CN114696869B - Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio - Google Patents

Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio Download PDF

Info

Publication number
CN114696869B
CN114696869B CN202210271885.3A CN202210271885A CN114696869B CN 114696869 B CN114696869 B CN 114696869B CN 202210271885 A CN202210271885 A CN 202210271885A CN 114696869 B CN114696869 B CN 114696869B
Authority
CN
China
Prior art keywords
signal
fft
beidou
capturing
count
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.)
Active
Application number
CN202210271885.3A
Other languages
Chinese (zh)
Other versions
CN114696869A (en
Inventor
梁熙民
李桓
杨錬
廖昌俊
朱贤省
刘阳
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Electronic Science and Technology of China
Original Assignee
University of Electronic Science and Technology of China
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by University of Electronic Science and Technology of China filed Critical University of Electronic Science and Technology of China
Priority to CN202210271885.3A priority Critical patent/CN114696869B/en
Publication of CN114696869A publication Critical patent/CN114696869A/en
Application granted granted Critical
Publication of CN114696869B publication Critical patent/CN114696869B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7075—Synchronisation aspects with code phase acquisition
    • 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

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The invention provides a Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio, which comprises the following steps of: i, Q obtained by multiplying intermediate frequency signal inputted by intermediate frequency signal with generated local carrier signalA way signal; FFT step: obtaining a baseband complex signal by using I, Q two paths of signals, respectively carrying out fast Fourier transform FFT operation on the baseband complex signal and a local pseudo code sequence, multiplying the baseband complex signal and the local pseudo code sequence, and then carrying out fast Fourier inverse transform on the multiplication result to obtain a sequence correlation value R (n); obtaining a maximum value R (R) and a maximum value occurrence position R from the sequence correlation value R (n); and a detection judgment step: r (R) and a preset judgment threshold are set as V t And comparing, when the capturing is successful, taking the current local carrier frequency as Doppler frequency shift of the captured Beidou No. three satellite RDSS service outbound signal, and taking the position R where R (R) appears as code phase of the captured Beidou No. three satellite RDSS service outbound signal. The invention has the characteristics of high capturing speed and less occupation of hardware resources.

Description

Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio
Technical Field
The invention relates to a satellite communication technology, in particular to a technology for capturing a Beidou No. three satellite RDSS service outbound signal.
Background
The Beidou No. three GEO satellite RDSS business outbound signal provides functional services such as positioning report, bidirectional timing, message communication and the like for users on the basis of completely reserving the Beidou No. two RDSS outbound signal. The civil signal of the RDSS service outbound signal of the new system comprises a pilot frequency branch S2C_p and a message branch S2C_d, and the two paths of signals are in UQPSK modulation relation.
The relative motion between the terrestrial receiver and the satellite causes the satellite signal to produce a doppler shift and a code phase shift, resulting in the carrier frequency and code phase of the terrestrial received signal not being coincident with the transmitted signal. In order to provide services for users, the terrestrial receiver needs to achieve reliable acquisition of satellite outbound signals (hereinafter referred to as target signals), i.e., preliminary estimation of carrier frequency offset and code phase offset, and eliminate the influence caused by relative motion. In the satellite signal receiving technology, the capturing result lays a foundation for subsequent tracking and demodulation, and capturing can be rapidly and accurately completed, so that the capturing is an important index of the performance of a receiver.
In order to obtain higher capturing probability, a multi-stay method can be adopted, namely, a multi-detection method is used for improving the overall capturing probability and reducing the false alarm probability. In the methods, the traditional M-taking detection method in N is simple in implementation mode, but has low capture probability when signal-to-noise conditions are poor, and the method has the problem of long residence time, so that the method is not beneficial to being applied to a system with high real-time requirements.
Disclosure of Invention
Aiming at the defects of an M detection method in N, the invention provides a Beidou No. three satellite RDSS service outbound signal capturing method under the condition of low signal-to-noise ratio.
The invention aims to solve the technical problems, and adopts the technical scheme that the method for capturing the Beidou No. three satellite RDSS service outbound signals under the condition of low signal-to-noise ratio comprises the steps of detecting and capturing input intermediate frequency signals by taking cells as units, dividing the intermediate frequency signals to be detected in each cell into N sections, and detecting and capturing the intermediate frequency signals of each cell according to the following steps:
and (3) a down-conversion step: multiplying the nth section intermediate frequency signal in the current cell with the generated local carrier signal, filtering out a high frequency part by a low-pass filtering module, and then enabling the obtained I, Q two paths of signals to enter an FFT step;
FFT step: obtaining a baseband complex signal s (n) by using I, Q two paths of signals, if the local pseudo code sequence is c ' (n), respectively performing fast Fourier transform FFT operation on the baseband complex signal s (n) and a time reversal sequence c ' (-n) of the local pseudo code sequence to obtain FFT (s (n)), and obtaining FFT (c ' (-n)), wherein c ' (-n) is a real sequence, and the FFT (c ' (-n)) is equivalent to FFT according to the property of Fourier transform * (c′(-n)), * Representing the conjugate. FFT (s (n)) and FFT * (c' (-n)) multiplying; finally, performing Inverse Fast Fourier Transform (IFFT) operation on the multiplication result to obtain a sequence correlation value R (n) of the local pseudo code and the baseband signal at each phase offset, where R (n) =ifft (FFT (s (n)). FFT * (c (-n)); spectral amplitudeA maximum value R (R) and a maximum value occurrence position R in the value R (n) enter a detection judgment step;
and a detection judgment step: r (R) and a preset judgment threshold are set as V t Comparing, for example, the current cell is greater than a preset decision threshold of V t If the R (R) count of the current cell reaches the successful judgment count, the acquisition is considered to be successful, if the R (R) count of the current cell is greater than the preset judgment threshold and is V t If the count of R (R) does not reach the successful judgment count and the search times do not reach N, updating n=n+1, and returning to the down-conversion step to continue the next search; if the current cell is greater than the preset decision threshold V t If the R (R) count does not reach the successful judgment count and the search times reach N, discarding the search of the current cell, adjusting the frequency of the generated local carrier wave, and carrying out the detection capture of the next cell; and when the capturing is successful, taking the current local carrier frequency as Doppler frequency shift of the captured Beidou No. three satellite RDSS service outbound signal, and taking the position R where R (R) appears as the code phase of the captured Beidou No. three satellite RDSS service outbound signal.
The invention has the advantages of being beneficial to improving the capturing probability of the Beidou No. three RDSS service outbound signals, and having the characteristics of high capturing speed and less occupation of hardware resources.
Drawings
FIG. 1 is a schematic diagram of a system;
FIG. 2 is a schematic diagram of a down conversion module;
FIG. 3 is a schematic diagram of an FFT module;
fig. 4 is a schematic diagram of a detection decision module.
Detailed Description
The system for realizing the method of the invention is shown in figure 1, and comprises a down-conversion module, a fast Fourier transform FFT module and a detection decision module.
The system detects the input intermediate frequency signals by taking the unit cells as units, and the intermediate frequency signals to be detected in each unit cell are divided into N sections. 1 segment of intermediate frequency signal is detected at a time.
The down-conversion module multiplies the input intermediate frequency signal by the local carrier signal, filters out the high frequency part through the low-pass filtering module, and then inputs the obtained I, Q two paths of signals to the next module.
The FFT module performs FFT operation on the input I, Q two paths of signals and the local pseudo code sequence, and then gives the product of the FFT operation (inverse FFT operation IFFT, and gives the maximum value of the IFFT result and the position where the maximum value appears to the detection decision module.
And the detection judgment module judges whether the capturing is finished or not according to the maximum value output by the FFT module and the position where the maximum value appears. If the acquisition is completed, outputting the acquired code phase and Doppler frequency shift to a subsequent tracking module, otherwise, searching again.
As shown in fig. 2, since the modulation relationship of the civil signal is UQPSK, the doppler shift and the code offset of the two signals are identical, and the intermediate frequency signal s' (n) of the satellite signal entering the acquisition module is defined as:
s′(n)＝d(n)c(n)cos(2πfnT s )
wherein d (n) is a data code carried by the signal, c (n) is a spread spectrum code, f is a carrier frequency of the intermediate frequency signal, T s Is the baseband data rate, N is the nth signal sequence, n=1, …, N.
Through a multiplier module, the local carrier signal is multiplied by the intermediate frequency signal after cos mapping and sin mapping, and then the high frequency component is filtered through a low-pass filter, so that signals i (n) and q (n) of I, Q are obtained:
i(n)＝d(n)c(n)cos(2πf d nT s )
q(n)＝d(n)c(n)sin(2πf d nT s )
wherein f d Representing the difference between the local carrier frequency signal and the intermediate frequency signal, i.e. the doppler shift. The resulting I, Q signal is passed to an FFT module for further processing.
The structure of the FFT module is shown in fig. 3, and includes an FFT computation module, an IFFT computation module, a local pseudo code generation module, a multiplier module, and a maximum signal selector. For convenience of deduction, the obtained I, Q two paths of signals are expressed as baseband complex signals through Euler formula:
if the local pseudocode sequence is defined as c '(n), there is a code phase offset of δ between c (n) and c' (n). Performing fast fourier transform FFT operation on the time-reversed sequences c '(-n) of the baseband complex signal s (n) and the local pseudo code sequence respectively to obtain FFT (s (n)), FFT (c' (-n)), wherein since c '(-n) is a real sequence, FFT (c' (-n)) is equivalent to FFT according to the nature of fourier transform * (c′(-n)), * Representing the conjugate.
Depending on the nature of the fourier transform, the signal frequency domain multiplication is equal to the time domain convolution, i.e
* Representing a time domain convolution operation. It can be seen that if the operation result of the multiplier is subjected to inverse Fourier transform, a time domain correlation function can be obtained
R(n)＝s(n)*c′(-n)＝IFFT(FFT(s(n))·FFT * (c(-n)))
The value of R (n) represents the magnitude of the local pseudocode summed in relation to the baseband signal at each phase offset. The maximum signal selector gives the maximum value module R (R) of the spectrum amplitude and the maximum amplitude occurrence position R as selection results to the detection decision module.
The detection decision module is shown in fig. 4, and comprises a threshold detection module and a decision module. If the calculation result of the ith detection after the down-conversion and FFT module is V i The decision threshold of the detection decision module is V t Defining a successful detection judgment value as A, a detection initial value as B, counting a variable K, initializing K as B, and searching for N as an upper limit, wherein A, B is an experience value selected according to environment and requirements, and the module comprises the following processing flow:
1. the maximum value of the spectrum amplitude is modulo V i Decision threshold V t Comparing, if V i >V t K is increased by 1, otherwise K is decreased by 1.
2. If K is greater than 0 but less than a, updating i=i+1, and obtainingCalculation result V through down-conversion and FFT module i Returning to the step 1 to continue searching the current signal; if K is equal to A, judging that the capturing is successful; if K is equal to 0, discarding the current cell search, adjusting the frequency of the local carrier generation module, and carrying out the next cell search.
3. If the search times are equal to N, the current cell search is abandoned and the next cell search is performed.
If the acquisition is successful, then the local carrier frequency at this point is the acquired doppler shift, and the acquired code phase is the maximum value modulus R (R) of the spectral amplitude and the maximum amplitude occurrence position R.

Claims (1)

1. The method for capturing the Beidou No. three satellite RDSS service outbound signal under the condition of low signal-to-noise ratio is characterized by comprising the steps of detecting and capturing an input intermediate frequency signal by taking a cell as a unit, dividing the intermediate frequency signal to be detected in each cell into N sections, and detecting and capturing the intermediate frequency signal of each cell according to the following steps:
and (3) a down-conversion step: multiplying the nth section intermediate frequency signal in the current cell with the generated local carrier signal, filtering out a high frequency part by a low-pass filtering module, and then enabling the obtained I, Q two paths of signals to enter an FFT step;
FFT step: obtaining a baseband complex signal s (n) by using I, Q two paths of signals, and if the local pseudo code sequence is c ′ (n) time-reversed sequence c of baseband complex signal s (n) and local pseudo code sequence ′ Respectively performing fast Fourier transform FFT operation to obtain FFT (s (n)), FFT (c) ′ (-n))，FFT * (c ′ (-n))＝FFT(c ′ (-n)), * The representation is conjugated and FFT (s (n)) is combined with the FFT * (c' (-n)) multiplying; finally, performing Inverse Fast Fourier Transform (IFFT) operation on the multiplication result to obtain a sequence correlation value R (n) of the local pseudo code and the baseband signal at each phase offset, where R (n) =ifft (FFT (s (n)). FFT * (c (-n)); a maximum value R (R) and a maximum value occurrence position R in the sequence correlation value R (n) enter a detection judgment step;
and a detection judgment step: will beR (R) is V with a preset judgment threshold t Comparing, for example, the current cell is greater than a preset decision threshold of V t If the R (R) count of the current cell reaches the successful judgment count, the acquisition is considered to be successful, if the R (R) count of the current cell is greater than the preset judgment threshold and is V t The R (R) count does not reach the successful judgment count and the searching times do not reach N, and the next searching is continued after the down-conversion step is returned; if the current cell is greater than the preset decision threshold V t If the R (R) count does not reach the successful judgment count and the search times reach N, discarding the search of the current cell, adjusting the frequency of the generated local carrier wave, and carrying out the detection capture of the next cell; and when the capturing is successful, taking the current local carrier frequency as Doppler frequency shift of the captured Beidou No. three satellite RDSS service outbound signal, and taking the position R where R (R) appears as the code phase of the captured Beidou No. three satellite RDSS service outbound signal.
CN202210271885.3A 2022-03-18 2022-03-18 Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio Active CN114696869B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210271885.3A CN114696869B (en) 2022-03-18 2022-03-18 Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210271885.3A CN114696869B (en) 2022-03-18 2022-03-18 Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio

Publications (2)

Publication Number Publication Date
CN114696869A CN114696869A (en) 2022-07-01
CN114696869B true CN114696869B (en) 2023-07-25

Family

ID=82138382

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210271885.3A Active CN114696869B (en) 2022-03-18 2022-03-18 Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio

Country Status (1)

Country Link
CN (1) CN114696869B (en)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102162852A (en) * 2010-12-07 2011-08-24 清华大学 Method and system for capturing weak GNSS (Global Navigation Satellite System) signal under condition of large-scale frequency deviation

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104360357A (en) * 2014-11-24 2015-02-18 四川九洲电器集团有限责任公司 Quick Beidou satellite signal capturing method and system based on circulation mode
CN106230475B (en) * 2016-07-06 2018-10-02 北京理工大学 One kind being based on Tong detectors pseudo-code Doppler effect correction catching method and device
CN112987046A (en) * 2019-12-13 2021-06-18 深圳开阳电子股份有限公司 Method and device for rapidly capturing satellite signals and computer storage medium

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102162852A (en) * 2010-12-07 2011-08-24 清华大学 Method and system for capturing weak GNSS (Global Navigation Satellite System) signal under condition of large-scale frequency deviation

Also Published As

Publication number Publication date
CN114696869A (en) 2022-07-01

Similar Documents

Publication Publication Date Title
CN106646546B (en) A kind of satellite-signal multidimensional quick capturing method and system
CN105162493A (en) Doppler domain and delay domain two-dimension acquiring method and device
CN109633711B (en) Ultra-large dynamic and high-sensitivity spread spectrum measurement and control baseband receiving method and device
CN109088838B (en) Pseudo code-Doppler fast capturing method of direct sequence spread spectrum DPSK signal under high dynamic condition
CN106879068B (en) Method for estimating arrival time of signal in strong multipath environment
CN105842713A (en) INS (Inertial Navigation System) assisted fast acquisition method for BDS (Beidou Navigation System) signals based on SFT (Sparse Fourier Transform)
CN105790788B (en) A kind of pseudo-code of direct expansion msk signal-Doppler's joint acquisition method
CN102520423A (en) Circuit for rapidly capturing long period pseudo random spread spectrum code of satellite navigation receiver and capturing method thereof
CN111935046B (en) Low-complexity frequency shift keying signal symbol rate estimation method
CN109586761B (en) Tracking demodulation method of high dynamic spread spectrum signal
CN111245476A (en) Low-orbit satellite deep spread spectrum low-complexity pseudo code capturing method
CN103344968B (en) INS auxiliary Beidou signal capturing method
CN113938157A (en) PMF-FFT-based short burst signal rapid capturing method and system
CN113253313A (en) Method for improving Doppler frequency estimation precision of PMF-FFT system
CN107247276B (en) Weak signal capturing method based on overlapped multi-block zero-filling algorithm
US20070177699A1 (en) Interpolation processing for enhanced signal acquisition
Sisi et al. Carrier frequency and symbol rate estimation based on cyclic spectrum
CN115980798A (en) Fast unambiguous signal capture algorithm
CN105429918A (en) Rapid acquisition method used for deep space measurement and control signals
CN111082835A (en) Pseudo code and Doppler combined capturing method of direct sequence spread spectrum signal under high dynamic condition
CN114217329A (en) Short code capturing method based on serial search
CN114696869B (en) Beidou No. three satellite RDSS service outbound signal capturing method under low signal-to-noise ratio
CN112600784B (en) Large frequency offset bit synchronization method based on quadratic differential correlation
CN110007322B (en) Beidou B1I signal capturing method based on coherent down-sampling
CN110958035A (en) Frequency secondary capturing device and method based on triangular envelope fitting

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