CN115685262A - Consistency Measurement Method Between Channels of Navigation Simulator Based on Signal Amplitude and Phase Characteristics - Google Patents

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

Consistency measurement method between navigation simulator channels based on signal amplitude and phase characteristics

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 and phase characteristics.

Background technique

In the process of scientific research and application related to satellite navigation, the way of receiving navigation satellite signals only by relying on the Global Satellite System (GNSS) receiver (hereinafter referred to as "receiver") will be affected by factors such as the number of visible satellites, weather, and electromagnetic environment. Affected by many uncontrollable factors, such as scientific research and verification, the progress and efficiency of scientific research and verification work are reduced, and limited by conditions, it is impossible to obtain a variety of navigation satellite status scenarios to meet the needs. Therefore, the use of GNSS signal simulators to simulate various navigation satellite signals has become the first choice. GNSS signal simulator (hereinafter referred to as "simulator") is a GNSS system signal generator, which can provide GNSS signal simulation according to the condition of the moving carrier, and accurately simulate and generate GNSS satellite signals that the carrier can receive. Satellite constellations include GPS, GLONASS, GALILEO, BDS, etc., which can be used in all aspects of the R&D, production and measurement process of GNSS receivers. It can measure and identify the acquisition, tracking and measurement accuracy of receivers. key measuring instruments.

At present, the simulators on the market are mainly used for receiver calibration and method research, and will be applied to the calibration of various receivers (including high dynamic and high sensitivity receivers) in the future. The receiving equipment performs accurate measurement and evaluation, reducing or completely eliminating the high cost of on-site measurement, and getting rid of the limitation of application in the actual environment. At the same time, taking into account the measurement and research of the internal delay of the receiver, the measurement of this index is the basis of precision time transfer and its research. Most of the simulator products are produced by foreign manufacturers (such as Spirent and other brands), and their products have high indicators and advanced performance. Many domestic manufacturers already have the ability to independently develop and produce simulators, and the scale of independent research and development and production continues to expand, and the technical level continues to improve.

In view of the status quo of satellite navigation system development, it is required that the navigation simulator can generate navigation signals of multiple frequency points, multiple systems and multiple formats. This requires multiple modules to generate various signals inside the simulator, and then superimpose them uniformly. Due to differences in circuit parameters, clock transmission delay, and phase, as well as phase nonlinear effects and group delays of radio frequency units, although frequency and environment changes, the channel consistency of signal simulation has become an important issue that affects the accuracy of signal simulation. Even if each module adopts a unified clock and uses the same structure and devices, due to the differences between devices and the later characteristic drift of devices after a period of use, it is difficult to completely solve the channel consistency problem of signal simulation between devices.

One channel of the simulator simulates a satellite, and the consistency between internal channels is an important technical indicator. Channel consistency requires multiple channels at the same frequency to be consistent in the initial state under the same conditions. From the signal level, the delay is expressed as 0, if there is a delay in the initial state of each channel, it will affect the entire simulation scene as a system error, thereby affecting the receiver positioning.

The traditional method of measuring consistency between channels is to input the 1PPS signal output by the simulator to the oscilloscope as a trigger signal, and at the same time use another channel of the oscilloscope to measure the BPSK signals of different channels output by the simulator, and use the oscilloscope to measure the BPSK signal flip point to 1pps. Delay, compare the time difference between different channels (satellites) and the rising edge of 1pps, and calculate the channel consistency error. The limitation of this method is that the "turnover point" of the actual modulated signal is not a zero-crossing point, but a curve, and it fluctuates up and down. It is impossible to find a unified delay point. The uncertainty is large and can only be on the order of ns verify. In addition, this method can only measure signals modulated by BPSK at the navigation frequency point, and cannot measure signals using other modulation methods, which reflects the problem of large limitations of existing measurement methods.

In order to adapt to different application fields in different industries, the simulator needs to have multi-system multi-frequency point navigation signal output function. According to the definition of ICD of each system, the navigation signal modulation methods of different systems and different frequency points are not the same, such as BPSK, QPSK, BOC modulation And many other modulation methods, especially with the advent and application of the new system simulator, the signal modulation method is different from the old system, and the navigation signals of the new system mostly use QPSK and BOC modulation. However, existing simulator channel-to-channel coherence calibration methods are only suitable for BPSK-modulated signals.

Figure 1 is a screenshot of the measurement results of the existing method to calibrate the consistency between the channels of the simulator. The picture shows the positional relationship between the flip point of the BPSK signal output separately from the four channels of the simulator and the rising edge of the simulator 1PPS signal. At this time, the level of the digital oscilloscope Larger scale. Figure 2 is an enlarged view of the signal inversion points of the four channels in Figure 1, and the horizontal scale is 10 ns/div at this time. 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 real zero-crossing point, which leads to greater uncertainty in the measurement results.

Thereby embodying the problem of prior art is:

(1) Only BPSK-modulated navigation signals can be measured, and the inter-channel consistency of navigation signals of other modulation methods cannot be measured, which is very restrictive.

(2) Judging from the actual measurement results, the inversion point used to measure the BPSK modulation signal in the prior art is not a signal point, but a fluctuating zero-crossing signal. There is a large uncertainty in the measurement of the inversion point, which leads to calibration The result is not accurate, and its uncertainty is on the order of ns.

Through the above two points, it can be clarified that the measurement accuracy of the existing consistency calibration method between simulator channels is not high, and it is difficult to truly reflect the consistency between channels of high-precision simulators.

So how to provide a consistency measurement method between satellite navigation simulator channels that can be applied to multiple modulation modes has become an urgent problem to be solved.

Contents of the invention

Aiming at the limitations of current simulator channel consistency calibration methods, the present invention provides a navigation simulator channel consistency measurement method based on signal amplitude and phase characteristics, which 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 the consistency between channels of a navigation simulator based on signal amplitude and phase characteristics, including: selecting a single carrier signal at any frequency point of the simulator navigation system, and measuring any two channels separately Peak level, the peak level requirements of the two channels are consistent. Simultaneously output two-channel signals, measure the peak level of the composite signal; compare the composite peak level with the single peak level, and judge whether the amplitude increase of the composite signal is 6.02dB, if not, obtain it according to the level difference Delayed phase difference, the delay time between the two channels is obtained according to the phase difference.

As an optimization of the above technical solution, preferably, when the difference is not 6.02dB, the phase difference θ is obtained by inverse calculation according to the amplitude increase value Δ' of the composite signal:

其中，θ的单位为弧度。

Among them, the unit of θ is radian.

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

As a preference of the above technical solution, preferably, if the composite signal amplitude increase value is 6.02dB, the delay between the two channels is 0 ns.

The advantage of the invention is: as long as the single-carrier signal can be selected to be output, the measurement can be carried out without being restricted by the modulation method adopted by the navigation signal; by using the characteristics of the phase-amplitude characteristics of the single-carrier signal, there is no need to find the flip point of the modulation signal, and by reading The spectrum analyzer displays the peak level of the single carrier signal, 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 consistency measurement between the simulator channels is reduced, the accuracy is high, and the reference value is large, which provides a more reliable basis for debugging.

Description of drawings

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 that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are the For some embodiments of the present invention, those skilled in the art can also obtain other drawings based on these drawings without any creative effort.

FIG. 1 is a screenshot of the measurement results of the consistency between calibration simulator channels in the prior art related to the present invention.

FIG. 2 is an enlarged view of the channel signal inversion point in FIG. 1 .

Fig. 3 is a flow chart of the measurement process provided by the technical solution of the present invention.

Fig. 4 is a connection block diagram of the consistency measuring instrument between simulator channels based on the single carrier signal in the embodiment of the present invention.

Fig. 5 is the situation of measuring with a spectrum analyzer when the method of the present invention is used to measure the single channel output single carrier signal of the navigation signal at the same frequency point.

Fig. 6 is the situation of measuring with a spectrum analyzer when the method of the present invention is used to measure the same frequency point navigation signal and two channels simultaneously output a single carrier signal.

Detailed ways

In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The technical solution of the present invention is now described in conjunction with the embodiments. Fig. 3 is a schematic flow diagram provided by the embodiment of the present invention, as shown in Fig. 3:

Step 101, setting the initial state of the satellite navigation simulator.

Including, setting the simulator as a static scene, the pseudo-range between the satellite and the carrier is fixed, and selecting a single-carrier signal at any frequency point of the navigation system.

Step 102, measure the peak levels of channel 1 and channel 2 respectively.

The simulator outputs satellite channel signals at any frequency point, and uses a spectrum analyzer to measure the signal peak level P ₀ of channel 1. Keep the simulation settings of the simulator unchanged, switch to another channel 2, and use a spectrum analyzer to measure the peak level P ₀ ′ of channel 2. It is judged whether the signal peak levels of the two channels are equal, that is, P ₀ =P ₀ ′. If the peak levels of the two channels are different, adjust either level of the two peak levels to make the peak levels of the two channels equal.

Step 103. Measure the composite peak level P ₁ of the composite signal after the two signals are composited.

Specifically, the simulator simultaneously outputs the signals of the two channels in step 102, and uses a spectrum analyzer to measure the peak level of the synthesized signal.

Step 104, calculating the peak level difference Δ'.

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.

Step 105 , judging whether the peak level difference is 6.02 dB, if so, prove that the delay between the two channels is 0 ns, otherwise, execute step 106 .

In detail, the two signals of channels 1 and 2 are superimposed to obtain a theoretical superposition value. Since the two sine wave signals of the same amplitude and frequency of the two synthesized signals have a phase difference of θ, the center frequency will not change after the signal is synthesized, and only the signal level and phase will change, as shown in the following formula:

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

The peak levels of the two-channel single-carrier signals are equal, that is, P ₀ =P ₀ ′, if the delay between channels is 0ns, according to the above formula, the amplitude of the two-channel composite signal is twice that of the one-channel signal, and the amplitude is converted into logarithm (dB ) indicates that the amplitude increase value ΔP of the two-way composite signal compared with the single-way signal is: ΔP=20log 2=6.02dB.

Conversely, in step 105, if the peak level of the two synthetic signals measured by a spectrum analyzer is 6.02dB greater than the peak level of the single signal, it proves that the simulator simultaneously outputs the delay between the two channels of the single carrier signal at this frequency 0ns, the measurement ends.

Step 106. Calculate the phase difference θ according to the peak level difference Δ′.

specific,

其中，θ的单位为弧度。

Among them, the unit of θ is radian.

Step 107, inversely calculating the delay time Δt according to the phase difference θ.

f为模拟器输出单载波信号的中心频率标称值。

f is the nominal value of the center frequency of the single carrier signal output by the simulator.

Fig. 4 is the instrument connection block diagram of the method for measuring the consistency between simulator channels proposed by the present invention. Before the measurement, the simulator and the spectrum analyzer need to be turned on for half an hour to warm up, and the radio frequency signal output of the simulator is connected to the spectrum analyzer signal input. catch.

In the channel consistency measurement method provided based on the technical solution of the present invention, the satellite navigation simulator simulates a static scene, the pseudo-range of the satellite and the carrier is fixed, the modulation signal is turned off so that the signal outputs a single carrier, and one satellite is first simulated to measure the peak level. Add another satellite, measure the signal peak change value after superimposition, and calculate the phase difference and delay. Switching the superimposed different channel satellites can verify the delay of other channel satellites, so as to obtain the delay between all channel satellites in the frequency point.

Now use a specific embodiment to illustrate the inventive method, and the present embodiment carries out experimental verification to the GSS9000 simulator of Spirent Company imported abroad, and what measuring equipment selects is the spectrum analyzer of German R&S Company.

Select the GPSL1 frequency point as the measurement signal, the frequency is 1.57542GHz, and the period is about 0.63475ns. Close all error models, set a static scene with a fixed pseudo-range between the satellite and the carrier, and the simulator outputs a single-satellite, single-channel, and single-carrier signal, and measure it with a spectrum analyzer The signal peak level P ₀ is -58.10dBm, as shown in Fig. 5 . Switching to another channel satellite signal, the peak level P′ ₀ is also -58.10dBm, and the signal amplitudes of the two channels are consistent.

Change the output of the simulator to dual-channel satellite single-carrier, and keep the others unchanged. The actual measured peak level P ₁ of the synthesized signal is -52.08dBm, as shown in Figure 6.

Peak level change value: ΔP=P ₁ -P ₀ =-52.08dBm-(-58.10dBm)=6.02dB.

The measurement results are consistent with the theoretical data when the delay is 0ns, which proves that the output signals of the two channels have no delay. According to this method, keeping one channel unchanged, using it as a reference channel, and replacing the output signals of other channels, the time delay between other channels and the reference channel can be measured one by one, so as to obtain the consistency of all channels at the entire frequency point.

It is difficult for the inter-channel delay of the simulator to be absolutely 0 ns, 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 0.01dB, combined with different frequency points, the measurement accuracy of the inter-channel delay can be approximately 0.01ns.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting 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: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (4)

1. a method for measuring consistency between navigation simulator channels based on signal amplitude and phase characteristics, it is characterized in that said method comprises: Select a single carrier signal at any frequency point of the simulator navigation system, and measure the peak levels of any two channels separately, and the peak levels of the two channels are required to be consistent; Simultaneously output two-channel signals to measure the composite peak level; compare the composite peak level with the single peak level to determine whether the composite signal amplitude increase value is 6.02dB, if not, obtain the delay according to the level difference The phase difference of , and the delay time between the two channels is obtained according to the phase difference. 2. The method according to claim 1, characterized in that, when the difference is not 6.02dB, the phase difference θ is obtained by inverse calculation according to the increase value of the composite signal amplitude:

Among them, the unit of θ is radian. 3. The method according to claim 2, characterized in that it comprises: calculating the inter-channel delay time Δt according to the phase difference θ;

4. The method according to claim 1, wherein if the amplitude increase value of the composite signal is 6.02dB, the delay between the two channels is 0ns.

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