CN109143292B - Method and device for measuring zero-crossing offset of navigation signal phase detection curve - Google Patents

Abstract

The invention discloses a method for measuring the zero-crossing point offset of a phase-discrimination curve of a navigation signal, comprising the steps of: collecting navigation signal data; calculating the zero-crossing point offset of the phase-discrimination curve of the collected signal; calculating the zero-crossing point offset of the phase-discrimination curve of a reference signal; calculating The difference between the zero-crossing point offset of the phase detection curve of the acquisition signal and the zero-crossing point offset of the phase detection curve of the reference signal under the same correlator interval is used to obtain the zero-crossing point offset of the phase detection curve of the navigation signal. By deducting the zero-crossing point offset of the reference signal phase detection curve, the influence of pseudo codes and data between components on the calculation of the offset is reduced, and the zero-crossing point offset of the phase detection curve acquired in different time periods has good consistency and measurement accuracy. High, suitable for the calculation and analysis of the zero-crossing point of the phase detection curve caused by the distortion of the navigation load, and provides an effective means for the optimal design, delivery, test, and rapid evaluation of the navigation load.

Description

Method and device for measuring zero-crossing offset of navigation signal phase detection curve

technical field

The invention relates to the field of navigation signal measurement, in particular to a method and equipment for measuring the zero-crossing point offset of a phase detection curve of a navigation signal.

Background technique

At present, there are two main methods for measuring the zero-crossing point offset of the phase detection curve of the navigation signal:

The first is to make measurements with a navigation monitoring receiver, which requires the monitoring receiver to be capable of measuring at multiple fixed correlator intervals. The influence of modulation data, authorization code and other factors can be eliminated by monitoring receiver measurement. However, due to the limitation of hardware implementation conditions, the correlator interval is relatively large and cannot be set arbitrarily, which makes the monitoring receiver not sensitive enough to the subtle features of the signal. For the BOC modulation signal widely studied and used at present, the monitoring receiver adopts a specific non-matching processing method. At this time, the evaluation of the navigation signal quality needs to measure and analyze the zero-crossing offset of the S-curve under the condition of matching reception.

The second is to collect the radio frequency signal through a high-speed oscilloscope, and adopt an off-line analysis method to obtain the analysis results. At present, Beidou, GPS, and Galileo navigation systems all broadcast multiple navigation signals on one frequency point. There are intermodulation signals in the process of synthesizing multiple navigation signals, and there are aperiodic authorization codes and aperiodic authorization codes in the pseudo codes of the synthesized signals. Data modulation, when the composite signal is used for analysis, the analysis results are easily affected by intermodulation components, authorization codes, and data modulation, which may lead to large fluctuations or even opposite results. In the process of signal acquisition by the oscilloscope, although the sampling rate of the oscilloscope is high, the storage depth of the oscilloscope is small, and it is difficult to track and demodulate the data acquisition. There is an aperiodic authorization part in the received signal component, and the S curve corresponding to the authorization code signal component cannot be analyzed. Zero crossing offset. At the same time, in the off-line analysis method of collecting data, it is necessary to first generate the phase detection curve according to the correlation function, and then search for the zero-crossing point offset of the phase detection curve. The algorithm is relatively complicated and the calculation time is long.

Contents of the invention

In view of the above-mentioned defects in the prior art, embodiments of the present invention provide a zero-crossing point offset measurement method and device for a navigation signal phase detection curve with low computational complexity and high measurement accuracy.

The present invention can be implemented in numerous ways, including as a method, system, apparatus, apparatus or computer readable medium, several embodiments of the invention are discussed below.

A method for measuring a zero-crossing offset of a navigation signal phase detection curve, comprising the steps of:

Collect navigation signal data;

Calculate the zero-crossing point offset of the acquisition signal phase detection curve;

Calculate the zero-crossing point offset of the phase detection curve of the reference signal;

The difference between the zero-crossing point offset of the phase detection curve of the acquisition signal and the zero-crossing point offset of the phase detection curve of the reference signal under the same correlator interval is calculated to obtain the zero-crossing point offset of the phase detection curve of the navigation signal.

Further, the step of calculating the zero-crossing point offset of the acquisition signal phase detection curve includes:

(2-1) filtering the collected signal;

(2-2) If the signal acquisition is homologous acquisition, directly enter the pseudo code search process, otherwise complete the frequency estimation of the signal through frequency search, and enter the pseudo code search process;

(2-3) Carry out pseudo code search processing to signal, determine signal pseudo code initial phase position;

(2-4) Calculate the signal correlation function, search for the main peak of the correlation function, and calculate the zero-crossing point offset of the signal phase detection curve under the correlator interval.

Further, the step (2-2) frequency search step is to select any short code, adjust the frequency control word of the digitally controlled oscillator of the code and the digitally controlled oscillator of the carrier to carry out frequency point traversal, to generate new pseudo-code and carrier, utilize The newly generated carrier performs down-conversion processing on the signal, and then performs correlation processing with the newly generated pseudo code, and determines the interval of the frequency based on the maximum output of the correlation function.

Further, step (2-3) pseudo-code search step is to filter the signal after the down-conversion process, recalculate the frequency control word of the code digital control oscillator, utilize the updated pseudo-code rate to regenerate the pseudo-code, and Use the newly generated pseudo code to recalculate the maximum value of the correlation function, and the sampling point corresponding to the maximum value of the correlation function is the initial position of the phase of the pseudo code.

Further, the starting position of the pseudo-code phase is marked as the counting position, and in the subsequent processing, the counting starts from the counting position of the collected signal.

Further, in the step (2-4) of calculating the signal correlation function step, when the signal sampling rate reaches the preset accuracy, re-fetching is started from the counting position, and the pseudo-code and carrier wave generated by the phase search step are directly used to obtain the signal Correlation function; when the signal sampling rate does not reach the preset accuracy, adjust the code phase control word to regenerate the pseudo code to obtain the correlation function of the signal.

Further, the step (2-4) calculates the step of shifting the zero-crossing point of the phase detection curve of the signal under the correlator interval, including moving the correlation function so that the maximum value of the correlation function is located on the vertical axis. When the loop is locked, the phase detection curve of the signal passes The zero offset is half the interval between the working points of the leading correlator and the lagging correlator.

Further, before calculating the offset of the zero-crossing point of the phase detection curve of the signal at the interval of the correlator, an interpolation process is performed on the main peak of the correlation function.

Further, the step of calculating the offset of the zero-crossing point of the phase detection curve of the reference signal includes extracting the navigation message corresponding to the signal acquisition time, synthesizing the navigation message into an ideal baseband signal, generating a pseudocode, and obtaining different correlations by using the method of step (2-4). The zero-crossing point offset of the phase detection curve of the reference signal under the device interval, wherein, when the signal acquisition is homologous acquisition, the pseudo code is generated according to the agreed code rate, and when the signal acquisition is non-homologous acquisition, it is estimated according to the The frequency offset compensates the code rate, and generates a pseudo code according to the compensated code rate.

A device for measuring the zero-crossing point offset of a phase detection curve of a navigation signal, comprising a processor configured to perform the steps of any one of claims 1-8.

The positive and beneficial technical effects that can be realized by the embodiments of the present invention include: by deducting the zero-crossing point offset of the phase detection curve of the reference signal, the influence of pseudo codes and data between components on the calculation of the offset is reduced, and the acquired signals of different time periods are obtained. The zero-crossing point offset of the phase detection curve has good consistency and high measurement accuracy. It is suitable for the calculation and analysis of the zero-crossing point of the phase detection curve caused by the distortion of the navigation load, and provides an effective means for the optimal design, delivery, test, and rapid evaluation of the navigation load; Limited by the interval setting of the correlator of the traditional monitoring receiver, the phase relationship of the authorization code can be obtained without demodulation and extraction of the message, and the fast and high-precision measurement of the zero-crossing point offset of the phase detection curve corresponding to the long code signal component can be completed; no calculation is required The phase detection curve of the navigation signal has low computational complexity.

Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

Description of drawings

The invention will be illustrated by way of example with reference to the accompanying drawings, in which:

Fig. 1 is the flowchart of the zero-crossing point offset measurement method of the navigation signal phase detection curve provided by the embodiment of the present invention;

Fig. 2 is a schematic diagram of the main peak of the correlation function provided by the embodiment of the present invention.

Detailed ways

All features disclosed in this specification, or steps in all methods or processes disclosed, may be combined in any manner, except for mutually exclusive features and/or steps.

Any feature disclosed in this specification, unless specifically stated, can be replaced by other alternative features that are equivalent or have similar purposes. That is, unless expressly stated otherwise, each feature is one example only of a series of equivalent or similar features.

Fig. 1 is the flow chart of the zero-crossing point offset measurement method of the navigation signal phase detection curve provided by the embodiment of the present invention, as shown in Fig. 1, comprising steps:

(1) Collecting navigation signal data;

(2) Calculate the zero-crossing offset of the acquisition signal phase detection curve;

(3) Calculate the zero-crossing point offset of the reference signal phase detection curve;

(4) Calculate the difference between the zero-crossing point offset of the acquisition signal phase detection curve and the reference signal phase detection curve zero-crossing point offset under the same correlator interval, and obtain the zero-crossing point offset of the navigation signal phase detection curve.

The steps of collecting navigation signal data include: collecting the PPS (Pulse Per Second) signal of the navigation load, the navigation message and the satellite time; using the PPS signal of the navigation load to maintain the local second time to ensure that the local second time is consistent with the load second time ;Collect the navigation signal on the rising edge of the PPS, and when the signal is triggered, record the week count and second count when triggering the acquisition synchronously, extract the navigation message from the message of the navigation signal according to the week count and second count, and generate it from the local authorization code The module extracts the authorization code. The authorization code extraction process is not limited by the interval setting of the correlator of the traditional monitoring receiver, and the phase relationship of the authorization code can be obtained without demodulating and extracting the message.

The steps for calculating the zero-crossing point offset of the acquisition signal phase detection curve include:

(2-1) filtering the collected signal;

(2-2) If the signal acquisition is homologous acquisition, directly enter the pseudo code search process, otherwise complete the frequency estimation of the signal through frequency search, and enter the pseudo code search process;

(2-3) Carry out pseudo code search processing to signal, determine signal pseudo code initial phase position;

(2-4) Obtain the signal correlation function, search for the main peak of the correlation function, and calculate the zero-crossing point offset of the signal phase detection curve under the correlator interval.

Step (2-1) The step of filtering the collected signal includes: according to the bandwidth requirements of the analysis object, using an ideal filter to filter out the out-of-band signal, the characteristics of the ideal filter are as follows:

The filtering method is to perform FFT (Fourier) transformation on the signal data, and calculate the position of the point corresponding to f _L and f _h after FFT transformation. The calculation formula is Point _L ＝f _L ×L _data /f _s , Point _h ＝f _h ×L _data /f _s , where L _data represents the length of the signal data, usually the length of the signal data is a pseudo-code period of a short code, and f _s represents the sampling rate. Except for retaining the data in the range of [Point _L , Point _H ] and [L _data -Point _H , L _data -Point _L ], the rest of the signal data are all set to zero, and then IFFT is performed on the retained signal data to obtain the manager Want to filter the filtered signal data.

Step (2-2) If the signal acquisition is homologous acquisition (the reference frequency of the acquisition device adopts the frequency output by the load), skip the frequency search step, directly down-convert the signal and enter the pseudo code search process, if the signal acquisition is non-homogeneous Source acquisition, complete the frequency estimation of the signal through frequency search, and then enter the pseudo code search process.

The frequency search step is to select any short code, adjust the frequency control word Fcw _code of the code digitally controlled oscillator and the frequency control word Fcw _car of the carrier digitally controlled oscillator to conduct a rough search to generate a new pseudo code and carrier. Exemplarily, within the Doppler range [ _{-dpl max} ,d _p l _max ], Fcw car traverses each frequency point according to the interval of L _data /4f _s , for example, when Fcw _car =-dpl _max , Fcw _code =- Under Fcw _car × R _c /f _c (where f _c is the nominal carrier frequency, R _c is the nominal pseudo-code rate), the carrier with frequency f _c + Fcw _car and the rate of R _c + Fcw _code are generated Pseudo-code, the length of which is L _data , after using the newly generated carrier to down-convert the signal, it is correlated with the newly generated pseudo-code, that is s(t) represents the filtered signal, c(t) is the local reproduced pseudo code, conj represents the conjugate operation, using the maximum correlation output max(R) as the criterion to determine the possible range of the frequency, and then in In the possible range of frequency, the frequency step search is smaller, and the maximum correlation output is still used as the criterion, and the frequency estimation error is controlled at the Hz level.

Step (2-3) The pseudo code search step is to filter the signal after the down-conversion process, recalculate the frequency control word of the digitally controlled oscillator, use the updated pseudo code rate to regenerate the pseudo code, and use the newly generated The pseudo-code recalculates the maximum value of the correlation function, and the sampling point corresponding to the maximum value of the correlation function is the initial position of the phase of the pseudo-code.

Specifically, the Fcw _car obtained after the frequency fine search is used to down-convert the signal, and an ideal filter is used to filter out the double frequency component. The characteristics of the filter are as follows:

Recalculate Fcw _code =-Fcw _car ×R _c /f _c , use the updated pseudo code rate R _c +Fcw _code to regenerate the pseudo code with a length of L _data , according to Calculate the maximum value of the correlation function R, the sampling point corresponding to the maximum value of the correlation function is the phase starting point position of the pseudo code, and mark the phase starting position of the pseudo code as the access position, and in the subsequent processing, start from the acquisition position of the collected signal Access.

Step (2-4) In the step of calculating the signal correlation function, when the signal sampling rate reaches the preset accuracy, start to take the number again from the above-mentioned number fetching position, and directly use the pseudo code and the carrier wave generated by the phase search step to obtain the correlation function of the signal; the signal When the sampling rate does not reach the preset accuracy, adjust the code phase control word to regenerate the pseudo code to obtain the correlation function of the signal.

Exemplarily, if the sampling rate of the signal can reach the accuracy of one thousandth of a chip, start to retake the number at the mark position, update s(t), and use the pseudocode and carrier generated by the phase search step to obtain the correlation function of the signal Considering that in most cases, the phase detection algorithm used by the monitoring receiver is non-coherent processing, so the modulo operation is performed on the relevant output; if the signal sampling rate does not reach the accuracy of one thousandth of a chip, adjust the phase of the pseudo-code digital control oscillator The control word is used to obtain a high-precision correlation function, and the pseudo-code is regenerated by continuously adjusting the initial value of the phase of the pseudo-code digitally controlled oscillator, and the pseudo-code generated each time is multiplied by the signal after down-conversion processing and integrated to obtain Complete coverage of the main peak of the correlation function plus or minus one chip.

The signal acquisition device records the time when the signal acquisition is triggered, and generates a long code sequence based on this time to ensure that the long code in the acquired signal is consistent with the local long code, and uses the frequency offset information estimated from the short code to correct the frequency and compensate In the long code, the same processing method as the short code is used to obtain the correlation function with one-thousandth resolution. Through the processing of the correlation function, the zero-crossing point offset of the phase detection curve corresponding to the long code signal component is obtained.

Optimally, the main peak of the correlation function is interpolated before calculating the offset of the zero-crossing point of the phase detection curve of the signal at the interval of the correlator. Exemplarily, on the basis that the resolution of the main peak of the correlation function is one thousandth of a chip, a cubic spline interpolation method is used to insert 100 points between every two adjacent points to complete the interpolation process for the main peak of the correlation function, so that Increased resolution and continuity of correlation functions.

Step (2-4) The step of calculating the zero-crossing shift of the signal phase detection curve under the correlator interval includes moving the correlation function so that the maximum value of the correlation function is located on the vertical axis. When the loop is locked, the zero-crossing shift of the signal phase detection curve It is half of the interval between the working points of the leading correlator and the lagging correlator.

Fig. 2 is a schematic diagram of the main peak of the correlation function provided by the embodiment of the present invention, the width of which is ±1 chip, the vertical axis represents the amplitude of the correlation peak, and the horizontal axis represents the time delay. Move the correlation function so that the maximum point C of the correlation function is located on the vertical axis, the working point of the leading correlator corresponds to the position A of the correlation function, and the coordinates are marked as (x _A , y _A ), the working point of the lagging correlator corresponds to the position B of the correlation function, and the coordinate Marked as (x _B ,y _B ), when the loop is locked, the amplitude of the output of the leading correlator is equal to the amplitude of the output of the lagging correlator, that is, y _A =y _B , the correlator interval dspace=|x _A |+|x _B |, the zero-crossing offset of the phase detection curve is:

That is, when the loop is locked, the offset of the zero-crossing point of the signal phase detection curve is half of the working point interval between the leading correlator and the lagging correlator.

If it is necessary to calculate the offset of the zero-crossing point of the signal phase detection curve when the correlator interval approaches from 0 to 2 chips, start from point C and determine the horizontal line y _AB = y _C -N×C _{step according to the expected step} , N=1, 2, 3L M, M and C _step are selected according to the scope and precision of the analysis, search for the main peak of the correlation function, search for the intersection point of y _AB and the correlation function, and after finding the intersection point, you can obtain the intersection point in the horizontal direction coordinates on the axis, then follow the formula Calculate the zero-crossing point offset of the signal phase detection curve when the correlator interval is dspace, N traverses from 1 to M, and the corresponding zero-crossing point offset of the signal phase detection curve under various continuous correlator intervals can be obtained.

Due to the influence of factors such as long codes, data bits, and intermodulation components, the zero-crossing point offsets of the signal phase detection curves calculated at different times are quite different, and even the opposite deviation occurs, which shows that the results of direct calculations cannot truly reflect The zero-crossing point offset of the phase detection curve caused by the distortion in the navigation load generation process needs to deduct the zero point offset caused by the ideal signal itself to accurately reflect the zero-crossing point offset of the phase detection curve caused by the distortion in the navigation load generation process.

Step (3) The step of calculating the offset of the zero-crossing point of the phase detection curve of the reference signal includes extracting the navigation message corresponding to the signal acquisition time, synthesizing the navigation message into an ideal baseband signal to generate a pseudocode, and using the method of step (2-4) to obtain different The zero-crossing point offset of the reference signal phase detection curve under the correlator interval, wherein, when the signal acquisition is homologous acquisition, the pseudo code is generated according to the agreed code rate, and when the signal acquisition is non-homologous acquisition, it is estimated according to step (2-2) The frequency offset compensates the code rate, and generates a pseudo code according to the compensated code rate.

A device for measuring the zero-crossing point offset of a phase detection curve of a navigation signal, comprising a processor, and the processor is used to execute the steps described in claims 1-8.

The different aspects, embodiments, implementations or features of the invention can be used alone or in any combination.

The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, and any new method or process step or any new combination disclosed.

Claims (8)

1. a zero-crossing shift measurement method of a navigation signal phase detection curve, characterized in that it comprises the steps: Collect navigation signal data; Calculate the zero-crossing point offset of the acquisition signal phase detection curve; Calculate the zero-crossing point offset of the phase detection curve of the reference signal; Calculate the difference between the zero-crossing point offset of the acquisition signal phase detection curve and the zero-crossing point offset of the reference signal phase detection curve under the same correlator interval, and obtain the zero-crossing point offset of the navigation signal phase detection curve; The steps for calculating the zero-crossing point offset of the acquisition signal phase detection curve include: (2-1) filtering the collected signal; (2-2) If the signal acquisition is homologous acquisition, directly enter the pseudo code search process, otherwise complete the frequency estimation of the signal through frequency search, and enter the pseudo code search process; (2-3) Carry out pseudo code search processing to signal, determine signal pseudo code initial phase position; (2-4) Calculate the signal correlation function, search for the main peak of the correlation function, and calculate the zero-crossing point offset of the signal phase detection curve under the correlator interval; The step of calculating the zero-crossing point offset of the phase detection curve of the reference signal includes extracting the navigation message corresponding to the signal acquisition time, synthesizing the navigation message into an ideal baseband signal, generating a pseudo code, and using the method of step (2-4) to obtain The zero-crossing point offset of the phase detection curve of the reference signal, wherein, when the signal acquisition is homologous acquisition, the pseudo code is generated according to the agreed code rate, and when the signal acquisition is non-homologous acquisition, the frequency offset estimated in step (2-2) is used The code rate is compensated, and a pseudo code is generated according to the compensated code rate. 2. the zero-crossing offset measurement method of a kind of navigation signal phase detection curve according to claim 1, it is characterized in that, step (2-2) frequency search step is to select any short code, adjusts code digital control oscillator Perform frequency point traversal with the frequency control word of the carrier digitally controlled oscillator to generate a new pseudo code and carrier, use the newly generated carrier to perform down-conversion processing on the signal, and then perform correlation processing with the newly generated pseudo code to obtain The maximum output of the correlation function is the interval where the criterion determines the frequency. 3. the zero-crossing offset measurement method of a kind of navigation signal phase detection curve according to claim 2, it is characterized in that, step (2-3) pseudo code search step is to filter the signal after down-conversion processing, Recalculate the frequency control word of the code digitally controlled oscillator, use the updated pseudocode rate to regenerate the pseudocode, and use the newly generated pseudocode to recalculate the maximum value of the correlation function, and the sampling point corresponding to the maximum value of the correlation function is the pseudocode Phase start position. 4. the zero-crossing offset measuring method of a kind of navigation signal phase detection curve according to claim 3, it is characterized in that, mark pseudo-code phase starting position is the counting position, in follow-up processing, from the counting of acquisition signal The position starts counting. 5. the zero-crossing offset measurement method of a kind of navigation signal phase detection curve according to claim 4, is characterized in that, in step (2-4) calculates signal correlation function step, when signal sampling rate reaches preset accuracy, Start re-fetching from the counting position, and directly use the pseudo-code generated by the correlation search step and the carrier to obtain the correlation function of the signal; when the signal sampling rate does not reach the preset accuracy, adjust the code phase control word to regenerate the pseudo-code to obtain the signal related functions. 6. the zero-crossing offset measurement method of a kind of navigation signal phase-detection curve according to claim 1, is characterized in that, the step (2-4) calculates the step of the signal phase-detection curve zero-cross offset under the correlator interval The moving correlation function is included so that the maximum value of the correlation function is located on the vertical axis. When the loop is locked, the zero-crossing point offset of the signal phase detection curve is half of the working point interval between the leading correlator and the lagging correlator. 7. the zero-crossing offset measurement method of a kind of navigation signal phase detection curve according to claim 1, it is characterized in that, before calculating the signal phase detection curve zero-crossing offset under the correlator interval, the main peak of correlation function is carried out Interpolation processing. 8. A device for measuring zero-crossing point offset of a phase detection curve of a navigation signal, characterized in that it comprises a processor, and the processor is configured to execute the method according to any one of claims 1-7.