JP2000244231A - Micro-strip antenna and method for adjusting its resonance frequency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a micro-strip antenna small in size and excellent in directional gain. SOLUTION: A ground plate 7 and a feeder element 8 are laminated respectively on the backside and surface of a dielectric substrate 6. A parasitic element 10 is oppositely provided above the feeder element 8 through a gap 9. A slot hole 11 and a slit are provided in the center area of the parasitic element 10. When current (i) is excited on the parasitic element 10 with the connection of the feeder element 8 and the parasitic element 10, current (i) detours so that it avoids the slot hole 11 and the slit. Thus, a current route becomes long and the parasitic element 10 can be miniaturized. A back lobe becomes small and the micro-strip antenna excellent in directional gain can be realized. Then, a resonance frequency can easily be controlled by controlling the sizes of the slot hole 11 and the slit and the size of the feeder element 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip antenna, and more particularly, to a microstrip antenna which has a high degree of freedom for setting desired characteristics and which can be downsized.

[0002]

2. Description of the Related Art As a conventional microstrip antenna, there is one disclosed in Japanese Patent Application Laid-Open No. 10-154909. As shown in an exploded perspective view of FIG. 7A and a longitudinal sectional view of FIG. 7B, this conventional microstrip antenna includes a ground plate 2 called a ground conductor on the back and front surfaces of a dielectric substrate 1. A feed element 3 called a radiating element is formed by lamination, and a flat parasitic element 5 is provided above the feed element 3 with a gap 4 therebetween.

A power supply circuit or the like is connected to one end of the power supply element 3,
By exciting the current to the parasitic element 5 by coupling the feed element 3 and the parasitic element 5, it is used as a transmitting antenna, and by connecting a high-frequency amplifier or the like to one end of the feeding element 3, a receiving antenna is formed. It is used as

According to such a structure, the parasitic element 5 functions as a director for improving the gain, so that a high-gain antenna can be realized.

[0005]

However, when the above-mentioned conventional microstrip antenna is used as a resonance antenna, if the parasitic element 5 is used to improve the gain, it is necessary to reduce the size of the parasitic element 5. Since it cannot be performed, there is a problem that the microstrip antenna itself becomes large.

For example, if a microstrip antenna provided with the above-described conventional parasitic element 5 is applied to a communication device used in a satellite communication, a mobile communication system, or the like, there is a demand for miniaturization and portability of the communication device. With the ground plate 2
Cannot be increased. That is, the size of the main plate 2 is limited. When the size of the ground plane 2 is limited as described above, if the parasitic element 5 is reduced in order to reduce the size of the entire antenna, the back lobe of the antenna beam pattern increases, and the directional gain (directive gain) increases.
n) decreases. For this reason, it is difficult to reduce the size of the parasitic element 5 in a situation where the size of the ground plate 2 is limited, and it has been substantially difficult to reduce the size of the microstrip antenna.

When a weak signal such as a satellite wave is received, if the parasitic element 5 is made smaller in response to a demand for miniaturization, the effective noise temperature of the antenna increases as the back lobe increases. However, there has been a problem that the C / N becomes high and the C / N is reduced.

Further, as a general usage of the antenna, the antenna is often used by being housed in a radome. In this case, the resonance frequency of the antenna changes due to the influence of the radome, and it may not be possible to obtain a frequency characteristic that meets desired design specifications.

In particular, when the parasitic element 5 is provided, the number of constituent elements is increased as compared with the case where the parasitic element is not provided.
While taking into account the impact of adding
It becomes necessary to match the resonance frequency to a desired design specification. For this reason, there has been a problem that the difficulty in performing the optimum design and the fine adjustment is extremely high.

As described above, it has been a major problem to realize a microstrip antenna having desired characteristics and enabling downsizing while effectively utilizing the effect of the parasitic element 5.

The present invention has been made in view of the above-mentioned conventional problems, and provides a microstrip antenna capable of improving characteristics such as directivity gain, improving design flexibility, and miniaturizing. The purpose is to:

[0012]

To achieve the above object, the present invention provides a microstrip antenna in which a ground plane and a feed element are formed via a dielectric substrate, and a parasitic element is provided opposite to the feed element. In the above structure, a slot-shaped hole or a cut is formed in the parasitic element.

According to this structure, when power is supplied to the feed element, a current is excited on the parasitic element by coupling of the feed element and the parasitic element, and a radio wave is emitted from the parasitic element. In addition, since the excited current is bypassed so as to avoid a slot-like hole or cut, the current path becomes longer, and the size of the parasitic element and the size of the ground plane can be reduced. Further, when a slot-shaped hole or notch is provided, the back lobe of the antenna beam pattern becomes smaller as compared with a conventional microstrip antenna having no slot-shaped hole or notch, resulting in a microstrip having a good directivity gain. An antenna is realized. The resonance frequency can be easily adjusted by changing the size of the slot-like hole, the notch, and the size of the feed element.

Further, in the method of adjusting the resonance frequency of a microstrip antenna in which a ground plane and a feed element are formed via a dielectric substrate and a parasitic element facing the feed element is provided, a slot is provided in the parasitic element. A hole or cut is formed, and one or both of the size of the slot-shaped hole or cut and the size of the feed element are adjusted.

According to this adjustment method, a slot-shaped hole or notch is formed, and only one or both of the size of the slot-shaped hole or notch and the size of the power feeding element are adjusted. , A desired resonance frequency can be easily set. Thus, when the microstrip antenna of the present invention is used by being housed in a radome, even if the resonance frequency changes due to the influence of the radome, it can be easily adjusted to the target resonance frequency. Can be.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing the basic structure of the microstrip antenna of the present embodiment, and FIG. 2 is a characteristic diagram showing measured values of directivity gain.

An exploded perspective view shown in FIG. 1A and FIG.
In the vertical cross-sectional view shown in FIG. 1, the present microstrip antenna is formed by laminating a thin metal base plate 7 on the back surface of a dielectric substrate 6 and a thin metal feed element 8 on the surface of the dielectric substrate 6. The passive element 10 has a structure in which a parasitic element 10 is disposed above a space 8 via a gap 9.

A rectangular slot hole 11 is formed in the central region of the parasitic element 10.
The center of the feed element 8 and the center of the feed element 8 are aligned, and the feed element 8 and the parasitic element 10 are arranged to face each other.

Although not shown, a feed line formed integrally with the feed element 8 or a feed probe formed of a coaxial cable is connected to the ends (feed points) A and B of the feed element 8. I have. By connecting a power supply circuit or the like to these power supply lines or power supply probes, the power supply circuit or the like can be used as a transmission antenna, and a high-frequency amplifier circuit or the like for amplifying received radio waves is connected to these power supply lines or power supply probes. As a result, it can be used as a receiving antenna.

Next, the basic operation of the present microstrip antenna having such a structure will be described with reference to FIG.

When a high-frequency current is supplied to the feed element 8 by the above-described feed circuit or the like, a current is excited on the parasitic element 10 by coupling of the feed element 8 and the parasitic element 10, and a radio wave is emitted from the parasitic element 10. Is done. Here, as illustrated in FIG. 1C, the excited current i bypasses the rectangular slot hole 11 so that its current path becomes longer. Also, when a radio wave is received in response to a surrounding electromagnetic field, as shown in FIG.
Circumvents the rectangular slot hole 11 so that its current path becomes longer.

As described above, in the present microstrip antenna, the current path of the excitation current i is longer than that of the conventional parasitic element in which the slot hole 11 is not provided (see FIG. 7). Can be reduced in size.

That is, since the parasitic element 5 provided in the conventional microstrip antenna shown in FIGS. 7A and 7B has a flat plate shape with no slot hole formed therein, The current i excited on the feed element 5 is
As shown in FIG. 1D, the water flows straight.

Therefore, if the parasitic element 11 of the present embodiment and the conventional parasitic element 5 have the vertical and horizontal lengths (dimensions) e,
When f is equal, the parasitic element 11 of the present embodiment is
The current path of the excitation current i is longer than that of the conventional parasitic element 5.

As a result, the ground plate 7 has been
In the case of a microstrip antenna having a limited size, the current path is lengthened by the slot hole 7.
Since the vertical and horizontal lengths e and f of the parasitic element 11 can be reduced, a substantially small microstrip antenna can be realized.

Further, the directional gain of the present microstrip antenna will be described with reference to FIG. In the figure, the horizontal axis represents the azimuth angle (θ), and the vertical axis represents the gain (dB).
i) is shown, and the directional gain of the conventional microstrip antenna shown in FIG. 7 is indicated by a dotted line X, and the directional gain of the microstrip antenna of the present embodiment is indicated by a solid line Y. In order to compare the characteristics of the microstrip antenna of the present embodiment with those of the conventional microstrip antenna, the slot holes 11 are used.
The directivity gain was measured with only the presence or absence of the difference and the other structures being equal.

As is clear from FIG. 2, in the microstrip antenna of the present embodiment, the gain is azimuth angle θ.
It peaks at the main lobe at 0 ° and decreases almost monotonically as it goes to the side lobes and back lobes. As a result of the reduction of the back lobe, the directivity gain is improved, and the increase of the antenna noise temperature and the decrease of the C / N are suppressed.

On the other hand, the conventional microstrip antenna has an azimuth angle of θ = 90 ° or more and θ = −90 °.
Below, the back lobe increases. For this reason, the directivity gain decreases, the antenna noise temperature increases, and C /
N decreases.

As described above, according to the present embodiment, the provision of the slot hole in the parasitic element can suppress an increase in the back lobe, increase the antenna noise temperature and increase the C / N.
Can be suppressed.

Although the case where the rectangular slot hole 11 is provided in the parasitic element 10 has been described, as shown in FIGS. 3 (a) to 3 (c) corresponding to FIGS. 1 (a) to 1 (c). Alternatively, the cut 11 ′ may be formed in the parasitic element 10.

According to this structure, the current i excited in the parasitic element 10 bypasses the cut 11 'so that the current path becomes long. Therefore, similarly to the case where the slot hole 11 is formed, the parasitic element 10 can be reduced in size, and a small microstrip antenna can be realized. Further, since an increase in back lobe can be suppressed, an increase in antenna noise temperature and C /
N can be suppressed from decreasing.

FIGS. 4 and 5 show that the microstrip antenna of the present invention has the above-described structure, thereby improving the degree of freedom in design and the like.
This will be described with reference to FIG.

FIG. 4 is a diagram showing the structure of a linearly polarized square microstrip antenna, and FIG. 5 is a diagram showing the structure of a circularly polarized square microstrip antenna, corresponding to the microstrip antenna having the basic structure shown in FIG. Is shown.

In the plan view of FIG. 4 (a), the parasitic element 10 of the linearly polarized microstrip antenna has the outer vertical and horizontal lengths e and f, and the vertical and horizontal lengths of the slot hole 11. Are set to a and b. In the plan view of FIG. 4B, the vertical and horizontal lengths of the base plate 7 are set to g and h, and the vertical and horizontal lengths of the feed element 8 are set to c and d. In addition, as shown in the vertical cross-sectional view of FIG. 4C, the dielectric substrate 6, the feed element 8, and the parasitic element 10 are arranged symmetrically with respect to the ground plate 7.

The ground plate 7 is the largest, and the parasitic element 1
0, the feed element 8 has a smaller shape in this order.
The feed element 8 is larger than the slot hole 11.

The feeding point A is provided on a virtual center line in the vertical direction (y direction) and the horizontal direction (x direction) passing through the center Q of the feeding element 8 and orthogonal to each other.
A resonance frequency f _H resonating with horizontal polarization and a resonance frequency f _V resonating with vertical polarization occur at the feeding point B.

Here, the above-mentioned resonance frequencies f _H and f _V are determined depending on the dimensions a, b, c and d of the slot hole 11 and the feed element 8. When specific examples are listed, a relationship as shown in FIG. 6 is obtained. For example, if you are both square slot hole 11 and the feeding element 8, i.e., a = b, when the c = d, the resonance frequency f _H and f _V becomes f _H = f _V.

The slot hole 11 is rectangular, and the feed element 8
If it was a square, i.e., a> b, when the c = d, the resonance frequency f _H and f _V becomes f _H> f _V. Also, a
If <b, c = d, the resonance frequencies f _H and f _V are f _H <
the f _V.

FIG. 6 shows an example, and when the dimensions a, b, c, and d of the slot hole 11 and the feed element 8 are changed, the magnitude relationship between the resonance frequencies f _H and f _V is determined. The value of the resonance frequency can be adjusted.

Therefore, when the slot hole 11 is formed in the parasitic element 10 and the dimensions a, b, c, and d of the slot hole 11 and the feed element 8 are adjusted, the resonance frequencies f _H and f _V can be adjusted according to design specifications and the like. Fine adjustment can be made to the set desired value. In particular, the microstrip antenna is housed in the radome, and the resonance frequencies f _H and f _V are affected by the radome.
Is changed, the resonance frequencies f _H and f _V can be obtained simply by adjusting the dimensions a, b, c, and d of the slot hole 11 and the feed element 8.
Can be finely adjusted to a desired resonance frequency suitable for the purpose, and the degree of freedom in design can be greatly improved.

Next, the structure and features of the circularly polarized microstrip antenna will be described with reference to FIG.

In the plan view of FIG. 5 (a), the parasitic element 10 of the circularly polarized microstrip antenna has the outer vertical and horizontal lengths e and f, and the vertical and horizontal lengths of the slot hole 11. Are set to a and b, and cutouts (perturbations) 10a and 10b having the same shape are formed in the diagonal direction. In addition, in the plan view of FIG. 5B, the vertical and horizontal lengths of the base plate 7 are set to g and h, the vertical and horizontal lengths of the feed element 8 are set to c and d, and the diagonal direction is set. Thus, cutouts (perturbations) 8a and 8b having the same shape are formed.

Then, as shown in the vertical sectional view of FIG. 5C, the dielectric substrate 6, the feeding element 8 and the parasitic element 10 are arranged symmetrically with respect to the ground plate 7, and 7 is the largest, and has a smaller shape in the order of the parasitic element 10 and the feeding element 8, and the feeding element 8 is larger than the slot hole 11.

The feeding point A is provided on a virtual center line in the vertical direction (y direction) and the horizontal direction (x direction) passing through the center Q of the feeding element 8 and orthogonal to each other.
A resonance frequency f _H resonating with horizontal polarization and a resonance frequency f _V resonating with vertical polarization occur at the feeding point B.

As described above, the notches 10a, 10b, 8
a, 8b, and parasitic element 1 with respect to feeding points A, B
If the shapes of 1 and the feed element 8 are asymmetric, circularly polarized waves can be excited. When the dimensions a, b, c, and d of the slot hole 11 and the feed element 8 are changed, FIG.
In the same manner as shown in, it is possible to change the value of the resonant frequency and the magnitude relation between the resonance frequency f _H and f _V.

Therefore, when the present microstrip antenna is housed in the radome, and the resonance frequencies f _H and f _V are changed by the influence of the radome, the shapes of the slot hole 11 and the feed element 8 are simply adjusted. the resonance frequency f _H and f _V
Can be finely adjusted to a desired frequency suitable for the purpose, and the degree of freedom in design can be greatly improved.

In the circularly polarized microstrip antenna shown in FIGS. 5A to 5C, the slot hole 1
1 are in the range of 30 mm to 40 mm, the external dimensions e and f of the parasitic element 10 are 71 mm, respectively.
The outer dimensions c and d of the feed element 8 are 60 mm, the outer dimensions g and h of the ground plate 7 are 100 mm, the thickness of the dielectric substrate 6 is about 3 mm, and the gap 9 between the ground plate 7 and the parasitic element 10 is about 10 mm. When the dielectric substrate 6 is set to 12 mm and the dielectric substrate 6 is formed of a dielectric material having a relative dielectric constant εr of 2 to 3 such as glass epoxy, Teflon glass, ceramics, etc., the 1.5 GHz band in the mobile communication system conforming to the Radio Equipment Regulations. (L band), it is possible to realize a circularly polarized square microstrip antenna suitable for application to (L band).

In particular, when the slot hole 11 is not provided, the outer dimensions e and f of the parasitic element 10 need to be about 90 mm to realize a microstrip antenna having the same characteristics. On the other hand, according to the present embodiment, the outer dimensions e and f of the parasitic element 10 are each 71 m.
As a result, a small circularly polarized square microstrip antenna can be realized.

As described above, according to the present embodiment, since the slot hole 11 is formed in the parasitic element 10, a small-sized microstrip antenna can be realized in both the linear polarization type and the circular polarization type. In addition, the desired resonance frequency can be easily set only by adjusting the dimensions and shapes of the slot hole 11 and the feed element 8, so that the degree of freedom in design can be greatly improved.

In the microstrip antenna in which the cut 11 'is formed in the parasitic element 10 shown in FIG. 3, the desired resonance frequency can be easily adjusted by adjusting the size of the cut 11' and the size of the feed element 8. Can be set to

Although the rectangular microstrip antenna has been described, a circular microstrip antenna can be realized by making the dielectric substrate 6, and the feeding element 8 and the parasitic element 10 circular. By forming the slot holes in the circular parasitic element, it is possible to reduce the size, improve the directivity gain, and improve the design flexibility.

The shapes of the slot hole 11 and the cut 11 'and the shapes of the notches 8a, 8b, 10a and 10b may be changed to other shapes. In short, by providing the slot hole 11 and the cutout 11 ′ of an appropriate shape in the parasitic element 10, it is possible to improve the directivity gain and the degree of freedom in design with a small size.

[0053]

As described above, according to the present invention, since a slot-shaped hole or notch is provided in the parasitic element,
The current path of the current flowing on the parasitic element can be lengthened. For this reason, in the microstrip antenna in which the size of the ground plane is limited, the size of the parasitic element can be reduced, and as a result, a substantially small microstrip antenna can be realized.

Further, when a slot hole or the like is formed in the parasitic element as described above, the back lobe of the antenna beam pattern can be reduced, and as a result, a microstrip antenna having good directivity gain can be realized.

Further, by adjusting the size of the slot hole and the size of the feeding element, the resonance frequency can be easily fine-tuned. Therefore, when the resonance frequency is changed by the influence of the radome, the slot hole and the like are not changed. The degree of freedom in design can be greatly improved, for example, the resonance frequency can be finely adjusted to a desired resonance frequency suitable for the purpose only by adjusting the dimensions of the power supply element.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic structure of a microstrip antenna according to an embodiment.

FIG. 2 is a characteristic diagram showing characteristics of the microstrip antenna of the present embodiment.

FIG. 3 is a diagram showing a basic structure of a modified example of the microstrip antenna of the embodiment.

FIGS. 4A and 4B are a plan view and a vertical sectional view showing a structure of a linearly polarized microstrip antenna according to the present embodiment.

5A and 5B are a plan view and a longitudinal sectional view illustrating the structure of a circularly polarized microstrip antenna according to the present embodiment.

FIG. 6 is an explanatory diagram showing characteristics of linearly polarized and circularly polarized microstrip antennas.

FIG. 7 is an explanatory diagram showing a structure of a conventional microstrip antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 6 ... Dielectric element 7 ... Ground plate 8 ... Feeding element 9 ... Void 10 ... Parasitic element 11 ... Slot hole 11 '... Cut 8a, 8b, 10a, 10b ... Notch H, V ... Feeding point

Claims (5)

[Claims] 1. A microstrip antenna in which a ground plane and a feed element are formed via a dielectric substrate and a parasitic element facing the feed element is provided, wherein the parasitic element has a slot-shaped hole or notch. A microstrip antenna, which is formed. 2. The ground plane is larger than the feeding element and the parasitic element, the parasitic element is larger than the feeding element, and the feeding element is set to have a shape larger than the slot-like hole or notch. The microstrip antenna according to claim 1, wherein 3. The dielectric substrate, the ground plane, the feed element, the parasitic element, and the slot-shaped holes or cuts are all rectangular, and the relative permittivity of the dielectric substrate is in the range of 2 to 3. Value, the vertical and horizontal dimensions of the base plate are both about 100 mm,
Both the vertical and horizontal dimensions of the feed element are about 60 mm, the vertical and horizontal dimensions of the outer shape of the parasitic element are both about 71 mm, and the vertical and horizontal dimensions of the slot-shaped holes or cuts are set within a range of 30 mm to 40 mm, respectively. The microstrip antenna according to claim 1, wherein a thickness of the dielectric substrate is set to about 3 mm, and a distance between the ground plane and the parasitic element is set to about 12 mm. 4. The microstrip antenna according to claim 1, wherein the microstrip antenna is a linear polarization type or circular polarization type microstrip antenna. 5. A method for adjusting a resonance frequency of a microstrip antenna in which a ground plane and a feed element are formed via a dielectric substrate and a parasitic element facing the feed element is provided. The shape of the slot-shaped hole or notch, and the size of the slot-shaped hole or notch and the size of the feed element, or adjusting the size of both, the resonance frequency of the microstrip antenna characterized in that Adjustment method.