Inter-channel Consistency Measurement Method of Navigation Simulator Based on Signal Amplitude and Phase Characteristics

Abstract

The present invention provides a method for measuring the consistency between channels of a navigation simulator based on the amplitude-phase characteristics of signals. A single-carrier signal at any frequency point in the navigation system of the simulator is selected, and the peak levels of the signals of any two channels and the peak level of the synthesized signal are measured respectively. The synthesized peak level is compared with the single peak level, and the delayed phase difference is calculated based on the difference, and then the delay time between the two channels is calculated. When the delay between the two channels is 0 ns, the peak level of the synthesized signal increases by 6.02 dB compared with the single peak. The advantages are as follows: Measurement can be carried out by outputting a single-carrier signal, which is not limited by the modulation method adopted by the navigation signal; The accuracy of measuring the channel delay by using the peak level is high, and the measurement uncertainty is smaller than that of the original method, providing a more reliable basis for the measurement of the simulator.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation, and particularly to a method for measuring the consistency between channels of a navigation simulator based on the amplitude-phase characteristics of signals. Background Art

[0002] In the process of scientific research and application related to satellite navigation, relying solely on a Global Navigation Satellite System (GNSS) receiver (hereinafter referred to as "receiver") to receive navigation satellite signals is affected by many uncontrollable factors such as the number of visible satellites, weather, and electromagnetic environment, resulting in a reduction in the progress and efficiency of scientific research and verification work. Moreover, due to conditions, it is impossible to obtain diverse navigation satellite state scenarios to meet the requirements. Therefore, using a GNSS signal simulator to simulate various navigation satellite signals has become the first choice. A GNSS signal simulator (hereinafter referred to as "simulator") is a signal generator of the GNSS system, which can provide global navigation satellite system signal simulation according to the conditions of a moving carrier, and accurately simulate and generate GNSS satellite signals that a carrier can receive. The satellite constellations include GPS, GLONASS, GALILEO, BDS, etc., and can be used in all aspects of the research, production, and metrology processes of GNSS receivers, and can measure and identify the acquisition, tracking, and measurement accuracy of receivers. It is a key metrological instrument in the calibration process of GNSS receivers.

[0003] Currently, the simulators on the market are mainly used for receiver calibration and its method research, and are also applied to the calibration work of various receivers in the future (including high-dynamic and high-sensitivity receivers), accurately measuring and evaluating receiving devices in development, qualification review, and certification, reducing or completely eliminating the high costs of on-site measurement, and getting rid of the limitations of application in the actual environment. At the same time, it is also used for the measurement and research of the internal delay of receivers. The measurement of this index is the basis of precise time transfer and its research. Most simulator products are produced by foreign manufacturers (such as brands like Spirent), and their products have relatively high indicators and advanced performance. Many domestic manufacturers already have the ability to independently research and produce simulators, and the scale of independent research and production is continuously expanding, and the technical level is continuously improving.

[0004] In view of the current situation of the development of satellite navigation systems, it is required that the navigation simulator can generate navigation signals with multiple frequencies, multiple systems, and multiple modulation formats. This requires that inside the simulator, multiple modules are used to generate various signals and then superimposed uniformly. Due to differences in circuit parameters, clock transmission delays, phases, as well as the phase non-linearity effect and group delay of the radio frequency unit varying with frequency and environment, the channel consistency of signal simulation has become an important issue affecting the signal simulation accuracy. Even if all modules use a unified clock and the same structure and devices, however, due to the differences between devices and the problem of late characteristic drift occurring after a period of use of the devices, it is difficult to completely solve the problem of channel consistency in signal simulation between devices.

[0005] One channel of the simulator simulates one satellite, and the consistency between internal channels is an important technical index. The channel consistency requires that the initial states of multiple channels at the same frequency point are consistent under the same conditions. At the signal level, it is manifested as a delay of 0. If there is a delay in the initial state of each channel, as a systematic error, it will affect the entire simulation scenario and thus affect the positioning of the receiver.

[0006] The traditional method for measuring the consistency between channels is to input the 1PPS signal output by the simulator into an oscilloscope as a trigger signal, and at the same time use another channel of the oscilloscope to measure the BPSK signals output by different channels of the simulator. Use the oscilloscope to measure the time delay from the turning point of the BPSK signal to 1pps, compare the time differences between different channels (satellites) and the rising edge of 1pps, and calculate the channel consistency error. The limitation of this method is that the "turning point" of the actual modulation signal is not a zero-crossing point, but a curve with ups and downs, and it is impossible to find a unified time delay point, with a large uncertainty, and it can only be verified at the ns level. In addition, this method can only measure signals modulated by BPSK at the navigation frequency point and cannot measure signals using other modulation methods, reflecting the problem of large limitations of the existing measurement methods.

[0007] To adapt to different industries and different application fields, the simulator needs to have the function of outputting navigation signals with multiple systems and multiple frequency points. According to the definitions of the ICDs of each system, the modulation formats of navigation signals with different systems and different frequency points are not the same, and there are various modulation formats such as BPSK, QPSK, and BOC modulation. Especially with the introduction and application of new-generation simulators, the signal modulation method is different from that of the old generation. The navigation signals of the new generation more often use QPSK and BOC modulation. However, the existing calibration method for the consistency between channels of the simulator only applies to signals modulated by BPSK.

[0008] Figure 1 This is a screenshot of the measurement results for calibrating the consistency between channels of the simulator. The picture shows the positional relationship between the turning points of the BPSK signals output separately by the four channels of the simulator and the rising edge of the 1PPS signal of the simulator. At this time, the horizontal scale of the digital oscilloscope is relatively large.Figure 2 For Figure 1 Figure 1 is an enlarged view of the signal inversion point of four channels. At this time, the horizontal scale is 10 ns / div. Figure 2 It can be seen from Figure 2 that the signal inversion point is not a zero-crossing point, but a signal with a small amplitude. It is difficult to find the true zero-crossing point, resulting in a large uncertainty in the measurement result.

[0009] Thus, the problems of the existing technology are as follows:

[0010] (1) It can only measure the navigation signal modulated by BPSK, and cannot measure the inter-channel consistency of navigation signals with other modulation methods, with great limitations.

[0011] (2) From the actual measurement results, the inversion point used in the existing technology to measure the BPSK modulated signal is not a signal point, but a fluctuating zero-crossing signal. There is a large uncertainty in measuring the inversion point, resulting in inaccurate calibration results, and its uncertainty is of the order of ns.

[0012] Through the above two problems, it can be clearly seen that the existing calibration method for the inter-channel consistency of the simulator has low measurement accuracy and is difficult to truly reflect the inter-channel consistency of the high-precision simulator.

[0013] Therefore, how to provide a method for measuring the inter-channel consistency of satellite navigation simulators applicable to multiple modulation methods has become an urgent problem to be solved. SUMMARY OF THE INVENTION

[0014] Aiming at the limitations of the current calibration method for the inter-channel consistency of the simulator, the present invention provides a method for measuring the inter-channel consistency of a navigation simulator based on the amplitude-phase characteristics of the signal, which solves the problems of the limitation of the BPSK modulated signal and the low measurement accuracy.

[0015] To achieve the above object, the technical solution of the present invention provides a method for measuring the inter-channel consistency of a navigation simulator based on the amplitude-phase characteristics of the signal, including: selecting a single-carrier signal at any frequency point of the navigation system of the simulator, separately measuring the peak levels of any two channels, and the peak levels of these two channels are required to be the same. At the same time, output the signals of the two channels and measure the peak level of the composite signal; compare the composite peak level with the single peak level, and determine whether the increase in the amplitude of the composite signal is 6.02 dB. If not, obtain the delayed phase difference according to the level difference, and obtain the delay time between the two channels according to the phase difference.

[0016] As a preference of the above technical solution, preferably, when the difference is not 6.02 dB, the phase difference θ is calculated by inverse calculation according to the increase in the amplitude of the composite signal Δ':

[0017]

[0018] Among them, the unit of θ is radian.

[0019] As an optimization of the above technical solution, preferably, the inter-channel delay time Δt is calculated according to the phase difference θ;

[0020]

[0021] As an optimization of the above technical solution, preferably, if the increase value of the synthesized signal amplitude is 6.02 dB, the delay between the two channels is 0 ns.

[0022] The advantages of the invention are as follows: Measurement can be carried out as long as a single-carrier signal can be selected for output, without being restricted by the modulation method adopted by the navigation signal; By utilizing the characteristics of the phase and amplitude of the single-carrier signal, there is no need to find the turning point of the modulation signal. By reading the peak level of the single-carrier signal displayed on the spectrum analyzer and according to the calculation method of the present invention, the delay between channels can be calculated, and the uncertainty is better than 10 ps. Since the peak level is used to calculate the delay, the uncertainty of the measurement of the inter-channel consistency of the simulator is reduced, the accuracy is high, the reference value is large, and a more reliable basis is provided for debugging. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a screenshot of the measurement result of calibrating the inter-channel consistency in the prior art related to the present invention.

[0025] Figure 2 For Figure 1 It is an enlarged view of the turning point of the channel signal in

[0026] Figure 3 It is a flowchart of the measurement process provided by the technical solution of the present invention.

[0027] Figure 4 It is a connection block diagram of the instrument for measuring the inter-channel consistency of the simulator based on the single-carrier signal in the embodiment of the present invention.

[0028] Figure 5 It is the situation measured by the spectrum analyzer when measuring the single-carrier signal output by a single channel of the navigation signal at the same frequency point by applying the method of the present invention.

[0029] Figure 6This is the case of measuring the single-carrier signals simultaneously output by two channels of a navigation signal at the same frequency point using a spectrum analyzer by applying the method of the present invention. Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Now, the technical solutions of the present invention will be described in conjunction with the embodiments. Figure 3 This is a schematic flowchart provided for the embodiments of the present invention, as Figure 3 shown:

[0032] Step 101: Set the initial state of the satellite navigation simulator.

[0033] This includes setting the simulator to a static scenario, fixing the pseudo-range between the satellite and the carrier, and selecting a single-carrier signal at any frequency point of the navigation system.

[0034] Step 102: Measure the peak levels of Channel 1 and Channel 2 respectively.

[0035] The simulator outputs the satellite channel signal at any frequency point, and uses a spectrum analyzer to measure the peak level P0 of the signal in Channel 1. Keeping the simulation settings of the simulator unchanged, switch to the other Channel 2, and use a spectrum analyzer to measure the peak level P0' of Channel 2. Determine whether the peak levels of the signals in the two channels are equal, that is, P0 = P0'. If the peak levels of the two channels are different, adjust any one of the two peak levels so that the peak levels of the two channels are equal.

[0036] Step 103: Measure the combined peak level P1 of the combined signal after the two signals are combined.

[0037] Specifically, the simulator simultaneously outputs the signals of the two channels in Step 102, and uses a spectrum analyzer to measure the combined peak level of the combined signal.

[0038] Step 104: Calculate the peak level difference Δ'.

[0039] Specifically, the peak level difference is: the difference between the combined peak level of the combined signal and the peak level of the single-channel signal.

[0040] Step 105: Determine whether the peak level difference is 6.02 dB. If so, it proves that the delay between the two channels is 0 ns; otherwise, execute Step 106.

[0041] Specifically, the signals of Channel 1 and Channel 2 are superimposed to obtain the theoretical superimposed value. Since the two synthesized signals are sine wave signals with the same amplitude and the same frequency, and the phase difference is θ, the center frequency of the synthesized signal will not change, and only the signal level and phase will change, as shown in the following formula:

[0042]

[0043] In actual situations, the frequency of the synthesized signal does not change, and the amplitude changes with the phase difference. For the navigation simulator, under ideal conditions, the consistency delay between channels for satellites with the same frequency point and the same state is 0 ns, that is, the phase difference θ is 0.

[0044] The peak levels of the single-carrier signals of the two channels are equal, that is, P0 = P0'. If the delay between channels is 0 ns, according to the above formula, the amplitude of the two synthesized signals is twice that of one signal. When the amplitude is converted to logarithmic (dB) representation, the increased value ΔP of the amplitude of the two synthesized signals compared to the single-channel signal is: ΔP = 20log 2 = 6.02 dB.

[0045] Conversely, in step 105, if the peak level of the two synthesized signals measured by the spectrum analyzer is 6.02 dB greater than the peak level of the single-channel signal, it proves that the delay between the two channels that simultaneously output single-carrier signals at this frequency point of the simulator is 0 ns, and the measurement is completed.

[0046] Step 106: Calculate the phase difference θ according to the peak level difference Δ'.

[0047] Specifically,

[0048] where the unit of θ is radians.

[0049] Step 107: Calculate the delay time Δt by back-calculating according to the phase difference θ.

[0050] f is the nominal value of the center frequency of the single-carrier signal output by the simulator.

[0051] Figure 4 This is the instrument connection block diagram for the method of measuring the consistency between channels of the simulator proposed by the present invention. Before measurement, the simulator and the spectrum analyzer need to be powered on and preheated for half an hour, and the RF signal output terminal of the simulator is connected to the signal input terminal of the spectrum analyzer.

[0052] In the channel consistency measurement method provided based on the technical solution of the present invention, the satellite navigation simulator simulates a static scenario where the pseudo-ranges of the satellites and the carrier are fixed. The modulation signal is turned off to make the signal output a single carrier. First, 1 satellite is simulated, and the peak level is measured. Then, 1 more satellite is added, and the change value of the signal peak after superposition is measured. The phase difference and delay are calculated. Switching the satellites in different channels for superposition can verify the delays of the satellites in other channels, thereby obtaining the delays between all the satellites in the frequency band.

[0053] Now, a specific embodiment is used to illustrate the method of the present invention. In this embodiment, the GSS9000 simulator of Spirent Company imported from abroad is tested and verified, and the spectrum analyzer of Rohde & Schwarz Company of Germany is selected as the measurement device.

[0054] The GPS L1 frequency band is selected as the measurement signal, with a frequency of 1.57542 GHz and a period of approximately 0.63475 ns. All error models are turned off, and a static scenario with fixed pseudo-ranges of satellites and the carrier is set. The simulator outputs a single-star, single-channel, single-carrier signal, and the peak level P0 of the signal measured by the spectrum analyzer is -58.10 dBm, as shown in the appendix Figure 5 shown. Switching to the satellite signal of another channel, the peak level P'0 is also -58.10 dBm, and the amplitudes of the two-channel signals are consistent.

[0055] The output of the simulator is changed to a two-channel satellite single carrier, and other conditions remain unchanged. The actually measured peak level P1 of the composite signal is -52.08 dBm, as shown in the appendix Figure 6 shown.

[0056] Change value of the peak level: ΔP = P1 - P0 = -52.08 dBm - (-58.10 dBm) = 6.02 dB.

[0057] The measurement results are consistent with the theoretical data when the delay is 0 ns, proving that there is no delay in the output signals of the two channels. According to this method, keeping one channel unchanged as the reference channel and replacing the output signals of other channels, the time delays between other channels and the reference channel can be measured one by one, thereby obtaining the consistency of all channels in the entire frequency band.

[0058] It is very difficult to achieve an absolute 0 ns delay between the channels of the simulator, and the measurement results will be affected by factors such as the power resolution of the spectrum analyzer used and the stability of the RF signal output by the simulator. For a spectrum analyzer with a power measurement resolution of 0.01 dB, combined with the frequencies of different frequency bands, the measurement accuracy of the inter-channel delay can be approximated to 0.01 ns.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the consistency between channels of a navigation simulator based on the amplitude-phase characteristics of signals, characterized in that, The method includes: Select a single-carrier signal at any frequency point of the simulator navigation system, and separately measure the peak levels of any two channels, where the peak levels of these two channels are required to be the same; Output the signals of the two channels simultaneously, and measure the combined peak level; compare the combined peak level with the single peak level to determine whether the increase in the amplitude of the combined signal is 6.02 dB. If not, obtain the delayed phase difference according to the level difference, and obtain the delay time between the two channels according to the phase difference; Wherein, when the difference is not 6.02 dB, the phase difference θ is obtained by back-calculation according to the increase in the amplitude of the combined signal: Wherein, the unit of θ is radian, and Δ' is the peak level difference; Further, the inter-channel delay time Δt is calculated according to the phase difference θ; Wherein, f is the nominal value of the center frequency of the single-carrier signal output by the simulator.

2. The method according to claim 1, wherein If the increase in the amplitude of the combined signal is 6.02 dB, the delay between the two channels is 0 ns.

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