JP7478054B2 - Electric field strength calculation device and program - Google Patents

Description

The present invention relates to a field strength calculation device and program that calculates the field strength at a receiving point receiving a medium wave.

Conventionally, the electric field strength at the receiving point of a medium wave radio broadcast has a long wavelength of several hundreds of meters and is calculated as the strength of surface waves that propagate along the ground during the daytime. In the case of mixed path propagation where the electrical constants of the ground in the propagation path, including the sea, plains, and mountains, are different, the Millington method described in Ministry of Posts and Telecommunications Notification No. 640 (Non-Patent Document 1) (see, for example, Non-Patent Document 2) is widely used to calculate the electric field strength.

A method for calculating the service area of medium wave broadcasting using the Millington method has also been reported (see, for example, non-patent document 3). This method for calculating the electric field strength using the Millington method uses the formula and electric field strength curve described in the aforementioned non-patent document 1 to determine the electric field strength at the receiving point.

Specifically, this method determines the terrain classification at regular distances along the propagation path (straight-line propagation path) that connects the transmitting point and the receiving point over the shortest distance, and then determines the earth conductivity according to the terrain classification.

This method uses a field strength curve corresponding to the earth's conductivity to calculate the field strength in the forward direction of the propagation path (from the transmitting point to the receiving point) and in the reverse direction (from the receiving point to the transmitting point), and then calculates the field strength at the receiving point by taking the geometric mean.

“Method of calculating electric field strength when determining the broadcasting area, etc. based on the calculated electric field strength pursuant to the provisions of Article 7, Paragraph 2 of the Radio Station Licensing Procedure Regulations”, [online], Ministry of Posts and Telecommunications Notification No. 640, [searched June 15, 2020], Internet <URL: https://www.tele.soumu.go.jp/horei/reiki_honbun/a720730001.html> Rec. ITU-R P.368-9 Annex 2, “GROUND-WAVE PROPAGATION CURVES FOR FREQUENCIES BETWEEN 10 kHz AND 30 MHz”, 2007. Okamoto et al., "Automatic Calculation of AM Broadcasting Service Areas," 2001 Annual Conference of the Institute of Image Information and Television Engineers, 20-1

However, the electric field strength calculation method using the Millington method described above had a problem in that, for example, when the straight-line propagation path between the transmitting point and the receiving point included mountain propagation, the calculated value and the actual measured value differed significantly, making it impossible to obtain highly accurate electric field strength.

This is because the Millington method may not be able to accurately reflect the effects of diffraction due to mountains, etc. in the electric field strength. For this reason, it has been desirable to calculate electric field strength with high accuracy by, for example, reflecting the effects of diffraction due to mountains, etc.

The present invention has been made to solve the above problems, and its purpose is to provide a field strength calculation device and program that can accurately calculate the field strength at a receiving point that receives medium waves.

In order to solve the above problem, the electric field strength calculation device of claim 1 is an electric field strength calculation device that calculates an electric field strength of a reception point receiving a medium wave, the electric field strength calculation device comprising: a propagation path calculation unit that calculates propagation path information indicating the latitude and longitude of a straight line route from the transmission point to the reception point from transmission point information indicating the latitude and longitude of a preset transmission point and reception point information indicating the longitude and latitude of the reception point, calculates a first Fresnel zone when the transmission point is viewed from the reception point based on the transmission point information, the reception point information, and the medium wave frequency, sets either the right end or the left end of the first Fresnel zone as an end route with reference to the earth's surface, and calculates the propagation path information of the end route; an electric field strength calculation unit that determines a terrain classification for each of the straight line route and the end route along a route indicated by the corresponding propagation path information using preset terrain classification data for each predetermined distance, and calculates an electric field strength E _m of the reception point in accordance with the terrain classification by a predetermined electric field strength calculation method of the Millington method; and _and a field intensity averaging unit which calculates an average value of the field intensity E _m of the route of the end and outputs the average value as the field intensity of the receiving point.

The electric field strength calculation device according to claim 2 calculates the electric field strength of a reception point receiving a medium wave, and calculates propagation path information indicating the latitude and longitude of a straight line route from the transmission point to the reception point from transmission point information indicating the latitude and longitude of a preset transmission point and reception point information indicating the longitude and latitude of the reception point, calculates a first Fresnel zone when the transmission point is seen from the reception point based on the transmission point information, the reception point information, and the frequency of the medium wave, and calculates a right end of the first Fresnel zone clockwise with the earth's surface as a reference. a propagation path calculation unit which sets the left end of the first Fresnel zone as a clockwise route with respect to the earth's plane and calculates the propagation path information of the counterclockwise route, and sets the left end of the first Fresnel zone as a counterclockwise route with respect to the earth's plane and calculates the propagation path information of the counterclockwise route; a field strength calculation unit which calculates a terrain classification for each of the straight line route, the clockwise route and the counterclockwise route along a route indicated by the corresponding propagation path information using preset terrain classification data for each predetermined distance, and calculates an electric field strength E _m of the reception point in accordance with the terrain classification by a predetermined electric field strength calculation method of the Millington method; and a field strength averaging unit which calculates an average value of the electric field strength E _m of the straight line route, the electric field strength E _m of the clockwise route and the electric field strength E _m of the counterclockwise route calculated by the field strength calculation unit, and outputs this as the electric field strength of the reception point.

According to a third aspect of the present invention, there is provided an electric field strength calculation device according to the first or second aspect, wherein the electric field strength calculation unit includes a propagation path terrain classification processing unit, a Millington method calculation unit, a diffraction point detection unit, a shielding loss calculation unit, and an electric field strength processing unit, each corresponding to a plurality of routes in the propagation path information calculated by the propagation path calculation unit, and the propagation path terrain classification processing unit determines the terrain classification for each of the predetermined distances using the terrain classification data along the route indicated by the propagation path information, and the Millington method calculation unit calculates the electric field strength E according to the terrain classification determined by the propagation path terrain classification processing unit by the electric field strength calculation method of the Millington method. the _diffraction point detection unit generates topographical cross-sectional data for each predetermined distance between the transmission point and the reception point based on the propagation path information and preset altitude data, and detects all diffraction points existing between the transmission point and the reception point based on the topographical cross-sectional data, the shadowing loss calculation unit calculates a power loss tmp for each of all the diffraction points detected by the diffraction point detection unit, and obtains the largest power loss tmp among the power loss tmp of all the diffraction points as the shadowing loss _E , or obtains a sum of the power loss tmp of all the diffraction points as the shadowing loss _E , the electric field strength processing unit subtracts the shadowing loss _E calculated by the shadowing loss calculation unit from the electric field strength _E calculated by the Millington method calculation unit to obtain an individual electric field strength of the reception point, and the electric field strength averaging unit obtains an average value of the individual electric field strengths calculated by the electric field strength processing units corresponding to each of the plurality of routes, and outputs the average value as the electric field strength of the reception point.

According to a fourth aspect of the present invention, there is provided a field strength calculation device for calculating a field strength at a reception point receiving a medium wave, the field strength calculation device comprising: a propagation path calculation unit for calculating propagation path information indicating the latitude and longitude of a straight line route from a transmission point to the reception point from transmission point information indicating the latitude and longitude of a preset transmission point and reception point information indicating the longitude and latitude of the reception point; and a field strength calculation unit for calculating the field strength at the reception point, the field strength calculation unit further comprising: a propagation path terrain classification processing unit for determining a terrain classification for each predetermined distance using preset terrain classification data along a route indicated by the propagation path information of the straight line route calculated by the propagation path calculation unit; and a field strength calculation unit for calculating the field strength E of the reception point according to the terrain classification determined by the propagation path terrain classification processing unit, the field strength calculation unit further comprising: a propagation path terrain classification processing unit for determining a terrain classification for each predetermined distance along a route indicated by the propagation path information of the straight line route calculated by the propagation path calculation unit, the propagation path terrain classification processing unit for determining a terrain classification for each predetermined distance using a predetermined terrain classification data, and a field strength calculation method according to a predetermined Millington method field strength calculation method. a _diffraction point detection unit that generates topographical cross-sectional data for each predetermined distance between the transmission point and the reception point based on the propagation path information of the straight line route and preset altitude data, and detects all diffraction points existing between the transmission point and the reception point based on the topographical cross-sectional data; a shadowing loss calculation unit that calculates a power loss tmp for each of all the diffraction points detected by the diffraction point detection unit, and determines a sum of the power loss tmp of all the diffraction points as a shadowing loss _E , or determines the largest power loss tmp of all the diffraction points as the shadowing loss _E ; and a field strength processing unit that subtracts the shadowing loss _EL calculated by the shadowing loss calculation unit from the field strength _E calculated by the Millington method calculation unit to determine the field strength of the reception point.

Furthermore, the program of claim 5 is characterized in that it causes a computer to function as the electric field strength calculation device of any one of claims 1 to 4.

As described above, according to the present invention, it is possible to calculate the electric field strength at the receiving point where the medium wave is received with high accuracy.

1 is a block diagram showing an example of the configuration of a field intensity calculation device according to a first embodiment; 4 is a flowchart illustrating an example of processing performed by the electric field intensity calculation device according to the first embodiment. 1A to 1C are diagrams for explaining propagation paths of a straight route and a clockwise route and a counterclockwise route calculated from a first Fresnel zone. 4 is a block diagram showing an example of the configuration of a field intensity calculation unit; FIG. 13 is a flowchart illustrating an example of processing by a field intensity calculation unit. FIG. 1 is a diagram showing an example of correspondence between topographic classification of the National Land Numerical Information and electrical conductivity. 11 is a diagram showing an example of the electric field strength at each point (transmission point → reception point) calculated by the Millington method calculation unit. FIG. 13 is a diagram showing an example of the electric field intensity at a discontinuous point (transmission point → reception point) corrected by the Millington method calculation unit. FIG. 11 is a diagram showing an example of the electric field strength at each point (receiving point → transmitting point) calculated by the Millington method calculation unit. FIG. 13 is a flowchart showing an example of processing by a diffraction point detection unit. 11A and 11B are diagrams illustrating an example of processing by a diffraction point detection unit. 13 is a flowchart illustrating an example of processing by a shielding loss calculation unit. FIG. 12 is a diagram for explaining a calculation example of the shielding coefficient x (step S1201); FIG. 11 is a block diagram showing a configuration example of a field intensity calculation device according to a second embodiment. FIG. 11 is a block diagram showing a configuration example of a field intensity calculation device according to a third embodiment. FIG. 13 is a block diagram showing a configuration example of an electric field strength calculation unit in the third embodiment.

The following describes in detail the embodiments of the present invention with reference to the drawings. The present invention is characterized in that it calculates the electric field strength at the receiving point by taking into account the shielding loss (nearby ridge loss) caused by diffraction of mountains, etc., in addition to the electric field strength calculated using the Millington method. This makes it possible to obtain highly accurate medium wave electric field strength even in propagation paths that include mountain propagation.

The present invention is also characterized by calculating the electric field strength at the receiving point by considering a propagation path that takes into account the Fresnel zone in addition to the conventional propagation path of a straight line route that connects the transmitting and receiving points by the shortest distance. This makes it possible to reduce the difference between the calculated value and the actually measured value for the electric field strength of medium wave.

Example 1
First, a description will be given of a field intensity calculation device according to Example 1. Example 1 is an example in which the field intensity at a receiving point is calculated by taking into account shielding loss due to diffraction by mountains and the like, in addition to the field intensity calculated by the Millington method, using a straight line route propagation path and a propagation path taking into account the Fresnel zone.

Figure 1 is a block diagram showing an example of the configuration of a field strength calculation device of the first embodiment, and Figure 2 is a flowchart showing an example of the processing of the field strength calculation device of the first embodiment.

This electric field strength calculation device 1 includes a propagation path calculation unit 10, electric field strength calculation units 11-1, 11-2, and 11-3, and an electric field strength averaging unit 12.

The propagation path calculation unit 10 inputs the transmission point information and the reception point information (step S201). Then, the propagation path calculation unit 10 calculates propagation path information of a straight line route from the transmission point information and the reception point information, calculates a first Fresnel zone from the transmission point information and the reception point information, and calculates propagation path information of a right-handed route and a left-handed route (step S202). This allows the propagation path information of the right-handed route and the left-handed route taking into account the first Fresnel zone to be obtained.

The propagation path calculation unit 10 outputs propagation path information for the counterclockwise route to the electric field strength calculation unit 11-1, outputs propagation path information for the straight route to the electric field strength calculation unit 11-2, and outputs propagation path information for the clockwise route to the electric field strength calculation unit 11-3. Details of the propagation path calculation unit 10 will be described later.

The transmitting point information consists of the latitude and longitude of the transmitting point that transmits radio waves. The receiving point information consists of the latitude and longitude of the receiving point that receives radio waves. The propagation path information consists of the latitude and longitude for each specified distance between the transmitting and receiving points.

The electric field strength calculation units 11-1, 11-2, and 11-3 respectively input the propagation path information of the counterclockwise route, the propagation path information of the straight route, and the propagation path information of the clockwise route from the propagation path calculation unit 10.

The electric field strength calculation units 11-1, 11-2, and 11-3 calculate the electric field strength E _m of the reception point for each of the left-handed route, the straight route, and the right-handed route by the Millington method, and detect the diffraction points to calculate the shadowing loss E _L. Then, the electric field strength calculation units 11-1, 11-2, and 11-3 subtract the shadowing loss E _L from the electric field strength E _m to obtain the electric field strength (individual electric field strength) of the reception point (step S203). As a result, the electric field strength of the reception point of the left-handed route, the electric field strength of the reception point of the straight route, and the electric field strength of the reception point of the right-handed route taking into account the propagation path diffraction (shadowing loss E _L due to diffraction) can be obtained.

The electric field strength calculation unit 11-1 outputs the electric field strength of the reception points on the counterclockwise route to the electric field strength averaging unit 12, and the electric field strength calculation unit 11-2 outputs the electric field strength of the reception points on the straight route to the electric field strength averaging unit 12. The electric field strength calculation unit 11-3 outputs the electric field strength of the reception points on the clockwise route to the electric field strength averaging unit 12. Details of the electric field strength calculation units 11-1, 11-2, and 11-3 will be described later.

The electric field strength averaging unit 12 inputs the electric field strength of the reception points on the counterclockwise route from the electric field strength calculation unit 11-1, and also inputs the electric field strength of the reception points on the straight route from the electric field strength calculation unit 11-2. The electric field strength averaging unit 12 also inputs the electric field strength of the reception points on the clockwise route from the electric field strength calculation unit 11-3.

The electric field intensity averaging unit 12 calculates the average value of the electric field intensity at the reception point on the counterclockwise route, the electric field intensity at the reception point on the straight route, and the electric field intensity at the reception point on the clockwise route, and outputs this as the electric field intensity at the reception point (step S204). This allows the electric field intensity at the reception point to be obtained, taking into account the first Fresnel zone and the shielding loss E _L due to diffraction.

(Propagation Path Calculation Unit 10)
Next, a detailed description will be given of the propagation path calculation unit 10 shown in Fig. 1. The propagation path calculation unit 10 calculates propagation path information (latitude and longitude for each predetermined distance between the transmitting and receiving points) of a straight line route between the transmitting and receiving points based on the transmitting point information (latitude and longitude) and the receiving point information (latitude and longitude).

The propagation path calculation unit 10 calculates the first Fresnel zone when the transmitting point is viewed from the receiving point with respect to the Earth's surface based on the distance between the transmitting and receiving points obtained from the transmitting point information and the receiving point information, and the frequency of the radio waves.

The propagation path calculation unit 10 sets the route that passes through the right edge of the spheroid that is the shape of the first Fresnel zone, based on the Earth's surface when viewed from the receiving point to the transmitting point, as a clockwise route, and calculates the propagation path information for the clockwise route. Similarly, the propagation path calculation unit 10 sets the route that passes through the left edge as a counterclockwise route, and calculates the propagation path information for the counterclockwise route.

Figure 3 is a diagram explaining the propagation paths of the straight line route and the clockwise and counterclockwise routes calculated from the first Fresnel zone. As shown in Figure 3, the propagation path calculation unit 10 sets a straight line route from the transmission point to the reception point, a clockwise route that passes through the right end of the first Fresnel zone, and a counterclockwise route that passes through the left end of the first Fresnel zone.

(Field Intensity Calculation Units 11-1, 11-2, 11-3)
Next, the electric field strength calculation units 11-1, 11-2, and 11-3 shown in Fig. 1 will be described in detail. The electric field strength calculation units 11-1, 11-2, and 11-3 perform the same process. Hereinafter, the electric field strength calculation units 11-1, 11-2, and 11-3 will be collectively referred to as the electric field strength calculation unit 11.

Fig. 4 is a block diagram showing an example of the configuration of the electric field strength calculation unit 11, and Fig. 5 is a flowchart showing an example of the processing of the electric field strength calculation unit 11. This electric field strength calculation unit 11 includes a propagation path topography classification processing unit 20, a Millington method calculation unit 21, a diffraction point detection unit 22, a shielding loss calculation unit 23, and an electric field strength processing unit 24. The processing of steps S502 and S503 described below by the propagation path topography classification processing unit 20 and the Millington method calculation unit 21 is processing according to the conventional electric field strength calculation method of the Millington method described in the above-mentioned non-patent documents 1 to 3.

The electric field strength calculation unit 11 inputs propagation path information (latitude and longitude for each predetermined distance between the transmitting and receiving points) of the corresponding route (either a left-handed route, a straight route, or a right-handed route) from the propagation path calculation unit 10 (step S501).

The propagation path terrain classification processing unit 20 inputs the propagation path information and also inputs the preset terrain classification data. Then, the propagation path terrain classification processing unit 20 uses the terrain classification data to determine the terrain classification for each predetermined distance (e.g., every 100 m) from the transmission point to the reception point along the propagation path indicated by the propagation path information (step S502). The propagation path terrain classification processing unit 20 outputs the terrain classification for each predetermined distance of the propagation path to the Millington method calculation unit 21.

For example, land classification mesh data (1 km mesh) from the National Land Numerical Information is used as the terrain classification data. When the propagation path terrain classification processing unit 20 uses the land classification mesh data (1 km mesh) from the National Land Numerical Information to determine the terrain classification for every 100 m, it treats all points within the 1 km mesh as having the same land classification. In addition, the terrain classification determined by the propagation path terrain classification processing unit 20 is "mountainous area (mountains)", "hilly area (hills)", "plain area (plains)", or "ocean".

Figure 6 is a diagram showing an example of the correspondence between the topography classification of the National Land Numerical Information and electrical conductivity. This correspondence example is a table that associates the main classification code and main classification, which are the topography classification of the National Land Numerical Information, with the division (topography classification) and the electrical conductivity of the earth (earth electrical conductivity) σ [mS/m]. The propagation path topography classification processing unit 20 uses the land classification mesh data of the National Land Numerical Information to identify the main classification code and main classification for each specified distance, identifies the corresponding division (topography classification), and outputs the topography classification for each specified distance to the Millington method calculation unit 21.

The propagation path terrain classification processing unit 20 may determine the terrain classification for every 100 m of the propagation path, or may determine the terrain classification in units other than 100 m.

The Millington method calculation unit 21 calculates the electric field strength E m at the receiving point by using the earth conductivity (see FIG _{. 6} ) corresponding to the topographical classification according to the electric field strength calculation method of the Millington method shown in the Ministry of Posts and Telecommunications Notification No. 640 of the above-mentioned Non-Patent Document 1 (step S503). Hereinafter, a method of calculating the electric field strength when the propagation path of the radio wave is a mixed path (a propagation path including a section with different earth conductivity and relative dielectric constant) will be described.

In general, the electric field strength E is calculated by the following formula:
[Equation 1]
E = E _m × √ ( G _η × D (θ) × P _t ) [mV/m] ... (1)
G _η is the antenna apparent efficiency, P _t is the antenna power, E _m is the electric field strength in the mixed path when the antenna power is 1 kW, and D(θ) is the antenna directivity coefficient.

The antenna directivity coefficient D(θ) is data that satisfies the following formula:
[Equation 2]
D(θ)=Dv(θv)+Dh(θh) [dB] (2)
Dv (θv) indicates vertical plane directivity, θv indicates the tilt angle in the direction of the reception point, Dh (θh) indicates horizontal plane directivity, and θh indicates the horizontal angle in the direction of the reception point.

The Millington method calculation unit 21 inputs the terrain classification for each predetermined distance of the propagation path from the propagation path terrain classification processing unit 20, and also inputs data on the electric field strength curve for each earth conductivity according to a preset terrain classification (see, for example, the aforementioned non-patent document 1).

The Millington method calculation unit 21 uses the electric field strength curve for each earth conductivity according to the terrain classification to calculate the electric field strength at points at a predetermined distance (for example, every 100 m) along the propagation path from the transmitting point to the receiving point, corrects for discontinuous points, and calculates the electric field strength _Ea at the receiving point (transmitting point → receiving point). A specific description will be given below.

Figure 7 shows an example of the electric field strength at each point (transmission point → reception point) calculated by the Millington method calculation unit 21. The horizontal axis shows the distance [km] from the transmission point to the reception point, and the vertical axis shows the electric field strength [dBμV/m]. α is the electric field strength curve for a terrain classified as "ocean" (earth conductivity σ = 6 [mS/m]), β is the electric field strength curve for a terrain classified as "plain" (earth conductivity σ = 2 [mS/m]), and γ is the electric field strength curve for a terrain classified as "mountain" (earth conductivity σ = 1 [mS/m]). Earth conductivity σ is an example.

The Millington method calculation unit 21 determines, from the terrain classification for each specified distance of the input propagation path, that the terrain classification for the area between the transmitting point and 10 km is "ocean," the terrain classification for the area between 10 km and 20 km is "plains," and the terrain classification for the area between 20 km and the receiving point is "mountainous."

The Millington method calculation unit 21 uses the electric field strength curves α, β, and γ for each earth conductivity σ corresponding to the terrain classifications "ocean," "plain," and "mountain" to calculate the electric field strength (characteristics of the square ■) at points at each specified distance. Here, the electric field strength at each point is calculated independently, so the electric field strength becomes discontinuous at the boundary between different terrain classifications (see the points around the 10 km point and the 20 km point).

Therefore, the Millington method calculation unit 21 uses the following formula to correct the electric field strength at the discontinuous points shown in Figure 7 to obtain the corrected electric field strength, and then obtains the electric field strength _Ea of the receiving point from the transmitting point to the receiving point (transmitting point → receiving point) from the corrected electric field strength.
[Equation 3]
E _a = E ₁ - ( E ₂ - E ₃ ) - ( E ₄ - E ₅ ) ... (3)

FIG. 8 is a diagram showing an example of the electric field strength at a discontinuous point (transmission point → reception point) corrected by the Millington method calculation unit 21. The vertical axis, horizontal axis, and electric field strength curves α, β, and γ are the same as those in FIG. 7. E ₁ indicates the electric field strength at a distance of 10 km, which is a discontinuous point, in the electric field strength curve of "ocean". E ₂ indicates the electric field strength at a distance of 10 km, which is a discontinuous point, in the electric field strength curve of "plain". E ₃ indicates the electric field strength at a distance of 20 km, which is a discontinuous point, in the electric field strength curve of "plain". E ₄ indicates the electric field strength at a distance of 20 km, which is a discontinuous point, in the electric field strength curve of "mountain". E ₅ indicates the electric field strength at the reception point in the electric field strength curve of "mountain". These electric field strengths E ₁ , E ₂ , E ₃ , E ₄ , and E ₅ are used in the above formula (3).

In other words, the Millington method calculation unit 21 uses the electric field strength curve of the terrain classification of the point including the transmission point (the thick curve on the left side of Figure 8) as a reference (fixed) so that the electric field strength curve from the transmission point to the reception point has continuous characteristics (the corrected electric field strength curve ρ shown in Figure 8), and shifts the electric field strength curves of other terrain classifications by a predetermined strength (( _E1 - _E2 ) from the discontinuous point at a distance of 10 km to a distance of 20 km, and (( _E1 - _E2 ) + ( _E4 - _E3 )) from the discontinuous point at a distance of 20 km to the reception point), and finds the electric field strength (transmission point → reception point) _Ea at the reception point.

4 and 5, similarly, the Millington method calculation unit 21 obtains the electric field strength at each point along the propagation path from the receiving point to the transmitting point, as shown in FIG. 9 described later, and then corrects for discontinuous points to obtain the electric field strength _Eb at the transmitting point (receiving point → transmitting point).

Specifically, the Millington method calculation unit 21 determines, from the terrain classification for each specified distance of the input propagation path, that the terrain classification for the area between the receiving point and 10 km is "mountainous," the terrain classification for the area between 10 km and 20 km is "plain," and the terrain classification for the area between 20 km and the transmitting point is "marine."

The Millington method calculation unit 21 uses the electric field strength curves γ, β, α for each earth conductivity σ corresponding to the terrain classifications "mountainous," "plain," and "marine" to determine the electric field strength at each point at a specified distance (the characteristics of the square ■ in Figure 9 described later, and the characteristics of the square ■ hidden by the thick line in areas where the terrain classification is "mountainous"). Here, as in the case above, the electric field strength becomes discontinuous at the boundary between different terrain classifications (see the points around the 10 km point and the 20 km point in Figure 9 described later).

The Millington method calculation unit 21 corrects the electric field strength at the discontinuous points shown in FIG. 9 described later using the same process as described above, thereby obtaining the corrected electric field strength, and calculates the electric field strength _Eb of the transmission point from the reception point to the transmission point (reception point → transmission point) from the corrected electric field strength.

Fig. 9 is a diagram showing an example of the electric field strength (receiving point → transmitting point) at each point calculated by the Millington method calculation unit 21. The vertical axis, horizontal axis, and electric field strength curves α, β, and γ are the same as those in Fig. 7. In other words, the Millington method calculation unit 21 shifts the electric field strength curves of other terrain classes by a predetermined strength using the electric field strength curve of the terrain class including the receiving point (thick curve on the left side of Fig. 9) as a reference (fixed) so that the electric field strength curve between the receiving point and the transmitting point has continuous characteristics (corrected electric field strength curve ρ' shown in Fig. 9), and calculates the electric field strength (receiving point → transmitting point) _Eb of the transmitting point.

4 and 5, the Millington method calculation unit 21 calculates the electric field strength E m of the reception point from the electric field strength (transmission point → reception point) E _a and the electric field strength (reception point → transmission point) E _b by the following formula. Then, the Millington method calculation unit 21 outputs _{the electric field strength E m of} the reception point to the electric field strength processing unit 24.
[Equation 4]
E _m =√( E _a ×E _b ) ... (4)

The diffraction point detection unit 22 inputs the propagation path information and preset altitude data. The altitude data is data indicating the altitude (height above sea level) of each point based on, for example, a 50 m mesh. The diffraction point detection unit 22 then generates topographical cross section data for each specified distance between the transmitting and receiving points based on the propagation path information and the altitude data, and detects all diffraction points that exist between the transmitting and receiving points based on the topographical cross section data (step S504). The diffraction point detection unit 22 may detect one diffraction point, may detect multiple diffraction points, or may not be able to detect (do not detect) any diffraction points.

The diffraction point detection unit 22 determines whether or not a diffraction point has been detected in step S504 (step S505), and if a diffraction point has been detected (if a diffraction point is present) (step S505: Y), outputs the latitude, longitude, and altitude data for each diffraction point to the shielding loss calculation unit 23. On the other hand, if the diffraction point detection unit 22 has not detected a diffraction point in step S505 (if there is no diffraction point) (step S505: N), it outputs information indicating that there is no diffraction point to the electric field intensity processing unit 24.

Fig. 10 is a flowchart showing an example of processing by the diffraction point detection unit 22, and Fig. 11 is a diagram explaining an example of processing by the diffraction point detection unit 22. First, the diffraction point detection unit 22 identifies the altitude of a transmission point included in the propagation path information from the altitude data. Then, the diffraction point detection unit 22 sets the transmission point (latitude, longitude, and altitude) as the judgment transmission point (latitude, longitude, and altitude) (step S1001).

The diffraction point detection unit 22 determines the angle θ at which the point is viewed from the determination transmission point for each point (altitude data point) in a certain section (e.g., 50 m) from the determination transmission point to the reception point along the path indicated by the propagation path information (step S1002). Here, the angle θ at which the point is viewed from the determination transmission point refers to the angle (vertical angle) between the point and a point on the ground perpendicularly downward from the determination transmission point, with the determination transmission point as the base point, as shown in FIG. 11(b).

The angle at which the reception point is viewed from the determination transmission point is set to θ1 (see FIG. 11(a)). Note that the latitude, longitude, and altitude of the point including the reception point are identified from the propagation path information and altitude data, so the angle θ at which the point is viewed from the determination transmission point can be obtained.

The diffraction point detection unit 22 determines whether or not there is a point that satisfies angle θ>angle θ1 (step S1003). Angle θ is the angle at which a point (excluding the reception point) is viewed from the determination transmission point, and angle θ1 is the angle at which the reception point is viewed from the determination transmission point.

If the diffraction point detection unit 22 determines in step S1003 that there is a point that satisfies angle θ>angle θ1 (step S1003: Y), it detects the point corresponding to the maximum angle θ as a diffraction point and stores it in a memory (not shown) (step S1004) (see the first diffraction point in Figure 11 (b)).

When there are multiple points that satisfy angle θ > angle θ1, the diffraction point detection unit 22 detects the point that corresponds to the maximum angle θ among them as a diffraction point. When there is only one point, the diffraction point detection unit 22 determines that the angle θ of the point is maximum and detects the point as a diffraction point.

The diffraction point detection unit 22 sets the diffraction point detected in step S1004 as the transmission point for determination (step S1005) and proceeds to step S1002. As a result, the diffraction point detected in step S1004 is set as the transmission point for determination, the angle θ of the point to the reception point is found, a new diffraction point is detected, and is stored in memory (see the second diffraction point in FIG. 11(c)).

In addition, in step S1004, if the detected diffraction point is adjacent to the previously detected diffraction point and the elevation difference is within 1 m, the diffraction point detection unit 22 excludes the detected diffraction point and performs the determination process of step S1003 again.

On the other hand, if the diffraction point detection unit 22 determines in step S1003 that there is no point where angle θ>angle θ1 (step S1003: N), it ends the process.

In this way, the diffraction point can be detected by searching for the point with the maximum angle θ between the judgment transmission point and the reception point, and then sequentially moving the judgment transmission point to the diffraction point and repeating this process until the reception point is reached.

Then, the diffraction point detection unit 22 reads all the diffraction points from the memory and outputs the latitude, longitude, and altitude data for each diffraction point to the shielding loss calculation unit 23. On the other hand, if no diffraction points are stored in the memory, the diffraction point detection unit 22 outputs information indicating that there are no diffraction points to the electric field intensity processing unit 24.

4 and 5, the shielding loss calculation unit 23 inputs data of latitude, longitude, and altitude for each diffraction point from the diffraction point detection unit 22, and calculates the shielding loss E _L caused by diffraction at all diffraction points (step S506). Then, the shielding loss calculation unit 23 outputs the shielding loss E _L to the electric field intensity processing unit 24. Note that if there is no diffraction point, the shielding loss calculation unit 23 does not perform any processing.

Fig. 12 is a flowchart showing an example of processing by the shielding loss calculation unit 23, and Fig. 13 is a diagram explaining an example of calculation of the shielding coefficient x (step S1201). Here, the losses due to shielding at all diffraction points detected on the propagation path are calculated, and the maximum value is assumed to be the shielding loss E _L and used in the calculation of the electric field intensity in the subsequent step S507.

The shielding loss calculation unit 23 calculates the shielding coefficient x for each diffraction point using the following formula, which assumes shielding by a knife edge, based on the latitude, longitude, and altitude data of the transmission point and the reception point, and the latitude, longitude, and altitude data of each diffraction point (step S1201).
[Equation 5]
x = √{(π/λ) × [(d ₁ + d ₂ )/(d ₁ × d ₂ )]} × a (5)
d ₁ indicates the distance between the point on the Earth's surface (P1 in FIG. 13) corresponding to (vertically below) the transmission point or the previous diffraction point, and the point on the Earth's surface (P2) corresponding to the diffraction point. d ₂ indicates the distance between the point on the Earth's surface (P2) corresponding to the diffraction point and the point on the Earth's surface (P3) corresponding to the reception point or the next diffraction point. a indicates the distance from the intersection point (P4) of the straight line from the elevation data point of the diffraction point to the point on the Earth's surface (P2) corresponding to the diffraction point, and the straight line from the elevation data point of the transmission point to the elevation data point of the reception point, to the elevation data point of the diffraction point. λ indicates the wavelength of the radio wave. Here, the virtual transmission point of a certain diffraction point is the diffraction point one step before.

For details of the process of calculating the shielding coefficient x, please refer to the following document.
[Non-Patent Document 4] "Revised Edition: Guidebook for Predicting Damage to Buildings," Reception Technology Center, NHK General Sales Bureau, Telecable Newspaper Company, May 1995, pp. 1-7

The shielding loss calculation unit 23 calculates the magnitude lf of the Fresnel integral value for each diffraction point using the shielding coefficient x for each diffraction point calculated in step S1201 and the Fresnel integral locus expressed by the following equation (step S1202).
[Equation 6]

For details on the process of calculating the magnitude lf of the Fresnel integral, please refer to the aforementioned non-patent document 4.

The shielding loss calculation unit 23 calculates the power loss tmp for each diffraction point by the following formula using the magnitude lf of the Fresnel integral value for each diffraction point calculated in step S1202 (step S1203).
[Equation 7]
tmp = (-20) x _log10 (2 x lf) ... (7)

The shielding loss calculation unit 23 obtains the maximum power loss tmp among all the power losses tmp for each diffraction point calculated in step S1203 as the shielding loss E _L (step S1204).

The shadowing loss calculation unit 23 may calculate the sum of all the power losses tmp for each diffraction point as the shadowing loss E _L. Here, the value of the power loss tmp may vary greatly depending on the reception height of the diffraction point. In this case, it is preferable to use the maximum power loss tmp as the shadowing loss E _L.

Returning to FIGS. 4 and 5, the electric field strength processing unit 24 inputs the electric field strength E _m from the Millington method calculation unit 21 , and also inputs the shadowing loss E _L from the shadowing loss calculation unit 23 or information on the absence of diffraction points from the diffraction point detection unit 22 .

When information of no diffraction points is input from the diffraction point detection unit 22, the field strength processing unit 24 sets the shielding loss _{E L} = 0. Then, the field strength processing unit 24 subtracts the shielding loss E _L (the shielding loss E _L input from the shielding loss calculation unit 23, or the shielding loss E _L = 0 when information of no diffraction points is input from the diffraction point detection unit 22) from the field strength E m (step S507). The field strength processing unit 24 sets the subtraction result as the field strength of the reception point (individual field strength) and outputs this to the field strength averaging unit 12.

As a result, the electric field strength calculation unit 11 obtains the electric field strength at the receiving point on the left-handed route, the electric field strength at the receiving point on the straight route, and the electric field strength at the receiving point on the right-handed route, taking into account the shielding loss due to diffraction.

As described above, according to the electric field strength calculation device 1 of the first embodiment, the propagation path calculation unit 10 calculates propagation path information for a straight line route from the transmitting point information and the receiving point information, calculates the first Fresnel zone, and calculates propagation path information for the clockwise route and the counterclockwise route.

The electric field strength calculation units 11-1, 11-2, and 11-3 calculate the electric field strength E _m at the reception point for each of the left-handed route, the straight route, and the right-handed route by the Millington method, and detect the diffraction points to calculate the shadowing loss E _L. Then, the electric field strength calculation units 11-1, 11-2, and 11-3 subtract the shadowing loss E _L from the electric field strength E _m to calculate the electric field strength at the reception point.

The electric field strength averaging unit 12 calculates the average value of the electric field strength at the reception point on the left-handed route, the electric field strength at the reception point on the straight route, and the electric field strength at the reception point on the right-handed route, and outputs this as the electric field strength at the reception point.

This allows the electric field strength at the receiving point to be obtained taking into account the first Fresnel zone and the shielding loss E _L due to diffraction. This solves the problem of the conventional Millington method in which the effects of diffraction due to mountains, etc. cannot be properly reflected in the electric field strength, and makes it possible to calculate with high accuracy the electric field strength at the receiving point receiving the medium wave.

Example 2
Next, a description will be given of a field strength calculation device according to a second embodiment. The second embodiment is an example in which a propagation path of a straight line route is used, and the field strength at a receiving point is calculated by taking into account shielding loss due to diffraction by mountains or the like, with respect to the field strength calculated by the Millington method.

Figure 14 is a block diagram showing an example of the configuration of a field strength calculation device of Example 2. This field strength calculation device 2 includes a propagation path calculation unit 30 and a field strength calculation unit 11.

The propagation path calculation unit 30 inputs the transmitting point information (latitude and longitude) and the receiving point information (latitude and longitude), and calculates the propagation path information of the straight line route between the transmitting and receiving points (latitude and longitude for each specified distance between the transmitting and receiving points) based on this information. The propagation path calculation unit 30 then outputs the propagation path information of the straight line route to the electric field intensity calculation unit 11.

The propagation path calculation unit 30 in the second embodiment differs from the propagation path calculation unit 10 in the first embodiment in that it does not calculate propagation path information for the clockwise and counterclockwise routes based on the first Fresnel zone.

The electric field strength calculation unit 11 corresponds to the electric field strength calculation unit 11-2 shown in Fig. 1 and the electric field strength calculation unit 11 shown in Fig. 4. Specifically, the electric field strength calculation unit 11 inputs propagation path information of a straight route from the propagation path calculation unit 30, obtains a terrain classification for each predetermined distance of the propagation path of the straight route, and calculates the electric field strength E _m of the reception point by the Millington method using the terrain classification.

The electric field strength calculation unit 11 detects diffraction points based on the propagation path information and altitude data of the straight route, calculates the shadowing loss E _L of the diffraction points, and obtains the electric field strength at the reception point by subtracting the shadowing loss E _L from the electric field strength E _m .

As described above, the electric field strength calculation device 2 of the second embodiment can obtain the electric field strength at the receiving point of the straight route taking into account the shielding loss E _L due to diffraction. Therefore, it is possible to solve the problem of the conventional Millington method in which the influence of diffraction due to mountains, etc. cannot be properly reflected in the electric field strength, and it is possible to calculate the electric field strength at the receiving point receiving the medium wave with high accuracy.

Example 3
Next, a description will be given of a field intensity calculation device according to embodiment 3. Embodiment 3 is an example in which the field intensity at a receiving point is calculated by the Millington method using a straight line route propagation path and a propagation path taking into account a Fresnel zone.

FIG. 15 is a block diagram showing an example of the configuration of a field strength calculation device according to the third embodiment. This field strength calculation device 3 includes a propagation path calculation unit 10, field strength calculation units 31-1, 31-2, and 31-3, and a field strength averaging unit 12.

Comparing the electric field strength calculation device 1 of Example 1 shown in FIG. 1 with the electric field strength calculation device 3 of Example 3 shown in FIG. 15, both electric field strength calculation devices 1 and 3 have in common the fact that they include a propagation path calculation unit 10 and an electric field strength averaging unit 12. On the other hand, the electric field strength calculation device 3 differs from the electric field strength calculation device 1 in that it includes electric field strength calculation units 31-1, 31-2, and 31-3 that are different from the electric field strength calculation units 11-1, 11-2, and 11-3 included in the electric field strength calculation device 1. In FIG. 15, parts that are common to FIG. 1 are given the same reference numerals as in FIG. 1, and detailed descriptions thereof will be omitted.

The electric field strength calculation units 31-1, 31-2, and 31-3 respectively input the propagation path information of the counterclockwise route, the propagation path information of the straight route, and the propagation path information of the clockwise route from the propagation path calculation unit 10.

The electric field strength calculation units 31-1, 31-2, and 31-3 calculate the electric field strength at the reception point for each of the left-handed route, the straight route, and the right-handed route using the Millington method.

The electric field strength calculation unit 31-1 outputs the electric field strength of the reception points on the counterclockwise route to the electric field strength averaging unit 12, and the electric field strength calculation unit 31-2 outputs the electric field strength of the reception points on the straight route to the electric field strength averaging unit 12. The electric field strength calculation unit 31-3 outputs the electric field strength of the reception points on the clockwise route to the electric field strength averaging unit 12. Details of the electric field strength calculation units 31-1, 31-2, and 31-3 will be described later.

Unlike the electric field strength calculation units 11-1, 11-2, and 11-3 of the embodiment 1, the electric field strength calculation units 31-1, 31-2, and 31-3 of the embodiment 3 do not detect diffraction points to calculate the shadowing loss E _L. That is, the electric field strength calculation units 31-1, 31-2, and 31-3 calculate the electric field strength by the Millington method, but do not calculate the electric field strength taking into account the shadowing loss E _L due to diffraction.

The electric field strength calculation units 31-1, 31-2, and 31-3 (hereinafter collectively referred to as the electric field strength calculation unit 31) will be described in detail below. FIG. 16 is a block diagram showing an example of the configuration of the electric field strength calculation unit 31 in the third embodiment. This electric field strength calculation unit 31 includes a propagation path topography classification processing unit 20 and a Millington method calculation unit 21.

The electric field strength calculation unit 31 inputs propagation path information (latitude and longitude for each specified distance between the transmitting and receiving points) of the corresponding route (either a left-handed route, a straight route, or a right-handed route) from the propagation path calculation unit 10.

The propagation path terrain classification processing unit 20 performs the same processing as the propagation path terrain classification processing unit 20 shown in FIG. 4. Specifically, the propagation path terrain classification processing unit 20 inputs the propagation path information and preset terrain classification data, and uses the terrain classification data to determine the terrain classification for each predetermined distance along the propagation path indicated by the propagation path information from the transmission point to the reception point. The propagation path terrain classification processing unit 20 then outputs the terrain classification for each predetermined distance of the propagation path to the Millington method calculation unit 21.

The Millington method calculation unit 21 performs the same processing as the Millington method calculation unit 21 shown in Fig. 4. Specifically, the Millington method calculation unit 21 inputs the terrain classification for each predetermined distance of the propagation path from the propagation path terrain classification processing unit 20, and also inputs data of the electric field strength curve for each preset terrain classification.

The Millington method calculation unit 21 uses the electric field strength curve for each earth conductivity according to the terrain classification to determine the electric field strength at points at each predetermined distance along the propagation path from the transmitting point to the receiving point, then corrects for discontinuous points, and determines the electric field strength at the receiving point (transmitting point → receiving point) _Ea . Similarly, the Millington method calculation unit 21 determines the electric field strength at points at each predetermined distance along the propagation path from the receiving point to the transmitting point, then corrects for discontinuous points, and determines the electric field strength at the transmitting point (receiving point → transmitting point) _Eb .

The Millington method calculation unit 21 calculates the electric field strength E _m at the reception point from the electric field strength (transmission point → reception point) E _a and the electric field strength (reception point → transmission point) E _b using equation (4) above, and outputs this as the electric field strength at the reception point.

As described above, the electric field strength calculation device 3 of the third embodiment can calculate the electric field strength at the receiving point by the Millington method using a straight line route propagation path and a propagation path that takes into account the Fresnel zone. Therefore, the difference between the calculated value and the actual measured value for the electric field strength of the medium wave can be reduced, and the electric field strength at the receiving point receiving the medium wave can be calculated with high accuracy.

The present invention has been described above using Examples 1 to 3, but the present invention is not limited to the above Examples 1 to 3, and various modifications are possible without departing from the technical concept thereof.

In the above-mentioned first to third embodiments, the propagation path topography classification processing unit 20 provided in the electric field strength calculation unit 11 uses, for example, land classification mesh data (1 km mesh) from the National Land Numerical Information as the pre-set topography classification data. In contrast, the propagation path topography classification processing unit 20 may use land classification mesh data of a size other than the 1 km mesh.

In addition, in the above-mentioned Examples 1 to 3, the diffraction point detection unit 22 provided in the electric field intensity calculation unit 11 uses, as the preset altitude data, data indicating the altitude of each point based on, for example, a 50 m mesh. In contrast, the diffraction point detection unit 22 may use data indicating the altitude of each point of a size other than the 50 m mesh.

In addition, in the first and third embodiments, the propagation path calculation unit 10 calculates the propagation path information of the straight route, calculates the first Fresnel zone, sets the route that passes through the right end of the first Fresnel zone as a clockwise route, calculates the propagation path information of the clockwise route, sets the route that passes through the left end as a counterclockwise route, and calculates the propagation path information of the counterclockwise route. In contrast, the propagation path calculation unit 10 may calculate the propagation path information of the straight route, calculate the first Fresnel zone, set either the right end or the left end of the first Fresnel zone as an end route, and calculate the propagation path information of the end route.

In this case, since the propagation path calculation unit 10 calculates the propagation path information of the straight route and the end route, the field strength calculation device 1 may include two corresponding field strength calculation units 11. The two field strength calculation units 11 calculate the field strength E _m of the reception point for each of the straight route and the end route by the Millington method, detect the diffraction point to calculate the shadowing loss E _L , and subtract the shadowing loss E _L from the field strength E _m to calculate the field strength of the reception point. Then, the field strength averaging unit 12 calculates the average value of the field strength of the reception point on the straight route and the field strength of the reception point on the end route, and outputs this as the field strength of the reception point.

In addition, a normal computer can be used as the hardware configuration of the electric field strength calculation devices 1, 2, and 3 according to the first, second, and third embodiments of the present invention. The electric field strength calculation devices 1, 2, and 3 are configured by a computer equipped with a CPU, a volatile storage medium such as a RAM, a non-volatile storage medium such as a ROM, and an interface, etc.

The functions of the propagation path calculation unit 10, the field strength calculation units 11-1, 11-2, 11-3 and the field strength averaging unit 12 provided in the field strength calculation device 1 are each realized by having the CPU execute a program that describes these functions.

Furthermore, the functions of the propagation path calculation unit 30 and the field strength calculation unit 11 provided in the field strength calculation device 2 are each realized by having the CPU execute a program that describes these functions.

Furthermore, the functions of the propagation path calculation unit 10, the field strength calculation units 31-1, 31-2, 31-3, and the field strength averaging unit 12 provided in the field strength calculation device 3 are each realized by having the CPU execute a program that describes these functions.

These programs are stored in the storage medium and are read and executed by the CPU. In addition, these programs can be distributed by storing them on storage media such as magnetic disks (floppy disks, hard disks, etc.), optical disks (CD-ROMs, DVDs, etc.), and semiconductor memories, and can also be transmitted and received via a network.

1, 2, 3 Field strength calculation device 10, 30 Propagation path calculation unit 11, 31 Field strength calculation unit 12 Field strength averaging unit 20 Propagation path topography classification processing unit 21 Millington method calculation unit 22 Diffraction point detection unit 23 Shadowing loss calculation unit 24 Field strength processing unit E _m Field strength E _L Shadowing loss θ, θ1 Angle x Shadowing coefficient lf Magnitude of Fresnel integral value tmp Loss power

Claims (5)

In the electric field strength calculation device for calculating the electric field strength at a receiving point receiving a medium wave,
a propagation path calculation unit that calculates propagation path information indicating the latitude and longitude of a straight line route from the transmission point to the reception point, based on transmission point information indicating the latitude and longitude of a preset transmission point and reception point information indicating the longitude and latitude of the reception point, calculates a first Fresnel zone when the transmission point is viewed from the reception point, based on the transmission point information, the reception point information, and the medium wave frequency, sets either the right end or the left end of the first Fresnel zone as an edge route with respect to the earth's surface, and calculates the propagation path information of the edge route;
a field strength calculation unit that calculates a terrain classification for each of the straight line routes and the edge routes at predetermined distances along a route indicated by the corresponding propagation path information by using preset terrain classification data, and calculates a field strength E _m of the reception point according to the terrain classification by a predetermined field strength calculation method of the Millington method;
a field strength averaging unit that calculates an average value of the field strength E _m of the straight line route and the field strength E _m of the end route calculated by the field strength calculation unit, and outputs the average value as the field strength of the reception point;
A field strength calculation device comprising: In a field strength calculation device for calculating a field strength at a receiving point receiving a medium wave,
a propagation path calculation unit that calculates propagation path information indicating the latitude and longitude of a straight line route from the transmission point to the reception point, based on transmission point information indicating the latitude and longitude of a preset transmission point, and reception point information indicating the longitude and latitude of the reception point, calculates a first Fresnel zone when the transmission point is viewed from the reception point, based on the transmission point information, the reception point information, and the medium wave frequency, sets the right end of the first Fresnel zone as a clockwise route with respect to the Earth's surface, calculates the propagation path information for the clockwise route, and sets the left end of the first Fresnel zone as a counterclockwise route with respect to the Earth's surface, and calculates the propagation path information for the counterclockwise route;
a field strength calculation unit that calculates a terrain classification for each of the straight line route, the clockwise route, and the counterclockwise route, at every predetermined distance along a route indicated by the corresponding propagation path information by using preset terrain classification data, and calculates a field strength E _m of the reception point according to the terrain classification by a predetermined field strength calculation method of the Millington method;
a field strength averaging unit that calculates an average value of the field strength E _m of the straight line route, the field strength E _m of the clockwise route, and the field strength E _m of the counterclockwise route, which are calculated by the field strength calculation unit, and outputs the average value as the field strength of the reception point;
A field strength calculation device comprising: 3. The electric field strength calculation device according to claim 1,
the electric field strength calculation unit includes a propagation path topography classification processing unit, a Millington method calculation unit, a diffraction point detection unit, a shielding loss calculation unit, and an electric field strength processing unit, corresponding to each of the plurality of routes in the propagation path information calculated by the propagation path calculation unit;
The propagation path topography classification processing unit includes:
determining the terrain classification for each of the predetermined distances using the terrain classification data along the route indicated by the propagation path information;
The Millington method calculation unit is
Calculating the electric field strength E _m according to the terrain classification obtained by the propagation path terrain classification processing unit by the electric field strength calculation method of the Millington method;
The diffraction point detection unit is
generating topographical cross-sectional data for each predetermined distance between the transmitting point and the receiving point based on the propagation path information and preset altitude data, and detecting all diffraction points between the transmitting point and the receiving point based on the topographical cross-sectional data;
The shielding loss calculation unit
Calculating a power loss tmp for each of all the diffraction points detected by the diffraction point detection unit, and determining the largest power loss tmp among the power loss tmp of all the diffraction points as a shielding loss E _L , or determining the sum of the power loss tmp of all the diffraction points as the shielding loss E _L ;
The electric field intensity processing unit includes:
subtracting the shadowing loss E _L calculated by the shadowing loss calculation unit from the electric field strength E _m calculated by the Millington method calculation unit to calculate individual electric field strengths of the reception points;
The electric field intensity averaging unit is
a field strength calculation device which calculates an average value of the individual field strengths calculated by the field strength processing units corresponding to each of a plurality of the routes, and outputs the average value as the field strength of the reception point. In the electric field strength calculation device for calculating the electric field strength at a receiving point receiving a medium wave,
a propagation path calculation unit that calculates propagation path information indicating the latitude and longitude of a straight line route from a transmission point to a reception point, based on transmission point information indicating the latitude and longitude of a preset transmission point and reception point information indicating the longitude and latitude of the reception point;
A field strength calculation unit that calculates the field strength of the reception point,
The electric field strength calculation unit
a propagation path terrain classification processing unit that calculates a terrain classification for each predetermined distance along a route indicated by the propagation path information of the straight line route calculated by the propagation path calculation unit, using preset terrain classification data;
a Millington method calculation unit that calculates the electric field strength E _m of the reception point according to the terrain classification obtained by the propagation path terrain classification processing unit by a predetermined Millington method electric field strength calculation method;
a diffraction point detection unit that generates topographical cross-sectional data for each predetermined distance between the transmission point and the reception point based on the propagation path information of the straight line route and preset altitude data, and detects all diffraction points existing between the transmission point and the reception point based on the topographical cross-sectional data;
a shielding loss calculation unit that calculates a power loss tmp for each of all of the diffraction points detected by the diffraction point detection unit, and determines a sum of the power loss tmp of all of the diffraction points as a shielding loss E _L , or determines a maximum power loss tmp among the power loss tmp of all the diffraction points as the shielding loss E _L ;
a field strength processing unit that subtracts the shadowing loss E _L calculated by the shadowing loss calculation unit from the field strength E _m calculated by the Millington method calculation unit to calculate the field strength of the reception point;
A field strength calculation device comprising: A program for causing a computer to function as the electric field strength calculation device according to any one of claims 1 to 4.

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