JPH0380603A - Microstrip antenna - Google Patents

Abstract

PURPOSE:To obtain a desired resonance frequency even if the thickness or dielectric constant of a dielectric substrate or the diameter of a radiation conductor varies by forming a projection part or notch part at the outer peripheral edge part of the radiation conductor on the straight line connecting the center of the radiation conductor and a feed point. CONSTITUTION:The microstrip antenna which has the radiation conductor 13 and ground conductor 14 formed across the dielectric substrate 10 has the projection part 13a or notch part at the outer peripheral edge part of the radiation conductor 13 on the straight line connecting the center O of the radiation conductor 13 and the feed point P. Here, the resonance frequency is determined according to the size of the projection part 13 or notch part. Therefore, even if the thickness or dielectric constant of the dielectric substrate 10 or the diameter of the radiation conductor 13 varies owing to, for example, variance in manufacture, the resonance frequency can be adjusted by varying the size of the projection part 13a or cut part without varying the size of the radiation conductor 13. Consequently, even if the resonance frequency varies, a desired resonance frequency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microstrip antenna whose transmitting and receiving frequencies can be adjusted.

[Prior Art] FIG. 7 is a plan view of a conventional linearly polarized microstrip antenna.

In the linearly polarized microstrip antenna shown in FIG.
A circular radiation conductor 11 having a diameter R sufficiently shorter than one side of O is formed, and power is supplied to a position P shifted in the radial direction from the center O of the radiation conductor 11 via, for example, a coaxial cable.

Generally, the resonant frequency of this linearly polarized microstrip antenna is uniquely determined by the dielectric constant and thickness of the dielectric substrate 10 and the diameter R of the radiation conductor 11.

FIG. 8 is a plan view of a conventional fundamental mode circularly polarized microstrip antenna, and the same parts as in FIG. 7 are given the same reference numerals.

In the circularly polarized microstrip antenna shown in Fig. 8,
A dielectric substrate lO is placed in the center of the upper surface of a square dielectric substrate 10 with a ground conductor (not shown) formed on the lower surface.
A circular radiation conductor 12 having a diameter R sufficiently shorter than one side of the radiation conductor 12 is formed, and power is supplied to a position P shifted in the radial direction from the center O of the radiation conductor 12 via, for example, a coaxial cable.

Here, at the outer peripheral edge end of the radiation conductor 12 at a position at an angle of 45'' in a clockwise direction and at a position at an angle of 135° in a counterclockwise direction from the feeding point P, centering on the center 0 of the radiation conductor 12, Rectangular cutouts 12a and 12b are formed, and these cutouts 12a and 12b operate as mode degeneracy separation elements that emit circularly polarized radio waves.

In order to radiate circularly polarized radio waves from this microstrip antenna, it is desired that the value of the axial ratio, which is the ratio of the major axis to the minor axis of the circularly polarized wave, be close to 1, and the notch has the best axial ratio. The sizes of 12a and 12b are uniquely determined by the dielectric constant and thickness of the dielectric substrate 10, and the diameter R of the radiation conductor 12, and the frequency at which the axial ratio is the best is also determined by these three parameters. determined by

[Problems to be Solved by the Invention] In the conventional linearly polarized microstrip antenna described above, three parameters, the dielectric constant and thickness of the dielectric substrate 10, and the diameter R of the radiation conductor 11, are affected by manufacturing variations. If the microstrip antenna changes, there is a problem in that the resonant frequency of the microstrip antenna changes.

Further, in the above-described conventional circularly polarized microstrip antenna, there is a problem that, as in the case of linearly polarized waves, when the above three parameters change, the frequency at which the axial ratio is the best changes.

A first object of the present invention is to provide a linearly polarized microstrip antenna that has a desired resonant frequency even when the above three parameters change and the resonant frequency changes due to manufacturing variations, for example. be.

A second object of the present invention is to provide a circularly polarized microstrip antenna having a desired frequency even if the above three parameters change due to manufacturing variations and the frequency at which the axial ratio is the best changes. Our goal is to provide the following.

[Means for Solving the Problems 1] A linearly polarized microstrip antenna of the present invention is a microstrip antenna formed by forming a radiation conductor and a ground conductor via a dielectric substrate, in which the center of the radiation conductor and the feeding point are connected to each other. The radiation conductor is characterized in that a protrusion or a notch is formed at the outer peripheral edge of the radiation conductor on a straight line connecting the radiation conductor.

The circularly polarized microstrip antenna of the present invention is a microstrip antenna in which a radiation conductor and a ground conductor are formed via a dielectric substrate, in which the electromagnetic field generated between the radiation conductor and the ground conductor is in TMmn mode. , where m and n are natural numbers, and the outer peripheral edge of the radiating conductor at an angle of α-±45/m+90 N/m [' ] from the feeding point with the center of the radiating conductor as the center. At least one first protrusion or notch is formed at a position where the integer N is an even number, and at least one second protrusion or notch is formed at a position where the integer N is an odd number. It is characterized by the formation of

[Function 1] With the former configuration, a linearly polarized microstrip antenna having a predetermined resonant frequency can be obtained. Here, the resonance frequency is determined depending on the size of the protrusion or notch. Therefore, even if the thickness of the dielectric substrate, its relative dielectric constant, or the diameter of the radiation conductor change due to manufacturing variations, for example, the projections can be applied without changing the size of the radiation conductor. By changing the size of the portion or notch, the resonance frequency can be adjusted. For example, forming a radiating conductor in which the length of the protrusion is relatively long or a radiation conductor in which the length of the notch is relatively short, and cutting the protrusion so that the length of the protrusion becomes short; Alternatively, by further cutting the radiation conductor so that the length of the notch becomes longer, a linearly polarized microstrip antenna having a desired resonant frequency can be obtained.

In addition, by configuring the latter, the first and second protrusions or notches operate as mode degenerate separation elements, and a circularly polarized microstrip antenna having a predetermined frequency with the best axial ratio can be created. Obtainable. Here, the frequency at which the axial ratio is the best is determined according to the sizes of the first and second protrusions or notches. Therefore, even if the thickness of the dielectric substrate, its dielectric constant, or the diameter of the radiation conductor change due to manufacturing variations, the size of the radiation conductor remains unchanged. By changing the sizes of the first and second protrusions or notches, it is possible to adjust the frequency at which the axial ratio is the best. For example, forming a radiation conductor in which the length of the protrusion is relatively long and the length of the notch is relatively short, the protrusion is cut so that the length of the protrusion is short, and/ Alternatively, by further cutting the radiation conductor so that the length of the notch becomes longer, a circularly polarized microstrip antenna having a desired frequency with the best axial ratio can be obtained.

Note that the resonant frequency of this circularly polarized microstrip antenna can be adjusted, as is known, by connecting an impedance matching circuit to the feeding point and adjusting the frequency at which the above-mentioned axial ratio is the best.

[Example] Hereinafter, an example according to the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 is a plan view of a linearly polarized microstrip antenna according to the first embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view taken along line AA' in FIG. be.

In FIG. 1, a circular radiation conductor having a diameter R sufficiently shorter than one side of the dielectric substrate 10 is placed at the center of the upper surface of a square dielectric substrate 10 with a ground conductor 14 formed on the lower surface. 13 is formed, and the center conductor 21 of the power feeding coaxial cable 20 is connected to the radiation conductor 13 at a position P shifted in the radial direction from the center 0 of the radiation conductor 13,
A coaxial cable 20 is connected to the ground conductor 14 directly below the position P.
A ground conductor 22 is connected. Also, a straight line (hereinafter referred to as a base line BL) connecting the center O of the radiation conductor 13 and the feeding point P.

) on the outer peripheral edge of the radiation conductor 13, a rectangular protrusion 13a having a width W perpendicular to the base line BL and a length Q parallel to the base line BL is formed to protrude from the outer peripheral edge. be done.

Further, instead of the protrusion 13a, a rectangular cutout having a width W and a length Q is formed at the same position as the protrusion 13a.

Figure vg5 is a graph showing the frequency characteristics of the input end reflection coefficient S++ [dB] at the feeding point P of this linearly polarized microstrip antenna, and here, when the length Q is positive, the protrusion 13a is formed. A negative value indicates that a notch has been formed. Further, a glass-filled Teflon resin substrate is used as the dielectric substrate 10, and the thickness of the dielectric substrate 10 is 4 mm%, and the relative dielectric constant is 2.
．． 6. The diameter R of the radiation conductor 13 is 80 mm, and its thickness is 0.
．． 035 mm, the width W of the protrusion 13a and the notch is lom
It was m.

As shown in FIG. 5, when there is no protrusion 13a (12=
The resonant frequency of o) is approximately 1-305 GHz, and the resonant frequencies when the length α of the protrusion 13a is 5 mm and 2.5 mm are approximately 1.28 GHz and approximately 1.29 GH, respectively.
It is z. Further, when the length of the notch is 2.5 mm, the resonance frequency is approximately 1.315 GHz. Therefore,
The resonant frequency of the linearly polarized microstrip antenna is determined according to the length a of the protrusion 13a or the notch.

Therefore, the resonance frequency can be adjusted by changing the length Q of the protrusion 13a or notch without changing the diameter R of the radiation conductor 13. For example, the radiation conductor 13 having a relatively long length Q of the protrusion 13a or the radiation conductor 13 having a relatively short notch may be formed so that the length Q of the protrusion 13a is shortened. By cutting the radiating conductor 13 or further cutting the radiation conductor 13 so that the length of the notch becomes longer, a linearly polarized microstrip antenna having a desired resonant frequency can be obtained.

As explained above, for example, due to manufacturing variations, the thickness of the dielectric substrate 10, its relative permittivity, or the radiation conductor 13
Even if the diameter R of the protrusion 13a changes,
Alternatively, by changing the length α of the notch, the resonant frequency can be changed to obtain a linearly polarized microstrip antenna having a desired resonant frequency.

In the above first embodiment, the case where the electromagnetic field between the radiation conductor 13 and the ground conductor 10 is in the fundamental mode has been described, but the resonant frequency is not limited to this, and also applies to a microstrip antenna in a higher mode. Adjustments can be made as well.

In the above first embodiment, a case has been described in which the radiation conductor 13 has a circular shape, but the radiation conductor 13 is not limited to this, and may have any other shape such as a rectangle.

Second Embodiment FIG. 3 is a plan view of a circularly polarized microstrip antenna which is a second embodiment of the present invention, and FIG.
- It is a longitudinal cross-sectional view about the B' line. In FIGS. 3 and 4, the same parts as in FIGS. 1 and 2 are designated by the same reference numerals.

In FIG. 3, a circular radiation conductor having a diameter R sufficiently shorter than one side of the dielectric substrate 10 is placed at the center of the upper surface of a square dielectric substrate 10 on which a ground conductor 14 is formed on the lower surface. 15 is formed, and the center conductor 21 of the power feeding coaxial cable 20 is connected to the radiation conductor 15 at a position P shifted in the radial direction from the center O of the radiation conductor 15,
A coaxial cable 20 is connected to the ground conductor 14 directly below the position P.
A ground conductor 22 is connected. Also, 45° clockwise from the feeding point P with the center O of the radiation conductor 15 as the center.
and a radius W perpendicular to the radial direction of the radiating conductor 15 and a length parallel to the radial direction at each outer peripheral edge end of the radiating conductor 15 at an angle of 135° in the counterclockwise direction. Cutouts 15a and 15b having a length a2 are formed.

Furthermore, the radiation conductor 15 is located at a position at an angle of 45° in a counterclockwise direction from the feeding point P with the center O of the radiation conductor 15 as the center, and at a position at an angle of 135° in a clockwise direction from the feeding point P.
A width W perpendicular to the radial direction of the radiation conductor 15 and a length a parallel to the radial direction are provided at each outer peripheral edge end of the radiation conductor 15.

Projecting portions 15c and 15d are formed to protrude from the outer peripheral edge.

FIG. 6 is a graph showing the frequency characteristics of the axial ratio [dB] of this circularly polarized microstrip antenna, and shows the case where the radiation angle is Oe. Here, a glass-filled Teflon resin substrate is used as the dielectric substrate 10, the thickness of the dielectric substrate 10 is 4 mm, its relative dielectric constant is 2.6, the diameter R of the radiation conductor 15 is 64 mm, and its thickness is 0. .035mm,
The width W of the notches 15a, 15b and the protrusions 15c, 15d was 6 mm.

As shown in FIG. 6, when only the projections 15c and 15d are formed (CQr = 5 mm), the frequency when the axial ratio [dB] is closest to 0 and the axial ratio is the best is about 1. 548, and the notch 15a.

When only 15b is formed CQ, = 5 mm), the frequency when the axial ratio is best is about 1.571G
It is Hz. Furthermore, when notches 15a, 15b and projections 15c, 15d are both formed (L=2.5m
m, (h=3 mm), the frequency when the axial ratio is the best is about 1.565 GHz. Therefore, the notch 1
The frequency at which the axial ratio is the best is determined according to the length C2 of the projections 5a and 15b and the length Q of the projections 15c and 15d.

Therefore, without changing the diameter R of the radiation conductor 15, the length Q of the notches 15a, 15b and/or the projections 15c, 1
By changing the length Q of 5d, the frequency at which the axial ratio is the best can be adjusted.

For example, the projection 15c is shaped like a radiation conductor 15 in which the length Q□ of the projections 15c and 15d is relatively long and the length α of the notches 15a and 15b is relatively short.

The protrusion 15c is formed so that the length al of 15d is shortened.

By cutting 15d and/or further cutting the radiation conductor 15 so that the length α2 of the notches 15a and 15b becomes longer, a circularly polarized microstrip antenna having the desired frequency with the best axial ratio can be obtained. Obtainable.

As is well known, the resonant frequency of the circularly polarized microstrip antenna can be adjusted by connecting an impedance matching circuit to the feeding point of this antenna after the frequency adjustment of the above-mentioned axial ratio.

As explained above, for example, due to manufacturing variations, the thickness of the dielectric substrate 10, its relative permittivity, or the radiation conductor 15
Even if the diameter R of the notch 15a changes,
, 15b and/or the length 4 of the projections 15c, 15d, it is possible to obtain a circularly polarized microstrip antenna having a desired frequency with the best axial ratio.

In the above second embodiment, the case where the electromagnetic field between the radiation conductor 15 and the ground conductor 10 is in the fundamental mode has been described. Adjustments can be made in the same way.

Note that when the electromagnetic field between the radiation conductor 15 and the ground conductor lO is generally in the TMmn mode (m, n are as known,
It is a natural number. ), the notch and/or the protrusion are located on the radiation conductor 15 at an angle σ expressed by the following equation (1) in a clockwise direction from the feeding point P with the center ○ of the radiation conductor I5 as the center. Formed at the outer peripheral edge.

α-±45/m+9ON/m C” Co-(1
) Here, N is an integer, one or more notches or protrusions are formed at the above positions where N is an even number, and one or more notches or protrusions are formed at the above positions where N is an even number. is,
Therefore, a total of two or more notches and/or protrusions are formed.

In the above second embodiment, a case has been described in which the radiation conductor 15 has a circular shape, but the radiation conductor 15 is not limited to this, and may have any other shape such as a rectangle.

[Effects of the Invention] As detailed above, according to the present invention, in a microstrip antenna in which a radiation conductor and a ground conductor are formed via a dielectric substrate, a straight line connecting the center of the radiation conductor and a feeding point. Since a linearly polarized microstrip antenna is constructed by forming a protrusion or cutout on the outer peripheral edge of the radiation conductor, a predetermined resonant frequency can be set depending on the size of the protrusion or cutout. It is possible to obtain a linearly polarized microstrip antenna with . Therefore, even if the thickness of the dielectric substrate, its relative permittivity, or the diameter of the radiation conductor changes due to manufacturing variations, for example, the protrusion can be fixed without changing the size of the radiation conductor. Alternatively, there is an advantage that a linearly polarized microstrip antenna having a desired resonant frequency can be obtained by changing the size of the notch.

Further, in a microstrip antenna formed by forming a radiation conductor and a ground conductor via a dielectric substrate, an electromagnetic field generated between the radiation conductor and the ground conductor is in a TMmn mode, and the electromagnetic field is centered at the center of the radiation conductor. At least one first protrusion at the outer peripheral end of the radiation conductor at an angle of α-±45/m+90 N/m [' ] from the feeding point, and at a position where the integer N is an even number. forming at least one second projection or notch at a position where the integer N is an odd number;
Since the circularly polarized microstrip antenna is configured, it is possible to obtain a circularly polarized microstrip antenna having a predetermined resonant frequency that provides the best axial ratio according to the sizes of the first and second protrusions or notches. I can do it. Therefore, even if the thickness of the dielectric substrate, its dielectric constant, or the diameter of the radiation conductor changes due to manufacturing variations, the first
Another advantage is that a circularly polarized microstrip antenna having a desired resonant frequency can be obtained by changing the size of the second protrusion or notch.

[Brief explanation of drawings]

FIG. 1 is a plan view of a linearly polarized microstrip antenna according to the first embodiment of the present invention, and FIG.
Fig. 3 is a plan view of a circularly polarized microstrip antenna according to the second embodiment of the present invention; Fig. 4 is a longitudinal sectional view taken along line B-B' in Fig. 3. , Fig. 5 is a graph showing the frequency characteristics of the input end reflection coefficient Sll at the feeding point of the linearly polarized microstrip antenna of the first embodiment, and Fig. 6 is a graph showing the frequency characteristics of the circularly polarized microstrip antenna of the second embodiment. A graph showing the frequency characteristic of the axial ratio, FIG. 7 is a plan view of a conventional linearly polarized microstrip antenna, and FIG. 8 is a plan view of a conventional circularly polarized microstrip antenna. 10... Dielectric substrate, 13.15... Radiation conductor, 13a, 15c, 15d... Projection, 15a, 15b
- Notch, 0... Center of radiation conductor, P... Feeding point, α, Q, 12. ...Length of the protrusion or notch.

Claims (2)

[Claims] (1) In a microstrip antenna formed by forming a radiating conductor and a grounding conductor via a dielectric substrate, a protrusion is located on the straight line connecting the center of the radiating conductor and the feeding point at the outer peripheral edge of the radiating conductor. A linearly polarized microstrip antenna characterized by forming a section or a notch. (2) In a microstrip antenna formed by forming a radiation conductor and a ground conductor via a dielectric substrate, the electromagnetic field generated between the radiation conductor and the ground conductor is TM
mn mode, where m and n are natural numbers, and the outer peripheral edge of the radiation conductor is located at an angle of α=±45/m+90N/m [°] from the feed point with the center of the radiation conductor as the center. at least one first protrusion or notch is formed at a position where the integer N is an even number, and at least one second protrusion or notch is formed at a position where the integer N is an odd number. A circularly polarized microstrip antenna characterized in that a circularly polarized microstrip antenna is formed with a circularly polarized wave microstrip antenna.