A method for evaluating the similarity of Loran signals

Abstract

The present invention provides a Roland signal similarity evaluation method, which first constructs a mathematical model of an actual signal waveform, samples the actual signal waveform, and uses the sampled data to fit and solve the model parameters of the actual signal waveform. By comparing the mathematical model of the Roland theoretical signal waveform, the similarity between the actual signal waveform and the theoretical signal waveform can be evaluated more accurately and efficiently. The Roland signal evaluation method proposed by the present invention uses the waveform carrier frequency half-cycle peak data to solve the mathematical model parameters of the actual waveform, does not need to pre-calculate and store a large amount of reference data, and has the advantages of small memory usage and high calculation efficiency.

Description

Technical Field

[0001] The invention relates to a signal evaluation method, which is used in the field of Loran navigation timing. Background Art

[0002] The Loran navigation system provides navigation and timing information to system users by transmitting Loran signals. In order to ensure the navigation and timing service performance of the system and improve the signal capture success rate of the user terminal, the waveform of the actual transmitted Loran signal should be as close to the theoretical signal waveform as possible. However, due to the influence of high-power component parameter errors, transmission control errors, etc., the actual signal waveform cannot be consistent with the theoretical signal waveform, and it is necessary to measure and evaluate the difference between the actual signal waveform and the theoretical signal waveform. The traditional evaluation method is to use the "lookup table method" to calculate the carrier half-cycle peak ratio according to the theoretical formula of the Loran signal waveform to form a reference data table. When applied, the half-cycle peak ratio of the actual signal waveform is calculated and compared with the data table, and the closest group is selected to evaluate the similarity between the actual Loran waveform and the theoretical waveform. Considering the operability of the lookup table method, the step amount of the theoretical waveform model parameters in the reference data table cannot be infinitely reduced, so the actual Loran waveform obtained by the lookup table must be different from the theoretical waveform parameters. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the present invention provides a Roland signal similarity evaluation method. First, a mathematical model of the actual signal waveform is constructed. By sampling the actual signal waveform, the model parameters of the actual signal waveform are solved by fitting the sampled data. By comparing the mathematical model of the Roland theoretical signal waveform, the similarity between the actual signal waveform and the theoretical signal waveform can be evaluated more accurately and efficiently.

[0004] The technical solution adopted by the present invention to solve the technical problem comprises the following steps:

[0005] Step 1, sampling the Roland signal waveform output by the Roland reference analog source, discretizing the continuous signal, and obtaining a sampling sequence;

[0006] Step 2: Calculate the peak value X of the first M carrier frequency half cycles of the sampling sequence j ;

[0007] Step 3: Calculate the peak values ​​I of the first M carrier frequency half cycles of the theoretical signal waveform j (τ,A) and X j The root mean square of the deviation f(τ,A), where τ represents the synchronization deviation between the signal carrier and the envelope, and A represents a constant related to the peak antenna current amplitude;

[0008] Step 4, calculate partial derivatives of the root mean square f(τ, A) with respect to τ and A respectively, and solve the set of equations of partial derivatives to find a set of solutions τ′ and A′ that make f(τ, A) obtain the minimum value, that is, the actual signal waveform with τ′ and A′ as parameters is the best approximate fit of the theoretical signal waveform;

[0009] Step 5, calculate the deviation rate of τ′ relative to the theoretical waveform τ, and evaluate the similarity between the actual Loran waveform and the theoretical waveform.

[0010] The value of M is less than or equal to 12.

[0011] The value of M is 12.

[0012] The beneficial effects of the present invention are:

[0013] 1. Compared with the traditional "table lookup method", the present invention has the advantages of intuitive results and high evaluation accuracy.

[0014] 2. The Loran signal evaluation method proposed in the present invention uses the half-cycle peak data of the waveform carrier frequency to solve the mathematical model parameters of the actual waveform. It does not need to pre-calculate and store a large amount of reference data, and has the advantages of small memory usage and high calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flow chart of the method of embodiment 1 of the present invention;

[0016] Figure 2 Schematic diagram of the peak point of the Loran signal carrier according to Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0018] The leading edge of the Roland theory signal waveform is defined by the following formula:

[0019]

[0020] in:

[0021] represents the signal envelope;

[0022] sin(0.2πt+PC): represents the signal carrier, where PC is the phase coding of the signal, which takes the value of 0 or π, determined according to the phase coding rule of the system;

[0023] A: represents a constant related to the peak antenna current amplitude;

[0024] τ: represents the synchronization deviation between the signal carrier and the envelope;

[0025] The parameters τ and A of the Loran theoretical signal waveform can be set manually. The Loran transmission system generates an actual Loran waveform based on the set parameters τ and A. The change of parameter τ directly affects the success rate of user terminal signal capture. Therefore, the deviation of parameter τ is used to characterize the similarity between the actual signal waveform and the theoretical signal waveform.

[0026] like Figure 1 As shown, the Roland signal similarity evaluation method proposed in Example 1 of the present invention is specifically implemented as follows:

[0027] Step 1: Sample the Roland signal waveform output by the Roland reference analog source, discretize the continuous signal, and obtain a sampling sequence;

[0028] Step 2: The leading edge of the Roland theoretical waveform is before 65us, and the time span of a single half cycle is 5us. Considering that the parameter τ affects the time when the leading edge of the waveform reaches the peak, the 13th carrier half cycle may be at the trailing edge of the Roland waveform. To ensure the accuracy of the parameter solution, the peak values ​​of the first 12 carrier half cycles can be used at most when solving the actual Roland waveform parameters. The peak values ​​X of the first 12 carrier half cycles of the sampling sequence are calculated. j ;

[0029] Step 3: Calculate the peak value I of the first 12 carrier frequency half cycles of the theoretical signal waveform j (τ, A)(j=1~12) and X j (j=1~12) root mean square of deviation f(τ,A);

[0030] Step 4: Take the partial derivatives of the root mean square f(τ,A) with respect to τ and A respectively, and solve the set of equations of partial derivatives to find a set of solutions τ′ and A′ that minimize f(τ,A). That is, the actual signal waveform with τ′ and A′ as parameters is the best approximate fit of the theoretical signal waveform.

[0031] Step 5: Calculate the deviation rate of τ′ relative to the theoretical waveform’s τ to evaluate the similarity between the actual Loran waveform and the theoretical waveform.

[0032] Embodiment 2 of the present invention comprises the following steps:

[0033] Step 1: Generate a Roland signal waveform with A=1, τ=0 using a Roland reference analog source, set the sampling pulse frequency of the data acquisition device to 200MHz (time resolution reaches 5ns), and according to the time length of a single Roland waveform, each acquisition lasts 2us, and saves the discrete sampling sequence;

[0034] Step 2: Divide the sequence into multiple carrier half cycles according to the zero crossing points in the sampling sequence, such as Figure 2 shown.

[0035] The first 12 carrier half cycles of the Roland signal waveform front edge in the sampling sequence are analyzed, and the peak values ​​of the first 12 carrier half cycles in the sampling sequence are calculated. At the same time, the theoretical values ​​of the first 12 carrier half cycles are calculated according to the Roland theoretical signal waveform front edge formula, and the results are listed in Table 1.

[0036] Table 1 Carrier frequency half cycle peak value

[0037]

[0038]

[0039] Step 3: Calculate the peak value I of the first 12 carrier frequency half cycles of the theoretical signal waveform j (τ, A)(j=1~8) and X j (j=1~8) The root mean square of the deviation f(τ,A) is calculated as follows:

[0040]

[0041] Step 4: Find the partial derivative of the root mean square f(τ,A), set the partial derivative equal to zero, and combine the equations for the partial derivatives as follows:

[0042]

[0043] The solution of this set of equations is A'=0.99, τ'=0.5. This set of solutions can make f(τ,A) reach the minimum value, and the deviation between the actual waveform and the theoretical waveform is minimized. In addition, the solution of A and τ is obtained by table lookup method, which is A'=0.9, 6τ'=0.9.

[0044] Step 5: Calculate the deviation P between τ′ and the τ set by the analog source τ , the calculation formula is as follows:

[0045] P τ = abs(τ-τ′)

[0046] The P obtained by the method proposed by the present invention τ =0.5, P obtained by table lookup method τ =0.9, it is obvious that the method proposed by the present invention is superior to the traditional table lookup method.

Claims

1. A method for evaluating the similarity of Loran signals, characterized in that: The following steps are involved: Step 1, sampling the Roland signal waveform output by the Roland reference analog source, discretizing the continuous signal, and obtaining a sampling sequence; Step 2: Calculate the peak value X of the first M carrier frequency half cycles of the sampling sequence j ; The value of M is less than or equal to 12; Step 3: Calculate the peak values ​​I of the first M carrier frequency half cycles of the theoretical signal waveform j (τ,A) and X j The root mean square of the deviation f(τ,A), where τ represents the synchronization deviation between the signal carrier and the envelope, and A represents a constant related to the peak antenna current amplitude; Step 4, calculate partial derivatives of the root mean square f(τ, A) with respect to τ and A respectively, and solve the set of equations of partial derivatives to find a set of solutions τ′ and A′ that make f(τ, A) obtain the minimum value, that is, the actual signal waveform with τ′ and A′ as parameters is the best approximate fit of the theoretical signal waveform; Step 5, calculate the deviation rate of τ′ relative to the theoretical waveform τ, and evaluate the similarity between the actual Loran waveform and the theoretical waveform.

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