JPH1022728A - Dual-frequency feed coupled circularly polarized antenna - Google Patents

Abstract

[PROBLEMS] To provide a dual-frequency feed coupling circularly polarized wave having a simple circuit configuration, suitable for miniaturization and cost reduction, and capable of exciting circularly polarized wave having good axial ratio characteristics. Provide an antenna. Kind Code: A1 Abstract: In a dual-frequency planar antenna in which two planar antennas having different resonance frequencies are formed on a dielectric substrate, the two planar antennas are stacked in a direction perpendicular to the dielectric substrate. It is characterized in that two or more feeding points in which the vector of the current distribution at the point is in the same direction are connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circularly polarized antenna.
For example, the present invention relates to a configuration of a circularly polarized antenna composed of two or more planar antennas having different resonance frequencies used in a mobile satellite communication device.

[0002]

2. Description of the Related Art When a transmission frequency and a reception frequency are assigned differently as in the case of satellite communication, an antenna used for the satellite communication must have a resonance frequency corresponding to each frequency of transmission and reception. Various dual frequency antennas have been proposed. Among them, a planar antenna having an advantage that it can be easily miniaturized and can be mounted on a moving body such as an automobile is disclosed in Japanese Unexamined Utility Model Publication No. 2-35514. And a dual-frequency planar antenna disclosed in Japanese Patent Application Laid-Open No. 5-175727.

[0003] The dual-frequency annular antenna disclosed in Japanese Utility Model Laid-Open No. 2-35514 has a problem that a diplexer is required when power is supplied for transmission and reception using the same power supply line, and miniaturization is difficult. As shown in FIGS. 11 (a) and 11 (b), the upper conductor plate 1, the lower conductor plate 2, and the conductor ground plate 3 are provided in order to separately provide power supply for transmission and reception, and to enhance isolation between the two antennas. Are arranged in parallel at regular intervals, and the conductor ring 4 is arranged between the lower conductor plate 2 and the conductor ground plate 3. The upper conductor plate 1 and the lower conductor plate 2 are each used for circularly polarized radiation. Phase-fed electrode feed line 5,
6, and each power supply line has four or more power supply lines. Further, the upper conductor plate 1 and the lower conductor plate 2
Are provided independently of the power distributor or the power combiner, as shown in FIG.

[0004]

However, the above-mentioned conventional dual-frequency antenna requires a hybrid circuit for power distribution or power combining, and has the problems that the cost is high and miniaturization is difficult. . On the other hand, the antenna disclosed in Japanese Patent Application Laid-Open No. HEI 5-175727 has two planar antennas having different resonance frequencies, which are separated from each other by a predetermined distance, and the two planar antennas are isolated from each other in order to ensure isolation between the two planar antennas. The feeding point of the circular antenna patch is relatively rotated by a predetermined angle. It also shows that two planar antennas may be provided so as to overlap in a direction perpendicular to the plane of the dielectric substrate. In this prior art, two feeder antennas are stacked and a hybrid circuit is used to radiate circularly polarized waves. The details of the feed point are not described. There has been a problem that polarization and left-handed circular polarization are generated, and the axial ratio is deteriorated. Therefore, the present invention provides a dual-frequency feed-coupled circle which has a simpler circuit configuration than conventional dual-frequency antennas, is suitable for miniaturization and cost reduction, and can excite circularly polarized waves having good axial ratio characteristics. It is an object to provide a polarized antenna.

[0005]

In order to solve the above-mentioned problems, a dual-frequency feed-coupled circularly polarized antenna according to a first aspect of the present invention comprises two planar antennas having different resonance frequencies from each other. In the dual-frequency planar antenna formed on the substrate, the two planar antennas are stacked in a direction perpendicular to the dielectric substrate, and extend horizontally from the center of each planar antenna to the outer periphery of the antenna. It is characterized in that the feeding points on the line are connected. The dual-frequency feed coupled circularly polarized antenna according to claim 2 of the present invention is the dual-frequency planar antenna, wherein two planar antennas having mutually different resonance frequencies are formed on a dielectric substrate. The antenna is provided at a predetermined distance from the dielectric substrate, and two or more feeding points having current distribution vectors in the same direction at the feeding points are coupled and coupled.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a dual-frequency feed-coupled circularly polarized antenna according to the present invention. First, prior to the description of the present invention, a brief description will be given of the deterioration of the axial ratio characteristics of the conventional dual-frequency circularly polarized antenna. FIG. 1A is a perspective view of a conventional dual-frequency feed-coupled circularly polarized antenna of a two-point feed type, and FIG.
3A and 3B are conceptual cross-sectional views of the antenna shown in FIG. 3A, wherein 10, 11, and 12 are dielectric substrates, 13 is a circular antenna patch provided on the dielectric substrate 10, and 14 is a dielectric substrate. The antenna patch 13 is provided between the feed points Q1 and Q2.
And the antenna patch 14 is connected to the feeding point Q3
And Q4.

FIG. 2 is a plan view of a hybrid circuit and a power supply line provided on the lower surface of the dielectric substrate 12, and FIG.
(4) A transmission line from the hybrid circuit 15 to the feeding points Q1 to Q4 via the microstrip line (strip line) is configured. In the figure, a two-partitioning and combining circuit using a transmission line is used. The transmission lines from the hybrid circuit 15 to the feeding points Q1 and Q2 are equal in length, and the transmission lines from the hybrid circuit 15 to the feeding points Q3 and Q4 are equal in length. Therefore, the signals supplied to the feeding points Q1 and Q2 have a phase difference of 90 °, and have equal amplitude, 90 ° through the feeding points Q1 and Q2.
By feeding the ゜ -phase signal to the antenna patch 13, a circularly polarized wave is excited from the antenna patch 13.
The relationship between the signals fed to the feeding points Q3 and Q4 is the same as above, and the antenna patch 14 also excites circularly polarized waves.

However, as shown in FIG. 3, the antenna having such a configuration has an axial ratio characteristic of about 5 dB, which makes it difficult to generate a good circularly polarized wave. The reason can be considered as follows. FIG. 4 (a) shows the case where the power supply point Q1 in the radiation conductor of the circular antenna patch 13 is zero.
9B shows a current distribution in the fundamental mode when excited at a phase of degree, and FIG. 9B shows a current distribution in the fundamental mode when excited at a phase of 0 degree at the feeding point Q3 in the radiation conductor of the annular antenna patch 14. FIG. 5 (a) shows the vector of the current component at each feeding point based on the concept of the current distribution in the basic mode and not using the two-distribution combining circuit. As is clear from this figure, at the feeding points Q1 and Q4, the vector of the Ey component is large, and the vector of the Hx component is at a level negligibly small as compared with the vector of the Ey component. Also at the feeding points Q2 and Q3, the Ex component vector is large and the Hy component vector is small.

Such a vector of the current component is generated at each feeding point. However, since this antenna uses a two-way splitting / combining circuit using a transmission line, it is taken into account by the vectors at the coupling points S1 and S2 shown in FIG. Then Figure 5
The result is as shown in FIG. That is, it can be seen that the ratio of the Ex component and the Hy component is smaller at the connection point S1 than before the connection, and the ratio of the Ey component and the Hx component is also smaller at the connection point S2 as well before the connection.
In order to generate a circularly polarized wave, a linearly polarized wave Ex polarized in the x-axis direction and a linearly polarized wave Ey polarized in the y-axis direction have a phase difference of ± 90 degrees, both propagating in the z-axis direction and having the same amplitude. When excited by the above, circular polarization occurs, but as described above, circular polarization is less likely to occur due to an increase in the ratio of the Hx or Hy component.

This can be expressed as a combination of left-handed circular polarization and right-handed circular polarization.
(Left-handed circularly polarized electric field strength), ER (right-handed circularly polarized electric field strength)
Then, the axial ratio AR can be expressed by the following equation. AR = (| EL | + | ER |) / (| EL |-| ER |) (1) In the above equation (1), as | AR | Since two linearly polarized waves E and H exist at the coupling points S1 and S2, for example, when used as a right-handed circularly polarized antenna, the cross-polarized wave (left-handed circularly polarized wave) also has the E component. Exists at the same energy as the ratio of the H component and the H component, and the axial ratio deteriorates. For example, even when used as a right-handed circularly polarized antenna in a mobile communication satellite system, a satellite or other system that receives left-handed circularly polarized In addition, there is a problem that an unnecessary signal is received by itself and the system is affected. Therefore, the following configuration is adopted as a dual-frequency feed-coupled circularly-polarized antenna that uses a two-combining distribution circuit and does not generate unnecessary cross polarization.

FIG. 6 is a diagram showing an embodiment of a dual-frequency feed-coupled circularly polarized antenna according to the present invention.
The same parts as those in FIG. The circular antenna patch 13 is provided on the dielectric substrate 10, and power is supplied from feeding points Q 1 and Q 2.
Is provided between the dielectric substrates 10 and 11, and the feeding point Q
Power is supplied from 3 and Q4. Further, the dielectric substrate 12
A transmission and hybrid circuit such as a microstrip line or a strip line for supplying power to the feeding points Q1 to Q4 is formed on the lower surface of the power supply point Q1.

FIG. 7 shows the configuration of a transmission line and a hybrid circuit using microstrip lines provided on the lower surface of the dielectric substrate 12, where O is a position corresponding to the center point of the circular and annular antenna patches, Reference numeral 15 denotes a 90-degree hybrid circuit, and reference numerals 16 and 17 denote transmission lines formed by strip lines, which constitute a two-division combining circuit. Note that the power supply point Q1
And the strip line length from the hybrid circuit 15 to the feeding point Q2 is equal, and similarly, the strip line length from the hybrid circuit 15 to the feeding point Q3 and the strip line length from the hybrid circuit 15 to the feeding point Q4 are equal. Further, the feeding points Q1 and Q3 are arranged on the same line L1 extending from the center O of the antenna to the outer periphery of the antenna, and the feeding points Q2 and Q4 are also arranged on the same line L2 orthogonal to the line L1. .

Considering the current distribution at the coupling points S3 and S4 when the feeding point is configured as described above, it can be expressed as shown in FIG. That is, the feeding points Q1 and Q
3 has a large Ey component and a small Hx component compared to the Ey component. Therefore, the vector of the current component at the connection point S3 between the feeding points Q1 and Q3 is a large Ey component. Synthesized, slight H
The x components are combined with each other, resulting in Ey >> Hx. The current components at the feeding points Q2 and Q4 are both large in the Ex component and the Hy component is small compared to the Ex, and the vector of the current component at the junction S4 between the feeding points Q2 and Q4 is a large Ex component. Are combined with each other, and slight Hy components are combined with each other, resulting in Ex >> Hy.

Thus, by forming the strip pattern of the two-distribution / combination circuit for supplying power from the hybrid circuit 15 to the feeding points Q1 to Q4, a linear polarization Ey polarized in the y-axis direction is provided at the coupling point S3. Exists and joins S4
Has a linearly polarized wave Ex polarized in the x-axis direction with a dominant magnitude. Therefore, by feeding the linearly polarized waves E and H to the feeding points Q1 and Q2 or Q3 and Q4 with equal amplitude and a phase difference of 90 ° through an external circuit such as a 90 ° hybrid circuit, cross polarization is achieved. No waves are generated, and a circularly polarized wave having good axial ratio characteristics can be excited.
FIG. 9 shows the axial ratio characteristics of the dual-frequency feed coupling circularly polarized antenna configured as described above. As is clear from the measurement results, it is understood that an improvement of about 4 dB is achieved as compared with the conventional antenna having the feeding point and the strip pattern configuration.

FIG. 10 is a view showing another embodiment of the dual-frequency feed coupling circularly polarized antenna according to the present invention.
In this embodiment, two circular antenna patches 22 and 24 having different resonance frequencies are arranged on a dielectric substrate 20. Although not shown, the circular antenna patch 22
And the feeding point Q3 of the circular antenna patch 24 are connected by the same feeding microstrip line via the connection point. Similarly, the circular antenna patch 22
And the feeding point Q4 of the circular antenna patch 24 are connected by the same feeding microstrip line via a connection point. That is, the vector of the current distribution at the feeding point Q1 provided on the circular antenna patch 22 is directed from the Q1 toward the center O of the antenna, while the vector of the current distribution at the feeding point Q3 provided on the circular antenna patch 24 is Since the antenna extends from Q3 toward the center P of the antenna, even if the feeding points Q1 and Q3 are coupled, linear polarization of the H component does not occur.

Further, the vectors of the current distribution at the feeding points Q2 and Q4 are also in the same direction.
, No linear polarization of the H component occurs. Therefore, it is possible to obtain circularly polarized waves without cross polarization. Although not shown, the transmission line length of the microstrip line from the hybrid circuit to the feeding points Q1 and Q2 of the circular antenna patch 22 is equal, and the feeding point Q of the circular antenna patch 24 from the hybrid circuit is equal.
Needless to say, the transmission line lengths of the microstrip lines up to 3, Q4 are equal.

[0017]

As described above, according to claim 1,
The dual-frequency feed-coupled circularly polarized antenna can make the current distribution vector at the connection point of the feed circuit in the same direction and reduce the occurrence of H-component linear polarization (cross-polarization). Axial ratio characteristics can be obtained. Further, the circuit configuration is simple and effective in providing an antenna at low cost. Also, the dual-frequency feed coupling circularly polarized antenna according to claim 2 can make the vector of the current distribution at the connection point of the feed circuit the same direction and reduce the generation of the H component linear polarization (cross polarization). Therefore, favorable axial ratio characteristics can be obtained over a wide angle. Further, the circuit configuration is simple and effective in providing an antenna at low cost.

[Brief description of the drawings]

FIG. 1 (a) is a perspective view of a conventional dual-frequency feed-coupled circularly polarized antenna of a two-point feed type, and FIG.
FIG. 2 is a conceptual cross-sectional view of a point-feed type dual-frequency feed coupled circularly polarized antenna.

FIG. 2 is a plan view of a hybrid circuit and a feed line provided on a lower surface of a dielectric substrate of a conventional dual-frequency feed-coupled circularly polarized antenna of a two-point feed type.

FIG. 3 is a diagram showing an axial ratio characteristic of a conventional dual-frequency feed coupled circularly polarized antenna.

4A is a diagram showing a current distribution in a fundamental mode when excited at a feeding point Q1 in a radiation antenna of a circular antenna patch at a phase of 0 degree, and FIG. 4B is a diagram showing a radiation conductor of a circular antenna patch; FIG. 7 is a diagram showing a current distribution in a basic mode when excitation is performed at a phase of 0 degrees at a feeding point Q3 in FIG.

5A is a diagram illustrating a current component vector at a feeding point, and FIG. 5B is a diagram illustrating a current component vector at coupling points S1 and S2.

FIG. 6 is a diagram showing an embodiment of a dual-frequency feed coupled circularly polarized antenna according to the present invention.

FIG. 7 is a diagram showing a configuration of a transmission line and a hybrid circuit of a dual-frequency feed coupling circularly polarized antenna according to the present invention.

FIG. 8 is a diagram showing current distribution at coupling points S3 and S4 of the dual-frequency feed coupling circularly polarized antenna according to the present invention.

FIG. 9 is a diagram showing an axial ratio characteristic of the dual-frequency feed coupling circularly polarized antenna according to the present invention.

FIG. 10 is a diagram showing another embodiment of the dual-frequency feed coupling circularly polarized antenna according to the present invention.

FIGS. 11A and 11B are views showing a dual-frequency annular antenna disclosed in Japanese Utility Model Laid-Open No. 2-35514.

FIG. 12 shows a structure disclosed in Japanese Utility Model Laid-Open Publication No. 2-35514.
The figure which shows the frequency shared annular antenna.

[Explanation of symbols]

 10, 11, 12: dielectric substrate, 13, 22, 24: circular antenna patch, 14: ring antenna patch, 15: 90 ° hybrid circuit, 16, 17: transmission line , O, P: antenna patch center, Q1, Q2, Q3, Q4: feeding point, S3, S4: coupling point.

Claims (2)

[Claims] 1. A dual-frequency planar antenna in which two planar antennas having different resonance frequencies are formed on a dielectric substrate, wherein the two planar antennas are stacked in a direction perpendicular to the dielectric substrate. A dual-frequency feed-coupled circularly polarized antenna, wherein two or more feed points having current distribution vectors in the same direction at the feed point are coupled. 2. A dual-frequency planar antenna having two planar antennas having different resonance frequencies formed on a dielectric substrate, wherein the two planar antennas are separated from the dielectric substrate by a predetermined distance from each other. A dual-frequency feed-coupled circularly polarized antenna, wherein two or more feed points having current distribution vectors at the feed points in the same direction are connected and coupled.