JP2019080128A - Circularly polarized omnidirectional antenna, array antenna, and polarization diversity communication system using the same - Google Patents

Abstract

To provide a low-profile circularly polarized antenna that can be easily colinear arrayed.SOLUTION: An antenna 1 is disposed such that dipole antennas whose phases are inverted with each other are offset with respect to the horizontal plane to be point symmetrical with respect to a feeding point at a predetermined distance apart as at least one pair. The dipole antenna has a shape having current components in the vertical and horizontal directions when viewed from two orthogonal directions in the horizontal plane, and is fed by a feeding part from the central feeding point.EFFECT: The antenna becomes omnidirectional in the circular polarization horizontal plane at low profile. Also, when the antennas is formed in a co-linear array, a polarization diversity system can be easily configured.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to wireless communication technology, and more particularly to a circularly polarized non-directional antenna and a polarization diversity communication system using the same to switch left and right two circularly polarized waves.

  In the environment where the mobile station and the fixed base station are connected by wireless communication and information on the mobile station side is transmitted to the base station side, the positional relationship between the mobile station and the base station changes, Due to reflections from various obstacles, fading (multipath) and the like occur, which greatly hinders communication distance and communication stability. As a countermeasure against this fading, if the transmission output is increased in order to supplement the communication margin, there is a problem that the transmission rate is lowered in the communication state where the reception sensitivity is lowered while the communication sensitivity is lowered. . Therefore, there is a diversity scheme in which communication is continued without interruption by switching to another channel instead of the channel with lowered reception sensitivity.

  For example, it is conceivable that there is a mobile station in a water gauge provided in a river or the like, information of the water gauge is transmitted to the base station, and information (water level, position information) of the water gauge is collected at the base station side. . As the water level changes, the positional relationship between the water level gauge and the base station changes, and reflected waves from the water surface, the ground, or other buildings are more strongly received, resulting in fading (multipath) interference. In such a case, if transmission and reception are performed using circularly polarized waves, the reflected waves are reversely polarized waves, so that direct waves can be selected with a high degree of separation. Nevertheless, when the reflected wave becomes large and the direct wave becomes small, by switching the antenna on the mobile station side to another antenna for transmission, transmission and reception can be performed using radio waves most advantageous for communication. At this time, when the communication channel used for switching is a communication channel of reverse rotation polarization, interference with the original communication channel is small and communication is not interrupted. Such communication technology using radio waves with different polarizations is called polarization diversity.

  Heretofore, helical antennas have been mainly used as circularly polarized non-directional antennas used for communication using circularly polarized waves. This helical antenna is a traveling wave antenna having a shape as shown in FIG. 12, and the current flowing through the helical portion of the antenna becomes the current of the traveling wave traveling forward while turning along the helical portion. Then, from the current, a circularly polarized traveling wave electromagnetic field is emitted forward (end fire mode). Patent Documents 1 to 5 disclose conventional traveling wave helical antennas.

JP 2004-356929 A Patent 2717741 Japanese Utility Model Application Publication No. 61-42112 Japanese Patent Application Laid-Open No. 63-30006 Japanese Examined Patent Publication 7-58858

  By the way, in the above-mentioned helical antenna, it is necessary to realize a helical shape accurately, and the processing and fixing method therefor are difficult, and the manufacturing cost is high. In addition, the traveling wave helical antenna also has a problem that it is difficult to form a colinear array because of its shape.

The antenna of the present invention has the following features in order to solve the above problems.
The present invention is a horizontal omnidirectional circularly polarized antenna, wherein
The array antenna according to the present invention is characterized in that an antenna unit in which the above-mentioned antennas are alternately laminated coaxially as element antennas is coaxially laminated by rotating 90 ° each.
The polarization diversity communication system of the present invention is characterized by using the above-mentioned horizontal omnidirectional circular polarization antenna.

According to the present invention, by adopting a simple configuration in which dipole antennas are provided at a predetermined interval and at least one pair facing each other at a predetermined rising angle with respect to a horizontal surface, low profile non-directionality in a horizontal surface It is possible to realize a circularly polarized antenna and reduce the manufacturing cost. Further, the shape of the antenna does not have to be exactly circular as in the case of a helical antenna, and can be efficiently incorporated in a square case or the like.
Also, conventionally, it has been difficult to reduce the amount of coupling between adjacent antennas when arrayed, but with the antenna of the present invention, it becomes possible to reduce the amount of coupling between antennas, and adjacent cross polarization Since the distance between the element antennas can be shortened, the entire array antenna can be miniaturized.
As a total, it is possible to provide a polarization diversity communication system capable of inexpensive and stable communication.

Top view of the circularly polarized omnidirectional antenna according to the first embodiment of the present invention Front view of a circularly polarized omnidirectional antenna according to a first embodiment of the present invention Side view of the circularly polarized omnidirectional antenna according to the first embodiment of the present invention Upper perspective view of the circularly polarized omnidirectional antenna according to the first embodiment of the present invention Lower perspective view of the circularly polarized omnidirectional antenna according to the first embodiment of the present invention Modification of the circularly polarized omnidirectional antenna of the present invention Graph showing axial ratio in horizontal plane of antenna of Example 1 of the present invention Upper perspective view of the circularly polarized omnidirectional antenna according to the second embodiment of the present invention Lower perspective view of the circularly polarized omnidirectional antenna according to the second embodiment of the present invention Top view of the circularly polarized omnidirectional antenna of the second embodiment of the present invention Front view of a circularly polarized omnidirectional antenna according to a second embodiment of the present invention Side view of the circularly polarized omnidirectional antenna of the second embodiment of the present invention Bottom view of circularly polarized omnidirectional antenna according to Example 2 of the present invention Graph showing the directivity characteristic of the antenna of Example 2 of the present invention Overview of collinear array of circularly polarized omnidirectional antenna according to the third embodiment of the present invention Illustration of feeding of array antenna Graph showing the coupling amount of adjacent element antennas Overview of collinear array antenna according to the fourth embodiment of the present invention Graph showing the amount of coupling when the direction of each element antenna is changed Graph showing directivity (axial ratio, gain) of the array antenna of Example 4 of the present invention Illustration of communication system by polarization diversity Overview of conventional helical antenna

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, but extends to all the things included in the technical concept.

<Circular polarized non-directional antenna>
The appearance of a circularly polarized omnidirectional antenna is shown in FIG. 1A is a top view of the antenna 1, FIG. 1B is a front view of the antenna 1, and FIG. 1C is a side view of the antenna 1. Further, FIG. 1D is a view of the antenna 1 as viewed obliquely from the upper left, and FIG. 1E is a view of the antenna 1 as viewed from the lower left.
The antenna 1 has hot side elements 21 and 22 provided on the upper surface side of a substrate-like spacer 50 which is an insulator in a horizontal plane, and is connected to the hot side feeding point 10 by the hot side feed parts A1 and A2, respectively. (Figure 1A).

Further, cold side elements 31 and 32 are provided on the lower surface side of the substrate-like spacer 50, and are connected to the cold side feeding point 13 by the cold side feeding portions B1 and B2 (FIG. 1E). The hot side feed point 10 and the cold side feed point 13 are connection points with the hot side and the cold side of the parallel line which is the feed line 40, respectively. As can be seen from FIGS. 1A to 1E, the hot side elements 21 and 22 have a hot side feeding point 10, and the cold side elements 31 and 32 are point symmetrical with respect to the cold side feeding point 13 (FIG. 1B). ~ C).
The hot side elements 21 and 22 are composed of continuous first horizontal portions 21A and 22A, oblique portions 21B and 22B, and second horizontal portions 21C and 22C. Similarly, the cold side elements 31 and 32 are formed of continuous first horizontal portions 31A and 32A, oblique portions 31B and 32B, and second horizontal portions 31C and 32C.
The oblique portion following the first horizontal portion is offset by a predetermined angle with respect to the horizontal plane. This angle depends on the size and shape of the antenna.

The design parameters of the antenna of FIG. 1 are, for example, as follows. When the length is normalized with the free space wavelength λ at the center frequency of the operating frequency band, the size in the horizontal (x) direction is 0.21 λ, the size in the vertical (y) direction is 0.18 λ, and the height from the spacer 50 ( z) The direction length is 0.08λ, the wire length of the hot side element and the cold side element is 0.23λ, and the angle of the oblique portion is 35 ° with respect to the horizontal plane (FIG. 1A, C). At this time, omnidirectionality in the horizontal plane can be obtained by circular polarization.
When the angle of the oblique portion is reversed (-35 ° in the case of the example of FIG. 1), reverse rotation polarization is transmitted.
Next, the operation of the antenna of FIG. 1 will be described qualitatively. 1A and 1B, the antenna element pair of the hot side element 21 and the cold side element 32 forms one dipole antenna from the front direction (0 degree), and the antenna of the hot side element 22 and the cold side element 31 The element pair forms another dipole antenna. It can also be viewed as a turn-style (cross dipole) antenna in which the antenna element pairs are opposed to each other at an angle of 70. Therefore, it can be seen that circularly polarized waves are emitted in the front direction.

On the other hand, referring to FIGS. 1A and 1C, the antenna element pair of the hot side element 21 and the cold side element 31 forms one dipole antenna from the side direction (90 degrees), and the hot side element 22 and the cold side element 32. One antenna element pair forms another dipole antenna, and these antenna element pairs can also be viewed as cross-turned (cross dipole) antennas. Thus, it can be seen that circularly polarized light is emitted in the side direction.
The description of the other intermediate directions is omitted, but it is also qualitatively understood that circularly polarized non-directional in the horizontal plane as well.
The shape of this antenna is vertical (height (z-axis)) and horizontal direction when viewed from at least two directions (horizontal (x) and vertical (y)) in the horizontal plane for each cold-side element and hot-side element It may be any shape as long as the current component matches (horizontal (x-axis), vertical (y-axis)). Further, as a characteristic, it is sufficient that the horizontal polarization and the vertical polarization component in the horizontal plane be matched. Any shape may be used as long as the dipole antenna is offset at a predetermined angle with respect to the horizontal plane and arranged at predetermined intervals so as to be point symmetric with respect to the feeding point.
Specifically, FIG. 1F shows a modification of the shapes of the hot side element and the cold side element. When viewed from the top of the antenna, it has a line-symmetrical shape with respect to 0 degree (longitudinal (y-axis)), and the length also when viewed from 0 degree (y-axis) and 90 degrees (horizontal (x-axis)) direction As long as it has a shape, it may be any shape such as a bowl shape, a diagonal line, a circular arc, or a polygon. Then, the hot side element and the cold side element are offset at a predetermined angle on the front side and the rear side at the front side and the back side as a substrate, so that the current components of the hot side element and the cold side element It is within the scope of the present invention to have a configuration in which both the vertical (z-axis) direction and the horizontal (x, y-axis) direction coincide with each other.
Further, although the feed portion, the hot side element and the cold side element are provided on the substrate in the present embodiment, if the respective feed portions and elements are arranged in a predetermined positional relationship with respect to the horizontal plane corresponding to the position of the substrate, There is no need for a substrate.

Then, the measurement result is shown in FIG. 2 about the axial ratio of the circular polarization in the horizontal surface of the antenna of Example 1. FIG.
At the center frequency (fc), the value is 1 [dB] or less, and it can be seen that good circular polarization is transmitted in the horizontal plane. In addition, the axial ratio is 2 [dB] or less also in the relative bandwidth of 10% above and below the central frequency, and it can be seen that the circularly polarized wave is sufficiently good.

In the first embodiment, an antenna in which the hot feed side and the cold feed side are supplied from the feed line 40 using the parallel feed line has been described. In the second embodiment, an antenna for feeding two hot-side elements and two cold-side elements at one point feeding of the hot-side feeding point 10 using a microstrip line formed on the printed wiring board of the spacer 50 will be described. Do.
The appearance of the circularly polarized omnidirectional antenna of Example 2 is shown in FIGS.
3A is a view of the antenna viewed obliquely from above, FIG. 3B is a view of the antenna viewed obliquely from below, FIG. 3C is a top view, FIG. 3D is a front view, FIG. 3E is a side view, and FIG. is there.

Referring to FIGS. 3A and 3B, the hot-side elements 121 and 122 are formed in an arc shape in a five-fold manner from diagonally upward from the surface side of the printed wiring board. On the contrary, the cold-side elements 131 and 132 are formed in an arc shape in a five-fold manner from diagonally downward from the back surface side of the printed wiring board. The hot elements 121 and 122 are connected to the feed lines A1 and A2 at connection points 121A and 122A, respectively.
The cold-side elements 131 and 132 are connected to the feed lines B1 and B2 at connection points 131B and 132B, respectively. The feed lines A1, A2, B1 and B2 are connected to the hot side of the feed cable at one point of the common feed point O.

The cold side of the feed cable is connected to the ground 51 on the back surface of the printed wiring board, and the feed lines A1, A2, B1 and B2 are formed on the surface of the printed wiring board to form a strip line.
Further, since both the hot side element and the cold side element are connected to the hot side of the feed cable, the excitation of the hot side element and the cold side element must be 180 ° phase-reversed. Therefore, the hot side power supply line A1, A2 from the cold side power supply line B1, B2 meander line in order to lengthen only the wiring length when the guide wavelength of the stripline and λ _g λ _g / 2 at the center frequency of the use frequency band Parts B1M and B2M are provided.
As described above, the feed system was configured by the strip line.

Next, a specific design shape of the antenna of the second embodiment will be described.
Referring to the top view of FIG. 3C, the circular diameter of the antenna is 0.21 λ, normalized to the free space wavelength λ. The hot side element and the cold side element have a length of 0.25 λ (1/4 λ). Further, referring to FIG. 3E, the hot side element and the cold side element each have a height of 0.08 λ from the printed wiring board, and each element has an angle of about 20 ° with the printed wiring board at that time.

Next, the directivity characteristic of the antenna made from the above design parameters is shown in FIG.
It can be seen that the solid line is directional in the horizontal plane, extremely flat and omnidirectional in the horizontal plane. On the other hand, the vertical in-plane directivity of the dashed-dotted line is the vertical direction. The gain drops very sharply at 0 ° and 180 °. With this single antenna, the directivity in the vertical plane is ± 50 ° (−3 dB), and it can be seen that circular polarization is mainly radiated in the horizontal direction.

<Colinear array antenna>
Next, a collinear array antenna of the first embodiment will be described.
FIG. 5 shows how three circularly polarized nondirectional antennas shown in FIG. 1 are vertically stacked and arrayed. In the figure, right-handed horizontal and left-handed vertical are described, but this will be explained in a retrospective manner in Fig. 7. However, by making the hot-side and cold-side elements into folded dipoles with the right-handed polarization antenna, respectively, horizontal polarization The use as an antenna, and the use as a vertical polarization antenna by increasing the angle of the oblique portion of the hot and cold side elements with a left-handed polarization antenna, are represented.
The shape of the middle element antenna 100M in FIG. 5 is a folded dipole antenna, and the element shape of the dipole antenna and the rising angle are set so that the horizontal polarization component becomes larger than the vertical polarization component in all directions in the horizontal plane. ing. Further, the shapes of the upper element antenna 100T and the lower element antenna 100B are set to the element shape and the rising angle of the dipole antenna so that the vertical polarization component becomes larger than the horizontal polarization component in all directions in the horizontal plane. ing.
In the upper element antenna 100T of FIG. 5 and the lower element antenna 100B, radio waves of the same vertical polarization (left-handed antenna) are excited in phase, and the middle element antenna 100M and the other antennas are different horizontally polarized waves (right-handed antenna ) Is excited. Each array element antenna is wired such that each element antenna is excited in phase by the tournament method as shown in FIG. FIG. 6 shows a configuration example of an eight-element array antenna. This tournament type distribution is performed using distribution lines D1 to D6 provided in the substrate of each element antenna. FIG. 5 illustrates the configuration of the broken line in FIG. In FIG. 5, power feeding to the upper and lower element antennas 100T and 100B using the distribution line D3 of the middle element antenna will be described.

First, the hot elements 121T and 122T are fed to the upper element antenna 100T of FIG. 5 from the hot feed point 10T via the hot feeds A1T and A2T. Similarly, to the lower element antenna 100B, the hot elements 121B and 122B are fed from the hot feed point 10B via the hot feeds A1B and A2B.
Distribution lines D3 and D4 are provided on the substrate surface of the middle element antenna 100M. The wiring length of the distribution lines D3 and D4 is set to λ _g / 4 in order to achieve impedance matching. Unlike the upper and lower element antennas 100T and 100B, the antenna element portion of the antenna 100M in the middle of the figure is a folded dipole antenna in order to use horizontal polarization as main polarization.
The feed line distributed in a tournament manner from the excitation source is connected to the feed point FD2 of the distribution line D3. Then, the FD 1 at the other end of the distribution line D3 is connected to the feeding point 10T of the upper element antenna 100T and the feeding point 10B of the lower element antenna 100B. In this manner, power is supplied to the upper element antenna 100T and the lower element antenna 100B of the left-handed polarization.
On the other hand, the antenna 100M of right-handed polarization is connected from the end portion FD3 of the distribution line D2 provided on the upper element antenna 100T to the feeding point 10M of the middle element antenna 100M.
By arranging the distribution lines D2 and D3 on the element antennas 100T, M and B as shown in FIG. 6, an array antenna is skillfully constructed.

FIG. 7A shows the coupling amount of adjacent circularly polarized antennas when excited as horizontally and vertically linearly polarized antennas. Originally, in the element antenna of Example 1, the vertical in-plane directivity hardly radiates in the vertical direction, so that the element antennas are separated (FIG. 4). And since the separation of the circularly polarized antenna of the present invention is high, it was excited with horizontal and vertical linearly polarized waves to show it. The distance between the two element antennas is 0.6λ. From FIG. 7 (a), the same polarized waves (for example, left-handed polarized antenna (ex. Upper element antenna 100T) represented by dotted lines are excited with vertical polarization, and another left-handed polarized antenna (ex. Lower) Even when vertically polarized waves are received by the element antenna 100B), the coupling amount is as small as about -15 to -20 [dB] in a ratio band of 10% above and below the center frequency (fc). It has become. The different polarizations (for example, left-handed polarization antenna (ex. Upper element antenna 100T)) are excited with vertical polarization, and horizontally polarized waves are generated with the right-handed polarization antenna (ex. Middle element antenna 100M). In the case of reception), the coupling amount is very low such as -35 to -42 [dB]. This is because the coupling amount in the case where the normal vertically polarized dipole antenna and the horizontally polarized dipole antenna are adjacent to each other is about -20 [dB], which is further lower by 20 [dB]. It has been shown that the antenna of the present invention is suitable for arraying in the vertical direction because the shape is low profile and the radiation direction is horizontal.
Moreover, the same directivity can be obtained while having different polarization, and therefore, it can also be used as a MIMO antenna.

FIG. 7 (b) shows the directivity in the horizontal plane when the circularly polarized antenna for both right-handed and left-handed rotation is excited as a vertical / horizontally polarized antenna. The solid line indicates the vertical polarization gain (main polarization) when the right-handed polarization antenna is excited with vertical polarization, and the dotted line indicates the horizontal polarization gain (crossing when the right-handed polarization antenna is excited with vertical polarization When the left-handed polarization antenna is excited with horizontal polarization, the one-dot chain line excites the horizontal polarization gain (main polarization) when the left-handed polarization antenna is excited with horizontal polarization, and when the two-dot chain line is excited with the left-handed polarization antenna. Vertical polarization gain (cross polarization) of In both cases, it can be read that the gain is about 7 to 8 [dB] in the main polarization and the cross polarization.
Although the degree of polarization separation of each antenna is not high, when arraying this antenna as an element antenna, the right-handed polarization antenna is excited with vertical polarization and the left-handed polarization antenna is excited with horizontal polarization. By doing this, it is possible to reduce the coupling amount of the element antennas of each other.

Next, a right-handed polarization antenna and a pair of left-handed polarized antennas rotated 90 ° are stacked to form one antenna unit, and each antenna unit is further rotated 90 ° to make the four antenna units coaxial. A configuration in which a collinear array antenna of eight element antennas is configured by stacking is shown in FIG. FIG. 8 (a) is a schematic view seen from diagonally below, and FIG. 8 (b) is a schematic view seen from diagonally above.
As shown in FIG. 8, by rotating each unit by 90 °, each element antenna characteristic is superimposed, thereby eliminating deviation of directivity in the horizontal plane and obtaining uniform and favorable axial ratio characteristics in the horizontal plane. Is possible.
In the co-linear array antenna of FIG. 8, the height of one unit is 0.34 λ and the unit interval is 0.45 λ when normalized with the free space wavelength λ.
In FIG. 9, when antennas with different polarizations of right-handed and left-handed rotation are arranged in the same direction at an interval of 0.2λ (dotted line), each element antenna is rotated by 90 ° as shown in FIG. The amount of coupling with the arrangement in (solid line) is compared in a relative bandwidth of 10% above and below the center frequency (fc).
It can be seen that, by using the arrangement by rotating the element antennas by 90 ° as in Example 4, good separation characteristics are obtained even if the distance between the element antennas is reduced.

Next, the radiation characteristic of the antenna of the fourth embodiment will be described with reference to FIG.
FIG. 10A shows the axial ratio in the horizontal plane of the antenna of the fourth embodiment. The center frequency (fc) is indicated by an alternate long and short dash line, where the frequency is indicated by a solid line (fc-10%) and the frequency is indicated by a dotted line (fc + 10%).
In all these, it is less than 2 [dB]. Generally, the axial ratio is acceptable up to about 3 [dB], and it can be seen that sufficient characteristics are obtained in the present embodiment. Further, it can be understood that the deviation of the directivity in the horizontal plane is suppressed by arranging the antennas offset by 90 °, and uniform characteristics can be obtained.
Next, FIG. 10 (b) shows the directivity of the four-stage collinear array. The dotted line is directivity in the horizontal plane, and the solid line is directivity in the vertical plane. In the vertical in-plane directivity, the gain drops very sharply at 0 ° and 180 °, and it can be seen that the radiation direction is horizontal.

<Diversity communication system>
Next, FIG. 11 is a block diagram showing a configuration of a diversity communication system including an antenna capable of transmitting and receiving right-handed and left-handed circularly polarized waves to which a circularly polarized antenna according to an embodiment of the present invention is applied. FIG. 11A is a block diagram showing the configuration of the diversity communication system, and FIG. 11B is a block diagram showing the configuration of the diversity communication device.
In terrestrial radio communication links, fading is present, which greatly hinders communication distance and communication stability. In order to compensate for this fading, increasing the transmission power increases the cost. Also, if the transmission power is not changed, the transmission rate will be limited. Diversity is one of the radio technologies, and in order to prevent the effects of fading due to mutual interference of radio waves, radio waves are received from a plurality of antennas, signals of high quality are selected, signals are combined, and so on. It is a technology that raises quality and reliability. The diversity includes space diversity for receiving with a plurality of antennas installed at a distance, polarization diversity for installing antennas for receiving a plurality of different polarizations, and time diversity with a plurality of times of signal transmission offset is there.

  The diversity communication system shown in FIG. 11A shows a configuration example in which diversity communication is performed by polarization diversity using right-handed circular polarization and left-handed circular polarization. This diversity communication system includes a diversity communication device 230-1 including an antenna 140-1 capable of transmitting and receiving circularly polarized waves in right and left rotations, and a diversity communication including an antenna 140-2 capable of transmitting and receiving circularly polarized waves in right and left rotations. And a machine 230-2. The antenna 1 according to the present invention can be applied to the antenna 140-1 and the antenna 140-2.

Since the configurations of diversity communication device 230-1 and diversity communication device 230-2 are the same, a block diagram showing the configuration of diversity communication device 230-1 as a representative is shown in FIG. 11 (b) and described. Diversity communication unit 230-1 includes, for example, a transmitter 233 that encodes and modulates data from a water level meter and the like to send out a transmission signal, and a receiver 234 that demodulates and decodes a reception signal to obtain original data, A transmitter / receiver switch 232 for switching between transmission and reception, an antenna switch 231 for switching the turning direction of circular polarization transmitted and received by the antenna 140-1 by right rotation and left rotation, and a microcontroller 235 for controlling each part It consists of
Although the operation of the diversity communication device 230-1 will be described, the operation of each part is controlled by the microcontroller 235. At the time of transmission, since the transmission / reception switch 232 is switched to transmission, the transmission signal transmitted from the transmitter 233 is sent to the antenna switch 231 via the transmission / reception switch 232. The antenna switching device 231 is switched to, for example, a right-handed circularly polarized antenna, and a transmission signal is transmitted from the antenna 140-1 with right-handed circular polarization. The transmitted signal of the right-handed circularly polarized wave transmitted is received by the antenna 240-2 in the diversity communication device 230-2 on the receiving side, and the received signal received by the antenna switch 231 with the circularly polarized antenna of the right-handed rotation Are switched to be sent to the sending / receiving switch 232. The transmission / reception switch 232 switches to supply the reception signal to the receiver 234. If the reception level of the signal received by the receiver 234 has reached a predetermined reception level, it is determined that reception is possible, and the original data can be received.

Also, if the reception level of the signal received by the receiver 234 has not reached the specified reception level, the reception signal received by the left-handed circularly polarized antenna in the diversity communication device 230-2 on the reception side is The antenna switching device 231 is switched so as to be sent to the transmission / reception switching device 232. As a result, when the reception level of the signal received by the receiver 234 has reached a predetermined reception level, it is determined that reception is possible, and the original data can be received. This is because when the circularly polarized wave is reflected, it becomes a reverse polarized wave, and the level of the radio wave reflected once is relatively large, and the received level becomes higher if the reverse polarized wave is received. Because there is
Thus, in the diversity communication system, communication can be performed by the combination of the following (1) to (4), and switching to the combination of the following (1) to (4) is sequentially performed until a prescribed reception level is obtained: Communication may be performed.
(1) [Transmission side] Right-handed circular polarization: [Reception side] Right-handed circular polarization (2) [Transmission side] Right-handed circular polarization: [Reception side] Left-handed circular polarization (3) [Transmission side] Left-handed circular polarization: [reception side] left-handed circular polarization (4) [transmission side] left-handed circular polarization: [reception side] right-handed circular polarization When a specified reception level is obtained in the diversity communication system Alternatively, the receiver may transmit data to notify the transmitter that communication has been established.

  In the above-described diversity communication system, it is possible to reduce the effects of fading caused by rainfall or changes in the ground due to rainfall, changes in the water level of paddy fields or rivers, or changes in tide level. From this, when transmitting the water gauge data, the use of the above-described diversity communication system is particularly effective. In addition, since the physical positions of the circularly polarized antennas for right-handed and left-handed ones are different, they also function as space diversity, so the correlation of the propagation path is lowered, and the effects of both polarization diversity and space diversity are obtained. Not only flat fading, but also selective fading based on shielding of a car or the like is effective, and stable communication becomes possible. The communication system in which the circular polarization array antenna 1 of the present invention of the present invention is applied to the antenna 140-1 of the first station and the antenna 140-2 of the second station of FIG. 11 has been described. Even if the antenna is not applied to both stations, the effect is sufficiently exhibited.

10 hot side feed point
13 cold side feed point
21, 22 hot side element
31, 32 Cold side element
50 Spacer

Claims (17)

  An omnidirectional circularly polarized antenna in a horizontal plane provided with a dipole antenna at a predetermined interval and at least one pair facing each other at a predetermined rising angle with respect to the horizontal plane.   2. The horizontal plane according to claim 1, wherein the dipole antenna has an element shape of the dipole antenna and the rising angle so that horizontal polarization and vertical polarization components match in all directions in the horizontal plane. Directional circularly polarized antenna. The dipole antennas are arranged in point symmetry,
The horizontal omnidirectional circularly polarized antenna according to claim 1, wherein the dipole antenna has a shape in which current components in the vertical and horizontal directions coincide with each other when viewed from at least two directions in the horizontal plane.   4. The dipole antenna according to claim 1, wherein an element shape of the dipole antenna and the rising angle are set such that the vertical polarization component is larger than the horizontal polarization component in all directions in the horizontal plane. The horizontal nondirectional circularly polarized antenna according to any one of the above.   4. The dipole antenna according to claim 1, wherein an element shape of the dipole antenna and the rising angle are set such that a horizontal polarization component becomes larger than a vertical polarization component in all directions in a horizontal plane. The horizontal nondirectional circularly polarized antenna according to any one of the above.   The dipole antenna is provided so as to be separated in a direct current sandwiching the substrate, the hot side element is provided on the substrate surface side, and the cold side element is provided on the substrate back surface side so as to be offset. The horizontal nondirectional circularly polarized antenna according to any one of the above. The pair of dipole antennas are arranged in point symmetry with respect to a feeding point on the substrate,
The horizontal omnidirectional circularly polarized antenna according to claim 6, wherein each of the feeding points is fed through a feeding unit.   The horizontal side nondirectionality according to any one of claims 6 to 7, wherein the hot side feed section feeds power from the hot side of the feed line and the cold side feed section feeds from the cold side of the feed line. Circularly polarized antenna.   Each of the feeding parts is fed from the hot side of the feeding wire, and the cold-side feeding part is provided with a wiring part which reverses the phase with respect to the hot-side feeding part. The horizontal omnidirectional circularly polarized antenna according to any one of the items 1 to 4.   The horizontal omnidirectional circularly polarized antenna according to any one of claims 1 to 7, wherein the dipole antenna is a folded dipole antenna. An antenna unit is configured by coaxially laminating one set of the horizontal surface omnidirectional circular polarization antenna according to any one of claims 1 to 10 for right-handed polarization and left-handed polarization as an element antenna,
An array antenna characterized in that the antenna units are coaxially stacked.   The array antenna according to claim 11, wherein a distribution line is formed on a substrate of the element antenna, and the other element antenna is fed.   The array antenna according to any one of claims 11 to 12, wherein the antenna unit is coaxially stacked by rotating the antenna unit by 90 °.   11. The in-horizontal surface omnidirectional circularly polarized antenna according to any one of claims 1 to 10, which is used in a polarization diversity communication system of left-handed circularly polarized light and right-handed circularly polarized light.   11. The in-horizontal surface omnidirectional circularly polarized antenna according to any one of claims 1 to 10, which is used in a polarization diversity communication system of vertical polarization and horizontal polarization.   A polarization diversity communication system using an omnidirectional circular polarization antenna in a horizontal plane according to any one of claims 1 to 10.   A polarization diversity communication system using the array antenna according to any one of claims 11 to 13.

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