A Method and System for Estimating the Center Frequency of a Single-Tone Continuous-Wave Interference Carrier

Abstract

The present application provides a method and system for estimating the carrier center frequency of single-tone continuous-wave interference. The method includes: obtaining the carrier frequency data output by a frequency-locked loop; constructing a carrier frequency data sequence and a carrier frequency data time sequence; performing a fitting operation on the carrier frequency data sequence; performing an interpolation operation on the carrier frequency data to obtain a carrier frequency interpolation sequence; performing a difference operation on the carrier frequency interpolation sequence to obtain a carrier frequency difference sequence; determining the minimum value of the carrier frequency difference sequence; and estimating the carrier center frequency based on the minimum value of the carrier frequency difference sequence. The advantages of the present application are as follows: it can be applied to a single satellite platform; and accurate estimation of the carrier center frequency of single-tone continuous-wave interference can be achieved only by relying on signal processing methods.

Description

Technical Field

[0001] This application belongs to the field of GNSS interference monitoring technology and applications, and particularly relates to a method and system for estimating the carrier center frequency of single-tone continuous-wave interference. Background Art

[0002] The Global Navigation Satellite System (GNSS) is a very important type of space infrastructure that can provide precise, all-weather positioning, navigation, and timing (PNT) services to users worldwide. Currently, GNSS has been widely applied in many fields such as economic construction, scientific research, and national defense and military. Because of this, the inherent vulnerability of GNSS has gradually emerged. In particular, the emergence of malicious GNSS interference has greatly endangered the security of GNSS-based applications and systems. Therefore, GNSS interference monitoring technology and applications have become one of the research focuses.

[0003] Single-tone continuous-wave interference is one of the very common and high-occurrence GNSS interferences. Researchers have conducted extensive and in-depth research on single-tone continuous-wave interference monitoring technology and single-tone continuous-wave interference source localization technology. In the research on single-tone continuous-wave interference source localization technology, it usually involves measuring the Doppler frequency of the single-tone continuous-wave interference emitted by the single-tone continuous-wave interference source. And this Doppler frequency value is related to the carrier center frequency of the single-tone continuous-wave interference.

[0004] Since the single-tone continuous-wave interference source belongs to a non-cooperative signal source, the carrier center frequency of the single-tone continuous-wave interference emitted by the single-tone continuous-wave interference source is usually unknown and needs to be estimated. However, currently, it is very difficult for a single satellite platform to estimate the carrier center frequency of single-tone continuous-wave interference only relying on signal processing methods without auxiliary means. Summary of the Invention

[0005] The purpose of the present invention is to propose a method and system for estimating the carrier center frequency of single-tone continuous-wave interference. This method and system are applicable to a single satellite platform to accurately estimate the carrier center frequency of single-tone continuous-wave interference only relying on signal processing methods and without auxiliary means, and solve the problem of accurately estimating the carrier center frequency of single-tone continuous-wave interference by a single satellite platform only relying on signal processing methods without auxiliary means.

[0006] To achieve the above purpose, this application proposes a method for estimating the carrier center frequency of single-tone continuous-wave interference, including:

[0007] Step S101) Obtain the carrier frequency data output by the frequency-locked loop;

[0008] Step S102) Construct a carrier frequency data sequence and a carrier frequency data time sequence;

[0009] Step S103) Perform a fitting operation on the carrier frequency data sequence;

[0010] Step S104) Perform an interpolation operation on the carrier frequency data to obtain a carrier frequency interpolation sequence;

[0011] Step S105) Perform a difference operation on the carrier frequency interpolation sequence to obtain a carrier frequency difference sequence;

[0012] Step S106) Determine the minimum value of the carrier frequency difference sequence;

[0013] Step S107) Estimate the carrier center frequency based on the minimum value of the carrier frequency difference sequence.

[0014] As an improvement of the above method, the step S102) includes:

[0015] Construct a carrier frequency data sequence from all real-time estimated values of the single-tone continuous wave interference carrier frequency continuously output by the frequency-locked loop:

[0016] F = [f(1), f(2), f(3), …, f(n), …, f(N)]

[0017] where F represents the carrier frequency data sequence; N represents the total number of real-time estimated values of the single-tone continuous wave interference carrier frequency continuously output by the frequency-locked loop; f(n) represents the real-time estimated value of the single-tone continuous wave interference carrier frequency;

[0018] Based on the coherent integration time of the frequency-locked loop, construct a time sequence corresponding to the carrier frequency data sequence:

[0019] T = [T coh , 2T coh , 3T coh , …, NT coh

[0020] where T represents the time sequence; T coh represents the coherent integration time of the frequency-locked loop.

[0021] As an improvement of the above method, the step S103) includes:

[0022] Perform a fitting on the carrier frequency data sequence F, expressed as:

[0023] [K, S, Mu] = polyfit(T, F, Ord)

[0024] Among them, polyfit(·) represents the polynomial fitting function; Ord represents the polynomial fitting order; K represents the least squares fitting polynomial coefficient; S represents the estimation error; Mu represents the centering and scaling factor; T represents the time series.

[0025] As an improvement of the above method, the step S104) includes:

[0026] Construct an interpolation time series with high time resolution:

[0027]

[0028] Among them, T i represents the interpolation time series; M represents the interpolation multiple; the subscript i represents interpolation; T coh represents the coherent integration time of the frequency-locked loop;

[0029] Based on the fitting result of the carrier frequency data sequence F, interpolate the carrier frequency data sequence F, which is expressed as:

[0030] [F i , D] = polyval(K, T i , S, Mu)

[0031] Among them, F i represents the carrier frequency interpolation sequence; D represents the interpolation standard deviation; polyval(·) represents the interpolation function; K represents the least squares fitting polynomial coefficient; S represents the estimation error; Mu represents the centering and scaling factor.

[0032] As an improvement of the above method, the step S105) includes:

[0033] Based on the carrier frequency interpolation sequence F i , perform differencing on the carrier frequency interpolation sequence, which is expressed as:

[0034] F d (m) = F i (m + 1) - F i (m)

[0035] Among them, m represents the ordinal number of the carrier frequency interpolation sequence F i ; F i (m) represents the m-th element of the carrier frequency interpolation sequence F i ; F d represents the carrier frequency difference sequence; F d (m) represents the m-th element of the carrier frequency difference sequence; the subscript d represents differencing.

[0036] As an improvement of the above method, the step S106) includes:

[0037] Based on the carrier frequency difference sequence F d , determine the minimum value of the carrier frequency difference sequence and the ordinal number corresponding to the minimum value, expressed as:

[0038] [V, I] = min(F d )

[0039] where min(·) represents the function for determining the minimum value; V represents the minimum value of the carrier frequency difference sequence F d ; I represents the ordinal number corresponding to the minimum value of the carrier frequency difference sequence F d .

[0040] As an improvement of the above method, step S107) includes:

[0041] Based on the carrier frequency interpolation sequence F i and the ordinal number I corresponding to the minimum value of the carrier frequency difference sequence F d , determine the center frequency of the single-tone continuous wave interference carrier:

[0042] f c = F i (I)

[0043] where f c represents the estimated value of the center frequency of the single-tone continuous wave interference carrier; the subscript c represents the carrier.

[0044] This application also provides a system for estimating the center frequency of a single-tone continuous wave interference carrier, which is implemented based on the above method. The system includes:

[0045] A frequency-locked loop for tracking the single-tone continuous wave interference and outputting a real-time estimated value of the single-tone continuous wave interference carrier frequency every set time;

[0046] A construction time series module for obtaining the carrier frequency data output by the frequency-locked loop and constructing a carrier frequency data sequence and a carrier frequency data time series;

[0047] A fitting module for performing a fitting operation on the carrier frequency data sequence;

[0048] An interpolation module for performing an interpolation operation on the carrier frequency data to obtain a carrier frequency interpolation sequence;

[0049] A difference module for performing a difference operation on the carrier frequency interpolation sequence to obtain a carrier frequency difference sequence;

[0050] A minimum value determination module for determining the minimum value of the carrier frequency difference sequence; and

[0051] An estimated center frequency module is used to estimate the carrier center frequency according to the minimum value of the carrier frequency difference sequence.

[0052] Compared with the prior art, the advantages of this application are as follows:

[0053] 1. The method proposed by the present invention can be applied to a single satellite platform;

[0054] 2. The method proposed by the present invention can achieve accurate estimation of the carrier center frequency of the single-tone continuous wave interference only by relying on signal processing methods. Description of the Drawings

[0055] Figure 1 Shown is a flowchart of the method for estimating the carrier center frequency of single-tone continuous wave interference;

[0056] Figure 2 Shown is a block diagram of the structure of the system for estimating the carrier center frequency of single-tone continuous wave interference. Detailed Embodiments

[0057] The technical solutions of this application will be described in detail below with reference to the drawings.

[0058] As Figure 1 shown, a method for estimating the carrier center frequency of single-tone continuous wave interference proposed by the present invention includes:

[0059] Step S101) Obtain the carrier frequency data output by the frequency-locked loop;

[0060] A frequency-locked loop (FLL) is generally used to track and process single-tone continuous wave interference. The frequency-locked loop outputs a real-time estimated value f(n) (unit: Hz) of the carrier frequency of the single-tone continuous wave interference every time interval T coh . Among them, T coh represents the coherent integration time of the frequency-locked loop; n represents the ordinal number of the real-time estimated value of the carrier frequency of the single-tone continuous wave interference output by the frequency-locked loop.

[0061] Step S102) Construct a time series of the carrier frequency data;

[0062] Construct a carrier frequency data sequence from all the real-time estimated values of the carrier frequency of the single-tone continuous wave interference continuously output by the frequency-locked loop: F = [f(1), f(2), f(3),..., f(N)]. Among them, F represents this carrier frequency data sequence; N represents the total number of the real-time estimated values of the carrier frequency of the single-tone continuous wave interference continuously output by the frequency-locked loop.

[0063] Based on the coherent integration time of the frequency-locked loop, construct a time series corresponding to the carrier frequency data sequence: T = [T coh, 2T coh , 3T coh , …, NT coh . Among them, T represents the time series.

[0064] Step S103) Fit the carrier frequency data;

[0065] Generally, the signal input to the frequency-locked loop contains both single-tone continuous wave interference and noise, and may also contain other signal components. Therefore, the real-time estimated value f(n) of the single-tone continuous wave interference carrier frequency output by the frequency-locked loop fluctuates on a microscopic scale and conforms to the real-time change trend of the carrier frequency on a macroscopic scale.

[0066] To eliminate the fluctuations of f(n) on a microscopic scale, first fit the carrier frequency data sequence F. The fitting operation is expressed as:

[0067] [K, S, Mu] = polyfit(T, F, Ord) (1)

[0068] Among them, polyfit(·) represents the polynomial fitting function; Ord represents the polynomial fitting order; K represents the least squares fitting polynomial coefficient; S represents the estimation error; Mu represents the centering and scaling factor.

[0069] Step S104) Interpolate the carrier frequency data;

[0070] Before interpolating the carrier frequency data, first construct a high-time-resolution interpolation time series: where, T i represents the interpolation time series; M represents the interpolation multiple; the subscript i represents interpolation.

[0071] Based on the fitting result of the carrier frequency data sequence F, interpolate the carrier frequency data sequence F. The interpolation operation is expressed as:

[0072] [F i , D] = polyval(K, T i , S, M u ) (2)

[0073] where, F i represents the carrier frequency interpolation sequence; D represents the interpolation standard deviation; polyval(·) represents the interpolation function.

[0074] Step S105) Perform a difference operation on the carrier frequency interpolation sequence;

[0075] Based on the carrier frequency interpolation sequence F i , perform a difference on the carrier frequency interpolation sequence. The difference operation is expressed as:

[0076] F d F(m) = i F(m + 1)- i F(m)(3)

[0077] where m represents the ordinal number of the carrier frequency interpolation sequence F i ; F i F(m) represents the m-th element of the carrier frequency interpolation sequence F i ; F d represents the carrier frequency difference sequence; F d F(m) represents the m-th element of the carrier frequency difference sequence; the subscript d represents difference.

[0078] Step S106) Determine the minimum value of the carrier frequency difference sequence;

[0079] Based on the carrier frequency difference sequence F d , determine the minimum value of the carrier frequency difference sequence and the ordinal number corresponding to the minimum value. The operation of determining the minimum value of the carrier frequency difference sequence and the ordinal number corresponding to the minimum value is expressed as:

[0080] [V, I]=min(F d )(4)

[0081] where min(·) represents the function of determining the minimum value; V represents the minimum value of the carrier frequency difference sequence F d ; I represents the ordinal number corresponding to the minimum value of the carrier frequency difference sequence F d .

[0082] Step S107) Estimate the carrier center frequency;

[0083] Based on the carrier frequency interpolation sequence F i and the ordinal number I corresponding to the minimum value of the carrier frequency difference sequence F d , the carrier center frequency of the single-tone continuous wave interference can be determined:

[0084] f c =F i (I)(5)

[0085] where f c represents the estimated value of the carrier center frequency of the single-tone continuous wave interference; the subscript c represents the carrier.

[0086] As Figure 2 shown, this application also provides a system for estimating the carrier center frequency of single-tone continuous wave interference, which is implemented based on the above method. The system includes:

[0087] A frequency-locked loop is used to track and process single-tone continuous-wave interference, and outputs a real-time estimated value of the carrier frequency of the single-tone continuous-wave interference every set time.

[0088] A time series module is constructed to obtain the carrier frequency data output by the frequency-locked loop and construct a carrier frequency data sequence and a carrier frequency data time series.

[0089] A fitting module is used to perform a fitting operation on the carrier frequency data sequence.

[0090] An interpolation module is used to perform an interpolation operation on the carrier frequency data to obtain a carrier frequency interpolation sequence.

[0091] A difference module is used to perform a difference operation on the carrier frequency interpolation sequence to obtain a carrier frequency difference sequence.

[0092] A minimum value determination module is used to determine the minimum value of the carrier frequency difference sequence.

[0093] A central frequency estimation module is used to estimate the carrier center frequency based on the minimum value of the carrier frequency difference sequence.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that any modification or equivalent replacement of the technical solutions of the present application does not depart from the spirit and scope of the technical solutions of the present application, and they should all be covered by the scope of the claims of the present application.

Claims

1. A method for estimating the center frequency of a single-tone continuous wave interference carrier, comprising: Step S101) obtaining carrier frequency data output by a frequency locked loop; Step S102) constructing a carrier frequency data sequence, and then constructing a carrier frequency data time sequence corresponding to the carrier frequency data sequence based on the coherent integration time of the frequency locked loop; Step S103) performing a fitting operation on the carrier frequency data sequence using the carrier frequency data time series; Step S104) performing an interpolation operation on the fitted carrier frequency data sequence to obtain a carrier frequency interpolation sequence; Step S105) performing a differential operation on the carrier frequency interpolation sequence to obtain a carrier frequency differential sequence; Step S106) determining the minimum value of the carrier frequency difference sequence; Step S107) estimating the carrier center frequency according to the minimum value of the carrier frequency difference sequence; The step S105) includes: Based on the carrier frequency interpolation sequence , the carrier frequency interpolation sequence is differentiated and expressed as: ； in, Represents the carrier frequency interpolation sequence The ordinal number of Represents the carrier frequency interpolation sequence No. elements; represents the carrier frequency difference sequence; The first phase of the carrier frequency difference sequence elements; subscript Indicates difference.

2. The method for estimating center frequency of a single-tone continuous wave interference carrier according to claim 1, wherein: The step S102) includes: The real-time estimated values ​​of all single-tone continuous wave interference carrier frequencies continuously output by the frequency locked loop are used to construct a carrier frequency data sequence: ； in, Represents a carrier frequency data sequence; Represents the total number of real-time estimated values ​​of single-tone continuous wave interference carrier frequency continuously output by the frequency locking loop; Indicates the real-time estimation value of the single-tone continuous wave interference carrier frequency; Based on the coherent integration time of the frequency locked loop, a time series corresponding to the carrier frequency data series is constructed: ； in, represents a time series; Represents the coherent integration time of the frequency locked loop.

3. The method for estimating center frequency of a single-tone continuous wave interference carrier according to claim 1, wherein: The step S103) includes: Carrier frequency data sequence Fitting is performed, expressed as: ； in, represents the polynomial fitting function; Indicates the polynomial fitting order; represents the least squares fitting polynomial coefficients; represents the estimation error; represents the centering and scaling factors; Represents a time series.

4. The method for estimating center frequency of a single-tone continuous wave interference carrier according to claim 1, wherein: The step S104) includes: Construct an interpolated time series with high temporal resolution: ； in, represents the interpolated time series; Indicates interpolation multiple; subscript represents interpolation; represents the coherent integration time of the frequency locked loop; Based on the carrier frequency data sequence The fitting results for the carrier frequency data sequence Interpolation is performed, expressed as: ； in, represents the carrier frequency interpolation sequence; represents the interpolation standard deviation; represents the interpolation function; represents the least squares fitting polynomial coefficients; represents the estimation error; represents the centering and scaling factors.

5. The method for estimating center frequency of a single-tone continuous wave interference carrier according to claim 1, wherein: The step S106) includes: Based on carrier frequency difference sequence , determine the minimum value of the carrier frequency difference sequence and the ordinal number corresponding to the minimum value, expressed as: ； in, Represents the minimum value determination function; Represents the carrier frequency difference sequence The minimum value of Represents the carrier frequency difference sequence The ordinal number corresponding to the minimum value of .

6. The method for estimating center frequency of a single-tone continuous wave interference carrier according to claim 1, wherein: The step S107) includes: Based on the carrier frequency interpolation sequence and carrier frequency difference sequence The ordinal number corresponding to the minimum value of , determine the center frequency of the single-tone continuous wave interference carrier: ； in, represents the estimated value of the center frequency of the single-tone continuous wave interference carrier; Indicates carrier wave.

7. A single-tone continuous wave interference carrier center frequency estimation system, based on the method described in any one of claims 1 to 6, characterized in that: The system comprises: The frequency locking loop is used to track and process the single-tone continuous wave interference and output a real-time estimation value of the single-tone continuous wave interference carrier frequency at a set time interval; A time series module is constructed to obtain carrier frequency data output by the frequency locked loop, construct a carrier frequency data sequence, and then construct a carrier frequency data time series corresponding to the carrier frequency data sequence based on the coherent integration time of the frequency locked loop; A fitting module, used for performing a fitting operation on a carrier frequency data sequence using a carrier frequency data time series; An interpolation module, used for performing an interpolation operation on the carrier frequency data to obtain a carrier frequency interpolation sequence; A differential module, used for performing differential operation on a carrier frequency interpolation sequence to obtain a carrier frequency differential sequence; A minimum value determination module, used to determine the minimum value of the carrier frequency difference sequence; and The center frequency estimation module is used to estimate the carrier center frequency according to the minimum value of the carrier frequency difference sequence.

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