JP2009069982A - Propagation route calculation device, propagation route calculation method, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a propagation route calculation device for faithfully calculating a propagation route near the reflection point of an electric wave, and for shortening a calculation time. <P>SOLUTION: This propagation route calculation device is provided with an electron density calculation part 11 for calculating electron density in the current calculation point of the propagation route of an electric wave; a refractive index calculation part 12 for calculating a refractive index on the basis of the electron density calculated by the electron density calculation part; a zenithal angle calculation part 13 for calculating the zenithal angle of the propagation route of the electric wave in the current calculation point on the basis of the refractive index calculated by the refractive index calculation part; and a step calculation part 14 for calculating a step representing a distance or a propagation time from the current calculation point to the next calculation point, and changing so as to become smaller according as the zenithal angle calculated by the zenithal angle calculation part becomes larger, according to the zenithal angle calculated by the zenithal angle calculation part 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a propagation path calculation device for calculating a propagation path of a radio wave propagating in an ionosphere, a propagation path calculation method, and a recording medium on which a program for realizing the propagation path calculation method is recorded.

  Conventionally, communication using the HF band (10 to 30 MHz) is performed. In the communication using this HF band, the radio wave emitted from the transmission source is reflected by the ionosphere existing above the earth, and propagates far away from the line-of-sight distance as an ionospheric reflection wave. In general, the lower the frequency, the easier the radio wave is reflected by the ionosphere, and the radio wave is attenuated when passing or reflecting through the ionosphere.

  By the way, since communication using the HF band is affected by the ionospheric state, in order to check whether the radio wave reaches a distant party, the radio wave emission angle, frequency, time zone, self position, etc. are used as variables. The propagation path of a radio wave is obtained by calculation. In the calculation of the propagation path, points (hereinafter referred to as “calculation points”) for performing the calculation for tracing the propagation path of the radio wave are sequentially set. The distance from one calculation point to the next calculation point or the radio wave propagation time is called “step”.

As a related technique, Non-Patent Document 1 discloses propagation of radio waves in the ionosphere, and Non-Patent Document 2 discloses a technique of calculating a propagation path of radio waves.
"International Reference Ionosphere 2000" Radio Science, Volume 36, Number 2, Page261-275, March / April 2001 "Effects of on Whistle-Mode Ray Tracing" RADIO SCIENCE, Vol 1 (New Series), No. 3, Page269-283, March 1966

  However, in the conventional technique for calculating the propagation path of the radio wave described above, the reflected state in the ionosphere cannot be reproduced unless the steps are made fine in the ionosphere portion of the radio wave propagation path, particularly in the vicinity of the reflection point.

  That is, if the step is rough, the next calculation point reaches a position higher than the place where it should be reflected, and the refractive index becomes complex, which is not normal. On the other hand, if the steps are made fine throughout the propagation path in order to accurately reproduce the path near the reflection point, enormous calculation time is required.

  An object of the present invention is to realize a propagation path calculation device, a propagation path calculation method, and a propagation path calculation method capable of accurately calculating a propagation path in the vicinity of a reflection point of radio waves and reducing the calculation time. It is to provide a recording medium on which a program is recorded.

  In order to solve the above-described problem, a propagation path calculation device according to the invention described in claim 1 is obtained by an electron density calculation unit that calculates an electron density at a current calculation point of a radio wave propagation path, and an electron density calculation unit. Refractive index calculator for calculating refractive index based on electron density, zenith angle calculator for calculating zenith angle of radio wave propagation path at current calculation point based on refractive index determined by refractive index calculator, and zenith angle calculator A step calculation unit for obtaining a step representing a distance or a propagation time from the current calculation point to the next calculation point and changing so as to decrease as the zenith angle increases according to the zenith angle determined in It is characterized by having.

  According to a second aspect of the present invention, there is provided a propagation path calculation method for obtaining an electron density at a current calculation point of a radio wave propagation path, obtaining a refractive index based on the obtained electron density, and obtaining the obtained refractive index. The zenith angle of the propagation path of the radio wave at the current calculation point is calculated based on the above, and the distance or propagation time from the current calculation point to the next calculation point is represented and the zenith angle is large according to the calculated zenith angle. It is characterized in that a step that changes so as to become smaller is obtained.

  According to a third aspect of the present invention, there is provided a computer readable recording medium for obtaining an electron density at a current calculation point of a radio wave propagation path, obtaining a refractive index based on the obtained electron density, and obtaining the obtained refractive index. The zenith angle of the propagation path of the radio wave at the current calculation point is obtained based on the refractive index, and the distance or propagation time from the current calculation point to the next calculation point is represented according to the obtained zenith angle and the zenith angle. A program for determining a step that changes so as to become smaller as the value becomes larger is stored.

  According to the first to third aspects of the present invention, the electron density at the current calculation point of the propagation path of the radio wave is obtained, the refractive index is obtained based on the electron density, and the propagation of the radio wave at the current calculation point is obtained based on the refractive index. Since the zenith angle of the path is obtained, and the step representing the distance or propagation time to the next calculation point and changing as the zenith angle increases is obtained according to the obtained zenith angle. In the vicinity of the ionospheric reflection point where the angle increases, the step becomes smaller and fine calculation is possible, and the propagation path can be calculated accurately. On the other hand, since the step is large except in the vicinity of the reflection point of the ionosphere where the zenith angle is small, the calculation time can be shortened.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a propagation path calculation apparatus according to Embodiment 1 of the present invention. The propagation path calculation device includes an electron density calculation unit 11, a refractive index calculation unit 12, a zenith angle calculation unit 13, and a step calculation unit 14, which are realized by software processing of a personal computer, for example.

  The electron density calculator 11 calculates the electron density at each calculation point set as a radio wave propagation path. FIG. 2A is a diagram showing changes in electron density in the D layer, E layer, F1 layer, and F2 layer forming the ionosphere. The electron density calculation unit 11 can be configured to obtain the electron density by calculation according to an electron density algorithm, and data indicating the relationship between the electron density and the height H as shown in FIG. It can also be configured by storing in advance.

  FIG. 2B is a diagram showing a state in which radio waves propagate through the ionosphere having the electron density as shown in FIG. The radio wave emitted at a predetermined elevation angle el and frequency reaches the reflection point at the lower part of the F2 layer while changing the path with a refractive index corresponding to the electron density of the ionosphere, and the radio wave reflected at this reflection point is It propagates while changing the path with a refractive index corresponding to the electron density of the to reach the earth's surface. The electron density calculated by the electron density calculator 11 is sent to the refractive index / propagation direction calculator 12.

  The refractive index / propagation direction calculation unit 12 calculates a refractive index at each calculation point based on the electron density sent from the electron density calculation unit 11, and calculates a propagation direction vector corresponding to the refractive index. The refractive index / propagation direction vector calculated by the refractive index / propagation direction calculation unit 12 is sent to the zenith angle calculation unit 13.

  The zenith angle calculation unit 13 is based on the propagation direction vector sent from the refractive index / propagation direction calculation unit 12 and forms the zenith angle of the propagation path of the radio wave at each calculation point, that is, the step propagation direction vector and the vertical direction. Calculate the corner. The zenith angle calculated by the zenith angle calculation unit 13 is sent to the step calculation unit 14.

  The step calculator 14 calculates a step (distance or propagation time) to the next calculation point according to the zenith angle sent from the zenith angle calculator 13. At this time, a step is required which changes so as to decrease as the zenith angle increases.

Specifically, the step calculator 14 obtains a step step by using a Fermi distribution function shown in the equation (1). The propagation path calculation apparatus according to the first embodiment is characterized in that the Fermi distribution function is used for the step calculation and the setting method of the Fermi level (α) and the portion (β) corresponding to the temperature.

here,
τ ₀ : Initial step value z: Angle formed by the propagation direction vector of the step and the vertical direction (zenith angle)
α: Zenith angle halving the initial step value (0 <α <π / 2)
β: a value that determines the amount of change in the vicinity of α of step β is obtained by the following equation (2).

here,
τ _min : Minimum step value The minimum step value τ _min is determined by the following equation (3) based on the transmission (reception) elevation angle el and the initial step value τ ₀ .

here,
el: Transmission (reception) elevation angle (0 ≦ el ≦ π / 2)
γ: constant (0 <γ <π / 2)
FIG. 3 is a diagram illustrating a state in which the step step obtained by the equation (1) changes according to the magnitude of the zenith angle z. It is shown that the step step decreases as the zenith angle z increases.

FIG. 4 is a diagram showing the relationship between the propagation direction vector and the zenith angle at each calculation point. When the height of the radio wave emitted at the elevation angle el increases, the refractive index increases and the zenith angle z increases ( z ₁ <z ₂ <z ₃ <z ₄ ...) is shown.

  Next, the operation of the propagation path calculation apparatus according to the first embodiment of the present invention configured as described above will be described with reference to the flowchart shown in FIG. Note that the propagation path calculation process shown in the flowchart of FIG. 5 focuses on the operation when the calculation point exists in the ionosphere.

First, an initial step value τ ₀ is set (step S11). The initial step value τ ₀ can be configured to be stored in advance in the step calculation unit 14, or can be configured to be set in the step calculation unit 14 from an input device (not shown).

  Next, the electron density is obtained (step S13). It is checked whether the ionosphere has entered the ionosphere depending on whether the electron density is equal to or higher than the reference value (step S12). That is, as a result of sequentially calculating the steps, it is checked whether the height of the calculation point has reached the height of the ionosphere. If it is determined in step S12 that there are no calculation points in the ionosphere, the process ends. In this case, although illustration is omitted, processing when the propagation path of the radio wave is other than the ionosphere, that is, calculation of the propagation path in a rough step is performed.

  On the other hand, if it is determined in step S12 that there is a calculation point in the ionosphere, then a refractive index propagation direction vector is obtained (step S14).

  That is, the refractive index / propagation direction calculation unit 12 calculates the refractive index / propagation direction vector at the current calculation point based on the electron density sent from the electron density calculation unit 11 and sends the vector to the zenith angle calculation unit 13.

  Next, the zenith angle is obtained from the propagation direction vector (step S15). That is, the zenith angle calculation unit 13 is based on the refractive index sent from the refractive index / propagation direction calculation unit 12 and the propagation direction vector of the radio wave for the current calculation point, and the zenith angle of the radio wave propagation path at the current calculation point. Is sent to the step calculator 14.

  Next, step calculation is performed (step S16). That is, the step calculation unit 14 calculates a step (distance or propagation time) from the current calculation point to the next calculation point in accordance with the zenith angle sent from the zenith angle calculation unit 13. Next, the next calculation point is set (step S17). That is, the step calculation unit 14 sets the next calculation point based on the step calculated in step S16.

  Next, the electron density is obtained (step S13), and it is checked whether or not it has exited the ionosphere (step S12). If it is determined in step S12 that the calculation point is not in the ionosphere, the process returns to step S14 and the above-described processing is repeated. As a result, as shown in FIG. 4, step steps are sequentially calculated, and a radio wave propagation path is obtained.

  On the other hand, if it is determined in step S12 that the calculation point is not in the ionosphere, the process ends. In this case, although illustration is omitted, processing is performed when the propagation path of radio waves is other than the ionosphere.

  As described above, according to the propagation path calculation apparatus according to the first embodiment of the present invention, in the vicinity of the reflection point of the ionosphere where the zenith angle increases, the step becomes smaller and fine calculation is possible, and the propagation path is accurately determined. Can be calculated. On the other hand, the calculation time can be reduced because the step is large except in the vicinity of the reflection point of the ionosphere where the zenith angle is small.

  Note that the procedure shown in the flowchart of FIG. 5 can be realized by a computer program, stored in a recording medium such as a hard disk, and executed on a computer as necessary.

  The present invention is applicable to a communication device that performs communication in, for example, the HF band.

It is a figure which shows the structure of the propagation path calculation apparatus which concerns on Example 1 of this invention. It is a figure which shows a mode that the propagation path calculation apparatus which concerns on Example 1 of this invention uses the change of the electron density of the ionosphere utilized for calculation of a propagation path, and a mode that an electromagnetic wave propagates through an ionosphere. It is a figure which shows the relationship between the step calculated by the step calculation part of the propagation path calculation apparatus which concerns on Example 1 of this invention, and a zenith angle. It is a figure which shows the relationship between the refractive index and the zenith angle in each calculation point of the propagation path calculated in the propagation path calculation apparatus which concerns on Example 1 of this invention. It is a flowchart which shows operation | movement of the propagation path calculation apparatus which concerns on Example 1 of this invention.

Explanation of symbols

11 Electron density calculator 12 Refractive index / propagation direction calculator 13 Zenith angle calculator 14 Step calculator

Claims (3)

An electron density calculator that calculates the electron density at the current calculation point of the radio wave propagation path;
A refractive index calculation unit for obtaining a refractive index based on the electron density obtained by the electron density calculation unit;
A zenith angle calculation unit for determining the zenith angle of the propagation path of the radio wave at the current calculation point based on the refractive index obtained by the refractive index calculation unit;
According to the zenith angle obtained by the zenith angle calculation unit, the step represents the distance or propagation time from the current calculation point to the next calculation point, and changes so as to decrease as the zenith angle increases. A step calculation unit to be obtained;
A propagation path calculation device comprising: Find the electron density at the current calculation point of the radio wave propagation path,
A refractive index is obtained based on the obtained electron density,
Based on the obtained refractive index, find the zenith angle of the propagation path of the radio wave at the current calculation point,
According to the obtained zenith angle, a step representing a distance or a propagation time from the current calculation point to the next calculation point and changing so as to decrease as the zenith angle increases is obtained. Propagation path calculation method. Find the electron density at the current calculation point of the radio wave propagation path,
A refractive index is obtained based on the obtained electron density,
Based on the obtained refractive index, find the zenith angle of the propagation path of the radio wave at the current calculation point,
A program for obtaining a step representing a distance or propagation time from the current calculation point to the next calculation point and changing so as to decrease as the zenith angle increases in accordance with the calculated zenith angle. A computer-readable recording medium characterized by being stored.

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