CN115685262A - Method for measuring consistency between navigation simulator channels based on signal amplitude-phase characteristics - Google Patents
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Abstract
The invention provides a method for measuring consistency between channels of a navigation simulator based on signal amplitude-phase characteristics, which comprises the steps of selecting single carrier signals of any frequency point in a simulator navigation system, respectively measuring the peak level of any two channel signals and the peak level of a synthesized signal, comparing the synthesized peak level with a single peak level, calculating the delayed phase difference according to the difference value, and further calculating the delay time between the two channels, wherein when the delay of the two channels is 0ns, the peak level of the synthesized signal is increased by 6.02dB compared with the single peak. The advantages are that: the measurement can be carried out by outputting a single carrier signal without the limitation of a modulation mode adopted by a navigation signal; the channel delay measurement method based on the peak level has the advantages that the accuracy of the channel delay measurement is high, the uncertainty of the channel delay measurement is smaller than that of the channel delay measurement method based on the original method, and a more reliable basis is provided for measurement of a simulator.
Description
Technical Field
The invention relates to the field of satellite navigation, in particular to a method for measuring consistency between channels of a navigation simulator based on signal amplitude-phase characteristics.
Background
In the scientific research and application process related to satellite navigation, the mode of receiving navigation satellite signals only by means of a Global Navigation Satellite System (GNSS) receiver (hereinafter referred to as a "receiver") is influenced by various uncontrollable factors such as the number of visible satellites, weather, electromagnetic environment and the like, so that the progress and efficiency of scientific research and verification work are reduced, and the requirements can not be met by obtaining diversified navigation satellite state scenes due to condition limitation. Therefore, it is preferred to use a GNSS signal simulator to simulate various navigation satellite signals. The GNSS signal simulator (hereinafter referred to as "simulator") is a GNSS system signal generator, and can provide global navigation satellite system signal simulation according to the condition of a moving carrier, and accurately simulate and generate GNSS satellite signals that can be received by the carrier. The satellite constellation comprises GPS, GLONASS, GALILEO, BDS and the like, can be used in each link of the research, development, production and measurement process of the GNSS receiver, can measure and identify the acquisition, tracking and measurement accuracy of the receiver, and is a key measuring instrument in the calibration process of the GNSS receiver.
At present, simulators in the market are mainly applied to calibration of receivers and research of methods thereof, and are applied to calibration work of various receivers (including high-dynamic and high-sensitivity receivers) in the future, accurate measurement and evaluation are carried out on receiving equipment in development, qualification examination and certification, high cost of field measurement is reduced or completely eliminated, and the limit of application in practical environments is eliminated. Meanwhile, the method is applied to measurement and research of the internal delay of the receiver, and the measurement of the index is the basis of precise time transfer and research thereof. Most simulator products are produced by foreign manufacturers (such as Spirent brands), and the products have high indexes and advanced performance. Many domestic manufacturers have the capability of independently developing and producing simulators, the independent development and production scale is continuously enlarged, and the technical level is continuously improved.
In view of the current situation of the development of satellite navigation systems, a navigation simulator is required to generate navigation signals of multiple frequency points, multiple systems and multiple systems. This requires that multiple modules are used to generate various signals within the simulator, and then the signals are uniformly superimposed. Due to circuit parameters, clock transmission delay, and differences in phase, and although frequency and environment changes in phase nonlinear effect and group delay of the radio frequency unit, channel consistency of signal simulation becomes an important problem affecting signal simulation accuracy. Even if the modules adopt the unified clock and adopt the same structure and devices, the problem of consistency of signal simulation channels among the devices is difficult to completely solve due to the difference among the devices and the problem of generated late characteristic drift of the devices after the devices are used for a period of time.
One channel of the simulator simulates one satellite, the consistency of internal channels is an important technical index, the channel consistency requires that a plurality of channels at the same frequency point are consistent in initial state under the same condition, the delay is 0 from the aspect of signal level, and if the delay exists in the initial state of each channel, the delay can be used as a system error to influence the whole simulation scene, thereby influencing the positioning of a receiver.
The traditional method for measuring the consistency between channels is to input a 1PPS signal output by a simulator into an oscilloscope as a trigger signal, measure BPSK signals of different channels output by the simulator by using another channel of the oscilloscope, measure the time delay from the turning point of the BPSK signals to 1PPS by using the oscilloscope, compare the time difference between the rising edges of the different channels (satellites) and 1PPS, and calculate the consistency error of the channels. The limitation of the method is that the turning point of the actual modulation signal is not a zero crossing point but a curve, and the turning point fluctuates up and down, so that a uniform time delay point cannot be found, the uncertainty is large, and the verification can be only carried out on ns magnitude. In addition, the method can only measure the signal of which the navigation frequency point is BPSK modulation, and cannot measure the signal adopting other modulation modes, thereby reflecting the problem of large limitation of the existing measurement mode.
In order to adapt to different application fields of different industries, a simulator needs to have a multi-system multi-frequency-point navigation signal output function, navigation signal modulation modes of different frequency points of different systems are different according to the definition of each system ICD, and the simulator has multiple modulation modes such as BPSK, QPSK and BOC modulation. However, existing simulator inter-channel consistency calibration methods only accommodate BPSK modulated signals.
Fig. 1 is a screenshot of a measurement result of calibrating consistency between channels of a simulator by using a conventional method, wherein the screenshot shows a position relationship between a BPSK signal flip point and a rising edge of a PPS signal of a simulator 1 which is output by four channels of the simulator independently, and at this time, a horizontal scale of the digital oscilloscope is large. Fig. 2 is an enlarged view of the four channel signal inversion points of fig. 1, when the horizontal dimension is 10ns/div. As can be seen from fig. 2, the signal turning point is not a zero-crossing point, but a signal with a small amplitude, so that it is difficult to find a real zero-crossing point, and thus the uncertainty of the measurement result is large.
So that the problems of the prior art are:
(1) The method can only measure the BPSK modulated navigation signals, cannot measure the consistency among channels of navigation signals of other modulation modes, and has great limitation.
(2) From the actual measurement result, in the prior art, the turning point used for measuring the BPSK modulation signal is not a signal point, but a section of fluctuating zero-crossing signal, and the measurement turning point has large uncertainty, so that the calibration result is inaccurate, and the uncertainty is ns magnitude.
The two problems can be clarified, and the existing method for calibrating the consistency between the channels of the simulator has low measurement accuracy and is difficult to truly reflect the consistency between the channels of the high-precision simulator.
Therefore, how to provide a method for measuring the consistency between channels of a satellite navigation simulator, which is applicable to a plurality of modulation modes, is a problem to be solved urgently.
Disclosure of Invention
Aiming at the limitation of the current method for calibrating the consistency between channels of the simulator, the invention provides a method for measuring the consistency between channels of the navigation simulator based on the amplitude-phase characteristics of signals, and solves the problems of BPSK modulation signal limitation and low measurement accuracy.
In order to achieve the above object, the technical solution of the present invention provides a method for measuring consistency between channels of a navigation simulator based on signal amplitude-phase characteristics, including: selecting a single carrier signal of any frequency point of the simulator navigation system, and independently measuring the peak level of any two channels, wherein the peak level requirements of the two channels are consistent. Simultaneously outputting two-channel signals, and measuring the peak level of the synthesized signal; comparing the synthesized peak value level with the single peak value level, judging whether the amplitude added value of the synthesized signal is 6.02dB, if not, obtaining a delayed phase difference according to the level difference value, and obtaining the delay time between two channels according to the phase difference.
Preferably, when the difference is not 6.02dB, the phase difference θ is obtained by performing inverse calculation according to the amplitude increase Δ' of the synthesized signal:
As a preferable preference of the above technical solution, preferably, the inter-channel delay time Δ t is calculated according to the phase difference θ;
preferably, if the amplitude increase of the synthesized signal is 6.02dB, the delay between the two channels is 0ns.
The invention has the advantages that: the measurement can be carried out as long as a single carrier signal can be selected to be output, and the measurement is not limited by a modulation mode adopted by the navigation signal; by utilizing the characteristic of the phase-amplitude characteristic of the single carrier signal, the turning point of the modulation signal is not required to be found, the peak level of the single carrier signal is displayed by reading a frequency spectrograph, and the delay between channels can be calculated according to the calculating method provided by the invention, wherein the uncertainty is superior to 10ps. Because the delay is calculated by adopting the peak level, the uncertainty of consistency measurement between channels of the simulator is reduced, the accuracy is high, the reference value is high, and a more reliable basis is provided for debugging.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a screenshot of a measurement result of consistency between channels of a calibration simulator in the prior art.
Fig. 2 is an enlarged view of the signal inversion point of the channel in fig. 1.
Fig. 3 is a flowchart of a measurement process provided in the technical solution of the present invention.
Fig. 4 is a connection block diagram of a single carrier signal-based simulator inter-channel consistency measurement apparatus in an embodiment of the present invention.
Fig. 5 shows the situation of measuring with a frequency spectrograph when the single channel of the navigation signal of the same frequency point outputs a single carrier signal by applying the method of the invention.
Fig. 6 shows the situation of measurement by a spectrometer when two channels of a navigation signal with the same frequency point are simultaneously outputting single carrier signals by applying the method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Now, the technical solution of the present invention is described with reference to an embodiment, and fig. 3 is a schematic flow chart provided by the embodiment of the present invention, as shown in fig. 3:
step 101, setting an initial state of the satellite navigation simulator.
The method comprises the steps of setting a simulator as a static scene, fixing a satellite and a carrier pseudo range, and selecting a single carrier signal of any frequency point of a navigation system.
Step 102, the peak levels of channel 1 and channel 2 are measured, respectively.
The simulator outputs satellite channel signals of any frequency point, and the spectrum analyzer is utilized to measure the signal peak value level P of the channel 1 0 . Keeping the simulator simulation setting unchanged, switching another channel 2, and measuring the peak level P of the channel 2 by using a spectrum analyzer 0 '. Judging whether the peak levels of the two channel signals are equal, i.e. P 0 ＝P 0 '. If the peak levels of the two channels are different, any one of the two peak levels is adjusted, so that the peak levels of the two channels are equal.
Step 103, measuring the combined peak level P of the combined signal after the two signals are combined 1 。
Specifically, the simulator outputs the two-channel signals in step 102 simultaneously, and the peak level of the synthesized signal is measured by the spectrum analyzer.
And step 104, calculating the peak level difference delta'.
Specifically, the peak level difference is: the difference between the peak level of the composite signal and the peak level of the single channel signal.
And 105, judging whether the peak level difference is 6.02dB, if so, proving that the delay between the two channels is 0ns, and otherwise, executing a step 106.
In detail, the signals of the channels 1 and 2 are superposed to obtain a theoretical superposition value. Because two paths of sine wave signals with the same amplitude and the same frequency of the two paths of synthesized signals have the phase difference of theta, the central frequency of the synthesized signals is not changed, and only the signal level and the phase are changed, as shown in the following formula:
in practical cases, the frequency of the synthesized signal is unchanged, and the amplitude changes with the phase difference. For a navigation simulator, the consistency delay between channels under the ideal condition of the satellite with the same frequency point and the same state is 0ns, namely the phase difference theta is 0.
The peak levels of the two-channel single-carrier signals being equal, i.e. P 0 ＝P 0 If the delay between the channels is 0ns, the amplitude of the two-path synthesized signal is 2 times that of the one-path signal according to the formula, the amplitude is converted into logarithm (dB) to be represented, and the amplitude increase value delta P of the two-path synthesized signal compared with the single-path signal is as follows: Δ P =20log 2=6.02db.
On the contrary, in step 105, if the peak level of the two-path synthesized signal is measured by the spectrum analyzer to be 6.02dB greater than the peak level of the single-path signal, it is proved that the delay between the two channels of the single-carrier signal simultaneously output by the frequency point of the simulator is 0ns, and the measurement is finished.
And 106, calculating the phase difference theta according to the peak level difference delta'.
In particular, the method comprises the following steps of,
And step 107, inversely calculating the delay time delta t according to the phase difference theta.
Fig. 4 is an instrument connection block diagram of the method for measuring the consistency between channels of the simulator provided by the invention, the simulator and the spectrum analyzer need to be started and preheated for half an hour before measurement, and the radio frequency signal output end of the simulator is connected with the signal input end of the spectrum analyzer.
In the channel consistency measurement method provided based on the technical scheme of the invention, a satellite navigation simulator simulates a static scene, satellites and carrier pseudo-ranges are fixed, a modulation signal is closed to enable a signal to output a single carrier, 1 satellite is simulated firstly, the peak level is measured, then 1 satellite is added, the signal peak value change value after superposition is measured, and the phase difference and the delay are calculated. The satellite delay of other channels can be verified by switching the superposed different channel satellites, so that the delay among all the channel satellites in the frequency point is obtained.
The method of the invention is explained by using a specific embodiment, the GSS9000 simulator of Spirent company imported from abroad is tested and verified, and a spectrum analyzer of R & S company in Germany is selected as the measuring equipment.
Selecting a GPSL1 frequency point as a measuring signal, wherein the frequency is 1.57542GHz, the period is about 0.63475ns, closing all error models, setting a static scene with fixed satellite and carrier pseudo-range, outputting a single-satellite single-channel single-carrier signal by a simulator, and measuring the peak level P of the signal by a frequency spectrograph 0 Was-58.10 dBm as shown in FIG. 5. Switching to another channel satellite signal, peak level P' 0 Also-58.10 dBm, the two channel signals amplitude is identical.
Changing the simulator output into a double-channel satellite single carrier, and actually measuring the peak level P of the synthesized signal without changing the simulator output 1 Was-52.08 dBm as shown in FIG. 6.
Peak level change value: Δ P = P 1 -P 0 ＝-52.08dBm-(-58.10dBm)＝6.02dB。
The measurement result is consistent with theoretical data when the delay is 0ns, and the output signals of the two channels are proved to have no delay. According to the method, one channel is kept unchanged and is used as a reference channel, output signals of other channels are replaced, and time delays between the other channels and the reference channel can be measured one by one, so that the consistency of all channels of the whole frequency point is obtained.
The delay between channels of the simulator is difficult to be absolutely 0ns, and the measurement result is influenced by factors such as the power resolution of the used frequency spectrograph and the stability of the radio frequency signal output by the simulator. For a frequency spectrograph with power measurement resolution of 0.01dB, the measurement precision of the delay among channels can be approximate to 0.01ns by combining different frequency point frequencies.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (4)
1. A method for measuring consistency between channels of a navigation simulator based on signal amplitude-phase characteristics is characterized by comprising the following steps:
selecting a single carrier signal of any frequency point of a simulator navigation system, and independently measuring the peak level of any two channels, wherein the peak level requirements of the two channels are consistent;
simultaneously outputting two channel signals, and measuring the level of a synthesized peak value; and comparing the synthesized peak value level with the single peak value level, judging whether the amplitude added value of the synthesized signal is 6.02dB, if not, acquiring a delayed phase difference according to the level difference value, and acquiring the delay time between two channels according to the phase difference.
2. The method of claim 1, wherein when the difference is not 6.02dB, the phase difference θ is obtained by performing an inverse calculation based on the amplitude increase of the composite signal:
3. The method of claim 2, comprising: calculating to obtain the delay time delta t between channels according to the phase difference theta;
4. the method of claim 1 wherein if the composite signal amplitude is increased by 6.02dB, the delay between the two channels is 0ns.
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