a duty cycle of 50%. Under the control of the selection signal 355, the selectors 370 and 380 select odd delay data groups 313, 315 or The even delay data groups 314 and 316 are used as outputs 317 and 318, and the preceding ones of 317 and 318 are The data 321 and 323 are sent to the first set of matched filters 410 and 430, and then/> The data 322 and 324 are sent to the second set of matched filters 420 and 440.
1比特L级移位寄存器390存放测距码序列的L个码片,序列的前个码片351送入第一组匹配滤波器410、430,后/>个码片352送入第二组匹配滤波器420、440。The 1-bit L-level shift register 390 stores L chips of the ranging code sequence. The first part of the sequence Each chip 351 is sent to the first set of matched filters 410 and 430, and then/> Each chip 352 is fed into the second set of matched filters 420, 440.
第一组、第二组匹配滤波器分别产生的积分值361(Ik1)、363(Qk1)和362(Ik2)、364(Qk2),输入到峰值记录器450。峰值记录器450将先计算两组滤波器积分值的和,再计算功率值,与预设的门限比较,若大于门限,记录以下信息:第一组匹配滤波器410、430输出的I/Q积分值361、363(Ik1、Qk1)、第二组匹配滤波器420、440输出的I/Q积分值362、364(Ik2、Qk2)、功率值和采样点连续计数值Kk。峰值记录器450在2L个采样点内只记录具有最大功率值的一条信息。The integrated values 361(I k1 ), 363(Q k1 ) and 362(I k2 ), 364(Q k2 ) respectively generated by the first group and the second group of matched filters are input to the peak recorder 450 . The peak recorder 450 will first calculate the sum of the integral values of the two sets of filters, then calculate the power value, and compare it with the preset threshold. If it is greater than the threshold, record the following information: I/Q output by the first set of matched filters 410 and 430 Integral values 361, 363 (I k1 , Q k1 ), I/Q integral values 362, 364 (I k2 , Q k2 ) output by the second set of matched filters 420, 440, power value and sampling point continuous count value K k . The peak recorder 450 only records one piece of information with the maximum power value within 2L sampling points.
跳时图案捕获和频率估计模块220,根据峰值记录器450记录的采样点连续计数值Kk计算捕获时隙值Tk:构成跳时图案的子样本,进行跳时图案捕获;根据峰值记录器450记录的第一组匹配滤波器、第二组匹配滤波输出的I/Q积分值计算频率估计/> The time-hopping pattern capture and frequency estimation module 220 calculates the capture time slot value T k according to the continuous count value K k of sampling points recorded by the peak recorder 450: Sub-samples that constitute the time-hopping pattern are captured to capture the time-hopping pattern; frequency estimation is calculated based on the I/Q integral values of the first set of matched filters and the second set of matched filter outputs recorded by the peak recorder 450/>
其中,m是峰值记录器中的记录条数。Among them, m is the number of records in the peak recorder.
本发明基于匹配滤波技术,实现了地基导航信号时域、频域和发射时隙的三维度快速搜索。以Locata系统设计参数为例:本发明可以在5~10ms内捕获目标伪卫星信号,50~100ms内搜索、捕获系统内所有的伪卫星;对信号频率的估计范围达到-10~+10kHz,对于静态或低动态应用而言,不需要额外的多普勒频点搜索;频域搜索间隔为10kHz,在高动态应用中,当视距速度达到5km/s时,对应的多普勒频移范围-40~40kHz,搜索频点数为9个,最坏情况也能在21~26ms内捕获到目标伪卫星。Based on the matching filtering technology, the present invention realizes three-dimensional fast search of time domain, frequency domain and transmission time slot of ground-based navigation signals. Taking the design parameters of the Locata system as an example: the present invention can capture the target pseudolite signal within 5 to 10 ms, and search and capture all pseudolites in the system within 50 to 100 ms; the estimated signal frequency range reaches -10 to +10 kHz. For static or low dynamic applications, no additional Doppler frequency point search is required; the frequency domain search interval is 10kHz. In high dynamic applications, when the line-of-sight speed reaches 5km/s, the corresponding Doppler frequency shift range -40~40kHz, the number of search frequency points is 9, and the target pseudolite can be captured within 21~26ms in the worst case.
最后说明的是,以上实施例仅用以说明本发明的技术方案而非限制,尽管参照较佳实施例对本发明进行了详细说明,本领域的普通技术人员应当理解,可以对本发明的技术方案进行修改或者等同替换,而不脱离本发明技术方案的宗旨和范围,其均应涵盖在本发明的权利要求范围当中。Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified. Modifications or equivalent substitutions without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of the claims of the present invention.
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