CN113237493B - Method, system and device for predicting electromagnetic interference effect of navigation terminal - Google Patents
Method, system and device for predicting electromagnetic interference effect of navigation terminal Download PDFInfo
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- CN113237493B CN113237493B CN202110514692.1A CN202110514692A CN113237493B CN 113237493 B CN113237493 B CN 113237493B CN 202110514692 A CN202110514692 A CN 202110514692A CN 113237493 B CN113237493 B CN 113237493B
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Abstract
The invention discloses a method, a system and a device for predicting the electromagnetic interference effect of a navigation terminal, wherein the method comprises the following steps: when the interference signal received by the navigation terminal is in-band interference, acquiring an in-band interference signal and an antenna receiving signal; determining a first multi-frequency effect model according to the antenna receiving signal and the in-band interference signal; when the interference signal received by the navigation terminal is out-of-band interference, acquiring the out-of-band interference signal and an antenna receiving signal; determining a second multi-frequency effect model according to the antenna receiving signal and the out-of-band interference signal; when the interference signal received by the navigation terminal is in-band interference and out-of-band interference, determining a third multi-frequency effect model according to the first multi-frequency effect model and the second multi-frequency effect model; predicting according to the third multi-frequency effect model, and determining the tracking state of a satellite in the navigation terminal under the electromagnetic interference; the tracking states include stable tracking and lost states. The invention can effectively predict the tracking state of the satellite in the navigation terminal under the in-band and out-band multi-frequency electromagnetic interference.
Description
Technical Field
The invention relates to the technical field of electromagnetic environment effect test and evaluation, in particular to a method, a system and a device for predicting an electromagnetic interference effect of a navigation terminal.
Background
With the continuous development of electronic information equipment, electromagnetic signals of various patterns are mutually overlapped in time domain, frequency domain, space domain and energy to form a complex electromagnetic environment with dense distribution and dynamic alternation, the normal work of an information system and electronic equipment is hindered from different layers, and the use efficiency of frequency equipment is obviously influenced. Satellite navigation systems have gradually penetrated into various fields as boosters for economic development and multipliers for military strength, and become indispensable space infrastructures. Not to be neglected, satellite navigation systems have natural vulnerabilities. The performance degradation and the loss of the positioning function of the navigation system can be caused by the reduction of the number of constellation satellites, the change of the earth meteorological system and the strong electromagnetic signal interference from the space. The key factor determining the safety of the satellite navigation system is the complex electromagnetic environment. Due to the nonlinear effects of the radio frequency transmitter, harmonic components of the electromagnetic signals may fall within the frequency band of the satellite navigation signals, creating in-band interference to the navigation terminal. For out-of-band interference with large amplitude and strong energy, even if the out-of-band interference falls outside the processing frequency band of the navigation terminal, the out-of-band interference can also leak through a pre-filter of the navigation terminal, so that supersaturation of a radio frequency front end is caused to generate a blocking effect. In the big background of complex electromagnetic environment, it is a trend to study the influence of multi-frequency interference on a satellite navigation system.
At present, researchers at home and abroad have conducted extensive research aiming at the problem that a navigation system is easy to be interfered by electromagnetic waves. Keithamrmstrong points out that the traditional EMC test method is not enough to explain the electromagnetic sensitivity of the equipment, and proposes that the problem of simultaneous occurrence of radio frequency electromagnetic interference is not considered in the electromagnetic compatibility test. Duffy and a. orlandi et al tested the intermodulation effects in the reverberation room using the multi-frequency radiation sensitivity test. A continuous wave electromagnetic environment effect test platform is set up in Zhang Qinglong and Chen Asia of the university of army engineering, and the electromagnetic sensitivity threshold of a navigation terminal under single-frequency continuous wave interference is researched. The law of electromagnetic radiation sensitivity under the condition of multi-frequency continuous waves is researched by natural, natural and Zhao national beams. Based on an effect mechanism, Liwei researches an electromagnetic radiation effect modeling and predicting method of communication equipment under the combined action of in-band multi-frequency continuous waves, random noise and the two. However, for a specific test object, a satellite navigation terminal, further research on a multi-frequency electromagnetic interference prediction method is lacked.
Disclosure of Invention
The invention aims to provide a method, a system and a device for predicting the electromagnetic interference effect of a navigation terminal so as to effectively predict the tracking state of a satellite in the navigation terminal under the in-band and out-band multi-frequency electromagnetic interference.
In order to achieve the purpose, the invention provides the following scheme:
a method for predicting the electromagnetic interference effect of a navigation terminal comprises the following steps:
when the interference signal received by the navigation terminal is in-band interference, acquiring an in-band interference signal and an antenna receiving signal; determining a first multi-frequency effect model according to an antenna receiving signal and the in-band interference signal;
when the interference signal received by the navigation terminal is out-of-band interference, acquiring the out-of-band interference signal and an antenna receiving signal; determining a second multi-frequency effect model according to the antenna receiving signal and the out-of-band interference signal;
when the interference signal received by the navigation terminal is in-band interference and out-of-band interference, determining a third multi-frequency effect model according to the first multi-frequency effect model and the second multi-frequency effect model;
predicting according to the third multi-frequency effect model, and determining the tracking state of a satellite in the navigation terminal under electromagnetic interference; the tracking states include stable tracking and lost states.
Optionally, the predicting according to the third multi-frequency effect model to determine a tracking state of a satellite in the navigation terminal under electromagnetic interference specifically includes:
inputting the in-band interference signal and the out-of-band interference signal into the third multi-frequency effect model to obtain a suppression coefficient;
judging whether the pressing coefficient is larger than a preset threshold value or not to obtain a first judgment result;
if the first judgment result shows that the satellite in the navigation terminal is in the lost state, determining that the satellite in the navigation terminal is in the lost state; and if the first judgment result shows that the satellite in the navigation terminal continues to stably track, determining that the satellite in the navigation terminal continues to stably track.
Optionally, the third multi-frequency effect model is:
wherein S isioTo suppress the coefficient, PignIs an in-band interference signal, n is the number of in-band multi-frequency electromagnetic interference signals, PogmIs out of bandInterference signal, m is the number of out-of-band multi-frequency electromagnetic interference signals, PinIs an in-band threshold, PomOut-of-band threshold.
A system for predicting the effect of electromagnetic interference on a navigation terminal, comprising:
the navigation terminal comprises a first acquisition module, a second acquisition module and a control module, wherein the first acquisition module is used for acquiring an in-band interference signal and an antenna receiving signal when the interference signal received by the navigation terminal is in-band interference;
the first multi-frequency effect model determining module is used for determining a first multi-frequency effect model according to an antenna receiving signal and the in-band interference signal;
the second acquisition module is used for acquiring an out-of-band interference signal and an antenna receiving signal when the interference signal received by the navigation terminal is out-of-band interference;
a second multi-frequency effect model determining module, configured to determine a second multi-frequency effect model according to an antenna receiving signal and the out-of-band interference signal;
a third multi-frequency effect model determining module, configured to determine a third multi-frequency effect model according to the first multi-frequency effect model and the second multi-frequency effect model when an interference signal received by the navigation terminal is in-band interference and out-of-band interference;
the prediction module is used for predicting according to the third multi-frequency effect model and determining the tracking state of a satellite in the navigation terminal under the electromagnetic interference; the tracking states include stable tracking and lost states.
Optionally, the prediction module specifically includes:
a suppression coefficient determining unit, configured to input the in-band interference signal and the out-of-band interference signal into the third multi-frequency effect model to obtain a suppression coefficient;
the judging unit is used for judging whether the pressing coefficient is larger than a preset threshold value or not to obtain a first judging result;
a lost state determination unit, configured to determine that a satellite in the navigation terminal enters a lost state when the first determination result indicates yes;
and the stable tracking determining unit is used for determining that the satellite in the navigation terminal continues stable tracking when the first judgment result shows that the satellite is not stably tracked.
Optionally, the third multi-frequency effect model is:
wherein S isioTo suppress the coefficient, PignIs an in-band interference signal, n is the number of in-band multi-frequency electromagnetic interference signals, PogmFor out-of-band interference signals, m is the number of out-of-band multi-frequency electromagnetic interference signals, PinIs an in-band threshold, PomOut-of-band threshold.
An apparatus for predicting electromagnetic interference effect of a navigation terminal, comprising: the system comprises a first signal source, a second signal source, a navigation signal simulator, a directional coupler, a power divider, a radio frequency front-end module, a navigation terminal, an injection power monitoring frequency spectrograph, a radio frequency monitoring frequency spectrograph and a monitoring computer;
the first signal source, the second signal source and the navigation signal simulator are all connected with one end of the directional coupler, the first signal source is used for generating in-band interference, and the second signal source is used for generating out-of-band interference; the other end of the directional coupler is connected with one end of the power divider, the other end of the power divider is respectively connected with the injection power monitoring frequency spectrograph and the radio frequency front end module, and the injection power monitoring frequency spectrograph is used for observing the power of an interference signal injected into the radio frequency front end module; the radio frequency front end module is used for simulating an antenna of an active antenna to receive signals, the radio frequency front end module is also connected with a navigation terminal, the navigation terminal is also respectively connected with the monitoring computer and the radio frequency monitoring frequency spectrograph, and the monitoring computer is used for monitoring various states of the navigation terminal in real time; the monitoring computer is also connected with the navigation signal simulator.
Optionally, one or more first signal sources are provided, and one or more second signal sources are provided.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
according to the method, the system and the device for predicting the electromagnetic interference effect of the navigation terminal, the third multi-frequency effect model determined by the first multi-frequency effect model and the second multi-frequency effect model is used for predicting, so that the effective judgment of the satellite tracking state in the navigation terminal under the electromagnetic interference effect of in-band interference and out-of-band interference is realized.
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 embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flowchart of a method for predicting the electromagnetic interference effect of a navigation terminal according to the present invention;
FIG. 2 is a vector diagram of single frequency out-of-band interference;
FIG. 3 is a vector diagram of out-of-band dual-frequency interference and navigation signals;
FIG. 4 is a schematic diagram of a system for predicting the electromagnetic interference effect of a navigation terminal according to the present invention;
FIG. 5 is a diagram of a test configuration for dual frequency EMI;
FIG. 6 is a diagram of a single frequency EMI test configuration;
FIG. 7 is a diagram of a specific experimental configuration for dual-frequency EMI;
FIG. 8 is a diagram of a test configuration for tri-band EMI.
Description of the symbols:
1-a first signal source; 2-a second signal source; 3-a navigation signal simulator; 4-a directional coupler; 5-power divider; 6-radio frequency front end module; 7-injection power monitoring radio frequency instrument; 8-a navigation terminal; 9-radio frequency monitoring spectrometer; 10-a direct current voltage regulator; 11-monitoring computer.
Detailed Description
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 only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a method, a system and a device for predicting the electromagnetic interference effect of a navigation terminal so as to effectively predict the tracking state of a satellite in the navigation terminal under the in-band and out-band multi-frequency electromagnetic interference.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1, the method for predicting the electromagnetic interference effect of a navigation terminal provided by the present invention includes:
step 101: and when the interference signal received by the navigation terminal is in-band interference, acquiring the in-band interference signal and an antenna receiving signal.
Step 102: and determining a first multi-frequency effect model according to the antenna receiving signal and the in-band interference signal.
And when the signal received by the antenna is an in-band electromagnetic interference signal, determining a first multi-frequency effect model. When the interference signal faced by the navigation terminal is in-band interference, the non-linear phenomenon of the radio frequency front end is not obvious because the power of the in-band interference signal is low, and at this time, the antenna receives signals as follows:
r(t)＝s(t)+n(t)+Ji(t) (1)
where t is time, r (t) is antenna received signal, s (t) is power of navigation signal received by antenna, JiAnd (t) is the inband interference signal power, and n (t) is the sum of the noise floor of the environment and the noise of the devices inside the terminal.
Under the interference, the navigation signal is de-spread to obtain a carrier-to-noise ratio, and the carrier-to-noise ratio C/N after the navigation signal is de-spread0As shown in formula (2).
In the formula, C/N0Is the carrier to noise ratio; c is the carrier signal power, PsFor navigation signals, PiIs the interference signal power; ksThe processing gain of the navigation signal is related to parameters such as coherent integration time, navigation signal bandwidth and the like; s is a navigation signal, KiThe processing gain is the processing gain of the interference signal, and is related to factors such as coherent integration time, interference signal bandwidth, navigation signal line spectrum and frequency; n is a radical of0Is the noise power in Hz, the value of which is related to the noise temperature.
Suppose there are two in-band single frequency electromagnetic interference signals, denoted as J respectivelyi1(t) and Ji2(t), when the carrier-to-noise ratio value output by the correlator is the carrier-to-noise ratio threshold value, the satellite tracking of the tracking loop in the navigation terminal is lost, and when two single-frequency electromagnetic interference signals act respectively, the sensitivity threshold value under each single-frequency electromagnetic interference signal when the satellite tracking is lost can be calculated to be P according to the formula (3)i1And Pi2。
In the formula: (C/N)0)tIs a carrier to noise ratio threshold value, Pi1And Pi2For two in-band interfering signals of different frequencies, Ki1And Ki2Respectively the gains of the two interference signals in the correlation process.
When the two in-band single-frequency electromagnetic interference signals act simultaneously and the carrier-to-noise ratio value output by the correlator is the carrier-to-noise ratio threshold value, the satellite tracking of the tracking loop in the navigation terminal is lost at the moment, and the power of each single-frequency electromagnetic interference signal is P respectively when the satellite tracking is lost according to the formula (4)ig1And Pig2。
The combined type (3) and the formula (4) can obtain
Is simplified to obtain
Ki2Pig2+Ki2Pig2＝Ki1Pi1＝Ki2Pi2 (6)
Further simplification of
Similarly, when the satellite navigation terminal is simultaneously subjected to electromagnetic interference signals of multiple frequencies, the satellite navigation terminal can obtain
In the formula: siThe suppression coefficient is the suppression coefficient under the electromagnetic interference of the in-band multi-frequency. Equation (8) is a first multi-frequency effect model, which is an effect model under the in-band multi-frequency electromagnetic interference.
Step 103: and when the interference signal received by the navigation terminal is out-of-band interference, acquiring the out-of-band interference signal and an antenna receiving signal.
Step 104: and determining a second multi-frequency effect model according to the antenna receiving signal and the out-of-band interference signal.
And when the signal received by the antenna is the out-of-band electromagnetic interference signal, determining a second multi-frequency effect model. When the interference signal faced by the navigation terminal is out-of-band interference, the problem of abrupt change nonlinearity of the radio frequency front end of the terminal caused by the entering of a large signal can be explained by a limiter mechanism. When the antenna receives a signal of
r(t)＝s(t)+n(t)+Jo(t) (9)
Where r (t) is the antenna received signal, s (t) is the power of the pilot signal received by the antenna, Jo(t) is a beltThe external interference signal power, n (t), is the sum of the noise floor of the environment and the noise of the internal devices of the terminal.
r(t)＝s(t)+g(t) (10)
Wherein g (t) is Jo(t)+n(t)≈Jo(t), since the power of the noise signal is much lower than the power of the interference signal, the characteristics of the signal g (t) depend mainly on the interference signal Jo(t) ignoring the effect of noise n (t) for the purpose of facilitating subsequent formulation derivation.
In the formula, Jo(t) is an out-of-band interference signal, PoFor out-of-band interfering signal power, fsFor navigation signal frequency, foFor interfering with the signal frequency, UsFor navigation signal amplitude, UoIs the amplitude of the interfering signal. Then r (t) can be represented by formula (6).
r(t)＝Uscos(2πfst)+Uocos(2πfot) (12)
Due to the frequency selection effect of the terminal radio frequency front-end filter on the out-of-band signal, the actual signal can be expressed as the signal arriving at a sensitive device
r(t)＝AsUscos(2πfst)+AoUo cos(2πfot) (13)
In the formula, AsFor the filter to the frequency-selective coefficient of the navigation signal, AoThe frequency selection coefficient of the filter to the interference signal is obtained. When the out-of-band large signal enters the radio frequency front end of the terminal, A at the momentsUs/AoUo1, the relationship between the signal frequencies is shown as formula (14)
In the formula (f)dFor the difference between the frequencies of the pilot signal and the interfering signal, assume fs＞foI.e. exist
fs＝fd+fo (15)
From the signal vector diagram shown in fig. 2, a composite signal r can be calculatedo(t)：
ro(t)＝R1(t)cos(2πfot+θ)＝R1(t)cos[2π(fs-fd)t+θ] (16)
In the formula, R1And (t) is a combined signal, and theta is an included angle between the combined signal and the out-of-band interference signal.
Setting amplitude limiting amplitude value as UcThe system gain is K0When A issUs+AoUo＜UcWhile the amplitude of the output signal is K0AoUo(1+αcos2πfdt). When A issUs+AoUo＞UcWhile the output signal amplitude is UcOutput signal ro(t)' is
According to the first class of n-th order bessel theory, there is an expansion as follows.
In the formula, Jn(α) is a first class of nth order Bessel function, J0(α)≈1，J1(α) ≈ 0.5 α. n is the order of the Bessel function, the second term in equation (19) is expanded in conjunction with equation (20), and only the fundamental component is considered, as shown in equation (21).
It can be seen that the first term in equation (21) is the useful signal component, and further calculation yields the useful signal gain as shown in equation (22):
as can be seen from equation (22), when the outband interference signal acts on the terminal, the gain of the rf front end of the terminal is related to the power of the outband interference signal, the frequency-selecting coefficient of the terminal for the outband interference signal, and the amplitude limiting value of the terminal.
When the interference signal faced by the navigation terminal is an out-of-band dual-source electromagnetic interference signal, the signal received by the antenna at this time can be represented as
r(t)＝s(t)+n(t)+Jo1(t)+Jo2(t)≈s(t)+Jo1(t)+Jo2(t) (23)
In the formula: j. the design is a squareo1(t) and Jo2(t) are two out-of-band electromagnetic interference signals, respectively.
It is assumed that two out-of-band electromagnetic interference signals can be represented as
In the formula: po1And Po2Power, f, of two out-of-band electromagnetic interference signals, respectivelyo1And fo2Respectively, of two out-of-band electromagnetic interference signals, Uo1And Uo2The amplitudes of the two out-of-band electromagnetic interference signals, respectively. Considering the effect of the RF front-end filter, the signal actually arriving at the sensitive device can be expressed as
r(t)＝AsUscos(2πfst)+Ao1Uo1 cos(2πfo1t)+Ao2Uo2 cos(2πfo2t) (25)
In the formula: a. theo1And Ao2The frequency selection coefficients of the filter to the two out-of-band electromagnetic interference signals are respectively.
Firstly, a vector method is utilized to analyze a combined signal S of two interference signalso(t) as shown in FIG. 3.
The composite amplitude S of the interference signal can be calculatedo(t) and phase
As shown in equation (26).
In the formula: fa ═ fo2-fo1And fa is the angle between two interfering signals.
Further combining the interference signal with the desired signal, the final combined signal being r2(t)。
R2(t)＝{(AsUs)2+2AsUsSo(t)cos(2πfbt)+[So(t)]2}1/2 (27)
In the formula:
fbthe angle between the navigation signal and the combined signal of the two interference signals is shown. Similarly, when the amplitude of the superimposed signal is greater than the cutoff voltage UcAt this time, the output signal r2(t)' is
The second term of the above formula is developed according to Bessel theory only by considering the gain of the useful signal, and the gain can be obtained
Then gain of the desired signal can be obtained
The interference amplitude when the satellite tracking in the navigation terminal is lost is assumed to be U when the two out-of-band electromagnetic interference signals act simultaneouslyog1And Uog2When the two interference signals act independently, the interference amplitude when the satellite tracking in the navigation terminal is lost is Uo1And Uo2. When the satellite tracking is lost under the condition of out-of-band electromagnetic interference, the gain of the useful signal on the sensitive components should be equal, and then the combination formula (22) and the formula (31) can obtain the formula (32)
Further simplified and according to Pasval identity P ═ U2Per 2R, can be obtained by working up
Similarly, when the satellite navigation terminal is simultaneously subjected to a plurality of electromagnetic interference signals with out-of-band frequencies, the electromagnetic interference signals with the out-of-band frequencies can be obtained
Step 105: and when the interference signal received by the navigation terminal is in-band interference and out-of-band interference, determining a third multi-frequency effect model according to the first multi-frequency effect model and the second multi-frequency effect model.
The first multi-frequency effect model can be recorded as
In the formula: alpha is alphainWeighting coefficients for the effects of different in-band electromagnetic interference signals.
The second multi-frequency effect model can be written as
In the formula: alpha is alphaomWeighting coefficients for the effects of different in-band electromagnetic interference signals.
Then when the navigation terminal is faced with in-band and out-of-band multi-frequency electromagnetic interference, the effect coefficient of the tracking loop should be the sum of the effect weight coefficients of all electromagnetic interference signals, i.e. the effect weight coefficient
In the formula: sioThe suppression coefficient of the satellite tracking loss under the in-band and out-band multi-frequency electromagnetic interference is obtained. And actually, predicting by using a third multi-frequency effect model, namely determining a suppression coefficient according to in-band and out-band multi-frequency electromagnetic interference, and finally comparing the suppression coefficient with 1 to determine the tracking state of the satellite in the navigation terminal under the electromagnetic interference.
Step 106: predicting according to the third multi-frequency effect model, and determining the tracking state of a satellite in the navigation terminal under electromagnetic interference; the tracking states include stable tracking and lost states.
Wherein, step 106: the method specifically comprises the following steps:
and inputting the in-band interference signal and the out-of-band interference signal into the third multi-frequency effect model to obtain a suppression coefficient. Judging whether the pressing coefficient is larger than a preset threshold value or not to obtain a first judgment result; if the first judgment result shows that the satellite in the navigation terminal is in the lost state, determining that the satellite in the navigation terminal is in the lost state; and if the first judgment result shows that the satellite in the navigation terminal continues to stably track, determining that the satellite in the navigation terminal continues to stably track.
The third multi-frequency effect model is as follows:
wherein S isioTo suppress the coefficient, PignIs an in-band interference signal, n is the number of in-band multi-frequency electromagnetic interference signals, PogmFor out-of-band interference signals, m is the number of out-of-band multi-frequency electromagnetic interference signals, PinIs an in-band threshold, PomOut-of-band threshold.
For a given in-band and out-of-band multi-frequency electromagnetic interference signal, the sensitivity threshold is known to be P if each is radiated separatelyi1、Pi2、Pi3···Po1、Po2、Po3When in-band and out-of-band multi-frequency electromagnetic interference (power combination P)ig1、Pig2、Pig3···Pog1、Pog2、Pog3When acting on a navigation terminal at the same time, SioWhen the tracking loss reaches 1, the navigation terminal may lose the satellite tracking, and because the signal input into the navigation terminal generates intermodulation to cause energy loss, when the satellite tracking is lost, SioAnd may be greater than 1. On the contrary, if SioAnd when the tracking loss is less than 1, the tracking loss phenomenon of the navigation terminal can not occur.
As shown in fig. 4, a system for predicting electromagnetic interference effect of a navigation terminal includes:
a first obtaining module 401, configured to obtain an in-band interference signal and an antenna receiving signal when the interference signal received by the navigation terminal is in-band interference.
A first multi-frequency effect model determining module 402, configured to determine a first multi-frequency effect model according to the antenna receiving signal and the inband interferer signal.
A second obtaining module 403, configured to obtain an out-of-band interference signal and an antenna receiving signal when the interference signal received by the navigation terminal is out-of-band interference.
A second multi-frequency effect model determining module 404, configured to determine a second multi-frequency effect model according to the antenna receiving signal and the out-of-band interference signal.
A third multi-frequency effect model determining module 405, configured to determine a third multi-frequency effect model according to the first multi-frequency effect model and the second multi-frequency effect model when the interference signal received by the navigation terminal is in-band interference and out-of-band interference.
The prediction module 406 is used for predicting according to the third multi-frequency effect model and determining the tracking state of a satellite in the navigation terminal under the electromagnetic interference; the tracking states include stable tracking and lost states. The prediction module 406 specifically includes: a suppression coefficient determining unit, configured to input the in-band interference signal and the out-of-band interference signal into the third multi-frequency effect model to obtain a suppression coefficient; the judging unit is used for judging whether the pressing coefficient is larger than a preset threshold value or not to obtain a first judging result; a lost state determination unit, configured to determine that a satellite in the navigation terminal enters a lost state when the first determination result indicates yes; and the stable tracking determining unit is used for determining that the satellite in the navigation terminal continues stable tracking when the first judgment result shows that the satellite is not stably tracked.
Wherein the third multi-frequency effect model is:
wherein S isioTo suppress the coefficient, PignIs an in-band interference signal, n is the number of in-band multi-frequency electromagnetic interference signals, PogmFor out-of-band interference signals, m is the number of out-of-band multi-frequency electromagnetic interference signals, PinIs an in-band threshold, PomOut-of-band threshold.
As shown in fig. 5, the present invention provides a device for predicting electromagnetic interference effect of a navigation terminal, including: the device comprises a first signal source 1, a second signal source 2, a navigation signal simulator 3, a directional coupler 4, a power divider 5, a radio frequency front end module 6, a navigation terminal 8, an injection power monitoring frequency spectrograph 7, a radio frequency monitoring frequency spectrograph 9, a direct current voltage stabilizing source 10 and a monitoring computer 11.
The first signal source 1, the second signal source 2 and the navigation signal simulator 3 are all connected with one end of a directional coupler 4, the first signal source 1 is used for generating in-band interference, and the second signal source 2 is used for generating out-of-band interference; the other end of the directional coupler 4 is connected with one end of the power divider 5, the other end of the power divider 5 is respectively connected with the injection power monitoring spectrometer 7 and the radio frequency front end module 6, and the injection power monitoring spectrometer 7 is used for observing the power of an interference signal injected into the radio frequency front end; the radio frequency front-end module 6 is used for simulating an antenna receiving signal of an active antenna, the radio frequency front-end module 6 is further connected with a navigation terminal 8, the navigation terminal 8 is further connected with the monitoring computer 11 and the radio frequency monitoring frequency spectrograph 9 respectively, and the monitoring computer 11 is used for monitoring various states of the navigation terminal 8 in real time; the monitoring computer 11 is also connected to the navigation signal simulator 3.
In practical applications, as shown in fig. 6 to 8, one or more first signal sources 1 are provided, and one or more second signal sources 2 are provided. The first signal source 1 and the second signal source 2 may be vector signal sources or single-frequency signal sources. The vector signal source will be taken as an example below.
As shown in fig. 7, the prediction apparatus for electromagnetic interference effect of navigation terminal, that is, the test configuration diagram for dual-frequency electromagnetic interference, according to the present invention, the specific method of the prediction apparatus for electromagnetic interference effect of navigation terminal, provided by the present invention, includes: the device comprises two vector signal sources, a navigation signal simulator 3, a directional coupler 4, a power divider 5, a radio frequency front end module 6, a navigation terminal 8, an injection power monitoring frequency spectrograph 7, a radio frequency monitoring frequency spectrograph 9 and a monitoring computer.
The vector signal source, the vector signal source and the navigation signal simulator 3 are all connected with one end of a directional coupler 4, one vector signal source is used for generating in-band interference, and the other vector signal source is used for generating out-of-band interference; the other end of the directional coupler 4 is connected with one end of the power divider 5, the other end of the power divider 5 is respectively connected with the injection power monitoring spectrometer 7 and the radio frequency front end module 6, and the injection power monitoring spectrometer 7 is used for observing the power of an interference signal injected into the radio frequency front end; the radio frequency front-end module 6 is used for simulating an antenna receiving signal of an active antenna, the radio frequency front-end module 6 is further connected with a navigation terminal 8, the navigation terminal 8 is further connected with the monitoring computer and the radio frequency monitoring frequency spectrograph 9 respectively, and the monitoring computer is used for monitoring various states of the navigation terminal 8 in real time; the monitoring computer is also connected with the navigation signal simulator 3.
The effect test method of the single-frequency electromagnetic interference comprises the following steps:
generating a single-frequency or interference signal with a certain bandwidth by using a vector signal source, injecting the interference signal and a navigation signal generated by the navigation signal simulator 3 into the directional coupler 4+ the power divider 5, wherein one path of a signal output by the power divider 5 is injected into a radio frequency front end module 6 of a navigation terminal 8 and is used for simulating the receiving state of an active antenna, and the other path of the signal is connected with a frequency spectrograph through a radio frequency cable and is used for observing the power of the interference signal injected into the radio frequency front end; the radio frequency front end module 6 is connected with a navigation terminal 8, the navigation terminal 8 is connected with an upper monitoring computer through a network cable, real-time monitoring of various states of the navigation terminal 8 is achieved, a direct current voltage stabilizing source 10 is connected with the navigation terminal 8 through a power line, and the test configuration is shown in fig. 6.
And the radio frequency front-end module 6 and the navigation terminal 8 are adopted to simulate the navigation terminal 8 in the real use process.
The method for predicting the effect of the in-band and out-of-band dual-frequency electromagnetic interference comprises the following steps:
the method comprises the steps that a single-frequency signal or a narrow-band (or broadband) signal is respectively generated by two signal sources and is injected into a directional coupler 4+ a power divider 5 together with a navigation signal generated by a navigation signal simulator 3, wherein one path of the signal output by the power divider is injected into a radio frequency front-end module 6 of a navigation terminal 8 and is used for simulating the receiving state of an active antenna, and the other path of the signal is connected with a frequency spectrograph through a radio frequency cable and is used for observing the power of an interference signal injected into the radio frequency front-end; the radio frequency front end module 6 is connected with the navigation terminal 8, the navigation terminal 8 is connected with an upper monitoring computer through a network cable, real-time monitoring of various states of the navigation terminal 8 is achieved, and the test configuration is shown in fig. 7.
According to the method, a prediction model of the in-band and out-of-band multi-frequency electromagnetic radiation signal blocking interference effect of the navigation terminal 8 is established through an out-of-band large signal blocking mechanism and a calculation formula of an in-band related processing carrier-to-noise ratio, power combination change rules under different multi-frequency combinations are researched through in-band single-frequency and out-of-band single-frequency of the navigation terminal 8 and in-band and out-of-band multi-frequency electromagnetic interference tests, the test results show that model coefficients of the multi-frequency electromagnetic interference (including narrow-band interference and broadband interference) effect prediction models under different frequency combinations and different power combinations are all about 1, the absolute value of a prediction error is less than 3dB, and the effectiveness of the electromagnetic interference prediction model of the navigation terminal 8 under the in-band and out-of-band multi-frequency interference is verified. The in-band and out-band multi-frequency electromagnetic interference effect prediction is carried out on the navigation terminal 8 through the in-band and out-band multi-frequency electromagnetic interference effect model of the navigation terminal 8, and the method has the advantages of accuracy, convenience and quickness in prediction.
In order to verify the correctness of the established model, the invention takes a certain type of navigation terminal 8 as a test object, and single-frequency and multi-frequency electromagnetic interference effect tests are respectively carried out on the navigation terminal 8.
Such a carrier-to-noise ratio threshold exists in the internal channel of the navigation terminal 8: whenever the signal-to-noise ratio is less than this threshold, the loop loses the ability to stably track the weak signal. Because different radio frequency front-end circuits adopted by different navigation terminals 8 are different and baseband resolving algorithms are different, different navigation terminals 8 have different carrier-to-noise ratio threshold values, and the carrier-to-noise ratio threshold values of the navigation terminals 8 are determined through tests before the tests.
According to the test methods of fig. 6 and fig. 7, three groups of in-band and out-of-band dual-frequency interference signal combinations are selected for test verification, which are respectively as follows: the frequency combination of the first group of interference signals is 1510MHz (f 1) and 1561.1MHz (f 2); the frequency combination of the second group of interference signals is f 3-1605 MHz and f 4-1562.1 +/-1 MHz; the third group of interference signal frequency combination is 1515MHz for f5 and 1560.1 ± 0.2MHz for f 6. The test results are shown in tables 1, 2 and 3, where table 1 is a test validation table for the first set of dual-frequency emi, table 2 is a test validation table for the second set of dual-frequency emi, and table 3 is a test validation table for the third set of dual-frequency emi.
TABLE 1 test and verification table for first group of dual-frequency electromagnetic interference
TABLE 2 Experimental validation of the second set of dual frequency EMI
TABLE 3 Experimental validation of the third set of dual frequency EMI
According to the test methods of fig. 6 and 8, three groups of in-band and out-of-band tri-band interference signal combinations are selected for test verification, which are respectively as follows: the first group of interference signal is frequency combined as f1＝1523MHz、f21495MHz and f31559.4 MHz; the second group of interference signals is frequency combined into f4＝1638MHz、f51610MHz and f61561.5 MHz; the third group of interference signal frequency combination is f7＝1615MHz、f81562MHz and f91560.8 ± 1 MHz. The test results are shown in tables 4, 5 and 6, where table 4 is a first set of three-frequency emi test validation table, table 5 is a third set of two-frequency emi test validation table, and table 6 is a third set of three-frequency emi test validation table.
TABLE 4 first set of three-frequency EMI test and verification table
TABLE 5 second set of three-frequency EMI test and verification table
TABLE 6 test and verification table for the third group of three-frequency electromagnetic interference
From the above results, it can be seen that the effect coefficient S of the prediction model under the dual-frequency and tri-frequency electromagnetic interference under different frequency combinations, different bandwidths and different power intensitiesioThe prediction error is within +/-3 dB and meets the tolerance requirement specified by military standards, and the accuracy and the effectiveness of the model established by the invention are proved. This means that when the navigation terminal 8 is in a certain determined dual-frequency electromagnetic interference environment, the electromagnetic interference effect of the tracking loop of the navigation terminal 8 can be predicted by the pre-known single-frequency electromagnetic interference threshold.
The in-band interference and the out-of-band interference are taken as two typical electromagnetic interference modes, the electromagnetic interference effect of the in-band interference and the out-of-band interference on the navigation terminal is researched, a radio frequency electromagnetic interference prediction method is provided, and the method has great significance for further developing the electromagnetic interference effect prediction evaluation research of more style systems.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (4)
1. A method for predicting the electromagnetic interference effect of a navigation terminal is characterized by comprising the following steps:
when the interference signal received by the navigation terminal is in-band interference, acquiring an in-band interference signal and an antenna receiving signal; determining a first multi-frequency effect model according to an antenna receiving signal and the in-band interference signal; the first multi-frequency effect model is:
wherein S isiIs a first multi-frequency effect model, alphainEffect weight coefficients for different in-band electromagnetic interference signals;
when the interference signal received by the navigation terminal is out-of-band interference, acquiring the out-of-band interference signal and an antenna receiving signal; determining a second multi-frequency effect model according to the antenna receiving signal and the out-of-band interference signal; the second multi-frequency effect model is:
wherein S isoIs a second multi-frequency effect model, alphaomEffect weight coefficients for different in-band electromagnetic interference signals;
when the interference signal received by the navigation terminal is in-band interference and out-of-band interference, determining a third multi-frequency effect model according to the first multi-frequency effect model and the second multi-frequency effect model;
predicting according to the third multi-frequency effect model, and determining the tracking state of a satellite in the navigation terminal under electromagnetic interference; the tracking states include stable tracking and lost states; the predicting according to the third multi-frequency effect model to determine the tracking state of the satellite in the navigation terminal under the electromagnetic interference specifically comprises:
inputting the in-band interference signal and the out-of-band interference signal into the third multi-frequency effect model to obtain a suppression coefficient;
judging whether the pressing coefficient is larger than a preset threshold value or not to obtain a first judgment result;
if the first judgment result shows that the satellite in the navigation terminal is in the lost state, determining that the satellite in the navigation terminal is in the lost state; if the first judgment result shows that the satellite in the navigation terminal continues to stably track, determining that the satellite in the navigation terminal continues to stably track; the third multi-frequency effect model is as follows:
wherein S isioTo suppress the coefficient, PignIs an in-band interference signal, n is the number of in-band multi-frequency electromagnetic interference signals, PogmFor out-of-band interference signals, m is the number of out-of-band multi-frequency electromagnetic interference signals, PinIs an in-band threshold, PomOut-of-band threshold.
2. A system for predicting electromagnetic interference effects of a navigation terminal, comprising:
the navigation terminal comprises a first acquisition module, a second acquisition module and a control module, wherein the first acquisition module is used for acquiring an in-band interference signal and an antenna receiving signal when the interference signal received by the navigation terminal is in-band interference;
the first multi-frequency effect model determining module is used for determining a first multi-frequency effect model according to an antenna receiving signal and the in-band interference signal; the first multi-frequency effect model is:
wherein S isiIs a first multi-frequency effect model, alphainEffect weight coefficients for different in-band electromagnetic interference signals;
the second acquisition module is used for acquiring an out-of-band interference signal and an antenna receiving signal when the interference signal received by the navigation terminal is out-of-band interference;
a second multi-frequency effect model determining module, configured to determine a second multi-frequency effect model according to an antenna receiving signal and the out-of-band interference signal; the second multi-frequency effect model is:
wherein S isoIs a second multi-frequency effect model, alphaomEffect weight coefficients for different in-band electromagnetic interference signals;
a third multi-frequency effect model determining module, configured to determine a third multi-frequency effect model according to the first multi-frequency effect model and the second multi-frequency effect model when an interference signal received by the navigation terminal is in-band interference and out-of-band interference;
the prediction module is used for predicting according to the third multi-frequency effect model and determining the tracking state of a satellite in the navigation terminal under the electromagnetic interference; the tracking states include stable tracking and lost states; the prediction module specifically includes:
a suppression coefficient determining unit, configured to input the in-band interference signal and the out-of-band interference signal into the third multi-frequency effect model to obtain a suppression coefficient;
the judging unit is used for judging whether the pressing coefficient is larger than a preset threshold value or not to obtain a first judging result;
a lost state determination unit, configured to determine that a satellite in the navigation terminal enters a lost state when the first determination result indicates yes;
the stable tracking determining unit is used for determining that the satellite in the navigation terminal continues stable tracking when the first judgment result shows that the satellite continues stable tracking;
the third multi-frequency effect model is as follows:
wherein S isioTo suppress the coefficient, PignIs an in-band interference signal, n is the number of in-band multi-frequency electromagnetic interference signals, PogmFor out-of-band interference signals, m is the number of out-of-band multi-frequency electromagnetic interference signals, PinIs an in-band threshold, PomOut-of-band threshold.
3. An apparatus for predicting electromagnetic interference effect of a navigation terminal, comprising: a first signal source, a second signal source, a navigation signal simulator, a directional coupler, a power divider, a radio frequency front-end module, a navigation terminal, an injection power monitoring spectrometer, a radio frequency monitoring spectrometer and a monitoring computer applying the method for predicting the electromagnetic interference effect of the navigation terminal according to claim 1;
the first signal source, the second signal source and the navigation signal simulator are all connected with one end of the directional coupler, the first signal source is used for generating in-band interference, and the second signal source is used for generating out-of-band interference; the other end of the directional coupler is connected with one end of the power divider, the other end of the power divider is respectively connected with the injection power monitoring frequency spectrograph and the radio frequency front end module, and the injection power monitoring frequency spectrograph is used for observing the power of an interference signal injected into the radio frequency front end module; the radio frequency front end module is used for simulating an antenna of an active antenna to receive signals, the radio frequency front end module is also connected with a navigation terminal, the navigation terminal is also respectively connected with the monitoring computer and the radio frequency monitoring frequency spectrograph, and the monitoring computer is used for monitoring various states of the navigation terminal in real time; the monitoring computer is also connected with the navigation signal simulator.
4. The apparatus for predicting the effect of electromagnetic interference of a navigation terminal as set forth in claim 3, wherein said first signal source is provided with one or more than one, and said second signal source is provided with one or more than one.
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