JP3445431B2 - Circularly polarized patch antenna and wireless communication system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless LAN, for example.
And a wireless communication system such as a wireless LAN using the circularly polarized patch antenna.

[0002]

2. Description of the Related Art An antenna used for a base station such as a wireless LAN is required to have a simple structure, a small size, a thin shape and a low cost. In addition, it is desirable that the beam be tilted in a non-directional manner in the horizontal plane and the beam be tilted downward in the vertical plane.
Further, for performing high-speed transmission of, for example, about 100 Mbps, a circular polarization antenna that can reduce the influence of multipath is suitable.

By the way, as an antenna for realizing the beam tilt, (1) an antenna of a linear element system, (2) an antenna of a patch system and the like can be considered.

As a typical example of the linear element system antenna for realizing the beam tilt, there is a collinear antenna in which dipole elements are vertically arranged in multiple stages. However, in such a linear element system antenna, it is generally not easy to realize circular polarization, and the structure is often complicated.

On the other hand, the patch antenna is capable of circular polarization while realizing beam tilt. As a typical structure of a patch antenna, there is a structure in which a dielectric substrate is placed on a conductor plate, a patch antenna is formed on the dielectric substrate, and the patch antenna is fed directly. However, such a patch antenna cannot achieve omnidirectionality in the horizontal plane.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a circularly polarized patch antenna which is omnidirectional in a horizontal plane and can realize circular polarization.

An object of the present invention is to provide a circularly polarized patch antenna which can be simplified in structure, can be made small and thin, and can be manufactured at low cost.

An object of the present invention is to provide a circularly polarized patch antenna which can be easily arrayed and whose beam tilt is easy.

An object of the present invention is to provide a circularly polarized patch antenna which can be easily installed on the ceiling or the like.

An object of the present invention is to provide a wireless communication system capable of uniformly maintaining the electric field strength over a wide area and being resistant to multipath.

[0011]

In order to solve these problems, the circularly polarized patch antenna of the present invention according to claim 1 is arranged on a ground conductor plate and on the first surface side of this ground conductor plate. A first patch antenna for flowing a first image current corresponding to the supplied current in a predetermined rotation direction with respect to the ground conductor plate and a second surface side of the ground conductor plate, and the power is supplied. A second patch antenna for supplying a second image current corresponding to the current to the ground conductor plate so as to cancel the first image current; and a power feeding means for feeding power to the first and second patch antennas. It is equipped with.

According to a second aspect of the present invention, there is provided a circularly polarized wave patch antenna which is arranged on a ground conductor plate and a first surface side of the ground conductor plate, and which is arranged in a first direction with respect to a first direction different from a feeding direction. A first patch antenna having a second width in a second direction different from the feeding direction and the first width being longer than the second width; The conductor plate is arranged at a position facing the first patch antenna on the second surface side, has the second width in the first direction, and has the second width in the second direction. A second patch antenna having a width of 1 and having substantially the same shape as the first patch antenna;
And a power feeding means for feeding power to the first and second patch antennas. Viewed from another side, the conductor plate and the first current path that is disposed on the first surface side of the ground conductor plate and in which the fed current flows in the first direction and the fed current are A first patch antenna having a second current path that flows in a direction, and the length of the first current path is longer than the length of the second current path; and a second patch antenna of the ground conductor plate. The first of the surface side
A third current path in which the fed current flows in the first direction and a fourth current path in which the fed current flows in the second direction, and A circularly polarized patch including a second patch antenna in which the length of the fourth current path is longer than the length of the third current path, and a power feeding unit that feeds power to the first and second patch antennas. It is an antenna.

A radio communication system according to a third aspect of the present invention is a radio communication system for transmitting and receiving data between a base station and a terminal via a radio communication path, wherein the base station is a ground conductor plate. A plurality of first patch antennas arranged on the first surface side of the ground conductor plate, each of which flows a first image current corresponding to a supplied current in a predetermined rotation direction with respect to the ground conductor plate; , A second image current, which is arranged at a position facing the respective first patch antennas on the second surface side of the ground conductor plate, and each of which supplies a second image current corresponding to a fed current to the ground conductor plate. A circular polarization patch array antenna having a plurality of second patch antennas that flow so as to cancel each of the first image currents and a power feeding unit that feeds power to the first and second patch antennas is provided.

The invention can be explained in principle as shown in FIG. As shown in FIG. 1, the first patch antenna 12 and the second patch antenna 13 are arranged on the respective surface sides of the ground conductor plate 11. Here, the first patch antenna 12 and the second patch antenna 13 are each configured to generate circularly polarized waves. That is, the first patch antenna 12 and the second patch antenna 13 are configured so that a current that rotates according to the supplied current flows. In response to these currents, the first image current 14 for the first patch antenna 12 and the second image current 15 for the second patch antenna 13 flow through the ground conductor plate 11, respectively. According to the present invention, the first patch antenna 12 and the second patch antenna 13 are configured such that the first image current 14 and the second image current 15 cancel each other. Here, a metal conductor is used as the ground conductor plate. Ground conductor plate and first and second
A dielectric substrate is usually interposed between the patch antenna and the patch antenna.

Metal conductors are also used for the first and second patch antennas. Various shapes of the first and second patch antennas can be considered as shown in FIGS. The solid line shows the shape of the patch antenna on the front surface, and the broken line shows the shape of the antenna on the back surface seen through the surface.

As the power feeding means, in addition to the coplanar (CPW) power feeding described later, the first and second patch antennas 34 and 35 have a common ground conductor plate 36 like the direct power feeding 32 shown in FIG. It may be of any type. 37 and 38 are dielectric substrates. These power supply means may supply power from the center of the first and second patch antennas, or may supply power from any other position.

The present invention can be applied not only to a single type consisting of a pair of first and second patch antennas, but also to an array antenna having a plurality of pairs of first and second patch antennas.

The circular polarization patch antenna of the present invention is suitable as an antenna for a base station of a wireless communication system such as a wireless LAN constructed in a building. Generally, such a system requires, for example, a large number of terminals to be arranged over a large area of one floor and to transmit and receive data accurately. On the other hand, the circularly polarized patch array antenna of the present invention is omnidirectional in the horizontal plane,
Since the beam can be tilted downward in the vertical plane and is circularly polarized, if this antenna is placed on the ceiling, for example, the electric field strength can be maintained uniformly over a wide area, and it is strong against multipath and transmits data more accurately. Because you can

[0019]

FIG. 4 is a diagram showing an example of a circular polarization patch antenna of the present invention.

As shown in FIG. 4, this circularly polarized patch antenna has a first patch antenna 42 made of substantially rectangular copper foil on each side of a ground conductor plate 41 made of, for example, a rectangular copper plate. The second patch antenna 43 is arranged,
Ground conductor plate 41 and first and second patch antennas 42, 4
3 and dielectric substrates 44 and 45, respectively. Further, as shown in FIG. 5, the ground conductor plate 41
Has an elongated conductor removing portion 46, and in the conductor removing portion 46, a CPW feed line 47 for electromagnetically coupled feeding is provided. An input / output terminal (not shown) is connected to the lower end of the CPW feed line 47.

In the first patch antenna 42, two corners in the first diagonal direction 48 are left as they are, and two corners in the second diagonal direction 49 are cut off by a predetermined amount. In addition, the second patch antenna 43 has two corners in the second diagonal direction 49 left as they are, and two corners in the first diagonal direction 48 are cut off by a predetermined amount. That is, the first patch antenna 42 is
Has a first width in a diagonal direction 48, a second width in a second diagonal direction 49, and the first width is longer than the second width. The patch antenna 43 of
Has a first width with respect to a second diagonal direction 49;
Has a second width with respect to the diagonal direction 48 of.

In this circularly polarized patch antenna, for example, a ground conductor plate 41 is bonded to one surface of a dielectric substrate 44, and CPW is used.
The feed line 47 is formed by etching removal. next,
The dielectric substrate 44 is adhered to the other surface of the ground conductor plate 41.
Next, the first patch antenna 42 and the second patch antenna 43 are formed on the surfaces of the respective dielectric substrates 44 and 45 by the photolithography technique.

The operation of this circular polarization patch antenna will be described.

As a method for achieving circular polarization, an antenna in which a dielectric substrate 62 is placed on a ground conductor plate 61 having a CPW feed line 60 and a patch antenna 63 is placed on it as shown in FIG. , The first of the patch antenna 63
Leave the two corners of the diagonal direction 64 of
It is conceivable to cut off two corners in the direction 65 of the diagonal line.

In this antenna, as shown in FIG. 7, the current flowing on the ground conductor plate 61 is affected by the CPW feeding line 60 and avoids the CPW feeding line 60, and the current flows so as to draw a large curve. For this reason, the current length is equivalently increased, and the frequency of circular polarization is lower than the frequency of matching with the CPW feed line 60, and the frequency at which good characteristics of both circular polarization and matching can be realized is Disappear.

That is, the frequency at which circular polarization is obtained and CPW
When trying to realize an antenna in which the frequency matched with the power supply line 60 substantially matches, the current flowing on the ground conductor plate 61 shown in FIG. 7 looks equivalently long.

The inventors of the present invention, if the current flowing on the ground conductor plate 61 can be canceled, the CPW feed line 60.
We considered that the mode degeneration could be resolved at a frequency that matched with, and a circularly polarized antenna could be realized.

Therefore, in the present invention, as shown in FIG. 4 , the first patch antenna 42 and the second patch antenna 43 are arranged so as to face each other with the ground conductor plate 41 interposed therebetween, and the first patch antenna 42 is First with respect to the first diagonal direction 48
And has a second width in the direction 49 of the second diagonal, and the first width is longer than the second width. Has a first width with respect to a second diagonal direction 49, and has a first diagonal direction 4
The second image current with respect to the first patch antenna 42 flowing through the ground conductor plate 41 and the second image current with respect to the second patch antenna 43 are configured so as to have a second width with respect to 8 They cancel each other out and generate almost omnidirectional circularly polarized waves in the horizontal plane.

By the way, as shown in FIG.
The first patch antenna 82 and the second patch antenna 83 are arranged so as to be opposed to each other with the first patch antenna 82 having a first width with respect to the first diagonal direction 88, and the second patch antenna 82.
Has a second width with respect to a diagonal direction 89 of
Of the second patch antenna 83 has a first width with respect to a first diagonal direction 88 and a second diagonal direction 89. On the other hand, in the antenna configured to have the second width, the image currents flowing on the ground conductor plate 81 are added to each other, and the frequency at which circular polarization is obtained and the frequency matching with the CPW feed line 80 match. It is not possible.

Next, experimental results of the circularly polarized patch antenna of the present invention shown in FIG. 4 will be shown.

In the circular polarization patch antenna of FIG. 4, the width of the dielectric substrate W = 70 mm, the length of the dielectric substrate H = 150 mm, the thickness of the dielectric substrate t = 3.2 mm, the width of the patch antenna La = 47.36 mm. Length of patch antenna Lb = 47.36 mm Crossing length of CPW feed line with patch antenna d = 25
mm CPW feed line width Si = 4.5 mm Conductor removed portion width So = 4.9 mm Patch antenna first width−Patch antenna second width = Δ = 4 mm, characteristic impedance 50Ω, center frequency 1. 9G
It was configured to resonate at Hz.

FIG. 9 shows the case of 1.85 GHz to 1.9.
The input impedance of 5 GHz and its Smith chart are shown. From FIG. 9, it can be seen that the input impedance has a kink around 1.905 GHz. Therefore, it can be seen that the circular polarization patch antenna of FIG. 4 can obtain circular polarization by canceling the mode degeneracy in the vicinity of the frequency matching the feed line.

On the other hand, the circular polarization patch antenna shown in FIG. 8 has the same characteristics as shown in FIG. From the figure, it can be seen that there is no kink on the Smith chart, it operates as a linearly polarized wave, and a circularly polarized wave cannot be obtained.

Next, in the circularly polarized wave patch antenna of the present invention shown in FIG. 4, Δ = 4 mm, frequency 1.905 GH
The radiation directivity of the horizontal plane at z is shown in FIG. In the figure, the 0 degree direction is -18 on one front of the double-sided patch.
The 0 degree direction is the other front. The radiation directivity of the vertical plane of the antenna is shown in FIG.

From FIG. 11, a circular polarization characteristic with an axial ratio of 4 dB or less was obtained over 360 degrees in the horizontal plane. In the front direction of both patches, the axial ratio was 2 dB or less.

The directivity of the vertical plane was the same as that of a normal circular polarization patch alone, and the axial ratio was a good circular polarization characteristic of 2 dB or less over a wide angle. A good circular polarization antenna can be realized by providing degenerate separation elements in the same direction with respect to the rectangular patch.

On the other hand, when the circular polarization patch antenna shown in FIG. 8 has the same characteristics with respect to the horizontal plane, it becomes as shown in FIG. In FIG. 13, Hpol-Hpol
Is the normal polarization characteristic, and Hpol-Vpol is the cross polarization characteristic. From FIG. 13, it can be seen that circular polarization cannot be realized.

The circularly polarized patch antenna of the present invention has a structure in which two dielectric substrates are simply superposed on each other, and therefore an array is structurally easy. In the array antenna, beam tilt can be performed by controlling the phase between the patch antennas at each stage. The phase can be controlled by appropriately setting the length of the CPW line. 14 and 15 show examples of circularly polarized patch array antennas.

FIG. 14 shows a circular polarization patch array antenna using a CPW feed line. In FIG. 14, reference numeral 141 denotes a ground conductor plate, and dielectric substrates 142 and 143 are arranged on both surfaces of the ground conductor plate 141, respectively. On the surfaces of the dielectric substrates 142 and 143, a pair of multi-stage (for example, four stages) patch antennas 144a-144b and 145a-14 are provided.
5b, 146a-146b, 147a-147b are arranged. These patch antennas 144a-144
b, 145a-145b, 146a-146b, 147
Each of the a-147b has two corners cut off in one diagonal direction, similarly to the antenna shown in FIG. The patch antennas 144a-144b are electromagnetically fed by the CPW feeding line 148a, and the patch antennas are electromagnetically coupled by the CPW feeding lines 148b to 148d.

FIG. 15 shows a circularly polarized patch array antenna using a direct feed line, which corresponds to C of the antenna shown in FIG.
Direct feed lines 150a to 150d instead of the PW feed line
Is used.

FIG. 16 is a diagram showing an example in which the circularly polarized patch antenna of the present invention is applied to a wireless LAN constructed in a building, for example.

In FIG. 16, 161, 161 ... Show terminals arranged on the floor. On the other hand, a base station 162 is installed on the ceiling, and the base station 162, the terminals 161, ...
Data is transmitted to and received from and via a wireless communication path. In this system, the circular polarization patch array antenna 163 according to the present invention is used for the base station 162. As the circularly polarized wave patch array antenna 163 according to the present invention, for example, the one shown in FIG. 14 is used. The circularly polarized patch array antenna 163 is, for example, 2.4 GHz.
It is about 30 cm in length and is not very noticeable even when installed on the ceiling of an office or the like.

[0043]

As described above, according to the circularly polarized patch antenna of the present invention, the first patch antenna and the second patch antenna are arranged to face each other with the ground conductor plate interposed therebetween, and Since the first image current flowing to the first patch antenna and the second image current flowing to the second patch antenna cancel each other, it is omnidirectional in the horizontal plane and circular polarization is realized. be able to. In particular, when a CPW power supply line is used as the power supply means, the frequency of circular polarization and the frequency of matching of the power supply line match, and good characteristics can be maintained.

Since the circularly polarized wave patch antenna of the present invention has a structure in which the first patch antenna and the second patch antenna are arranged to face each other with the ground conductor plate interposed therebetween, for example, the ground conductor plate and the first patch antenna are arranged. By inserting a dielectric substrate between the second patch antenna and the second patch antenna, the structure can be simplified and the size and thickness can be reduced. Further, in that case, since the first patch antenna and the second patch antenna can be formed by the photolithography technique, the mass productivity is excellent and the cost can be reduced. Further, in such a structure, since it is easy to form an array, beam tilt can be easily realized. Furthermore, it is easy to install on the ceiling, etc., and it is easy to supply power.

The circularly polarized patch array antenna of the present invention is
It is omnidirectional in the horizontal plane, can be beam tilted downward in the vertical plane, and is circularly polarized, so if this antenna is applied to a wireless communication system, the electric field strength can be uniformly maintained over a wide area, and A wireless communication system resistant to multipath can be provided.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a diagram showing various shapes of the patch antenna of the present invention.

FIG. 3 is a diagram showing various power supply means of the present invention.

FIG. 4 is a perspective view showing an example of a circular polarization patch antenna of the present invention.

5 is a perspective view of the ground conductor plate shown in FIG. 4. FIG.

FIG. 6 is a diagram for explaining the operation of the present invention.

FIG. 7 is a diagram for explaining the operation of the present invention.

FIG. 8 is a perspective view of an antenna of a comparative example with the present invention.

FIG. 9 is a diagram showing measurement results of input impedance of the antenna of the present invention.

FIG. 10 is a diagram showing measurement results of input impedance of an antenna of a comparative example.

FIG. 11 is a diagram showing measurement results of radiation directivity on a horizontal plane of the antenna of the present invention.

FIG. 12 is a diagram showing measurement results of radiation directivity on a vertical surface of the antenna of the present invention.

FIG. 13 is a diagram showing a measurement result of radiation directivity on a horizontal plane of an antenna of a comparative example.

FIG. 14 is a perspective view showing an example of a circular polarization patch array antenna of the present invention.

FIG. 15 is a perspective view showing another example of the circular polarization patch array antenna of the present invention.

FIG. 16 is a diagram showing an example in which the circularly polarized patch antenna of the present invention is applied to a wireless LAN constructed in a building, for example.

[Explanation of symbols]

11 Conductor plate 12 First patch antenna 13 Second patch antenna 14 First image current 15 Second image current

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01Q 21/24 H01Q 13/08

Claims (3)

(57) [Claims] 1. A ground conductor plate, and a first image current arranged on the first surface side of the ground conductor plate and adapted to flow a first image current corresponding to a supplied current in a predetermined rotation direction with respect to the ground conductor plate. 1 patch antenna, and a second image current arranged on the second surface side of the ground conductor plate for canceling the first image current with respect to the ground conductor plate according to the supplied current. A circularly polarized patch antenna comprising: a second patch antenna for feeding; and a power feeding means for feeding power to the first and second patch antennas. 2. A ground conductor plate, and a ground conductor plate arranged on the first surface side of the ground conductor plate, having a first width in a first direction different from the power feeding direction and different from the power feeding direction. A first patch antenna having a second width in the two directions and the first width being longer than the second width; and the first patch antenna on the second surface side of the ground conductor plate. Is arranged at a position facing the patch antenna, has the second width with respect to the first direction, has the first width with respect to the second direction, and has the first width. A circularly polarized patch antenna comprising: a second patch antenna having substantially the same shape as that of the patch antenna; and a feeding unit that feeds power to the first and second patch antennas. 3. A wireless communication system for transmitting and receiving data between a base station and a terminal via a wireless communication path, wherein the base station comprises a ground conductor plate and a first surface side of the ground conductor plate. A plurality of first patch antennas, which are arranged on the ground conductor plate and flow a first image current corresponding to the fed current in a predetermined rotation direction with respect to the ground conductor plate, and a second surface side of the ground conductor plate. Of the second patch antennas arranged at positions facing the respective first patch antennas of
A plurality of second patch antennas that flow the image current to the ground conductor plate so as to cancel each of the first image currents, and a power feeding unit that feeds power to the first and second patch antennas. A wireless communication system comprising a polarization patch array antenna.