JP2002009538A - Planar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small-sized planar antenna that has excellent axial ratio characteristics over a wide frequency range. SOLUTION: The antenna having a feeding point at an impedance matching point of a radiation electrode in two axial directions formed on the surface of a dielectric board is mounted on a 2-layer wiring board provided with a 90 deg. phase adjusting circuit and ports. The 90 deg. phase adjusting circuit consisting of a closed conductor pattern, a port connected to the antenna drawn out to the inside and a port connected to a coaxial line are formed to the printed circuit board, and the 90 deg. phase adjusting circuit is contained to the rear side of the antenna.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circularly polarized planar antenna having a small size and excellent (low) axial ratio characteristics over a wide frequency range.
It is configured using a phase adjustment circuit (hereinafter referred to as a 90 ° hybrid).

[0002]

2. Description of the Related Art A conventional circularly polarized antenna using a dielectric planar antenna using a patch electrode mainly supplies power at one point, and the frequency range in which a good axis ratio is exhibited is narrow. GPS has a center frequency
1575.42MHz ± 1.023MHz frequency range with 0.13 fractional bandwidth
%, It is not necessary to widen the frequency range of the good axis ratio.
Therefore, there was no problem with the microstrip circularly polarized antenna fed by one point.

[0003] However, the frequency used for communication / broadcasting has become higher. For example, in a wireless LAN using the ISM band of 2450 MHz ± 50 MHz, the relative bandwidth becomes 4.1%, and
It is necessary to widen the frequency range.

Conventionally, a circularly polarized antenna using a 90 ° hybrid is rarely used for an application using only one element, and is arranged as shown in FIG. As shown in Fig. 10, the radiation electrode and the 90 ° hybrid are often configured on the same plane, and the 90 ° hybrid has a larger area than the radiation electrode patch. Was not suitable.

[0005]

SUMMARY OF THE INVENTION The present invention is not limited to a 2450 MHz band wireless LAN, but also a 5150 to 5250 MHz band wireless LAN.
And 5250-5350MHz wireless access, 5975-5845MHz band E
An object of the present invention is to provide a small circularly polarized plane antenna that can be used for communication requiring a good axis ratio over a wide band, such as TC and satellite digital broadcasting.

[0006]

According to the present invention, a dielectric planar antenna and a 90 ° hybrid are arranged one on top of the other, and a 90 ° hybrid is accommodated on the back surface of the dielectric planar antenna. It is intended to solve the problem. Further, by improving the connection structure between the 90 ° hybrid, the coaxial line, and the antenna, the characteristics are further improved.

That is, a dielectric planar antenna element having a feed point at each of 50Ω matching points on a line connecting the midpoints of opposing sides, using resonance modes in two orthogonal axes of a square conductor pattern on a dielectric substrate. 90 ° having two ports connected to respective feeding points connected to a closed conductor pattern of one wavelength and one wavelength, and two coaxial line connection ports connected to a transmission or reception circuit. In the planar antenna provided with the hybrid, the 90 ° hybrid is formed on a wiring board having two or more layers, and two ports connected to the feeding point are drawn inside the closed conductor pattern, and the ground pattern is closed. The conductor pattern formed around the conductor pattern and drawn inward is connected to the feed point of the dielectric planar antenna, and the port and the port of the closed conductor pattern are formed. Fine earth pattern are connected to the core wire and the external line of the coaxial line respectively, and it has the characteristics that the 90 ° hybrid is disposed on the rear surface of the dielectric plane antenna element.

A dielectric planar antenna element having a feed point at each of the 50Ω matching points on a line connecting the midpoints of the opposing sides, using resonance modes in two orthogonal directions of a square conductor pattern on a dielectric substrate; A 90 ° hybrid with two ports connected to each feed point connected to a closed conductor pattern of one wavelength and one wavelength and two coaxial line connection ports connected to a transmission or reception system circuit In the provided planar antenna, the 90 ° hybrid is
The two conductors formed on the substantially square wiring board and connected to the feeding point are drawn out inside the closed conductor pattern, the ground pattern is formed surrounding the closed conductor pattern, and the conductor drawn out inside is closed. The pattern is connected to the feeding point of the dielectric planar antenna, the port of the closed conductor pattern and the ground pattern are respectively connected to the coaxial lines at the corners of the wiring board, and the 90 ° hybrid is connected to the back surface of the dielectric planar antenna element. It is characterized by being arranged.

Further, a dielectric planar antenna element having a feed point at each of 50Ω matching points on a line connecting the midpoints of opposing sides, using resonance modes in two orthogonal directions of a square conductor pattern on a dielectric substrate. And two ports connected to the respective feeding points connected to a closed conductor pattern of one wavelength and one wavelength, and connected to a transmission or reception system circuit.
In a planar antenna provided with a 90 ° hybrid having two coaxial line connection-side ports, the 90 ° hybrid is formed on a square wiring board, and two ports connected to a feeding point have a closed conductor pattern. The wiring pattern is drawn inward from the corner position of the wiring board, the ground pattern is formed surrounding the closed conductor pattern, the conductor pattern of the port drawn out inward is connected to the feeding point of the dielectric planar antenna, and the closed The conductor pattern and the ground pattern are connected to the core wire and the outer wire of the coaxial line at the corners of the wiring board, respectively, and are not connected to the feeding point and the coaxial line.
The hybrid terminal is connected to an earth pattern via an impedance element formed of a conductor pattern formed on a wiring board, and is characterized in that a 90 ° hybrid is arranged on the back surface of a dielectric planar antenna element.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The components of a planar antenna according to the present invention are as follows. A dielectric planar antenna that consists of a square or circular patch and has a radiating electrode with two feed points at the biaxial matching points, a conductor on one side serves as the antenna ground electrode, and a 90 ° hybrid on the other surface And a two-layer wiring board on which a ground pattern surrounding them is formed, and a coaxial line connected to the 90 ° hybrid port and the ground pattern.

A structure in which a coaxial line is drawn out in a diagonal direction of the wiring board or a matching connection with a port not connected to a coaxial line or an antenna is realized by a pattern of the wiring board to further improve the characteristics. is there.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

1A and 1B show an embodiment of the present invention. FIG. 1A is a plan view and FIG. 1B is a front view. Antenna element 11 is 2450
For a 100 MHz bandwidth at a center frequency of MHz, the dielectric constant is 8
A 20 mm square patch 12 is formed on the surface of a 26 mm square dielectric substrate having a thickness of 6 mm. One feed pin is inserted into each of the two 50Ω points on the center line of the orthogonal sides of the patch, and consists of two independent microstrip antennas whose polarization axes in the X and Y directions are orthogonal. is there.

The wiring board 14 has a ground pattern on one side, except that a clearance is provided at the position of the feed pin of the antenna element, and a ground conductor for the antenna element. Power is supplied via a 90 ° hybrid described later, but connection to an external circuit is performed via a coaxial cable 17.

FIG. 2 is a plan view showing an example of the wiring board. 3 shows an example of a conductor pattern formed on one surface of a two-layer wiring board 24. FIG. One circumference is one wavelength, and the characteristic impedance is changed to 35.4Ω and 50Ω every 90 °.
A 90 ° hybrid conductor pattern 25 having a circular (diameter of about 22.4 mm) corner and a straight line between the corners is formed. These are surrounded by a ground pattern 26.

The inside of a pattern 25 closed from both ends of one 50Ω arm portion has a characteristic impedance of 50 ohms.
The conductor patterns 28 having the same length are drawn out. The conductor pattern 28 is formed up to a position corresponding to the feeding point of the antenna element, and is connected to the radiation electrode with a pin.

One of both ends of the other 50Ω arm is connected to a coaxial line (not shown) with a characteristic impedance of 50 ohms. That is, one end of the 50Ω arm is connected to the core of the coaxial line, and the ground pattern is connected to the outer line of the coaxial line.
The other end is connected to the ground pattern 26 also with a matching impedance of 50Ω. Usually, a chip resistor is soldered to a predetermined impedance.
The ground pattern 26 is connected to the entire ground pattern on the opposing surface by through holes or the like.

The good axis ratio-frequency characteristic of the two-point feeding circularly polarized antenna is good for the following reason. The square radiation pattern resonates as two orthogonal antennas in the X and Y directions. At frequencies near the center frequency, the received power induced by the X direction resonance and the Y direction induced resonance with respect to the circularly polarized wave. The received powers are equal, and the axis ratio, which expresses the ratio between the two in decibels, shows a low good value. There is a 50Ω feed point on the vertical line at the center of each side of X and Y to extract the reception output
When the output of a two-point feeding microstrip antenna is combined with a 90 ° hybrid of two input ports and two output ports,
A right-handed polarization output is obtained at one end of the output port, and a left-handed polarization output is obtained at the other end.

Using the wiring substrate shown in FIG.
Figure 3 shows the axial ratio for each radiation angle at the end of the frequency bandwidth and the axial ratio for each radiation angle at the center frequency when a coaxial cable is connected to the center of the 24 side and pulled out from the center as it is. . In other words, this is a case where the core wire of the coaxial wire is drawn out in the direction perpendicular to the side at the position of the center line of the side. The longer the rod length, the worse the axial ratio. In this case, the axial ratio is not sufficient.

FIG. 4 shows the characteristics when the connection position of the coaxial line to the arm is the same as that in the example shown in FIG. 2 and the position to be pulled out to the outside is the diagonal direction of the wiring board. in this way,
The axial ratio can be improved simply by changing the drawing direction.

FIG. 5 is a plan view showing another embodiment of the present invention, in which the shape of a 90 ° hybrid is changed. In this example, the 90 ° hybrid pattern 55 is arranged so that the connection point of the arm is located on the diagonal line of the square wiring board, and from the both ends of the 50Ω arm to the position corresponding to the feeding point of the antenna element inside from both ends of the 50Ω arm. Conductor patterns of equal length
58 are formed.

FIG. 6 shows a connection structure between the 90 ° hybrid and the coaxial line shown in FIG. 5. The core of the coaxial line 67 is connected to a pattern drawn outward from the connection point of the 90 ° hybrid pattern 65. , And an external line is connected to the ground pattern 66. In this manner, the size of the ground plate becomes equal in the X direction and the Y direction by being pulled out at the corners, and as a result, the axial ratio-frequency range is expanded.

The size of the antenna element is determined by the dielectric constant of the dielectric antenna element, and the size of the 90 ° hybrid pattern is determined by the dielectric constant of the wiring board. Effectively reduces the permittivity of the wiring board to 40% to 130% of the permittivity of the antenna element board
By doing so, a 90 ° hybrid pattern can be accommodated on the back surface of the antenna element.

The input ports of the 90 ° hybrid are connected to the feed points of the antennas which are orthogonal to each other, but usually only one port pair is connected to the receiving or transmitting circuit. If the unused port is left open, as shown in FIG. 7, the axial ratio is good at the center frequency, but at ± 50 MHz, the matching is greatly disturbed and the characteristics deteriorate. If this is matched with 50Ω, the axial ratio becomes good over a wide band as shown in FIG.

When a resistor is connected for matching, a mounting process is required, and solder printing-mounting-
A reflow process will be added. If this can be replaced with a conductor pattern that gives an impedance of 50Ω at the frequency used, the number of manufacturing steps can be reduced.

Therefore, it is conceivable that a meandering conductor pattern is formed at the time of forming a 90 ° hybrid. For example, to obtain 50Ω at 2.45 GHz, an inductance of 3.3 nH may be formed from the relationship of L = Z / (2πf). FIG. 9 shows an example in which a meandering conductor pattern 99 is formed between a 90 ° hybrid connection point and a ground pattern.

Although the above description has been made using the example of a square antenna element, the antenna element may be circular. Further, the wiring board constituting the 90 ° hybrid may have a triplate structure using three or more layers. Note that a microstrip line opposite to the partial ground conductor may be used instead of the coaxial line, and the microstrip line may be connected to the hybrid port.

[0028]

According to the present invention, on the back surface of the antenna element,
Since a 90 ° hybrid can be accommodated, a very small planar antenna can be obtained.

Further, by setting the coaxial line extending direction to the diagonal direction of the wiring board, a good axial ratio can be obtained over a wide frequency band, and a plane suitable for communication requiring a wide range of a good axial ratio. An antenna is obtained.

Furthermore, since the impedance for obtaining the matching can be formed integrally and simultaneously with the 90 ° hybrid, a planar antenna with a small number of manufacturing steps and high reliability can be obtained.

[Brief description of the drawings]

FIG. 1A is a plan view showing an embodiment of the present invention,
(B) is a front view

FIG. 2 is a plan view of an example of a wiring board used in the present invention.

FIG. 3 is an explanatory diagram of characteristics of the planar antenna according to the present invention.

FIG. 4 is an explanatory diagram of characteristics of the planar antenna according to the present invention.

FIG. 5 is a plan view of an example of a wiring board used in the present invention.

FIG. 6 is a partial plan view of an embodiment of the present invention.

FIG. 7 is an explanatory diagram of characteristics of the planar antenna according to the present invention.

FIG. 8 is an explanatory diagram of characteristics of the planar antenna according to the present invention.

FIG. 9 is a partial plan view of an embodiment of the present invention.

FIG. 10 is a plan view of a conventional planar antenna.

FIG. 11 is a plan view of a conventional planar antenna.

[Explanation of symbols]

 11: Antenna element 14, 24: Wiring board 25, 55, 65: 90 ° hybrid 26, 66: Earth pattern 17, 67: Coaxial line

Claims (11)

[Claims] 1. A dielectric planar antenna element having a feed point at each of 50Ω matching points on a line connecting midpoints of opposing sides, using resonance modes in two orthogonal directions of a square conductor pattern on a dielectric substrate. 90 ° having two ports connected to respective power supply points connected to a closed conductor pattern of one wavelength and one wavelength, and two coaxial line connection ports connected to a transmission or reception system circuit. In the planar antenna provided with the hybrid, the 90 ° hybrid is formed on a wiring board having two or more layers, and two ports connected to the feed point are drawn out of the conductor pattern in which the port is closed, and the ground pattern is closed. The conductor pattern formed around the pattern and drawn inward is connected to a feeding point of the dielectric planar antenna, and the port of the closed conductor pattern and the ground are provided. Turn is connected to the core wire and the external line of the coaxial line respectively, a planar antenna, characterized in that the 90 ° hybrid is disposed on the rear surface of the dielectric plane antenna element. 2. The wiring board according to claim 1, wherein the wiring board is a two-layer wiring board.
2. The planar antenna according to claim 1, wherein the back surface of the surface on which the 0 ° hybrid is formed serves as a ground conductor of the dielectric planar antenna element. 3. The planar antenna according to claim 1, wherein the dielectric constant of the wiring substrate is 40% to 130% of the dielectric constant of the dielectric of the dielectric planar antenna element. 4. A dielectric planar antenna element having a feed point at each of 50Ω matching points on a line connecting midpoints of opposing sides using resonance modes in two orthogonal axes of a square conductor pattern on a dielectric substrate. 90 ° having two ports connected to respective power supply points connected to a closed conductor pattern of one wavelength and one wavelength, and two coaxial line connection ports connected to a transmission or reception system circuit. In the planar antenna provided with the hybrid, the 90 ° hybrid is formed on a substantially square wiring board, and two ports connected to the feeding point are drawn out of the closed conductor pattern, and the ground pattern is closed. And the conductor pattern drawn inward is connected to the feeding point of the dielectric planar antenna, and the port and the electrode of the closed conductor pattern are formed. Scan pattern is connected to the coaxial line at a position of the corner of each wiring board, the planar antenna, characterized in that the 90 ° hybrid is disposed on the rear surface of the dielectric plane antenna element. 5. A dielectric planar antenna element having a feeding point at each of 50Ω matching points on a line connecting the midpoints of opposing sides, using resonance modes in two orthogonal axes of a square conductor pattern on a dielectric substrate. 90 ° having two ports connected to respective power supply points connected to a closed conductor pattern of one wavelength and one wavelength, and two coaxial line connection ports connected to a transmission or reception system circuit. In the planar antenna provided with the hybrid, the 90 ° hybrid is formed on a substantially square wiring board, and two ports connected to the feeding point are drawn inward from corners of the wiring board of the closed conductor pattern,
An earth pattern is formed surrounding the closed conductor pattern, the conductor pattern of the port drawn inward is connected to the feeding point of the dielectric planar antenna, and the conductor pattern and the earth pattern of the closed port are respectively connected to the wiring board. A planar antenna, wherein the 90 ° hybrid is connected to a core wire and an outer wire of a coaxial wire at a corner position, and the 90 ° hybrid is arranged on a back surface of the dielectric planar antenna element. 6. The wiring board is a two-layer wiring board.
The planar antenna according to claim 4 or 5, wherein the back surface of the surface on which the 0 ° hybrid is formed serves as a ground conductor of the dielectric planar antenna element. 7. The planar antenna according to claim 4, wherein a dielectric constant of the wiring board is 40% to 130% of a dielectric constant of the dielectric of the dielectric planar antenna element. 8. A dielectric planar antenna element having a feed point at each of 50Ω matching points on a line connecting midpoints of opposing sides, using resonance modes in a biaxial direction orthogonal to a square conductor pattern on a dielectric substrate. 90 ° having two ports connected to respective power supply points connected to a closed conductor pattern of one wavelength and one wavelength, and two coaxial line connection ports connected to a transmission or reception system circuit. In the planar antenna provided with the hybrid, the 90 ° hybrid is formed on a square wiring board, and two ports connected to the feeding point are drawn inward from corners of the wiring board of the closed conductor pattern, and grounded. A pattern is formed surrounding the closed conductor pattern, and the conductor pattern of the port drawn inward is connected to a feed point of the dielectric planar antenna, and the closed conductor The pattern and the ground pattern are connected to the core wire and the outer wire of the coaxial line at the corner positions of the wiring board, respectively, and the power supply point, the terminal of the 90 ° hybrid not connected to the coaxial line, is an impedance element formed by a conductor pattern formed on the wiring board. Wherein the 90 ° hybrid is disposed on the back surface of the dielectric planar antenna element via a ground pattern. 9. The planar antenna according to claim 8, wherein the impedance element is an inductance element. 10. The wiring board is a two-layer wiring board,
9. The planar antenna according to claim 8, wherein the back surface of the surface on which the 90 ° hybrid is formed serves as a ground conductor of the dielectric planar antenna element. 11. The planar antenna according to claim 8, wherein the dielectric constant of the wiring board is 40% to 130% of the dielectric constant of the dielectric of the dielectric planar antenna element.