CN103178914B - Method for accurately analyzing fading characteristics of satellite communication channels of high-frequency helicopters - Google Patents
Method for accurately analyzing fading characteristics of satellite communication channels of high-frequency helicopters Download PDFInfo
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- CN103178914B CN103178914B CN201310089539.4A CN201310089539A CN103178914B CN 103178914 B CN103178914 B CN 103178914B CN 201310089539 A CN201310089539 A CN 201310089539A CN 103178914 B CN103178914 B CN 103178914B
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Abstract
The invention discloses a method for accurately analyzing the fading characteristics of satellite communication channels of high-frequency helicopters. The method comprises the following steps of: accurately analyzing the influence of rotor wings of helicopters on the fading characteristics of satellite communication by adopting an electromagnetic simulation method, and analyzing the influence of other general environmental factors on the fading of the channels by using a probability distribution module, thus analysis results are more accurate and effective in comparison with the analysis results of a traditional channel fading analysis method. The method has the advantages that the accuracy and reliability of fading characteristic analysis of the satellite communication wireless channels of the high-frequency (above Ku frequency ranges) helicopters are greatly improved by adopting an electromagnetic simulation analysis and probability distribution model combined mixing analysis method, the simulated analysis speed is accelerated, the hardware pay expenses needed for simulation analysis are saved, and the technical problem of lacking of methods for accurately analyzing the transmission characteristic of the satellite wireless communication channels of conventional high-frequency helicopters is solved.
Description
Technical field
The present invention relates to the research method of wireless channel transmission characteristic, be specifically related to a kind of method of accurate analysis high band helicopter satellite communication channel fading characteristic.
Background technology
Fading Characteristics of Outdoor Time-variant Wireless Channel research under particular surroundings is the difficulties in Communication Studies field always.For the helicopter satellite communication of current extensive use, its Fading Characteristics of Outdoor Time-variant Wireless Channel of accurate analysis, to fully excavating capacity of communication system, optimization system performance has important directive significance.But what be subject to rotor wing rotation due to its satellite communication antena blocks impact, and the environmental impact factor of its channel fading characteristic not only with general is relevant, and closely related with the dynamic barriers effect of rotor, analyze quite complexity and difficult.
Present analysis Fading Characteristics of Outdoor Time-variant Wireless Channel generally adopts the method based on probability Distribution Model, these methods are the empirical equations of the statistical law that only considered general environment, more effective to the characteristic of channel analyzing general environment, but it is no longer applicable to particular surroundings, main cause is particular surroundings, and often distance communication antenna is very near, therefore its impact is not allowed to ignore, and sometimes even exceedes the impact of other all external environmental factors.Fading Characteristics of Outdoor Time-variant Wireless Channel belongs to radio wave propagation rule problem in itself, and method of therefore researching and analysing more accurately is the Electromagnetic Simulation analytical technology adopting or develop based on strict maxwell equation group.Although had some to study for the electromagnetic simulation technique of lifting airscrew occlusion issue specially both at home and abroad at present, but they generally only considered lifting airscrew and block impact on communication performance when analyzing, and lack system complete analysis to all environmental factors of periphery, such as do not consider multipath effect that mountain area physical features, the woods etc. residing for helicopter bring, occlusion effect impact; And, analysis frequency range mainly very high frequency(VHF) (the Very High Frequency) VHF(30 ~ 300MHz of current helicopter rotor wing electromagnetic emulation) or superfrequency (Ultra High Frequency) UHF(300 ~ 3000MHz) relatively low frequency range, and for the high band moving towards gradually at present to apply, especially there is not been reported for Ku and Ka frequency range (more than 12.5GHz).But to high band carry out Electromagnetic Simulation accurate analysis can face simulation calculation amount excessive, a series of practical difficulty such as to be difficult to carry out, need to further investigate solution further.
From analyzing above, owing to also lacking Electromagnetic Simulation analysis means accurately and effectively to high band (more than Ku frequency range) lifting airscrew occlusion issue, and helicopter satellite communication channel fading characteristic is also lacked to the comprehensive analytical method of system considering all such environmental effects.
Summary of the invention
For above problems of the prior art, in order to Fading Characteristics of Outdoor Time-variant Wireless Channel and the rule of the satellite communication of high band helicopter accurately can be obtained, the present invention proposes a kind of hybrid analysis not only having comprised high-frequency electromagnetic emulation mode but also comprised probability Distribution Model.
The object of the present invention is to provide the method for a kind of accurate analysis high band (more than Ku frequency range) helicopter satellite communication channel fading characteristic, lacking the problem of accurate analysis means for solving existing high band helicopter satellite communication wireless channel transmission characteristic.
The analytical method of high band helicopter satellite communication channel fading characteristic of the present invention comprises the following steps:
1) Electromagnetic Simulation method is utilized, accurate analysis high band lifting airscrew rotates the impact on onboard satellite communication antenna performance, wherein first the dynamic property of the antenna under rotor wing rotation state is equivalent to the antenna performance in series of discrete sampling instant under rotor inactive state by employing quasi-static method, recycling Electromagnetic Simulation algorithm, analyze and obtain helicopter under the attitude corresponding to each discrete sampling instant and rotor wing rotation angle, static rotor is on the impact of antenna performance;
2) utilize probability Distribution Model, analysis other general environment influencing factors except lifting airscrew impact are on the impact of helicopter satellite communication channel fading characteristic;
3) analysis result of the analysis result of Electromagnetic Simulation method and probability Distribution Model is carried out hybrid analysis, thus obtain the accurate analysis result of high band helicopter satellite communication channel fading characteristic.
Wherein, in step 1), quasi-static method refers to, adopts the impact of static rotor on radiation field of aerial in the sampling instant of series of discrete to simulate the dynamic electric magnetic characteristic of this antenna under rotor wing rotation state.
Helicopter, under the attitude corresponding to each sampling instant and rotor wing rotation angle, obtains the impact of static rotor on antenna performance by Geometric Modeling and Accurate Analysis.Conventional method accurate analysis high band lifting airscrew occlusion issue is adopted to face two large main bugbears: one is that this analytic target belongs to complicated electrically large sizes problem, if adopt the algorithm of accurate simulation completely, as moment method, then by facing, unknown quantity to be asked is too much, simulation calculation amount is excessive and be difficult to the actual difficult problem solved, if all adopt high-frequency approximation method, then can bring the problem of computational accuracy deficiency; Two is analyze this problem to need to carry out simulation analysis calculating one by one for different helicopter attitudes and rotor wing rotation angle, and this just needs a large amount of approximate calculating repeated, if adopt traditional analysis will expend time in long.
In order to solve the unknown quantity to be asked that runs into when analysis of high frequency section (more than Ku frequency range) rotor occlusion issue too much and simulation calculation amount problems of too, the present invention adopts the radiation field of moment method Accurate Analysis independent onboard satellite communication antenna part, adopts high-frequency approximation methods analyst other all rotors except onboard satellite communication antenna and the electromagnetic field of fuselage sections.The hybrid electromagnetic emulation mode that moment method combines with high-frequency approximation method, significantly reduces computation complexity while guarantee analysis precision.High-frequency approximation method comprises geometrical optics approach GO, physical optical method PO, Method of Equivalent Currents MEC, geometric theory of diffraction GTD, consistency diffraction theory UTD, the progressive diffraction theory UAT of consistency and physics diffraction theory PTD.
In addition, for the feature all needing a large amount of double counting antenna pattern under different rotor wing rotation angle or different helicopter flight attitude, the present invention adopts equivalent face method to accelerate simulation calculation process further.Equivalent face method is based on Huygen's principle, the magnetic distribution of radiation field near antenna in an imaginary plane of the independent onboard satellite communication antenna first utilizing moment method Accurate Analysis to obtain, then utilize its equivalent substitute actual antennas, carry out the performance evaluation that the antenna under other flight attitudes and rotor wing rotation angle blocks by rotor.Equivalent face method improves computational speed and the efficiency of Electromagnetic Simulation.
Electromagnetic Simulation algorithm of the present invention is the fast mixing process having gathered moment method, high-frequency electromagnetic computational methods and equivalent face method, wherein, Method for Accurate Calculation based on moment method is adopted to onboard satellite communication antenna, and high-frequency approximation method is adopted to rotor except the antenna and other fuselage sections, adopt equivalent face method to replace actual antennas to accelerate the computational process of different helicopter attitude and rotor wing rotation angle simultaneously.Therefore the Electromagnetic Simulation method comprising quasi-static method and Electromagnetic Simulation algorithm that the present invention proposes can take into account the requirement of simulation accuracy and speed simultaneously, greatly improves efficiency of algorithm and validity.
In step 2) in, probability Distribution Model adopts Corazza channel simulation model to calculate the multipath effect of general environment and shadow effect to the impact of channel fading characteristic, wherein multipath effect obeys Rayleigh Rayleigh distribution, and shadow effect obeys logarithm normal Lognormal distributes.And adopt three condition Markov Chain to the change between the three kinds of typical environment states describing Corazza channel simulation model, and when to be described in helicopter and satellite fast moving, the change at random of environment residing for onboard satellite communication antenna.Three kinds of typical environment states of Corazza channel simulation model are the shadow-free state of corresponding open ground, the slight shade shape in corresponding suburb and the severe shadow state in corresponding complicated city respectively.
In step 3), hybrid analysis refers to, the gain of onboard satellite communication antenna Electromagnetic Simulation method obtained in time result of variations replaces the antenna fixed gain that supposes in probability Distribution Model, then utilizes probability Distribution Model to carry out last Macro or mass analysis to Fading Characteristics of Outdoor Time-variant Wireless Channel.
The present invention proposes the hybrid analysis of associating Electromagnetic Simulation method and probability Distribution Model first, adopt the impact of Electromagnetic Simulation method Accurate Analysis lifting airscrew rotation on satellite communication fading characteristic, and utilize the impact that probability Distribution Model analysis other general environment factors in addition cause channel fading, thus make analysis result more more accurate and effective than conventional channel decline analytical method.
Beneficial effect of the present invention:
The present invention is by adopting the hybrid analysis of associating Electromagnetic Simulation method and probability Distribution Model, greatly improve accuracy and the confidence level of the analysis of high band (more than Ku frequency range) helicopter satellite communication Fading Characteristics of Outdoor Time-variant Wireless Channel, accelerate simulation analysis speed, save the hardware spending needed for simulation analysis, efficiently solve the technical barrier that existing high band helicopter satellite communication wireless channel transmission characteristic lacks accurate analysis means.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of the complete Corazza channel simulation model of the present invention after the impact considering multipath effect and shadow effect;
Fig. 2 is the helicopter satellite communication antena gain that utilizes Electromagnetic Simulation methods analyst to obtain in the f=12.5GHz situation curve chart with the time variations of rotor wing rotation;
The helicopter Satellite Communication Receive signal time history plot that Fig. 3 (a) obtains for utilizing the analysis of Corazza channel simulation model in f=12.5GHz situation, (b) is the partial enlarged drawing in (a) in rectangle frame;
Fig. 4 is in conjunction with the helicopter satellite communication antena Received signal strength time history plot that Electromagnetic Simulation method and the analysis of Corazza channel simulation model obtain in f=12.5GHz situation;
Fig. 5 is the flow chart of the analytical method of high band helicopter satellite communication channel fading characteristic of the present invention.
Embodiment
Below in conjunction with accompanying drawing, describe the present invention in detail by embodiment.
In the present embodiment, the operating frequency of helicopter satellite communication channel is f=12.5GHz.Major parameter and the operational environment of helicopter are as follows: 1) lifting airscrew comprises 5 blades, and rotor wing rotation speed 400 encloses/minute, the long 10.65m of each blade, wide 52cm; 2) onboard satellite communication antenna is parabolic antenna, actinal surface diameter 35cm, burnt footpath than 0.6, maximum directive gain 29.1dB; 3) onboard satellite communication antenna is positioned at the below of lifting airscrew and the right back of fuselage upper surface, departs from helicopter fuselage center line 0.3m in the horizontal direction and the rotating shaft center 1.5m of distance rotor, in vertical direction distance rotor blade 0.8m; 4) helicopter job site is positioned at somewhere, Beijing (north latitude 39.42 °, east longitude 116.46 °), and the satellite that helicopter satellite communication antena is aimed at is ChinaStar-1 geosynchronous satellite (east longitude 87.5 °); 5) helicopter operational environment is assumed to the shadow-free state of open ground.
As shown in Figure 5, the operating frequency of the present embodiment is that the analytical method of the helicopter satellite communication channel fading characteristic of f=12.5GHz comprises the following steps:
1) utilize Electromagnetic Simulation method, accurate analysis high band lifting airscrew rotates the impact on onboard satellite communication antenna performance:
First, quasi-static method is adopted to study the antenna dynamic electric magnetic characteristic under rotor wing rotation state, when rotor wing rotation angular speed is much smaller than Electromagnetic Wave Propagation angular speed, can go up at any one time and revolving vane be regarded as " freezing " on rotational trajectory, thus namely adopt static rotor in a series of sampling instant to the gain effects of antenna performance to simulate the dynamic electric magnetic characteristic of this antenna under rotor wing rotation state;
Then, helicopter is under the attitude corresponding to each sampling instant and rotor wing rotation angle, the radiation field of moment method Accurate Analysis independent onboard satellite communication antenna part is adopted when applying FEKO software, adopt high-frequency approximation methods analyst other all rotors except onboard satellite communication antenna and the electromagnetic field of fuselage sections, obtain the impact of static rotor on antenna performance by Geometric Modeling and Accurate Analysis;
Further, equivalent face method is have employed during application FEKO software, based on Huygen's principle, first moment method Accurate Analysis is utilized to obtain the magnetic distribution of satellite communication antena near antenna in certain imaginary plane, then utilize its equivalent substitute actual antennas, carry out the performance evaluation that the antenna under other flight attitudes and rotor wing rotation angle blocks by rotor.
2) utilize probability Distribution Model, analysis other general environment influencing factors except lifting airscrew impact are on the impact of helicopter satellite communication channel fading characteristic.
Fig. 1 gives the complete Corazza channel simulation model after the impact considering multipath effect and shadow effect of the present embodiment.
Two summation symbol Σ above in Fig. 1
cand Σ
srepresent respectively and sue for peace to the real part part of the multipath signal in multipath effect and imaginary part part, M represents multipath number, and all multipath signals synthesize later signal strength signal intensity probability density distribution and obey Rayleigh distribution.Multipath signal and direct signal 1 are synthesized, the intensity of the resultant signal obtained || probability density function obey Rice distribution; Rice distribution is determined by Rice factor K, and K represents the ratio of direct signal and the power of multipath signal; By direct signal 1 normalization in Fig. 1, be expressed as real number 1.X
ct () representative considers that Rice factor K affects the real part part of later composite signal, jX
st () representative considers that Rice factor K affects the imaginary part part of later composite signal.
Following summation symbol Σ in Fig. 1
ithe content of front and back and the right exponent arithmetic e
(.
)represent the modeling process of shadow effect, shadow effect generally meets Lognormal distribution.Shadow effect determines primarily of two parameters: shade average μ and shade standard deviation sigma; These two parameters determine the average dafing depth of shadow effect respectively, and the severe degree of shade change.After considering all factors (comprising direct signal, multipath effect and shadow effect), obtain the total signal strength R (t) on the right in Fig. 1.
Corazza channel simulation model determines primarily of three parameters: Rice factor K, shade average μ, shade standard deviation sigma.Block environment for different ground and to satellite elevation angle, three parameter K in Corazza channel simulation model, μ, σ are all not identical.The complexity of the present invention's ground environment residing for helicopter is different with coverage extent, ground environment is divided into three kinds of typicalnesses: the slight shade shape in the shadow-free state of corresponding open ground, corresponding suburb and the severe shadow state in corresponding complicated city, in the present embodiment, helicopter operational environment is assumed to the shadow-free state of open ground.
When in order to be described in helicopter and satellite fast moving, the change of environment residing for onboard satellite communication antenna, the present invention adopts three condition Markov Chain to the change between the three kinds of typical environment states describing Corazza channel simulation model, wherein, the state transition probability matrix as key parameter obtains according to the statistical law of actual conditions.
Three important parameters in Corazza channel simulation model and the relation between the α of satellite elevation angle, the available following expression formula approximate representation based on a large amount of statistics:
K=K
0+K
1α+K
2α
2+K
3α
3
μ=μ
0+μ
1α+μ
2α
2+μ
3α
3
σ=σ
0+σ
1α+σ
2α
2+σ
3α
3
In above formula, each coefficient represents fitting coefficient, chooses following representative value respectively in this example: K=[26.43 ,-2.644,0.08377 ,-4.111 × 10
-4], μ=[3.978 ,-0.1742,0.002647 ,-1.367 × 10
-5], σ=[0,0,0,0].
3) analysis result in conjunction with Electromagnetic Simulation method and probability Distribution Model carries out hybrid analysis, the final accurate analysis result obtaining the high band helicopter satellite communication channel fading characteristic considering all environmental impact factors.
The gain of the onboard satellite communication antenna that Electromagnetic Simulation method mainly obtains by hybrid analysis in time result of variations replaces the antenna fixed gain that supposes in probability Distribution Model, then utilizes probability Distribution Model to carry out last Macro or mass analysis to Fading Characteristics of Outdoor Time-variant Wireless Channel.In this way, the impact that Electromagnetic Simulation method can be utilized accurately to calculate the particular surroundings near antenna cause antenna performance, and utilize the impact that probability Distribution Model analysis other general environment factors in addition cause channel fading, thus make analysis result than traditional helicopter satellite communication channel fading characteristic analytical method accurate and effective more.
Fig. 2, Fig. 3 and Fig. 4 sets forth the present embodiment under the helicopter environment of f=12.5GHz, the helicopter satellite communication antena gain utilizing Electromagnetic Simulation methods analyst to obtain in step 1) is with the time changing curve of rotor wing rotation, in step 2) in utilize the Corazza channel simulation model analysis of Corpus--based Method rule to obtain helicopter Satellite Communication Receive signal curve over time, and in conjunction with the helicopter satellite communication antena Received signal strength curve over time that Electromagnetic Simulation method and the analysis of Corazza channel simulation model obtain in step 3).As shown in Figure 2, Ku frequency range lifting airscrew rotates and blocks the impact caused the gain of onboard satellite communication antenna and present regular and compared with the change of macrorelief; And the helicopter surrounding environment being operated in open ground presents change unordered and more by a small margin to the impact that onboard satellite communication receive signals level causes, as shown in Figure 3; Gather the impact of all environmental factors, helicopter satellite communication channel fading characteristic determines primarily of rotor wing rotation factor of blocking, but detail section reflects the impact of multipath effect and the shadow effect caused by helicopter ambient environmental factors, as shown in Figure 4.In a word, by the mixed method adopting the present invention to propose, high band (more than Ku frequency range) helicopter satellite communication channel fading characteristic is analyzed, not only can obtain the accurate rule of high band (more than Ku frequency range) lifting airscrew rotation to onboard satellite communication fade characteristic, and can obtain adopting separately Electromagnetic Simulation method than ever, or the analysis result adopting separately the method for the probability Distribution Model of Corpus--based Method rule more comprehensive and accurate.
It is finally noted that the object publicizing and implementing example is to help to understand the present invention further, but it will be appreciated by those skilled in the art that: without departing from the spirit and scope of the invention and the appended claims, various substitutions and modifications are all possible.Therefore, the present invention should not be limited to the content disclosed in embodiment, and the scope that the scope of protection of present invention defines with claims is as the criterion.
Claims (6)
1. an analytical method for high band helicopter satellite communication channel fading characteristic, is characterized in that, described analytical method comprises the following steps:
1) Electromagnetic Simulation method is utilized, accurate analysis high band lifting airscrew rotates the impact on onboard satellite communication antenna performance, wherein first the dynamic property of the antenna under rotor wing rotation state is equivalent to the antenna performance in series of discrete sampling instant under rotor inactive state by employing quasi-static method, recycling Electromagnetic Simulation algorithm, analyze and obtain helicopter under the attitude corresponding to each discrete sampling instant and rotor wing rotation angle, static rotor is on the impact of antenna performance;
2) utilize probability Distribution Model, analysis other general environment influencing factors except lifting airscrew impact are on the impact of helicopter satellite communication channel fading characteristic;
3) analysis result of the analysis result of Electromagnetic Simulation method and probability Distribution Model is carried out hybrid analysis, thus obtain the accurate analysis result of high band helicopter satellite communication channel fading characteristic;
Comprise equivalent face method further, described equivalent face method is based on Huygen's principle, the magnetic distribution of radiation field near antenna in an imaginary plane of the independent onboard satellite communication antenna first utilizing moment method Accurate Analysis to obtain, then utilize its equivalent substitute actual antennas, carry out the performance evaluation that the antenna under other flight attitudes and rotor wing rotation angle blocks by rotor.
2. analytical method as claimed in claim 1, it is characterized in that, in step 1) in, described quasi-static method refers to, adopts the impact of static rotor on radiation field of aerial in the sampling instant of series of discrete to simulate the dynamic electric magnetic characteristic of this antenna under rotor wing rotation state.
3. analytical method as claimed in claim 2, it is characterized in that, in step 1) in, adopt the radiation field of moment method Accurate Analysis independent onboard satellite communication antenna part, adopt high-frequency approximation methods analyst other all rotors except onboard satellite communication antenna and the electromagnetic field of fuselage sections.
4. analytical method as claimed in claim 1, it is characterized in that, in step 2) in, described probability Distribution Model adopts Corazza channel simulation model to calculate the multipath effect of general environment and shadow effect to the impact of channel fading characteristic, wherein said multipath effect obeys Rayleigh Rayleigh distribution, and described shadow effect obeys logarithm normal Lognormal distributes.
5. analytical method as claimed in claim 4, it is characterized in that, employing three condition Markov Chain describes the change between three kinds of typical environment states of Corazza channel simulation model, when to be described in helicopter and satellite fast moving, the change at random of environment residing for onboard satellite communication antenna.
6. analytical method as claimed in claim 1, it is characterized in that, in step 3) in, described hybrid analysis refers to, the gain of onboard satellite communication antenna Electromagnetic Simulation method obtained in time result of variations replaces the antenna fixed gain that supposes in probability Distribution Model, then utilizes probability Distribution Model to carry out last Macro or mass analysis to Fading Characteristics of Outdoor Time-variant Wireless Channel.
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| 《用矩量法研究直升机高频天线辐射性能的旋翼调制效应》;牛臻弋等;《航空学报》;20040725(第4期);第701页第24行-第704页第8行 * |
| 陈江等.《多径衰落的空间相关性及其对空间分集接收机的影响》.《北京大学学报(自然科学版)》.2003,第39卷(第3期), * |
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