JPH0884018A - Electromagnetic coupling patch antenna - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an electromagnetically coupled patch antenna that can achieve miniaturization and wideband characteristics, and that maintains good electrical characteristics. [Structure] From the outside or inside on a dielectric substrate of thickness h ₂ having a circular antenna with an outer radius a _o and an inner radius a _i formed on a dielectric substrate of thickness h ₁ and a ground conductor plate. In a microstrip antenna that forms a microstrip line that is an inserted feed line and overlaps each other,
The thickness of the dielectric plate substrate forming the circular patch having a radius a _m (a _i <a _m ) from the center of the circular antenna is approximately equal to the thickness of the dielectric substrate of thickness h ₂ forming the microstrip line. , The thickness of other parts of the dielectric plate substrate is h ₁ > h
_An electromagnetically coupled patch antenna was constructed in _two stages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetically coupled patch antenna which is compact and has a wide band.

[0002]

2. Description of the Related Art Array antennas in the future are required to have various performances such as beam scanning, beam forming, and low side lobe. For this purpose, an active phased array antenna having an LNA (low noise amplifier), HPA (high power amplifier) and a phase shifter is required. In addition, demand for mobile objects such as aircraft and automobiles is also expected. For this reason, it is also required to construct an array antenna including a feeding circuit and the like in a small and thin form.

The miniaturization and thinning of the antenna can be dealt with by using a microstrip antenna, and a microstrip feed line can be used for constructing a feed circuit. it can. Furthermore, FIG.
1A is a top view and FIG. 11B is a cross-sectional view showing an antenna using proximity coupling, which is one of the electromagnetic coupling feed systems. Reference numeral 50 is a rectangular patch antenna, 51 is a microstrip line, 52 and 53 are dielectric substrates, and 54 is a ground conductor plate. Since this electromagnetically coupled feed microstrip antenna does not require electrical connection such as soldering, it can be easily manufactured and reduced in cost.

The bandwidth required for L-band mobile satellite communications, BS receiving antennas, etc. is 3% to 5%. With a normal microstrip antenna using a dielectric substrate having a dielectric constant of 2.6 and a thickness of 1.6 mm, a band of only about 1% can be obtained. Therefore, in order to widen the band, it is necessary to lower the dielectric constant of the dielectric substrate or increase the substrate thickness.

For example, let us consider an antenna and a feed line that can obtain a bandwidth of 5% by using the proximity coupling feed system as shown in FIG. Resonance frequency of 1.63 GHz
Then, the thickness h of the substrate is about 8 mm, and if a circular patch is used instead of the rectangular patch, the radius a _{o of the} circular antenna is about 3 mm.
It is 6.5 mm. Here, assuming that the microstrip line shown in FIG. 11 is h ₂ = 4 mm, which is half the thickness of the substrate, the width W of the microstrip line having a characteristic impedance of 50Ω is required to be 11 mm. Such a microstrip line having a width W = 11 mm formed on the substrate thickness h ₂ = 4 mm is a feeding line, and at the same time, unnecessary radio waves are radiated from this line, which deteriorates the characteristics of the antenna. The problem occurs.

On the other hand, if the thickness h _{2 of the} substrate is 0.8 mm, the width of the microstrip line becomes 2.2 mm, and the electromagnetic field is confined in the feed line, so that the above-mentioned unnecessary radiation does not occur. However, the substrate thickness h = 6.4 mm,
In the circular patch antenna with a radius a _o = 33 mm, which was h ₂ = 1.6 mm, FIG. 12 shows impedance characteristics when the most reflection loss is good. In this state, it operates as a microstrip line, but the circular patch antenna cannot be excited and there is a problem that the feed line and the circular patch antenna cannot be matched. Although attained the matching between the antenna and the feed line by inserting a transformer lambda _g / 4, since the input impedance of the antenna is 20Ω about than 6, the characteristic impedance of the transformer lambda _g / 4 is about 32Ω As a result, the line width becomes wider, which causes a problem of spatial arrangement of the feed line and a problem of generation of unnecessary radiation from the feed line.

When beam scanning is performed at a wide angle by the array antenna, it is necessary to set the element spacing to about half a wavelength.
Therefore, miniaturization of the device is important. Compared to the circular patch antenna element operating in the basic mode described above,
The area of the ring antenna operating in the same basic mode (when the ratio of the outer shape to the inner diameter is 2) can be reduced by about 60%.
However, in the case of widening the band, the problems described above similarly occur.

Further, in order to widen the band, it is necessary to increase the thickness of the dielectric substrate, but there is a problem that the weight of the entire antenna is significantly increased.

Further, if the thickness of the dielectric substrate is increased, surface waves propagating in the lateral direction of the substrate are generated, coupling between unnecessary elements and leakage / radiation of power are generated, and input impedance / radiation of the antenna is generated. -There is a problem that the gain characteristic deteriorates.

[0010]

As described above, in the case of widening the band in the conventional electromagnetically coupled patch antenna, the thickness of the dielectric substrate becomes thicker, resulting in an increase in the weight of the antenna. In addition, the generation of unnecessary radiation from the microstrip line causes a problem such as adversely affecting the electric characteristics of the antenna, and the problem that the patch antenna and the power supply line cannot be coupled and the antenna does not operate. there were. It is an object of the present invention to provide an electromagnetically coupled patch antenna that obtains good electrical characteristics while maintaining the miniaturization of antenna elements and wide band characteristics.

[0011]

In order to achieve the above object, a first invention of the present application is a ring antenna having an outer radius a _o and an inner radius a _i formed on a dielectric substrate having a thickness h _1. A microstrip line, which is a feed line inserted from the outside or the inside, is formed on a dielectric substrate having a thickness h ₂ and a ground conductor plate. Radius a _m (a
The thickness of the dielectric plate substrate forming the circular patch of _i <a _m ) is almost equal to the thickness of the dielectric substrate of thickness h ₂ forming the microstrip line, and the thickness of the dielectric plate substrate in other parts is It is an electromagnetically coupled patch antenna in which h ₁ > h ₂ .

According to a second invention of the present application, in the structure of the first invention, a step having a width W is provided at an arbitrary intermediate position between the outer radius a _o of the annular antenna and the inner radius a _i , The thickness of the dielectric plate substrate in that portion is almost equal to the thickness of the dielectric substrate of thickness h ₂ on which the microstrip line is formed, and the thickness of the other portions is h ₁ > h ₂ in a multistage electromagnetic coupling It is a patch antenna.

Further, a third invention of the present application is such that the annular antenna in the first and second inventions of the present application is a rectangular patch,
This is an electromagnetically coupled patch antenna in which a square patch, an elliptic patch, or the like is replaced with a ring shape.

[0014]

According to the first invention of the present application, the thickness of the dielectric plate substrate forming the annular patch having a radius a _m (a _i <a _m ) from the center of the annular antenna is the thickness of the microstrip line formed. approximately equal to the thickness of the dielectric substrate h ₂ is, since the dielectric thickness of the substrate of the other parts in the multi-stage configuration in which the h _1> h _2, to realize miniaturization and broadband performance, the feed line Ya It suppresses the generation of unwanted radiation and coupling that causes surface waves propagating laterally on the dielectric substrate, has good compatibility with the feed line, and does not affect the electrical characteristics of the antenna.

According to the second invention of the present application, in the configuration of the first invention of the present application, a step having a width W at an arbitrary intermediate position between the outer radius a _o of the annular antenna and the inner radius a _i. Is provided, and the thickness of the dielectric plate substrate at that portion is approximately equal to the thickness of the dielectric substrate having a thickness h ₂ on which the microstrip line is formed, and the thickness of the other portions is set to h ₁ > h ₂ in a multistage configuration. Therefore, it is possible to operate in the same manner as the first invention of the present application, and the manufacturing restrictions are further alleviated.

Further, even if the annular antenna is replaced with a ring shape such as a rectangular patch, a square patch, an elliptic patch as in the third invention of the present application, the same operation as in the first invention of the present application can be achieved. .

[0017]

The present invention will be described below based on an embodiment.

FIG. 1 shows a close-coupling ring patch antenna which is one of the structures of the electromagnetic coupling feeding system according to the embodiment of the present invention. Note that FIG. 1A is a top view and FIG. 1B is a cross-sectional view.

In FIG. 1, reference numerals 1, 5 and 6 denote dielectric substrates having predetermined thicknesses (h ₁ -h), (h-h ₂ ), h ₂ respectively.
Is a circular patch antenna composed of a multi-stage structure having an outer radius a _o made of a conductor plate and an inner radius a _i , 3 is a microstrip feed line, and 4 is a ground conductor. The operation of this antenna will be described below.

First, the characteristics of the close-coupling feed type annular patch antenna shown in FIG. 2 will be clarified. A dielectric plate substrate 6 having a dielectric constant of 2.6, on which the microstrip line 3 is formed.
Has a thickness h ₂ = 1.6 mm, and the thickness h ₁ = of the dielectric plate substrate 1 having a dielectric constant of 2.6 on which the circular patch antenna 2 is formed.
An annular patch antenna in which the length S of the microstrip line (zero at the center of the annular patch and (+) when it exceeds the center is (+)) is changed in the case of 1.6 mm and 4.8 mm. Figure 3 shows the resonance frequency and reflection loss of
Shown in As shown in FIG. 3, as the thickness h ₁ of the dielectric substrate provided with the ring patch antenna is increased, the resonance frequency of the ring patch antenna becomes higher, and the ring patch and the microstrip line which is the feed line are Turns out to be inconsistent. FIG. 4 shows the input impedance with the parameters at points (a) and (b) shown in FIG.

Next, the thickness h ₂ of the dielectric plate substrate on which the microstrip line is formed is 1.6 mm, and the thickness h ₁ of the dielectric plate substrate on which the annular patch antenna is formed is h ₁ .
In the thickness relationship of 8 mm, a dielectric of a thickness h ₂ having a circular antenna having an outer radius a _o and an inner radius a _i formed on the dielectric substrate 1 having a thickness h ₁ and a ground conductor plate 4 Body board 6
In the antenna configuration shown in FIG. 1 in which the microstrip line 3 which is the feed line inserted from the outside is formed and is superimposed on each other, in the antenna configuration shown in FIG.
The thickness (h ₁ −h) of the dielectric plate substrate forming the circular patch of _m (a _i <a _m ) is equal to the thickness of the dielectric substrate of thickness h ₂ forming the microstrip line, and other portions The multi-stage electromagnetically coupled patch antenna was constructed with the thickness of the dielectric plate substrate of ₁ as h ₁ .

The outer radius a _o of the circular patch antenna is set to 3
In a circular patch antenna having a diameter of 2.5 mm, an inner radius of a _i of 16.25 mm, and a stepped radius of a _m of 21.5 mm and 27 mm, the length S of the microstrip line, which is a feeding line, was changed. FIG. 5 shows the resonance frequency and reflection loss of the circular patch antenna in this case. As shown in FIG. 5, by providing multiple stages in the annular patch, it is impossible to match the feed line and the annular patch antenna as shown in FIG. 3 to the points (c) and (d). It can be seen that the match can be easily obtained. Furthermore, the radius a _m
21.5 mm, the resonance frequency is 1.4 GHz as shown in point (c), and the resonance frequency is about 1. It was 05 times higher. Therefore, it can be expected that the gain will be increased by about 0.4 dB.

Further, it is understood that the resonance frequency can be controlled by changing the radius a _m of the multi-step circular shape. Further, FIG. 6 shows the input impedance of the annular patch antenna having the parameters at points (c) and (d) in FIG.

From the above, unlike the resonance characteristics in the antenna configuration shown in FIG. 2, the antenna of the present invention is different from the feed line and λ.
It has been found that a good match can be made without using a _g / 4 transformer.

[0025] Figure 7, in FIG. 3 (a), (b) point and the circular patch radially a _m stepped to provided was of FIG. 5 (c), the resonance frequency fr and bandwidth at point (d) The relationship with BW is shown in a table.
From the table of FIG. 7, the resonance frequency becomes higher by providing the step than the resonance frequency and the bandwidth at the point (a) of FIG. 3, and the bandwidth BW is widened by about 50% or more. I understand.

Further, although the radius a _{o of the} circular patch is constant, the resonance frequency of the circular patch antenna is increased by adopting a multi-stage structure. It can be seen that, as shown in FIGS. 5 and 6, the gain is increased by about 0.4 dB.
Therefore, when arrayed, the number of elements required to obtain a predetermined gain can be reduced, and the array antenna as a whole can be downsized.

Further, in the antenna of the present invention, since the central portion of the dielectric substrate of the circular patch is removed, the weight of the entire antenna is reduced and the weight can be reduced.

Although the antenna shown in FIG. 1 has been described in the case where the dielectric constant is 2.6, when the dielectric constant of the dielectric plate substrate is low, the portion corresponding to the antenna portion is previously hollowed out from a foam material or the like, a metal press, or the like. Since the antenna element and the array antenna can be formed by placing the antenna element which is easily manufactured in 1., the manufacturing is easy and the cost can be reduced.

Although the microstrip line 3 is inserted from the outside to the inside of the circular patch antenna 2, the same effect can be obtained by providing the microstrip line from the center to the outside of the circular patch antenna.

Further, if the thickness of the dielectric substrate is increased in order to widen the band, surface waves propagating in the lateral direction of the dielectric substrate are generated, causing unnecessary radiation and coupling. When the antenna element having a step formed on the dielectric substrate is arrayed as in the present invention, the boundary condition of the mode in which the surface wave propagates changes, and the stepped portion prevents unnecessary surface waves from propagating. Therefore, the characteristics of the antenna are not deteriorated.

Modifications are shown in FIGS. 8 (a), 8 (b) and 8 (c). Other than the circular patch antenna, any shape such as a rectangle, a square, and an ellipse, and the combination of the inside and outside shapes may be freely selected. Further, as shown in the top view of FIG. 9A and the sectional view of FIG. 9B, the same effect can be obtained by providing a step at an arbitrary intermediate position of the ring patch antenna.
Further, as shown in FIGS. 10 (a), (b), and (c), the same effect can be obtained in an antenna having a shape in which a ground conductor is short-circuited at a radius a _i inside the annular antenna. . Also in this shape, the same effect can be obtained even if a step is provided at an arbitrary position.

[0032]

As described above, according to the present invention, the miniaturization and the wide band property are realized, the unnecessary radiation generated from the feeding line is suppressed, the matching with the feeding line is good, and the electric characteristics of the antenna are improved. Does not affect

Further, by providing a step on the antenna element, the resonance mode of the circular patch antenna changes, and even in a circular patch antenna having the same radius, the resonance frequency becomes high and the gain of the antenna is about 0.5 dB or more. improves. Therefore, when an array antenna is configured by using this element, the number of elements for obtaining the same gain is reduced, so that the size of the entire array antenna is reduced.

Further, since the thickness of the dielectric substrate in the stepped portion can be reduced, the weight of the entire antenna can be significantly reduced.

Further, when the thickness of the dielectric substrate is increased, surface waves propagating in the lateral direction of the substrate are generated, and unnecessary coupling between elements and leakage / radiation of power are generated, but a step is formed on the dielectric substrate. By providing, it is possible to suppress the propagation of this surface wave. Therefore, the characteristics of the antenna can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of an electromagnetically coupled patch antenna according to an embodiment of the present invention.

FIG. 2 is a diagram showing a structure of a conventional patch antenna used for explaining a difference in characteristics between an embodiment of the present invention and a conventional one.

FIG. 3 is a diagram showing respective characteristics of a resonance frequency and a reflection loss in the structure of FIG.

FIG. 4 is a diagram showing the input impedance with the parameters at each point shown in FIG.

FIG. 5 is a diagram showing each characteristic of the resonance frequency and the reflection loss when the length of the feed line is changed in the structure of the embodiment of the present invention.

6 is a diagram showing the input impedance with the parameters at each point shown in FIG.

FIG. 7 is a table showing a difference in characteristics between an embodiment of the present invention and a conventional one.

FIG. 8 is a diagram showing each modification of the patch shape as another embodiment of the present invention.

FIG. 9 is a view showing a modified example in which the position where the step is provided is changed as another embodiment of the present invention.

FIG. 10 is a view showing each modified example of an antenna having a shape in which a ground conductor is short-circuited as another embodiment of the present invention.

FIG. 11 is a diagram showing an example of a conventional patch antenna.

12 is a diagram showing a characteristic of reflection loss in the structure of FIG.

[Explanation of symbols]

 1, 5, 6 Dielectric substrate 2 Circular patch 3 Feed line 4 Ground conductor plate

Claims (2)

[Claims] 1. A thickness h ₁ of radius a _o of the dielectric substrate to form the outer shape, the ring antenna and the thickness h ₂ having a ground conductor plate dielectric substrate radius a _i of the inner form outer or Form a microstrip line, which is a feed line inserted from the inside,
In the microstrip antennas that are overlapped with each other, a radius a _m (a _i <
a _m ), the thickness of the dielectric plate substrate forming the circular patch is substantially equal to the thickness of the dielectric substrate of thickness h ₂ forming the microstrip line, and the thickness of the other dielectric plate substrate is h ₁ An electromagnetically coupled patch antenna having a multi-stage configuration with> h ₂ . 2. The electromagnetic coupling patch antenna according to claim 1, wherein a step having a width W is provided at an arbitrary intermediate position between the outer radius a _o of the annular antenna and the inner radius a _i . It is characterized in that the thickness of the dielectric plate substrate is substantially equal to the thickness of the dielectric substrate of thickness h ₂ on which the microstrip line is formed, and the thickness of the other portions is h ₁ > h ₂ Electromagnetic coupling patch antenna.