CN101719802A - Device and calculation method for predicting maximum usable frequency (MUF) of short-wave communication - Google Patents

Abstract

The invention relates to a device for predicting the maximum usable frequency (MUF) of a short-wave communication, comprising a user input module, an environmental model module, a space distribution module for establishing a refractive index according to a magnetoionic theory, a ray tracking characteristic calculation module and a predicated maximum usable frequency expansion module; the calculation method for predicting the maximum usable frequency of the short-wave communication comprises the seven steps of: 1. confirming an initial value of a ray equation; 2. establishing electronic concentration distribution by utilizing international feference ionosphere (IRI); 3. introducing a geomagnetic field model of International geomagnetic reference field (IGRF) and establishing a function relation; 4. solving a differential equation; 5. extracting ray parameters that reach the ground; 6. screening ray tracking results; and 7. selecting 85 percent of MUF as the frequency used by the short-wave communication. The invention solves the method for acquiring form parameters of the ionized layer model and establishes the electronic concentration distribution over the position according to longitudes and latitudes at any time and place. The invention has wide practical value and application prospects in the technical field of short-wave communications.

Description

A kind of device and computational methods of predicting maximum usable frequency (MUF) of short-wave communication

(1) technical field

The present invention relates to a kind of device and computational methods, belong to the short wave communication technical field based on ray tracing technique prediction maximum usable frequency (MUF) of short-wave communication.

(2) background technology

In the application of short wave communication, for the ionosphere of certain electron density distribution and certain sending and receiving distance, the electric wave that can reflect the ground of turning back has a frequency maximum, is called maximum usable frequency (MUF), it with the transmitting-receiving between distance reduce and step-down.If distance is certain between sending and receiving, tranmitting frequency is lower, and acceptance point can be received the high and low angle ripple of certain delay inequality; Along with frequency gets higher, angle of site ripple delay inequality is dwindled so that gradual change is extremely zero, and angle of site ripple overlaps; If frequency raises again, then acceptance point falls into and jumps in the distance, can not receive fully to transmit.Therefore, the frequency that the circuit of certain distance can be propagated must have a upper limit, and this upper limiting frequency is called the maximum usable frequency of this circuit.

Ray tracing technique is under the situation of high frequency, and electromagnetic wave is approximately ray.According to the environmental condition at ray propagates place, the electromagnetic wave track is calculated, therefore utilize this technology just can calculate launch point all rays to acceptance point.And, according to calculating all fundamental characteristics (as parameters such as acceptance point field intensity, time delay, the angles of arrival) that can obtain ray.

Utilizing ionosphere to carry out as channel in the process of short wave communication, the variation of short wave communication channel often causes communicating pair to receive and uncertainty occurs.Secondly, the influence in earth magnetic field also becomes a very important factor.In short wave communication, use ray tracing technique and just must consider the environment of ray propagates, so must come environmental modeling according to ionospheric model and earth magnetic field model.In addition, because actual condition restriction, can not accomplish short wave communication is each time all surveyed.Therefore, utilization can predict accurately that the Mathematical Modeling of ionosphere environment and earth magnetic field environment predicts, whether maximum closing to reality situation instructs the setting of the practical operation of short wave communication such as frequency-selecting and antenna direction reasonable, should do and how to handle.

The empirical equation current, that P.1240-1 the prediction of the maximum usable frequency in the general short wave communication (MUF) mainly provides by ITU-R according to different transmitter configuration and current environment, is simply predicted.

Its empirical equation is as follows:

The calculating of F2 layer basic MUF is estimated

$F2\left(D\right)\mathrm{MUF}=[1+\left(\frac{C_D}{C_{3000}}\right)(B-1)]\·\mathrm{fo}{F}_2+\frac{f_H}{2}(1-\frac{D}{d_{\max }})$

f _HIt is the magnetic rotation frequency;

C _D＝0.74-0.591Z-0.424Z ²-0.090Z ³+0.088Z ⁴+0.181Z ⁵+0.096Z ⁶

Z＝1-2D/dmax

C ₃₀₀₀C when being exactly D=3000km _DValue, D is a great-circle distance.

The single-hop maximum outreach d of this back warp F2 layer reflection _Max(km) provide by following formula:

d _max＝4780+(12610+2140/x ²-49720/x ⁴-688900/x ⁶)(1/B-0.303)

Here B is provided by following formula:

$B=M\left(3000\right)F2-0.124+[{\left[M\left(3000\right)F2\right]}^2-4]\·[0.0215+0.005\sin (\frac{7.854}{x}-1.9635)]$

X=foF2/foE, if the x that is asked is littler than 2, then x gets 2.

The calculating of F1 layer basic MUF is estimated

M _F1＝J ₀-0.01(J ₀-J ₁₀₀)R ₁₂

Here:

J ₀＝0.16+2.64×10 ^-3D-0.40×10 ^-6D ²

J ₁₀₀＝-0.52+2.69×10 ^-3D-0.39×10 ^-6D ²

The great-circle distance of D representative in 2000km～3400km scope.

The calculating of E layer basic MUF is estimated

M _E＝3.94+2.80x-1.70x ²-0.60x ³+0.96x ⁴

Here:

$x=\frac{D-1150}{1150}$

D is a great-circle distance.

Concrete parameter wherein also needs to obtain according to different ionospheric models, P.1240-1 the accuracy of the MUF that predicts of standard is not high according to ITU-R, also inapplicable for some application scenario, the prediction for MUF just occurs and the actual bigger problem of situation gap like this.And complexity in actual applications is higher, as wants the situation of interpretation ionospheric layer, and this uses difficulty to increase for the user, and the possibility of introducing error improves greatly.

Utilize ray tracing technique to predict short wave communication some characterisitic parameters in using, as long as the model that utilizes is closing to reality farthest, just can coincide to a more accurate degree with actual conditions, what adopt in the application of ray tracing usually mainly is accurate parabolic model, and this model is described below:

The general simple parabolic curve of employing form comes the interior electron concentration of STATIC CORRECTION USING APPROXIMATE LAYER to be called parabolic layer with the layer of the variation of height, and its expression formula is:

$N_e=\left\{\begin{array}{cc}{N}_{\mathrm{em}}[1-{\left(\frac{h-h_m}{Y_n}\right)}^2]& \left(\right|h-h_m|\≤Y_m)\\ 0& \left(\right|h-h_m|\≥Y_m)\end{array}\right.$

N in the formula _EmBe electron concentration maximum, h _mBe the height at electron concentration maximum place, Y _mHalf thickness for parabolic layer.Because mathematic(al) representation is fairly simple, so often be used.

In addition, for ray tracing technique, the general form of calculation that all adopts two dimension, situation about showing generally has only the great-circle distance of communication two places, therefore, be simple approximate model in the introducing of ionospheric model and the introducing great majority in earth magnetic field, can only be to adopt average form in addition in the use of model, can not adopt reconstruct environmental model step by step, the error that exists on the precision of using is bigger like this.The model in earth magnetic field generally can not introduced.But the earth magnetic field is bigger to the influence of ray under the actual conditions.The basis of adopting accurate parabolic ionospheric model to be used as ray tracing technique is not extensively approved, in addition, in the model use, the formal parameter of model obtains existing problems, and ionosphere constantly changes according to the time place, and the situation that can occur layering in the local time of according to the locality, this situation are difficult to embody when utilizing accurate parabolic model, and the situation credible and that gear to actual circumstances of model reduces greatly.In general application, seldom introduce the earth magnetic field model, and the introducing of magnetic field model is explained seldom over the ground.In addition, adopt the demonstration and the account form of two dimension, to the utilizability of the parameter that calculates not high (as the angle of arrival of ray etc.).So existing technology is not in that to calculate accuracy and realistic situation high, further application also is difficult to accomplish to parameters calculated.

(3) summary of the invention

(1) goal of the invention: in short wave communication is used, in order to make the communication normal use, and guarantee a reliable communication channel, just must carry out analyses and prediction to the channel of short wave communication, according to prediction, select suitable frequency and suitable antenna to place, finally realize the efficient communication needs of communicating pair.The purpose of this invention is to provide a kind of device and computational methods of predicting maximum usable frequency (MUF) of short-wave communication, this device and method has overcome the deficiencies in the prior art, it adopts the basis of international reference ionosphere IRI as ray tracing, solved ionospheric model formal parameter acquisition methods, and ionosphere electron concentration distributed in three dimensions prediction, will be according to any time, the longitude and latitude of anywhere, the electron concentration of setting up this sky, position distributes.Introduce international earth magnetic field model IGRF, this model can predict that the earth magnetic field in the anywhere height above sea level sky of any time distributes, and obtains field intensity size and geomagnetic inclination and geomagnetic declination.The influence in the earth magnetic field of can not ignore is joined in the ray tracing technique, thereby further revise the environment of ray propagates, the calculating parameter that is geared to actual circumstances more.According to two master patterns, realize the ray tracing under the three-dimensional environment, under the environment of three-dimensional, calculate, carry out according to the actual size ratio fully, thereby the data that calculate more can embody actual at that time situation, better the direct communications both sides.Therefore, predict maximum usable frequency MUF in the short wave communication, realize application directs short wave communication based on this ray tracing technique.

(2) technical scheme:

1, as shown in Figure 1, a kind of device of the present invention based on the prediction maximum usable frequency (MUF) of short-wave communication, this device is made up of 5 modules: they are user's input module, environmental model module, make up spatial distribution module, the ray tracing property calculation module of refractive index and predict the maximum usable frequency expansion module according to magneto-ionic theory, position between these five modules, annexation and signal trend are: initial by user's input module, condition when determining to use, according to user's input, the environmental model module is carried out modeling and is handled; According to the model of being set up, the spatial distribution module that makes up refractive index according to magneto-ionic theory makes up the refractive index spatial distribution, according to the refractive index spatial distribution, the ray tracing computing module carries out ray tracing and calculates, and predicts the data estimation maximum usable frequency MUF that the utilization of maximum usable frequency expansion module is calculated at last.

Described user's input module, be needs according to the user, the condition of using is set, and the main users interface has the emission mode, elevation coverage of tranmitting frequency, the ray of geographical latitude and longitude coordinates, the ray of current time set, launch point and acceptance point etc.Wherein input further is applied as and calculates great-circle distance and launch point direction deflection angle to acceptance point.

The computing formula of great-circle distance D is as follows:

D＝R×φ

The computing formula of direction deflection angle α of being pointed to place B by place A is as follows:

$\cos \mathrm{\α}=\frac{\sin \mathrm{latB}-\sin \mathrm{LatA}\·\cos \mathrm{\φ}}{\cos \mathrm{latA}}$

Wherein φ is drawn by following formula

cosφ＝sinlatA·sinlatB+coslatA·coslatB·cos(longA-longB)

This module is according to different application needs, ionosphere, earth magnetic field basic parameter under the different conditions of demand are set, with these basic parameters, make up the communication environments of ray, it is mainly imported the geographical longitude and latitude and the height above sea level in universal time, this zone by the user.

Described environmental model module is that international ionosphere is described with reference to the Mathematical Modeling of IRI and international earth magnetic field reference model IGRF, adopts the software encapsulation form to realize, is embedded in the computational methods.This module mainly needs according to the user, sets up the spatial distribution of electron concentration according to international ionosphere with reference to IRI, sets up the spatial distribution in earth magnetic field with reference to IGRF according to international earth magnetic field.Ionospheric fundamental forecasting data are set up according to ITU standard CC IR coefficient, have international universal applicability.The generally approval that the accuracy of earth magnetic field model also obtains estimating.The foundation of IRI model mainly is according to IRI model data, go out the distribution situation of foF2 and M (3000) F2 based on the CCIR coefficient calculations, according to these two ionosphere resemblance parameters, shift out other characteristic parameter one by one onto, main characteristic parameter has foF1, foE, hmF1, hmE, and the distribution situation of E range upon range of mountains paddy, wherein need parameter such as the sunspot number month known, solar zenith angle, sunrise sunset constantly, geomagnetic declinations etc. also are specifically to calculate according to input, at last these formal parameters are integrated, and construct the needed electron concentration distribution situation of user.The IGRF model mainly is according to the Gaussian sphere hamonic function, and its spherical harmonic coefficient adopts the basic world with reference to the IGRF coefficient table.According to these data computation spatial distribution situation in magnetic field predictably, the main parameter that calculates has magnetic field intensity, geomagnetic declination, geomagnetic inclination etc.Provide the parameter that to use according to magneto-ionic theory.

Described spatial distribution module according to magneto-ionic theory structure refractive index is to utilize magneto-ionic theory to make up the functional module of refractive index, and this module is utilized the environmental model of setting up previously, provides the spatial distribution of refractive index.The key foundation of ray-tracing algorithm foundation is a magneto-ionic theory in the patent, principal mode is the Appleton-Hartree formula, this formula has been set up the relation of refractive index with electron concentration and earth magnetic field spatial distribution ignoring under the condition of particle encounter, this formula is as follows:

$n^2=1-\frac{X(1-X)}{1-X-\frac{1}{2}{Y}_T^2\±\sqrt{\frac{1}{4}{Y}_T^4+Y_L^2{(1-X)}^2}}$

$\left.\begin{array}{c}{Y}_L^2=Y^2{\cos }^2\mathrm{\θ}\\ Y_T^2=Y^2{\sin }^2\mathrm{\θ}\end{array}\right\}$ $\left.\begin{array}{c}X=\frac{N_e{e}^2}{m{\mathrm{\ϵ}}_0{\mathrm{\ω}}^2}\\ Y=\frac{{\mathrm{\ω}}_H}{\mathrm{\ω}}\end{array}\right\}$ ${\mathrm{\ω}}_H=\frac{e{B}_0}{m}$

By formula as can be seen, wherein: it is the basic data of setting up refractive index that electron concentration and earth magnetic field distribute, and makes up three-dimensional refractive index according to these two data and distributes, and just framework has played whole ray propagates environment.N wherein _eNeed set up according to the IRI in the environmental model, and Y _LY _TTo set up according to earth magnetic field reference model IGRF.

Described ray tracing property calculation module is based on the functional module that ray tracing technique calculates ray tracing and ray arrival characteristic.This module is utilized ray equation under the spherical coordinates:

Wherein:

P is a group path.

Utilize the numerical differentiation equations system method to find the solution this equation on this basis, according to different frequencies and emission angle, different ray propagates environment, each track of ray calculates the most at last, the fundamental characteristics when obtaining ray arrival ground simultaneously.Each bar ray all has its corresponding character, the group path of the characteristic on the frequency in the situation of penetrating that starts as before, launching elevation, emission drift angle and arrival ground such as the great-circle distance between arrival point and the launch point, ray operation, the arrival incident angle of ray, the signal strength signal intensity when ray arrives, time delay, multipath etc.These parameters offer the application extension module and further handle, the needs that finally are applied as the output of this module.

Described prediction maximum usable frequency expansion module is based on an expanded application of ray tracing module result of calculation, and the condition of its control ray emission calculates corresponding ray characteristics, according to these prediction of result maximum usable frequency MUF.According to maximum usable frequency is the definition of MUF, and ray is set the maximal rays elevation angle through the characteristic of ionospheric reflection, frequency is brought up to 30MHz gradually from 1MHz, the data that calculate according to the 4th part according to the track and the characteristic of each bar ray, are predicted and are selected.

2, a kind of computational methods of predicting maximum usable frequency (MUF) of short-wave communication of the present invention, these method concrete steps are as follows:

Step 1:, determine the initial value of ray equation according to concrete operating position.

Ordinary circumstance, r is an earth radius, θ is the pi/2-geographic latitude, Be geographic logitude (0-360)

$k_r=\frac{\mathrm{\ω}}{c}\cos \mathrm{\β}$ $k_{\mathrm{\θ}}=-\frac{\mathrm{\ω}}{c}\cos \mathrm{\β}\cos \mathrm{\α},$

Wherein β is the emission inclination angle, and α is the emission drift angle, is specifically calculated by the longitude and latitude of launch point and acceptance point two places and obtains.

Step 2: utilize international ionosphere to make up electron concentration with reference to IRI and distribute, draw the distribution function relation of Appleton-Hartree formula X, common form is

Ne can be drawn by the IRI model, is and time, geographical coordinate, the relevant function of height above sea level.Table 1 is listed the formal parameter that certain IRI constantly predicts the electron concentration that obtains.

Step 3: introduce earth magnetic field model IGRF, introduce geomagnetic field intensity, reach the distribution function relation of geomagnetic declination, geomagnetic inclination.

Wherein:

θ ' is the angle in wave vector and magnetic field, and the calculating of θ ' is according to following formula

Wherein I is a magnetic dip angle, has a down dip to just, and updip is for negative; D is a magnetic declination, and from x axle steer H axle, east is partially for just, and is western partially for negative.

Step 4: utilize numerical solution differential equation method, find the solution the differential equation, wherein r, θ, k _r, k _θ, Every process a bit needs again at this point according to the Appleton-Hartree formula, according to the result that IRI and IGRF draw, calculating

Guarantee at utmost near actual conditions.The differential step-length adopts 0.1km, such precision can guarantee the needs that use.

Step 5: finally judge with the size of r whether ray arrives ground, will arrive the parameter extraction on ground then, as arriving the longitude and latitude on ground, during arrival the group path of process, and arrival angle.Can calculate great-circle distance between 2 according to the longitude and latitude of the longitude and latitude of place of arrival and launch point.These parameters can be obtained by ray tracing.

Step 6: for the reference as a result of ray tracing, Fig. 2 is scanning angle signal under the ray same frequency.

By information among the figure as can be known, under the condition of fixed transmission angle, along with the rising of frequency, the great-circle distance that ray can arrive constantly increases, and when frequency during greater than a critical value, can penetrate ionosphere, zip through space.Just ray can arrive the distance of a maximum along with the rising of frequency under the certain angle situation.

Step 7: general ray tracing is used, and under the certain frequency condition, the great-circle distance that ray can arrive reduces (involving low angle ripple situation comprising the angle of elevation) along with the increase at the elevation angle.Therefore on this basis MUF is estimated, mainly according to the maximum angle of ray emission, promptly ray can arrive minimum range on this angle, and great-circle distance and the direction deflection angle launched between receiving at 2 calculate.Usually constructing environment model as required, keep the emission maximum elevation angle and direction deflection angle constant then, then frequency is brought up to 30MHz gradually by 1MHz, with 0.1M is step-length, scanning calculate all rays the ground location that can arrive, calculate the great-circle distance under this frequency then, great-circle distance last and actual reception and emission point-to-point transmission compares, if greater than this great-circle distance, illustrate under this frequency, the minimum range that ray can arrive is greater than the great-circle distance between the two places, so this frequency is inapplicable in current the use.Ordinary circumstance, maximum usable frequency are chosen as the great-circle distance less than actual reception and emission point-to-point transmission, and near the frequency of this great-circle distance.

(3) advantage and effect:

The present invention adopted international ionosphere with reference to IRI and IGRF as the basis, set up the communication environments of ray, all bigger again raising on accuracy and confidence level.

In the use, only need just can predict that bigger breakthrough is arranged to maximum usable frequency MUF on practicality for the user to the corresponding geographical position of emission, acceptance point, parameters such as time, antenna directivity when prediction is used.As three-dimensional ray tracing technique, aspect visual, bigger advantage is arranged in addition, use this method more intuitively.

(4) description of drawings

Fig. 1 apparatus of the present invention structural principle schematic diagram

Scanning angle schematic diagram under Fig. 2 ray same frequency

Fig. 3 refractive index height above sea level distribution schematic diagram

Fig. 4 frequency is that schematic diagram is showed in the ray tracing under the 10MHz

It is 40_ estimation MUF schematic diagram that Fig. 5 sets maximum emission angle

(5) embodiment

1, as shown in Figure 1, a kind of device based on ray tracing technique prediction maximum usable frequency (MUF) of short-wave communication of the present invention, this device is made up of 5 modules: they are user's input module, environmental model module, make up spatial distribution module, the ray tracing property calculation module of refractive index and predict the maximum usable frequency expansion module according to magneto-ionic theory.Position between these five modules, annexation and signal trend are: initial by user's input module, condition when determining to use, import according to the user, the environmental model module is carried out modeling and is handled, according to the model of being set up, the spatial distribution module that makes up refractive index according to magneto-ionic theory makes up the refractive index spatial distribution, according to the refractive index spatial distribution, the ray tracing computing module carries out ray tracing and calculates, and predicts the data estimation maximum usable frequency MUF that the utilization of maximum usable frequency expansion module is calculated at last.

Described user's input module is the needs according to the user, the condition of using is set, and the main users interface has the emission mode, elevation coverage of tranmitting frequency, the ray of geographical latitude and longitude coordinates, the ray of current time set, launch point and acceptance point etc.Wherein input further is applied as and calculates great-circle distance and launch point direction deflection angle to acceptance point.

The computing formula of great-circle distance D is as follows:

D＝R×φ

The computing formula of direction deflection angle α of being pointed to place B by place A is as follows:

$\cos \mathrm{\α}=\frac{\sin \mathrm{latB}-\sin \mathrm{LatA}\·\cos \mathrm{\φ}}{\cos \mathrm{latA}}$

Wherein φ is drawn by following formula

cosφ＝sin?latA·sin?latB+cos?latA·cos?latB·cos(longA-longB)

This module is according to different application needs, ionosphere, earth magnetic field basic parameter under the different conditions of demand are set, with these basic parameters, make up the communication environments of ray, it is mainly imported the geographical longitude and latitude and the height above sea level in universal time, this zone by the user.

Described environmental model module is that international ionosphere is described with reference to the Mathematical Modeling of IRI and international earth magnetic field reference model IGRF, adopts the software encapsulation form to realize, is embedded in the computational methods.This module mainly needs according to the user, sets up the spatial distribution of electron concentration according to international ionosphere with reference to IRI, sets up the spatial distribution in earth magnetic field with reference to IGRF according to international earth magnetic field.Ionospheric fundamental forecasting data are set up according to ITU standard CC IR coefficient, have international universal applicability.The generally approval that the accuracy of earth magnetic field model also obtains estimating.

Described spatial distribution module according to magneto-ionic theory structure refractive index is to utilize magneto-ionic theory to make up the functional module of refractive index, and this module is utilized the environmental model of setting up previously, provides the spatial distribution of refractive index.The key foundation of ray-tracing algorithm foundation is a magneto-ionic theory in the patent, principal mode is the Appleton-Hartree formula, this formula has been set up the relation of refractive index with electron concentration and earth magnetic field spatial distribution ignoring under the condition of particle encounter, this formula is as follows:

$n^2=1-\frac{X(1-X)}{1-X-\frac{1}{2}{Y}_T^2\±\sqrt{\frac{1}{4}{Y}_T^4+Y_L^2{(1-X)}^2}}$

$\left.\begin{array}{c}{Y}_L^2=Y^2{\cos }^2\mathrm{\θ}\\ Y_T^2=Y^2{\sin }^2\mathrm{\θ}\end{array}\right\}$ $\left.\begin{array}{c}X=\frac{N_e{e}^2}{m{\mathrm{\ϵ}}_0{\mathrm{\ω}}^2}\\ Y=\frac{{\mathrm{\ω}}_H}{\mathrm{\ω}}\end{array}\right\}$ ${\mathrm{\ω}}_H=\frac{e{B}_0}{m}$

By formula as can be seen, wherein the distribution of electron concentration and earth magnetic field is a basic data of setting up refractive index, makes up three-dimensional refractive indexes according to these two data and distributes, and just framework has played whole ray propagates environment.N wherein _eNeed set up according to the IRI in the environmental model, and Y _LY _TTo set up according to earth magnetic field reference model IGRF.

Described ray tracing property calculation module is based on the functional module that ray tracing technique calculates ray tracing and ray arrival characteristic.This module is utilized ray equation under the spherical coordinates:

Wherein:

P is a group path.

Utilize the numerical differentiation equations system method to find the solution this equation on this basis, according to different frequencies and emission angle, different ray propagates environment, each track of ray calculates the most at last, the fundamental characteristics when obtaining ray arrival ground simultaneously.

Described prediction maximum usable frequency expansion module is based on an expanded application of ray tracing module result of calculation, and the condition of its control ray emission calculates corresponding ray characteristics, again according to these prediction of result maximum usable frequency MUF.According to maximum usable frequency is the definition of MUF, and ray is set the maximal rays elevation angle through the characteristic of ionospheric reflection, frequency is brought up to 30MHz gradually from 1MHz, the data that calculate according to the 4th part according to the track and the characteristic of each bar ray, are predicted and are selected.

The present invention has than high practicability, according to the international standard model, predicts environmental condition, does not need particular device and environmental condition in use.

2, a kind of computational methods of the present invention based on ray tracing technique prediction maximum usable frequency (MUF) of short-wave communication, these method concrete steps are as follows:

The maximum usable frequency pre-estimation:

Step 1: determine the geographical coordinate of launch point and acceptance point, calculate emission drift angle and great-circle distance

Launch point: Qingdao (36.1,120.3) acceptance point: Changchun (43.84,125.28)

Acceptance point is positioned at 24.6756 ° of launch point norths by east.Great-circle distance is 958.974km.

The great-circle distance of two places is fixed like this, can carry out the prediction of MUF.

Step 2: according to the actual conditions of applied forecasting, the initialization ionospheric model:

Example: the ionosphere situation that adopts the 2009-10-6 14:00 of IRI model prediction two places midpoint.

The characteristic parameter of ionosphere at that time such as the following table of IRI model prediction:

Table 1 utilizes the ionosphere characterisitic parameter of IRI model prediction computation

Project	Numerical values recited	Unit
			??Fof2	??10.582	??MHz
??M(3000)F2	??2.76041	??MHz
			??Hmf2	??340.32809	??Km
??Fof1	??4.63616	??MHz
			??Hmf1	??120.88902	??Km
??Foe	??3.26609	??MHz
			??Hme	??115.0	??Km
??Hmd	??81.04659	??Km

Project	Numerical values recited	Unit
			??Rz12	??44.9666
??B0	??203.406	??Km

Step 3: utilize IGRF prediction earth magnetism situation probably for the magnetic field size about 0.5 Gauss, constantly change with longitude and latitude, height above sea level.

For example concrete, 120.6 ° of prediction longitudes, 36.9 ° in latitude, height above sea level is the earth magnetic field distribution situation of 100km.

Table 2 utilizes the earth magnetic field characterisitic parameter of IGRF model prediction computation

Project	Numerical values recited	Unit
			The magnetic field overall strength	??0.49195	Gauss (ten thousand/tesla)
The inclination angle, magnetic field	??53.92418	Degree
			The drift angle, magnetic field	??34.46101	Degree
East component	??-0.032722	Degree
			North component	??0.287836	Degree
Vertical component	??0.397616	Degree

Step 4: pass through Appleton-Hartree formula with reference to IRI and international earth magnetic field with reference to IGRF according to international ionosphere, the ray communication environments is constructed the distribution of the refractive index of (between launch point and the acceptance point) with height above sea level, the frequency of ray is 12MHz.As Fig. 3 is refractive index height above sea level distribution schematic diagram.Refractive index when wherein the earth magnetic field is introduced in two curve representatives up and down distributes, the no earth magnetic field of intermediate curve representative situation.The just refractive index of enumerating in Fig. 3 under 12MHz distributes, and is a special case, will make up refractive index according to actual conditions generally speaking and distribute.

Step 5: make up the ray initial value,, generally need set,, calculate step by step, obtain the track of whole ray then according to numerical differentiation Equation for Calculating method to the initial value of ray for using.

In application this time:

R is 6370, and θ is pi/2-36.1*pi/180,

Be 120.3*pi/180

Wherein Kr is $k_r=\frac{\mathrm{\ω}}{c}\cos \mathrm{\β}$ $k_{\mathrm{\θ}}=-\frac{\mathrm{\ω}}{c}\cos \mathrm{\β}\cos \mathrm{\α},$

ω is the angular frequency of ray, and c is a light propagation velocity 3 * 10 in a vacuum ⁸M/s, α are 24.6756 °, and β is a launching elevation

Ray tracing application example: draw under the ray tracing fixed frequency ray tracing that scans such as Fig. 4: frequency is that the ray tracing under the 10MHz is showed.

Step 6: 40 ° of the maximum emission angles that ray is set, scanning frequency has 1MHZ-30MHz to the data output frequency, because frequency is greater than certain limit, then ray can penetrate ionosphere, so this part is disregarded, (data of this table are the parts of calculated data, but concrete reference paper is seen: MUF scan-data .xls) for data such as following table, concrete figure is Fig. 5, owing to show it is the scene of under three-dimensional, setting up, thus can't displaing coordinate, so result calculated is provided with form through calculating.

Table 3 is ray emission maximum elevation angle frequency scanning data outputs (selected parts) fixedly

Tranmitting frequency (MHZ) arrives latitude longitude in group path (Km) great-circle distance (Km)

6.1??????????????40.34???????122.88???????704.08???????522.00

6.4??????????????40.43???????122.94???????720.67???????533.98

6.7??????????????40.53???????123.01???????737.47???????546.17

7.0??????????????40.63???????123.07???????754.86???????558.75

7.3??????????????40.74???????123.14???????772.76???????571.68

7.6??????????????40.84???????123.21???????791.65???????584.87

7.9??????????????40.96???????123.29???????811.65???????599.00

8.2??????????????41.08???????123.37???????833.24???????614.36

8.5??????????????41.22???????123.46???????857.04???????631.30

8.8??????????????41.37???????123.56???????883.93???????650.50

9.1??????????????41.55???????123.68???????915.82???????673.26

9.4??????????????41.77???????123.84???????955.21???????700.46

9.7??????????????42.08???????124.05???????1010.00??????739.07

10.0?????????????42.65???????124.43???????1110.38??????809.78

10.1?????????????43.05???????124.72???????1181.86??????860.52

Step 7: find maximum usable frequency MUF10.1MHz, because the ray that surpasses under the high frequency frequency of 10.1MHz can penetrate ionosphere at 40 ° launching elevation, so this part is cast out, generally speaking, MUF is chosen as the most approaching and arrives the ray frequency of distance less than transmitting-receiving two places great-circle distance, and therefore, the predicted value of the MUF under this condition is 10.1MHz, for using, generally select 85%MUF as the employed frequency of short wave communication.Therefore it is proper the frequency of short wave communication can be chosen as 8.5MHz.

Claims (2)

1. One kind based on the prediction maximum usable frequency (MUF) of short-wave communication device, it is characterized in that: this device is made up of 5 modules, and they are user's input module, environmental model module, make up spatial distribution module, the ray tracing property calculation module of refractive index and predict the maximum usable frequency expansion module according to magneto-ionic theory; Position between these five modules, annexation and signal trend are: initial by user's input module, and the condition when determining to use, according to user's input, the environmental model module is carried out modeling and is handled; According to the model of being set up, the spatial distribution module that makes up refractive index according to magneto-ionic theory makes up the refractive index spatial distribution, according to the refractive index spatial distribution, the ray tracing computing module carries out ray tracing and calculates, and predicts the data estimation maximum usable frequency MUF that the utilization of maximum usable frequency expansion module is calculated at last;

   Described user's input module is the needs according to the user, and the condition of using is set, and ionosphere, earth magnetic field basic parameter under the different conditions of demand are set, and with these basic parameters, makes up the communication environments of ray; The main users interface has geographical latitude and longitude coordinates, the tranmitting frequency of ray, the emission mode of ray, the elevation coverage of current time set, launch point and acceptance point; Wherein input further is applied as and calculates great-circle distance and launch point direction deflection angle to acceptance point;

   The computing formula of great-circle distance D is as follows:

   D＝R×φ

   The computing formula of direction deflection angle α of being pointed to place B by place A is as follows:

   $\cos \mathrm{\α}=\frac{\sin \mathrm{latB}-\sin \mathrm{LatA}\·\cos \mathrm{\φ}}{\cos \mathrm{latA}}$

   Wherein: φ is drawn by following formula

   cosφ＝sin?latA·sin?latB+cos?latA·cos?latB·cos(longA-longB)；

   Described environmental model module is that international ionosphere is described with reference to the Mathematical Modeling of IRI and international earth magnetic field reference model IGRF, adopts the software encapsulation form to realize, is embedded in the computational methods; This module mainly needs according to the user, sets up the spatial distribution of electron concentration according to international ionosphere with reference to IRI, sets up the spatial distribution in earth magnetic field with reference to IGRF according to international earth magnetic field; Ionospheric fundamental forecasting data are set up according to ITU standard CC IR coefficient, have international universal applicability; The foundation of IRI model mainly is according to IRI model data, goes out the distribution situation of foF2 and M (3000) F2 based on the CCIR coefficient calculations, according to these two ionosphere resemblance parameters, derives other characteristic parameter one by one;

   Described spatial distribution module according to magneto-ionic theory structure refractive index is to utilize magneto-ionic theory to make up the functional module of refractive index, and this module is utilized the environmental model of setting up previously, provides the spatial distribution of refractive index; The key foundation of ray-tracing algorithm foundation is a magneto-ionic theory, and principal mode is the Appleton-Hartree formula, and this formula has been set up the relation of refractive index with electron concentration and earth magnetic field spatial distribution ignoring under the condition of particle encounter, and this formula is as follows:

   $n^2=1-\frac{X(1-X)}{1-X-\frac{1}{2}{Y}_T^2\±\sqrt{\frac{1}{4}{Y}_T^4+Y_L^2{(1-X)}^2}}$

   $\begin{array}{ccc}\left.\begin{array}{c}{Y}_L^2=Y^2{\cos }^2\mathrm{\θ}\\ Y_T^2=Y^2{\sin }^2\mathrm{\θ}\end{array}\right\}& \left.\begin{array}{c}X=\frac{N_e{e}^2}{m{\mathrm{\ϵ}}_0{\mathrm{\ω}}^2}\\ Y=\frac{{\mathrm{\ω}}_H}{\mathrm{\ω}}\end{array}\right\}& {\mathrm{\ω}}_H=\frac{e{B}_0}{m}\end{array}$

   Wherein: it is the basic data of setting up refractive index that electron concentration and earth magnetic field distribute, and makes up three-dimensional refractive index according to these two data and distributes, and just framework has played whole ray propagates environment; N _eNeed set up according to the IRI in the environmental model, and Y _LY _TTo set up according to earth magnetic field reference model IGRF;

   Described ray tracing property calculation module is based on the functional module that ray tracing technique calculates ray tracing and ray arrival characteristic, and this module is utilized ray equation under the spherical coordinates:

   

   Wherein:

   

   P is a group path; Utilize the numerical differentiation equations system method to find the solution this equation on this basis, according to different frequencies and emission angle, different ray propagates environment, each track of ray calculates the most at last, the fundamental characteristics when obtaining ray arrival ground simultaneously;

   Described prediction maximum usable frequency expansion module is based on an expanded application of ray tracing module result of calculation, and the condition of its control ray emission calculates corresponding ray characteristics, according to these prediction of result maximum usable frequency MUF; According to maximum usable frequency is the definition of MUF, and ray is set the maximal rays elevation angle through the characteristic of ionospheric reflection, frequency is brought up to 30MHz gradually from 1MHz, according to the data that calculate,, predict and select according to the track and the characteristic of each bar ray.
2. 2. a kind of computational methods of predicting maximum usable frequency (MUF) of short-wave communication of the present invention, it is characterized in that: these method concrete steps are as follows:

   Step 1:, determine the initial value of ray equation according to concrete operating position;

   R is an earth radius, and θ is the pi/2-geographic latitude, Be geographic logitude (0-360)

   $k_r=\frac{\mathrm{\ω}}{c}\cos \mathrm{\β}{k}_{\mathrm{\θ}}=-\frac{\mathrm{\ω}}{c}\cos \mathrm{\β}\cos \mathrm{\α},$

   

   Wherein: β is the emission inclination angle, and α is the emission drift angle, is specifically calculated by the longitude and latitude of launch point and acceptance point two places and obtains;

   Step 2: utilize international ionosphere to make up electron concentration with reference to IRI and distribute, draw the distribution function relation of Appleton-Hartree formula X, common form is

   

   Ne can be drawn by the IRI model, is and time, geographical coordinate, the relevant function of height above sea level;

   Step 3: introduce earth magnetic field model IGRF, introduce geomagnetic field intensity, reach the distribution function relation of geomagnetic declination, geomagnetic inclination;

   Wherein:

   

   Be the angle in wave vector and magnetic field, the calculating of θ ' is according to following formula

   

   Wherein: I is a magnetic dip angle, has a down dip to just, and updip is for negative; D is a magnetic declination, and from x axle steer H axle, east is partially for just, and is western partially for negative;

   Step 4: utilize numerical solution differential equation method, find the solution the differential equation, wherein r, θ, k _r, k _θ,

   

   Every process a bit needs again at this point according to the Appleton-Hartree formula, according to the result that IRI and IGRF draw, calculating

   

   

   Guarantee at utmost near actual conditions; The differential step-length adopts 0.1km, such precision can guarantee the needs that use;

   Step 5: finally judge with the size of r whether ray arrives ground, will arrive the parameter extraction on ground then; As arrive the longitude and latitude on ground, during arrival the group path of process, and arrive angle; Can calculate great-circle distance between 2 according to the longitude and latitude of the longitude and latitude of place of arrival and launch point; These parameters can be obtained by ray tracing;

   Step 6: with reference to screening, by information as can be known, under the condition of fixed transmission angle, along with the rising of frequency, the great-circle distance that ray can arrive constantly increases for the result of ray tracing, when frequency during greater than a critical value, can penetrate ionosphere, zip through space; Just ray can arrive the distance of a maximum along with the rising of frequency under the certain angle situation;

   Step 7: general ray tracing is used, under the certain frequency condition, the great-circle distance that ray can arrive reduces along with the increase at the elevation angle, therefore on this basis MUF is estimated, main maximum angle according to ray emission, be that ray can arrive minimum range on this angle, and great-circle distance and the direction deflection angle launched between receiving at 2 calculate; Usually constructing environment model as required, keep the emission maximum elevation angle and direction deflection angle constant then, then frequency is brought up to 30MHz gradually by 1MHz, with 0.1M is step-length, scanning calculate all rays the ground location that can arrive, calculate the great-circle distance under this frequency then, great-circle distance last and actual reception and emission point-to-point transmission compares, if greater than this great-circle distance, illustrate under this frequency, the minimum range that ray can arrive is greater than the great-circle distance between the two places, so this frequency is inapplicable in current the use; Ordinary circumstance, maximum usable frequency are chosen as the great-circle distance less than actual reception and emission point-to-point transmission, and near the frequency of this great-circle distance, select 85%MUF as the employed frequency of short wave communication usually.

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