JP3825006B2 - Circularly polarized planar antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circularly polarized planar antenna for high-frequency wireless equipment, and more particularly to a circularly polarized planar antenna suitable for a plurality of microwave band ITS services (GPS, ETC, etc.) and wireless LAN.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-9538 [Patent Document 2]
Japanese Patent Laid-Open No. 2002-232227
As a car navigation system antenna mounted on a car that uses GPS (Global Positioning System), it is easy to communicate in an optimal state in any direction, and a thin and compact circularly polarized flat antenna is used. Yes. Recently, due to its characteristics (features), the range of use as an antenna for a wireless LAN access point has expanded.
[0004]
As shown in FIG. 9, this circularly polarized wave planar antenna usually has a dielectric ceramic 90 in which a radiation conductor 91 is formed on a ground conductor 93 on the surface of a wiring board 92. Two modes # 1 and # 2 whose polarizations are orthogonal to each other are excited independently. As shown in FIG. 9, the power feeding method is a method in which two orthogonal modes # 1 and # 2 are fed at one point from the same point, and as shown in FIG. There is a two-point power feeding system that feeds power from two different points using a phase adjuster such as 90 ° hybrid 104. In these circularly polarized flat antennas, in terms of characteristics, in addition to the frequency band, antenna gain, and impedance, axial ratio characteristics are regarded as important. It has been found that the cross-polarized component isolation becomes worse when the axial ratio characteristic is lowered.
[0005]
Although the flow of electronic devices is from miniaturization, weight reduction, and thinning, in the field of antennas, it is considered to change the dielectric constant of dielectric ceramics to a higher one or to make it a complicated radiation electrode shape. However, the current situation is that the characteristics are deteriorated. In particular, since the band characteristics and the axial ratio characteristics are remarkably lowered, it becomes unsuitable as a device such as a wireless LAN that requires a relatively wide band.
[0006]
[Problems to be solved by the invention]
The present invention provides a circularly polarized wave planar antenna that can be miniaturized while minimizing deterioration in characteristics as much as possible. In particular, the present invention provides a circularly polarized planar antenna that improves the axial ratio characteristics and enables a wide band.
[0007]
[Means for Solving the Problems]
That is, in a circularly polarized wave planar antenna in which a dielectric ceramic with a radiation electrode formed thereon is mounted on a wiring board on which a conductor pattern is formed, the radiation conductor has an annular conductor pattern, and the grounding conductor is formed on the surface of the wiring board. However, a 90 ° hybrid is formed on the back surface, and the conductor connected to the two adjacent points of the 90 ° hybrid is divided into four equal parts and the radiation electrode are capacitively coupled and fed. The conductor adjacent to the remaining two points of the 90 ° hybrid and the radiation electrode are capacitively coupled, and the conductors are connected to a grounded conductor pattern.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The concept of the circularly polarized flat antenna according to the present invention will be described with reference to FIG. A two-point power feeding method is employed in which a ring-shaped radiation conductor 32 is used and power is fed to two points A and B among points A, B, C, and D divided into four equal parts. The two feeding points A and B are capacitively coupled to the feeding conductor, connected to the 90 ° hybrid 34, and connected to an external circuit by a coaxial cable or the like. The remaining two points C and D are capacitively coupled to the conductor and grounded via the reactance element. By adding capacitive coupling means connected to the reactance element, the characteristics can be improved and the size can be reduced.
[0009]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a perspective view of the top and bottom surfaces, and FIG. 2 is a plan view, a bottom view, and side and front sectional views. On the surface of the dielectric ceramic 10, a rectangular ring-shaped radiation conductor 11 having a circumference of approximately one wavelength is formed and mounted on a ground conductor 13 formed on the surface of the wiring board 12. A 90 ° hybrid 14 is formed on the back surface of the wiring board 12 by a conductor pattern. This 90 ° hybrid is also formed so that its overall length is almost one wavelength.
[0010]
In the 90 ° hybrid, a conductor pattern is drawn inward from two adjacent points obtained by dividing the whole circumference into four equal parts, and is connected to a power feeding pin 15 disposed at a position corresponding to the power feeding point. The power feeding pin 15 is inserted into a hole formed in the dielectric ceramic 10 and arranged so that the tip thereof faces the radiation conductor 11. As a result, the feeding pin 15 is capacitively coupled to the radiation conductor 11. The 90 ° hybrid is connected to a coaxial cable (not shown) via an input / output connector 17 and connected to an external circuit. Further, it is connected to a grounded conductor pattern via a chip resistor 18.
[0011]
The mounting reactance pin 16 arranged near the remaining two points of the 90 ° hybrid divided into four parts is also inserted into the hole formed in the dielectric ceramics 10 in the same manner as the power feeding pin 15. The tip is arranged so as to face the radiation conductor 11. The shape of the loading reactance pin 16 may be the same as that of the power feeding pin. As a result, the loading reactance pin 16 and the radiation conductor 11 are also capacitively coupled. The mounting reactance pin 16 is connected to a grounded conductor pattern via a chip capacitor 19. This capacitance may be a capacitance obtained by a gap between the ground conductor pattern. Thereby, the connection structure shown in FIG. 3 is obtained.
[0012]
A circularly polarized wave planar antenna according to the present invention shown in FIGS. 1 and 2 was fabricated with a rectangular parallelepiped dielectric ceramic having a relative dielectric constant of about 8. The size of the dielectric ceramics was 20 mm in length and width, and the thickness was 6 mm. A radiating conductor having an outer side of 16 mm and an inner side of 8 mm was formed on the surface. At the center position of each linear portion of the ring-shaped radiation conductor, the feeding pin and the loading reactance pin inserted from the back face were opposed to each other at an interval of 1 mm. The power feeding pin and the loading reactance pin were connected as described above. For comparison, the device shown in FIG. 10 was fabricated by forming a 22 mm square radiation electrode on a 26 mm square dielectric ceramic. This is not the case where the feed pin is capacitively coupled, but directly connected to the feed conductor.
[0013]
5 and 6 show the antenna frequency vs. antenna maximum gain characteristics. FIG. 5 shows the characteristics of right-handed polarization and FIG. 6 shows the characteristics of left-handed polarization. In the figure, the solid line indicates the characteristic of the circularly polarized flat antenna according to the present invention, and the broken line indicates the characteristic of the conventional antenna. FIG. 7 shows frequency-to-axis ratio characteristics, and it can be seen that the circularly polarized flat antenna according to the present invention is greatly improved. As a result, an antenna that can be used in a wide frequency band can be obtained. FIG. 8 shows a vertical plane radiation pattern of a circularly polarized wave planar antenna according to the present invention, in which the solid line indicates right-handed polarization and the broken line indicates left-handed polarization.
[0014]
FIG. 4 is a perspective view showing another embodiment of the present invention. A power supply conductor 45 and a loaded reactance conductor 46 are formed on the surface of the dielectric ceramics 40 in place of the power supply pin and the loaded reactance pin shown in FIGS. Even in this case, the power supply conductor 45 and the loaded reactance conductor 46 are capacitively coupled to the radiation conductor 41. In this case, the conductor pattern drawn out from the 90 ° hybrid 44 is different in that it is formed outside. The loaded reactance conductor 46 has a structure in which a capacitance is obtained by a gap in the conductor pattern.
[0015]
The loaded reactance conductor according to the present invention can be terminated using not only a capacitor but also a reactance element such as a resistor or an inductor. Moreover, those reactance elements can also be obtained by a wiring board-like conductor pattern. Furthermore, the shape of the radiation conductor may be an annular shape. Note that the 90 ° hybrid acts as a phase adjuster, and other phase adjusters (circuits) may be used.
[0016]
【The invention's effect】
According to the present invention, it is possible to obtain a circularly polarized wave planar antenna that can be miniaturized while minimizing deterioration of characteristics as much as possible. In particular, it is possible to obtain a circularly polarized wave planar antenna having improved axial ratio characteristics and capable of widening the band.
[Brief description of the drawings]
1A is a front side view of an embodiment of the present invention, FIG. 2B is a rear perspective view thereof, FIG. 2A is a plan view of the embodiment of the present invention, and FIG. (C) is a front sectional view, (D) is a bottom view. FIG. 3 is an explanatory view of the concept of the present invention. FIG. 4 shows another embodiment of the present invention. Side perspective view [FIG. 5] Explanatory diagram of frequency vs. right-handed polarization antenna maximum gain characteristic of circularly polarized flat antenna according to the present invention [FIG. 6] Frequency of circularly polarized plane antenna according to the present invention vs. left-handed polarized antenna maximum gain FIG. 7 is an explanatory diagram of frequency-to-axis ratio characteristics of a circularly polarized flat antenna according to the present invention. FIG. 8 is an explanatory diagram of a vertical plane radiation pattern of the circularly polarized planar antenna according to the present invention. FIG. 10 is a perspective view of a conventional two-point feed planar antenna. FIG. 10A is a front side view, and FIG. View [Explanation of symbols]
10, 40, 90: Dielectric ceramics
11, 32, 41: Radiation conductor
12, 32, 92, 102: Wiring board
13, 93: Grounding conductor
14, 34, 44, 104: 90 ° hybrid
15: Power supply pin
45: Power supply conductor
16: Load reactance pin
46: Conductor for loading reactance
17: I / O connector
18: Chip resistance
19: Chip capacitor

Claims (4)

In a circularly polarized wave planar antenna in which a dielectric ceramic in which a radiation electrode is formed is mounted on a wiring board on which a conductor pattern is formed,
The radiation conductor consists of an annular conductor pattern,
A ground conductor is formed on the front surface of the wiring board, and a 90 ° hybrid is formed on the back surface. The conductor and radiation electrode connected to two adjacent points that divide the entire circumference of the 90 ° hybrid into four equal parts Combined and powered,
The conductor adjacent to the remaining two points of the 90 ° hybrid and the radiation electrode are capacitively coupled and the conductors are connected to a grounded conductor pattern.
A circularly polarized flat antenna characterized by that. In a circularly polarized wave planar antenna in which a dielectric ceramic in which a radiation electrode is formed is mounted on a wiring board on which a conductor pattern is formed,
The radiation conductor consists of an annular conductor pattern,
A grounding conductor is formed on the front surface of the wiring board, and a 90 ° hybrid is formed on the back surface. The tip of the power supply pin connected to two adjacent points that divide the entire circumference of the 90 ° hybrid into four equal parts and radiation The electrode is capacitively coupled and powered,
The loaded reactance pin and the radiation electrode adjacent to the remaining two points of the 90 ° hybrid are capacitively coupled and the loaded reactance pin is connected to the grounded conductor pattern via the reactance element.
A circularly polarized flat antenna characterized by that. In a circularly polarized wave planar antenna in which a dielectric ceramic in which a radiation electrode is formed is mounted on a wiring board on which a conductor pattern is formed,
The radiation conductor consists of an annular conductor pattern,
A grounding conductor is formed on the front surface of the wiring board, and a 90 ° hybrid is formed on the back surface. The 90 ° hybrid is formed on the surface of the dielectric ceramic by connecting it to two adjacent points that divide the entire circumference of the 90 ° hybrid into four equal parts. The power supply conductor tip and the radiation electrode are capacitively coupled and supplied with power,
The loaded reactance conductor and the radiation electrode formed on the surface of the dielectric ceramic adjacent to the remaining two points of the 90 ° hybrid are capacitively coupled, and the loaded reactance conductor is grounded via the reactance element. A circularly polarized flat antenna connected to a conductive pattern. The circularly polarized wave planar antenna according to claim 1, 2, or 3, wherein the radiation electrode has substantially one wavelength per circumference.

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