CN115061165A - Navigation spread spectrum signal capturing method and system based on low-loss down-sampling strategy - Google Patents
Navigation spread spectrum signal capturing method and system based on low-loss down-sampling strategy Download PDFInfo
- Publication number
- CN115061165A CN115061165A CN202210990540.3A CN202210990540A CN115061165A CN 115061165 A CN115061165 A CN 115061165A CN 202210990540 A CN202210990540 A CN 202210990540A CN 115061165 A CN115061165 A CN 115061165A
- Authority
- CN
- China
- Prior art keywords
- signal
- sampling
- frequency
- low
- sequence
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000005070 sampling Methods 0.000 title claims abstract description 94
- 238000000034 method Methods 0.000 title claims abstract description 55
- 238000001228 spectrum Methods 0.000 title claims abstract description 30
- 238000001514 detection method Methods 0.000 claims abstract description 12
- 238000007781 pre-processing Methods 0.000 claims description 41
- 108010076504 Protein Sorting Signals Proteins 0.000 claims description 24
- 230000001427 coherent effect Effects 0.000 claims description 15
- 238000012545 processing Methods 0.000 claims description 15
- 239000011159 matrix material Substances 0.000 claims description 8
- 238000001914 filtration Methods 0.000 claims description 7
- 230000010354 integration Effects 0.000 claims description 7
- 230000021615 conjugation Effects 0.000 claims description 3
- 238000010606 normalization Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 14
- 238000005516 engineering process Methods 0.000 abstract description 5
- 230000006870 function Effects 0.000 description 21
- 230000003595 spectral effect Effects 0.000 description 5
- 238000004422 calculation algorithm Methods 0.000 description 4
- 238000005314 correlation function Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000001360 synchronised effect Effects 0.000 description 2
- 241000287196 Asthenes Species 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- 241000764238 Isis Species 0.000 description 1
- 230000003416 augmentation Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004590 computer program Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Images
Classifications
-
- 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
- G01S19/243—Demodulation of navigation message
-
- 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
-
- 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
- G01S19/35—Constructional details or hardware or software details of the signal processing chain
- G01S19/37—Hardware or software details of the signal processing chain
Landscapes
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Signal Processing (AREA)
- Position Fixing By Use Of Radio Waves (AREA)
Abstract
The application relates to a navigation spread spectrum signal capturing method and system based on a low-loss down-sampling strategy. The method introduces a minimum loss strategy to preprocess the signal before the down-sampling on the basis that the down-sampling can improve the capturing speed and reduce the loss of the peak signal-to-noise ratio caused by the down-sampling process when the traditional down-sampling capturing method focuses more on improving the capturing speed and meets the bottleneck of improving the capturing probability, thereby obviously improving the capturing probability of the navigation spread spectrum signal under the condition of keeping the advantages of the down-sampling technology. Therefore, the technical scheme of the invention is superior to the traditional downsampling capture method in terms of capture speed and detection probability.
Description
Technical Field
The present application relates to the field of signal processing technologies, and in particular, to a method and a system for acquiring a navigation spread spectrum signal based on a low-loss down-sampling strategy.
Background
The navigation spread spectrum signal receiving system is composed of a radio frequency front end, a baseband signal processing module and an information resolving module, and each module respectively executes the functions of intermediate frequency digitization, capturing and tracking and text interpretation. The signal capture is the key technology of baseband signal processing in a navigation spread spectrum signal receiving system, and aims to estimate carrier Doppler frequency shift and pseudo code phase delay of a received signal in a limited precision range by using the shortest possible time and high capture probability and ensure the smooth operation of a signal receiving process. Compared with a general direct sequence spread spectrum signal, the system for navigating the spread spectrum signal is more complex, has more precise functions and more extensive signal service, so the development potential is better, and particularly under the condition that the current satellite navigation new modes such as low-orbit satellite augmentation and the like are concerned. However, the design requirement of the signal on the capture algorithm is higher, the complexity of the whole system and the vulnerability of the signal make the processing of the capture module more difficult, the consumed time is correspondingly increased, and the improvement of the capture probability also meets the bottleneck. Therefore, it has been a research focus in the industry to achieve fast and effective acquisition of navigation signals.
At present, the main idea of using a down-sampling method to solve the problem of fast acquisition of navigation spread spectrum signals is that the following three fast acquisition algorithms based on down-sampling are mainly used: coherent downsampling, mean downsampling, and time-frequency combination. The three methods are all that the strong correlation of the pseudo code is utilized to carry out operations such as folding and averaging on the signal in the time domain so as to achieve the effect equivalent to frequency down-sampling, thereby reducing the signal processing scale and greatly improving the capture speed. However, such a down-sampling strategy damages the strong coherent property of the pseudo code, introduces coherent noise, and causes loss of the peak signal-to-noise ratio of the captured result, resulting in a decrease in the capture probability, and such negative effects increase with an increase in the down-sampling degree, which further increases the computational difficulty in the subsequent de-blurring process, and on the contrary, reduces the capture efficiency. Therefore, finding a low-loss down-sampling strategy is a breakthrough in the face of the low peak signal-to-noise ratio dilemma of current acquisition schemes.
Disclosure of Invention
In view of the foregoing, it is desirable to provide a method and a system for acquiring a pilot spread spectrum signal based on a low-loss down-sampling strategy.
A method for acquiring a navigation spread spectrum signal based on a low-loss down-sampling strategy, the method comprising:
acquiring an intermediate frequency digital receiving signal according to a preset down-sampling parameter, and generating a local pseudo code sequence and a local carrier signal sequence;
demodulating and filtering according to the intermediate frequency digital receiving signal and the local carrier signal sequence to obtain a low-frequency signal of a difference frequency part;
constructing a preprocessing function which enables the loss of the signal peak signal-to-noise ratio to be minimum according to preset down-sampling parameters, and processing the low-frequency signal according to the preprocessing function to obtain a preprocessed signal;
sequentially performing down-sampling, FFT operation, de-spreading, IFFT operation and non-coherent integration operation on the preprocessed signals to obtain captured signals;
and obtaining a navigation spread spectrum signal acquisition result based on the threshold detection result of the acquisition signal and the local carrier signal sequence.
In one embodiment, the method further comprises the following steps: according to the preset down-sampling parameter, the acquisition duration isTSuccessive intervals beingT s Normalized angular frequency of
Intermediate frequency digital receiving signal ofr(n) (ii) a Wherein, presetting the down-sampling parameters comprises: down sampling factor value
Number of Doppler search channelsMAnd the number of FFT points before coherent integrationL，
，f p Representing intermediate frequency digital received signalsr(n) The known pseudo-code rate of the code,
and
respectively representing the known intermediate frequency angular frequency and the unknown doppler angular frequency after normalization.
In one embodiment, the method further comprises the following steps: according to the duration ofTAnd local pseudo-code of
The time interval of sampling the local pseudo code to generate the length of
Local pseudo-code reference sequence ofp(n) And referencing the local pseudo-code with a sequencep(n) Performing FFT and then taking conjugation to obtain a de-spread reference signal; in the carrier Doppler shift range of
Doppler search is stepped to
Taking a duration ofTAt sampling intervals ofT s And has a frequency of
Local carrier signal sequence ofc(n) Wherein
the carrier sequence number in the current state is indicated, and the initial value is 0.
In one embodiment, the method further comprises the following steps: receiving the intermediate frequency digital signalr(n) And local carrier sequencec(n) Multiplying to complete demodulation; and removing a sum frequency part in the demodulation result by using a low-pass filter and reserving a difference frequency part to obtain a low-frequency signal.
In one embodiment, the method further comprises the following steps: according to the preset down-sampling parameters, constructing a preprocessing function which enables the signal peak signal-to-noise ratio loss to be minimum as follows:
wherein,
a pre-processing function is represented as,
and
are all positive definite matrixes,
representing the vector of frequency components, superscript T representing the transpose of the matrix, operation
Representation matrix
And the feature vector corresponding to the minimum feature value.
In one embodiment, the method further comprises the following steps: and multiplying the preprocessing function and the low-frequency signal to obtain a preprocessed signal.
In one embodiment, the method further comprises the following steps: sampling the preprocessed signal to obtain a length ofN/αDown-sampled signal.
In one embodiment, the method further comprises the following steps: and multiplying the down-sampling signal and the de-spread reference signal to obtain an acquisition signal.
A navigation spread spectrum signal acquisition system based on a low loss down-sampling strategy, the system comprising:
the initial data acquisition module is used for acquiring an intermediate frequency digital receiving signal according to a preset down-sampling parameter and generating a local pseudo code sequence and a local carrier signal sequence;
the demodulation module is used for demodulating and filtering according to the intermediate frequency digital receiving signal and the local carrier signal sequence to obtain a low-frequency signal of a difference frequency part;
the preprocessing module is used for constructing a preprocessing function which enables the loss of the signal peak signal-to-noise ratio to be minimum according to a preset down-sampling parameter, and processing the low-frequency signal according to the preprocessing function to obtain a preprocessed signal;
the acquisition module is used for sequentially carrying out down-sampling, FFT operation, de-spreading, IFFT operation and non-coherent integration operation on the preprocessed signals to obtain acquisition signals; and obtaining a navigation spread spectrum signal acquisition result based on the threshold detection result of the acquisition signal and the local carrier signal sequence.
According to the navigation spread spectrum signal capturing method and system based on the low-loss down-sampling strategy, the traditional down-sampling capturing method is more focused on improving the capturing speed, and when a bottleneck is met in the aspect of improving the capturing probability, the method introduces the minimum loss strategy to preprocess the signal before down-sampling on the basis that the capturing speed can be improved through down-sampling, so that the peak signal-to-noise ratio loss caused in the down-sampling process is reduced, and the capturing probability of the navigation spread spectrum signal is obviously improved under the condition that the advantages of the down-sampling technology are reserved. Therefore, the technical scheme of the invention is superior to the traditional downsampling capture method in terms of capture speed and detection probability.
Drawings
Fig. 1 is a flowchart illustrating a navigation spread spectrum signal acquisition method based on a low-loss down-sampling strategy according to an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In one embodiment, as shown in fig. 1, there is provided a navigation spread spectrum signal acquisition method based on a low-loss down-sampling strategy, including the following steps:
and 102, acquiring an intermediate frequency digital receiving signal according to a preset down-sampling parameter, and generating a local pseudo code sequence and a local carrier signal sequence.
In this step, the down-sampling factor value is set with reference to the actual acquisition condition requirementsαNumber of Doppler search channelsMAnd the number of Fast Fourier Transform (FFT) points before coherent integrationL。
In the capturing process, the local pseudo code sequence after the down sampling and conjugate FFT conversion is stored in advance, so that the unnecessary calculation amount is prevented from being increased due to repeated generation.
And 104, demodulating and filtering according to the intermediate frequency digital receiving signal and the local carrier signal sequence to obtain a low-frequency signal of a difference frequency part.
And 106, constructing a preprocessing function which enables the signal peak signal-to-noise ratio loss to be minimum according to the preset down-sampling parameters, and processing the low-frequency signal according to the preprocessing function to obtain a preprocessed signal.
And step 108, performing down-sampling, FFT operation, de-spreading, IFFT operation and non-coherent integration operation on the preprocessed signals in sequence to obtain captured signals.
And step 110, acquiring a navigation spread spectrum signal acquisition result based on the threshold detection result of the acquisition signal and the local carrier signal sequence.
In the navigation spread spectrum signal capturing method based on the low-loss down-sampling strategy, the traditional down-sampling capturing method focuses more on improving the capturing speed, and when a bottleneck is met in improving the capturing probability, the method introduces the minimum loss strategy to preprocess the signal before down-sampling on the basis that the capturing speed can be improved by down-sampling, so that the peak signal-to-noise ratio loss caused in the down-sampling process is reduced, and the capturing probability of the navigation spread spectrum signal is obviously improved under the condition of keeping the advantages of the down-sampling technology. Therefore, the technical scheme of the invention is superior to the traditional downsampling capture method in terms of capture speed and detection probability.
In one embodiment, the acquisition duration is according to the preset down-sampling parameterTAt successive intervals ofT s Normalized angular frequency of
Intermediate frequency digital receiving signal ofr(n) (ii) a Wherein, presetting the down-sampling parameters comprises: down sampling factor valueαNumber of Doppler search channelsMAnd the number of FFT points before coherent integrationL，
，f p Representing intermediate frequency digital received signalsr(n) The known pseudo-code rate of the code,
and
respectively representing the known intermediate frequency angular frequency and the unknown doppler angular frequency after normalization. Since the carrier doppler and code phase delay of the incoming signal are unknown, they are first estimated by an acquisition process.
In one embodiment, the time duration isTAnd local pseudo code of
The time interval of sampling the local pseudo code to generate the length of
Local pseudo code reference sequence ofp(n) And referencing the local pseudo-code with a sequencep(n) Performing FFT and then taking conjugation to obtain a de-spread reference signal; in the carrier Doppler shift range of
Doppler search is stepped to
Taking a duration ofTAt sampling intervals ofT s And has a frequency of
Local carrier signal sequence ofc(n) Wherein
the carrier sequence number in the current state is represented, and the initial value is 0.
In another embodiment, the intermediate frequency is digitally receivedr(n) And local carrier sequencec(n) Multiplying to complete demodulation; and removing a sum frequency part in the demodulation result by using a low-pass filter and reserving a difference frequency part to obtain a low-frequency signal. The method comprises the following specific steps:
receiving signals by intermediate frequency digitalr(n) And local carrier sequencec(n) Multiplying, stripping carrier of received signal, utilizing low-pass filter to process and remove sum frequency portion and retain difference frequency portion, namely low-frequency signalx 1 (n) Memory for recordingx 1 (n)=s 1 (n)+w 1 (n). Wherein,s 1 (n) To representx 1 (n) At a medium frequency of
The signal components of (a) are,w 1 (n) Representsx 1 (n) Mean variance of
A white gaussian noise component.
In one embodiment, according to the preset down-sampling parameter, a preprocessing function that minimizes the loss of the signal-to-noise ratio of the peak value of the signal is constructed as follows:
wherein,
the pre-processing function is represented as,
and
are all positive definite matrixes,
representing the vector of frequency components, superscript T representing the transpose of the matrix, operation
Representation matrix
And the feature vector corresponding to the minimum feature value.
The specific form of the preprocessing function is given above, and the specific proving steps are as follows:
after the carrier wave of the stripped signal completes the demodulation process, the key step of low-loss down-sampling strategy capture is executed, namely, the low-frequency signal is capturedx 1 (n) And (4) carrying out pretreatment. Designing a preprocessing function
To pairx 1 (n) Operating to obtain an output sequencex 2 (n)，x 2 (n)=s 2 (n)+w 2 (n) Whereins 2 (n) To representx 2 (n) The signal components of (a) are,w 2 (n) Representsx 2 (n) The noise component (c) is specifically as follows.
Time domain expression of preprocessing functionh(n) Satisfy the requirement of
The conditions of (1). Its frequency domain response is
The expression can be obtained as follows.
For the output after pretreatmentx 2 (n) In other words, can be obtaineds 2 (n) Peak power gain ofQAnd average power of noise
As shown in the following formula. Wherein,
and
respectively represent
Cut-off frequency ofw 2 (n) Of the power spectral density of (c). Since the preprocessing process does not change the power of the noise component, the peak SNR gain of the preprocessing process can be obtained asQ。
After the preprocessing is finished, a down-sampling step is executed to obtain down-sampled outputx 3 (n). Specifically, the formula is shown as follows, wherein,s 3 (n) To representx 3 (n) The signal components of (a) are,w 3 (n) Representsx 3 (n) The noise component of (2).
For down-sampled outputx 3 (n) In other words, the signal components 3 (n) Is extended in phaseαMultiple, but unchanged in amplitude, so the peak power of the signal component is unchanged. But for noise componentsw 3 (n) The correlation function before and after down-sampling can be obtained
And
in a relationship of
. According to the relation between the correlation function and the power spectral density, the correlation function is obtainedw 3 (n) Power spectral density of
Which indicates that the noise power spectral density is averaged and spread after down-sampling. Therefore, the average power of the noise component after down-sampling can be obtained
As shown in the following formula.
After the down-sampling step is completed, thex 3 (n) ExecuteLOutputting result after FFT operation of point
Wherein, in the process,
to represent
A medium peak power ofL 2 QThe signal components of (a) are,
represents
The noise component of (2). Let us firstkThe noise component of each Doppler search channel is
Then, then
Wherein
. The obtainable power spectral density and average power are shown in the following formulas,
to be simple and convenient, order
Obtained by
The power of (c) is shown in the following formula.
For FFT output results
In other words, the peak signal-to-noise ratio can be obtainedPSNR 1 As shown in the following formula.
If there is no preprocessing and down-sampling step, directly comparing the signalsx 1 (n) By performing FFT operation, the peak SNR in this case can be obtainedPSNR 2 As shown in the following formula.
To implement a low loss strategy, a loss function is defined as shown below, which indicates that the preprocessing function is critical to achieving minimum loss.
Input signal due to preprocessing functionx 1 (n) Is a low frequency signal, so it can be regarded as a strict linear phase low pass filter whose impulse response satisfies the conditionh(n) = h(N-1-n). Since the number of sampling points is generally an even number, the preprocessing function can be expressed as follows. Wherein,
and is andU(n)=2h(N/2-n) A coefficient vector representing a frequency component;
and represents a frequency component vector.
As shown in the formula, the minimum loss strategy is realized by finding the optimal coefficient vectorU. For convenience, the following symbols are given as shown below. Wherein,
and
are all positive definite matrices.
From the above, the loss function can be represented by the following equation.
The above formula can be rewritten as
Then, the two sides are derived to obtain the following formula.
In the formula,
. It is obvious that
And is
Is equal to
Can obtain the minimum feature value
The value is obtained. Provision for
To obtain the operator of the eigenvector corresponding to the minimum eigenvalue, the optimal vector satisfying the minimum loss condition can be obtained as shown in the following formula.
Thus, the preprocessing function that can implement the minimum loss strategy is shown below.
In obtaining a signal
Then, de-spread, IFFT and non-coherent integration operations are performed to obtain the acquisition resultz(n) Specifically, the following formula is shown.
Finally, find the sequencez(n) The maximum value is compared with the detection threshold, if the maximum value exceeds the detection threshold, the position corresponding to the abscissa thereof is the code phase delay, and the central frequency corresponding to the local carrier in the current state is the same as the central frequency corresponding to the local carrier in the current state
The difference is the carrier Doppler shift; if not, returning to the local carrier generation stage, namely the carrier sequence numbering
Adding 1 to regenerate the local carrier wave, and repeatedly executing the subsequent steps until the detection exceeds the threshold.
In a specific embodiment, in a baseband processing link of a navigation spread spectrum signal receiving system, a spreading pseudo code rate of an input signal is assumed to be 1.023MHz, an intermediate frequency is assumed to be 30.69MHz, pseudo code phase delay is random, and a carrier Doppler dynamic range is between-2.5 kHz and 2.5 kHz. And taking an intermediate frequency digital signal sequence with the duration of 20ms and the input signal-to-noise ratio of-20 dB, and estimating the pseudo code phase delay and the carrier Doppler frequency shift of the signal by a baseband processing module by adopting a capture algorithm of a low-loss down-sampling strategy.
The sampling rate is 75MHz, the coherent time length T is 2ms, Doppler search stepping is 100Hz, the number of Doppler search channels is 10, and the selected down-sampling factor is 10, the signal is captured by the method provided by the invention, the finally obtained pseudo code estimation error is less than 400 nanoseconds, the Doppler estimation error is less than 100Hz, the signal is in the capture error tolerance range, the capture speed is improved by 45% compared with the traditional down-sampling capture algorithm, and the capture probability is improved by 9%. Therefore, the method provided by the invention can realize the improvement of the acquisition performance of the navigation spread spectrum signal.
It should be understood that, although the steps in the flowchart of fig. 1 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least a portion of the steps in fig. 1 may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performance of the sub-steps or stages is not necessarily sequential, but may be performed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.
In one embodiment, a navigation spread spectrum signal acquisition system based on a low-loss down-sampling strategy is provided, which includes:
the initial data acquisition module is used for acquiring an intermediate frequency digital receiving signal according to a preset down-sampling parameter and generating a local pseudo code sequence and a local carrier signal sequence;
the demodulation module is used for demodulating and filtering according to the intermediate frequency digital receiving signal and the local carrier signal sequence to obtain a low-frequency signal of a difference frequency part;
the preprocessing module is used for constructing a preprocessing function which enables the loss of the signal peak signal-to-noise ratio to be minimum according to a preset down-sampling parameter, and processing the low-frequency signal according to the preprocessing function to obtain a preprocessed signal;
the acquisition module is used for sequentially carrying out down-sampling, FFT operation, de-spreading, IFFT operation and non-coherent integration operation on the preprocessed signals to obtain acquisition signals; and obtaining a navigation spread spectrum signal acquisition result based on the threshold detection result of the acquisition signal and the local carrier signal sequence.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include non-volatile and/or volatile memory. Non-volatile memory can include read-only memory (ROM), Programmable ROM (PROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchronous Link DRAM (SLDRAM), Rambus Direct RAM (RDRAM), direct bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
All possible combinations of the technical features in the above embodiments may not be described for the sake of brevity, but should be considered as being within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (7)
1. A method for acquiring a navigation spread spectrum signal based on a low-loss down-sampling strategy, the method comprising:
acquiring an intermediate frequency digital receiving signal according to a preset down-sampling parameter, and generating a local pseudo code sequence and a local carrier signal sequence;
demodulating and filtering according to the intermediate frequency digital receiving signal and the local carrier signal sequence to obtain a low-frequency signal of a difference frequency part;
constructing a preprocessing function which enables the loss of the signal peak signal-to-noise ratio to be minimum according to preset down-sampling parameters, and processing the low-frequency signal according to the preprocessing function to obtain a preprocessed signal;
sequentially performing down-sampling, FFT operation, de-spreading, IFFT operation and non-coherent integration operation on the preprocessed signals to obtain captured signals;
obtaining a navigation spread spectrum signal capturing result based on the threshold detection result of the captured signal and the local carrier signal sequence;
the constructing of the preprocessing function which enables the loss of the signal-to-noise ratio of the signal peak value to be minimum according to the preset down-sampling parameters comprises the following steps:
according to the preset down-sampling parameters, constructing a preprocessing function which enables the signal peak signal-to-noise ratio loss to be minimum as follows:
wherein,
a pre-processing function is represented as,
and
are all positive definite matrixes,
representing the frequency component vector, superscript T representing the transpose of the matrix, M representing the number of Doppler search channels, and operation
Representation matrix
The characteristic vector corresponding to the minimum characteristic value;
processing the low-frequency signal according to the preprocessing function to obtain a preprocessed signal, including:
and multiplying the preprocessing function and the low-frequency signal to obtain a preprocessed signal.
2. The method of claim 1, wherein the obtaining the if digital received signal according to the preset down-sampling parameter comprises:
according to the preset down-sampling parameter, the acquisition duration isTAt successive intervals ofT s Normalized angular frequency of (
+
) Intermediate frequency digital receiving signal ofr(n) (ii) a Wherein, presetting the down-sampling parameters comprises: down sampling factor valueαNumber of Doppler search channelsMAnd the number of FFT points before coherent integrationL，
，f p Representing intermediate frequency digital received signalsr(n) The known pseudo-code rate of the code,
and
respectively representing the known intermediate frequency angular frequency and the unknown doppler angular frequency after normalization.
3. The method of claim 2, wherein generating the local pseudo-code sequence and the local carrier signal sequence comprises:
according to the duration ofTAnd local pseudo-code of
The time interval of sampling the local pseudo code to generate the length of
Local pseudo code reference sequence ofp(n) And referencing the local pseudo-code with a sequencep(n) Performing FFT and then taking conjugation to obtain a de-spread reference signal;
in the carrier Doppler shift range of
Doppler search is stepped to
Taking a duration ofTAt sampling intervals of
And has a frequency of
Local carrier signal sequence ofc(n)，Wherein,
the carrier sequence number in the current state is represented, and the initial value is 0.
4. The method of claim 3, wherein demodulating and filtering based on the intermediate frequency digital received signal and the local carrier signal sequence to obtain a low frequency signal of a difference frequency portion comprises:
receiving the intermediate frequency digital signalr(n) And local carrier sequencec(n) Multiplying to complete demodulation;
and removing a sum frequency part in the demodulation result by using a low-pass filter and reserving a difference frequency part to obtain a low-frequency signal.
5. The method of claim 1, wherein down-sampling the pre-processed signal comprises:
sampling the preprocessed signal to obtain a length ofN/αDown-sampled signal.
6. The method of claim 1, wherein despreading the pre-processed signal comprises:
and multiplying the down-sampling signal and the de-spread reference signal to obtain an acquisition signal.
7. A system for navigation spread spectrum signal acquisition based on a low loss down-sampling strategy, the system comprising:
the initial data acquisition module is used for acquiring an intermediate frequency digital receiving signal according to a preset down-sampling parameter and generating a local pseudo code sequence and a local carrier signal sequence;
the demodulation module is used for demodulating and filtering according to the intermediate frequency digital receiving signal and the local carrier signal sequence to obtain a low-frequency signal of a difference frequency part;
the preprocessing module is used for constructing a preprocessing function which enables the loss of the signal peak signal-to-noise ratio to be minimum according to a preset down-sampling parameter, and processing the low-frequency signal according to the preprocessing function to obtain a preprocessed signal;
the acquisition module is used for sequentially carrying out down-sampling, FFT operation, de-spreading, IFFT operation and non-coherent integration operation on the preprocessed signals to obtain acquisition signals; obtaining a navigation spread spectrum signal capturing result based on the threshold detection result of the captured signal and the local carrier signal sequence;
the constructing of the preprocessing function which enables the loss of the signal-to-noise ratio of the signal peak value to be minimum according to the preset down-sampling parameters comprises the following steps:
according to the preset down-sampling parameters, constructing a preprocessing function which enables the signal peak signal-to-noise ratio loss to be minimum as follows:
wherein,
the pre-processing function is represented as,
and
are all positive definite matrixes,
representing the vector of frequency components, superscript T representing the transpose of the matrix, M representing the number of Doppler search channels, and operation
Representation matrix
The characteristic vector corresponding to the minimum characteristic value;
processing the low-frequency signal according to the preprocessing function to obtain a preprocessed signal, including:
and multiplying the preprocessing function and the low-frequency signal to obtain a preprocessed signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210990540.3A CN115061165B (en) | 2022-08-18 | 2022-08-18 | Navigation spread spectrum signal capturing method and system based on low-loss down-sampling strategy |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210990540.3A CN115061165B (en) | 2022-08-18 | 2022-08-18 | Navigation spread spectrum signal capturing method and system based on low-loss down-sampling strategy |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN115061165A true CN115061165A (en) | 2022-09-16 |
| CN115061165B CN115061165B (en) | 2022-11-15 |
Family
ID=83207570
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210990540.3A Active CN115061165B (en) | 2022-08-18 | 2022-08-18 | Navigation spread spectrum signal capturing method and system based on low-loss down-sampling strategy |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115061165B (en) |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20070046536A1 (en) * | 2005-08-31 | 2007-03-01 | Zhike Jia | Fast fourier transform with down sampling based navigational satellite signal tracking |
| US20110200074A1 (en) * | 2008-10-29 | 2011-08-18 | Thales Alenia Space Italia S.P.A. | Method and system for spread spectrum signal acquisition |
| CN106788470A (en) * | 2016-11-25 | 2017-05-31 | 西安烽火电子科技有限责任公司 | High data rate bursts communication quick capturing method and device based on spread spectrum |
| CN110007322A (en) * | 2019-04-17 | 2019-07-12 | 南京航空航天大学 | Based on the Beidou B1I signal acquisition methods for being concerned with down-sampled |
| CN113328765A (en) * | 2021-04-25 | 2021-08-31 | 北京航空航天大学 | Method for realizing universal receiver of multiple spread spectrum systems under high dynamic condition |
| CN114690218A (en) * | 2022-03-23 | 2022-07-01 | 中国科学院国家空间科学中心 | Method for considering both GNSS reflected signal observation and GNSS direct signal capture |
-
2022
- 2022-08-18 CN CN202210990540.3A patent/CN115061165B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20070046536A1 (en) * | 2005-08-31 | 2007-03-01 | Zhike Jia | Fast fourier transform with down sampling based navigational satellite signal tracking |
| US20110200074A1 (en) * | 2008-10-29 | 2011-08-18 | Thales Alenia Space Italia S.P.A. | Method and system for spread spectrum signal acquisition |
| CN106788470A (en) * | 2016-11-25 | 2017-05-31 | 西安烽火电子科技有限责任公司 | High data rate bursts communication quick capturing method and device based on spread spectrum |
| CN110007322A (en) * | 2019-04-17 | 2019-07-12 | 南京航空航天大学 | Based on the Beidou B1I signal acquisition methods for being concerned with down-sampled |
| CN113328765A (en) * | 2021-04-25 | 2021-08-31 | 北京航空航天大学 | Method for realizing universal receiver of multiple spread spectrum systems under high dynamic condition |
| CN114690218A (en) * | 2022-03-23 | 2022-07-01 | 中国科学院国家空间科学中心 | Method for considering both GNSS reflected signal observation and GNSS direct signal capture |
Non-Patent Citations (5)
| Title |
|---|
| CHENGYAO TANG 等: "Fast acquisition method using modified PCA with a sparse factor for burst DS spread-spectrum transmission", 《SCIENCE DIRECT》 * |
| TAYLOR SIBBETT 等: "Novel Maximum-based Timing Acquisition for Spread-Spectrum Communications", 《IEEE XPLORE》 * |
| 刘春玲等: "一种基于FFT的弱信号快速捕获算法", 《计算机仿真》 * |
| 朱国富: "扩频体制低轨卫星通信信号捕获与跟踪系统设计", 《电讯技术》 * |
| 陈柳鹏 等: "一种高动态突发信号捕获方法研究", 《第十二届中国卫星导航年会论文集——S07卫星导航增强技术》 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN115061165B (en) | 2022-11-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP2808954B2 (en) | Unmodulated signal detection and frequency pull-in device | |
| CN101729461B (en) | System and method for eliminating single-frequency interference and multi-frequency interference | |
| CN102075484A (en) | Method and device for reducing peak-to-average power ratio of signal | |
| USH741H (en) | Discrete complex correlation device for obtaining subpixel accuracy | |
| CN113972929B (en) | Method for capturing spread spectrum signal under high dynamic Doppler | |
| Tamim et al. | Techniques for optimization in time delay estimation from cross correlation function | |
| CN114944974B (en) | Frequency offset estimation method and device and electronic equipment | |
| CN115980798A (en) | Fast unambiguous signal capture algorithm | |
| CN115061165B (en) | Navigation spread spectrum signal capturing method and system based on low-loss down-sampling strategy | |
| CN114285713A (en) | Low-orbit broadband satellite time frequency offset estimation method and system | |
| US7130342B2 (en) | Wireless receiver and method employing forward/backward recursive covariance based filter coefficient generation | |
| Mosavi et al. | A new method for continuous wave interference mitigation in single-frequency GPS receivers | |
| CN115378462B (en) | Method and system for capturing direct spread spectrum signal with large signal-to-noise ratio | |
| CN111245473B (en) | Down-sampling-serial FFT-based high-dynamic low-signal-to-noise-ratio signal coarse capturing method | |
| CN115469341A (en) | Rapid acquisition method for CL code of GPS L2C signal | |
| KR101991844B1 (en) | Apparatus and method for estimating time delay | |
| CN111641572A (en) | Noise power evaluation method and device and storage medium | |
| CN109361632B (en) | Parameter blind estimation method of multipath BOC signal based on spectrum correlation | |
| Tamim et al. | Hilbert transform of FFT pruned cross correlation function for optimization in time delay estimation | |
| CN109633707B (en) | Variable coefficient matched filtering rapid capturing method based on pre-averaging processing | |
| CN116962123B (en) | Raised cosine shaping filter bandwidth estimation method and system of software defined framework | |
| JP3630581B2 (en) | Spread modulation signal receiver | |
| CN102420635A (en) | Multipath search method and multipath searcher | |
| CN118174748B (en) | Low-complexity non-search first-order dynamic direct-spread signal capturing method | |
| CN117176518B (en) | Frequency offset estimation method, device, electronic equipment and storage medium |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |