WO2022033071A1 - 一种基于最速上升法的高动态卫星跟踪方法 - Google Patents

一种基于最速上升法的高动态卫星跟踪方法 Download PDF

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WO2022033071A1
WO2022033071A1 PCT/CN2021/089030 CN2021089030W WO2022033071A1 WO 2022033071 A1 WO2022033071 A1 WO 2022033071A1 CN 2021089030 W CN2021089030 W CN 2021089030W WO 2022033071 A1 WO2022033071 A1 WO 2022033071A1
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signal
mixing
carrier
mixing signal
fast fourier
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French (fr)
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曾庆化
邱文旗
刘建业
孙永荣
许睿
李荣冰
熊智
赖际舟
王融
赵伟
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南京航空航天大学
南京航空航天大学秦淮创新研究院
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S19/13—Receivers
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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  • the invention belongs to the field of satellite signal processing, and particularly relates to a high dynamic satellite tracking method based on the steepest ascent method.
  • GNSS is a key component of the navigation system.
  • the carrier tracking loop of the GNSS receiver is easy to lose lock. Increasing the bandwidth of the tracking loop will make the tracking loop have better dynamic performance, but at the same time introduce a larger tracking error.
  • the methods for improving the tracking performance of the wave tracking loop in high dynamic environments can be divided into two categories: one is to use inertial navigation system assistance, and the other is to improve its own structure.
  • inertial navigation system improves the dynamic performance of receiver by feeding back the Doppler frequency shift value predicted by GNSS/INS ultra-tightly coupled system into the carrier tracking loop.
  • This method has the advantages of high accuracy and fast response, but it requires precise synchronization of the carrier tracking loop with the external equipment, which may bring more costs and difficulties to the implementation.
  • the discriminator-based method still follows the traditional phase-locked loop structure, which alleviates the contradiction between high dynamics and high precision of this structure with the assistance of frequency-locked loop or Wigner-Ville distribution (WVD), but this method Requires a very complex mechanism design; estimator-based approaches replace the PLL's discriminator and loop filter with an estimator whose structure can take any suitable form, such as Kalman filter (KF), extended Kalman filter Mann Filter (EKF), Unscented Kalman Filter (UKF), Maximum Likelihood, and FFT-based methods that require prior knowledge of noise statistics to get a better carrier estimate; vector-based methods use a navigation filter Instead of a single tracking loop in each channel, the feedback from the local signal generator to each satellite is obtained based on the calculated pseudorange and pseudorange rate when the receiver position and velocity are known.
  • KF Kalman filter
  • EKF extended Kalman filter Mann Filter
  • UDF Unscented Kalman Filter
  • FFT-based methods that require prior knowledge of noise statistics to get a better
  • the present invention provides a high dynamic satellite tracking method based on the steepest ascent method which is not affected by high dynamic.
  • the technical solution of the present invention is: a high dynamic satellite tracking method based on the steepest ascent method, comprising:
  • Step 1 According to the autocorrelation characteristics of the ranging code sequence, perform a correlation operation between the locally generated ranging code sequence C l (n) and the intermediate frequency signal x (n) input to the tracking loop to obtain the intermediate frequency signal after code stripping. s(n);
  • Step 2 Mix the stripped intermediate frequency signal s(n) with the locally generated instant carrier signal x P (n) to obtain a first mixing signal y P (n), and mix the stripped intermediate frequency signal s (n) mixing with the leading carrier signal x E (n) or the lagging carrier signal x L (n) to obtain the second mixing signal y L (n) or the third mixing signal y E (n);
  • Step 3 Perform down-sampling processing on the first mixing signal y P (n) to obtain a fourth mixing signal y P (k), and perform downsampling on the second mixing signal y L (n) or the third mixing signal y L (n).
  • the mixing signal y E (n) is subjected to down-sampling processing to obtain the fifth mixing signal y L (k) or the sixth mixing signal y E (k);
  • Step 4 Perform fast Fourier transform processing on the fourth mixing signal y P (k) and the fifth mixing signal y L (k) to obtain the maximum value of the output amplitude spectrum of the fast Fourier transform, or Do fast Fourier transform processing to the fourth mixing signal y P (k) and the sixth mixing signal y E (k) to obtain the maximum value of the fast Fourier transform output amplitude spectrum;
  • Step 5 Use the steepest ascent method and the maximum value of the output amplitude spectrum of the fast Fourier transform to track the carrier.
  • the signal structure of the discrete intermediate frequency input to the tracking loop is shown in formula (1).
  • A is the amplitude of the intermediate frequency signal x(n)
  • C(n) is the ranging code sequence
  • D(n) is the information code sequence
  • f 1 is the frequency of the signal arriving in the tracking loop
  • ⁇ 0 is the initial phase
  • R( ) is the autocorrelation function of the ranging code
  • C l (n) is the locally generated ranging code sequence.
  • the above-mentioned step 2 further includes: if the fastest ascent is to use the left partial derivative, then the choice is to separate the stripped intermediate frequency signal s(n) with the locally generated instant carrier signal x P (n) and the delayed carrier respectively.
  • the signal x L (n) is mixed, and after the mixing, the first mixing signal y P (n) and the second mixing signal y L (n) of the signal are obtained respectively;
  • the option is to mix the stripped intermediate frequency signal s(n) with the locally generated instant carrier signal x P (n) and the leading carrier signal x E (n), respectively. After frequency, the first mixing signal y P (n) and the third mixing signal y E (n) are obtained respectively.
  • the signal structure of the instant carrier generated locally is defined as:
  • the locally generated signal structure of the lead carrier is defined as:
  • the locally generated signal structure of the lag carrier is defined as:
  • f2 is the instantaneous carrier signal frequency and d is the frequency interval.
  • the option is to separate the stripped intermediate frequency signal s(n) with the locally generated instant carrier signal x P (n) and the delayed carrier signal x L respectively.
  • (n) mixing, after the mixing, the first mixing signal y P (n) and the second mixing signal y L (n) of the signal are obtained respectively, further comprising:
  • the mixing process is as follows:
  • step 3 the down-sampling process of the first mixing signal y P (n) can be expressed by formula (7):
  • T s is the initial sampling period
  • M is the number of summation operation points.
  • step 4 further:
  • the fourth mixing signal y P (k) can be used to represent the signal after the continuous function has undergone two processing processes of discrete and truncation, as represented by formula (9)
  • TL represents the length of the rectangular window
  • rect( ⁇ ) represents the rectangular function
  • ⁇ ( ⁇ ) is the Dirac function
  • M FFT_P ( ⁇ f) is the maximum value of the output amplitude spectrum of the fast Fourier transform
  • sinc( ⁇ ) is the sinc function
  • step 5 further:
  • the carrier tracking process can be expressed by formula (11)
  • ⁇ f k+1 is the frequency difference between the received signal and the local instant carrier at the next moment
  • ⁇ f k is the frequency difference between the received signal and the local instant carrier at the current moment
  • ⁇ is the control step size
  • k is Immediate performance function value at the current moment
  • k is the lag performance function value at the current moment.
  • the beneficial effect of an embodiment of the present invention relative to the prior art is that: in this embodiment, a performance function that is not affected by high dynamics is constructed, and a high dynamic tracking structure is constructed by using the function and the steepest ascent method, and the satellite signal is processed by this structure.
  • the tracking method is simple in design, does not need external sensor assistance, and does not need to know the prior statistical information of noise in advance, and has good robustness and stability.
  • FIG. 2 is an overall flow structure diagram of an embodiment of the present invention.
  • This embodiment provides a high dynamic satellite tracking method based on the steepest ascent method, as shown in FIG. 1 and FIG. 2 , including the following steps:
  • the function of this step is to strip the ranging code sequence, which is as follows:
  • i is the imaginary part symbol
  • A is the amplitude of the signal x(n)
  • C(n) is the ranging code sequence
  • D(n) is the information code sequence
  • f1 is the frequency of the signal arriving in the tracking loop
  • ⁇ 0 is initial phase.
  • R( ) is the autocorrelation function of the ranging code
  • C l (n) is the locally generated ranging code sequence.
  • S20 Mix the stripped intermediate frequency signal s(n) with the locally generated real-time carrier signal xP( n ) to obtain a first mixed frequency signal yP( n ), and mix the stripped intermediate frequency signal s(n). n) Mixing with the leading carrier signal x E (n) or the lagging carrier signal x L (n) to obtain the second mixing signal y L (n) or the third mixing signal y E (n).
  • the choice is to mix the intermediate frequency signal s(n) with the locally generated instant carrier signal x P (n) and the delayed carrier signal x L (n), respectively.
  • the first mixing signal y P (n) and the second mixing signal y L (n) are obtained respectively;
  • the choice is to combine the intermediate frequency signal s(n) with the locally generated instant carrier
  • the signal x P (n) is mixed with the leading carrier signal x E (n), and after the mixing, the first mixed signal y P (n) and the third mixed signal y E (n) are obtained respectively.
  • the structure of the locally generated carrier signal needs to be defined, and the signal structure of the locally generated instant carrier signal is defined as:
  • the signal structure of the locally generated lead carrier is defined as:
  • the signal structure of the locally generated lagging carrier is defined as:
  • f2 is the instantaneous carrier signal frequency and d is the frequency interval.
  • the summation method is used for downsampling.
  • the first The mixing signal y P (n) and the second mixing signal y L (n) become the fourth mixing signal y P (k) and the fifth mixing signal y L (k), respectively, or the first mixing signal y P (n) and the third mixing signal y E (n) become the fourth mixing signal y P (k) and the sixth mixing signal y E (k), respectively.
  • the purpose of downsampling is to reduce the amount of calculation in the subsequent Fast Fourier Transform (hereinafter referred to as FFT) process. Since the sampling rate fs is much larger than the frequency difference ⁇ f between the received signal and the local instant carrier, the first mixing signal y
  • the downsampling process of P (n) can be expressed by formula (7).
  • the down-sampling process of the second mixing signal y L (n) can be represented by formula (8).
  • T s is the initial sampling period
  • M is the number of summation operation points.
  • S40 Perform fast Fourier transform processing on the fourth mixing signal y P (k) and the fifth mixing signal y L (k) to obtain the maximum value of the output amplitude spectrum of the fast Fourier transform or
  • the fourth frequency mixing signal y P (k) and the sixth frequency mixing signal y E (k) are subjected to fast Fourier transform processing to obtain the maximum value of the output amplitude spectrum of the fast Fourier transform.
  • the specific fourth mixing signal y P (k) is used to represent the signal of the continuous function after the two processing processes of discrete and truncation, which can be expressed by formula (9)
  • TL represents the length of the rectangular window
  • rect( ⁇ ) represents the rectangular function
  • ⁇ ( ⁇ ) is the Dirac function
  • M FFT_P ( ⁇ f) is the maximum value of the output amplitude spectrum of the fast Fourier transform
  • sinc( ⁇ ) is the sinc function
  • Equation (10) can be abbreviated as
  • N c is the maximum value of M FFT_P in a short time.
  • the carrier tracking process can be expressed by formula (15).
  • ⁇ f k+1 is the frequency difference between the received signal and the local instant carrier at the next moment
  • ⁇ f k is the frequency difference between the received signal and the local instant carrier at the current moment
  • ⁇ is the control step size
  • k is Immediate performance function value at the current moment
  • k is the lag performance function value at the current moment.
  • the high dynamic satellite tracking method obtains the relationship between the carrier tracking error and the maximum output value of fast Fourier transform (FFT) by analyzing the characteristics of the carrier amplitude spectrum.
  • FFT fast Fourier transform
  • a new carrier is designed.
  • a tracking structure is used to track satellite signals.
  • the present invention can obtain high tracking accuracy in both static and dynamic environments, has simple design and high engineering use value.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)

Abstract

一种基于最速上升法的高动态卫星跟踪方法，包括：首先剥离测距码序列，接着对载波进行混频以及快速傅里叶变换处理，得到载波跟踪误差与快速傅里叶变换(FFT)输出幅度谱最大值之间的映射关系，最后根据最速上升法的原理对载波进行跟踪。该高动态卫星跟踪方法在静态和动态环境下均能获得较高的跟踪精度，而且该卫星跟踪方法不需要外部传感器辅助，不需要预先知道噪声的先验统计信息，具有较好的鲁棒性和稳定性，具有较高的工程使用价值。

Description

一种基于最速上升法的高动态卫星跟踪方法 技术领域
本发明属于卫星信号处理领域，特别涉及了一种基于最速上升法的高动态卫星跟踪方法。
背景技术
高超音速飞行器以其潜在的军事、政治和经济价值逐渐受到人们的关注。导航是高超声速飞行器的关键技术之一。GNSS作为导航系统的关键部件，在高动态环境下，GNSS接收机的载波跟踪回路容易失锁。跟踪环路带宽增加会使得跟踪环路具有更好的动态性能，但是同时引入较大的跟踪误差。
根据是否使用外部传感器，提升高动态环境下载波跟踪环路跟踪性能的方法可分为两类：一类是使用惯性导航系统辅助，另一类是改进自身结构。
惯性导航系统作为高超声速飞行器必不可少的传感器，通过将GNSS/INS超紧耦合系统预测的多普勒频移值反馈到载波跟踪回路中，提高接收机的动态性能。外这种方法具有精度高、响应快的优点，但它要求载波跟踪环路与外部设备的精确同步，这可能会给实现带来更多的成本和困难。
改进载波跟踪环路的结构有三种方法，即基于鉴频器的方法、基于估计器的方法和基于矢量的方法。基于鉴频器的方法仍然遵循传统的锁相环结构，通过频率锁定环或Wigner-Ville分布(WVD)的辅助，缓解了这种结构高动态性和高精度之间的矛盾，但这种方法需要非常复杂的机构设计；基于估计器的方法用一个估计器代替PLL的鉴频器和环路滤波器，该估计器的结构可以采用任何合适的形式，如卡尔曼滤波(KF)、扩展卡尔曼滤波(EKF)、无迹卡尔曼滤波(UKF)、最大似然和基于FFT，这种方法需要事先知道噪声的统计信息，才能得到更好的载波估计；基于矢量的方法用一个导航滤波器代替每个通道中的单个跟踪回路，在已知接收机位置和速度的情况下，根据计算得到的伪距和伪距率，得到本地信号发生器对各卫星的反馈，这种方法的主要缺点是所有卫星的处理数据都是密切 相关的，一个通道中的任何错误都可能损坏其他通道。
上述算法在改善跟踪环路的动态性能的同时往往伴随着复杂的机构设计、外部高精度传感器辅助、或预先知晓先验信息。
发明内容
为了解决上述背景技术提出的技术问题，本发明提供一种一种不受高动态影响的基于最速上升法的高动态卫星跟踪方法。
为了实现上述技术目的，本发明的技术方案为：一种基于最速上升法的高动态卫星跟踪方法，包括：
步骤一：根据测距码序列的自相关特性，将本地生成的测距码序列C l(n)与输入到跟踪环路的中频信号x(n)做相关运算，得到码剥离后的中频信号s(n)；
步骤二：将所述剥离后的中频信号s(n)与本地生成的即时载波信号x P(n)混频得到第一混频信号y P(n)，将所述剥离后的中频信号s(n)与超前载波信号x E(n)混频或者滞后载波信号x L(n)混频得到第二混频信号y L(n)或第三混频信号y E(n)；
步骤三：对所述第一混频信号y P(n)做降采样处理得到第四混频信号y P(k)，对所述第二混频信号y L(n)或所述第三混频信号y E(n)做降采样处理得到第五混频信号y L(k)或第六混频信号y E(k)；
步骤四：对所述第四混频信号y P(k)和所述第五混频信号y L(k)做快速傅里叶变换处理得到快速傅里叶变换输出幅度谱的最大值，或者对所述第四混频信号y P(k)和所述第六混频信号y E(k)做快速傅里叶变换处理得到快速傅里叶变换输出幅度谱的最大值；
步骤五：利用最速上升法以及所述快速傅里叶变换输出幅度谱的最大值对载波进行跟踪。
可选的，在上述的步骤一中，进一步的，输入到跟踪回路的离散中频的信号结构如式(1)所示。
x(n)＝AC(n)D(n)exp[i(2πf 1n+θ 0)]   (1)
测距码的剥离过程如式(2)所示。
Figure PCTCN2021089030-appb-000001
其中，i是虚部符号，A是中频信号x(n)的幅度，C(n)是测距码序列，D(n)是信息码序列，f 1是到达跟踪回路信号的频率，θ 0是初始相位，R(·)是测距码的自相关函数，
Figure PCTCN2021089030-appb-000002
是本地测距码和接收信号中调制测距码之间的相位差，C l(n)为本地生成的测距码序列。
可选的，上述步骤二进一步包括：若最速上升是采用左偏导，则选择是将所述剥离后的中频信号s(n)分别与本地生成的即时载波信号x P(n)和滞后载波信号x L(n)混频，混频后分别得到信号第一混频信号y P(n)和第二混频信号y L(n)；
若最速上升是采用右偏导，则选择是将所述剥离后的中频信号s(n)分别与本地生成的即时载波信号x P(n)和超前载波信号x E(n)混频，混频后分别得到信号第一混频y P(n)和第三混频信号y E(n)。
在上述技术方案中，本地生成的所述的即时载波的信号结构定义为：
x P(n)＝exp[-i(2πf 2n)]   (3)
本地生成的所述的超前载波的信号结构定义为：
x E(n)＝exp{-i[(2π(f 2+d)n]}   (4)
本地生成的所述的滞后载波的信号结构定义为：
x L(n)＝exp{-i[(2π(f 2-d)n]}   (5)
其中，f 2是即时载波信号频率，d是频率间隔。
可选的，在上述的若最速上升是采用左偏导，则选择是将所述剥离后的中频 信号s(n)分别与本地生成的即时载波信号x P(n)和滞后载波信号x L(n)混频，混频后分别得到信号第一混频信号y P(n)和第二混频信号y L(n)，进一步包括：
混频过程如下式所示：
Figure PCTCN2021089030-appb-000003
其中，Δf是接收信号和本地即时载波之间的频率差，可以用表示Δf＝f 2-f 1。
可选的，在上述的步骤三中，进一步的：所述第一混频信号y P(n)的降采样过程可以用公式(7)表示：
Figure PCTCN2021089030-appb-000004
同样地所述第二混频信号y L(n)的降采样过程可以用公式(8)表示：
Figure PCTCN2021089030-appb-000005
其中，T s为初始采样周期，M为求和运算点数。
可选的，在上述步骤四中，进一步的：
所述第四混频信号y P(k)可以用来表示连续函数经过离散和截断两个处理过程后的信号，如公式(9)表示
Figure PCTCN2021089030-appb-000006
式中T L表示矩形窗的长度，rect(·)表示矩形函数，δ(·)为狄拉克函数。
经过快速傅里叶变换后，快速傅里叶变换输出幅度谱的最大值和Δf的关系可以用公式(10)表示：
Figure PCTCN2021089030-appb-000007
式中round是取整函数，M FFT_P(Δf)为快速傅里叶变换输出幅度谱的最大值，sinc(·)为sinc函数。
可选的，在上述步骤五中，进一步的：
根据最速上升法的原理，载波跟踪过程可以用公式(11)表示
Figure PCTCN2021089030-appb-000008
其中，Δf k+1为下一时刻接收信号和本地即时载波之间的频率差，Δf k为当前刻接收信号和本地即时载波之间的频率差，μ为控制步长，P F_P| k为当前时刻即时性能函数值，P F_L| k为当前时刻滞后性能函数值。
本发明的一个实施例相对于现有技术的有益效果是：该实施例通过构建不受高动态影响的性能函数，利用该函数和最速上升法构建高动态跟踪结构，利用该结构对卫星信号进行跟踪，该跟踪方法设计简单、不需要外部传感器辅助且不需要预先知道噪声的先验统计信息，具有较好的鲁棒性和稳定性。
附图说明
图1是本发明实施例的流程示意图；
图2是本发明实施例的整体流程架构图。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅是本发明的一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
实施例1
本实施例提供一种基于最速上升法的高动态卫星跟踪方法，如图1和图2所示，包括以下步骤：
S10：根据测距码序列的自相关特性，将本地生成的测距码序列C l(n)与输入到跟踪环路的中频信号x(n)做相关运算，得到码剥离后的中频信号s(n)。
该步骤的作用是剥离测距码序列，具体的如下：
假设输入到跟踪回路的离散中频(IF)的信号结构如式(1)所示。
x(n)＝AC(n)D(n)exp[i(2πf 1n+θ 0)]   (1)
其中，i是虚部符号，A是信号x(n)的幅度，C(n)是测距码序列，D(n)是信息码序列，f 1是到达跟踪回路信号的频率，θ 0是初始相位。
测距码的剥离过程如式(2)所示。
Figure PCTCN2021089030-appb-000009
其中，R(·)是测距码的自相关函数，
Figure PCTCN2021089030-appb-000010
是本地测距码和接收信号中调制测距码之间的相位差，C l(n)为本地生成的测距码序列。。
S20：将所述剥离后的中频信号s(n)与本地生成的即时载波信号x P(n)混频得到第一混频信号y P(n)，将所述剥离后的中频信号s(n)与超前载波信号x E(n)混频或者滞后载波信号x L(n)混频得到第二混频信号y L(n)或第三混频信号y E(n)。
具体的，如果最速上升是采用左偏导，则选择是将中频信号s(n)分别与本地生成的即时载波信号x P(n)和滞后载波信号x L(n)混频，混频后分别得到第一混频 信号y P(n)和第二混频信号y L(n)；如果最速上升是采用右偏导，则选择是将中频信号s(n)分别与本地生成的即时载波信号x P(n)和超前载波信号x E(n)混频，混频后分别得到信号第一混频信号y P(n)和第三混频信号y E(n)。
在该步骤中，需要对本地产生的载波信号的结构进行定义，本地生成的即时载波的信号结构定义为：
x P(n)＝exp[-i(2πf 2n)]   (3)
本地生成的超前载波的信号结构定义为：
x E(n)＝exp{-i[(2π(f 2+d)n]}   (4)
本地生成的滞后载波的信号结构定义为：
x L(n)＝exp{-i[(2π(f 2-d)n]}   (5)
其中，f 2是即时载波信号频率，d是频率间隔。
以最速上升法采用左偏导为例，混频过程如下式所示。
Figure PCTCN2021089030-appb-000011
其中，Δf是接收信号和本地即时载波之间的频率差，可以用表示Δf＝f 2-f 1。
S30：对所述第一混频信号y P(n)做降采样处理得到第四混频信号y P(k)，对所述第二混频信号y L(n)或所述第三混频信号y E(n)做降采样处理得到第五混频信号y L(k)或第六混频信号y E(k)。
由于进行载波混频后的信号频率已经远远小于采样率，如果继续采用该采样率，后续计算将占用大量的计算资源，为此采用求和的方式进行降采样，经过降采样处理，第一混频信号y P(n)和第二混频信号y L(n)分别变为第四混频信号 y P(k)和第五混频信号y L(k)，或第一混频信号y P(n)和第三混频信号y E(n)分别变为第四混频信号y P(k)和第六混频信号y E(k)。
降采样的目的是减小后续快速傅里叶变换(以下简称FFT)过程的计算量，由于采样率fs远大于接收信号和本地即时载波之间的频率差Δf，所以，第一混频信号y P(n)的降采样过程可以用公式(7)表示。
Figure PCTCN2021089030-appb-000012
同样地第二混频信号y L(n)的降采样过程可以用公式(8)表示。
Figure PCTCN2021089030-appb-000013
其中，T s为初始采样周期，M为求和运算点数。
S40：对所述第四混频信号y P(k)和所述第五混频信号y L(k)做快速傅里叶变换处理得到快速傅里叶变换输出幅度谱的最大值或者对所述第四混频信号y P(k)和所述第六混频信号y E(k)做快速傅里叶变换处理得到快速傅里叶变换输出幅度谱的最大值。
具体的第四混频信号y P(k)用来表示连续函数经过离散和截断两个处理过程后的信号，可以用公式(9)表示
Figure PCTCN2021089030-appb-000014
式中T L表示矩形窗的长度，rect(·)表示矩形函数，δ(·)为狄拉克函数。
所以经过FFT后，FFT输出幅度谱的最大值和Δf的关系可以用公式(10)表示
Figure PCTCN2021089030-appb-000015
式中round是取整函数，M FFT_P(Δf)为快速傅里叶变换输出幅度谱的最大值，sinc(·)为sinc函数。
假设2MT s＜＜T L并且y p(k)信号频率Δf在
Figure PCTCN2021089030-appb-000016
内，公式(10)可以被简写为
Figure PCTCN2021089030-appb-000017
为了减弱信号功率对载波跟踪环路的影响，需要对式(11)进行归一化。由于信号x(n)的振幅A在短时间内可以看作一个常数并且测距码自相关函数的最大值为1，所以，短时间内M FFT_P的最大值可用于使式(12)的归一化。归一化过程如公式(12)所示。
Figure PCTCN2021089030-appb-000018
式中，N c是M FFT_P在短时间内的最大值。
所以M FFT_P在本实施例的性能表面上的位置可以用公式(13)表示。
Figure PCTCN2021089030-appb-000019
相似地，M FFT_L在本实施例的性能表面上的位置可以用公式(14)表示
Figure PCTCN2021089030-appb-000020
S50：利用最速上升法以及所述快速傅里叶变换输出幅度谱的最大值对载波 进行跟踪。
具体的根据最速上升法的原理，载波跟踪过程可以用公式(15)表示。
Figure PCTCN2021089030-appb-000021
其中，Δf k+1为下一时刻接收信号和本地即时载波之间的频率差，Δf k为当前刻接收信号和本地即时载波之间的频率差，μ为控制步长，P F_P| k为当前时刻即时性能函数值，P F_L| k为当前时刻滞后性能函数值。
该高动态卫星跟踪方法通过对载波幅度谱特性进行分析，得到载波跟踪误差与快速傅里叶变换(FFT)输出最大值之间的关系，根据最速上升法的原理，设计了一种新的载波跟踪结构，并利用该结构对卫星信号进行跟踪。本发明在静态和动态环境下均能获得较高的跟踪精度，设计简单，具有较高的工程使用价值。
以上所述仅为本发明的一种实施方式，并非因此限制本发明的专利范围，凡是利用本发明说明书及附图内容所作的等效结构或等效流程变换，或直接或间接运用在其他相关的技术领域，均同理包括在本发明的专利保护范围内。

Claims (8)

  1. 一种基于最速上升法的高动态卫星跟踪方法，其特征在于，包括：
    根据测距码序列的自相关特性，将本地生成的测距码序列C l(n)与输入到跟踪环路的中频信号x(n)转换成码剥离后的中频信号s(n)；
    将所述剥离后的中频信号s(n)与本地生成的即时载波信号x P(n)混频得到第一混频信号y P(n)，将所述剥离后的中频信号s(n)与超前载波信号x E(n)混频或者滞后载波信号x L(n)混频得到第二混频信号y L(n)或第三混频信号y E(n)；
    对所述第一混频信号y P(n)做降采样处理得到第四混频信号y P(k)，对所述第二混频信号y L(n)或所述第三混频信号y E(n)做降采样处理得到第五混频信号y L(k)或第六混频信号y E(k)；
    对所述第四混频信号y P(k)和所述第五混频信号y L(k)做快速傅里叶变换处理得到快速傅里叶变换输出幅度谱的最大值或者对所述第四混频信号y P(k)和所述第六混频信号y E(k)做快速傅里叶变换处理得到快速傅里叶变换输出幅度谱的最大值；
    利用最速上升法以及所述快速傅里叶变换输出幅度谱的最大值对载波进行跟踪。
  2. 根据权利要求1所述的高动态卫星跟踪方法，其特征在于，在所述的根据测距码序列的自相关特性，将本地生成的C l(n)序列与输入到跟踪环路的中频信号x(n)转换成码剥离后的中频信号s(n)中，进一步包括：
    输入到跟踪回路的离散中频的信号结构如式(1)所示；
    x(n)＝AC(n)D(n)exp[i(2πf 1n+θ 0)]  (1)
    测距码的剥离过程如式(2)所示：
    Figure PCTCN2021089030-appb-100001
    其中，i是虚部符号，A是中频信号x(n)的幅度，C(n)是测距码序列，D(n)是 信息码序列，f 1是到达跟踪回路信号的频率，θ 0是初始相位，R(·)是测距码的自相关函数，
    Figure PCTCN2021089030-appb-100002
    是本地测距码和接收信号中调制测距码之间的相位差，C l(n)为本地生成的测距码序列。
  3. 根据权利要求1或2所述的高动态卫星跟踪方法，其特征在于，所述的将所述剥离后的中频信号s(n)与本地生成的即时载波信号x P(n)混频得到第一混频信号y P(n)，将所述剥离后的中频信号s(n)与超前载波信号x E(n)混频或者滞后载波信号x L(n)混频得到第二混频信号y L(n)或第三混频信号y E(n)，进一步包括：
    若最速上升是采用左偏导，则选择是将所述剥离后的中频信号s(n)分别与本地生成的即时载波信号x P(n)和滞后载波信号x L(n)混频，混频后分别得到信号第一混频信号y P(n)和第二混频信号y L(n)；
    若最速上升是采用右偏导，则选择是将所述剥离后的中频信号s(n)分别与本地生成的即时载波信号x P(n)和超前载波信号x E(n)混频，混频后分别得到信号第一混频y P(n)和第三混频信号y E(n)。
  4. 根据权利要求3所述的高动态卫星跟踪方法，其特征在于，本地生成的所述的即时载波信号结构定义为：
    x P(n)＝exp[-i(2πf 2n)]  (3)
    本地生成的所述的超前载波信号结构定义为：
    x E(n)＝exp{-i[(2π(f 2+d)n]}  (4)
    本地生成的所述的滞后载波信号结构定义为：
    x L(n)＝exp{-i[(2π(f 2-d)n]}  (5)
    其中，f 2是即时载波信号频率，d是频率间隔。
  5. 根据权利要求4所述的高动态卫星跟踪方法，其特征在于，所述的若最 速上升是采用左偏导，则选择是将所述剥离后的中频信号s(n)分别与本地生成的即时载波信号x P(n)和滞后载波信号x L(n)混频，混频后分别得到信号第一混频信号y P(n)和第二混频信号y L(n)，进一步包括：
    混频过程如下式所示；
    Figure PCTCN2021089030-appb-100003
    其中，Δf是接收信号和本地即时载波之间的频率差，Δf＝f 2-f 1。
  6. 根据权利要求5所述的高动态卫星跟踪方法，其特征在于，在所述的对所述第一混频信号y P(n)做降采样处理得到第四混频信号y P(k)，对所述第二混频信号y L(n)或所述第三混频信号y E(n)做降采样处理得到第五混频信号y L(k)或第六混频信号y E(k)中，进一步的：所述第一混频信号y P(n)的降采样过程以公式(7)表示：
    Figure PCTCN2021089030-appb-100004
    Figure PCTCN2021089030-appb-100005
    Figure PCTCN2021089030-appb-100006
    所述第二混频信号y L(n)的降采样过程以公式(8)表示：
    Figure PCTCN2021089030-appb-100007
    其中，T s为初始采样周期，M为求和运算点数。
  7. 根据权利要求6所述的高动态卫星跟踪方法，其特征在于，在所述对所述第四混频信号y P(k)和所述第五混频信号y L(k)做快速傅里叶变换处理得到快速傅里叶变换输出幅度谱的最大值或者对所述第四混频信号y P(k)和所述第六混频信号y E(k)做快速傅里叶变换处理得到快速傅里叶变换输出幅度谱的最大值中，进一步的：
    所述第四混频信号y P(k)用来表示连续函数经过离散和截断两个处理过程后的信号，以公式(9)表示：
    Figure PCTCN2021089030-appb-100008
    式中T L为矩形窗的长度，rect(·)为矩形函数，δ(·)为狄拉克函数；
    经过快速傅里叶变换后，快速傅里叶变换输出幅度谱的最大值和Δf的关系以公式(10)表示：
    Figure PCTCN2021089030-appb-100009
    其中，round是取整函数，M FFT_P(Δf)为快速傅里叶变换输出幅度谱的最大值，sinc(·)为sinc函数。
  8. 根据权利要求7所述的高动态卫星跟踪方法，其特征在于，在所述的利用最速上升法以及所述快速傅里叶变换输出幅度谱的最大值对载波进行跟踪中，进一步的：
    根据最速上升法的原理，载波跟踪过程以公式(11)表示：
    Figure PCTCN2021089030-appb-100010
    其中，Δf k+1为下一时刻接收信号和本地即时载波之间的频率差，Δf k为当前刻接收信号和本地即时载波之间的频率差，μ为控制步长，P F_P| k为当前时刻即时性能函数值，P F_L| k为当前时刻滞后性能函数值。
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