CN108562918B - BOC (n, n) ambiguity-free capturing method and device based on correlation shift - Google Patents

BOC (n, n) ambiguity-free capturing method and device based on correlation shift Download PDF

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CN108562918B
CN108562918B CN201810385165.3A CN201810385165A CN108562918B CN 108562918 B CN108562918 B CN 108562918B CN 201810385165 A CN201810385165 A CN 201810385165A CN 108562918 B CN108562918 B CN 108562918B
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signal
boc
detection
signals
intermediate frequency
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CN108562918A (en
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孙希延
郝放
纪元法
甄卫民
彭良福
蔚保国
甘兴利
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Guilin University of Electronic Technology
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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

Abstract

The invention provides a BOC (n, n) ambiguity-free capturing method and device based on correlation shift, wherein the method comprises the steps of obtaining in-phase signals and orthogonal signals; obtaining odd and even branch signals; carrying out modulus taking on the complex signal I + jQ after carrier stripping, and obtaining the modulus result and the odd branch signal CO(t) multiplying by each other, and integrating to obtain
Figure DDA0001641992980000011
To pair
Figure DDA0001641992980000012
Hysteresis
Figure DDA0001641992980000013
The number of sampling points is obtained by negation
Figure DDA0001641992980000014
Will be provided with
Figure DDA0001641992980000015
And
Figure DDA0001641992980000016
multiplying to obtain the detected quantity S with side peakOE(ii) a To SOEModulus is taken to obtain | SOEI, then SOEAdding the sum | SOE | to obtain a detection amount without blurring; comparing the detection quantity with a detection threshold value set by a decision device, and if the detection value exceeds the detection threshold value, considering that the signal is accurately captured; if the detection value does not exceed the detection threshold value, the signal is not accurately captured, and the steps are repeated. Based on the idea of splitting and reconstructing, the method splits the local BOC into two odd-even unit signals, reconstructs the unit correlation functions of the two signals and the received signals, completely eliminates the multimodal property while keeping the advantages of narrow correlation main peaks, and improves the capture sensitivity.

Description

BOC (n, n) ambiguity-free capturing method and device based on correlation shift
Technical Field
The invention belongs to the technical field of satellite navigation positioning, and particularly relates to a BOC (n, n) ambiguity-free capturing method and device based on correlation shift.
Background
At present, in order to fully utilize frequency band resources and enhance anti-interference capability of various global satellite navigation systems, a new modulation mode, namely Binary Offset Carrier (BOC) modulation is provided, compared with BPSK modulation, the BOC modulation has the advantages that firstly, the BOC modulation uses square wave subcarriers to pre-modulate pseudo-random codes to enable signal spectrums to be symmetrically split at the edges of frequency bands, the separation distance changes along with the change of modulation orders, limited spectrum resources are fully utilized, interference among signals is reduced, secondly, a narrower correlation main peak exists in an autocorrelation function, and acquisition precision is improved, the BOC modulation signal has the main defects that the autocorrelation function has multimodality in +/-1 chip span on two sides of a main peak, side peaks are easily mistakenly acquired in the acquisition process, acquisition ambiguity is caused, the method for eliminating the mistaken acquisition problem is mainly divided into two types of frequency domain processing and time domain processing, namely a L IKE method for frequency domain processing, the BOC signal is regarded as the superposition of multiple BPSK signals, the obtained detection peak is one, but the correlation is eliminated by the main peak of frequency domain processing, the square edge filtering of a single peak, the BPSK signal is added to a single peak, the side peak elimination of the PRN signal is eliminated by a typical square edge filtering algorithm, and the PRN filtering algorithm is not added, and the PRN filtering is added to the side peak, the side peak elimination of the PRN signal, the PRN signal is effectively eliminated, and the PRN signal is added, and the PRN signal, the PRN signal is added to.
Disclosure of Invention
In view of the above drawbacks of the prior art, an object of the present invention is to provide a method and an apparatus for ambiguity-free signal acquisition for BOC (n, n) signals, so as to solve the problem in the prior art that the autocorrelation function of a Binary Offset Carrier (BOC) modulation technique has multiple secondary peaks and thus causes ambiguity in signal acquisition.
To achieve the above and other related objects, the present invention provides a ambiguity-free acquisition method for BOC (n, n) signals, the acquisition method comprising the steps of:
the method comprises the following steps: acquiring a digital intermediate frequency BOC signal of discrete time, and mixing the digital intermediate frequency BOC signal with a local carrier by adopting a quadrature demodulation method respectively to obtain an in-phase I signal and a quadrature Q signal;
step two: the local PRN sequence modulates subcarrier to obtain local BOC signal, and the local BOC signal is split into odd and even branch signals, which are marked as CO(t) and CE(t)；
Step three: carrying out modulus taking on the complex signal I + jQ after carrier stripping, and obtaining the modulus result and the odd branch signal CO(t) multiplying by each other, and integrating to obtain
Figure GDA0002447740080000021
Step four: to pair
Figure GDA0002447740080000022
Hysteresis
Figure GDA0002447740080000023
The number of sampling points is obtained by negation
Figure GDA0002447740080000024
T of itCIs the width of one chip;
step five: will be provided with
Figure GDA0002447740080000025
And
Figure GDA0002447740080000026
multiplying to obtain the detected quantity S with side peakOE；
Step six: to SOEModulus is taken to obtain | SOEI, then SOEAnd | SOEAdding | to obtain a detection quantity V without ambiguity;
step seven: comparing the detection quantity V with a detection threshold value set by a decision device, and if the detection value exceeds the detection threshold value, considering that the signal is accurately captured; if the detection value does not exceed the detection threshold value, the signal is not accurately captured, and the steps from one step to six are repeated.
Preferably, the method further comprises the step eight: when the satellite signal required for positioning is found to exist, the GNSS receiver continues to normally receive the satellite signal to obtain a navigation message, and positioning is realized; if the required satellite signal is not found, the satellite is replaced, and the steps from one step to seven are repeated.
Preferably, the method for acquiring the digital intermediate frequency BOC signal of the discrete time comprises:
receiving satellite BOC signals;
the BOC signal is subjected to down-conversion to generate an intermediate frequency signal, and the intermediate frequency signal is subjected to digital-to-analog conversion to a discrete-time digital intermediate frequency BOC signal.
Preferably, the second step is specifically: the local PRN sequence modulates subcarrier to obtain BOC code, divides each chip of local BOC signal equally, cuts out the chip information of the first half or the second half of each pseudo-random code chip in turn, splits into odd and even two branch signals, and marks them as CO(t) and CE(t)。
To achieve the above and other related objects, the present invention provides a correlation shift BOC (n, n) -based unambiguous capturing apparatus, comprising:
the signal receiving module is used for acquiring digital intermediate frequency BOC signals of discrete time, and mixing the digital intermediate frequency BOC signals with local carrier waves by adopting a quadrature demodulation method respectively to obtain in-phase I and quadrature Q signals;
a signal splitting module, configured to split a local BOC signal obtained by modulating a subcarrier with a local PRN sequence into an odd branch signal and an even branch signal, which are respectively denoted as CO(t) and CE(t)；
An integration module for taking the modulus of the complex signal I + jQ after the carrier stripping, the modulus result and the odd branch signal CO(t) multiplying by each other, and integrating to obtain
Figure GDA0002447740080000027
Negation module for pairing
Figure GDA0002447740080000028
Hysteresis
Figure GDA0002447740080000029
The number of sampling points is obtained by negation
Figure GDA00024477400800000210
T of itCIs the width of one chip;
a detection amount acquisition module I for connecting
Figure GDA0002447740080000031
And
Figure GDA0002447740080000032
multiplying to obtain the detected quantity S with side peakOE；
A detection amount acquisition module II for comparing SOEModulus is taken to obtain | SOEI, then SOEAnd | SOEAdding | to obtain a detection quantity V without ambiguity;
the comparison module is used for comparing the detection quantity V with a detection threshold value set by the decision device, and if the detection value exceeds the detection threshold value, the signal is considered to be accurately captured; if the detection value does not exceed the detection threshold, the signal is deemed to have not been accurately captured.
Preferably, the device further comprises a positioning module, configured to continue to normally receive the satellite signal through the GNSS receiver when the satellite signal required for positioning is found to exist, so as to obtain a navigation message, thereby implementing positioning.
Preferably, the signal receiving module includes:
the receiving module is suitable for receiving a satellite BOC signal;
the down-conversion module is used for carrying out frequency conversion on the BOC signal to generate an intermediate frequency signal;
the analog-to-digital converter is used for converting the intermediate frequency signal into a digital intermediate frequency BOC signal of discrete time;
and the frequency mixing module is used for mixing the digital intermediate frequency BOC signal with a local carrier by adopting a quadrature demodulation method to obtain an in-phase I signal and a quadrature Q signal.
As described above, the ambiguity-free acquisition method and apparatus for BOC (n, n) signals according to the present invention have the following advantages:
(1) the invention provides a ambiguity-free capturing method suitable for BOC (n, n) signals, which does not adopt the traditional parallel code phase capturing mode but adopts a segmented matched filtering and FFT mode in the capturing mode, thereby not only saving the operation amount, but also completing the capturing in a plurality of working clocks, which has the effect that the parallel code phase capturing mode cannot receive signals of 1 ms. In the algorithm, based on the splitting and reconstructing idea, the local BOC signal is split into two odd-even unit signals, the unit correlation functions of the two signals and the received signal are reconstructed, the multi-peak property is completely eliminated while the advantages of the narrow correlation main peak are kept, and the capture sensitivity is improved. Therefore, the problems of mistaken capture and missed capture caused by multi-peak performance in the capture process are avoided, the BOC signal capture precision is improved, and the search time is shortened.
(2) The ambiguity-free capturing method suitable for the BOC (n, n) signal provided by the invention can meet the ambiguity-free capturing of the BOC (n, n) signal, the time division multiplexing TMBOC (6,1,4/33) signal adopted by the L1C wave band of the American GPS satellite navigation system and the Galileo E1 signal modulated by the code division CBOC (6,1,1/11) adopted by the European Union Galileo satellite navigation system, namely is suitable for the main BOC modulation adopted in each current large satellite navigation system, and ensures wide algorithm applicability.
Drawings
FIG. 1 is a diagram of the principle of a correlation shift based BOC (n, n) unambiguous acquisition algorithm;
FIG. 2(a) shows local BOC (1,1) signal generation;
FIG. 2(b) shows local CBOC (6,1,1/11) signal generation;
FIG. 2(c) shows local TMBOC (6,1,4/33) signal generation;
FIG. 3 illustrates the generation of a local parity tributary signal;
FIG. 4(a) is a reconstruction of the BOC (1,1) correlation shift function;
FIG. 4(b) reconstruction of CBOC (6,1,1/11) correlation shift function;
FIG. 4(c) reconstruction of TMBOC (6,1,4/33) correlation shift function;
FIG. 5 is a graph of detection probability versus signal-to-noise ratio;
FIG. 6 shows the results of three-dimensional acquisition of the BOC (1,1) signal correlation shift function;
FIG. 7 is a comparison of the results of the four capture methods versus the BOC (1,1) capture;
FIG. 8 is a comparison graph of peak-to-average ratios of four methods;
FIG. 9(a) is a diagram showing the two-dimensional acquisition result of the BOC (1,1) signal by the acquisition method of the present invention;
FIG. 9(b) is a graph showing the two-dimensional acquisition result of the CBOC (6,1,1/11, +) signal by the acquisition method of the present invention;
FIG. 9(c) is a graph of the two-dimensional acquisition of TMBOC (6,1,4/33) signal by the acquisition method of the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
The invention provides a correlation shift BOC (n, n) -based ambiguity-free capturing method, which is characterized in that a local BOC signal is split into odd and even unit branch signals by utilizing the splitting and reconstructing idea, and the cross-correlation function of any one of the two branch signals and a received BOC signal is reconstructed.
Taking BOC (n, n) modulation signals as an example, the specific implementation scheme is as follows:
the method comprises the following steps: the method comprises the steps that a received satellite BOC signal is converted into an intermediate frequency signal through down-conversion by a down-conversion module, then the intermediate frequency signal is converted into a digital intermediate frequency BOC signal with discrete time through an analog-to-digital (A/D) converter, the digital intermediate frequency BOC signal is marked as S (t), and the digital intermediate frequency BOC signal and a local carrier are mixed by adopting an orthogonal demodulation method respectively to obtain an in-phase I signal and an orthogonal Q signal. The down-converted digital intermediate frequency signal can be expressed as:
Figure GDA0002447740080000051
PSis the power of the input signal, C (t) is the PRN code, D (t) is the navigation data, τ is the code delay of the input signal, fDIs the Doppler frequency, f, of the input signalIFIs the intermediate frequency, Sc (t) is the subcarrier, and n (t) is the noise term.
The input signal is mixed with local carrier to obtain inphase I and orthogonal Q signals as shown in the following
I(t)＝S(t)[cos[2π(fIF+fD)t]+cos[2π(fIF+fD)Ts]]+n(t)
Q(t)＝S(t)[cos[2π(fIF+fD)t]+cos[2π(fIF+fD)Ts]]+n(t)
Step two: the local PRN sequence modulates subcarrier to obtain BOC code, divides each chip of local BOC signal equally, cuts out the chip information of the first half or the second half of each pseudo-random code chip in turn, and can split into odd and even branch signals marked as CO(t) and CE(t)。
Mathematical model of local PRN sequence:
Figure GDA0002447740080000052
in the formula:
Figure GDA0002447740080000058
is a period of TCAmplitude of 1 rectangular pulse, TCIs one chip wide, CiIs a symbol of a chip, Ci∈ (-1, 1.) the local subcarrier is mathematically represented as:
Figure GDA0002447740080000053
Figure GDA0002447740080000054
is a period of TscThe amplitude of the rectangular pulse of (1), i.e., the width of one subcarrier pulse. djIs the pulse symbol of the subcarrier and M is the total number of pulses within one PRN chip. For BOC (1,1) signal, dj∈(-1,1)，
Figure GDA0002447740080000055
And M is 2. Using the two mathematical models described above, a local BOC (n, n) baseband sequence is generated:
Figure GDA0002447740080000056
fig. 2(a) illustrates the generation of the local BOC (1,1) baseband sequence, which can generate local CBOC (6,1,1/11) and TMBOC (6,1,4/33) baseband sequences, as shown in fig. 2(b) and 2 (c). Since the subcarriers are strictly synchronized with the PRN code sequences, the above equation can be simplified as:
Figure GDA0002447740080000057
and taking the length of each PRN chip as a reference, cutting the PRN chip into two equal parts according to the pulse duration of the subcarrier, wherein the front half part and the rear half part are reset to zero to form an odd branch BOC signal, and the front half part is zero and the rear half part is added to form a BOC even branch signal. CO(t) represents the odd branch portion, CE(t) represents an even branch portion.
Figure GDA0002447740080000061
Figure GDA0002447740080000062
NcIs the number of PRN chips in a period of time, doFor the sub-carrier pulse symbol corresponding to the first half chip based on the length of each PRN chip, dEIs a subcarrier pulse symbol corresponding to the second half chip based on the length of each PRN chip, and do&dE∈dj。
FIG. 3 is a schematic diagram of the generation of the local BOC (1,1) parity branch signal.
Step three: taking a modulus of the complex signal I + jQ after carrier stripping, and splitting the complex signal I + jQ from a local BOC signal to obtain two unit signals CO(t) or CEMultiplying one of (t) by each other, and integrating to obtain
Figure GDA0002447740080000063
And
Figure GDA0002447740080000064
Figure GDA0002447740080000065
Figure GDA0002447740080000066
in the formula, Ro(τ) is the correlation function of the odd-path signal and the received signal, RE(τ) is the correlation function of the even signal and the received signal.
Step four: to pair
Figure GDA0002447740080000067
Hysteresis
Figure GDA0002447740080000068
The number of sampling points is obtained by negation
Figure GDA0002447740080000069
(or to
Figure GDA00024477400800000610
Advance in
Figure GDA00024477400800000611
The number of sampling points is obtained by negation
Figure GDA00024477400800000612
) Of, T thereofCIs one chip wide, calculated here
Figure GDA00024477400800000613
Step five: integrating the result
Figure GDA00024477400800000614
And
Figure GDA00024477400800000615
multiplying to obtain the detected amount with side peak as SOE。
Figure GDA00024477400800000616
And
Figure GDA00024477400800000617
can be simplified as follows:
Figure GDA00024477400800000618
Figure GDA00024477400800000619
SEis that
Figure GDA00024477400800000620
Signal part of, SOIs that
Figure GDA00024477400800000621
The signal portion of (a), the multiplication of the two forms giving SOE
SOE＝[SE(Δτ,ΔfD)+NE]×[SO(Δτ,ΔfD)+NO]
＝SE(Δτ,ΔfD)×SO(Δτ,ΔfD)+
SE(Δτ,ΔfD)×NO+
SO(Δτ,ΔfD)×NE+
NE×NO
Step six: according to the reconstruction rule pair SOETaking a model to obtain | SOEI, then SOEAnd | SOEAnd | adding to obtain a detection quantity without blurring and recording as V.
V＝(|SOE|)+(SOE)
Fig. 4(a), 4(b), and 4(c) are schematic diagrams of reconstruction of the parity correlation functions of BOC (1,1), CBOC (6,1,1/11), and TMBOC (6,1,4/33), respectively.
Step seven: and comparing the detection quantity V with a detection threshold value set by the decision device, and if the detection value exceeds the detection threshold value, considering that the signal is accurately captured, and obtaining the conclusion whether the satellite signal required by positioning exists in the received intermediate frequency input signal. If the detection value does not exceed the detection threshold value, the signal is not accurately captured, and the steps from one step to six are repeated.
Step eight: when the satellite signal required for positioning is found to exist, the GNSS receiver continues to normally receive the satellite signal to obtain a navigation message, and positioning is realized; if the required satellite signal is not found, the satellite is replaced, and the steps from one step to seven are repeated.
Assuming that an input BOC (1,1) signal is input, the capturing and judging are based on the fact that the error between the position where the maximum value appears and the offset position of the pseudo code under different signal-to-noise ratios is within plus and minus one quarter of a chip, the detection probability curves of the method, the method before the modulo addition of the invention and the ASPeCT and BPSK-L IKE methods are shown in figure 5. if the detection probability of 90 percent is taken as a standard, the detection probability is basically the same as that of the ASPeCT method, and is about 1dB better than that of the BPSK-L IKE method and about 0.5dB better than that of the method before the modulo addition of CSSPeCT.
The present invention algorithm compares with the method before the modular addition of the present invention, the traditional ASPECT, BPSK-L IKE acquisition method, as shown in FIG. 7. simulation results show that the CSSPeCT method is clearly superior to the CSSPeCT method before the modular addition, the ASPECT and BPSK-L IKE methods, in terms of main peak span, the CSSPeCT method has a main peak span of 20 sample points (half chip width) and is superior to the method before the modular addition and the ASPECT method, and is superior to the BPSK-L IKE method (80 sample points, 2 chip widths), and in terms of peak value, it is also significantly superior to the CSSPeCT method before the modular addition and the ASPECT method, and is 10% higher than the BPSK-L method, the method before the modular addition and the ASPECT method are worth noting that the CSSPeCT method completely eliminates the effect of secondary peaks, and the two smaller secondary peaks before the modular addition of the ASPECT method and the CSeCT method are superior to the final peak-taking method, and the comparison method is superior to the final peak-taking a new peak-average comparison method, which can be seen that the three different from the CSeCT method is superior to the final peak-averaged comparison method.
According to the above embodiment, the present invention further provides a correlation shift BOC (n, n) -based unambiguous capturing apparatus, including: the device comprises a signal receiving module, a signal splitting module, an integrating module, an inverting module, a detection quantity acquiring module I, a detection quantity acquiring module II, a comparing module and a positioning module.
Specifically, the signal receiving module is configured to obtain a digital intermediate frequency BOC signal of discrete time, and mix the digital intermediate frequency BOC signal with a local carrier by using a quadrature demodulation method, respectively, to obtain two paths of signals, I and Q, which are in-phase and quadrature.
In this embodiment, the signal receiving module includes:
the receiving module is suitable for receiving a satellite BOC signal; the down-conversion module is used for carrying out frequency conversion on the BOC signal to generate an intermediate frequency signal; the analog-to-digital converter is used for converting the intermediate frequency signal into a digital intermediate frequency BOC signal of discrete time; and the frequency mixing module is used for mixing the digital intermediate frequency BOC signal with a local carrier by adopting a quadrature demodulation method to obtain an in-phase I signal and a quadrature Q signal.
Specifically, the digital intermediate frequency signal after down-conversion may be expressed as:
Figure GDA0002447740080000081
PSis the power of the input signal, C (t) is the PRN code, D (t) is the navigation data, τ is the code delay of the input signal, fDIs the Doppler frequency, f, of the input signalIFIs the intermediate frequency, Sc (t) is the subcarrier, and n (t) is the noise term.
The input signal is mixed with local carrier to obtain inphase I and orthogonal Q signals as shown in the following
I(t)＝S(t)[cos[2π(fIF+fD)t]+cos[2π(fIF+fD)Ts]]+n(t)
Q(t)＝S(t)[cos[2π(fIF+fD)t]+cos[2π(fIF+fD)Ts]]+n(t)。
The signal splitting module is used for splitting a local BOC signal obtained by modulating a subcarrier by a local PRN sequence into an odd branch signal and an even branch signal which are respectively marked as CO(t) and CE(t)。
The method comprises the steps of modulating a subcarrier by a local PRN sequence to obtain a BOC code, equally dividing each chip of a local BOC signal, sequentially intercepting the chip information of the front half or the rear half of each pseudo-random code chip, splitting the chip information into odd and even branch signals, and recording the odd and even branch signals as CO(t) and CE(t)。
Mathematical model of local PRN sequence:
Figure GDA0002447740080000082
in the formula:
Figure GDA0002447740080000083
is a period of TCAmplitude of 1 rectangular pulse, TCIs one chip wide in width,Ciis a symbol of a chip, Ci∈ (-1, 1.) the local subcarrier is mathematically represented as:
Figure GDA0002447740080000084
Figure GDA0002447740080000091
is a period of TscThe amplitude of the rectangular pulse of (1), i.e., the width of one subcarrier pulse. djIs the pulse symbol of the subcarrier and M is the total number of pulses within one PRN chip. For BOC (1,1) signal, dj∈(-1,1)，
Figure GDA0002447740080000092
And M is 2. Using the two mathematical models described above, a local BOC (n, n) baseband sequence is generated:
Figure GDA0002447740080000093
fig. 2(a) illustrates the generation of the local BOC (1,1) baseband sequence, which can generate local CBOC (6,1,1/11) and TMBOC (6,1,4/33) baseband sequences, as shown in fig. 2(b) and 2 (c). Since the subcarriers are strictly synchronized with the PRN code sequences, the above equation can be simplified as:
Figure GDA0002447740080000094
and taking the length of each PRN chip as a reference, cutting the PRN chip into two equal parts according to the pulse duration of the subcarrier, wherein the front half part and the rear half part are reset to zero to form an odd branch BOC signal, and the front half part is zero and the rear half part is added to form a BOC even branch signal. CO(t) represents the odd branch portion, CE(t) represents an even branch portion.
Figure GDA0002447740080000095
Figure GDA0002447740080000096
NcIs the number of PRN chips in a period of time, doFor the sub-carrier pulse symbol corresponding to the first half chip based on the length of each PRN chip, dEIs a subcarrier pulse symbol corresponding to the second half chip based on the length of each PRN chip, and do&dE∈dj。
FIG. 3 is a schematic diagram of the generation of the local BOC (1,1) parity branch signal.
The integral module is used for taking the modulus of the complex signal I + jQ after the carrier stripping, and the modulus result and the odd branch signal CO(t) multiplying by each other, and integrating to obtain
Figure GDA0002447740080000097
Specifically, the complex signal I + jQ after carrier stripping is subjected to modulus taking, and two unit signals C obtained by splitting the complex signal I + jQ and the local BOC signal are obtainedO(t) or CEMultiplying one of (t) by each other, and integrating to obtain
Figure GDA0002447740080000098
And
Figure GDA0002447740080000099
Figure GDA00024477400800000910
Figure GDA00024477400800000911
in the formula, Ro(τ) is the correlation function of the odd-path signal and the received signal, RE(τ) is the correlation function of the even signal and the received signal.
The negation module is used for negating
Figure GDA0002447740080000101
Hysteresis
Figure GDA0002447740080000102
The number of sampling points is obtained by negation
Figure GDA0002447740080000103
T of itCIs the width of one chip;
specifically, for
Figure GDA0002447740080000104
Hysteresis
Figure GDA0002447740080000105
The number of sampling points is obtained by negation
Figure GDA0002447740080000106
(or to
Figure GDA0002447740080000107
Advance in
Figure GDA0002447740080000108
The number of sampling points is obtained by negation
Figure GDA0002447740080000109
) Here calculated
Figure GDA00024477400800001010
The detection amount acquisition module I is used for acquiring the detection amount
Figure GDA00024477400800001011
And
Figure GDA00024477400800001012
multiplying to obtain the detected quantity S with side peakOE。
Specifically, the integration result is
Figure GDA00024477400800001013
And
Figure GDA00024477400800001014
multiplying to obtain the detected amount with side peak as SOE。
Figure GDA00024477400800001015
And
Figure GDA00024477400800001016
can be simplified as follows:
Figure GDA00024477400800001017
Figure GDA00024477400800001018
SEis that
Figure GDA00024477400800001019
Signal part of, SOIs that
Figure GDA00024477400800001020
The signal portion of (a), the multiplication of the two forms giving SOE
SOE＝[SE(Δτ,ΔfD)+NE]×[SO(Δτ,ΔfD)+NO]
＝SE(Δτ,ΔfD)×SO(Δτ,ΔfD)+
SE(Δτ,ΔfD)×NO+
SO(Δτ,ΔfD)×NE+
NE×NO
The detection amount acquisition module II is used for comparing SOEModulus is taken to obtain | SOEI, then SOEAnd | SOEAnd | adding to obtain a detection quantity V without blurring.
Specifically, according to the reconstruction rule pair SOETaking a model to obtain | SOEI, then SOEAnd | SOEAdd | to get unambiguous detectionThe amount is denoted V.
V＝(|SOE|)+(SOE)
Fig. 4(a), 4(b), and 4(c) are schematic diagrams of reconstruction of the parity correlation functions of BOC (1,1), CBOC (6,1,1/11), and TMBOC (6,1,4/33), respectively.
And the comparison module is used for comparing the detection quantity V with a detection threshold value set by the decision device, and if the detection value exceeds the detection threshold value, the signal is considered to be accurately captured, so that the conclusion whether the satellite signal required by positioning exists in the received intermediate frequency input signal is obtained. If the detection value does not exceed the detection threshold, the signal is deemed to have not been accurately captured.
And the positioning module is used for continuously and normally receiving the satellite signals through the GNSS receiver when the satellite signals required for positioning are found to exist, so as to obtain the navigation message and realize positioning.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (7)

1. A correlation-shifted BOC (n, n) -based unambiguous acquisition method, characterized in that it comprises the following steps:
the method comprises the following steps: acquiring a digital intermediate frequency BOC signal of discrete time, and mixing the digital intermediate frequency BOC signal with a local carrier by adopting a quadrature demodulation method respectively to obtain an in-phase I signal and a quadrature Q signal;
step two: the local PRN sequence modulates subcarrier to obtain local BOC signal, and the local BOC signal is split into odd and even branch signals, which are marked as CO(t) and CE(t)；
Step three: carrying out modulus taking on the complex signal I + jQ after carrier stripping, and obtaining the modulus result and the odd branch signal CO(t) multiplying by each other, and integrating to obtain
Figure FDA0002447740070000011
Step four: to pair
Figure FDA0002447740070000012
Hysteresis
Figure FDA0002447740070000013
The number of sampling points is obtained by negation
Figure FDA0002447740070000014
T of itCIs the width of one chip;
step five: will be provided with
Figure FDA0002447740070000015
And
Figure FDA0002447740070000016
multiplying to obtain the detected quantity S with side peakOE；
Step six: to SOEModulus is taken to obtain | SOEI, then SOEAnd | SOEAdding | to obtain a detection quantity V without ambiguity;
step seven: comparing the detection quantity V with a detection threshold value set by a decision device, and if the detection value exceeds the detection threshold value, considering that the signal is accurately captured; if the detection value does not exceed the detection threshold value, the signal is not accurately captured, and the steps from one step to six are repeated.
2. The correlation-shifted BOC (n, n) -based unambiguous acquisition method according to claim 1, further comprising the steps of: when the satellite signal required for positioning is found to exist, the GNSS receiver continues to normally receive the satellite signal to obtain a navigation message, and positioning is realized; if the required satellite signal is not found, the satellite is replaced, and the steps from one step to seven are repeated.
3. The correlation shift BOC (n, n) -based ambiguity-free acquisition method according to claim 1, wherein the method for acquiring the digital intermediate frequency BOC signal of discrete time comprises:
receiving satellite BOC signals;
the BOC signal is subjected to down-conversion to generate an intermediate frequency signal, and the intermediate frequency signal is subjected to digital-to-analog conversion to a discrete-time digital intermediate frequency BOC signal.
4. The correlation-shift-based BOC (n, n) -based ambiguity-free acquisition method according to claim 1, wherein the second step is specifically: the local PRN sequence modulates subcarrier to obtain BOC code, divides each chip of local BOC signal equally, cuts out the chip information of the first half or the second half of each pseudo-random code chip in turn, splits into odd and even two branch signals, and marks them as CO(t) and CE(t)。
5. An ambiguity-free correlation-shift-based BOC (n, n) acquisition apparatus, comprising:
the signal receiving module is used for acquiring digital intermediate frequency BOC signals of discrete time, and mixing the digital intermediate frequency BOC signals with local carrier waves by adopting a quadrature demodulation method respectively to obtain in-phase I and quadrature Q signals;
a signal splitting module, configured to split a local BOC signal obtained by modulating a subcarrier with a local PRN sequence into an odd branch signal and an even branch signal, which are respectively denoted as CO(t) and CE(t)；
An integration module for taking the modulus of the complex signal I + jQ after the carrier stripping, the modulus result and the odd branch signal CO(t) multiplying by each other, and integrating to obtain
Figure FDA0002447740070000021
Negation module for pairing
Figure FDA0002447740070000022
Hysteresis
Figure FDA0002447740070000023
The number of sampling points is obtained by negation
Figure FDA0002447740070000024
T of itCIs the width of one chip;
a detection amount acquisition module I for connecting
Figure FDA0002447740070000025
And
Figure FDA0002447740070000026
multiplying to obtain the detected quantity S with side peakOE；
A detection amount acquisition module II for comparing SOEModulus is taken to obtain | SOEI, then SOEAnd | SOEAdding | to obtain a detection quantity V without ambiguity;
the comparison module is used for comparing the detection quantity V with a detection threshold value set by the decision device, and if the detection value exceeds the detection threshold value, the signal is considered to be accurately captured; if the detection value does not exceed the detection threshold, the signal is deemed to have not been accurately captured.
6. The correlation-shift-based BOC (n, n) -based unambiguous acquisition apparatus according to claim 5, wherein the apparatus further comprises a positioning module, configured to continue normal reception of satellite signals via the GNSS receiver when satellite signals required for positioning are found to exist, to obtain navigation messages, and to implement positioning.
7. The correlation-shifted BOC (n, n) -based unambiguous acquisition apparatus according to claim 5, wherein the signal receiving module comprises:
the receiving module is suitable for receiving a satellite BOC signal;
the down-conversion module is used for carrying out frequency conversion on the BOC signal to generate an intermediate frequency signal;
the analog-to-digital converter is used for converting the intermediate frequency signal into a digital intermediate frequency BOC signal of discrete time;
and the frequency mixing module is used for mixing the digital intermediate frequency BOC signal with a local carrier by adopting a quadrature demodulation method to obtain an in-phase I signal and a quadrature Q signal.
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