JPH0629723A - Plane antenna - Google Patents

Abstract

PURPOSE:To extend the radiation band of a radiating element with a relatively simple and economical constitution and to improve the compatibility between the radiating element and a feeder with respect to the plane antenna used as an antenna for satellite broadcast reception or satellite communication, an antenna for general communication or a radar, an antenna of a single element having a wide-angle directivity for mobile communication, etc. CONSTITUTION:The Q value of an MSA radiating element 3 is reduced to extend the band of matching to a feed line 5 by the simple structure where an outer high-dielectric constant dielectric layer 7 and an inner low-dielectric constant dielectric layer 7' whose thickness is 1/4 effective wavelength are laminated on the radiating element 3, and the band of the axial ratio indicating the circular polarization characteristic is extended in the case of a circularly polarized wave radiating element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna for satellite broadcasting reception or satellite communication, an antenna used for general communication or radar, and a single element having wide-angle directivity for mobile communication. The present invention relates to a planar antenna that is also used as an antenna or the like.

[0002]

2. Description of the Related Art For example, a microstrip radiating element (M
In the case of a planar antenna using multiple SA radiating elements,
The radiating element is generally arranged on a substrate having a limited thickness so that an unnecessary propagation mode does not occur in the feed line. However, in this case, since the radiation band of the radiation element alone is narrowed, there is a problem that the application range is limited to some extent.

Therefore, as a means for widening the band of a conventional planar antenna, there is a method of disposing and coupling a parasitic radiating patch element above the MSA radiating element, or adding a wide band matching circuit to the feed line. However, the use of such a conventional band broadening means has a drawback that the configuration of the antenna device becomes complicated and the design becomes troublesome.

On the other hand, as a structure of a planar antenna that has been practically used in the past, there is an outer cover for protecting the antenna element, and a foamed dielectric layer is provided between the cover and the radiating element. .

Here, regarding the electrical characteristics of the antenna cover, the thickness of the foamed dielectric is adjusted in the experimental stage to minimize the loss of antenna gain due to the addition of the dielectric cover. In addition, as a conventional method for designing such a dielectric cover or radome, a dielectric layer having a small thickness or a material having a small dielectric constant is used, or the thickness of the dielectric layer is reduced by half. The wavelength is set.

In this case, the thickness of the dielectric layer is halved.
When the effective wavelength is set, resonance occurs in the dielectric layer in the thickness direction with respect to electromagnetic waves passing therethrough, and a frequency at which radio waves are easily transmitted is obtained, and reflected waves from the front and back surfaces of the dielectric layer are incident in the direction of radio waves. Will be offset against. In addition,
The thickness of the dielectric layer may be adjusted to some extent to correct the mismatch remaining in the antenna system.

[0007] Further, conventionally, in an antenna prototyped for the purpose of changing the directivity, a means of adding a dielectric material to the upper part of the MSA radiating element has been attempted, which may increase the gain to some extent. Are known.

[0008]

That is, in the above-mentioned conventional planar antenna, there is no band broadening means having a simple structure,
Further, in order to improve durability and characteristics, a dielectric material is used in various methods, but in any of them, there is a problem that the dielectric material cannot be used as an effective band widening means. .

In addition, the MSA in the conventional planar antenna
The radiating element has a radiation resistance of about 200 ohms when viewed from the open end, and the characteristic impedance (equation 1
Since it is larger than 0 ohm), there is a problem that the matching is poor such that an impedance conversion means is required for connection between the two.

The present invention has been made in view of the above problems,
It is an object of the present invention to provide a planar antenna capable of widening the radiation band of a radiating element with a relatively simple and economical structure and improving the matching between the radiating element and a feed line.

[0011]

That is, in the planar antenna according to the present invention, first, considering the operation of the MSA radiating element, since the MSA radiating element behaves as a resonance circuit during excitation, the excitation electromagnetic energy of the radiating element is Are mostly confined and only some are radiated into free space. Looking at this radiating element as an equivalent circuit, it consists of a radiative conductance component (reciprocal of radiation resistance) that radiates energy and a susceptance component that accumulates energy. The antenna Q value obtained by dividing the latter susceptance component by the former conductance component is , Usually about 20 to 30. The radiation bandwidth of the antenna is inversely proportional to the Q value.

Next, considering the electromagnetic radiation by the MSA radiation element, the magnitude of the radiation conductance component is
It is proportional to the square of the current flowing through the MSA radiating element and proportional to the impedance of free space.

Therefore, by providing the MSA with a plurality of impedance conversion dielectric layers having a quarter effective wavelength thickness, arranging a high dielectric constant dielectric layer on the outside and a low dielectric constant layer or an air layer on the inside. The radiated power is increased by increasing the input impedance of the space viewed from the outside of the radiating element. The above arrangement is an operation in which the impedance is temporarily lowered by the outer high dielectric constant layer, and then the impedance is inverted by the inner low dielectric constant layer, and the object can be achieved.

By doing so, the impedance conversion action of the dielectric layer is maximized, and the apparent free space impedance seen from the radiating element is increased by a multiple of the relative permittivity of the material, and the radiative conductance is increased at that rate. be able to. This can be interpreted as an increase in the electric power emitted from the excited MSA current to the space by increasing the impedance on the free space side.

Under the above operating conditions, when the dielectric layer alone is viewed, the reflected waves from both the front and back surfaces of the dielectric layer with respect to the incident wave are added and increased, and the electromagnetic wave is the most difficult to pass through and the anti-reflection in the thickness direction is caused. It is a resonance point. This is in contrast to conventional radome design concepts.

However, in the planar antenna of the present invention, the reflected wave with respect to the incident wave is canceled by combining with the reflected wave of the antenna element alone, so that there is no reflection loss as a whole and reactive reflection is originally provided. Therefore, the passing loss is small enough to be neglected, and the desired wide band can be achieved.

When the above-mentioned means for adding the dielectric layer is used, on the other hand, the energy stored as capacitance in the MSA radiating element is somewhat increased, but the amount of increase is relatively small. This is because the capacitance of the MSA radiating element is mainly made of the dielectric between the ground conductor and the MSA radiating element conductor. Therefore, the antenna Q value obtained by dividing the susceptance component by the radiation conductance component can be reduced at a rate close to the factor of the relative permittivity of the dielectric layer serving as the impedance conversion layer, so that the intended wide band can be achieved. Become.

Also, by means of adding a dielectric layer having a thickness of a quarter effective wavelength of the propagating electromagnetic wave, the excessive radiation resistance value of the MSA radiating element, which has been a problem in the past, can be reduced and optimized, The matching with the characteristic impedance of the feeder line can be improved at the same time.

In the antenna device of the present invention, by using a dielectric material having a relative dielectric constant value of 2, for example,
The bandwidth can be increased to approximately double, and the bandwidth can be further increased by selecting a dielectric material.

That is, in the planar antenna of the present invention, M
In order to positively utilize the dielectric layer arranged above the SA radiating element for impedance conversion, the dielectric material uses a non-foamed material or a material with a low foaming rate or a composite material thereof, and the thickness per layer is Is selected to be a quarter effective wavelength as a whole.

In this case, when a dielectric layer having a thickness of the above design conditions is used, unlike the conventional dielectric loading condition,
The change in the value of the radiation conductance exhibited by the original radiation element is maximized depending on the presence or absence of the dielectric layer. Therefore, the feeding circuit in this planar antenna is designed to match the radiation conductance increased by adding the dielectric.

On the other hand, even when the radiating element is a slot or another type, by interposing a plurality of dielectric layers having a quarter effective wavelength between the radiating element and the free space,
The apparent free space impedance is converted into the maximum value, and the band can be widened by the same principle as described above.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the structure of a MSA single patch coaxial feed type planar antenna. An MSA (microstrip antenna) is provided on the ground conductor plate 1 with a disc-shaped conductor plate 3 arranged at an interval via a dielectric 2.
4 are configured.

The disc conductor plate 3 is selected in such a size that its resonance frequency matches the operating frequency, and the feeder line 5 for excitation is used.
The connection point with and is set as a matching point.
The coaxial connector 6 is connected in correspondence with. Impedance conversion resin dielectric layers 7 and 7'having a thickness set to 1/4 effective wavelength are laminated and attached to the upper portion of the MSA 4. Here, the relationship between the relative permittivity ε _{ri of the} dielectric layers 7 and _{7'and the} thickness d _i (i = 1,2) is as follows: d ₁ = λ _g1 / 4, d ₂ = λ _g2 / 4 In addition, λ _gi = λ ₀ / RT (ε _ri ), RT () is set to a range in which a square root is multiplied, where λ _{0 is a} free space wavelength.

On the other hand, MSA with free space on the outside
The radiative conductance G of 4 is defined as the power radiated from the MSA 4 to the free space when a unit voltage is applied to the open end of the MSA 4, and is generally G = k · η · I ² It is known that the relational expression: (k is a constant) holds. Where I
Is the maximum amplitude of the current flowing through MSA4. Further, η is a wave impedance in free space.

Therefore, in the present embodiment, in order to effectively increase η in the above equation, the impedance-converting resin dielectric layers 7 and 7'having a quarter effective wavelength are laminated on the disk conductor 3 respectively. To do.

That is, in the case of the MSA 4 in this embodiment, the input impedance Zeff of the space seen from the outside of the MSA 4 has an electric field parallel to the dielectric layers 7 and 7'and an electromagnetic wave propagating in the thickness direction thereof. , Zeff = Z ₀₂ ² is the same principle as the operation of the impedance converter constituted by the two-stage lines having characteristic impedances of Z ₀₁ and Z ₀₂ , each having a quarter wavelength. / (Z ₀₁ ² / Η) = η (ε _r1 / ε _r2 ) = ε _r · η. Where Z ₀₁ = η / RT (ε _r1 ): characteristic impedance of the outer dielectric medium Z ₀₂ = η / RT (ε _r2 ) = about η: characteristic impedance of the inner dielectric medium η = 120 π: of the free space Wave impedance

The free space impedance is increased by ε _r times, and eventually the radiative conductance G of the MSA 4 according to the present embodiment configuration is increased by ε _r times when the dielectric layer 7 is not laminated. Therefore, the Q value of the MSA radiating element is reduced at that rate, and broadband radiation characteristics can be obtained.

In the present embodiment shown in FIG. 1, the dielectric layers 7 and 7'are in close contact with the MSA radiating element 4, but there is a high foaming ratio between the dielectric layer 7 and the MSA radiating element 4. A similar effect can be obtained by interposing a low dielectric constant material or by arranging a half effective wavelength interval.

In this case, the dimension of the planar antenna in the thickness direction is slightly increased, but the strong induction electromagnetic field in the vicinity of the radiating element 4 does not act directly on the dielectric layer 7, so that the radiating element 4
The advantage of minimizing the change in the resonance frequency and the increase in energy stored in the radiating element 4 are obtained.

Further, in the present embodiment, the dielectric layers 7 having a quarter effective wavelength are used in two layers. However, the dielectric layers 7 are used in multiple layers, similar to a general multi-stage impedance conversion technique of a microwave circuit. The band can be further widened by a stepwise conversion method. In this case, it is particularly effective to apply a combination of a ceramic material having a high relative dielectric constant and a resin dielectric material having a medium relative dielectric constant. FIG. 2 is a sectional view showing the structure of a coplanar circularly polarized planar antenna having a plurality of radiating elements.

In the planar antenna of the embodiment shown in FIG. 2, the MSA radiating elements 8 and 9 arranged on the ground conductor 1 with the insulating substrate dielectric 2 being spaced apart are excited by the microstrip feed line 10. The spatial impedance conversion dielectric layers 7 and 7 ′ are arranged so as to cover the MSA radiating elements 8 and 9 and the microstrip feed line 10. In this case, the working effect of the dielectric layers 7 and 7'is the same as that of the planar antenna shown in the embodiment in FIG. FIG. 3 is a plan view showing an arrangement configuration of MSA radiating elements in the coplanar circularly polarized planar antenna.

The feeding radiating element section 11 of this planar antenna
Is the microstrip antenna 1 on the same plane on one side which is separated by the ground conductor 1 and the substrate dielectric 2.
2, 13, 14, and 15 and the branch feeder line 16.

Each radiating element 12 at the end of the branch feed line 16,
The branch circuits 17 and 18 for 13, 14, and 15 are two-branch circuits with a half-wavelength folded line, and a method of exciting a pair of circularly polarized elements 180 degrees rotated and arranged with good symmetry (Japanese Patent Application No. -97711 "Flat Antenna", Japanese Patent Fair 3
-297207) has been adopted.

The form of the MSA radiating element 13 is a so-called single-point feeding circularly polarized wave generation type patch, and a pair of notch segments 19 and 20 are provided to make the resonance frequencies of the modes orthogonal to each other different from each other by 90 degrees. It is configured to excite with a phase difference of.

In this case, each MSA radiating element 12, 13,
Power is supplied to 14 and 15 from the outer peripheral portion of the patch, but the radiation conductance G can be appropriately increased by the action of the dielectric layer 7, and at the same time the Q of the planar antenna is lowered,
The matching property with the microstrip feed line 10 is improved, and both the circular polarization characteristics and the matching property can be broadened in bandwidth.

FIG. 4 is a cross-sectional view showing the structure of the feed line portion dielectric layer modification type planar antenna. The overall structure is substantially the same as that of the above embodiment, but the impedance conversion dielectric layer 7 is used.
By deforming, the apparent spatial impedance is increased on the radiating elements 8 and 9 to increase the radiated power, and the spatial impedance is decreased on the feed line 10 to suppress the radiation loss. In this case, the dielectric cover 21 forms a composite dielectric layer together with the dielectric layers 7 and 7 ', and the total thickness of the composite dielectric layer is set to a quarter effective wavelength.

The upper portion of the feed line 10 in this planar antenna may have a structure in which a part of the dielectric layer is removed. As a result, the free space impedance seen from the feed line 10 becomes a low impedance, and unnecessary radiation is suppressed, and the efficiency and performance of the planar antenna are improved.

As in the embodiment shown in FIG. 4,
The material of the outer dielectric cover 21 is hard for internal protection,
If the inner dielectric layer 7'is made soft, each radiating element 8, 9
Adhesion with and is improved, and the characteristics are stabilized. Figure 5
FIG. 3 is a cross-sectional view showing a configuration of a triplate feed type planar antenna by slot electromagnetic coupling.

The lower ground conductor 1 and the aperture radiating element 24,
The grounding conductor 23 provided with 25 and the exciting dielectrics 8 and 9 are arranged so as to sandwich the insulating dielectrics 2 and 22, and the strip feeding lines 10 and 10 'excite these to form a triplate feed type planar antenna. Composed.

The functions of the dielectric layers 7 and 7'and the dielectric cover 21 are the same as those in the above-mentioned respective embodiments, so that the radiation characteristics of the aperture radiating elements 24 and 25 are broadened. In this case, the excitation patches (radiating elements) 8 and 9 and the feed lines 10 and 10 'can be formed on the same film substrate. FIG. 6 is a sectional view showing the configuration of a planar antenna of the waveguide feeding slot radiating element type.

In this planar antenna, slot radiating elements 27, 28, 29 are provided on the upper surface of the waveguide 26, and the slot radiating elements 27, 28, 29 are excited by the traveling wave propagating in the waveguide 26. It

The dielectric layers 7 and 7 ′ having a thickness of 1/4 effective wavelength and the dielectric cover 21 facilitate the radiation of the slot radiating elements 27, 28 and 29. As a result, the waveguide 26 It is easy to combine with and the band can be widened.

Even when a radial line waveguide is used instead of the waveguide 26 as the feed line of the planar antenna of the embodiment shown in FIG. 6, the same effect as described above can be obtained.

Therefore, according to the plane antenna having the above-mentioned structure, the radiation is provided by the simple structure in which the dielectric layers 7 and 7'having a quarter effective wavelength are laminated on the MSA radiating element 3 and laminated. The Q value of the element 3 becomes small, the band of the matching with the feed line 5 is widened, and in the case of the circular polarized radiation element,
Broadening of the axial ratio showing the circular polarization characteristic is achieved.

Further, in the case of the MSA (cross trip antenna) radiating elements 8 and 9, by providing a cutout portion in the dielectric layers 7 and 7'above the feeder line 10, unnecessary radiation from the feeder line 10 is suppressed. As a result, the radiation characteristics from the radiating elements 8 and 9 are selectively strengthened and the antenna efficiency is enhanced.

Therefore, the planar antennas of various configurations can be made to have a wide band and high performance, and for example, a wide band operation of about 10% or more required for operating as a transmitting / receiving antenna for mobile communication can be supported. Like

In each of the above embodiments, a plurality of impedance conversion dielectric layers 7 and 7'are laminated on the radiating element 3 or 8 and 9, but the radiating element 3 or 8 is used. Impedance conversion dielectric layer 7 having a thickness equal to a quarter effective wavelength of the electromagnetic waves propagated from 8 and 9.
If only one layer is provided, the input impedance of the space viewed from the radiating element 3 or 8 or 9 is lowered, and the antenna characteristic is increased in bandwidth.

[0049]

As described above, according to the present invention, there is provided at least one radiating element disposed above the ground conductor surface with a space and a power feeding circuit for exciting the radiating element. A plurality of impedance conversion dielectric layers are provided on the radiating element, and the thickness of the one dielectric layer is equal to the effective wavelength of a quarter of the electromagnetic wave propagated from the radiating element in the thickness direction. Since the input impedance of the space viewed from the radiating element is set to high impedance and the antenna characteristic is broadened, the radiation band of the radiating element can be broadened with a relatively simple and economical structure. It is possible to improve the matching between the radiating element and the feeder line.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an MSA single patch coaxial feed type planar antenna according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the configuration of a coplanar circularly polarized planar antenna having a plurality of radiating elements.

FIG. 3 is an MS of the coplanar circularly polarized planar antenna.
The top view which shows the arrangement structure of an A radiation element.

FIG. 4 is a cross-sectional view showing a configuration of a feed line portion dielectric layer modification type planar antenna.

FIG. 5 is a cross-sectional view showing a configuration of a triplate-type power feeding type planar antenna by slot electromagnetic coupling.

FIG. 6 is a cross-sectional view showing a configuration of a waveguide-fed slot radiating element type planar antenna.

[Explanation of symbols]

1, 23 ... Ground conductor (plate), 2, 22 ... Insulating dielectric,
3,8,9 ... MSA radiating element, 4 ... MSA (microstrip antenna), 5 ... feeding wire, 6 ... coaxial plug, 7 ...
High-dielectric-constant dielectric layer, 7 '... Low-dielectric-constant dielectric layer, 10 ... Microstrip feed line, 11 ... Feed radiating element part, 1
2, 13, 14, 15 ... Microstrip antenna,
16 ... Branch feeding line, 17, 18 ... Branch circuit, 19, 20
... Notch segment, 21 ... Dielectric cover, 24, 25
... Aperture radiating element, 26 ... Waveguide, 27, 28, 29 ... Slot radiating element.

Claims (5)

[Claims] 1. A planar antenna having at least one radiating element arranged above a ground conductor surface with a space and a feeding circuit for exciting the radiating element, wherein a quarter is provided on the radiating element. Input impedance of the space viewed from the radiating element by arranging multiple dielectric layers for impedance conversion with effective wavelength thickness, arranging a high dielectric constant dielectric layer on the outside and a low dielectric constant layer or air layer on the inside A planar antenna characterized by increasing the impedance of the antenna and amplifying the radiated power to widen the antenna characteristics. 2. The impedance-converting quarter-wavelength effective dielectric layer is composed of a composite dielectric layer composed of a plurality of dielectric layers, and the composite dielectric layer has a total effective thickness. 2. The planar antenna according to claim 1, wherein the effective electrical length is set to have an effective wavelength of 1/4. 3. The composite dielectric layer uses a hard dielectric material as an outer layer and a soft dielectric material as an inner layer,
The planar antenna according to claim 2, wherein a dielectric layer made of the soft dielectric material is disposed in close contact with the radiating element. 4. The power feeding circuit, wherein the plurality of dielectric layers are closely attached to the power feeding circuit portion, and a cutout portion is provided in the dielectric layer corresponding to the radiating element portion on the same plane as the power feeding circuit portion. 4. The planar antenna according to claim 1, 2 or 3, wherein the free space impedance with respect to is smaller than the free space impedance with respect to the radiating element, and unnecessary radiation from the feeding circuit is suppressed. 5. A planar antenna having at least one radiating element arranged above a ground conductor surface with a space and a feeding circuit for exciting the radiating element, wherein a further impedance conversion is provided on the radiating element. And a thickness of the one dielectric layer is set to be equal to a quarter effective wavelength of an electromagnetic wave propagating from the radiating element in the thickness direction, and the outside is seen from the radiating element. Planar antenna characterized by lowering the input impedance of the space and widening the antenna characteristics.