JP2016208303A - Stacked antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for achieving stable reception by a stacked antenna irrespective of variations in the reception height pattern.SOLUTION: An antenna section (2) includes a pair of receiving antennas (21, 22) installed vertically. A combining section (3) includes a combiner (33) for synthesizing the outputs of the receiving antennas and a pair of feeder lines (31, 32) connecting each of the receiving antennas and the synthesizer. A composite wave is obtained by combining a direct wave arriving at the antenna section from the transmission source of the reception target radio wave and the ground reflected wave. The phase difference of the composite wave received by each of the receiving antennas is referred to as a vertical separation phase. The phase difference of the composite waves due to the line length difference between the pair of feeder lines is referred to as a feeding phase. The vertical separation distance of the pair of receiving antennas and the line length of the pair of feeder lines are set so that the sum of the vertical separation phase and the feeding phase generated at the predetermined reference frequency becomes 180°.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for suppressing the influence of a reception height pattern in a reception antenna that receives radio waves.

  The reception point of the TV joint reception facility and the gap filler (hereinafter referred to as GF) used for countermeasures for the difficulty in viewing digital terrestrial broadcasting is basically installed in a place where the radio wave visibility from the transmission point is good. At such a reception point, the reception level changes due to the influence of the reception height pattern (hereinafter referred to as height pattern), and reception may be poor depending on the reception channel.

  As a technique for stabilizing the reception level in such a situation, a stack antenna that combines (stacks) reception antenna outputs using two or more reception antennas is known (see Patent Document 1).

JP 2010-68174 A

  By the way, the height pattern is caused by interference between a direct wave that reaches directly from the transmission point to the reception point and a ground reflected wave that reflects and reaches the ground such as the ground or the sea surface. For this reason, if the reflecting surface that reflects radio waves due to snowfall, tides, etc., and the path of the ground reflected wave changes, the height pattern also changes accordingly, so how to synthesize and the height of the antenna There is a problem that it is difficult to stabilize the reception level.

  In other words, even if the antenna is adjusted to receive a signal at a high reception level in consideration of the height pattern, if the ground reflection surface changes, the height pattern shifts in the vertical direction by the change, and the height pattern The signal may be received near the null point.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique for realizing stable reception by a stack antenna regardless of fluctuations in the reception height pattern.

  The stack antenna of the present invention includes an antenna unit and a combining unit. The antenna unit is composed of a pair of receiving antennas installed at the top and bottom. The combining unit includes a combiner that combines the outputs of the receiving antennas and a pair of feed lines that connect each of the pair of receiving antennas to the combiner. However, a radio wave within a preset frequency range is a reception target radio wave, a combination of a direct wave reaching the antenna unit from the transmission source of the reception target radio wave and a ground reflected wave is a combined wave, and the antenna unit is At the reference frequency set within the frequency range, the phase difference between the combined waves received by each of the constituting receiving antennas is the vertical separation phase, and the phase difference of the combined wave due to the line length difference between the pair of feed lines is the feed phase. The vertical separation distance that is the arrangement interval of the pair of receiving antennas and the line length of the pair of feeding lines are set so that the total of the generated vertical separation phase and the feeding phase is 180 °.

  According to such a configuration, even if a periodic null point exists in the height pattern of the received electric field strength at the installation point of the stack antenna of the present invention, the received electric field strength obtained from the stack antenna is the height pattern null. The influence of points (that is, height dependency) is suppressed. As a result, almost uniform received electric field strength can be obtained regardless of the installation height of the antenna section, so even in an environment where the reflective surface of the ground reflection changes, it is stable without requiring adjustment of the stack antenna. The received state can be realized.

  In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is limited is not.

It is a block diagram which shows the structure of a stack antenna. It is explanatory drawing which shows the radio wave propagation model used for calculation of a theoretical value. (A) The characteristic of a ground reflection coefficient, (b) is a graph which illustrates the characteristic of the phase shift of a ground reflection coefficient. It is a graph which shows the example of calculation of a height pattern, (a) is a case of horizontal polarization, (b) is a case of vertical polarization. It is explanatory drawing which shows the relationship between a height pattern and an electric field vector, (a) is a height pattern, (b) is an electric field vector of a direct wave, (c) is an electric field vector of a ground reflected wave, (d) is an electric field of a synthetic wave. Is a vector. It is explanatory drawing which shows rotation of the electric field vector on a complex plane, (a) shows rotation of an electric field vector and a synthetic | combination vector, (b) shows the phase change of the synthetic | combination vector. It is explanatory drawing regarding the synthetic | combination output which synthesize | combined the output from an upper stage antenna and a lower stage antenna, and both outputs, (a) is the electric field strength of a single base antenna (upper stage and lower stage antenna) output, (b) is the phase of a single base antenna output. (C) is the electric field vector of the single-base antenna output, (d) is the electric field vector of the combined output obtained by in-phase combining the outputs of the upper and lower antennas, and (e) is the combined output obtained by phase-shifting the outputs of the upper and lower antennas. Of the electric field vector. It is a graph which shows the result of having calculated | required the synthetic | combination output at the time of making a feeding phase constant (90 degrees) and changing a vertical separation phase by simulation. It is a graph which shows the result of having calculated | required the synthetic | combination output at the time of making a perpendicular | vertical separation phase constant (90 degrees) and changing a feeding phase by simulation. It is a graph which shows the result of having calculated | required the synthetic | combination output at the time of making the sum total of a perpendicular | vertical separation phase and a feeding phase constant (180 degrees), and changing the ratio of both by simulation. It is a graph which shows the result of having calculated | required the relationship between the vertical separation phase and the amplitude of a synthetic | combination output at the time of making the sum total of a vertical separation phase and a feeding phase constant (180 degrees). It is the graph which calculated | required the synthetic | combination output in case there exists a level difference in an upper and lower stage antenna by simulation, (1)-(3) changes only a level difference, (4)-(6) shows a vertical separation phase and This is a case where the total feeding phase is not 180 °.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
[Constitution]
A stack antenna 1 shown in FIG. 1 is configured as a reception point of a TV joint reception facility or gap filler (GF) used for measures for difficulty in seeing digital terrestrial broadcasting, and includes an antenna unit 2 and a combining unit 3. With.

  The antenna unit 2 includes a pair of receiving antennas 21 and 22 each receiving a reception target radio wave, and is arranged with a space in the vertical direction. Hereinafter, the upper receiving antenna is referred to as the upper antenna 21, the lower receiving antenna is referred to as the lower antenna 22, and the distance between them is referred to as a vertical separation δ. The receiving antennas 21 and 22 are configured to be able to receive a part or all of signals within a predetermined reception target frequency range (here, a frequency band used for terrestrial digital broadcasting). Hereinafter, the center frequency of the frequency range is referred to as a reference frequency, and the wavelength of the reference frequency is referred to as a reference wavelength λ.

The synthesizer 3 includes a pair of feeder lines 31 and 32 and a synthesizer 33. Line length of the feed line 31 connecting the upper antenna 21 and combiner 33 is set to L _1, the line length of the feed line 32 which connects the lower antenna 22 and combiner 33 is set to L _2. The synthesizer 33 adds and synthesizes the outputs of the receiving antennas 21 and 22 supplied via the feeder lines 31 and 32 to generate a reception signal.

Here, it is assumed that the receiving antennas 21 and 22 each receive a combined wave of a direct wave that directly arrives from a transmission point of a reception target radio wave and a ground reflected wave that arrives after being reflected by the ground or the sea surface. Also, the phase difference between the upper combined wave received by the upper antenna 21 and the lower combined wave received by the lower antenna 22 is referred to as a vertical separation phase θ _δ, and depends on the line length difference (L ₁ −L ₂ ) between the feeder lines 31 and 32. , I called a phase difference generated between the upper composite wave and the lower combined wave and the feed phase theta _L.

Then, assuming that the wavelength of the reception target radio wave (and thus the combined wave) is the reference wavelength, the vertical separation distance δ of the receiving antennas 21 and 22 is θ _δ = 90 ° (= π / 2 [rad]). The line lengths L ₁ and L ₂ of the feeder lines 31 and 32 are set so that the feeding phase is θ _L = 90 ° (= π / 2 [rad]). However, the wavelength shortening rate in the feeder lines 31 and 32 is taken into account in setting the line lengths L ₁ and L ₂ .

Specifically, the line lengths L ₁ and L ₂ of the feeder lines 31 and 32 may be set so as to satisfy the expression (1), and the vertical separation distance δ may be set so as to satisfy the expression (2). For d and h ₁ in the equation, refer to the radio wave propagation model described later.

[Radio wave propagation model]
The radio wave propagation model used for calculating the theoretical value described below will be described.

2, the installation position of the transmission source (transmission antenna) of the reception target radio wave is the transmission point, the installation position of the upper antenna 21 is the reception point # 1, and the installation position of the lower antenna 22 is the reception point # 2. The height of the point (distance from the ground) is h ₁ , the horizontal distance from the transmission point to the reception points # 1 and # 2 is d, the height of the reception point # 1 is h ₂ , and the height of the reception point # 2 is h ₂ ′, and the vertical separation distance between the reception point # 1 and the reception point # 2 is δ.

[Height pattern]
First, a height pattern which is a premise for understanding the present invention will be described.
The height pattern represents a characteristic in which the received electric field strength changes periodically according to the height of the antenna, and is observed in a place where radio wave visibility is good. This phenomenon occurs when the direct wave and the ground reflected wave interfere and are combined, and is particularly noticeable in horizontal polarization.

Here, the distance from the transmission point to the ground point immediately below the reception point is r ₀ , the propagation distance of the direct wave at the reception point # 1 is r ₁ , and the propagation distance of the ground reflected wave is r ₂ . Distance _{r 0} ground reflected wave propagating path length difference [Delta] r ₂ of the propagation path length difference [Delta] r ₁ and the distance _{r 0} of the direct wave as a reference relative to the _{can, d >> h 1, h 2} , 2h 1 >> h ₂ is approximated by equations (3) and (4).

That is, when the distance r ₀ is considered as a reference, the direct wave reaches the reception point # 1 earlier by the propagation path length difference Δr ₁ , and the ground reflected wave reaches the reception point # 1 with a delay of the propagation path length difference Δr _2. Then, a synthesized wave obtained by synthesizing these is received at the reception point # 1. The received electric field strength (hereinafter also simply referred to as a synthesized wave) _Er of this synthesized wave is expressed by the equation (5). Here, θ is a phase difference caused by the propagation path length differences Δr ₁ and Δr ₂ , and is expressed by equation (6). Further, E ₀ is the free space electric field strength and is represented by the equation (7). Further, E ₁ is the received electric field intensity of the direct wave (hereinafter also referred to simply as direct wave), E ₂ is the received electric field intensity of the ground reflected wave (hereinafter also referred to simply as ground reflected wave), and R is the reflection coefficient of the ground reflected wave. (Hereinafter referred to as the ground reflection coefficient), β is a phase constant (= 2π / λ), and P is an effective radiation power at the transmission point.

As shown in FIG. 3, the reflection coefficient R of the ground reflected wave varies depending on the transmission polarization, the medium of the reflecting surface, and the incident angle (grounding angle) to the ground, and the amplitude of the reflected wave depends on the reflection coefficient R. Although the phase changes, the ground reflection coefficient of the horizontally polarized wave is usually treated as R = -1. Accordingly, by substituting R = −1 into the equation (5), the equation (8) is obtained. When the equation (8) is modified, the equation (9) is obtained. Note that the graph of FIG. 3 is obtained using a Fresnel reflection formula with a frequency of 600 MHz.

Height pattern is a pattern of the received electric field intensity E _r obtained when changing the height h ₂ of the reception point. Therefore, it can be seen from equation (9) that the height pattern is determined by the horizontal distance d between the transmission and reception points, the wavelength λ of the used radio wave, and the height h ₁ of the transmission point. An example of the height pattern of the horizontal polarization obtained according to the equation (9) is shown in FIG. For reference, in the case of vertical polarization, since it cannot be regarded as R = −1, the height pattern can be obtained by using the formula (5) by the Fresnel reflection formula. In this case, since the received electric field strengths of the direct wave and the ground reflected wave are different and do not completely cancel each other, as shown in FIG. 4B, reception is relatively large even at the null point as compared with the horizontally polarized wave. Electric field strength is obtained.

Here, the relationship between the electric field vectors of the direct wave E ₁ , the ground reflected wave E ₂ , and the combined wave _Er and the height pattern will be described with reference to FIGS. 5 and 6. The height pattern appears when the interference state between the direct wave E ₁ and the ground reflected wave E ₂ changes depending on the height of the reception point. Specifically, as can be seen from equation (8), the electric field vector of the direct wave E _{1 and} the electric field vector of the ground reflected wave E ₂ are rotated in the opposite direction, thereby canceling or strengthening (see FIG. 5 (b) (c), see FIG. 6 (a)). Then, the electric field vector of the synthesized wave _Er obtained by synthesizing the electric field vectors of the direct wave E ₁ and the ground reflected wave E ₂ alternately repeats ± 90 ° phases (FIG. 5 (d), (Refer FIG.6 (b)). Further, the amplitude value of the received electric field strength _Er sine-oscillates as shown in the equation (9) and changes between −2E _{0 to} 2E ₀ . At this time, a period in which a peak (maximum point) or valley (minimum point) of the absolute value of the amplitude value appears is called a height pitch. When the height of the reception point moves by a height pitch, the phase of the reception wave (synthetic wave) induced at the reception point is shifted by a half period (π [rad] = 180 °). In the following, the height of the reception point is represented by the phase θ of the reception wave so that general handling can be performed regardless of the frequency of the reception wave.

Then, for example, theta = height h _{2 =} h a reception point corresponding to 2 _[pi, the height of the reception points corresponding to theta = [pi When h _{2 =} h _b, these relations (6) The heights h _a and h _b can be obtained by substituting into and transformed, and the height pitch PT is expressed by equation (10) using the obtained heights h _a and h _b .

That is, in order to set the vertical separation phase to θ _δ = 90 °, considering that the vertical separation distance needs to be δ = PT / 2, Equation (2) is derived from Equation (10).

[Receiving electric field strength depending on the height of the receiving antenna]
Assuming that the installation height of the upper antenna 21 is h ₂ and the installation height of the lower antenna 22 is h ₂ ′, both have the relationship shown in the equation (11).

The phase of the combined wave (phase difference between the direct wave E ₁ and the ground reflected wave E ₂ ) θ ₁ and θ ₂ induced in each of the upper antenna 21 and the lower antenna 22 is expressed by equations (12) and (13).

Therefore, the received electric field strengths E _r1 and E _r2 of the combined wave induced in each of the upper antenna 21 and the lower antenna 22 are expressed by the equations (14) and (15).

Here, when the vertical separation distance δ is half of the height pitch PT shown in the equation (10) (δ = PT / 2) and this is substituted into the equation (13) and rearranged, the phase of the composite wave of the lower antenna 22 is calculated. θ ₂ is expressed by equation (16). In this case, the received electric field strength E _r2 of the combined wave of the lower antenna 22 is expressed by equation (17).

[Combination of upper and lower antenna outputs]
Next, the reception field intensity when the output E _r2 output E _r1 and the lower antenna 22 of the upper antenna 21 phase combining E _ra, the phase of the output E _r1 of the upper antenna 21 π / 2 (= 90 ° ) advanced reception electric field strength in the case where the phase synthesized (top fast synthesis) E _rb, phases π / 2 (= 90 °) delayed in phase synthetic output E _r1 of the upper antenna 21 (the upper slow synthesis) and if the reception field strength E _rc, the phase of the output E _r2 of the lower antenna 22 π / 2 (= 90 ° ) advanced reception field strength E _rd in the case of phase synthesis (lower fast synthesis), the output E of the lower antenna 22 The received electric field intensity E _re when the phase of _r2 is delayed by π / 2 (= 90 °) and phase-shifted (lower-stage delayed synthesis) is expressed by equations (18) to (22). Note that to advance the phase by π / 2 mathematically corresponds to multiplication by + j, and physically to make the length of the feeder line shorter by λ / 4 than the other. Further, delaying the phase by π / 2 mathematically corresponds to multiplying by −j, and physically making the line length of the feeder line λ / 4 longer than the other.

When ignoring the insertion loss of the combiner, in the received electric field strengths E _{ra to} E _re added and combined by the combiner 33, the peak value of E _ra is the height pattern of the single antenna (FIG. 5 (a ) See 3). The values of E _{rb to} E _re are the same as at the peak of the height pattern of the single antenna (see FIG. 5A).

As shown in the equation (18), the received electric field strength E _ra in the case of the in-phase synthesis has an amplitude that vibrates due to the presence of the sin term, resulting in a null point. However, the null point occurs at a position shifted by 45 ° (= π / 4 [rad]) as compared with the height pattern of the single-base antenna. On the other hand, the reception field strength E _rb to E _re in the case of phase synthesis (19) as shown in - (22), since no term for varying the amplitude, depending on the height of the receiving point h ₂ A constant amplitude can be obtained.

FIG. 7 visually shows the above-described content using electric field vectors. That is, the electric field vector expressing the outputs E _r1 and E _r2 of the single base antenna (upper antenna 21 and lower antenna 22) on the complex plane exists in the direction of ± 90 °, and the vertical separation phase of both is 90 ° shifted. (See FIGS. 7B and 7C). The electric field vector of the combined output E _ra obtained by combining the outputs E _r1 and E _r2 in phase is obtained by simply synthesizing the electric field vector of the upper antenna and the electric field vector of the lower antenna on the same horizontal line in FIG. )reference). Electric field vector of the output E _r1, E _r2 and phase synthesized composite output E _rb to E _re is one of the electric field vector of the output E _r1, E _r2, (multiplied by + j) + 90 ° rotation or -90 ° rotation (Multiply by -j) and combine with the other electric field vector (see FIG. 7 (e)). In the in-phase synthesis, the amplitude (the magnitude of the electric field vector) changes according to the height of the reception point. In the phase-shifting synthesis, the phase (the direction of the electric field vector) rotates according to the height of the reception point, but the amplitude It can be seen that (the magnitude of the electric field vector) is constant.

  In FIG. 7, the vertical axis of the graph indicates the height of the upper antenna 21. Further, the received electric field intensity and phase of the lower antenna 22 are shifted and displayed at the height of the upper antenna 21 (the same applies to FIGS. 8 to 10 and 12 below).

[effect]
As described above, in the stack antenna 1, the vertical separation distance δ is set so that the vertical separation phase becomes θ _δ = 90 °, and the line length L ₁ , so that the feeding phase becomes θ _L = 90 °. It has set the L _2. As a result, even if a periodic null point exists in the height pattern of the received electric field strength at the installation point of the stack antenna 1, the electric field strength of the received signal output from the combiner 33 is affected by the height pattern null point. Is suppressed, that is, the reception point height dependency is suppressed. As a result, a substantially uniform received electric field strength can be obtained regardless of the installation height of the antenna unit 2, so that adjustment of the stack antenna 1 is required even in an environment where the height of the ground reflecting surface changes. And a stable reception state can be realized.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention can take a various form, without being limited to the said embodiment.

(1) In the above embodiment, the vertical separation distance δ and the line lengths L ₁ and L ₂ are set so that the vertical separation phase is θ _δ = 90 ° and the feeding phase is θ _L = 90 °. However, the present invention is not limited to this, and both phases may be set in a range of 30 ° to 150 ° and 180 ° in total. The basis for this will be described below.

When the feeding phase is fixed at θ _L = 90 ° and the vertical separation phase θ _δ is changed, as shown in FIG. 8, when the vertical separation phase is θ _δ = 90 °, the received electric field strength of the combined output is received. The fluctuation width (PP value) of the received electric field intensity of the combined output becomes larger (the ripple of the height pattern becomes deeper) as the vertical separation phase θ _δ becomes farther from 90 °. When the vertical separation phase is θ _δ = 180 °, the output of the upper antenna 21 and the output of the lower antenna 22 are in opposite phases, and the effect of suppressing the influence of the null point cannot be obtained. Note that the received electric field strength of the combined output in the figure is represented by a relative level based on the free space electric field strength E ₀ (hereinafter, the same applies to FIGS. 9 to 12).

When the vertical separation phase is fixed at θ _δ = 90 ° and the feeding phase θ _L is changed, as shown in FIG. 9, when the feeding phase is θ _L = 90 °, the received electric field strength of the combined output is the receiving point. As the power feeding phase θ _L is further away from 90 °, the fluctuation range of the received electric field strength of the combined output becomes larger (the ripple of the height pattern becomes deeper). Then, when the feeding phase theta _L is 180 °, it can not be obtained the effect of suppressing the influence of the null point.

As can be seen from FIGS. 8 and 9, the effects of the deviation of the vertical separation phase θ _δ and the feeding phase θ _L from 90 ° on the fluctuation range of the received electric field strength of the combined output are the same.
When the sum of the vertical separation phase θ _δ and the feeding phase θ _L is 180 ° and only the ratio of both phases is changed, the received electric field strength of the combined output does not depend on the height at any ratio as shown in FIG. It becomes constant. However, when the vertical separation phase θ _δ and the feeding phase θ _L are both 90 °, the received electric field strength of the combined output becomes maximum, and the received electric field strength of the combined output decreases as the difference between the two phases increases. As shown in FIG. 11, the received electric field strength of the combined output is greater than or equal to the free space electric field strength E ₀ (relative combined level 0 dB) when the vertical separation phase θ _δ is in the range of 30 ° to 150 °.

Thus, if the vertical separation phase θ _δ and the feeding phase θ _L are both set to a total of 180 ° in the range of 30 ° to 150 °, the influence of the null point of the height pattern is sufficiently suppressed. be able to.

  However, if there is a level difference between the output of the upper antenna 21 and the output of the lower antenna 22, as shown in FIG. 12, the fluctuation range (P-P value) of the received field strength of the combined output by that level difference. Therefore, it is desirable to design in consideration of this level difference, or to design after combining both output levels so as to eliminate the level difference.

(2) In the above embodiment, the center frequency of the reception target frequency range is adopted as the reference frequency used when obtaining the vertical separation phase θ _δ and the feeding phase θ _L , but the present invention is not limited to this. It may deviate from the frequency.

(3) In the above embodiment, the ground reflection coefficient is treated as R = −1. However, when the difference between the height of the transmission point and the reception point is large near the transmission point, the ground reflection wave is grounded. The absolute value of the ground reflection coefficient is smaller than 1 in the situation where the ground contact angle that is the angle of incidence on the ground becomes large. For this reason, when obtaining the vertical separation phase θ _δ and the feeding phase θ _L , it is desirable to use a ground reflection coefficient corresponding to the situation with reference to FIG.

(4) In the above embodiment, the propagation path length difference Δr ₁ of the direct wave with respect to the reference path and the propagation path length difference Δr ₂ of the ground reflected wave with respect to the reference path are treated as approximately equal. When the difference between the height h ₁ and the height h ₂ of the reception point is small or the distance d between the transmission and reception points is short, it is desirable to handle the propagation path length differences Δr ₁ and Δr ₂ without approximation. If not approximated, Δr ₁ <Δr ₂ , and the ground reflection wave has a larger phase change amount.

(5) In the above embodiment, the heights h ₁ and h ₂ of the transmission / reception points are the heights from the ground plane assuming that the ground is a flat surface. When the roundness of the ground cannot be ignored, it is desirable to use an effective height (lower than the height from the ground) with respect to the plane in contact with the reflection point of the ground reflected wave. Furthermore, it is desirable to use the equivalent radius of the earth calculated in consideration of the fact that the propagation of radio waves is affected by the refractive index of the atmosphere on the earth surface.

  (6) In the above embodiment, the case where the reception target radio wave is mainly horizontally polarized has been described, but the reception target radio wave may be vertical polarization. As shown in FIG. 4, the vertical polarization causes a ripple although the influence of the height pattern is small compared to the horizontal polarization. For example, in the polarization MIMO technology that is being studied in the future for practical application of 8K Super Hi-Vision, it is necessary to suppress the influence of the height pattern for both horizontal polarization and vertical polarization. Technology is considered to contribute extremely effectively.

  (7) The functions of one component in the above embodiment may be distributed to a plurality of components, or the functions of a plurality of components may be integrated into one component. Further, at least a part of the configuration of the above embodiment may be replaced with a known configuration having the same function. Moreover, you may abbreviate | omit a part of structure of the said embodiment. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  (8) In addition to the stack antenna described above, the present invention can also be realized in the form of a system having the stack antenna as a component.

  DESCRIPTION OF SYMBOLS 1 ... Stack antenna 2 ... Antenna part 3 ... Synthesis | combination part 21,22 ... Reception antenna 31, 32 ... Feed line 33 ... Synthesizer

Claims (6)

An antenna section (2) composed of a pair of receiving antennas (21, 22) installed at the top and bottom;
A synthesizer (33) for synthesizing the outputs of the receiving antennas, and a synthesizer (3) comprising a pair of feed lines (31, 32) for connecting each of the pair of receiving antennas and the synthesizer;
With
A radio wave within a preset frequency range is a reception target radio wave, a combination of a direct wave reaching the antenna unit from the transmission source of the reception target radio wave and a ground reflected wave is a combined wave, and the antenna unit is The phase difference of the combined wave received by each of the constituting receiving antennas is set as the vertical separation phase, and the phase difference of the combined wave due to the line length difference of the pair of feed lines is set as the feed phase, and is set within the frequency range. The vertical separation distance, which is the arrangement interval of the pair of receiving antennas, and the line length of the pair of feeder lines are set so that the sum of the vertical separation phase and the feeding phase generated at the reference frequency is 180 °. A stack antenna.   The stack antenna according to claim 1, wherein the reception antenna receives horizontally polarized waves.   The stack antenna according to claim 1, wherein the reference frequency is a center frequency of the frequency range.   4. The stack antenna according to claim 1, wherein each of the vertical separation phase and the feeding phase is 90 °. 5.   4. The stack antenna according to claim 1, wherein the vertical separation phase and the feeding phase are both in a range of 30 ° or more and 150 ° or less. 5. The vertical separation distance δ is set according to the following equation, where h ₁ is the installation height of the transmission source, λ is the wavelength of the reference frequency radio wave, and d is the distance from the transmission source to the antenna unit. The stack antenna according to any one of claims 1 to 3, wherein:
δ = λ × d / (4 × h ₁ )